Cardiac cycle

About: Cardiac cycle is a research topic. Over the lifetime, 3290 publications have been published within this topic receiving 96159 citations.

Hemodynamic characteristics at the rupture site of cerebral aneurysms: a case study.

Abstract: Background and importance Hemodynamics play an important role in the mechanisms of aneurysm formation, growth, and rupture However, little is known about the hemodynamics of rupture sites Clinical presentation We incidentally acquired 3-dimensional images before and at the moment of rebleeding of a cerebral aneurysm in a patient Comparison of these 2 images enabled precise identification of the rupture site On the basis of computational fluid dynamics simulation, we propose that there are characteristic hemodynamic parameters of the rupture site in cerebral aneurysms We evaluated flow velocity, wall shear stress (WSS), pressure, and the oscillatory shear index to determine characteristic parameters at the rupture site Among the hemodynamic parameters in the cardiac cycle, the rupture site was most markedly distinguished by a combination of low WSS at end diastole and high pressure at peak systole The flow patterns around the rupture site uniquely changed in the cardiac cycle The rupture site was an impingement zone at peak systole Flow separation at the rupture site was observed at end diastole Conclusion In this case, a region with low WSS at end diastole and high pressure at peak systole was at the rupture site A possible mechanism of rupture in this particular aneurysm is that low WSS at end diastole caused degeneration and thinning of the aneurysm wall and that high pressure at peak systole (impingement zone) resulted in rupture of the thinning wall

Diastolic "locking" of the mitral valve: the importance of atrial systole and intraventricular volume.

Abstract: Diastolic mitral valve "locking," defined as sustained diastolic closure of the mitral valve after atrial systole, was investigated by simultaneous hemodynamic and echocardiographic recordings during a protocol of programmed pacing in six dogs with surgically induced atrioventricular block. Atrial extrasystoles were introduced at progressively increasing coupling intervals during programmed prolonged pauses in ventricular pacing. As the coupling interval of the atrial extrasystole was increased, both the mitral reopening time (MRT) and the calculated left ventricular volume (LVV) at the end of the MRT increased proportionally. These interrelations could be best expressed by a general logarithmic function of the form y = a + b ln (x), where x = the coupling interval of the atrial extrasystole and y = the MRT or the LVV. Correlations between the measured data and the predicted data were excellent (r greater than or equal to 0.95). In each dog, a specific LVV had to be attained to allow a diastolic "locking" of the mitral valve. Atrial standstill and atrial fibrillation were also induced in each dog to study the relative role of atrial systole in locking of the mitral valve. During either atrial standstill or atrial fibrillation, the mitral valve closed transiently, but did not lock, despite the accumulation of a LVV larger than the LVV necessary to lock the valve during sinus rhythm. Thus, diastolic locking of the mitral valve has several determinants, including the presence of active atrial systole and the accumulation of a sufficient intraventricular volume.

Hemodynamic sequelae of idioventricular pacemaking in complete heart block

Abstract: Systemic arterial and right heart pressure curves are reviewed in 3 patients with complete heart block. In all three the ventricles were driven by ventricular pacemakers so that the normal sequence of atrioventricular contraction was absent. Some of the hemodynamic consequences of such idioventricular pacemaking are reviewed, and the important role played by atrial systole in ventricular filling is emphasized.

MR Image-Based Geometric and Hemodynamic Investigation of the Right Coronary Artery with Dynamic Vessel Motion

Abstract: The aim of this study was to develop a fully subject-specific model of the right coronary artery (RCA), including dynamic vessel motion, for computational analysis to assess the effects of cardiac-induced motion on hemodynamics and resulting wall shear stress (WSS). Vascular geometries were acquired in the right coronary artery (RCA) of a healthy volunteer using a navigator-gated interleaved spiral sequence at 14 time points during the cardiac cycle. A high temporal resolution velocity waveform was also acquired in the proximal region. Cardiac-induced dynamic vessel motion was calculated by interpolating the geometries with an active contour model and a computational fluid dynamic (CFD) simulation with fully subject-specific information was carried out using this model. The results showed the expected variation of vessel radius and curvature throughout the cardiac cycle, and also revealed that dynamic motion of the right coronary artery consequent to cardiac motion had significant effects on instantaneous WSS and oscillatory shear index. Subject-specific MRI-based CFD is feasible and, if scan duration could be shortened, this method may have potential as a non-invasive tool to investigate the physiological and pathological role of hemodynamics in human coronary arteries.

Deductive Echocardiographic Analysis in Infants with Congenital Heart Disease

Abstract: A step-by-step approach to cardiac diagnosis utilizing a chest X-ray and echocardiography is described and used to study a normal infant and six infant patients with angiocardiographically-proven complex congenital heart malformations The heart is divided into three major anatomical segments in order to localize the atrial and ventricular chambers and determine the relationship of the great arteries The atrial chambers are localized by noting the position of the liver on the X-ray The right atrium is on the same side as the liver with few exceptions The ventricular chambers are localized by echocardiographically identifying the tricuspid and mitral valves They are a part of the morphologically right and left ventricles, respectively As a general rule, the atrioventricular valve whose anterior leaflet is continuous with the posterior margin of a semilunar valve is the mitral valve The atrioventricular valve whose anterior leaflet is not continuous with a posterior semilunar valve margin is the tricu