The alternating pulse is a pathological phenomenon in which the pulse rhythm is normal and the pulse strength alternates, and is evident in the sitting position. It is often associated with alternating strength of ventricular contraction and is often indicative of left heart insufficiency. The occurrence of alternating pulses in relation to the alternating strength of left ventricular contraction suggests myocardial injury and failure, and is strong evidence of occult heart failure. There are two views on the mechanism of its generation. Some people propose that weak beats are caused by a decrease in the number of myocardial fibers participating in ventricular contraction, when part of the heart is in relative under-supply and all myocardial fibers contract during the next beat. Etiology 1. Heart disease Various organic heart diseases that cause left heart failure, such as severe hypertension, severe coronary artery disease, dilated cardiomyopathy, etc. 2, arrhythmia Digitalis toxicity, paroxysmal tachycardia, and atrial fibrillation. Premature beats can also be followed by transient alternating pulses.