Patients with TTR Amyloidosis Using Pacemakers

San Francisco—Patients with transthyretin (TTR) amyloidosis who had pacemakers were more likely to be older and male, and have greater beta-blocker use, greater left ventricular septal thickness, and higher brain natriuretic peptide levels compared to those who did not use pacemakers, according to a cross-sectional study that analyzed a global patient registry.

Results were presented at the ACC meeting during a poster session. The poster was titled Pacemaker Use in Patients with Transthyretin Amyloidosis in THAOS: The Transthyretin Amyloidosis Outcomes Survey.

The authors noted that patients with TTR amyloidosis may suffer from restrictive/hypertrophic cardiomyopathy, heart failure, conduction abnormalities, and arrhythmias. In this analysis, they were interested in determining the factors associated with pacemaker use because cardiac involvement is variable and depends on mutations.

They utilized data from the THAOS [Transthyretin Amyloidosis Outcomes Survey] patient registry, a 10-year global study sponsored by Pfizer Inc. They determined the presence of pacemakers by identifying a paced rhythm or an electrocardiogram assessment.

Patients in this study had baseline information collected, including age, sex, nationality, and clinical data. They were considered symptomatic if they had ≥1 symptom at baseline related to or possibly related to TTR amyloidosis such as dyspnea or edema.

Of the 1482 patients in the registry as of September 2012, 138 had wild-type TTR, 454 were asymptomatic TTR mutation carriers, and 890 were symptomatic TTR mutation carriers. Two-thirds of the patients had the Val30Met mutation, which was the most common mutation, with >90% of those patients coming from Portugal, Sweden, and Japan.

The mean age of patients using pacemakers was 63.1 years compared with 47.4 years for patients not using pacemakers (P<.0001); 68.4% of patients using pacemakers were males compared with 53.8% of patients who did not use pacemakers (P=.0024).

The mean left ventricular septal thickness in patients using pacemakers was 18.9 mm compared with 14.4 mm for patients who did not use pacemakers (P=.0007). The mean brain natriuretic peptide level was 2840 pg/mL in the pacemakers group compared with 247 pg/mL for patients who did not use pacemakers (P<.0001). In addition, 20.5% of patients using pacemakers also received beta-blockers compared with 9.0% of patients who did not use pacemakers (P<.0001).

There were also geographical differences, with patients in France and the United States more likely to have pacemakers than those in Japan, Denmark, Germany, Italy, Portugal, Sweden, and Brazil. Patients in Portugal were less likely to use pacemakers compared with patients in other countries.

The authors also performed a multiple logistic regression analysis and found age (odds ratio [OR], 1.03; 95% confidence interval [CI], 1.00-1.05; P=.041), syncope (OR, 3.97; 95% CI, 1.50-10.53; P=.006), and brain natriuretic peptide level <100 pg/mL (OR, 0.12; 95% CI, 0.05-0.33; P<.0001) were potential predictors for using pacemakers.

The authors cited a few limitations, including that they did not determine the type of pacemaker used or the presence of concomitant defibrillators. They also noted that patients with a pacemaker that was not pacing at the time of an electrocardiogram would be misclassified, although they said there would not be a significant misclassification because a significant number of patients with TTR become dependent on pacemakers.

This study was sponsored by Pfizer Inc.