This article was written in collaboration with Dr. Mustafa Ahmed, Associate Professor of Medicine, Director of the Structural and Interventional Cardiology Program at the University of Alabama, at Birmingham.
CHRONIC MITRAL INSUFFICIENCY:
In this report, we would like to concentrate on the primary mitral insufficiency which is a disease of the mitral valve apparatus (mitral leaflet, chordae tendineae, papillary muscle, mitral annulus), and not the secondary cause which is a disease of the left ventricle and/or the left atrium. The most common cause in the US is mitral valve prolapse.
The severity of the valve insufficiency is based on several criteria that include symptoms, valve anatomy, hemodynamics, and the effect of the insufficiency on ventricular and pulmonary vasculature function. The criteria for severe valve regurgitation are based on predictors of clinical outcomes obtained from clinical trials and registries. Severity is a continuous variable and may manifest itself in different ways for different patients. The onset of symptoms represents an indication of valve repair. However, because the hemodynamic changes can occur over a long period of time, symptoms of shortness of breath or decreased exercise tolerance can be missed or ignored by the patients. Exercise testing or biomarkers (BNP or NT-proBNP) can be helpful in determining the severity of the valve lesion.
Echocardiographic images provide the ideal non-invasive testing to study mitral valve pathology, the severity of the lesion, and its impact on the left ventricle. Because the leaky mitral valve empties into a low-pressure chamber (left atrium), the EF appears better than normal and an EF of >70% is considered normal. When the extra volume load starts affecting the LV function, the EF starts declining toward 60% and the LV can no longer contract to an end-systolic diameter of <40 mm. The Doppler evaluation of the severity of the regurgitation should integrate all the variables documented by the examination: Color jet area (how far back it reaches into the LA), vena contracta (>0.7 cm), effective regurgitant orifice area (EROA >0.4 cm2), regurgitant volume (>60 mL) and a regurgitant fraction (>50%). In mitral valve prolapse, the regurgitant jet may not be holosystolic and the maximal doppler regurgitant jet may overestimate the severity of the lesion. Volumetric calculation of regurgitant volume may be more accurate in those circumstances particularly if 3D data is analyzed either from Echocardiography or magnetic resonance.
Transesophageal echocardiography using 3D imaging allows for visualization of abnormal mitral valve leaflets providing a “surgical view” of the valve and offering a better understanding of the anatomy and estimation of the likelihood of surgical repair. Decision-making can be challenging in an asymptomatic patient and requires the involvement of the Heart Team approach. Consideration should be given to referring patients to a Comprehensive Heart Valve Center where the operative morbidity and mortality are very low and where a durable surgical outcome is very high.