740-5 A New Intracavitary Cathether for Monitoring Contractility Through Endocardially Recorded First Heart Sound: Initial Clinical Validation

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Theoretical and experimental evidences have shown how changes in myocardial performance are mirrored in changes of first heart sound acceleration amplitude, which is generally 10 to 100 times more powerful with endecavitary than with chest wall recordings. Aim of the study was to evaluate the clinical feasibility and tolerability of intracavitary sampling of first heart sound via an implantable tip mounted accelerometer in man. We developed an unidirectional acceleration sensor (Sorin Biomedica) located inside the stimulating tip of a standard unipolar pacing lead: it has a frequency response up to 1 KHz and a sensitivity of 5 mV/G (G = 9.8 m/sec 2 ). The lead was connected to an external signal amplifier with a frequency range of 0.05–1,000 Hz and to a peak to peak detector synchronised with the endocardial R-wave scanning the isovolumetric contraction phase. Following standard electrophysiologic studies, sensor equipped leads were temporarily inserted in the right ventricle of 15 patients (61 ± 7 years), with normal regional and global ventricular function, to record peak endocardial acceleration (PEA) of first heart sound frequencies at rest, during AAI pacing, VVI pacing and during dobutamine infusion (up to 20 mcg/kg/min). PEA at baseline was 1.2 ± 0.6 G (heart rate = 68 ± 13 b.p.m.1 and increased to 1.5 ± 0.9 (p = ns vs baselinel during AAI pacing (heart rate = 140 b.p.m.) and to 1.4 ± 0.7 (p = ns vs baseline) during VVI pacing (heart rate = 140 b.p.m.). Dobutamine infusion increased PEA to 5.4 ± 2.1 (p < 0.001 vs baseline). with a heart rate = 120 ± 11 b.p.m. In conclusion, high quality first heart sound recording can be consistently and safely obtained with an implantable device. Pharmacologic inotropic stimulation, but not isolated chronotropic stimulation, increase the strength of the signal, in keeping with the experimental studies suggesting that PEA is an index of myocardial contractility. The clinical applicability of the method via right heart catheterization and implantable device offers potential for new diagnostic applications.