There are various ways to assess the severity of mitral regurgitation by color Doppler echocardiography. One method is to measure the mitral regurgitation jet area in the apical four chamber view and compare it with the area of the left atrium. The ratio of the maximum mitral regurgitation jet area by color Doppler to the area of the left atrium is calculated.
The grading of severity of mitral regurgitation by color Doppler is as follows:
Grade 1 (mild): Mitral regurgitation jet area / left atrium area ratio <20%
Grade 2 (moderate): Mitral regurgitation jet area / left atrium area ratio 20 – 40%
Grade 3 (severe): Mitral regurgitation jet area / left atrium area ratio >40%
When the left atrium is grossly dilated, the ratio may be erroneously low even in severe mitral regurgitation and this is a limitation of this method.
Another method is by looking at the extend of the jet into the left atrium. A jet reaching upto the pulmonary veins is graded as severe.