Cardiac cycle

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

The Effect of Cycle Length on the Time of Occurrence of the First Heart Sound and the Opening Snap in Mitral Stenosis

Abstract: Phonocardiography is often more valuable than electrocardiography in timing mechanical events in the cardiac cycle. This study shows that the opening and closing of the mitral valve are related to the length of the previous heart cycle as demonstrated by the variations occuring in auricular fibrillation. These variations in valve action are controlled by the pressure gradient between left auricle and ventricle.

Method and apparatus for assessing cardiovascular performance

Abstract: A method of assessing the cardiovascular performance of a subject, by: applying periodically, in synchronism with every n th heart cardiac cycle wherein "n" is at least two, external pressure pulsations on a peripheral organ of the subject sufficient to alter ventricular loading; acquiring data representative of the ventricular pressure, and data representative of the ventricular volume, of the subject's heart over a plurality of heart cardiac cycles; and utilizing such data for assessing the cardiovascular performance of the subject. Ventricular loading may be altered by impeding ventricular ejection (changing afterload), and/or by altering venous return to the heart (changing preload).

Studying Dynamic Myofiber Aggregate Reorientation in Dilated Cardiomyopathy Using In Vivo Magnetic Resonance Diffusion Tensor Imaging

Abstract: Background— The objective of this study is to assess the dynamic alterations of myocardial microstructure and strain between diastole and systole in patients with dilated cardiomyopathy relative to healthy controls using the magnetic resonance diffusion tensor imaging, myocardial tagging, and biomechanical modeling. Methods and Results— Dual heart-phase diffusion tensor imaging was successfully performed in 9 patients and 9 controls. Tagging data were acquired for the diffusion tensor strain correction and cardiac motion analysis. Mean diffusivity, fractional anisotropy, and myocyte aggregate orientations were compared between both cohorts. Cardiac function was assessed by left ventricular ejection fraction, torsion, and strain. Computational modeling was used to study the impact of cardiac shape on fiber reorientation and how fiber orientations affect strain. In patients with dilated cardiomyopathy, a more longitudinal orientation of diastolic myofiber aggregates was measured compared with controls. Although a significant steepening of helix angles (HAs) during contraction was found in the controls, consistent change in HAs during contraction was absent in patients. Left ventricular ejection fraction, cardiac torsion, and strain were significantly lower in the patients compared with controls. Computational modeling revealed that the dilated heart results in reduced HA changes compared with a normal heart. Reduced torsion was found to be exacerbated by steeper HAs. Conclusions— Diffusion tensor imaging revealed reduced reorientation of myofiber aggregates during cardiac contraction in patients with dilated cardiomyopathy relative to controls. Left ventricular remodeling seems to be an important factor in the changes to myocyte orientation. Steeper HAs are coupled with a worsening in strain and torsion. Overall, the findings provide new insights into the structural alterations in patients with dilated cardiomyopathy.