Incidentally detected bradyarrhythmias not associated with worse outcomes in older patients

Bradyarrhythmias were found in 20.8% of patients ages 70 years and older who were given an implantable loop recorder compared to 3.8% in a control group, but detection and treatment were not associated with risk of syncope or sudden death, a Danish study found.

Long-term continuous monitoring for atrial fibrillation in older patients was associated with incidental diagnosis of sinus node dysfunction or atrioventricular block and increased pacemaker implantations, but there was no change in the risk of syncope or sudden death, according to a recent study.

To assess bradyarrhythmia prevalence and prognostic significance in patients screened for atrial fibrillation using an implantable loop recorder (ILR), researchers did a post hoc analysis of the Implantable Loop Recorder Detection of Atrial Fibrillation to Prevent Stroke (LOOP), which randomized 6,004 patients, 4,503 to the control group and 1,501 to ILR, at four sites in Denmark. Researchers reviewed data on the patients, who were ages 70 years or older without known atrial fibrillation but with hypertension, diabetes, heart failure, or prior stroke. Results of the study, which was funded in part by Medtronic, were published by JAMA Cardiology on Feb. 15.

Bradyarrhythmia was diagnosed in 172 participants (3.8%) in the control group and 312 participants (20.8%) in the ILR group (hazard ratio [HR], 6.21; 95% CI, 5.15 to 7.48; P<0.001). The condition was asymptomatic in 41 participants (23.8%) in the control group versus 249 participants (79.8%) who had received ILR. The most common bradyarrhythmia was sinus node dysfunction, followed by high-grade atrioventricular block. Risk factors for bradyarrhythmia included older age, male sex, and prior syncope.

Pacemakers were implanted in 132 participants (2.9%) in the control group compared to 67 (4.5%) in the ILR group (HR, 1.53; 95% CI, 1.14 to 2.06; P<0.001). Syncope occurred in 120 patients (2.7%) in the control group and 33 (2.2%) on ILR (HR, 0.83; 95% CI, 0.56 to 1.22; P=0.34), while sudden cardiovascular death occurred in 49 (1.1%) and 18 (1.2%), respectively (HR, 1.11; 95% CI, 0.64 to 1.90; P=0.71).

Bradyarrhythmias were associated with subsequent syncope, cardiovascular death, and all-cause death, with no interaction between bradyarrhythmia and randomization group, the study authors observed. “A substantial proportion of bradyarrhythmias were completely asymptomatic, which was even true for more advanced episodes. Bradyarrhythmias were independently associated with clinical outcomes but not more so for bradyarrhythmias detected by screening than usual care,” they wrote.

An accompanying editorial noted that bradyarrhythmia may be a risk marker for underlying nonarrhythmic conditions, which could be addressed with preventive strategies and treatments.

“The widespread implementation of ILRs to detect a variety of potential or suspected cardiac arrhythmias is a mixed blessing; the same observation applies to the use of devices for prolonged ambulatory recording and patient self-monitoring,” the editorial stated. “Clearly, sensitivity for life-threatening arrhythmic conditions is enhanced with more monitoring, which has obvious benefit for our most fragile populations. Conversely, this advantage is a double-edged sword, as it comes intertwined with the manifest financial and personal costs of overtreatment.”