Left atrial volumes and function in orthotopic cardiac transplantation

Early ventricular filling and therefore passive left atrial emptying may be impaired in patients with cardiac transplantation. As a result, left atrial function may be an important factor in maintaining stroke volume in recipients of orthotopic cardiac transplants. Left atrial volumes maximal (mitral valve opening), minimal (mitral valve closure), and oset of atrial systole (P wave on electrocardiogram) were determined by echocardiography using the biplane area—length method in 12 patients after cardiac transplantation and 12 control subjects. Maximal and minimal left atrial volumes and left atrial volumes at onset of atrial systole were larger in patients who had cardiac transplantation than in control subjects (89.8 vs 41.8 cm3, 48 vs 15.2 cm3, and 70.4 vs 27.0 cm3, respectively; p < 0.01). In patients undergoing cardiac transplantation, good correlations were found between left atrial maximal volume and left ventricular mass (p = 0.58) and between left atrial maximal volume and mean pulmonary capillary wedge pressure (r = 0.81). Left atrial passive emptying volume (maximal minus volume at P wave) was not statistically different between the two groups (19.3 in patients receiving transplants vs 14.7 cm3 in control subjects), but left atrial stroke volume (beginning atrial systole to minimal) was larger in patients receiving transplants than in control subjects (22.4 vs 11.8 cm3, respectively; p < 0.001). Thus left atrial contraction contributed 42% to the left ventricular stroke volume in patients who had cardiac transplantation but only 17% in control subjects (p < 0.01). Left atrial ejection fraction (left atrial stroke volume/volume atrial systole) was decreased in patients who had cardiac transplantation compared with control subjects (33.8 vs 43.8; p = 0.02); a linear inverse correlation (p = 0.46) was found between left atrial volume at onset of atrial systole and left atrial ejection fraction. As left atrial volume at onset of atrial systole increased, the left atrial ejection fraction decreased; this finding suggests left atrial systolic dysfunction after transplantation. There was no correlation between left atrial volume at onset of atrial systole and left atrial ejection fraction in control subjects. Thus, despite left atrial dysfunction in patients undergoing cardiac transplantation, left atrial contraction plays an important role in maintaiing left ventricular stroke volume.