Showing papers on "Cardiac cycle published in 2004"

Impact of cardiac growth on Doppler tissue imaging velocities: a study in healthy children.

Abstract: Background Doppler tissue imaging (DTI) is a useful modality to quantitatively assess regional myocardial function. Studies attempting to establish reference values for DTI velocities in healthy children have been limited by small sample sizes and limited age distribution. In addition, the clinical effect of cardiac growth and other demographic and echocardiographic parameters on DTI velocities during childhood has not been adequately evaluated. Methods Pulsed wave DTI velocities were obtained in 325 healthy children at the lateral mitral annulus, interventricular septum, and lateral tricuspid annulus during early diastole, late diastole, and ventricular systole and were compared with demographic and echocardiographic study variables. Results In healthy children, parameters of cardiac growth, most notably left ventricular end-diastolic dimension, have the most significant correlation with the majority of DTI velocities. Age was also significantly correlated with most DTI velocities whereas sex, heart rate, and other echocardiographic parameters demonstrated minimal or no correlation. Conclusions This study establishes reference values for DTI velocities and demonstrates the important clinical effects of cardiac growth and age on DTI velocities in neonates and children.

Systolic ventricular filling.

Abstract: Summary The evidence of the ventricular myocardial band (VMB) has revealed unavoidable coherence and mutual coupling of form and function in the ventricular myocardium, making it possible to understand the principles governing electrical, mechanical and energetical events within the human heart From the earliest Erasistratus’ observations, principal mechanisms responsible for the ventricular filling have still remained obscured Contemporary experimental and clinical investigations unequivocally support the attitude that only powerful suction force, developed by the normal ventricles, would be able to produce an efficient filling of the ventricular cavities The true origin and the precise time frame for generating such force are still controversial Elastic recoil and muscular contraction were the most commonly mentioned, but yet, still not clearly explained mechanisms involved in the ventricular suction Classical concepts about timing of successive mechanical events during the cardiac cycle, also do not offer understandable insight into the mechanism of the ventricular filling The net result is the current state of insufficient knowledge of systolic and particularly diastolic function of normal and diseased heart Here we summarize experimental evidence and theoretical backgrounds, which could be useful in understanding the phenomenon of the ventricular filling Anatomy of the VMB, and recent proofs for its segmental electrical and mechanical activation, undoubtedly indicates that ventricular filling is the consequence of an active muscular contraction Contraction of the ascendent segment of the VMB, with simultaneous shortening and rectifying of its fibers, produces the paradoxical increase of the ventricular volume and lengthening of its long axis Specific spatial arrangement of the ascendent segment fibers, their interaction with adjacent descendent segment fibers, elastic elements and intracavitary blood volume (hemoskeleton), explain the physical principles involved in this action This contraction occurs during the last part of classical systole and the first part of diastole Therefore, the most important part of ventricular diastole (ie the rapid filling phase), in which it receives 70% of the stroke volume, belongs to the active muscular contraction of the ascendent segment We hope that these facts will give rise to new understanding of the principal mechanisms involved in normal and abnormal diastolic heart function

Timing of cardiac contraction in humans mapped by high-temporal-resolution MRI tagging: early onset and late peak of shortening in lateral wall

Abstract: Mechanical asynchrony is an important parameter in predicting the response to cardiac resynchronization therapy, but detailed knowledge of cardiac contraction timing in healthy persons is scarce. I...

Baseline echocardiographic values for adult male rats

Abstract: Background Because of safety, repeatability, and portability, clinical echocardiography is well established as a standard for cardiac anatomy, cardiac function, and hemodynamics. Similarly, application of echocardiography in commonly used rat experimental models would be worthwhile. The use of noninvasive ultrasound imaging in the rat is a potential replacement for more invasive terminal techniques. Although echocardiography has become commonly used in the rat, normal parameters for cardiac anatomy and function, and comparison with established human values, have not been reported. Methods A total of 44 Sprague-Dawley male rats had baseline echocardiography replicating a protocol for clinical echocardiography. Results Complete 2-dimensional echocardiography for cardiac anatomy and function was obtained in 44 rats. Hemodynamic parameters could be recorded in 85% of rats. The ejection fraction and fractional shortening values of the left ventricle were similar to those reported for healthy human beings. Pulsed Doppler velocities of atrial systole for mitral valve inflow, pulmonary vein reversal, and Doppler tissue of the lateral mitral valve annulus also had similar means as healthy human beings. The calculated left ventricular mass was at the same order of magnitude as a proportion of body weight of rat to man. All other observations in the clinical protocol were different from those reported in healthy human beings. Conclusion The use of echocardiography for assessment of cardiac anatomy, function, and hemodynamics can be consistently applied to the rat and replicates much of the information used routinely in human echocardiography.

Total heart volume variation throughout the cardiac cycle in humans.

Abstract: Variations in total heart volume (atria plus ventricles) during a cardiac cycle affect efficiency of cardiac pumping The goals of this study were to confirm the presence, extent, and contributors of total heart volume variation during the cardiac cycle in healthy volunteers with the use of MRI Eight healthy volunteers were examined by MRI at rest Changes in total cardiac volume throughout the cardiac cycle were calculated using the following methods: 1) planimetry derived from gradient-echo cine images and 2) flow-sensitive sequences to quantify flow in all vessels leading to and from the heart The maximum total heart volume diminished during systole by 82 +/- 08% (SEM, range 48-106%) measured by method 1 and 88 +/- 10% (SEM, range 56-118%) by method 2 with good agreement between the methods [difference according to Bland-Altman analysis -06% +/- 10% (SD), intraclass correlation coefficient = 0999] This decrease in volume is predominantly explained by variation at the midcardiac level at the widest diameter of the heart with a left-sided predominance In the short axis of the heart, the change of slice volume was proportional to the end-diastolic slice volume The present study has confirmed the presence of total heart volume variation that predominantly occurs in the region of atrioventricular plane movement and on the left side The total heart volume variation may relate to the efficiency of energy use by the heart to minimize displacement of surrounding tissue while accounting for the energy required to draw blood into the atria during ventricular systole

Enzyme replacement therapy with agalsidase β improves cardiac involvement in Fabry's disease

Abstract: Fabry's disease is an X-linked lysosomal storage disease caused by a deficiency of alpha-galactosidase that results in an accumulation of neutral glycosphingolipids throughout the body, including the cardiovascular system. Fabry cardiomyopathy, characterized by progressive severe concentric left ventricular (LV) hypertrophy, is very frequent and is the most important cause of death in affected patients. Enzyme replacement therapy (ERT) allows a specific treatment for this disease, however, there are very few data on the effectiveness of therapy on cardiac involvement. Nine patients with Fabry cardiac disease were studied on basal condition and after 6 and 12 months of treatment with algasidase beta (Fabrazyme). A complete clinical, electrocardiographic and echocardiographic evaluation was performed in all patients. Interpretable Doppler recordings of transmitral flow and pulmonary flow velocity curves were also acquired. At baseline, the patients with Fabry's disease had increased LV septum and posterior wall thickness, normal LV fractional shortening, LV ejection fraction, normal Doppler parameters of mitral inflow but a duration of pulmonary vein flow velocity wave exceeding that of the mitral wave at atrial systole. ERT did not affect heart rate and arterial pressure. LV internal diameters did not change, there was a slight but not significant decrease in the LV posterior wall thickening and a progressive decrease in the interventricular septum thickening (p < 0.025) and in LV mass (p < 0.001) The difference in duration between pulmonary vein flow velocity wave and mitral wave at atrial systole significantly decreased (p < 0.001). These results suggest that ERT in patients with Fabry cardiomyopathy is able to reduce the LV mass and ameliorate the LV stiffness.

Carotid flow rates and flow division at the bifurcation in healthy volunteers

Abstract: In nine healthy subjects, magnetic resonance imaging was used to measure blood flow waveforms in the common (CCA), internal (ICA) and external (ECA) carotid arteries. Useful data were acquired from 14 carotid arteries in total. Flow rates were determined from regions of interest placed over the arteries in CINE-phase contrast velocity encoded images. Use of a normalized cardiac cycle allowed the combination of flow waveforms from individuals. Time-averaged group mean flow rates were 6.16, 4.14 and 1.59 ml s(-1) for the CCA, ICA and ECA, respectively. Time-averaged values for the flow division ratios ICA/CCA, ECA/ICA and ECA/CCA were 0.70, 0.39 and 0.26, respectively. The data will be of use in future physiological studies and in computational modelling of carotid artery haemodynamics.

A rapid method to quantify left atrial contractile function: Doppler tissue imaging of the mitral annulus during atrial systole.

Abstract: Aims: Assess the value of peak atrial systolic mitral annular velocity ( A ann) measured by Doppler tissue echocardiography to quantify left atrial systolic function. Methods: We studied a total of 61 adults; 10 subjects without history of heart disease and 51 patients with a history of atrial fibrillation or undergoing evaluation for left ventricular systolic or diastolic dysfunction. A ann was obtained by averaging peak atrial systolic mitral annular velocities from the septal, lateral, anterior, and inferior annulus. Left atrial fractional area change (FAC) and fractional volume change (FVC) during atrial systole were calculated. The correlation between peak atrial systolic mitral annular velocity ( A ann) and left atrial systolic FAC and FVC was determined. Results: Mean FAC and FVC were 27±12 and 40±14%, respectively; mean A ann was 11.2 ± 3.2 cm/s. Linear regression analysis showed correlation between A ann and FAC ( r = 0.71; p <0.001) and between A ann and FVC ( r = 0.74; p <0.001). Conclusions: Peak systolic mitral annular velocity correlates well with left atrial systolic FAC and FVC, thus providing an easy means to assess left atrial systolic function.

Methods and apparatus for assisting cardiac resynchronization therapy

Abstract: A method for assisting the planning of an interventional biventricular pacing procedure includes segmenting an image dataset of a heart of a patient to extract a surface of a left ventricle (LV) and a LV myocardium of the patient's heart, utilizing the segmented image dataset to divide the LV into myocardial segments or into a plurality of short axis slices, and detecting wall motion of each short axis slice of phases of a cardiac cycle of the patient's heart with respect to a reference phase. The method also includes localizing a region most recently attaining maximum displacement and a region most recently attaining maximum velocity, and generating 2D or 3D renderings including renderings indicating at least one of time delays of contraction, a maximum displacement, or a maximum velocity.

Quantifying myocardial deformation throughout the cardiac cycle: a comparison of ultrasound strain rate, grey-scale M-mode and magnetic resonance imaging.

Abstract: Strain rate imaging (SRI) is a new ultrasound (US) approach to the quantification of regional myocardial deformation. It previously has been validated in vitro and in vivo against other imaging techniques. However, in all such studies, only peak strain values were compared, and the temporal evolution of the strain curve was not studied. Yet, it is the temporal evolution of the strain curves that contains the more important clinical information (e.g., asynchrony, viability, etc). Thus, the aim of this study was to compare the evolution of strain during the complete cardiac cycle as measured by US SRI, US grey-scale M-mode and magnetic resonance imaging (MRI). In 10 healthy volunteers and 20 patients with chronic ischaemic heart disease, radial deformation of the inferolateral segment of the left ventricle was measured by US SRI, US M-mode and MRI. The correspondence of the temporal characteristics of these strain curves were compared by defining an intraclass correlation coefficient (ICC). In healthy volunteers, an overall good agreement (mean ICC: 0.75 and 0.63 for systole and diastole) was found between the different methods. However, in patients with abnormal segmental deformation and low peak strain values, the agreement was less (mean ICC: 0.42 and 0.32), but remained within acceptable limits for clinical decision making. Myocardial deformation measurements using SRI correlated well with MRI and US M-mode measurements throughout the complete cardiac cycle.

Tissue Doppler gated (TDOG) dynamic three-dimensional ultrasound imaging of the fetal heart.

Abstract: Dynamic three-dimensional (3D) ultrasound imaging of the fetal heart is difficult due to the absence of an electrocardiogram (ECG) signal for synchronization between loops. In this study we introduce tissue Doppler gating (TDOG), a technique in which tissue Doppler data are used to calculate a gating signal. We have applied this cardiac gating method to dynamic 3D reconstructions of the heart of eight fetuses aged 20-24 weeks. The gating signal was derived from the amplitude and frequency contents of the tissue Doppler signal. We used this signal as a replacement for ECG in a 3D-volume reconstruction and visualization, utilizing techniques established in ECG-gated 3D echocardiography. The reliability of the TDOG signal for fetal cardiac cycle detection was experimentally investigated. Simultaneous recordings of tissue Doppler of the heart and continuous wave (CW) spectral Doppler of the umbilical artery (UA) were performed using two independent ultrasound systems, and the TDOG signal from one system was compared to the Doppler spectrum data from the other system. Each recording consisted of a two-dimensional (2D) sector scan, transabdominally and slowly tilted by the operator, covering the fetal heart over approximately 40 cardiac cycles. The total angle of the sweep was estimated by recording a separate loop through the center of the heart, in the elevation direction of the sweep.3D reconstruction and visualization were performed with the EchoPAC-3D software (GE Medical Systems). The 3D data were visualized by showing simultaneous cineloops of three 2D slices, as well as by volume projections running in cineloop. Synchronization of B-mode cineloops with the TDOG signal proved to be sufficiently accurate for reconstruction of high-quality dynamic 3D data. We show one example of a B-mode recording with a frame rate of 96 frames/s over 20 seconds. The reconstruction consists of 31 volumes, each with 49 tilted frames. With the fetal heart positioned 5-8 cm from the transducer, the sampling distances were approximately 0.15 mm in the beam direction, 0.33 degrees approximately 0.37 mm azimuth and 0.45 degrees approximately 0.51 mm elevation. From this single dataset we were able to generate a complete set of classical 2D views (such as four-chamber, three-vessel and short-axis views as well as those of the ascending aorta, aortic and ductal arches and inferior and superior venae cavae) with high image quality adequate for clinical use.

Sonometric study of the normal tricuspid valve annulus in sheep.

Abstract: Studies of the tricuspid valve have always lagged behind those of other cardiac valves because, when diseased, the valve's scant symptomatology and diffi- cult diagnosis have minimized its real frequency and importance. Recent advances in echocardiography have revealed a higher than expected incidence of tri- cuspid insufficiency, and less than perfect results of its surgical management. This is particularly significant in functional regurgitation where, as with the mitral valve, late recurrence of the insufficiency is frequent. These unsatisfactory results call for a reappraisal of surgical techniques that in the past might have been based on an incomplete knowledge of the normal and Background and aim of the study: Mitral valve dynamic changes during the cardiac cycle have been previously studied in sheep using sonomicrometry. The study aim was to analyze geometric changes of the normal tricuspid annulus in sheep using a simi- lar methodology. This is most likely the first tricus- pid valve study using high temporal resolution (200 Hz = 200 data points per second). Methods: Thirteen crystals were implanted in seven sheep along the annulus (n = 6), at the tips of papil- lary muscles (n = 3), at the free edge of the leaflets (n = 3), and at the apex of the left ventricle (n = 1). Recordings (10 s) of crystal distances were used to create a three-dimensional (3D) coordinate system based on the least-squares plane of the annulus, and maximum and minimum values were calculated for length, area, and position in xyz coordinates. Results: During the cardiac cycle, the tricuspid annu- lus area expanded 28.6 ± 3.6% with similar maximum expansions of each segment along the annulus: sep- tal (10.4 ± 1.2%), anterior (13.0 ± 1.5%), and posterior (14.0 ± 1.6%). The annulus was saddle-shaped, with a circumferential expansion from elliptical at mini- mum area to more circular at maximum area. The time delay to maximum leaflet area and maximum papillary area occurred 83 ± 13 ms and 279 ± 30 ms respectively after maximum annulus area. Conclusion: The tricuspid valve undergoes continual and complex geometric changes during the cardiac cycle. In addition, the annulus expands significantly due to similar increases in length of the septal and free wall segments. The annulus is not in a single plane, but is saddle-shaped. The expansion and con- traction of the tricuspid valve complex is stepwise, and sequential from base to apex.

Catherter for measuring an intraventricular pressure and method of using same

Abstract: A method for diagnosing a right ventricular dysfunction of a subject. The method includes measuring a right intraventricular pressure waveform in the subject over at least one cardiac cycle, extracting a ventricular parameter indicative of a right ventricular function from the measured right intraventricular pressure waveform, and establishing a diagnosis at least in part on a basis of the ventricular parameter.

Accurate and reproducible mitral valvular blood flow measurement with three-directional velocity-encoded magnetic resonance imaging.

Abstract: A new method for quantifying the transvalvular flow through the mitral valve (MV) based on three‐directional velocity‐encoded magnetic resonance imaging (MRI) is presented. For thirty time phases during one cardiac cycle, the three‐dimensional (3D) velocity vector field of the blood flow is reconstructed from the MRI measurement. Retrospectively, for each time phase, the MV‐plane is indicated manually in the velocity data and the flow through this plane is determined, representing the MV flow. Measurements are performed in 10 healthy volunteers. The new method is compared to the conventional, one‐directional velocity‐encoded MRI method for which an acquisition plane is positioned at the mitral valve at end‐systole and remains fixed during the acquisition. The flow measurements with the new method correlate very well with the flow measured in the aorta (rP = 0.92, p < 0.01), whereas the conventional method shows no statistically significant correlation (rP = 0.15, p = 0.68). The low differences between the...

The cardiac cycle time effect revisited: Temporal dynamics of the central-vagal modulation of heart rate in human reaction time tasks

Abstract: Lacey and Lacey (1974) suggested that during reaction time tasks higher brain centers dynamically adjust efferent vagal nerve pulses to the sino-atrial node of the heart, inducing phase-dependent heart rate changes. Since then, animal and human neuro-physiological results have provided evidence for this hypothesis. Higher subcortical and cortical brain centers may have reciprocal interactive pathways relating to autonomic control comparable to those at the level of peripheral autonomic changes and brain stem reflexes. In humans such central effects may be observed in the short latency vagal control of heart rate that has been studied mostly in reaction time (RT) tasks. RT task parameters modulate vagal pulses to the cardiac sino-atrial node (SAN), which in turn exerts a phase-dependent change in the ongoing cardiac interbeat interval. Simulations of human RT task effects in an animal model of heart rate change support this hypothesis. The current study examined evidence for vagal control of three human phasic heart rate responses in RT tasks. The evidence indicates that the initiation of an RT response triggers a reflexive shift from vagal activation to vagal inhibition. This shift is cardiac cycle phase dependent. Graded anticipatory cardiac deceleration during the warning interval of an RT task varies with task relevance and time uncertainty. This response may be part of a control process engaged in time keeping. Hence, temporal variables mediate the central-autonomic-vagal modulation of heart rate.

Non-invasive left ventricular volume determination

Abstract: A method of and a computer readable medium comprising a program for calculating total left ventricular (LV) volume during a cardiac cycle. The LV volume is estimated using only endocardial contours in a cardiac 3D image that was acquired at end diastole (ED), i.e. the moment at which the heart is fully relaxed. These contours are manually specified or (semi-)automatically derived. Based on these contours and on the pixel intensity in all other images, the LV volume is estimated based on intensity variations within the area enclosed by the contours (ED LV blood pool). These variations are proportional to the change in size of the ventricle. Hence ventricle volume and other derivable cardiac functionality parameters as well as the phase in the cardiac cycle are derived. The 3D image is previously to the method captured by means of a device for imaging inside parts of a mammal body, such as Magnetic Resonance (MR), Computer Tomography (CT), Nuclear Medicine (NM) or Ultrasound (US) devices.

Role of diastole in left ventricular function, I: Biochemical and biomechanical events.

Abstract: Left ventricular diastolic function plays an important role in cardiac physiology. Lusitropy, the ability of the cardiac myocytes to relax, is affected by both biochemical events within the myocyte and biomechanical events in the left ventricle. β-Adrenergic stimulation alters diastole by enhancing the phosphorylation of phospholamban, a substrate within the myocyte that increases the uptake of calcium ions into the sarcoplasmic reticulum, increasing the rate of relaxation. Troponin I, a regulatory protein involved in the coupling of excitation to contraction, is vital to maintaining the diastolic state; depletion of troponin I can produce diastolic dysfunction. Other biochemical events, such as defects in the voltage-sensitive release mechanism or in inositol triphosphate calcium release channels, have also been implicated in altering diastolic tone. Extracellular collagen determines myocardial stiffness; impaired glucose tolerance can induce an increase in collagen cross-linking and lead to higher end-diastolic pressures. The passive properties of the left ventricle are most accurately measured during the diastasis and atrial contraction phases of diastole. These phases of the cardiac cycle are the least affected by volume status, afterload, inherent viscoelasticity, and the inotropic state of the myocardium. Diastolic abnormalities can be conceptualized by using pressure-volume loops that illustrate myocardial work and both diastolic and systolic pressure-volume relationships. The pressure-volume model is an educational tool that can be used to demonstrate isolated changes in preload, afterload, inotropy, and lusitropy and their interaction. (American Journal of Critical Care. 2004;13:394-405)

A device and method to limit filling of the heart

Abstract: A device (20) used to treat heart disease by decreasing the size of a diseased heart, or to prevent further enlargement of a diseased heart. The device works by limiting the volume of blood entering the heart during each cardiac cycle. The device partitions blood within the ventricle of the heart, and protects the ventricle from excessive volume and pressure of blood. The device is placed within the interior of a heart, particularly within a ventricular cavity. The device is a hollow sac (24) with two openings (22), (30) which simulates the shape and size of the interior lining of a ventricle of a normal heart and limits filling of the heart beyond that volume. By limiting the amount of blood entering the ventricle, the ventricle is not subjected to the harmful effect of excessive volume and pressure of blood during diastole, the period of the cardiac cycle when the heart is at rest. This allows the ventricle to decrease in size, or to reverse remodel, and to recover lost function. In some applications, a second device may be simultaneously placed inside heart to take up excessive space between the heart and the primary device.

Atrial capture verification

Abstract: Methods and systems for classifying cardiac responses to pacing stimulation and/or preventing retrograde cardiac conduction are described. Following delivery of a pacing pulse to an atrium of the patient's heart during a cardiac cycle, the system senses in the atrium for a retrograde P-wave. The system classifies the atrial response to the pacing pulse based on detection of the retrograde P-wave. The system may also sense for an atrial evoked response and utilize the atrial evoked response in classifying the cardiac pacing response.

Electromechanical left ventricular resynchronisation by coronary artery bypass surgery

Abstract: Objective: In patients with coronary artery disease (CAD), the normal electromechanical response to dobutamine stress is deranged: QRS duration lengthens rather than shortens, left ventricular asynchrony develops, post-ejection shortening appears, and total isovolumic time (the time in the cardiac cycle when the ventricle is neither ejecting nor filling) increases rather than falls, all of which blunt the normal rise in cardiac output. We aimed to study the effect of revascularisation on these stress-induced electromechanical abnormalities and their effect on peak cardiac output after coronary artery bypass grafting (CABG). Method: 20 unselected patients were studied before and after CABG. Long axis asynchrony was determined by (i) delay in the onset of shortening, (ii) amplitude and (iii) duration of post-ejection shortening. Total isovolumic time (in s/min), calculated as [60 2 (total ejection time þ total filling time)] and cardiac output were measured by Doppler echocardiography. Results: Before CABG: QRS duration broadened with stress (by 7 ^ 8 ms, P , 0:01Þ and post-ejection shortening increased (amplitude by 1.1 ^ 0.7 mm, P , 0:001; duration by 8 ^ 9 ms, P , 0:01Þ: Total isovolumic time increased (by 3 ^ 3 s/min, P , 0:001Þ and cardiac output rose (by 2.8 ^ 1.2 l/min, P , 0:01Þ: After CABG: QRS duration shortened with stress (by 5 ^ 4 ms, P , 0:01Þ; post-ejection shortening decreased (amplitude and duration fell by 0.4 ^ 0.5 mm and 22 ^ 14 ms, respectively), total isovolumic time shortened (by 3 ^ 3 s/min) and cardiac output increased (by 5.1 ^ 1.8 l/min, all P , 0:001Þ: Changes in total isovolumic time and duration of post-ejection shortening with stress were independent predictors of the increase in peak cardiac output after revascularisation (total R 2 ¼ 0:69). Independent predictors of changes in total isovolumic time with stress were those in QRS duration and the duration of postejection shortening (total R 2 ¼ 0:75Þ: In turn, changes in the duration of post-ejection shortening were closely associated with alterations in the delay in long axis shortening ðr 2 ¼ 0:50Þ; which correlated with changes in QRS duration (r 2 ¼ 0:59; all P , 0:001Þ: Conclusions:

Respiratory therapy control based on cardiac cycle

Abstract: Methods and systems involve adjusting respiratory therapy based on cardiac cycle phase. A parameter indicative of cardiac cycle is sensed and the respiratory therapy is adjusted based on cardiac cycle phase. Modulation of respiratory therapy pressure reinforces the pumping action of the heart and results in increased cardiac output with decreased expenditure of myocardial energy output.

Injury to the Tricuspid Valve and Membranous Atrioventricular Septum Caused by Huge Calcified Right Ventricular Myxoma

Abstract: A 64-year-old female, admitted because of severe dyspnea on exertion and facial edema, showed echocardiographic findings of a large tumor in the right ventricle (RV). Echocardiography revealed a cardiac mass extending from the RV across the tricuspid valve into the right atrium, synchronized with the cardiac cycle, and severe tricuspid regurgitation was apparent. The mass was removed under cardiopulmonary bypass. It measured 7×5×5 cm with diffuse superficial calcification and arose from the posterior wall of the RV, just under the tricuspid valve ring, with a short pedicle. During the same procedure, after the successful excision of the tumor, small atrial and ventricular septal defects were found that had been caused by the tumor and these were closed directly. The tricuspid valve was repaired with valvuloplasty, chordoplasty and annuloplasty. The microscopic findings were of typical myxoma; however, a right ventricular myxoma protruding into the right atrium is exceedingly rare. (Circ J 2004; 68: 799 - 801)

Method and apparatus to optimally measure cardiac depolarization/repolarization instability

Abstract: A method of identifying and measuring alternans in an electrocardiographic (ECG) signal representative of the electric activity of a heart of a patient. The ECG signals from the patient are divided into individual cardiac cycles and the amplitude of four segments of the repolarization portion and the depolarization portion of each cardiac cycle are measured. The amplitude for each of the repolarization segments are measured from a reference baseline that is determined by a first base segment occurring immediately prior to the repolarization portion of the present cardiac cycle and a second base segment occurring immediately before the depolarization portion of the next cardiac cycle in the sequence. Based upon the amplitude measurements over the repolarization and the depolarization portions of each cardiac cycle, digital signal processing is applied to the measurements to generate eigenvariables. A spectral density is calculated for each of the eigenvariables, which spectral densities can be used to determine both the presence of alternans and the respiratory frequency.

Methods, systems and computer program products to inhibit ventricular fibrillation during cardiopulmonary resuscitation

Abstract: Methods, systems and computer program products determine and identify a favorable time to deliver cardiac compression to a subject to avoid a vulnerable period of a spontaneous intrinsic cardiac cycle.

Atrial retrograde management

Abstract: Methods and systems for classifying cardiac responses to pacing stimulation and/or preventing retrograde cardiac conduction are described. Following delivery of a pacing pulse to an atrium of the patient's heart during a cardiac cycle, the system senses in the atrium for a retrograde P-wave. The system classifies the atrial response to the pacing pulse based on detection of the retrograde P-wave. The system may also sense for an atrial evoked response and utilize the atrial evoked response in classifying the cardiac pacing response. If capture is not detected, the system may deliver additional atrial pacing pulses to reduce atrial retrograde conduction. A backup pace may be delivered to prevent the atrial retrograde conduction if an atrial evoked response is not detected during a cardiac cycle. Alternatively, retrograde management may involve delaying a next scheduled pace may be until expiration of an atrial effective refractory period.

Relationship of number of phases per cardiac cycle and accuracy of measurement of left ventricular volumes, ejection fraction, and mass.

Abstract: In cine cardiac magnetic resonance imaging (MRI) studies, for any preset imaging parameters the number of phases per cardiac cycle for a single slice is proportional to breath‐hold duration. We investigated the relationship between the accuracy of measurement of left ventricular (LV) end‐diastolic and end‐systolic volumes (EDV and ESV, respectively), mass and ejection fraction (EF), and the number of phases acquired per cardiac cycle. Twelve adult volunteers underwent cardiac MRI and five complete LV functional studies were obtained with 8, 11, 14, 17, and 20 phases per cardiac cycle. We calculated LV volumes, EF, and mass for each acquisition, and compared them using the 20‐phase acquisition as the reference standard. The scan duration was proportional to the number of phases acquired. There was a systematic underestimation of LV, EDV, and EF, with decreasing number of phases. Differences from the reference standard became significant for the 8‐phase acquisition (p < 0.05). Subgroup analysis showed that ...

Adaptive timing interval control method for treating congestive heart failure

Abstract: A method of treating a heart with an implantable cardiac stimulation device involves transiently disturbing the steady state hemodynamic parameters by altering a cardiac cycle timing interval sufficient to reduce end diastolic volume for that cycle. The cardiac cycle timing interval is then adaptively controlled for successive cardiac cycles to achieve a second set of hemodynamic parameters.

Respiratory motion of the heart: Implications for magnetic resonance coronary angiography

Abstract: Magnetic resonance(MR) coronary imaging is susceptible to artifacts caused by motion of the heart. The purpose of this thesis was to study the respiratory motion of the coronary arteries and to use the results to develop strategies for improved MRimaging. The first section of the thesis describes a MR motion correction technique for objects undergoing a 3D affine transformation. The remainder of the thesis focuses on measuring the respiratory motion of the heart from free breathing x-ray angiograms. Stereo reconstruction methods are used to generate 3D models of the arteries from biplane angiograms. A method for tracking the motion of the arteries in a sequence of biplane images is presented next. The algorithm uses 3D regularizing constraints on the length changes of the arteries and on the spatial regularity of their motion. The algorithm was validated using a deforming vascular phantom. RMS 3D distance errors were measured between centerline models tracked in the x-ray images and gold-standard models derived from a gated 3D MR acquisition. The mean error was 0.69±0.06 mm for four different orientations of the x-ray system. The motion field recovered from free breathing angiograms is a combination of the cardiac contraction and respiratory motion of the heart. A cardiac respiratory parametric model is formulated to decompose the field into independent cardiac and respiratory components. Results are presented for ten patients imaged during spontaneous tidal breathing. For all patients, the heart translated caudally (mean, 4.9±1.9 mm ) and rotated in a cranio-dorsal direction (mean, 1.5°±0.9°) during inspiration. In eight patients, the heart also translated anteriorly (mean, 1.3±1.8 mm ) and rotated in a caudo-dextral direction (mean, 1.2°±1.3°). Anatomic landmarks were used to compare results across patients. Three dimensional displacements and velocities were compared, and quiescent periods in the respiratory and cardiac cycles were measured. Finally, respiratory motion was analyzed using three linear motion models that correspond to available MR motion correction techniques: translation, rigid body, and affine. Calculations indicate that a two-to-four-fold increase in scan efficiency is attainable, resulting in reduced scan times while maintaining image quality.

Assessment of coronary artery and cardiac function using multidetector CT.

Abstract: Multidetector CT is able to reconstruct artifact-less cardiac images due to improved temporal resolution. In this article, we review the potential benefits of the cardiac application of multidetector CT in the assessment of coronary artery and cardiac function, such as wall motion and systolic thickening. By applying retrospective ECG-gating, 10 phases throughout 1 cardiac cycle are extracted for functional analysis. Animated movies are generated by paging through these 2D and 3D images in cardiac phase order. Left ventricular end-diastolic volume, end-systolic volume, and ejection fraction can also be generated. Using the data acquired during a single breath hold, coronary artery and cardiac function can be assessed by multidetector CT.

Determination of aortic pressure-time profile, along with aortic stiffness and peripheral resistance

Abstract: Aortic pressure measurement is of significant clinical importance However, the techniques require invasive approach, such as cardiac catheterization In this study, we are providing the analysis for the aortic pressure to be determined non-invasively, as well as indicating how it can be employed to determine cardiac contractility, compliance and peripheral resistance We record systolic and diastolic pressure during the cardiac cycle using cuff method, assumed that the systolic phase of the supra-systolic cuff signal and the diastolic phase of the sub-diastolic cuff signal most closely approximate systolic and diastolic aortic pressure, respectively The pressure curves for the systolic phase are derived from the aortic volume-time curve In both Ayuredic-medicine and traditional Chinese-medicine, the pressure-pulse shape is felt to provide diagnosis information concerning diseases and disorders In this regard, a precise evaluation of the aortic pressure-time profile and correlation of its shape parameters with diseases (using traditional Chinese and Ayuredic medical knowledge-base system) would constitute a significant contribution to medicine