Search results
Results from the WOW.Com Content Network
The first finding is that junctional rhythms are regular rhythms. This means that the time interval between beats stays constant. The next normal finding is a normal QRS. Since the impulse still travels down the bundle of His, the QRS will not be wide. Junctional rhythms can present with either bradycardia, a normal heart rate, or tachycardia. [9]
Cardiac rhythmicity is the spontaneous depolarization and repolarization event that occurs in a repetitive and stable manner within the cardiac muscle. Rhythmicity is often abnormal or lost in cases of cardiac dysfunction or cardiac failure.
Increased catecholamine levels promote positive lusitropy, enabling the heart to relax more rapidly. This effect is mediated by the phosphorylation of phospholamban and troponin I via a cAMP-dependent pathway. Catecholamine-induced calcium influx into the sarcoplasmic reticulum increases both inotropy and lusitropy.
A typical heart rate is 75 beats per minute (bpm), which means that the cardiac cycle that produces one heartbeat, lasts for less than one second. The cycle requires 0.3 sec in ventricular systole (contraction)—pumping blood to all body systems from the two ventricles; and 0.5 sec in diastole (dilation), re-filling the four chambers of the ...
It is almost always indicative of left ventricular systolic impairment, and carries a poor prognosis. The condition is relatively rare, and patients with the greatest risk for developing pulsus alternans include those with heart failure, cardiomyopathy , coronary artery disease, or other cardiac risk factors.
The section shows: 1) the opened ventricles contracting once per heartbeat—that is, once per each cardiac cycle; 2) the (partly obscured) mitral valve of the left heart; 3) the tricuspid and pulmonary valves of the right heart—note these paired valves open and close oppositely. + (The aortic valve of the left heart is located below the ...
The normal heart rate of the fetus is between 110 and 160 beats per minute. Any rhythm beyond these limits is abnormal and classed as a fetal arrhythmia. These are mainly the result of premature atrial contractions, usually give no symptoms, and have little consequence.
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.