Abstract
BACKGROUND: Recently, a cutaneous force-frequency relation recording system based on first heart sound amplitude vibrations has been validated. A further application is the assessment of Second Heart Sound (S2) amplitude variations at increasing heart rates. The aim of this study was to assess the relationship between second heart sound amplitude variations at increasing heart rates and hemodynamic changes. METHODS: The transcutaneous force sensor was positioned in the precordial region in 146 consecutive patients referred for exercise (n = 99), dipyridamole (n = 41), or pacing stress (n = 6). The curve of S2 peak amplitude variation as a function of heart rate was computed as the increment with respect to the resting value. RESULTS: A consistent S2 signal was obtained in all patients. Baseline S2 was 7.2 +/- 3.3 mg, increasing to 12.7 +/- 7.7 mg at peak stress. S2 percentage increase was + 133 +/- 104% in the 99 exercise, + 2 +/- 22% in the 41 dipyridamole, and + 31 +/- 27% in the 6 pacing patients (p < 0.05). Significant determinants of S2 amplitude were blood pressure, heart rate, and cardiac index with best correlation (R = .57) for mean pressure. CONCLUSION: S2 recording quantitatively documents systemic pressure changes.