A retrospective analysis of randomised clinical trials has found that one in five patients aged 70 years or older with cardiovascular risk factors are diagnosed with bradyarrhythmias when long-term monitoring for atrial fibrillation (AF) using implantable loop recorder (ILR) is applied.
The authors state this is the “first study” to analyse incidental diagnosis of bradyarrhythmia. Focusing their research on the Implantable Loop Recorder Detection of AF to Prevent Stroke (LOOP) randomised clinical trial—which took place at four sites across Denmark—participants included those with unknown AF aged 70 or over, with an existing diagnosis of diabetes, hypertension, heart failure, or prior stroke, between January 2014 and May 2016.
“The digital age holds promise of early detection of a range of conditions,” principal investigator (PI) Søren Zöga Diederichsen (Rigshospitalet, Copenhagen, Denmark) stated, situating their study as one which could provide insight into the “underlying prevalence and prognostic significance of bradyarrhythmias”, which may benefit clinical decision-making.
The study’s primary outcome measure was adjudicated bradyarrhythmia episodes, pacemaker implantation, syncope and sudden cardiovascular death, at a median follow-up period of 65 months.
In total, 6,004 patients were randomised—47.3% were female and 52.7% male, with a mean age of 75 years. In addition, 90.7% of the included cohort had a diagnosis of hypertension and 20.4% with prior syncope. The researchers assigned 4,503 to control and 1,501 to ILR, diagnosing bradyarrhythmia in 172 patients (3.8%) in the control group versus 312 (20.8%) in the ILR cohort (hazard ratio [HR], 6.21; 95% CI, 5.15–7.48 p<0.001). They also identified 41 asymptomatic patients (23.8%) versus 249 symptomatic participants (79.8%), respectively.
Diederichsen et al found the most common bradyarrhythmia to be sinus node dysfunction (SND) followed by high-grade atrioventricular block (AVB). Risk factors for the condition included advanced age, male sex, and prior syncope.
A pacemaker was implanted in 132 patients (2.9%) versus 67 (4.5%), while syncope occurred in 120 (2.7%) versus 33 (2.2%). Additionally, sudden cardiovascular death occurred in 49 (1.1%), versus 18 (1.2%), in the control and ILR groups respectively.
Their findings show that screening affected a six-fold increase in bradyarrhythmia detection and increased pacemaker implantations compared with usual care, with no signal toward a change in the risk of syncope or sudden death. Noting an “excessive increase” in SND and AVB diagnosis when employing long-term AF screening, the authors admit this did not improve clinical outcomes.
Rather, Diederichsen and colleagues posit that bradyarrhythmia detection may be a risk marker for later disease, commenting on the “high prevalence” and “overlapping findings” of incidental bradyarrhythmia and AF. On reflection, they believe this highlights the importance in identifying whether these arrhythmias represent “clinical problems”.
“When detected at an asymptomatic, subclinical stage, questions arise to whether abnormal findings represent a clinical problem needing diagnosis and treatment or are merely a risk marker without implications.” The authors conclude Should screening for subclinical AF or bradyarrhythmia prove clinically relevant, a next question will be by which means screening should be performed.”