Non-invasive assessment of changes in left ventricular relaxation by combined phono-, echo-, and mechanocardiography

In order to investigate interrelations between early diastolic events, simultaneous apex-, phono-, and echocardiograms were recorded in 10 normal subjects and 55 patients with ischaemic heart disease. In normal subjects isovolumic relaxation time measured as A2 to mitral valve opening was 72±9 ms, the interval A2-0 point was 116±15 ms, and the amplitude of the f wave of the apexcardiogram relative to the total amplitude was 11±2%. In patients with a normal left ventricular end-diastolic pressure (<15 mmHg), isovolumic relaxation time was prolonged to 99±18 ms, A2-0 point to 162±5 ms, and the relative height of the f wave was increased to 21±4%. Isovolumic relaxation time and A2-0 point interval both showed significant inverse correlation with left ventricular diastolic pressure. Glyceryl trinitrate administration of isometric stress both caused well recognised changes in arterial pressure and cavity size. Neither had any additional effect during early diastole in normal subjects. In the patients, however, glyceryl trinitrate prolonged isovolumic relaxation time, delayed the 0 point of the apexcardiogram with respect to A2, increased the interval 0 point - f wave, and reduced the relative amplitude of the f wave. Isometric stress had the opposite effects. These changes extend beyond the end of ventricular relaxation and so are more readily explained on a mechanical basis, possibly as oscillations whose periodicity and degree of damping were increased by glyceryl trinitrate and decreased by isometric stress.