Silent Atrial Fibrillation in Elderly Pacemaker Users: A Randomized Trial Using Home Monitoring.

BACKGROUND: Pacemaker with remote monitoring (PRM) may be useful for silent atrial fibrillation (AF) detection. The aims of this study were to evaluate the incidence of silent AF, the role of PRM, and to determine predictors of silent AF occurrence. METHODS: Three hundred elderly patients with permanent pacemaker (PPM) were randomly assigned to the remote group (RG) or control group (CG). All patients received PPM with remote monitoring capabilities. Primary end point was AF occurrence rate and the secondary end points were time to AF detection and number of days with AF. RESULTS: During the average follow-up of 15.7±7.7 months, AF episodes were detected in 21.6% (RG = 24% vs CG = 19.3%, P = 0.36]. There was no difference in the time to detect the first AF episode. However, the median time to detect AF recurrence in the RG was lower than that in the CG (54 days vs 100 days, P = 0.004). The average number of days with AF was 16.0 and 51.2 in the RG and CG, respectively (P = 0.028). Predictors of silent AF were left atrial diameter (odds ratio [OR] 1.2; 95% CI = 1.1-1.3; P < 0.001) and diastolic dysfunction (OR 4.8; 95% CI = 1.6-14.0; P = 0.005). CONCLUSIONS: The incidence of silent AF is high in elderly patients with pacemaker; left atrial diameter and diastolic dysfunction were predictors of its occurrence. AF monitoring by means of pacemaker is a valuable tool for silent AF detection and continuous remote monitoring allows early AF recurrence detection and reduces the number of days with AF.

Marchantia polymorpha mitochondrial orf identifies transcribed sequence in angiosperm mitochondrial genome.

Heterologous hybridizations performed using nine Marchantia polymorpha mitochondrial orfs and the sdh4 gene against angiosperm mtDNA suggested that three of them and the sdh4 gene have been conserved in the mitochondrial genome of different angiosperm species. Solanum tuberosum mtDNA fragments, which hybridized to M. polymorpha orf207 and sdh4 gene, were cloned, sequenced, and their expressions evaluated by Northern and RT-PCR. Hybridizing fragments to sdh4 gene and orf207 from potato mtDNA were shown to be transcribed, but only in the case of sdh4 gene was there homology between the protein encoded by the DNA sequence from M. polymorpha and the potato mitochondrial genome. M. polymorpha orf207 showed little similarity to an open reading frame from potato mtDNA, named here orf78. The putative proteins encoded by both orf207 and orf78 were not related, indicating that these orfs do not constitute homologous sequences.

Atrioventricular pacemaker. Incidence and causes of reprogramming in long-term follow-up.

OBJECTIVE: To assess the incidence of problems requiring reprogramming of atrioventricular pacemakers in a long-term follow-up, and also the causes for this procedure. METHODS: During the period from May '98 to December '99, 657 patients were retrospectively studied, An actuarial curve for the event reprogramming of the stimulation mode was drawn. RESULTS: The follow-up period ranged from 12 to 178 months (mean = 81 months). Eighty-two (12.4%) patients underwent reprogramming of the stimulation mode as follows: 63 (9.5%) changed to VVI,(R/C); 10 (1.5%) changed to DVI,C; 6 (0.9%) changed to VDD,C; and 3 (0.5%) changed to DOO. The causes for the reprogramming were as follows: arrhythmia conducted by the pacemaker in 39 (37.6%) patients; loss of atrial sensitivity or capture, or both, in 39 (38.6%) patients; and microfracture of atrial electrode in 5 (4.9%) patients. The stimulation mode reprogramming free probability after 15 years was 58%. CONCLUSION: In a long-term follow-up, the atrioventricular pacemaker provided a low incidence of complications, a high probability of permanence in the DDD,C mode, and the most common cause of reprogramming was arrhythmia conducted by the pacemaker.

Probability of occurrence of life-threatening ventricular arrhythmias in Chagas' disease versus non-Chagas' disease.

The implantable cardioverter defibrillator (ICD) is highly effective in the treatment of ventricular arrhythmias (VA) responsible for sudden cardiac death. However, the probability of occurrence of these arrhythmic events in presence of cardiomyopathy remains uncertain. The aim of this study was to compare the probability of nonoccurrence of life-threatening VA in ICD recipients with Chagas' versus non-Chagas' heart disease. Over a mean follow-up of 10.5 months, 53 ICD recipients (mean age = 50.1 years, 48 male) were evaluated. Eleven patients had Chagas' heart disease, 19 had idiopathic dilated cardiomyopathy and 23 had ischemic cardiomyopathy. Ventricular tachyarrhythmias with a cycle length < 315 ms were considered life-threatening. The cumulative probability of nonoccurrence of life-threatening VA was examined by Kaplan-Meyer method and the outcomes were submitted to the log rank test. At 2 years, the cumulative probability of life-threatening VA nonoccurrence was 0 in the Chagas' heart disease group versus 40% up to 55 months of follow-up in the non-Chagas' disease group (P = 0.0097). Among patients with cardiomyopathies of different etiologies, those with Chagas' heart disease had the lowest cumulative probability of nonoccurrence of life-threatening VA, confirming its unfavorable prognosis and the importance of preventive measures against sudden death in this disease.

Neurohumoral behavior in recipients of cardiac pacemakers controlled by a closed-loop autonomic nervous system-driven sensor.

The purpose of a sensor-driven pacing system is to physiologically correct chronotropic incompetence (CI). The aim of this study was to evaluate the changes in heart rate provided by a sympathetically driven pacemaker (PM) compared with normal sinus function (NSF). Nine men and six women (age 37-80 years) with AV block and a PM controlled by a closed-loop system were studied. Group I included eight patients with CI, and group II included seven patients with NSF. All patients underwent Valsalva maneuver and tilt table testing with measurements of plasma catecholamines and renin activity. Pacing was initially programmed in the DDDC mode at a lower rate (60 ppm) and upper rate limit (0.85 x [220 - age]), then in DDDR in group I and VVIR in group II. The second phase of the study consisted of nitroglycerin and phenylephrine infusions, and the third phase of physiological provocative maneuvers. The second and third phases were performed in three patients from each group with sensor activity On and Off. In group I, heart rate changed during tilt only in the DDDR mode. In group II, heart rate changes were comparable in both modes. Catecholamine levels in group I were higher during DDDC than during DDDR pacing (P < 0.05). In group I, heart rate did not change during phases II and IV of the Valsalva maneuver in the DDDC mode, but behaved nearly physiologically after sensor activation. A late and a paradoxical response to nitroglycerin was observed in groups I and II and to phenylephrine in group I. During physiological maneuvers, significantly greater variations in heart rate were observed during DDDR than during DDDC pacing. Sympathetic SDP provides physiological modulations of the heart rate were provided by a sympathetically driven pacing system in patients with AV block and CI.

[Pacemaker with mechanical sensors. Accumulated experience in long-term follow-up]. / Marcapassos dotados de sensor mecânico. Experiência acumulada em seguimento tardio.

PURPOSE: To evaluate the behavior of single chamber stimulation system, rate responsive with vibration sensing, taking into consideration the results of long term clinical follow-up. PATIENTS AND METHODS: From september 1986 to april 1989, 70 patients received pacemakers with vibration sensing. Sixty four patients (91.9%) implanted Activitrax I model and six (8.1%) Activitrax II. Thirty-one (44.3%) were men and the mean age was 51.2 years. Fifty-one patients (72.9%) had complete atrioventricular block, 11 (15.7%) sinus node dysfunction, one (1.4%) sinus node and atrioventricular disease, and one (1.4%) for therapeutic support of arrhythmia. The etiology of these dysfunctions were Chagas' disease in 31.4%, myocardiosclerosis in 35.7%, post-operative in 15.6%, post-av node fulguration in 5.8% and idiopathic in 11.5%. The group was submitted to clinic and electronic evaluation and laboratory examinations: echocardiogram, dynamic ECG, stress test and ergoespirometric test. The mean follow-up as 19.6 months. RESULTS: Clinic evaluations: decrease in congestive heart failure functional class in 86% of the patients. No recurrence of syncopes and no cardiac deaths. Echocardiogram: increase in ejection fraction in 42% of patients. Dynamic ECG: appropriate rate response in 94.3% of patients (good cronotropic response). Ergoespirometry: increase in oxygen consumption in 75% of studied cases, Electronic evaluation: absence of generator dysfunction; complications in 18% of cases, all corrected by reprogramation. CONCLUSION: The single chamber cardiac stimulation system with vibration sensing showed safety, efficacy and low rate of complications.