Measurement of vegetations in infective endocarditis: An inaccurate method to decide the therapeutical approach

The European Society of Cardiology and American Heart Association guidelines give a central role to the maximal vegetation diameter in the indication for surgery to prevent embolism in left sided infective endocarditis. Vegetation measuring is likely to be inaccurate. The hypothesis herein, is that the vegetation diameter is not an appropriate surgical criterion given the variability of its measurement.

Two trained echocardiographers independently measured the maximal vegetation diameter by transesophageal echocardiogram of 76 vegetations in 67 consecutive patients with definite infective endocarditis in an off-line workstation. The interobserver variability was calculated by the interclass correlation coefficient. The relationship between the strength of agreement for the cut-off points of 10 and 15 mm was also calculated. Finally, the number of patients whose surgical indication would have changed depending on which operator measured the vegetation was evaluated.

Interobserver interclass correlation coefficient in the measurement of the maximal longitudinal diameter of the vegetations was 0.757 (0.642-0.839). The strength of agreement of the interobserver analysis for the cut-off point of 10 mm was 0.533 (0.327-0.759). For the cut-off point of 15 mm it was 0.475 (0.270-0.679). If heart failure or uncontrolled infections had been absent, the surgical indication would have changed in a total of 33 patients (33/76; 43%) depending on which operator measured the vegetation.

The variability in the measurements of the maximal longitudinal diameter by transesophageal echocardiogram is high. Surgical indications based on the cut-off points recommended by the international guidelines should be revised.