A sixty-four-year-old woman with Chagas' disease, who underwent implantation of a permanent cardiac pacemaker and evolved with rapidly progressive heart failure

In a previous study of 225 patients with sick-sinus syndrome randomised to either single-chamber atrial pacing (n=110) or single-chamber ventricular pacing (n=115), we found that after a mean follow-up of 3.3 years, atrial pacing was associated with significantly less atrial fibrillation and thromboembolism whereas there was no significant difference in mortality and heart failure between the two groups. We aimed to find out whether this beneficial effect of atrial pacing is maintained during extended follow-up of up to 8 years. Follow-up visits for all patients were at 3 months, 12 months, then once a year at which patients had a physical examination, ECG recording, and pacemaker check-up. Endpoints were mortality, cardiovascular death, atrial fibrillation, thromboembolic events, heart failure, and atrioventricular block. Data was analysed on Dec 31, 1996. At long-term follow-up, 39 patients from the atrial group had died versus 57 from the ventricular group (relative risk 0.66 [95% CI 0.44-0.99]; p=0.045). 19 patients from the atrial group and 39 patients from the ventricular group died from a cardiovascular cause (0.47 [0.27-0.82]; p=0.0065). The cumulative incidences of atrial fibrillation and chronic atrial fibrillation were also significantly lower in the atrial group than in the ventricular group (0.54 [0.33-0.89], p=0.012 and 0.35 [0.16-0.76], p=0.004, respectively). Thromboembolic events occurred in 13 patients in the atrial group and 26 in the ventricular group (0.47 [0.24-0.92], p=0.023). Heart failure was less severe in the atrial group than in the ventricular group (p<0.05). In multivariate analysis, atrial pacing was significantly associated with freedom from thromboembolic events (0.47 [0.24-0.92], p=0.028) and survival from cardiovascular death (0.52 [0.30-0.91], p=0.022), but no longer with overall survival (0.71 [0.46-1.08], p=0.11) or chronic atrial fibrillation (0.45 [0.20-1.05], p=0.063). Atrioventricular block occurred in four patients in the atrial group (0.6% annual risk). The beneficial effect of atrial pacing found in our previous study is enhanced substantially over time. Patients with sick-sinus syndrome should be treated with an atrial rather than ventricular-pacing system because after long-term follow-up, atrial pacing is associated with a significantly higher survival, less atrial fibrillation, fewer thromboembolic complications, less heart failure, and a low-risk of atrioventricular block. Show more

The fundamental determinant of the natural history of Chagas' disease is cardiac involvement. We studied 104 male patients with congestive heart failure due to Chagas' disease to estimate the survival distribution function and to evaluate age, functional class (FC), maximal oxygen consumption (VO2max), and ejection fraction (EF) as predictors of survival. Statistical evaluation was performed through univariate (Student's t test and chi 2 test) and multivariate analyses (Cox's regression model). Overall survival was 66% at 1 year, 56% at 3 years, and 48% at 5 years. Ages were not statistically different (P = .9811) between survivor (40.3 +/- 8.7) and nonsurvivor (40.3 +/- 9.4) groups. The ejection fraction(s) were statistically different (P = .0001) between survival (43.6 +/- 9.9) and nonsurvival (30.6 +/- 8.1) groups, as was VO2max (P = .0001) (21.0 +/- 4.7 and 15.0 +/- 4.9, respectively). Most of the surviving patients were in FC II and most of the nonsurvivors were in FC IV (P = .0001). VO2max (P = .0001) and EF (P = .0008) are highly associated with survival time in the multivariate analysis, but FC (P = .0578) is less important. Age (P = .9811) did not influence survival. We conclude that 50% of the patients with heart failure due to Chagas' disease die in 47 months and that VO2max and EF are important indices of survival in this group. Show more