Usefulness of acoustic cardiography to resolve ambiguous values of B-type natriuretic Peptide levels in patients with suspected heart failure.

B-type natriuretic peptide (BNP) levels are helpful to diagnose left ventricular (LV) systolic and/or diastolic dysfunction. BNP levels that are only moderately increased have limited diagnostic ability, and an additional test to resolve this problem would be desirable. The hypothesis that acquiring combined electrocardiographic and electronic cardiac acoustical data can improve the detection of LV dysfunction in patients with nondiagnostic values of BNP was tested. Both BNP and combined 12-lead electrocardiograms with electronic heart sound (acoustic cardiographic) recordings were obtained from 164 outpatients referred for echocardiographic evaluation for suspected heart failure. Acoustic cardiographic parameters included the third heart sound (S(3)) and percentage of electromechanical activation time, measured as the interval from onset of the Q wave of the electrocardiogram to the first heart sound (S(1)) and expressed as a proportion of the cardiac cycle. Sixty-nine of 164 patients (42%) had BNP values in the "gray zone" of 100 to 500 pg/ml. Sensitivity and specificity for LV dysfunction of BNP in the gray zone were 55% and 75%, with a positive likelihood ratio of 2.3. The use of acoustic cardiographic parameters in these 69 patients increased sensitivity and specificity to 69% and 100%, with a corresponding positive likelihood ratio of 69. In conclusion, easily obtainable acoustic cardiographic data substantially improved the diagnostic evaluation of patients with nondiagnostic BNP values and therefore can increase the confidence with which physicians diagnose and treat LV dysfunction.