Characteristics of presystolic flow in the superior vena cava: new thoughts on a forgotten sound.

Cross sectional, M mode, and Doppler echocardiography, apexcardiography, and phonocardiography were used to characterise presystolic cardiovascular sounds in three patients with ventricular disease. Although the aetiology was different (dilated cardiomyopathy, primary pulmonary hypertension, and chronic pulmonary thromboembolic disease), in each case the presystolic sound was associated with a rapid change in acceleration of blood and with flow reversal in the superior vena cava, and could only be recorded at the right sternal edge or over the jugular veins. Such flow characteristics may be explained by a raised ventricular end diastolic pressure with reduced compliance. Use of these techniques helps to understand the cause of a previously described but little recognised heart sound, and adds weight to the interpretation of its presence in disease.