Diastolic mitral regurgitation with atrioventricular conduction abnormalities: relation of mitral flow velocity to transmitral pressure gradients in conscious dogs.

Diastolic mitral regurgitation is a common finding that can be detected with use of Doppler echocardiographic techniques in patients with atrioventricular (AV) conduction abnormalities. With use of simultaneous hemodynamic and Doppler techniques, mitral flow velocity, mitral valve motion and transmitral pressure gradient were studied during 50 cardiac cycles each of spontaneous or atrial paced first- and second-degree AV block in five lightly sedated dogs. Diastolic mitral regurgitation was detected during atrial relaxation on all beats in which ventricular contraction was delayed greater than 190 ms. In all dogs the diastolic regurgitation was associated with a reverse transmitral pressure gradient (3.7 +/- 1.1 mm Hg in first-degree AV block and 3.2 +/- 1.5 mm Hg in second-degree AV block) that occurred primarily as the result of a decrease in atrial pressure with atrial relaxation. These reverse pressure gradients were as large as the maximal forward transmitral gradients in early diastole (2.9 +/- 0.9 mm Hg in first-degree AV block and 3.1 +/- 0.7 mm Hg in second-degree AV block) and larger than the maximal forward pressure gradients at atrial contraction (1.7 +/- 0.5 and 1.4 +/- 0.6 mm Hg, respectively, p less than 0.05). The maximal reverse pressure gradient during atrial relaxation was also as large as the reverse pressure gradient in mid-diastole (2.7 +/- 0.9 and 2.8 +/- 1.0 mm Hg, respectively), associated with deceleration of early diastolic mitral flow. Peak diastolic mitral regurgitation velocity coincided with the maximal reverse transmitral gradient and was usually larger than anterograde mitral flow velocity.(ABSTRACT TRUNCATED AT 250 WORDS)