The electrocardiographic tracing shows second degree A-V block with 2:1 conduction. In the videos the mitral regurgitation is occurring in diastole which is evident after the non-conducted p wave. On color M-mode of mitral and tricuspid flow (figures 1 & 2) this is pointed to by the large green arrows. In addition in figure 1. which shows color Doppler of mitral inflow the reader can discern flow into the ventricle corresponding to the E and A waves (small white and red arrows) followed by the blue green pattern of diastolic M.R. In figure 3 pulsed wave Doppler shows the diastolic regurgitant flow below the baseline after the non-conducted p wave. The velocity is of course low at about 1 meter/sec. consistent with the low pressure difference between the left ventricle and atrium in diastole.
Diastolic mitral regurgitation is a well-recognized observation in Echocardiography seen in patients with A-V block especially in conditions of elevated Left ventricular filling pressures due to any cause. The explanation is: normally after atrial contraction and relaxation ventricular contraction occurs that closes the mitral and tricuspid valves preventing regurgitation into the atria. In the presence of a delay in ventricular contraction (as in AV block 1st degree) or absence of such (non-conducted p in 2nd degree AV block) the rise in ventricular pressure may exceed the atrial pressure and blood may flow back into the atria while the atrio-ventricular valves are not firmly closed but have “floated” to an almost closed position. The regurgitant volume is usually small and of no hemodynamic significance and resolves when the conduction disturbance is corrected.
Particular instances where it is of more significance include:
Patients with reduced ejection fraction and prolonged P-R interval. This is why when cardiac resynchronization therapy is performed a short P-R interval is set to allow optimal ventricular filling and abolish diastolic regurgitation. It follows that this may phenomenon may be seen in other conditions with impaired ventricular filling such as restrictive cardiomyopathy and constrictive pericarditis.
In the setting of aortic regurgitation (usually acute), the finding of diastolic mitral regurgitation is a sign of severity denoting blood being driven into the left atrium by the regurgitating jet and may be noted even in the absence of AV block.
1. Yoram Agmon, William K. Freeman, Jae K. Oh and James B. Seward Diastolic mitral regurgitation: Circulation. 1999; 99:e13
2. Santi Raffa, Concetta Zito, Smeralda Oliva, Maria Pia Calabro`, Salvatore La Carrubba, Scipione Carerj, Diastolic mitral and tricuspid regurgitation. ECHOCARDIOGRAPHY, Volume 23, number 3, March 2006 , p.251
Special thanks to Dr. Khalil Jalkh, cardilogy fellow at the American University of Beirut for his help with the graphics.