Mechanisms, features, and significance of diastolic mitral regurgitation: a case series

Abstract

Background: Diastolic mitral regurgitation (DMR) is a type of functional mitral regurgitation. Its occurrence in the diastolic phase of cardiac cycle renders DMR an easily ignored entity. Confusing it with systolic mitral regurgitation occasionally happens. The reversal of left atrioventricular pressure gradient during diastole and the incomplete closure of mitral valve are the essential conditions for DMR. Diastolic mitral regurgitation develops under various situations, where the mechanisms of diastolic reversal of left atrioventricular pressure gradient differ.

Case summary: Patient 1 was a 50-year-old man diagnosed with 2:1 second-degree atrioventricular block (AVB). Patient 2 was a 70-year-old man diagnosed with first-degree AVB. Patient 3 was a 66-year-old man diagnosed with atrial fibrillation with long intermission and occasional atrial flutter with unequal conduction. Patient 4 was a 54-year-old woman diagnosed with dilated cardiomyopathy with complete left bundle branch block. Patient 5 was a 36-year-old man diagnosed with severe acute aortic regurgitation secondary to subacute bacterial endocarditis.

Discussion: Although the degree of DMR is relatively mild, its appearance generally prompts further clinical considerations. The appreciation of DMR has an incremental value for diagnosing and evaluating the underlying cardiovascular disease.

Keywords: Case series; Diastolic mitral regurgitation; Functional mitral regurgitation; Mechanisms.

Figure 1

P-waves with 2:1 relation with QRS complexes are displayed on the electrocardiogram. Transthoracic echocardiography: (A) PW Doppler of transmitral flow from the apical four-chamber view. After left ventricular systole, the spectrum demonstrates normal early diastolic filling E wave and left atrium contractive A wave. After the blocked sinus P-wave (solid blue arrow), diastolic mitral regurgitation (solid white arrow) appears immediately until next left atrium contraction matching the conducted sinus P-wave (hollow blue arrow). The flow velocity of diastolic mitral regurgitation is about 1.1 m/s (far lower than common systolic mitral regurgitation and slightly higher than A wave) and gradually diminishes. (B) Colour M-mode of transmitral flow from the apical four-chamber view. Diastolic mitral regurgitation presents between the two mitral valve forward flows driven by left atrium contraction (solid white arrow).

Figure 2

P-R interval significantly prolongs over 300 ms on the electrocardiogram. Transthoracic echocardiography: (A) PW Doppler of transmitral flow from the apical four-chamber view. After left atrium systole, left ventricular contraction delays and diastolic mitral regurgitation appears with low velocity (solid white arrow) followed immediately by high velocity systolic mitral regurgitation (asterisk). (B) Colour flow Doppler still frame of transmitral flow from the apical three-chamber view. Mild diastolic mitral regurgitation jet (solid white arrow) presents after the sinus P-wave (solid blue arrow on electrocardiogram tracing).

Figure 3

(A) Atrial flutter with variable conduction on the electrocardiogram. Transthoracic echocardiography: PW Doppler of transmitral flow from the apical four-chamber view. During a 4:1 conduction, the third blocked F-wave (solid blue arrow) drives left atrium contraction accompanied by mitral valve forward flow (hollow white arrow), which is then followed by diastolic mitral regurgitation (solid white arrow) in late diastole. (B) Atrial fibrillation with a 1.5 s interval on the electrocardiogram. Transthoracic echocardiography: Multiple mitral valve forward flows (hollow white arrows) are followed closely by diastolic mitral regurgitations (solid white arrows), respectively until next left ventricular contraction. For the diastolic mitral regurgitation in both situations, the flow velocity is slightly higher than previous mitral valve forward flow.

Figure 4

Transthoracic echocardiography: (A) Colour flow Doppler still frame demonstrates diastolic mitral regurgitation jet (solid white arrow) from the apical four-chamber view after T-wave (solid blue arrow on electrocardiogram tracing). (B) PW Doppler of transmitral flow dictates two mitral regurgitation spectrums at different time of the cardiac cycle, where diastolic mitral regurgitation (solid white arrow) and systolic mitral regurgitation (asterisk) both exist. Transmitral valve forward flow signal only appears in late diastolic phase (hollow white arrow). A special ‘blank period’ existing between the two mitral regurgitation spectrums (double-headed arrow) may be due to dyssynchronous and paradoxical left ventricular movement among segments.

Figure 5

Transoesophageal echocardiography: (A) Midoesophageal short axis view of the aortic valve demonstrates the morphology of bicuspid aortic valve with minor thickening (arrow). (B) Midoesophageal long axis view reveals vegetations and prolapse of aortic valve (arrow). (C) Colour flow Doppler still frame demonstrates severe aortic regurgitation jet and diastolic mitral regurgitation jet (solid white arrow), and the presystolic closure of the mitral valve (hollow white arrow) before P-wave (solid blue arrow on electrocardiogram tracing). (D) PW Doppler of transmitral flow dictates two mitral regurgitation spectrums at different time of the cardiac cycle, diastolic mitral regurgitation (solid white arrow), and systolic mitral regurgitation (asterisk), and no obvious late diastolic forward flow by left atrium contraction (hollow white arrow). AO, aorta; AR, aortic regurgitation; LA, left atrium; LV, left ventricle; MV, mitral valve; RA, right atrium; RV, right ventricle.