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The isovolumetric contraction phase lasts about 0.05 seconds, [1] but this short period of time is enough to build up a sufficiently high pressure that eventually overcomes that of the aorta and the pulmonary artery upon opening of the semilunar valves. This process, therefore, helps maintain the correct unidirectional flow of blood through the ...
This is the ejection stage of the cardiac cycle; it is depicted (see circular diagram) as the ventricular systole–first phase followed by the ventricular systole–second phase. [2] After ventricular pressures fall below their peak(s) and below those in the trunks of the aorta and pulmonary arteries, the aortic and pulmonary valves close ...
Consequently, this initial phase of ventricular systole is known as isovolumic contraction, also called isovolumetric contraction. [1] In the second phase of ventricular systole, the ventricular ejection phase, the contraction of the ventricular muscle has raised the pressure within the ventricle to the point that it is greater than the ...
Electrical waves track a systole (a contraction) of the heart. The end-point of the P wave depolarization is the start-point of the atrial stage of systole. The ventricular stage of systole begins at the R peak of the QRS wave complex; the T wave indicates the end of ventricular contraction, after which ventricular relaxation (ventricular diastole) begins.
The Pressure-volume area (PVA) represents the total mechanical energy generated by ventricular contraction. This is equal to the sum of the stroke work (SW), encompassed within the PV loop, and the elastic potential energy (PE). In mathematical terms, = +
As the left posterior fascicle is shorter and broader than the right, impulses reach the papillary muscles just prior to depolarization, and therefore contraction, of the left ventricle myocardium. This allows pre-tensioning of the chordae tendinae, increasing the resistance to flow through the mitral valve during left ventricular contraction. [5]
The standard model used to understand the cardiac action potential is that of the ventricular myocyte. Outlined below are the five phases of the ventricular myocyte action potential, with reference also to the SAN action potential. Figure 2a: Ventricular action potential (left) and sinoatrial node action potential (right) waveforms.
[1] [2] In the Wiggers diagram, the X-axis is used to plot time subdivided into the cardiac phases, while the Y-axis typically contains the following on a single grid: Blood pressure. Aortic pressure; Ventricular pressure; Atrial pressure; Ventricular volume; Electrocardiogram; Arterial flow (optional) Heart sounds (optional)