PURPOSE: We sought to determine the importance of a third heart sound (S3) and its relation to hemodynamic and valvular dysfunction. SUBJECTS AND METHODS: We prospectively enrolled 580 patients who had isolated valvular regurgitation (mitral, n = 299; aortic, n = 121) or primary left ventricular dysfunction with or without functional mitral regurgitation (n = 160). We analyzed the associations between the clinical finding of an audible S3 (as noted in routine clinical practice by internal medicine physicians) and hemodynamic alterations measured by comprehensive quantitative Doppler echocardiography. RESULTS: S3 was more prevalent in patients with primary left ventricular dysfunction (46%, n = 73) than in organic mitral (16%, n = 47) or aortic (12%, n = 14) regurgitation (P <0.001). Patients with an S3 were more likely to have class III-IV symptoms (55% [74 of 137] vs. 18% [80 of 443] of those without an S3, P <0.001) and had a higher mean [± SD] pulmonary pressure (55 ± 15 vs. 41 ± 11 mm Hg, P <0.001). An S3 was also related to a higher early filling velocity due to a greater filling volume, restrictive filling, or both. An S3 was a marker of severe regurgitation (regurgitant fraction ≥40%) in patients with primary left ventricular dysfunction (odds ratio [OR] = 2.4; 95% confidence interval [CI]: 1.1 to 5.5), mitral regurgitation (OR = 17; 95% CI: 5.8 to 52), and aortic regurgitation (OR = 7.1; 95% CI: 1.8-28). An S3 was also associated with restrictive filling in primary left ventricular dysfunction (OR = 3.0; 95% CI, 1.6 to 5.9), marked dilatation in mitral regurgitation (OR = 20; 95% CI: 6.8 to 58), and an ejection fraction (<50%) in aortic regurgitation (OR = 19; 95% CI: 6.0 to 62). CONCLUSION: An audible S3 is an important clinical finding, indicating severe hemodynamic alterations, and should lead to a comprehensive assessment and consideration of vigorous medical or surgical treatment.
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