Acute mitral regurgitation is a medical emergency that requires prompt, accurate diagnosis and urgent therapy. Although the use of echo Doppler imaging has been described in these patients, preliminary observations have suggested that color flow Doppler performed from the standard transthoracic windows may underestimate the severity of mitral insufficiency in this setting. The aim of this study was to compare transesophageal color Doppler quantitation of regurgitation with results obtained from standard transthoracic windows in patients with acute, severe mitral regurgitation. Two-dimensional echocardiography with pulsed, continuous, and color flow Doppler was performed by both transthoracic and transesophageal methods in 16 consecutive patients who were documented to have acute severe mitral insufficiency by catheterization. Transthoracic and transesophageal scans were reviewed by two blinded observers and assessed for the detection of mitral regurgitation by transthoracic pulsed wave (81%), continuous wave (100%), and color flow Doppler (81%) compared with transesophageal color flow imaging (100%; p = NS). Severity of mitral regurgitation was graded as none, mild, moderate, or severe on the basis of existing transthoracic pulsed wave and color flow criteria and compared with transesophageal color flow grading. At first examination patients were critically ill, with elevated pulmonary wedge pressures (mean 27 +/- 7 mm Hg) and V waves (mean 45 +/- 10 mm Hg). Fifteen of the patients underwent emergency surgery, and the overall hospital mortality rate was 12%. Maximal color flow jet areas were significantly greater on transesophageal scanning (mean 10.5 cm2) compared with transthoracic color jets (mean 2.3 cm2).(ABSTRACT TRUNCATED AT 250 WORDS)