Effects of cardiac resynchronization therapy on the first heart sound energy

Introduction: The first heart sound (S1) carries information about ventricular function which may be clinically useful in optimization of cardiac resynchronization therapy (CRT). We developed a method of measuring the effects of CRT on S1 energy. Methods: For 10 patients with activation induced heart failure (age 64±8.4 years), the heart sound was recorded synchronously with the three lead ECG. Two recordings were made with the pacemaker turned off and on, respectively. An automated method was used for beat segmentation and alignment, and a median ECG beat was calculated. ECG beats were aligned to the median, and heart sound beats were aligned to the ECG. An envelope of the median heart sound was calculated using the absolute Hilbert transform, and the energy of the Sl envelope in a 0.2s interval was calculated. Statistical analysis was carried out using the Wilcoxon signed-rank test. Results: Activation of the pacemaker resulted in an increase in Sl energy of 419.6±623.4%. This was statistically significant with p<;0.01. Out often cases, the energy increased by >40% in nine and >74% in eight. In the single remaining case there was a -4.5% reduction. Conclusion: CRT causes clinically relevant change in Sl energy, and methods of real-time measurement may be useful in CRT optimization.