Influence of recipient atrial contraction on left ventricular filling dynamics of the transplanted heart assessed by Doppler echocardiography

Recipient atrial remnants retain electrical and mechanical activity after orthotopic cardiac transplantation. This study investigated the influence of recipient atrial contraction timing on Doppler ultrasound mitral flow velocity curves, isovolumic relaxation time, peak early mitral flow velocity (M₁), mitral valve pressure half-time and peak mitral flow velocity due to atrial systole (M₂). Clearly identifiable recipient atrial electrical activity (P waves) was present in 7 of 10 patients studied early postoperatively 2 to 6 months (mean 2.5) (early group) and in 20 of 24 patients seen 1 to 11 years (mean 3) after transplantation (late group). Median age and gender distribution were similar in both groups. For analysis of its influence on isovolumic relaxation time, pressure half-time and M₁, recipient atrial contraction was classified by its position in the cardiac cycle as early systole, late systole or diastole. For analysis of M₂, it was classified as early diastole, late diastole or systole. Compared with its occurrence in diastole, recipient atrial contraction in late systole was associated with a shorter isovolumic relaxation time, shorter pressure half-time and higher M₁. In early systole it was associated with a longer pressure half-time and lower M₁ than in diastole; isovolumic relaxation time was unchanged. Recipient atrial contraction in early diastole resulted in a lower M₂ than in systole, whereas simultaneous contraction of recipient and donor atria in late diastole resulted in an increase in M₂. These results indicate that the timing of recipient atrial contraction and relaxation significantly influences left ventricular filling dynamics.