Transthoracic DC Shock May Represent a Serious Hazard in Pacemaker Dependent Patients

External defibrillation is widely used for the termination of various atrial and ventricular tachyarrhythmias, including pacemaker patients. Our study was intended to evaluate the effects of DC shocks in 36 patients with unipolar pacemakers implanted in the right pectoral region (25 DDD, 10 VVI, 3 AAI). The shocks were delivered with paddles on the anterior surface of the thorax, as far as possible away from the pacemaker. The pacing output was programmed at 0.5 msec and 5 V (25 patients), 4 V (1 patient), and 2.5 V (10 patients). Transient loss of capture occurred in 18 patients (50%). These patients, compared with those without capture failure, received higher peak and cumulative shock energies, respectively, 216 ± 99 versus 123 ± 50 joules (P < 0.002) and 352 ± 62 versus 147 ± 98 joules (P < 0.004) and had a lower pacemaker pulse amplitude (4.0 ± 1.2 vs 4.6 ± 1.0 V, P = 0.11). Failure to capture lasted from 5 seconds to 30 minutes (mean 157 sec). In 15 patients the ventricular stimulation threshold was measured before and serially after cardioversion. A six-fold threshold increase was observed 3 minutes after the shock (P < 0.004) with gradual recovery to nearly baseline values at 24 hours. Transient sensing failure occurred in 7 of the 17 patients in whom it could be evaluated (41%). Furthermore, three cases of shock induced pacemaker malfunctions were observed requiring replacement of the stimulator in two patients. In conclusion, the incidence of loss of capture in pacemaker patients subjected to electrical cardioversion/defibrillation is high. The phenomenon is due to an abrupt rise in stimulation threshold, caused by the electrical shock, and may represent a serious hazard in pacemaker dependent patients. The risk of pacing failure could be reduced by utilizing low shock energies when possible, and by programming the pacemaker at its maximal output before cardioversion.     

Italian Multicenter Clinical Experience with Endocardial Defibrillation: Acute and Long-Term Results in 307 Patients

This study presents the acute and long-term results of 307 patients (267 men, mean age 57.5 years, 205 suffering from coronary artery disease, mean left ventricular ejection fraction 33.3%) with malignant ventricular tachyarrhythmias who underwent attempted transvenous ICD implantation with the CPI Endotak lead system in 37 Italian centers. Transvenous ICD implantation was ultimately accomplished in 306 (99.7%) patients. These included 19 subjects with high (< 10 J below output energy of implanted device) defibrillation threshold (DFT) at implant. One hundred sixty-four patients (53%) were implanted with the endocardial lead alone, while 142 also received an SQ patch or SQ array. The mean DFT (not always step-down DFT) at implant was 16.9 ± 5.7 joules; 15.3 ± 5.2 joules with biphasic shock and 19.6 ± 5.4 joules with monophasic shock; P < 0.0001. A significantly higher percentage of patients tested with a biphasic shock could be implanted with adequate safety margin and without an additional SQ patch or SQ array (98% and 81 %, respectively). No perioperative deaths occurred. During the mean follow-up of 14.5 ± 10.2 months, 140 patients (52%) received at least one appropriate shock. An inappropriate shock was observed in 26% of episodes. The 1- and 3-year actuarial incidence of sudden death was 2% and 4%, respectively, and that of total death was 10% and 20%, respectively. A pocket infection requiring ICD explantation occurred in 4 patients (1.4%) and an endocardial lead dislodgment in 11 patients (3.6%). Two patients (0.3%) showed a sensing pin disconnection and six patients (2.3%) had a lead insulation break. The results of this Italian multicenter trial indicate that the GPl Endotak lead system is a simple, safe, and reliable system for endocardial defibrillation. When compared to epicardial leads, it clearly reduces the perioperative mortality and morbidity, while maintaining a similar efficacy in preventing sudden death and terminating ventricular arrhythmias.     

Secretory immune response in patients with intestinal amoebiasis

The secretory immune response in saliva from intestinal amoebiasis patients against antigens obtained from Entamoeba histolytica membranes was studied. Western blot analysis indicated that patient saliva contains secretory IgA antibodies against antigens with molecular masses ranging from 170 to 24 kDa, some of which were also recognized by saliva from healthy subjects. However, antigens of 170, 125, 46 and 37 kDa are recognized more frequently (> 90%) by the secretory IgA from patients with intestinal amoebiasis than by that from healthy subjects (< 10%).     

Bifocal Right Ventricular Resynchronization for the Failing Right Ventricle

The present case illustrates that in patients with right ventricular (RV) failure and right bundle branch block it is possible to resynchronize the RV without further worsening RV or left ventricular (LV) pump function, even in cases with various degrees of atrioventricular block. The acute response to different pacing configurations was analyzed in terms of dP/dt variations. Bifocal RV pacing (His bundle plus RV outflow tract pacing) achieved the best acute results and was chosen for permanent pacing. This pacing configuration was associated to clinical and echocardiographic improvement. (PACE 2011; 34:e78–e81)