LEFT ATRIAL VOLUMES AND FUNCTION IN ORTHOTOPIC CARDIAC TRANSPLANTATION

Early ventricular filling and therefore passive left atrial emptying m ay 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 vo lumes maximal (mitral valve opening), minimal (mitral valve closure), and onset of atrial systole (P wave on electrocardiogram) were determi ned by echocardiography using the biplane area-length method in 12 pat ients after cardiac transplantation and 12 control subjects. Maximal a nd minimal left atrial volumes and left atrial volumes at onset of atr ial systole were larger in patients who had cardiac transplantation th an in control subjects (89.8 vs 41.8 cm(3), 48 vs 15.2 cm(3), and 70.4 vs 27.0 cm(3), respectively; p < 0.01). In patients undergoing cardia c transplantation, good correlations were found between left atrial ma ximal volume and left ventricular mass (r = 0.56) and between left atr ial maximal volume and mean pulmonary capillary wedge pressure (r = 0. 81). Left atrial passive emptying volume (maximal minus volume at P wa ve) was not statistically different between the two groups (19.3 in pa tients receiving transplants vs 14.7 cm(3) in control subjects), but l eft atrial stroke volume (beginning atrial systole to minimal) was lar ger in patients receiving transplants than in control subjects (22.4 v s 11.8 cm(3), respectively; p < 0.001). Thus left atrial contraction c ontributed 42% to the left ventricular stroke volume in patients who h ad cardiac transplantation but only 17% in control subjects (p < 0.01) . Left atrial ejection fraction (left atrial stroke volume/volume atri al systole) was decreased in patients who had cardiac transplantation compared with control subjects (33.8 vs 43.8; p = 0.02); a linear inve rse correlation (r = -0.46) was found between left atrial volume at on set of atrial systole and left atrial ejection fraction. As left atria l volume at onset of atrial systole increased, the left atrial ejectio n fraction decreased; this finding suggests left atrial systolic dysfu nction after transplantation. There was no correlation between left at rial volume at onset of atrial systole and left atrial ejection fracti on in control subjects. Thus, despite left atrial dysfunction in patie nts undergoing cardiac transplantation, left atrial contraction plays an important role in maintaining left ventricular stroke volume.