CARDIAC CYCLE ANALYSIS

Physiological cardiac cycle begins with atrial systole, and the clinical with the ventricular systole. Atrial systole takes 0.1 seconds and is concomitant with ventricular diastole; ventricular systole takes 0.27 seconds and is concomitant with atrial diastole; and general diastole takes 0.43 sec.

Right atrial systole start before the left (due to being the starting point of the stimulus contraction). Ventricular systole start early to the left (for that is activated first before left ventricular septum); period in which the left ventricle (Vs) is enclosed cavity is longer than the right ventricle (Vd) is closed cavity (due to differences in the aorta and pulmonary pressure).

In ventricular systole, open the pulmonary valve and aortic valve then; in diastole, aortic valve closes first and then pulmonary valve. It follows from the foregoing that periods ejection of the two ventricles differ (Vs <Vd). Supine normal sinus rhythm is between 60-90 beats / minute; tachycardia cardiac cycle shortens (0.6 sec.), with greater reduction of diastole, systole compared.

The duration depends on the intrinsic systole of myocardium (the power of contractile, actin-myosin interaction). Shortens systolic tachycardia by increasing inotropic state. The length of the fibers depends on the contraction degree of synchronization of electrical activation. The duration of systole also depends on the extracardiac factors (in particular hemodynamic) to preload ventricular diastolic blood during the previous (end-diastolic volume).

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