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: Diastolic mitral and tricuspid regurgitation are almost universally present in patients with AV block and are associated with a diastolic murmur, which coincides with forward AV valve flow.
93 citations
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TL;DR: The increase in atrial epsilon throughout the cardiac cycle is likely reflecting the improvement of atrial compliance and lead to LA reverse remodeling with reduction of LA size before and after atrial systole.
93 citations
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TL;DR: It is concluded that atrial systole significantly improves cardiac function in man under the conditions of the authors' study.
Abstract: 1. 1. The contribution of atrial systole to cardiovascular dynamics was described in 21 patients with complete heart block at a fixed and at a variable ventricular rate. 2. 2. It was demonstrated that a properly timed atrial systole significantly improves cardiac function in patients with complete heart block. The optimal P-R interval was found to occur between 1 and 300 msec. For this range there were 13, 14, 6, 12, 14 and 33 per cent increases in ejection time, mechanical systole, isometric contraction time, systemic pressure, peak derivative of brachial artery pressure and tensiontime index, respectively, as compared with figures obtained when atrial systole occurred during ventricular systole. 3. 3. It was also found that the contribution of atrial systole to cardiac function occurs in all ranges of ventricular rates studied (20 to 125 beats/min.). However, the maximal beneficial effect of atrial systole was found to occur for the ventricular rate in the range of 51 to 80 beats/min. 4. 4. Very short or very long P-R intervals resulted in minor changes in the measured parameters, and the figures obtained closely approach the ones determined when atrial systole occurred during ventricular systole. 5. 5. It is, therefore, concluded that atrial systole significantly improves cardiac function in man under the conditions of our study.
92 citations
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TL;DR: It has been demonstrated that in patients with mitral stenosis, a normal cardiac output can be delivered only at the expense of high pulmonary “capillary” pressure.
92 citations
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TL;DR: Measurements of mean velocity patterns indicate that the surfaces of the blood sac and valve tracts are exposed to significant levels of wall shear stress during some portion of the flow cycle, and there is no location where the flow is stagnant over the entire flow cycle.
Abstract: Laser Doppler Anemometry measurements of mean (ensemble average) velocities and turbulent (Reynolds) stresses at 140 locations within the left ventricle of the Penn State 70 cc electric artificial heart/ventricular assist device are reported at 8 times during the cardiac cycle. Mean velocity patterns indicate that the surfaces of the blood sac and valve tracts are exposed to significant levels of wall shear stress (good wall washing) during some portion of the flow cycle, and there is no location where the flow is stagnant over the entire flow cycle. This implies that thrombus deposition within the artificial heart should be suppressed. Turbulent stresses in the main pumping chamber and the outflow tracts of the tilting disk valves do not exceed 2000 dynes/cm2. The highest turbulent stresses (20,000 dynes/cm2) and smallest turbulent microscales (6 microns) are found in the regurgitant jets on the minor orifice side of the aortic valve during diastole and the mitral valve during systole. Taken together, the data suggest that improvements in artificial heart fluid mechanics will come through valve design and pump operating conditions, not pumping chamber design.
92 citations