Relationship between Amplitude and Timing of Heart Sounds and Endocardial Acceleration

Objective: To study the correlation between heart sounds and peak endocardial acceleration (PEA) amplitudes and timings, by modulation of paced atrioventricular (AV) delay in recipients of dual chamber pacemakers.
Methods: Ten recipients of dual chamber pacemakers implanted for high-degree AV block were studied. Endocardial acceleration (EA) and phonocardiographic and electrocardiographic signals were recorded during performance of an AV delay scan in VDD and DDD modes.
Results: First PEA (PEA I) and first heart sound (S1) changed similarly with the AV delay. A close intrapatient correlation was observed between S1 and PEA I amplitudes in all patients (P < 0.0001). The interpatient normalized PEA I to S1 amplitudes correlation was r = 0.89 (P < 0.0001) in DDD mode, and r = 0.81 (P < 0.0001) in VDD mode. The mean cycle-by-cycle PEA I to S1 delay was −4.3 ± 22 ms and second PEA (PEA II) to second heart sound (S2) delay was −7.7 ± 15 ms.
Conclusions: A close correlation was observed between PEA I and S1 amplitudes and timings, and between PEA II and S2 timings. These observations support the hypothesis that PEA and heart sounds are manifestations of the same phenomena. EA might be a useful tool to monitor cardiac function.     

Atrioventricular Interval Optimization in the Right Atrial Appendage and Interatrial Septum Pacing: A Comparison Between Echo and Peak Endocardial Acceleration Measurements

PADELETTI, et al. : Atrioventricular Interval Optimization in the Right Atrial Appendage and Interatrial Septum Pacing: A Comparison Between ECHC and Peak Endocardial Acceleration. Interatrial septum pacing (IASP) reduces interatrial conduction time and consequently may interfere with atrioventricular delay (AVD) optimization. We studied 14 patients with an implanted BEST Living system device able to measure peak endocardial acceleration (PEA) signal. The aims of our study were to compare the (1) optimal AVD (OAVD) in right atrial appendage pacing (RAAP) and IASP, and (2) OAVD derived by the PEA signal versus OAVD derived by Echo/Doppler evaluation of the left ventricular filling time (LVFT) and cardiac output (CO). Measurements were performed in DDD VDD modes Eight patients (group A) had RAAP and six patients (group B) had IASP. In group A, OAVD measured by LVFT, CO, and PEA was 185 ± 23 ms , 177 ± 19 ms , and 192 ± 23 ms in DDD and 147 ± 19 ms , 135 ± 27 ms , and 146 ± 20 ms in VDD, respectively. OAVD measured by LVFT, CO, and PEA was significantly longer in DDD mode than in VDD (P < 0.01, P < 0.01, P < 0.001 ). In group B, OAVD measured by LVFT, CO, and PEA was 116 ± 19 ms , 113 ± 10 ms , and 130 ± 30ms in DDD and 106 ± 16 ms , 96 ± 15 ms , and 108 ± 26 ms in VDD, respectively. No statistical differences were observed between DDD and VDD. Significant correlations between OAVDs PEA derived and OAVDs LVFT and CO derived were observed (r = 0.71, r = 0.69, respectively ). When new techniques of atrial stimulation, as IASP, are used an OAVD shorter and similar in VDD and DDD has to be considered. The BEST Living system could provide a valid method to ensure, in every moment, the exact required OAVD to maximize atrial contribution to CO.     

Effects of a combination of napping and bright light pulses on shift workers' sleepiness at the wheel: a pilot study

To assess the effects of napping + bright light on shift work drivers sleepiness at the wheel, we performed a pilot study on nine shift workers on three shifts (morning, afternoon, night), driving on a private road circuit. Sleepiness at the wheel was measured by ambulatory polysomnography and assessed using 30‐s segments of recordings with a percentage of theta electroencephalogram of at least 50% (15 s) of the period recorded. Sleepiness was also assessed by the Stanford Sleepiness Scale (SSS). Participants drove the same car on two similar 24‐h periods of work, with three drivers in each shift (morning, afternoon, night), separated by 3 weeks. During the baseline period, the subjects were told to manage their rest as usual. During the second experimental period, they had to rest lying in a dark room with two naps of 20 min and then exposed to bright light (5000 lux) for 10 min. Subjects showed a significantly decreased sleepiness at the wheel with an average of 10.7 ± 6.7 episodes of theta sleep during the baseline (766 ± 425 s) versus 1.0 ± 1.0 episode lasting 166 ± 96 s during the second period (P = 0.016; P = 0.0109). The percentage of driving asleep was also significantly reduced (3.7% ± 1.9% versus 0.9% ± 0.6%, P = 0.0077). The average SSS score in the group decreased from 2.76 ± 1.27 to 2.28 ± 0.74 (P = 0.09). In this pilot and preliminary study, a combination of napping and bright light pulses was powerful in decreasing sleepiness at the wheel of shift work drivers.     

Polymorphous Ventricular Tachyarrhythmias in the Absence of Structural Heart Disease

Polymorphous ventricular tachyarrhythmias (PVTA) in the absence of structural heart disease form a particularly important target for comprehensive research. They occur in young, healthy children and young adults and most probably cover several underlying electrophysiological abnormalities. We individualized two syndromes, namely catecholaminergic ventricular tachyarrhythmias, and torsade de pointes (TDP) with a short coupling interval, but these two entities certainly represent only a part of the problem of id-iopathic ventricular fibrillation. Having the implanted defibrillator as a therapeutic umbrella for those patients who were fortunate enough to escape from sudden death is not sufficient. Too often in modern cardiology the therapeutic achievements tend to precede the process of diagnosis and comprehension. At least, the former should not preclude the latter, a situation that can be observed, for instance, when the favorable effect of a drug is evidenced before its mode of action was understood. At best, both progress together, provided we pay attention to adequately exploit the resources of modern technology.