GENESIS OF THE AUSTIN FLINT MURMUR - RELATION TO MITRAL INFLOW AND AORTIC REGURGITANT FLOW DYNAMICS

Objectives. This study was designed to elucidate the genesis of the Au stin Flint murmur. Background. The Austin Flint murmur is an apical di astolic rumble associated with significant aortic regurgitation. The p recise mechanism of the murmur remains unclear. Methods. The relation between the Austin Flint murmur and mitral inflow and aortic regurgita nt flow dynamics was evaluated nonivasively in 13 patients with modera te to severe aortic regurgitation and 15 control subjects using phonoc ardiographic and pulsed and color-coded Doppler echocardiographic tech niques. The severity of aortic regurgitation was determined by color-c oded Doppler echocardiography on the basis of the maximal distance of the regurgitant signal. Results. The direction of aortic regurgitant f low was unrelated to the presence of the Austin Flint murmur. The seve rity of aortic regurgitation was greater in patients with than in thos e without this murmur. The peak mitral inflow velocity during early di astole (E) was significantly increased, and both peak mitral inflow ve locity at atrial contraction (A) and the A/E ratio were significantly decreased in patients with the Austin Flint murmur compared with value s in those without this murmur or in control subjects. However, the ma ximal amplitude of the Austin Flint murmur did not coincide temporally with the peak mitral inflow velocity. The murmur continued both after rapid mitral inflow had ended and during diastolic mitral regurgitati on. Conclusions. The increased velocity of early diastolic mitral infl ow in patients with the Austin Flint murmur is due to aortic regurgita tion, but rapid mitral inflow is not an essential requirement for prod uction of the murmur. In some cases, the Austin Flint murmur may be ge nerated by aortic regurgitant flow alone.