THE FIRST HEART-SOUND IN ATRIAL SEPTAL-DEFECT WITH REFERENCE TO ATRIOVENTRICULAR VALVE MOTION AND HEMODYNAMICS

To clarify the characteristics of the first heart sound in atrial sept al defect (ASD) and its pathophysiological basis, 17 patients with ASD associated with incomplete right bundle branch block (IRBBB) and 7 wi th isolated IRBBB were studied using phonoechocardiography and Doppler echocardiography. Fifteen of the 17 ASD patients also were studied fo llowing surgical closure of the defect. Indices were compared among th e preoperative ASD, postoperative ASD, and IRBBB groups including: P-Q intervals, loudness of the mitral and tricuspid component of the firs t heart sound (IM, IT), end-diastolic closing excursions of the mitral and tricuspid valves (Mx, IT), and mitral and tricuspid inflow veloci ties during early diastole and atrial contraction. There were no signi ficant differences in the P-Q intervals among these 3 groups. IM was a ttenuated, and IT was accentuated in ASD compared with IRBBB. Postoper atively, IM was augmented in all but 1 patient and IT was attenuated i n all patients. Mx was significantly smaller, and IT was significantly larger in ASD than in IRBBB. Postoperatively, Mx was significantly in creased and Tx was significantly reduced; the maximal mitral inflow ve locity during atrial contraction was increased while the maximal tricu spid inflow velocity was significantly reduced. Thus, the first heart sound in ASD is characterized by an attenuated mitral component and an accentuated tricuspid component. Hemodynamic alterations and conseque nt changes in closing energies of the atrioventricular valves probably account for these features.