Topic
Cardiac cycle
About: Cardiac cycle is a research topic. Over the lifetime, 3290 publications have been published within this topic receiving 96159 citations.
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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.
36 citations
TL;DR: The observations reported in this paper support the view that a vigorous and properly timed atrial contraction provides a mechanism by which mean atrial pressure is maintained at a substantially lower level for any ventricular end-diastolic pressure than would be the case if these functions of the atrium were not operative.
Abstract: The observations reported in this paper support the view that a vigorous and properly timed atrial contraction, by transporting blood into the ventricle and by approximating the atrioventricular valve prior to ventricular systole, provides a mechanism by which mean atrial pressure is maintained at a substantially lower level for any ventricular end-diastolic pressure than would be the case if these functions of the atrium were not operative. The central nervous system, by way of efferent sympathetic pathways, can regulate appropriately the vigor and timing of atrial systole as well as the duration of the diastolic filling period. The net effect of such regulation is to decrease mean atrial pressure at any given heart rate and cardiac output, and to permit rapid heart rates which could not otherwise be tolerated without elevations of atrial pressure. The fact that MLAP-LVEDP is independent of aortic pressure and stroke volume, and of heart rate over certain ranges suggests that this hemodynamic measurement is uniquely dependent on, and therefore useful in the analysis of, atrial performance.
36 citations
01 Dec 2005
TL;DR: An electrocardiogram is a measure of how the electrical activity of the heart changes over time as action potentials propagate throughout the heart during each cardiac cycle.
Abstract: An electrocardiogram (ECG; in German, the electrokardiogram, EKG) is a measure of how the electrical activity of the heart changes over time as action potentials propagate throughout the heart during each cardiac cycle However, this is not a direct measure of the cellular depolarization and repolarization with the heart, but rather the relative, cumulative magnitude of populations of cells eliciting changes in their membrane potentials at a given point in time; it shows electrical differences across the heart when depolarization and repolarization of these atrial and ventricular cells occur
36 citations
TL;DR: Since the onset ofleft ventricular systole, with respect to left ventricular stimulation, is considerably delayed in VDD pacemaker patients a short atrioventricular interval is required in these patients to maintain the normal time relations between atrial and ventricular contraction and hence maximise left vent cardiac filling.
Abstract: The effect of mitral valve closure on left ventricular filling time and its relation to the onset of systole were assessed from mitral valve echocardiograms and simultaneous apex cardiograms in 21 normal subjects, 11 patients with left bundle branch block, and 19 patients with VDD pacemakers programmed for atrioventricular intervals of 50, 150, and 250 ms. The interval between the electrocardiograph Q wave and the apex cardiogram upstroke was similar in normal subjects and patients with left bundle branch block, but was significantly longer in patients with VDD pacemakers at all atrioventricular intervals. Similarly there was little difference in the time interval between the Q wave and mitral valve closure in normal individuals and patients with left bundle branch block but this was considerably delayed in VDD pacemaker patients with the atrioventricular interval set at 50 ms. With increasing atrioventricular intervals the mitral valve closed significantly earlier, whereas the onset of left ventricular systole and the timing of mitral valve opening remained unchanged. Thus as a result of earlier mitral valve closure left ventricular filling time decreased progressively as the atrioventricular interval was increased. Since the onset of left ventricular systole, with respect to left ventricular stimulation, is considerably delayed in VDD pacemaker patients a short atrioventricular interval is required in these patients to maintain the normal time relations between atrial and ventricular contraction and hence maximise left ventricular filling.
36 citations
TL;DR: ECG-gated dynamic CTA is feasible on a 64-slice scanner with a standard radiation dose and can detect potentially serious consequences of EVAR, which alters renal artery motion by limiting proximal motion while leaving distal motion unaffected.
Abstract: Purpose:To observe the natural renal artery motion during cardiac cycles in patients with abdominal aortic aneurysm (AAA) and how the implantation of stent-grafts may distort this movement.Methods:Data on 29 renal arteries from 15 male patients (mean age 72.6 years, range 66–83) treated with Talent or Excluder stent-grafts were acquired using an electrocardiographically (ECG)-gated dynamic 64-slice CT scanner. ECG-triggered retrospective reconstructions were made at 8 equidistant time points over the R-R cardiac cycle. The gated datasets were reconstructed perpendicular to the center flow lumen of each renal artery at 1.2 and 2.4 cm from the renal ostium. Center of mass displacement was determined per cardiac cycle for pre- and post-EVAR renal arteries and compared.Results:Normal renal artery motion in AAA patients was impressive, with up to 3-mm movement both near and distant from the aorta (mean 2.0±0.6 mm, range 1.1–3.0). EVAR inhibited proximal renal motion, resulting in a 31% decrease in maximal move...
36 citations