The third(S3) and fourth(S4) heart sounds detected by phonocardiography are considered to represent the criterion standards of the gallop sounds, but their test characteristics have not been explored. Abstract: To determine the diagnostic test characteristics of the S3 and S4 for prediction of left ventricular dysfunction using a computerized heart sound detection algorithm. Design, Setting, and Participants: Prospective study of 90 adult patients undergoing elective left-sided heart catheterization at a single US teaching hospital between August 2003 and June 2004. The mean age was 62(SD, 13) years(range, 24- 90 years) and 61(68% ) were male. Within a 4-hour period, participants underwent computerized heart sound phonocardiographic analysis, cardiac catheterization, transthoracic echocardiography, and blood sampling for assessment of an S3/S4, left ventricular end-diastolic pressure(LVEDP), left ventricular ejection fraction(LVEF), and B-type natriuretic peptide(BNP), respectively. Main Outcome Measures: Diagnostic test characteristics of the computerized phonocardiographic S3 and S4 using markers of left ventricular function as criterion standards. Results: Mean(SD) LVEDP was significantly elevated(18.4[6.9] mm Hg vs 12.1[7.3] mm Hg; P< .001), mean(SD) LVEF was reduced(49.4% [20.2% ] vs 63.6% [14.8% ]; P< .001), and median(interquartile range) BNP was elevated(330[98- 1155] pg/mL vs 86[41- 192] pg/mL; P< .001) in those with an S3, S4, or both compared with patients without a diastolic heart sound. The sensitivities of these heart sounds to detect an elevated LVEDP, reduced LVEF, or elevated BNP were 41% , 52% , and 32% for an S3, and 46% , 43% , and 40% for an S4, respectively. For abnormal levels of the same markers of ventricular function, the specificities of the S3 were 92% , 87% , and 92% , while the specificities of the S4 were 80% , 72% , and 78% , respectively. Conclusions: Neither the phonocardiographic S3 nor the S4 is a sensitive marker of left ventricular dysfunction. The phonocardiographic S3 is specific for left ventricular dysfunction and appears to be superior to the moderate specificity of the phonocardiographic S4. The third (S3) and fourth (S4) heart sounds detected by phonocardiography are considered to represent the criterion standards of the gallop sounds, but their test characteristics have not been explored. Abstract: To determine the diagnostic test characteristics of the S3 and S4 for prediction of left ventricular dysfunction using a computerized heart sound detection algorithm. Design, Setting, and Participants: Prospective study of 90 adult patients undergoing elective left-sided heart catheterization at a single US teaching hospital between August 2003 and June 2004. The mean age was Within a 4-hour period, participants underwent computerized heart sound phonocardiographic analysis, cardiac catheterization, transthoracic echocardiography, and blood sampling for assessment of 62 (SD, 13) years (range, 24-90 years) and 61 of an S3 / S4, left ventricular end-diastolic pressure (LVEDP), left ventricular ejection fraction (LVEF), and B-type natriuretic peptide Results: Mean (SD) LVEDP was significantly elevated (18.4 [6.9] mm Hg vs 12.1 [7.3] mm Hg; P <.001), median (SD) LVEF was reduced (49.4% [20.2%] vs. 63.6% [14.8%]; P <.001), and median (interquartile range) BNP was elevated / mL vs 86 [41-192] pg / mL; P <.001) in those with an S3, S4, or both compared with patients without a diastolic heart sound. The sensitivities of these heart sounds to detect an elevated LVEDP, reduced For LVEF, or elevated BNP were 41%, 52%, and 32% for an S3, and 46%, 43%, and 40% for an S4, respectively. For abnormal levels of the same markers of ventricular function, the specificities of the S3 were 92%, 87%, and 92%, while the specificities of the S4 were 80%, 72%, and 78%, respectively. Conclusions: Neither the phonocardiographic S3 nor the S4 is a sensitive marker of left ventricular dysfunction. The phonocardiographic S3 is specific for left ventricular dysfunction and appears to be superior to the moderate specificity of the phonocardiographic S4.