Showing papers on "Cardiac cycle published in 2015"

Congenital heart disease assessment with 4D flow MRI.

Abstract: With improvements in surgical and medical management, patients with congenital heart disease (CHD) are often living well into adulthood. MRI provides critical data for diagnosis and monitoring of these patients, yielding information on cardiac anatomy, blood flow, and cardiac function. Though historically these exams have been complex and lengthy, four-dimensional (4D) flow is emerging as a single fast technique for comprehensive assessment of CHD. The 4D flow consists of a volumetric time-resolved acquisition that is gated to the cardiac cycle, providing a time-varying vector field of blood flow as well as registered anatomic images. In this article, we provide an overview of MRI evaluation of congenital heart disease by means of example of three relatively common representative conditions: tetralogy of Fallot, aortic coarctation, and anomalous pulmonary venous drainage. Then 4D flow data acquisition, data correction, and postprocessing techniques are reviewed. We conclude with several examples that highlight the comprehensive nature of the evaluation of congenital heart disease with 4D flow.

Quantitative Analysis of Vortical Blood Flow in the Thoracic Aorta Using 4D Phase Contrast MRI

Abstract: INTRODUCTION: Phase contrast MRI allows for the examination of complex hemodynamics in the heart and adjacent great vessels. Vortex flow patterns seem to play an important role in certain vascular pathologies. We propose two- and three-dimensional metrics for the objective quantification of aortic vortex blood flow in 4D phase contrast MRI. MATERIALS AND METHODS: For two-dimensional vorticity assessment, a standardized set of 6 regions-of-interest (ROIs) was defined throughout the course of the aorta. For each ROI, a heatmap of time-resolved vorticity values [Formula: see text] was computed. Evolution of minimum, maximum, and average values as well as opposing rotational flow components were analyzed. For three-dimensional analysis, vortex core detection was implemented combining the predictor-corrector method with λ2 correction. Strength, elongation, and radial expansion of the detected vortex core were recorded over time. All methods were applied to 4D flow MRI datasets of 9 healthy subjects, 2 patients with mildly dilated aorta, and 1 patient with aortic aneurysm. RESULTS: Vorticity quantification in the 6 standardized ROIs enabled the description of physiological vortex flow in the healthy aorta. Helical flow developed early in the ascending aorta (absolute vorticity = 166.4±86.4 s-1 at 12% of cardiac cycle) followed by maximum values in mid-systole in the aortic arch (240.1±45.2 s-1 at 16%). Strength, elongation, and radial expansion of 3D vortex cores escalated in early systole, reaching a peak in mid systole (strength = 241.2±30.7 s-1 at 17%, elongation = 65.1±34.6 mm at 18%, expansion = 80.1±48.8 mm2 at 20%), before all three parameters similarly decreased to overall low values in diastole. Flow patterns were considerably altered in patient data: Vortex flow developed late in mid/end-systole close to the aortic bulb and no physiological helix was found in the aortic arch. CONCLUSIONS: We have introduced objective measures for quantification of vortical flow in 4D phase contrast MRI. Vortex blood flow in the thoracic aorta could be consistently described in all healthy volunteers. In patient data, pathologically altered vortex flow was observed.

High-frame rate four dimensional optoacoustic tomography enables visualization of cardiovascular dynamics and mouse heart perfusion

Abstract: Functional imaging of mouse models of cardiac health and disease provides a major contribution to our fundamental understanding of the mammalian heart. However, imaging murine hearts presents significant challenges due to their small size and rapid heart rate. Here we demonstrate the feasibility of high-frame-rate, noninvasive optoacoustic imaging of the murine heart. The temporal resolution of 50 three-dimensional frames per second provides functional information at important phases of the cardiac cycle without the use of gating or other motion-reduction methods. Differentiation of the blood oxygenation state in the heart chambers was enabled by exploiting the wavelength dependence of optoacoustic signals. Real-time volumetric tracking of blood perfusion in the cardiac chambers was also evaluated using indocyanine green. Taken together, the newly-discovered capacities offer a unique tool set for in-vivo structural and functional imaging of the whole heart with high spatio-temporal resolution in all three dimensions.

Dynamic Changes in Tricuspid Annular Diameter Measurement in Relation to the Echocardiographic View and Timing during the Cardiac Cycle

Abstract: Background Tricuspid annular (TA) size and function play important roles in planning the need for associated TA annuloplasty in patients undergoing cardiac surgery for left-sided heart valve diseases. However, TA diameter normative values and the extent of TA dynamic changes during cardiac cycle remain to be established. Methods This was a prospective, cross-sectional study of 219 healthy volunteers (mean age, 43 ± 15 years; 57% women), using conventional two-dimensional transthoracic echocardiographic (2DE) imaging to assess the variability of TA diameter measurement in relation to 2DE view and timing during cardiac cycle. TA diameter was obtained from apical right ventricular (RV)–focused four-chamber, parasternal long-axis RV inflow, and parasternal short-axis at aortic plane 2DE views at five time points during the cardiac cycle. Right atrial and RV volumes were measured using three-dimensional echocardiography. Results TA diameters differed significantly among the three 2DE views and changed significantly during the cardiac cycle in all views. Moreover, mean fractional shortening of TA diameter was 24 ± 6% in the four-chamber view, 20 ± 7% in the parasternal long-axis RV inflow view, and 29 ± 11% in the parasternal short-axis at aortic plane view. One multivariate linear regression analysis, age, gender, and right atrial and RV volumes were independently correlated with TA diameters and accounted for 55% of the variance of midsystolic TA diameter in the four-chamber view. Conclusions This study provides references values for TA diameters and dynamics using 2DE imaging. Age, gender, and right chamber sizes, as well as the 2DE view and time during the cardiac cycle, significantly influenced TA diameters in healthy individuals. These data may help better identify TA dilatation using 2DE imaging for surgical planning.

Does the aortic annulus undergo conformational change throughout the cardiac cycle? : A systematic review

Abstract: Accurate annular sizing in transcatheter aortic valve implantation (TAVI) planning is essential. It is now widely recognized that the annulus is an oval structure in most patients, but it remains unclear if the annulus undergoes change in size and shape during the cardiac cycle that may impact prosthesis size selection. Our aim was to assess whether the aortic annulus undergoes dynamic conformational change during the cardiac cycle and to evaluate possible implications for prosthesis size selection. We performed a systematic search in PubMed and Embase databases and reviewed all available literature on aortic annulus measurements in at least two cardiac phases. Twenty-nine articles published from 2001 to 2014 were included. In total, 2021 subjects with and without aortic stenosis were evaluated with a mean age ranging from 11 ± 3.6 to 84.9 ± 7.2 years. Two- and three-dimensional echocardiography was performed in six studies each, magnetic resonance imaging was used in one and computed tomography in 17 studies. In general, the aortic annulus was more circular in systole and predominantly oval in diastole. Whereas the annular long-axis diameter showed insignificant change throughout the cycle, the short-axis diameter, area, and perimeter were significantly larger in systole compared with diastole. Hence, the aortic annulus does undergo dynamic changes during the cardiac cycle. In patients with large conformational changes, diastolic compared with systolic measurements can result in undersizing TAVI prostheses. Due to the complex annular anatomy and dynamic change, three-dimensional assessment in multiple phases has utmost importance in TAVI planning to improve prosthesis sizing.

Left Ventricular Vortices as Observed by Vector Flow Mapping: Main Determinants and their Relation to Left Ventricular Filling

Abstract: Background Swirling flow, organized in vortices, contributes to adequate left ventricular function. In this study, we apply a novel echocardiographic flow-mapping technique, vector flow mapping (VFM), to evaluate the main characteristics of left ventricular vortices and its relation to filling parameters. Methods Forty-eight subjects underwent conventional transthoracic echocardiographic examination with additional intracardiac flow assessment with VFM using a Aloka Alpha-10 system and experimental VFM analysis software. To analyze vortex behavior, its rotation direction, duration, location inside the left ventricle, size, and intensity were assessed in apical long-axis view. Its relation to conventional left ventricular filling parameters was then analyzed. Results Two vortex components were consistently identified following each transmitral filling wave. The anterior component of these visualized vortices was analyzed, due to its higher significance in the cardiac cycle, following early filling (V1) and atrial contraction (V2). Differences were observed in several aspects of vortex behavior between V1 and V2, particularly in patients with normal left ventricular filling parameters. These differences may be related to varying roles of vortices in different periods of the cardiac cycle. Conclusions Vector flow mapping allowed visualization and measurement of several parameters defining vortex behavior inside the cardiac cycle. The differences observed in these parameters between vortices in different phases of the cardiac cycle may be related to their role in optimizing cardiac function.

Value of left atrial strain: a highly promising field of investigation

Abstract: The principal role of the left atrium (LA) is to modulate left ventricular filling and cardiovascular performance by functioning as (i) a reservoir for pulmonary venous return during ventricular systole, (ii) a conduit for pulmonary venous return during early ventricular diastole, and (iii) a booster pump that augments ventricular filling during late ventricular diastole. The interplay between these atrial functions and ventricular performance throughout the cardiac cycle is crucial in many pathophysiological conditions.1,2 However, in clinical practice, we do not really assess all of the components of LA function. In fact, quantification of LA function remains challenging. Calculating ejection fraction or atrial ejection force has occasionally been proposed as methods for quantifying LA function, but they are neither routinely used nor recommended in the literature.3 Standard recommendations in the literature propose using LA volume calculated from trans-thoracic 2D echocardiography orthogonal views.3,4 LA size correlates with both LA and left ventricular (LV) function and is a strong predictor of cardiovascular morbidity and death.5 The antero-posterior diameter, calculated with M-mode or 2D echocardiography, is no longer considered to adequately represent the true LA size. For these reasons, the ASE/EACVI joined paper3 …

Mitral Annular Dynamics in Mitral Annular Calcification: A Three-Dimensional Imaging Study.

Abstract: Background The mitral annulus displays complex conformational changes during the cardiac cycle that can now be quantified by three-dimensional echocardiography. Mitral annular calcification (MAC) is increasingly encountered, but its structural and dynamic consequences are largely unexplored. The objective of this study was to describe alterations in mitral annular dimensions and dynamics in patients with MAC. Methods Transthoracic three-dimensional echocardiography was performed in 43 subjects with MAC and 36 age- and sex-matched normal control subjects. Mitral annular dimensions were quantified, using dedicated software, at six time points (three diastolic, three systolic) during the cardiac cycle. Results In diastole, the calcified annulus was larger and flatter than normal, with increased anteroposterior diameter (29.4 ± 0.6 vs 27.8 ± 0.6 mm, P = .046), reduced height (2.8 ± 0.2 vs 3.6 ± 0.2 mm, P = .006), and decreased saddle shape (8.9 ± 0.6% vs 11.4 ± 0.6%, P = .005). In systole, patients with MAC had greater annular area at all time points ( P P P = .04) in control subjects but not in those with MAC ( P = NS). Valvular alterations were also noted; although mitral valve tent length decreased during systole in both groups, decreases were less in patients with MAC ( P P = .006 vs control subjects, but nonsignificant for patients with mild MAC). Conclusions Quantitative three-dimensional echocardiography provides new insights into the dynamic consequences of MAC. This imaging technique demonstrates that the mitral annulus is not made smaller by calcification. However, there is loss of annular contraction, particularly along the anteroposterior diameter, and loss of early systolic folding along the intercommissural diameter. Associated valvular alterations include smaller than usual declines in tenting during systole. These quantitative three-dimensional echocardiographic data provide new insights into the dynamic physiology of the calcified mitral annulus.

Electrical consequences of cardiac myocyte: fibroblast coupling.

Abstract: Gap junctions are channels which allow electrical signals to propagate through the heart from the sinoatrial node and through the atria, conduction system and onwards to the ventricles, and hence are essential for co-ordinated cardiac contraction. Twelve connexin (Cx) proteins make up one gap junction channel, of which there are three main subtypes in the heart; Cx40, Cx43 and Cx45. In the cardiac myocyte, gap junctions are present mainly at the intercalated discs between neighbouring myocytes, and assist in rapid electrical conduction throughout the ventricular myocardium. Fibroblasts provide the structural skeleton of the myocardium and fibroblast numbers significantly increase in heart disease. Fibroblasts also express connexins and this may facilitate heterocellular electrical coupling between myocytes and fibroblasts in the setting of cardiac disease. Interestingly, cardiac fibroblasts have been demonstrated to increase Cx43 expression in experimental models of myocardial infarction and functional gap junctions between myocytes and fibroblasts have been reported. Therefore, in the setting of heart disease enhanced cardiac myocyte: fibroblast coupling may influence the electrical activity of the myocyte and contribute to arrhythmias.

Cardiovascular magnetic resonance compatible physical model of the left ventricle for multi-modality characterization of wall motion and hemodynamics

Abstract: The development of clinically applicable fluid-structure interaction (FSI) models of the left heart is inherently challenging when using in vivo cardiovascular magnetic resonance (CMR) data for validation, due to the lack of a well-controlled system where detailed measurements of the ventricular wall motion and flow field are available a priori. The purpose of this study was to (a) develop a clinically relevant, CMR-compatible left heart physical model; and (b) compare the left ventricular (LV) volume reconstructions and hemodynamic data obtained using CMR to laboratory-based experimental modalities. The LV was constructed from optically clear flexible silicone rubber. The geometry was based off a healthy patient’s LV geometry during peak systole. The LV phantom was attached to a left heart simulator consisting of an aorta, atrium, and systemic resistance and compliance elements. Experiments were conducted for heart rate of 70 bpm. Wall motion measurements were obtained using high speed stereo-photogrammetry (SP) and cine-CMR, while flow field measurements were obtained using digital particle image velocimetry (DPIV) and phase-contrast magnetic resonance (PC-CMR). The model reproduced physiologically accurate hemodynamics (aortic pressure = 120/80 mmHg; cardiac output = 3.5 L/min). DPIV and PC-CMR results of the center plane flow within the ventricle matched, both qualitatively and quantitatively, with flow from the atrium into the LV having a velocity of about 1.15 m/s for both modalities. The normalized LV volume through the cardiac cycle computed from CMR data matched closely to that from SP. The mean difference between CMR and SP was 5.5 ± 3.7 %. The model presented here can thus be used for the purposes of: (a) acquiring CMR data for validation of FSI simulations, (b) determining accuracy of cine-CMR reconstruction methods, and (c) conducting investigations of the effects of altering anatomical variables on LV function under normal and disease conditions.

Moving toward automatic and standalone delineation of seismocardiogram signal

Abstract: The purpose of this research is to propose an algorithm that could accomplish automatic delineation of the seismocardiogram (SCG) signal without using a reference electrocardiogram R-wave. As a result, the SCG signal could be used, as a stand-alone solution for many cardiovascular medical applications such as hemorrhage detection, cardiac computed tomographic gating, cardiac resynchronization therapy, hemodynamics estimations and diastolic timed vibration. Multiple envelopes were derived from the seismocardiogram signal by using filtering and triple integration. The first envelope is referred as the heart rate envelope, which has the characteristics of having a period of exactly one cardiac cycle and its purpose is to replace the ECG R-wave as a reference point. Our dataset is based on the lower body negative pressure (LBNP) test that was conducted on 18 individuals, containing 21610 cardiac cycles. For 94% of the LBNP dataset, the aforementioned envelope estimated heart rate within 3 beats per minute. Three different peaks of the SCG signal are of our interest: isovolumic contraction (IM), aortic valve opening (AO) and aortic valve closure (AC). For each of these desired peaks of the SCG signal, a different envelope was designed in a manner that its peak is very close to IM, AO and AC, respectively. For the same lower body negative pressure data set, a mean difference of (9, 9, 6) and standard deviation of (8, 9, 9) millisecond between the peak of envelopes and IM, AO and AC is accomplished. This could be used as a good initial estimation of the annotation points.

A new algorithm for segmentation of cardiac quiescent phases and cardiac time intervals using seismocardiography

Abstract: Systolic time intervals (STI) have significant diagnostic values for a clinical assessment of the left ventricle in adults. This study was conducted to explore the feasibility of using seismocardiography (SCG) to measure the systolic timings of the cardiac cycle accurately. An algorithm was developed for the automatic localization of the cardiac events (e.g. the opening and closing moments of the aortic and mitral valves). Synchronously acquired SCG and electrocardiography (ECG) enabled an accurate beat to beat estimation of the electromechanical systole (QS2), pre-ejection period (PEP) index and left ventricular ejection time (LVET) index. The performance of the algorithm was evaluated on a healthy test group with no evidence of cardiovascular disease (CVD). STI values were corrected based on Weissler’s regression method in order to assess the correlation between the heart rate and STIs. One can see from the results that STIs correlate poorly with the heart rate (HR) on this test group. An algorithm was developed to visualize the quiescent phases of the cardiac cycle. A color map displaying the magnitude of SCG accelerations for multiple heartbeats visualizes the average cardiac motions and thereby helps to identify quiescent phases. High correlation between the heart rate and the duration of the cardiac quiescent phases was observed.

Wave intensity analysis and its application to the coronary circulation.

Abstract: Wave intensity analysis (WIA) is a technique developed from the field of gas dynamics that is now being applied to assess cardiovascular physiology. It allows quantification of the forces acting to alter flow and pressure within a fluid system, and as such it is highly insightful in ascribing cause to dynamic blood pressure or velocity changes. When co-incident waves arrive at the same spatial location they exert either counteracting or summative effects on flow and pressure. WIA however allows waves of different origins to be measured uninfluenced by other simultaneously arriving waves. It therefore has found particular applicability within the coronary circulation where both proximal (aortic) and distal (myocardial) ends of the coronary artery can markedly influence blood flow. Using these concepts, a repeating pattern of 6 waves has been consistently identified within the coronary arteries, 3 originating proximally and 3 distally. Each has been associated with a particular part of the cardiac cycle. The most clinically relevant wave to date is the backward decompression wave, which causes the marked increase in coronary flow velocity observed at the start of the diastole. It has been proposed that this wave is generated by the elastic re-expansion of the intra-myocardial blood vessels that are compressed during systolic contraction. Particularly by quantifying this wave, WIA has been used to provide mechanistic and prognostic insight into a number of conditions including aortic stenosis, left ventricular hypertrophy, coronary artery disease and heart failure. It has proven itself to be highly sensitive and as such a number of novel research directions are encouraged where further insights would be beneficial.

Normal mitral annulus dynamics and its relationships with left ventricular and left atrial function

Abstract: Mitral annulus (MA) geometry and dynamics are crucial for preserving normal mitral valve (MV) function. Static reference values for MA parameters have been reported, but the normal MA dynamics during the entire cardiac cycle remains controversial. MV full-volume datasets were obtained by three-dimensional transthoracic echocardiography from 50 healthy volunteers (18-74 years; 31 men) to assess MA changes in size and shape during entire cardiac cycle. Using simultaneous multiplanar review, projected MA area (MAA) and circumference (MAC), antero-posterior (AP) and anterolateral-posteromedial (ALPM) diameters, and sphericity index (SphI) were obtained at: mitral valve closure (MVC), mid- and end-systole (ES), early- (EDF) and late-diastolic filling, and end-diastole. MAA and AP diameter were the most "active" parameters, changing in all reference frames (p < 0.001). MAA and AP diameter started to contract before MVC (during the left atrial contraction), reaching their minimum at MVC. Maximum MAA occurred at ES, while maximum AP diameter and SphI occurred at EDF. MAA fractional shortening was 35 ± 10 %. AP diameter change was 25 ± 10 %. MAC, ALPM and SphI showed similar patterns during left ventricular (LV) systole, and remained unchanged during diastole. Fractional change was 35 ± 10 % for MAC, and 13 ± 8 % for ALPM diameter. Our study provides the normal dynamics of the MA during the entire cardiac cycle. It reveals "pre-systolic" contraction of the MA, related to left atrial (LA) contraction, and minimal MAA during early LV systole. Therefore, the normal MA dynamics relates to a "physiologic LA-LV coupling", and a complete MA contraction requires both and properly timed LA and LV systole.

Troubleshooting Implantable Cardioverter-Defibrillator Sensing Problems II

Abstract: Accurate atrial sensing during tachycardia is essential for reliable determination of atrial rate, which is a critical component of interval-based dual-chamber supraventricular tachycardia (SVT)–VT discrimination algorithms1 Thus, atrial sensing in dual-chamber implantable cardioverter-defibrillators (ICDs) must be reliable at fast ventricular rates, a technically challenging requirement Determining the atrial rate during rapidly conducted atrial flutter (AF) requires accurate sensing of low-amplitude signals (Figure I in the Data Supplement) The required high atrial sensitivity increases the risk of atrial oversensing, especially of far-field R waves Pacemakers rely on a long postventricular atrial blanking period (PVAB) to prevent oversensing of far-field R waves, but ICDs cannot: for a fixed PVAB, the blanked fraction of the cardiac cycle increases with the ventricular rate For example, a 100-ms PVAB blanks 10% of the cycle at a bradycardia pacing cycle length of 1000 ms, but 33% during rapidly conducted AF with ventricular cycle length of 300 ms PVABs longer than ≈80 ms produce clinically significant, functional atrial undersensing in rapidly conducted AF,2 and any PVAB may cause undersensing of alternate atrial electrograms in AF with 2:1 atrioventricular conduction The inherent trade-off between atrial oversensing and undersensing is problematic Both cause errors in dual-chamber SVT–VT discrimination algorithms2–6 In contemporary ICDs, ventricular electrogram morphology algorithms mitigate this problem but do not eliminate it ### Determinants of Far-Field R Waves #### General Considerations In the absence of atrial lead dislodgement, the amplitude of far-field R wave depends on 4 variables The first is the amplitude of the ventricular electrogram in ventricular myocardium Thus, there is a correlation between far-field R–wave oversensing and left ventricular hypertrophy7 The second is interelectrode spacing8 Closely spaced electrodes (11 mm) minimize far-field R waves in comparison with conventional 10-mm spacing, but they also reduce the amplitude of atrial electrograms during short-term follow-up9,10 and …

High-frequency dual mode pulsed wave Doppler imaging for monitoring the functional regeneration of adult zebrafish hearts

Abstract: Adult zebrafish is a well-known small animal model for studying heart regeneration. Although the regeneration of scars made by resecting the ventricular apex has been visualized with histological methods, there is no adequate imaging tool for tracking the functional recovery of the damaged heart. For this reason, high-frequency Doppler echocardiography using dual mode pulsed wave Doppler, which provides both tissue Doppler (TD) and Doppler flow in a same cardiac cycle, is developed with a 30 MHz high-frequency array ultrasound imaging system. Phantom studies show that the Doppler flow mode of the dual mode is capable of measuring the flow velocity from 0.1 to 15 cm s(-1) with high accuracy (p-value = 0.974 > 0.05). In the in vivo study of zebrafish, both TD and Doppler flow signals were simultaneously obtained from the zebrafish heart for the first time, and the synchronized valve motions with the blood flow signals were identified. In the longitudinal study on the zebrafish heart regeneration, the parameters for diagnosing the diastolic dysfunction, for example, E/Em < 10, E/A < 0.14 for wild-type zebrafish, were measured, and the type of diastolic dysfunction caused by the amputation was found to be similar to the restrictive filling. The diastolic function was fully recovered within four weeks post-amputation.

Ivabradine Improves Left Ventricular Function During Chronic Hypertension in Conscious Pigs

Abstract: During chronic hypertension, increases in heart rate (HR) or adrenergic stimulation are associated with maladaptive left ventricular responses as isovolumic contraction and relaxation durations failed to reduce, impeding filling. We, therefore, investigated the effects of acute selective HR reduction with ivabradine on left ventricular dysfunction during chronic hypertension. Accordingly, chronically instrumented pigs received angiotensin II infusion during 4 weeks to induce chronic hypertension. Left ventricular function was investigated while angiotensin II infusion was stopped. A single intravenous dose of ivabradine was administered at days 0 and 28. Dobutamine infusion was also performed. HR was increased at day 28 versus day 0. Paradoxically, both isovolumic contraction and relaxation times failed to reduce and remained unchanged (57±3 versus 58±3 ms and 74±3 versus 70±3 at day 28 versus day 0, respectively). At day 28, ivabradine significantly reduced HR by 27%. Concomitantly, abnormal ventricular responses were corrected because both isovolumic contraction and relaxation times were significantly reduced while filling time was improved. Similarly at day 28, maladaptive responses of isovolumic contraction and relaxation to dobutamine were no longer observed during HR reduction with ivabradine. Correction of HR reduction with pacing showed that non-HR–related mechanisms also participated to these beneficial effects. In this model of chronic hypertension and left ventricular hypertrophy, acute HR reduction with ivabradine corrects the maladaptive responses of cardiac cycle phases by restoring a normal profile for isovolumic contraction and relaxation both at rest and under adrenergic stimuli, ultimately favoring filling.

Right and Left Atrial Dissimilarities in Normal Subjects Explored by Speckle Tracking Echocardiography.

Abstract: Background Atrial function is an important contributor of ventricular function and has a prognostic role in various cardiovascular diseases. We tested the hypothesis that right and left atrial (RA & LA) function may not be equal despite their accommodating identical cardiac output. Methods Two-dimensional (2D) speckle tracking echocardiography was acquired from the apical four-chamber view in 100 normal subjects. Both RA/LA subendocardial borders were traced to obtain atrial volumes, strain (e) and strain rate (SR). Reservoir, conduit, and booster pump functions were evaluated. Consequently, eNeg (corresponding to pump function) and ePos (corresponding to conduit function) were gauged. The SR parameters (SRLateNeg, SRPos, and SREarlyNeg), corresponding respectively to atrial systole, inception of ventricular systole, and inception of ventricular diastole, were measured. Results Mean age was 39 ± 15 years with 50 men (50%). Volumetric indices revealed that reservoir (Filling Volume = 35.1 ± 10.4 mL for LA vs. 27.47 ± 11.93 mL for RA, expansion index = 52.18 ± 16.89% for LA vs. 45.03 ± 16.49% for RA and diastolic emptying index = 52.85 ± 16.85 for LA vs. 45.62 ± 16.5 for RA, P < 0.001) and conduit (passive emptying (%) of total emptying = 34.49 ± 10.4 for LA vs. 26.82 ± 11.98 for RA and passive emptying index = 52.63 ± 16.86 for LA vs. 45.39 ± 16.5 for RA, P < 0.001) functions were significantly higher in the LA compared to the RA. Nevertheless, deformation indices demonstrated an opposite pattern (SRpos = 1.88 ± 0.74 for RA vs. 1.56 ± 0.54 for LA, P = 0.03 and ePos = 59.56 ± 30.63 for RA vs. 45.94 ± 16.67 for LA, P < 0.001). Reservoir, conduit, and booster pump functions showed no statistical significance among both genders. Conclusions Evaluation of global and regional RA/LA function by speckle tracking echocardiography is feasible. The current report provides insights regarding dissimilarities between both atria in healthy individuals. The significance of these findings and their potential application will warrant further work.

Seismocardiography-Based Detection of Cardiac Quiescence

Abstract: Cardiac-computed tomography angiography (CTA) is a minimally invasive imaging technology for characterizing coronary arteries. A fundamental limitation of CTA imaging is cardiac movement, which can cause artifacts and reduce the quality of the obtained images. To mitigate this problem, current approaches involve gating the image based on the electrocardiogram (ECG) to predict the timing of quiescent periods of the cardiac cycle. This paper focuses on developing a foundation for using a mechanical alternative to the ECG for finding these quiescent periods: the seismocardiogram (SCG). SCG was used to determine beat-by-beat systolic and diastolic quiescent periods of the cardiac cycle for nine healthy subjects, and 11 subjects with various cardiovascular diseases. To reduce noise in the SCG, and quantify these quiescent periods, a Kalman filter was designed to extract the velocity of chest wall movement from the recorded SCG signals. The average systolic and diastolic quiescent periods were centered at 29% and 76% for the healthy subjects, and 33% and 79% for subjects with cardiovascular disease. Both inter and intrasubject variability in the quiescent phases were observed compared to ECG-predicted phases, suggesting that the ECG may be a suboptimal modality for predicting quiescence, and that the SCG provides complementary data to the ECG.

Alterations in time intervals of ductus venosus and atrioventricular flow velocity waveforms in growth-restricted fetuses.

Abstract: Objective To investigate time intervals of the ductus venosus (DV) flow velocity waveform (FVW) and those of the cardiac cycle that correspond with each DV-FVW component in fetuses with intrauterine growth restriction (IUGR) due to placental insufficiency. Methods Women with a pregnancy complicated by IUGR were recruited into the study, as was a normal control group. Time intervals for systolic (S) and diastolic (D) components were measured in DV-FVW as follows: SDV, from the nadir of the a-wave during atrial contraction to the nadir between the S-wave and D-wave; DDV, from the nadir between S-wave and D-wave to the nadir of the a-wave. Regarding cardiac cycles, the following variables were measured from ventricular inflow through the tricuspid valve (TV) and mitral valve (MV): STV and SMV, from the second peak of ventricular inflow caused by atrial contraction (A-wave) to the opening of the atrioventricular valve; DTV and DMV, from the opening of the atrioventricular valve to the peak of the A-wave. In the IUGR group, only the last examination performed within 1 week of delivery was used for analysis. All variables were analyzed statistically using Z-scores. Results Data were obtained from 249 normal fetuses and 26 fetuses with IUGR. Compared to normal fetuses, SDV showed a significant decrease (P < 0.001), while DDV showed a significant increase (P < 0.001) in the IUGR group. Regarding cardiac cycles, STV and SMV showed significant decreases (P = 0.014 and P < 0.001, respectively) and DTV and DMV showed significant increases (P = 0.008 and P = 0.002, respectively) in fetuses with IUGR. Conclusion Time-interval alterations of DV-FVW in growth-restricted fetuses reflect the hemodynamic events caused by placental insufficiency. Copyright © 2014 ISUOG. Published by John Wiley & Sons Ltd.

Observation of cardiogenic flow oscillations in healthy subjects with hyperpolarized 3He MRI.

Abstract: Recently, dynamic MRI of hyperpolarized (3)He during inhalation revealed an alternation of the image intensity between left and right lungs with a cardiac origin (Sun Y, Butler JP, Ferrigno M, Albert MS, Loring SH. Respir Physiol Neurobiol 185: 468-471, 2013). This effect is investigated further using dynamic and phase-contrast flow MRI with inhaled (3)He during slow inhalations (flow rate ∼100 ml/s) to elucidate airflow dynamics in the main lobes in six healthy subjects. The ventilation MR signal and gas inflow in the left lower lobe (LLL) of the lungs were found to oscillate clearly at the cardiac frequency in all subjects, whereas the MR signals in the other parts of the lungs had a similar oscillatory behavior but were smaller in magnitude and in anti-phase to the signal in the left lower lung. The airflow in the main bronchi showed periodic oscillations at the frequency of the cardiac cycle. In four of the subjects, backflows were observed for a short period of time of the cardiac cycle, demonstrating a pendelluft effect at the carina bifurcation between the left and right lungs. Additional (1)H structural MR images of the lung volume and synchronized ECG recording revealed that maximum inspiratory flow rates in the LLL of the lungs occurred during systole when the corresponding left lung volume increased, whereas the opposite effect was observed during diastole, with gas flow redirected to the other parts of the lung. In conclusion, cardiogenic flow oscillations have a significant effect on regional gas flow and distribution within the lungs.

Validation of high temporal resolution spiral phase velocity mapping of temporal patterns of left and right coronary artery blood flow against Doppler guidewire

Abstract: Temporal patterns of coronary blood flow velocity can provide important information on disease state and are currently assessed invasively using a Doppler guidewire. A non-invasive alternative would be beneficial as it would allow study of a wider patient population and serial scanning. A retrospectively-gated breath-hold spiral phase velocity mapping sequence (TR 19 ms) was developed at 3 Tesla. Velocity maps were acquired in 8 proximal right and 15 proximal left coronary arteries of 18 subjects who had previously had a Doppler guidewire study at the time of coronary angiography. Cardiovascular magnetic resonance (CMR) velocity-time curves were processed semi-automatically and compared with corresponding invasive Doppler data. When corrected for differences in heart rate between the two studies, CMR mean velocity through the cardiac cycle, peak systolic velocity (PSV) and peak diastolic velocity (PDV) were approximately 40 % of the peak Doppler values with a moderate - good linear relationship between the two techniques (R2: 0.57, 0.64 and 0.79 respectively). CMR values of PDV/PSV showed a strong linear relationship with Doppler values with a slope close to unity (0.89 and 0.90 for right and left arteries respectively). In individual vessels, plots of CMR velocities at all cardiac phases against corresponding Doppler velocities showed a consistent linear relationship between the two with high R2 values (mean +/−SD: 0.79 +/−.13). High temporal resolution breath-hold spiral phase velocity mapping underestimates absolute values of coronary flow velocity but allows accurate assessment of the temporal patterns of blood flow.

Fast CT-FFR Analysis Method for the Coronary Artery Based on 4D-CT Image Analysis and Structural and Fluid Analysis

Abstract: Non invasive fractional flow reserve derived from CT coronary angiography (CT-FFR) has to date been typically performed using the principles of computational fluid analysis in which a lumped parameter coronary vascular bed model is assigned to represent the impedance of the downstream coronary vascular networks absent in the computational domain for each coronary outlet. This approach may have a number of limitations. It may not account for the impact of the myocardial contraction and relaxation during the cardiac cycle, patient-specific boundary conditions for coronary artery outlets and vessel stiffness. We have developed a novel approach based on 4D-CT image tracking (registration) and structural and fluid analysis based on one dimensional mechanical model, to address these issues. In our approach, we analyzed the deformation variation of vessels and the volume variation of vessels to better define boundary conditions and stiffness of vessels. We focused on the blood flow and vessel deformation of coronary arteries and aorta near coronary arteries in the diastolic cardiac phase from 70% to 100 %. The blood flow variation of coronary arteries relates to the deformation of vessels, such as expansion and contraction of the cross-sectional area, during this period where resistance is stable, pressure loss is approximately proportional to flow. We used a statistical estimation method based on a hierarchical Bayes model to integrate 4D-CT measurements and structural and fluid analysis data. Under these analysis conditions, we performed structural and fluid analysis to determine pressure, flow rate and CT-FFR. Furthermore, the reduced-order model based on fluid analysis was studied in order to shorten the computational time for 4D-CT-FFR analysis. The consistency of this method has been verified by a comparison of 4D-CT-FFR analysis results derived from five clinical 4D-CT datasets with invasive measurements of FFR. Additionally, phantom experiments of flexible tubes with and without stenosis using pulsating pumps, flow sensors and pressure sensors were performed. Our results show that the proposed 4D-CT-FFR analysis method has the potential to accurately estimate the effect of coronary artery stenosis on blood flow.Copyright © 2015 by ASME

Does the right muscular atrioventricular valve in the avian heart perform two functions

Abstract: The right atrioventricular valve of adult birds is a muscular unicuspid structure and unlike the right atrioventricular valve in the adult mammalian heart. The aim of this study is to test the hypothesis that the avian muscular valve (MV) is a part of the cardiac wall during systole and contributes to the right ventricle pump function. Six adult hens Gallus gallus domesticus were examined with a focus on MV structure and function. The thickness of the right ventricle (RV) wall and MV were examined post-mortem. RV wall and MV end-systolic thickness were estimated echocardiographically. The frame-by-frame processing of RV images was applied for the analysis of MV and RV free wall motion. According to the post-mortem measurements, no significant difference in the thickness between RV free wall and MV (1.8±0.3 and 1.6±0.4 mm, respectively) was found. In the course of the entire cardiac cycle, MV demonstrated the excursion of 10.3±0.9 mm. To the end of RV systole, MV thickness was increased roughly by a factor of two (2.9±0.57 mm), and reached almost the same value (3.0±0.25 mm) in RV free wall. Based on the findings obtained, we concluded that the MV may play specific and non-specific roles in the avian heart. First, MV determines the blood flow separation between the right heart chambers. Second, MV performs contractility to support for RV pump function.

Method and computer system for processing a heart sensor output

Abstract: The disclosure relates to a method and system for processing a heart sensor output, wherein a blood flow and a simulated aortic blood pressure are derived from a sensed blood pressure using an arterial flow model and values for arterial flow parameters. The simulated aortic blood pressure is matched to a part of the sensed blood pressure in the cardiac cycle by manipulating at least one of the values for the arterial flow parameters of the arterial flow model.

How the vagus nerve produces beat-to-beat heart rate variability; experiments in rabbits to mimic in vivo vagal patterns.

Abstract: Background and aim Analysis of heart rate variability (HRV) has recently become the playing field of mathematicians and physicists, losing its relation to physiology and the clinic. To set the record straight, a set of animal experiments is presented here, which was designed to test how vagus nerve traffic might produce beat to beat (b-t-b) heart rate (HR) control, like the baroreflex will do in vivo. Methods The response of HR to vagus nerve stimulation was tested after bilateral vagotomy in rabbits under anesthesia. Three protocols were followed: 1. Single burst stimulation at varying moments in one cardiac cycle; 2. B-t-b stimulation in each cycle, coupled to the P-wave with variable delays; in addition, testing the effects of one increased or decreased burst; 3. Tetanic stimulation, shortly interrupted or increased at varying moments in the cardiac cycle. Results and conclusions Sensitivity of the sinoatrial node to the timing of vagal bursts in its cycle from protocol 1 explains most of the observations. A single burst would be most effective when applied in late repolarization or early diastole of the sinoatrial node's action potential. In b-t-b stimulation the longest cardiac cycles occur when bursts are timed just before the end of the 'sensitive period'. Later coming bursts have their (diminished) effect on the next cycle; critically timed bursts induce an unstable HR, alternating between long and short cycles. This ran in synchrony with the respirator, thus producing a large respiratory sinus arrhythmia, even though the vagus nerves had been cut. HR-response to vagal burst activity shows two components: a fast one which is phase-sensitive and a slow one that builds up with longer lasting activity and also disappears slowly. Tetanic stimulation results in prolonged, but variable cycle lengths which are difficult to change by short-lasting manipulation of impulse frequency, be it up or down. Relevance for patients Measurement of heart rate variability (HRV) and baroreflex sensitivity (BRS) have become clinical tools in the cardiology clinic and in hypertension research. This study shows how the underlying vagus nerve to heart rate physiology is responsible for moment-to-moment variability in these numbers at almost unchanged underlying physiology. Programmed stimulation of the vagus nerves in acute animals (rabbits) demonstrates that the optimal mode of fast, beat-to-beat heart rate control by these nerves is by means of bursts of impulses arriving in every heart beat at well-timed moments. In vivo this is how the baroreflex stabilizes blood pressure at the expense of HRV.

A multidimensional dynamic quantification tool for the mitral valve

Abstract: OBJECTIVES: The mitral valve (MV) is a complex three-dimensional (3D) intracardiac structure. 3D transthoracic and transoesophageal echocardiography are used to evaluate and describe the changes in the mitral valve apparatus due to degenerative or functional mitral regurgitation. These techniques are, however, not accurate enough to capture the dynamic changes during the cardiac cycle. We describe a novel multistage modelling (MSM) technique, using three-dimensional transoesophageal echocardiography (3D TOE), to visualize and quantify the MV during all the phases of the cardiac cycle. METHODS: Using 3D TOE, sets of images were obtained from 32 individuals who were undergoing surgery for other reasons and who did not have MV disease. These images were divided into six steps whereby every step represented one cardiac cycle. The image sets were then cropped and sliced at the level of MV, then imported and segmented by the open source software (3D Slicer) to create 3D mathematical models. The models were synchronized with patient’s ECGs and then reunited and exported as multiphase dynamic models. The models were analysed in two steps: (i) direct step-by-step visual inspections of the MV from various angles and (ii) direct measurements of anteroposterior, intercommissural, anterolateral–posteromedial diameters, anterolateral angles and anteroposterior angles in systole and diastole at different levels. RESULTS: The segmentation results in 32 × 6 high-quality cropped MV. The division of models into six steps allows quantification and tracking of MV movement. Reunion of the models leads to creation of a full real-time simulation of the MV during the cardiac cycle. Synchronization of the models with ECG enables accurate simulation. Measurements of the diameters showed: median intercommissural diameters were increased with 10% from mid-systole to mid-diastole [31.9 mm (28.9–34.9), 34.8 mm (31.2–38.2), respectively, P-value <0.001]. This was also observed for anteroposterior diameters [33.8 mm (29.8–35.2), 37.1 mm (31.8–38.5), respectively, P-value <0.001]. Anterolateral–posteromedial diameter did not change significantly in both phases [43.7 mm (36.3–48.9), 43.5 mm (35.5–47.5), respectively]. Intercommissural and anteroposterior diameters were approximately the same in systole [31.9 mm (28.9–34.9) and 32.5 mm (29.8–35.2)] and diastole [34.8 mm (31.2–38.2) and 35.2 mm (31.8–38.5)]. Measurements of anteroposteriorangle at the anterolateral junction showed that this angle was accentuated acutely in diastole rather in systole [115° (104–129), 126° (113–137), respectively, P-value <0.001]. It was the same when measuring the anterolateral angle [105° (97–113), 119° (106–130), respectively, P-value <0.001]. CONCLUSION: The novel MSM technique allows precise quantification of shape changes in MV, which may help in better understanding the normal MV physiology, facilitate the diagnosis of MV pathologies and lead to numerical simulation of MV flow and displacement. It can also help cardiac surgeons and cardiologists gain a better understanding of the MV and assist them in obtaining a reliable orientation in order to choose optimal treatment strategies and plan surgical interventions. The measurement of the new anterolateral angle allowed better quantification of mitral annulus angulation and could be considered as new parameter that may help in future development of a new generation of mitral rings.