Classification of etiology 1. Various organic heart diseases that cause left heart failure, such as severe hypertension, severe coronary. Has disease, dilated cardiomyopathy and so on. 2, digitalis poisoning, paroxysmal tachycardia and atrial active. 3, premature beats can also cause a transient alternating pulse. Mechanism The occurrence of alternating pulse is related to the alternating strength of left ventricular contractility, suggesting myocardial injury and failure, and is a strong evidence of occult heart failure. There are two views on the mechanism, some people propose that the weak beat is due to the reduction of myocardial fibers participating in ventricular contraction, at this time part of the heart is in relative stress, in the next heart beat, all myocardial fibers undergo contraction, so that a strong pulse is generated. Another person put forward the explanation that the degree of ventricular diastole is not equal, that when the heart is filled with more blood volume, its beat is enhanced, and vice versa, it is weak, strong and weak alternately, it is an alternating pulse. When the venous filling pressure is reduced, the alternating pulse is more pronounced, and vice versa, so that the alternating pulse often appears before the onset of significant right-sided hemorrhagic heart failure.