Assessment of pulmonary venous flow velocity by pulsed Doppler echocardiography can also be of value in estimating the severity of mitral regurgitation. Normal pulmonary venous flow velocity is biphasic, with a predominant systolic forward velocity and a lesser diastolic forward velocity in older adults. Systolic forward velocity is reduced in patients with mitral regurgitation, and often the diastolic velocity predominates. In severe mitral regurgitation, the systolic flow in the pulmonary vein signal may reverse. Systolic flow reversal is highly specific for severe regurgitation but sensitivity is low. Unfortunately, pulmonary venous flow velocity patterns vary considerably in patients with mitral regurgitation, and the predictive value for regurgitation severity is low. In many laboratories, all these factors are integrated to produce a composite estimate of the severity of regurgitation, usually on a scale of 1 to 4, with 4 being severe mitral regurgitation. Table below exhibits the criteria for grading the severity of mitral regurgitation.
Current Diagnosis & Treatment Cardiology 3rd Edition (McGraw-Hill) 2009