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OBJECTIVES Little is known about coronary sinus lead performance in patients with cardiac resynchronization therapy devices. We evaluated the impact of clinical and technical parameters on coronary sinus lead performance over long-term follow-up. METHODS From February 1999 to July 2004, 235 patients (181 men; mean age, 68 +/- 9 years; mean left ventricular ejection fraction, 26.5 +/- 6.5%; idiopathic dilated cardiomyopathy, 49%; ischemic, 48%; and other cause, 3%) underwent cardiac resynchronization therapy (pacemaker or defibrillator) implantation. RESULTS On implantation, the only statistically significant difference was observed in mean pacing impedance, which was lower for unipolar leads than for bipolar leads (763 +/- 250 vs. 847 +/- 270 Omega, P = 0.02), and lower in patients with ischemic cardiomyopathy than in those with idiopathic cardiomyopathy (758 +/- 204 vs. 837 +/- 291 Omega, P = 0.03). After a mean follow-up of 41.7 +/- 14.7 months, a significant decrease was observed in mean pacing impedance (from 811 +/- 261 to 717 +/- 284 Omega, P = 0.0026) and mean R-wave amplitude (from 13.2 +/- 6.7 to 10.5 +/- 5.5 mV, P = 0.002), whereas the mean pacing energy threshold increased from 3.6 +/- 10.4 to 9.5 +/- 28 microJ (P = 0.004). On analysis of variance, unipolar lead (P = 0.016) and posterior coronary sinus position (P = 0.049) were related to a greater energy threshold increase. On multivariate analysis (Cox regression), only posterior coronary sinus lead position (P = 0.013) proved to be an independent predictor of long-term significant increase in the stimulation energy threshold. CONCLUSION Over the long-term follow-up of coronary sinus leads, pacing impedance and R-wave amplitude decreased, whereas the energy threshold increased; unipolar leads and posterior lead location in the coronary sinus were related to a greater energy threshold increase.

There is little information on any seasonal variations or meteorological factors associated with symptomatic bradyarrhythmias requiring cardiac pacing. The aim of this single-center study was to investigate the seasonal distribution of the incidence of severe, life-threatening bradyarrhythmias requiring urgent temporary transvenous cardiac pacing in an elderly population. Consecutive patients who underwent urgent temporary transvenous cardiac pacing between 2007 and 2012 were enrolled. The baseline characteristics of the patients and some meteorological parameters, including the calculation the daily heat index (HI), were recorded. During the study period, 79 consecutive patients (mean age 82 ± 8 years, 41% male) underwent urgent temporary transvenous cardiac pacing, mainly for third-degree atrioventricular block (79%). The incidence of bradyarrhythmias was significantly higher in summer than in the other seasons (P 0.001). Moreover, the highest incidence was observed in months with HI 90 °F for3 h per day for at least 10 days (P 0.001). A direct correlation was found between the average monthly temperature and the monthly number of patients undergoing temporary cardiac pacing (r = 0.54, P 0.001). Compared with other patients, those observed during the hottest months were significantly older and more frequently affected by chronic disabling neurological diseases (all P 0.05). In addition, they more frequently showed biochemical indices of dehydration, renal function impairment and hyperkalemia (all P 0.05). This study showed an increased incidence of severe bradyarrhythmias in an elderly population during the hottest months of the year. In these months, in subjects characterized by increased susceptibility to dehydration, the risk of developing bradyarrhythmias was increased significantly.