Diastolic Mitral Regurgitation in Complete Atrioventricular Block

Case report

A 75-year-old woman was admitted to our hospital with progressive dyspnea and fever due to an acute, community-acquired pneumonia. On examination, the heart rate was irregular and slow (43 beats per minute), and there was a soft end-diastolic and a somewhat louder systolic murmur over the apex. The 12-lead surface electrocardiogram confirmed the diagnosis of a third-degree atrioventricular (AV) block, most likely due to a pneumonia-associated myocarditis. The transthoracic echocardiogram revealed the presence of a significant diastolic mitral regurgitation (MR) as the reason for the diastolic murmur (Figure 1). The timing of diastolic MR was best demonstrated by continuous-wave Doppler recordings (Figure 2) and colour-Doppler M–mode (Figure 3, left side). During the M-mode acquisition, the patient switched back to SR, and the diastolic MR disappeared (Figure 3, right side).

Diastolic MR is caused by an elevated left ventricular end-diastolic pressure, leading to an inverse pressure gradient across the mitral valve in diastole, and hence to a diastolic MR with a relatively low velocity of 1–2 m/s [1,2]. This condition is frequently met during atrio- ventricular conduction abnormalities of any degree [1], after ventricular premature beats or in patients with a pacemaker and a prolonged PQ interval [3], during atrial flutter, in patients with restrictive cardiomyopathy [4], and in patients with severe aortic regurgitation [2]. The present case illustrates diastolic MR during complete atrioventricular block and emphasises the diagnostic accuracy of continuous-wave Doppler and colour-Doppler M-mode echocardiography.