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Relationship between mitral regurgitation and left ventricular outflow obstruction in hypertrophic cardiomyopathy
I Hasegawa1, T Sakamoto, Y Hada
1Second Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
Insights
Midsystolic mitral regurgitation in hypertrophic cardiomyopathy is linked to left ventricular outflow obstruction. This regurgitation is hydrodynamically induced by anterior mitral leaflet protrusion into the outflow tract.
Area of Science:
- Cardiology
- Medical Imaging
- Physiology
Background:
- Hypertrophic cardiomyopathy (HCM) can cause left ventricular outflow tract (LVOT) obstruction.
- The relationship between mitral regurgitation (MR) and LVOT obstruction in HCM is not fully understood.
Purpose of the Study:
- To investigate the association between mitral regurgitation and left ventricular outflow obstruction in patients with hypertrophic cardiomyopathy.
- To elucidate the mechanism of midsystolic mitral regurgitation in HCM.
Main Methods:
- Doppler and two-dimensional echocardiography were performed in 62 patients with HCM.
- Pulsed Doppler with color flow imaging assessed mitral regurgitation.
- Two-dimensional echocardiography evaluated mitral leaflet motion and septal contact.
Main Results:
- Midsystolic mitral regurgitation was observed in 20/22 patients with LVOT obstruction, correlating with mitral-septal contact.
- This specific MR pattern was absent in patients without obstruction.
- Mitral regurgitation dynamics mirrored obstruction changes during follow-up and interventions.
- Anterior mitral leaflet protrusion into the LVOT was identified as the cause of obstruction and MR.
Conclusions:
- Midsystolic mitral regurgitation in HCM is often secondary to LVOT obstruction.
- The obstruction is caused by anterior mitral leaflet prolapse into the outflow tract.
- This regurgitation is likely hydrodynamically induced by the pressure gradient across the protruding leaflet.
Abstract:
To clarify the relationship between mitral regurgitation and left ventricular outflow obstruction, Doppler and two-dimensional echocardiographic studies were performed in 62 patients with hypertrophic cardiomyopathy (22 with and 40 without obstruction caused by mitral systolic anterior motion with septal contact). Pulsed Doppler echocardiography with color Doppler flow imaging demostrated that in 20 of the 22 patients with obstruction, mitral regurgitation occurred mainly during midsystole from the onset to the end of mitral-septal contact. Such midsystolic mitral regurgitation was not observed in patients without obstruction, except in three of 25 patients with mild mitral systolic anterior motion without septal contact. Furthermore, that regurgitation developed or disappeared together with the obstruction during follow-up periods or pharmacologic interventions. Two-dimensional echocardiography showed that in 21 of the 22 patients with obstruction, a distal residual portion of the "anterior" mitral leaflet moved anteriorly in early systole and protruded into the outflow tract during midsystole to cause the obstruction. In the other patient with obstruction, who had only early systolic mitral regurgitation, a distal residual "posterior" leaflet moved similary. These results may indicate that the midsystolic mitral regurgitation is hydrodynamically induced by the midsystolic pressure gradient across the protruding distal residual anterior mitral leaflet.