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Showing papers on "Cardiac cycle published in 2008"


Journal ArticleDOI
TL;DR: LV myocardial contraction and relaxation were first impaired in the longitudinal direction among the 3 directions in subclinical patients with cardiovascular risk factors, however, LV pump function and LV filling were compensated by circumferential shortening at ventricular systole and 3 directional lengthenings at atrial systoles.
Abstract: Background Two-dimensional strain imaging allows rapid and accurate analysis of regional left ventricular (LV) systolic and diastolic mechanics in the longitudinal, radial, and circumferential directions. The aim of this study was to assess precisely the differences in early impairment of LV myocardial contraction and relaxation among the 3 directions in 70 patients with cardiovascular risk factors and preserved LV pump function. Methods The patients were classified into 2 groups according to the ratio of early diastolic to atrial systolic velocity (E/A) of transmitral flow: E/A ≥ 1 (n = 35, 57 ± 6.8 years) or E/A Results The mean peak systolic longitudinal strain and strain rate were lower, whereas the mean peak systolic circumferential strain and strain rate were greater in the E/A Conclusion LV myocardial contraction and relaxation were first impaired in the longitudinal direction among the 3 directions in subclinical patients with cardiovascular risk factors. However, LV pump function and LV filling were compensated by circumferential shortening at ventricular systole and 3 directional lengthenings at atrial systole, respectively.

220 citations


Journal ArticleDOI
TL;DR: This study establishes age- and sex-specific ECG-gated MDCT reference values for thoracic aortic diameters in healthy, normotensive, nonobese adults to identify aorta pathology by MDCT.

122 citations


Journal ArticleDOI
TL;DR: The severity of heart failure and its prognosis are more closely related to the degree of diastsolic filling abnormalities than the ejection fraction, which underscores the importance of understanding the mechanisms of diastolic abnormalities in heart failure.

118 citations


Journal ArticleDOI
TL;DR: High frame rate, full-view myocardial elastography with automated contour tracking could provide regional strain information of the LV throughout an entire cardiac cycle, and characterize normal as well as detect abnormalMyocardial function, such as an infarction.
Abstract: Myocardial elastography is a novel method for noninvasively assessing regional myocardial function, with the advantages of high resolution and high precision. The purpose in this paper was to isolate the left ventricle from other structures for better displacement and strain visualization. Using a high-resolution (30 MHz) ultrasound system and a retrospective electrocardiogram (ECG)-gating technique, an extremely high frame rate (up to 8 kHz) was previously shown achievable for full-view (12-mm times 12-mm) myocardial elastography in the murine left ventricle. In vivo experiments were performed in anesthetized normal and infarcted mice [one day after left anterior descending (LAD) coronary artery ligation]. Radio frequency (RF) signals of the left ventricle (LV) in the long-axis view and the associated ECG were simultaneously acquired, with the ECG allowing gating of the RF signals. Incremental axial displacement of the myocardium was estimated using a one-dimensional (1-D) cross-correlation function. The cumulative displacement and strain then were calculated from the incremental displacement. In this paper, after manual selection of 40-50 points along the endo-and epicardial borders in the first frame of the cine-loop, myocardial contour was automatically tracked across the entire LV throughout a full cardiac cycle, which correctly determined the region of interest (ROI) for better interpretation. The cine-loop of the cumulative displacement and strain in one cardiac cycle, in both the normal and infarcted cases, showed that motion and deformation in the infarcted myocardium were significantly reduced, and that the infarcted region underwent thinning, rather than thickening, during systole. High precision of the displacement estimation, due to high frequency (30 MHz) and high frame rate (up to 8 kHz) available with this system, allowed for automated tracking of a manually-initialized myocardial contour over an entire cardiac cycle. High frame rate, full-view myocardial elastography with automated contour tracking could provide regional strain information of the LV throughout an entire cardiac cycle, and characterize normal as well as detect abnormal myocardial function, such as an infarction. The method of automated contour tracking can further enhance the capability of the elastographic technique with minimal user intervention while providing accurate functional information for the detection of disease throughout the entire cardiac cycle.

91 citations


Journal ArticleDOI
TL;DR: Phase analysis has been developed to allow assessment of LV dyssynchrony by gated single photon emission computed tomography myocardial perfusion imaging and has shown promising results in clinical evaluations.

88 citations


Journal ArticleDOI
TL;DR: The data show that the cyclic deformations of pulsating embryonic heart tubes run other than originally thought, and there is evidence that heart tubes of elliptic cross‐section might pump blood with a higher mechanical efficiency than those of circular‐cross section.
Abstract: The embryonic heart tube consists of an outer myocardial tube, a middle layer of cardiac jelly, and an inner endocardial tube. It is said that tubular hearts pump the blood by peristaltoid contractions. The traditional concept of cardiac peristalsis sees the cyclic deformations of pulsating heart tubes as concentric narrowing and widening of tubes of circular cross-section. We have visualized the cross-sectional deformations of contracting embryonic hearts in chick embryos (HH-stages 9–17) using real-time high-resolution optical coherence tomography. Cardiac contractions are detected from HH-stage 10 onward. During the cardiac cycle, the myocardial tube undergoes concentric narrowing and widening while the endocardial tube undergoes eccentric narrowing and widening, having an elliptic cross-section at end-diastole and a slit-shaped cross-section at end-systole. The eccentric deformation of the endocardial tube is the consequence of an uneven distribution of the cardiac jelly. Our data show that the cyclic deformations of pulsating embryonic heart tubes run other than originally thought. There is evidence that heart tubes of elliptic cross-section might pump blood with a higher mechanical efficiency than those of circular-cross section. The uneven distribution of cardiac jelly seems to prefigure the future AV and cono-truncal endocardial cushions. Developmental Dynamics 237:953–961, 2008. © 2008 Wiley-Liss, Inc.

76 citations


Journal ArticleDOI
31 Jul 2008-Pain
TL;DR: Significant variations in the N2–P2 amplitudes occurred across the cardiac cycle, with smaller amplitudes midcycle, indicating that cortical processing of nociception was attenuated during systole compared to diastole, and support the hypothesis that arterial baroreceptors modulate the processing ofN2-P2 during each cardiac cycle.
Abstract: Evidence suggests that the arterial baroreceptors modulate pain. To examine whether cortical processing of nociception is modulated by natural variations in arterial baroreceptor stimulation during the cardiac cycle, peak-to-peak amplitudes of the N2-P2 pain-related potential and pain ratings were recorded in response to noxious laser stimulation at different times during the cardiac cycle in 10 healthy males. Significant variations in the N2-P2 amplitudes occurred across the cardiac cycle, with smaller amplitudes midcycle, indicating that cortical processing of nociception was attenuated during systole compared to diastole. Pain ratings did not vary across the cardiac cycle. These data support the hypothesis that arterial baroreceptors modulate the processing of nociception during each cardiac cycle.

63 citations


Patent
18 Jan 2008
TL;DR: In this article, the authors discuss systems, devices, and methods that measure an impedance and adjust an atrioventricular (AV) delay or other cardiac resynchronization therapy (CRT) parameter that synchronizes left and right ventricular contractions.
Abstract: This document discusses, among other things, systems, devices, and methods measure an impedance and, in response, adjust an atrioventricular (AV) delay or other cardiac resynchronization therapy (CRT) parameter that synchronizes left and right ventricular contractions. A first example uses parameterizes a first ventricular volume against a second ventricular volume during a cardiac cycle, using a loop area to create a synchronization fraction (SF). The CRT parameter is adjusted in closed-loop fashion to increase the SF. A second example measures a septal-freewall phase difference (PD), and adjusts a CRT parameter to decrease the PD. A third example measures a peak-to-peak volume or maximum rate of change in ventricular volume, and adjusts a CRT parameter to increase the peak-to-peak volume or maximum rate of change in the ventricular volume.

61 citations


Journal ArticleDOI
TL;DR: Systolic and diastolic slopes correlated significantly with distensibility values obtained by Reneman formula and exhibited a close inverse relationship with each subject’s age and systolic blood pressure, thereby showing the ability to reflect age- and pressure-dependent large artery stiffening within each cardiac cycle.
Abstract: Use of local arterial distensibility measurements by change in carotid artery diameter divided by pulse pressure has limitations because blood pressure is often taken in a vessel distant or at a time different from where and when change in diameter is taken. In 92 subjects (23 to 91 years of age), carotid artery diameter was continuously measured ecographically, whereas blood pressure was continuously measured simultaneously tonometrically on the contralateral artery, the 2 signals being synchronized via 2 EKGs. Within each cardiac cycle, there was a linear relationship between the changes in vessel diameter and the changes in blood pressure during either the protomesosystole or the diastole after the dicrotic notch. The diastolic slope was displaced upward and steeper than the systolic slope, the pressure-diameter loop showing a hysteresis. Both slopes showed a high reproducibility when data were averaged over a several-second period. There were small differences between consecutive cardiac cycles, suggesting that modulation of arterial mechanical response to continuous changes in intravascular pressure may undergo physiological variations. In the 92 subjects, systolic and diastolic slopes correlated significantly with distensibility values obtained by Reneman formula and exhibited a close inverse relationship with each subject's age and systolic blood pressure, thereby showing the ability to reflect age- and pressure-dependent large artery stiffening. This method may allow precise assessment of man's arterial mechanical properties within each cardiac cycle. This highly dynamic assessment may help to collect information on properties of normal and altered large elastic arteries and the mechanisms involved in disease.

58 citations


Journal ArticleDOI
TL;DR: Blood flow structure and flow dynamics during ventricular systole were investigated in 10 normal volunteers and macroscopic and microscopic asynchrony in the myocardial contraction and extension appeared systematically in the local part of the ventricular wall, which was helpful for making the flowructure and for performing the smooth pump function.

56 citations


Journal ArticleDOI
TL;DR: The results suggest that a pattern of subendocardial hypoperfusion at systole and normal perfusion at diastole characterizes ischemic myocardium.
Abstract: OBJECTIVE. Assessment of hemodynamic changes in ischemic cardiac segments at rest using CT has yet to be performed. We hypothesized that variations in subendocardial perfusion during the cardiac cycle might be related to the appearances of ischemia. The purpose of this study was to investigate myocardial perfusion in ischemic segments using contrast-enhanced 64-MDCT.SUBJECTS AND METHODS. We performed cardiac MDCT at rest and stress/rest 201Tl myocardial perfusion scintigraphy (MPS) in 34 patients with suspected coronary artery disease. We reconstructed 2D long- and short-axis cardiac images in diastolic and systolic phases using raw data from coronary CT angiography. The attenuation value (in Hounsfield units) in the myocardium was used as an estimate of myocardial perfusion. We measured the subendocardial intensity of 17 segments according to the American Heart Association classification. Systolic perfusion or diastolic perfusion was calculated by dividing the subendocardial intensity at systole or diast...

Journal ArticleDOI
01 Jun 2008-Heart
TL;DR: Today’s invasive cardiologist views disturbances in coronary flow from narrowing of epicardial arteries, as seen in a coronary arteriogram, as not sufficient to explain angina, particularly in older women.
Abstract: Today’s invasive cardiologist views disturbances in coronary flow from narrowing of epicardial arteries, as seen in a coronary arteriogram. Impairment in coronary flow is attributed to narrowing of the arteries, and relief sought through angioplasty or bypass surgery.1 This is not sufficient to explain angina, particularly in older women, nor the medical approaches that can be directed at its relief.2 Blood flow to the heart is different from blood flow to other parts of the body in that rhythmic contraction of the left ventricle throttles blood vessels during cardiac contraction; in consequence, blood can only enter the left ventricular (LV) arteries during cardiac diastole. This is readily seen in left anterior descending coronary flow tracings as originally recorded by Gregg et al in conscious dogs with implanted flow meters,3 but can now be recorded in humans non-invasively with ultrasound.4 Such tracings do show some forward blood flow in systole, but this can be accounted for by systolic distension of the epicardial coronary arteries5; essentially there is no systolic flow into the LV myocardium. Hence one needs to consider factors other than coronary narrowing; these include the duration of diastole6 and the pressure gradient across the coronary bed.7 Arterial stiffening can affect both of these, and can readily explain angina even in the absence of coronary narrowing.5–9 Cardiologists are apt to explain such syndromes as due to “microvascular …

Journal ArticleDOI
TL;DR: In vivo cardiac MRE is a noninvasive method for measuring pressure-related heart function determined by shear modulus variations in the LV wall and is potentially useful for assessing pathologies associated with increased myocardial stiffness such as diastolic dysfunction.
Abstract: Objectives: To develop cardiac magnetic resonance elastography (MRE) for noninvasively measuring left ventricular (LV) pressure-volume (P-V) work. Material and Methods: The anterior chest wall of 8 healthy volunteers was vibrated by 24.3-Hz acoustic waves for stimulating oscillating shear deformation in myocardium and adjacent blood. The induced motion was recorded by an electrocardiogram-gated, vibration-synchronized and segmented gradient-recalled echo MRE sequence acquiring 360 phase-contrast wave images with a temporal resolution of 5.16 milliseconds in the short-axis view during controlled breathing. Relative changes in wave amplitudes served as a measure of LV pressure variation during the cardiac cycle. MRE pressure data were combined with LV volumes obtained from segmentation of 3D cine-steady-state free precession data sets. Results: Shear wave amplitudes decreased from diastole to systole, which reflects the dynamics of myocardial shear modulus variations during the cardiac cycle. Assuming spherical shear stress, a linear relationship between myocardial stiffness and LV pressure was derived. The MRE-measured pressure was plotted as a function of LV volumes. Characteristic P-V cycles displayed an isovolumetric increase in pressure during early systole, whereas less pronounced volume conservation was observed in early diastole. Mean cardiac P-V work in all volunteers was 0.85 ± 0.11 J. Conclusion: In vivo cardiac MRE is a noninvasive method for measuring pressure-related heart function determined by shear modulus variations in the LV wall. This is the first noninvasive mechanical test of cardiac work in the human heart and is potentially useful for assessing pathologies associated with increased myocardial stiffness such as diastolic dysfunction.

Journal ArticleDOI
TL;DR: Cardiac MDCT provides an excellent imaging method for illustrating cardiac valve disease and Radiologists should be aware of the various appearances of the common and most important cardiac valve diseases on cardiac MDCT.
Abstract: OBJECTIVE. Recent studies have established that cardiac MDCT generates high-quality images of the cardiac valves. Images are acquired during a single breath-hold (inspiration) after the injection of iodinated contrast material (5 mL/s) followed by a saline bolus chaser. Incremental data sets are then reconstructed throughout the R-R interval, and after transfer to a workstation, specialized software combines data sets sequentially to generate cine loops of the heart throughout the cardiac cycle. The purpose of this article is to describe the cardiac MDCT techniques allowing optimal cardiac valve depiction and to illustrate the MDCT appearances of the most important valve diseases.CONCLUSION. Cardiac MDCT provides an excellent imaging method for illustrating cardiac valve disease. Radiologists should be aware of the various appearances of the common and most important cardiac valve diseases on cardiac MDCT.

Journal ArticleDOI
TL;DR: The data in the early activated region of normal canine heart in vivo suggest that the volume change is greater than would be estimated from the known average transmural blood flow, which implies the existence of blood-filled spaces within the myocardium, which could communicate with the ventricular lumen.
Abstract: Although previous studies report a reduction in myocardial volume during systole, myocardial volume changes during the cardiac cycle have not been quantitatively analyzed with high spatiotemporal r...

Journal ArticleDOI
TL;DR: The shear stress on the artery wall, a major determinant of the buildup of plaque, is found to be higher for a debulked artery than for a plaque-narrowed artery, and the outcome is favorable in that the higher the wall shear, the lower the rate of plaque formation.

Journal ArticleDOI
TL;DR: LA volume changes significantly during the cardiac cycle, and substantial regional variation in LA motion exists, and standard measurements of LA volume significantly underestimate LA(max) compared to the gold standard measure of three-dimensional volumetrics.

Journal ArticleDOI
TL;DR: Patients with coarctation of the aorta have reduced proximal aortic wall velocities and strain and increased stiffness even after successful repair, which amplifies stress-induced hypertension and increases LV burden.
Abstract: Background Increased arterial stiffness may participate in the genesis of hypertension and increase of left ventricular (LV) mass after surgical correction of coarctation of the aorta. The purpose of the current study was to assess the aortic elastic properties using Doppler tissue imaging and strain rate imaging in patients after coarctoplasty. Methods Echocardiography with Doppler tissue/strain rate imaging capabilities was performed in 26 adult normotensive patients who had successful repair of coarctation of the aorta in infancy and in 24 control subjects. Transesophageal aortic transverse sections were imaged at the level of the proximal and distal segments to the repair site. Doppler tissue imaging wall velocities during systole (S w ), early relaxation (E w ), and atrial systole (A w ) and peak systolic strain (ps e) were measured in both groups. Transthoracic ascending aorta (AAo) measurements were also obtained. Results In the patients with coarctoplasty, S w velocities and ps e were significantly decreased in the proximal segments compared with control subjects. Both peak systolic blood pressure after exercise ( P P P P P Conclusions Patients with coarctation of the aorta have reduced proximal aortic wall velocities and strain and increased stiffness even after successful repair. This amplifies stress-induced hypertension and increases LV burden.

Journal ArticleDOI
TL;DR: It was shown that during diastole the intramyocardial capacitance vessels have two functional components, unstressed volume and ordinary capacitance, which indicates the increase in resistance by cardiac contraction.
Abstract: The phase opposition of velocity waveforms between coronary arteries (predominantly diastolic) and veins (systolic) is the most prominent characteristic of coronary hemodynamics. This unique arterial and venous flow patterns indicate the importance of intramyocardial capacitance vessels and variable resistance vessels during a cardiac cycle. It was shown that during diastole the intramyocardial capacitance vessels have two functional components, unstressed volume and ordinary capacitance. Unstressed volume is defined as the volume of blood in a vessel at zero transmural pressure. In vivo observation of systolic narrowing of arterioles in mid-wall and in subendocardium indicates the increase in resistance by cardiac contraction.

Journal ArticleDOI
TL;DR: Strain rate imaging is reproducible, yields readily obtained parameters that provide unique data about global and longitudinal segmental atrial contraction, and can quantify the atrial dysfunction in patients with HCM.
Abstract: This study applied tissue Doppler imaging and color tissue Doppler imaging to study atrial function changes in patients with hypertrophic cardiomyopathy (HCM). The profile of the segmental atrial velocities and the strain rate were determined and compared with those of normal matched control subjects. This study investigated 20 patients with HCM and 20 age-matched healthy control subjects. In a four-chamber apical view, tissue Doppler imaging was used to measure the lateral left and right atrial (LA and RA) and interatrial septal (IAS) wall systolic, early, and late diastolic velocities. Similarly, the atrial strain rate during ventricular systole (SRS) and the early (SRE) and late (SRA) diastolic phases in patients and control subjects were measured. The interventricular septal tissue Doppler-derived isovolumic relaxation time was calculated. Only the IAS annular and middle segments showed a significant reduction in the early diastolic velocity (mean, 4.01 ± 2.2 vs 8.7 ± 1.1, p = 0.001; 3.23 ± 2 vs 6.01 ± 1.9, p = 0.001, respectively) for the patients with HCM in comparison with the control subjects. Generally, the atrial strain rate was clearly reduced. The systolic strain rate (SRS) was significantly reduced in the LA wall in the annular (p = 0.007) and middle (p = 0.001) segments and in the IAS middle segment (p = 0.007). Similarly, there was a reduction of the early diastolic strain rate (SRE) in the LA annular (p = 0.001) and middle (p = 0.01) segments and in the IAS annular (p = 0.05) and middle (p = 0.001) segments, as well as in the RA annular segment (p = 0.02). The RA middle segments showed insignificant changes. Atrial function may be affected by HCM due to impairment of myocardial diastolic function. Strain rate imaging is reproducible, yields readily obtained parameters that provide unique data about global and longitudinal segmental atrial contraction, and can quantify the atrial dysfunction in patients with HCM.

Journal ArticleDOI
TL;DR: An abnormal shortening of diastolic time during exercise can restrict left ventricular filling to an extent that is sufficient to limitleft ventricular stroke volume reserve and to cause pulmonary congestion.

Journal ArticleDOI
TL;DR: There are no typical pulmonary blood flow patterns of cardiac origin in patients with Fontan circulation, except for slight late diastolic flow acceleration representing diastsolic inflow restriction.

Journal ArticleDOI
TL;DR: The region of the flow examined here has been identified as a likely location of hemolysis and thrombosis in tilting disk valves and may be helpful in minimizing the extent of blood damage through the combined efforts of experimental and computational fluid dynamics to improve mechanical heart valve designs.
Abstract: Hemolysis and thrombosis are among the most detrimental effects associated with mechanical heart valves The strength and structure of the flows generated by the closure of mechanical heart valves can be correlated with the extent of blood damage In this in vitro study, a tilting disk mechanical heart valve has been modified to measure the flow created within the valve housing during the closing phase This is the first study to focus on the region just upstream of the mitral valve occluder during this part of the cardiac cycle, where cavitation is known to occur and blood damage is most severe Closure of the tilting disk valve was studied in a "single shot" chamber driven by a pneumatic pump Laser Doppler velocimetry was used to measure all three velocity components over a 30 ms period encompassing the initial valve impact and rebound An acrylic window placed in the housing enabled us to make flow measurements as close as 200 microm away from the closed occluder Velocity profiles reveal the development of an atrial vortex on the major orifice side of the valve shed off the tip of the leaflet The vortex strength makes this region susceptible to cavitation Mean and maximum axial velocities as high as 7 ms and 20 ms were recorded, respectively At closure, peak wall shear rates of 80,000 s(-1) were calculated close to the valve tip The region of the flow examined here has been identified as a likely location of hemolysis and thrombosis in tilting disk valves The results of this first comprehensive study measuring the flow within the housing of a tilting disk valve may be helpful in minimizing the extent of blood damage through the combined efforts of experimental and computational fluid dynamics to improve mechanical heart valve designs

Journal ArticleDOI
TL;DR: The data indicate that successful diastolic gating results in a statistically significant reduction in the magnitude of cardiac motion artifact, with residual artifact attributed primarily to gross patient motion.
Abstract: The development and evaluation of a prototype cardiac gating system for double-shot dual-energy (DE) imaging is described. By acquiring both low- and high-kVp images during the resting phase of the cardiac cycle (diastole), heart misalignment between images can be reduced, thereby decreasing the magnitude of cardiac motion artifacts. For this initial implementation, a fingertip pulse oximeter was employed to measure the peripheral pulse waveform ('plethysmogram'), offering potential logistic, cost and workflow advantages compared to an electrocardiogram. A gating method was developed that accommodates temporal delays due to physiological pulse propagation, oximeter waveform processing and the imaging system (software, filter-wheel, anti-scatter Bucky-grid and flat-panel detector). Modeling the diastolic period allowed the calculation of an implemented delay, t(imp), required to trigger correctly during diastole at any patient heart rate (HR). The model suggests a triggering scheme characterized by two HR regimes, separated by a threshold, HR(thresh). For rates at or below HR(thresh), sufficient time exists to expose on the same heartbeat as the plethysmogram pulse [t(imp)(HR) = 0]. Above HR(thresh), a characteristic t(imp)(HR) delays exposure to the subsequent heartbeat, accounting for all fixed and variable system delays. Performance was evaluated in terms of accuracy and precision of diastole-trigger coincidence and quantitative evaluation of artifact severity in gated and ungated DE images. Initial implementation indicated 85% accuracy in diastole-trigger coincidence. Through the identification of an improved HR estimation method (modified temporal smoothing of the oximeter waveform), trigger accuracy of 100% could be achieved with improved precision. To quantify the effect of the gating system on DE image quality, human observer tests were conducted to measure the magnitude of cardiac artifact under conditions of successful and unsuccessful diastolic gating. Six observers independently measured the artifact in 111 patient DE images. The data indicate that successful diastolic gating results in a statistically significant reduction (p < 0.001) in the magnitude of cardiac motion artifact, with residual artifact attributed primarily to gross patient motion.

Patent
01 May 2008
TL;DR: In this article, a series of MR image frames are acquired that depict a subject's heart at successive cardiac phases, and delayed enhancement of infarcted myocardium is depicted in some of the image frames by administering a contrast agent prior to data acquisition.
Abstract: A series of MR image frames are acquired that depict a subject's heart at successive cardiac phases. Delayed enhancement of infarcted myocardium is depicted in some of the image frames by administering a contrast agent prior to data acquisition. Data acquisition is performed in a single breath hold by producing an RF inversion pulse followed by segments of SSFP pulse sequences during a succession of cardiac gated heart beats. The acquired MR image frames depict contrast between blood, viable myocardium and nonviable myocardium, and they depict left ventricle wall thickness and wall thickening throughout the cardiac cycle.

Patent
04 Jan 2008
TL;DR: In this paper, a method and system for determining systolic time intervals, by analysis of radio frequency (RF) scatter patterns in conjunction with Electrocardiogram (ECG) data, is provided.
Abstract: A method and system for determining systolic time intervals, by analysis of radio frequency (RF) scatter patterns in conjunction with Electrocardiogram (ECG) data, is provided. An RF emitter is placed on the cardiac patient. The emitter includes two or more transmitting antennas which emit RF radiation into the cardiac patient, resulting in an RF scatter pattern. An RF sensor receives the scattered RF signals. The RF emitted from the antennas will differ spatially with regard to the RF sensor, causing the RF scatter patterns to differ from one another. A signal processor analyzes these differences to identify inhomogeneous structures, and to identify aortic valve motion, including aortic valve opening and closure. An electrocardiogram identifies the onset of the cardiac cycle. Systolic intervals are determined using the onset of the cardiac cycle and the aortic valve motion. Cardiac contractility also is determined by correlation to systolic intervals. An acoustic sensor is used to verify the aortic valve closure.

Journal ArticleDOI
TL;DR: In this article, the effects of ventricular hypertrophy on systolic function in anesthetized rainbow trout were examined using Doppler echocardiography and electrocardiography.
Abstract: Using Doppler echocardiography and electrocardiography, we characterized cardiac hemodynamics, timing, and electromechanical function, and examined the effects of ventricular hypertrophy on systolic function in anesthetized rainbow trout. Atrial filling (D(SA)), ventricular filling (D(AV)), and ventricular ejection (D(VB)) accounted for 40-77, 13-27, and 22-41% of the cardiac cycle, respectively. Ventricular ejection occurred entirely during atrial filling and ended by the time the QT interval was 80% (SD=9%) completed. Sinoatrial (SA) flow was of longer duration (0.53+/-0.08 sec, mean+/-SD) and lower velocity (32+/-8 cm sec(-1)) than corresponding atrioventricular (AV, 0.19+/-0.02 sec; 87+/-8 cm sec(-1)) and ventriculobulbar (VB, 0.30+/-0.05 sec; 63+/-20 cm sec(-1)) values. Despite a wide range of heart masses, atrioventricular and VB valve dimensions were identical ( approximately 5.5 mm(2)). Ventricle mass (M(V)), but not relative ventricle mass (RVM), and cardiac cycle length were positively correlated (r(2)=0.57, P<0.001); thus, all time-dependent electrical/mechanical measures of cardiac function were significantly related to M(V), but not RVM. All rate-corrected (c) electromechanical event durations (except cD(SA)) and the systolic function index (cPEP (pre-ejection period)/D(VB)) were independent of RVM, suggesting the maintenance of cardiac functional capabilities across maturation stages (males) and different ventricle sizes (males and females). In summary, we define fundamental electrical and mechanical properties of the in vivo teleost myocardium under anesthesia, and report the maintenance of systolic function over a wide range of heart sizes for both sexes and maturation state of males. We also suggest that the short duration of ventricular emptying relative to the QT interval may provide a novel mechanism to adjust stroke volume and cardiac output in teleosts.

Proceedings ArticleDOI
01 Sep 2008
TL;DR: The use of gyroscopic sensors to quantify cardiac rotation was evaluated in animals to be a sensitive index of cardiac function and demonstrated the feasibility of assessing cardiac rotation and LV twist alterations by means of gyrotopic sensors.
Abstract: During the cardiac cycle, contraction of the helically oriented myocardial fibers results in torsion, a wringing motion as the cardiac apex rotates with respect to the base about the left ventricle (LV) long axis. We evaluated in animals the use of gyroscopic sensors to quantify cardiac rotation, which was demonstrated to be a sensitive index of cardiac function. Three gyroscopes were epicardially glued at different levels along the LV long axis (apex, middle, base) to assess LV twist dynamics: angular velocity (Ang V) and angle of cardiac rotation (angle) were measured and evaluated against hemodynamic measurements of LV pressure (LVP, LVdP/dt), at baseline and after acute ischemia induced by coronary ligation. Results demonstrated the feasibility of assessing cardiac rotation and LV twist alterations by means of gyroscopic sensors, especially at apical level: compared with baseline, acute ischemia caused a significant decrease of both Angle and the maximum value of Ang V (mean variation of -37plusmn6% and -21plusmn4%, respectively); a concomitant reduction of LVdP/dtMAX (-43plusmn4%) was observed.

Journal ArticleDOI
TL;DR: An overview of the commonest methods used for assessments of delays in events during the cardiac cycle and their implications for selecting patients for biventricular pacing are provided.
Abstract: Cardiac resynchronization therapy (CRT) has revolutionized not only the treatment of chronic heart failure but also how we assess left ventricular (LV) dysfunction on echo. Increasingly, it has become clear that identifying and quantifying delays in events during the cardiac cycle is an important assessment in LV dysfunction as it has prognostic implications for patients undergoing CRT. The delays in atrioventricular, right-to-left ventricular, and LV segmental contraction have been shown to be important components in cardiac performance, and this review provides an overview of the commonest methods used for these assessments and their implications for selecting patients for biventricular pacing.

Journal ArticleDOI
TL;DR: To develop a method for quantifying left ventricular internal flow as a measure of dyssynchrony using standard cine cardiac magnetic resonance (CMR) images.
Abstract: Purpose To develop a method for quantifying left ventricular (LV) internal flow as a measure of dyssynchrony using standard cine cardiac magnetic resonance (CMR) images. Materials and Methods CMR images were obtained from 10 healthy controls and 10 patients with dyssynchronous heart failure (class III/IV, LV ejection fraction 150 msec). The LV volume was reconstructed and divided into 16 regions. Internal flow was defined as the sum of the regional volume changes minus the global volume change during each time step in the cardiac cycle. Internal flow fraction (IFF) was defined as the total internal flow as a percentage of stroke volume during systole (IFFsystole), diastole (IFFdiastole), or the whole cycle (IFFwhole). Results IFFwhole was significantly increased in the patients (9.9 ± 5.0% vs. 1.5 ± 0.5% in the controls, P < 0.001). An IFFwhole threshold of 4% discriminated between patients and controls with 90% sensitivity and 100% specificity. IFFdiastole (2.3 ± 0.8%) was greater than IFFsystole (0.8 ± 0.5%) in the normal controls (P < 0.001) while the patients had similar IFFdiastole (7.8 ± 4.2%) and IFFsystole (12.0 ± 7.8%). Conclusion Left ventricular internal flow fraction can be quantified from standard CMR images. In this preliminary study, Left ventricular internal flow fraction discriminated patients with dyssynchronous heart failure from normal controls with 95% accuracy. J. Magn. Reson. Imaging 2008;28:375–381. © 2008 Wiley-Liss, Inc.