Bileaflet mechanical heart valve closing sounds: in vitro classification by phonocardiographic analysis.

Bileaflet mechanical heart valves, which exhibit hemodynamic performance fairly similar to that of native valves, can be investigated by the analysis of their closing sounds. Signal spectra calculated from the closing sounds are characterized by specific features that are suitable for the functional evaluation of the valves. Five commercial bileaflet mechanical heart valves were studied under different conditions that were simulated in vitro using a Sheffield pulse duplicator for the aortic position. The closing sounds were acquired by means of a phonocardiographic apparatus, analyzed by a specifically implemented algorithm, and were statistically compared. This article was aimed at classifying the investigated valves on the basis of their signal spectra: different profiles were identified, depending on the working conditions; moreover, closing sound reproducibility and intensity allowed the ranking of valve performances with respect to the "noise" produced by valve closure. In particular, results demonstrated which valves were characterized by the lowest noise (i.e., the Medtronic Advantage and St. Jude Regent valves) and which were characterized by the highest reproducibility (OnX, Medtronic Advantage, and St. Jude Regent valves) under the examined experimental conditions.

Application of wavelet analysis to the phonocardiographic signal of mechanical heart valve closing sounds.

Heart valve disorders, caused by congenital defects, rheumatic fever, calcification, myocardial infarction and other cardiovascular diseases, often require native valves to be replaced by bio-prosthetic devices or mechanical heart valves (MHVs). Among MHVs, bileaflet valves are usually preferred for their hemodynamic features, similar to physiological ones, and their durability, but they are prone to complications due to thromboembolic events. Due to the asynchronous closure of the leaflets, bileaflet MHVs are also known to produce closing sounds typically characterized by the presence of two peaks in the time domain. The detection of this "double click" in the signal may be useful for the early diagnosis of bileaflet MHV malfunction. The closing sound is actually a non-stationary signal that can be properly explored by means of time-frequency analysis. This paper describes a preliminary approach to the investigation of bileaflet MHV closing sounds performed by Continuous Wavelet Transform (CWT) analysis. Signals were collected from 3 patients immediately after surgery by means of the Myotis 3C, which is a traditional phonocardiographic apparatus. Signals were analyzed by two algorithms: one embedded in the Myotis 3C, based on the Fast Fourier Transform (FFT); and one specifically created for the purposes of the present study, based on CWT. The performance of these algorithms was compared and the results showed that the proposed CWT technique correctly classifies as ''double'' a large number of clicks that are recognized as ''single'' by the Myotis 3C.

Electrophysiological efficacy of Epicor high-intensity focused ultrasound.

OBJECTIVES: Clinical success of atrial fibrillation (AF) ablation depends on persistent blocking of electrical conduction across the ablation lines. Epicor high-intensity focused ultrasound (HIFU) ablation has been credited with a variable clinical efficacy. The aim of this work is to ascertain the electrophysiological (EP) efficacy of such lesions, by assessing pulmonary vein isolation (PVI) after open chest HIFU ablation, in the clinical setting. METHODS: Ten consecutive mitral patients (mean age: 57±10 years) with paroxysmal AF undergoing concomitant ablation with the Epicor ablation system (St. Jude Inc.®, Minneapolis, MN, USA) were enrolled for EP assessment. During surgery, pairs of additional temporary wires were positioned on the right PVs (RPVs) and on the roof of the left atrium (RLA), before epicardial ablation. Exit block (no capture during PV pacing) of RPV and of RLA was assessed before, after ablating and immediately after closure of the chest, in order to check the correct positioning of the wires. EP assessment was repeated before discharge and at 3 weeks. RESULTS: Baseline RPV pacing threshold (PT) was 3.5±2 mA (range 1.5-8), of RLA 1.73±1.1 mA (range 0.7-4.3 mA). PVI was not reached any time after HIFU ablation. At the pre-discharge EP study, the absence of isolation was observed in all cases. At 3 weeks, the PTs were 6.8±5.8 mA on RPV (range 2-16) and 6.4±5.3 mA (range 1-19) on RLA. All patients were discharged in sinus rhythm. CONCLUSIONS: PVI was not achieved after Epicor HIFU ablations, up to 3 weeks after surgery.