Echocardiography is the key diagnostic tool in determining the functional type and severity of mitral regurgitation. It also determines left ventricular segmental wall motion and function. The severity of regurgitation can be assessed by semi-quantitative measurements using jet geometry and area in multiple views. The severity of mitral regurgitation is graded on a scale from 1+ to 4+ (1 + trace, 2+ mild, 3+ moderate and 4+ severe mitral regurgitation with flow reversal in the pulmonary veins). On Doppler echocardiography, the direction of the regurgitant jet provides important information with regard to the functional type of mitral regurgitation. During the last decade, quantitative Doppler methods have been applied with an increasing frequency to grade the severity of mitral regurgitation. This quantitative grading is based on the calculation of regurgitant volume (the difference between the mitral and aortic stroke volumes) and effective regurgitant orifice (ratio of regurgitant volume to regurgitant time velocity integral).
Intraoperative transesophageal echocardiography (TEE) can also be used to determine the mechanism of regurgitation. Several studies, however, have shown that TEE downgrades the severity of mitral regurgitation in patients with Type I or IIIb dysfunction. This physiologic phenomenon is explained by the unloading effect of general anesthesia, which results in arterial and venous vaso-dilatation, reducing afterload and preload respectively.
Type I mitral regurgitation-Normal leaflet motion
Type I dysfunction results from annular dilatation with a central jet on Doppler echocardiography. It is observed in patients with basal myocardial infarction.
Type II mitral regurgitation-Excess leaflet motion
Type II dysfunction is commonly due to papillary muscle rupture. The direction of the jet is opposite to the prolapsing segment. In the setting of complete papillary rupture with bileaflet prolapse, the jet is central and very wide. The ruptured segment of the muscle can often be directly viewed on echocardiography as a mobile ventricular mass that occasionally protrudes into the atrium. Initially, the heart is very hyperdynamic and the left ventricular systolic function is preserved in most instances due to the limited size of myocardial infarction.
Type IIIb mitral regurgitation-Systolic restricted leaflet motion
In patients with posterolateral myocardial infarction and restricted leaflet motion involving mostly the posterior leaflet, the jet is directed over the restricted p2-p3 segments. The jet could be central if there is significant annular dilatation. In patients with anteroseptal myocardial infarction and globular remodeling of the heart, both leaflets are commonly tethered and the jet is central. The coaptation depth, which is defined by the distance between the annular plane and the plane of coaptation, is particularly increased in these patients. Other important echocardiographic data are the evaluation of the tenting height, and area which also reflects the severity of leaflet tethering and of left ventricular function and size.
Careful assessment of these echocardiographic variables is critical as they are predictors of long-term durability of valve reconstruction.
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