Evaluation of the reproducibility and accuracy of apex beat measurement in the detection of echocardiographic left ventricular dilation.
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OBJECTIVE: To develop a standardized method for measuring the width of the apex beat and to determine its precision and accuracy in detecting echocardiographically determined left ventricular dilation. DESIGN: In the reproducibility study, two cardiologists blinded to each other's findings measured the apex beat. To determine accuracy, blind, independent assessment of apex beat measurement was compared with left ventricular enlargement determined by echocardiogram. PATIENTS: One hundred and four patients referred for echocardiogram for a wide variety of suspected cardiac abnormalities. MEASUREMENTS: The apex beat was measured with patients in a 45 degrees left lateral decubitus position; medial and lateral aspects of the impulse and the width were identified using electrocardiographic callipers. Echocardiographic left ventricular dilation was defined as a measure exceeding the 95% prediction limits as determined for the patient's age and body surface area. RESULTS: The intraclass correlation measuring agreement on apex beat size between two cardiologists in 13 patients was 0.95. Of the 104 patients, 57 had a measurable apex beat of whom 50 had a technically adequate echocardiogram. The sensitivity of the measurement, using a cut-point of 40 mm, was 0.48 and the specificity 0.96.
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