A study published in Circulation suggests that intermittent rhythm monitoring severely under-detects atrial fibrillation recurrence and can overestimate success rates of therapeutic interventions for atrial fibrillation.
Efstratios Charitos, Department of Cardiac and Thoracic Vascular Surgery, University of Luebeck, Luebeck, Germany, and others evaluated the most commonly used intermittent rhythm monitoring (IRM) strategies to detect atrial fibrillation recurrence. They reported that two to four sessions of 24h IRM has been shown to “under-detect atrial fibrillation recurrence and thus overestimate success rates of therapeutic interventions”.
They said that as an alternative to IRM, there is continuous monitoring (CM; via an implantable leadless rhythm monitor) but the use of CM in all patients may be unrealistic. Charitos et al wrote: “This has led to the belief that intensifying non-invasive IRM either with greater frequency or with long duration (7-day or 30-day monitoring) or both may lead to better and more reliable detection of atrial fibrillation.” In their study, they used data from a database of patients monitored with a CM device (which has a sensitivity of near 100%) to compare CM-detected atrial fibrillation recurrence with the rate of atrial fibrillation recurrence that IRM (at various frequencies and different durations) would have detected during the same timeframe.
They noted: “The reconstruction of the rhythm history of every patient allows us to evaluate the true probability of atrial fibrillation recurrence of any random IRM of any duration in every patient.”
They found that compared with the number of actual episodes of atrial fibrillation recurrence detected by CM, four sessions of 24-hour holter monitoring had a sensitivity of only 52%-“thus failing to identify atrial fibrillation recurrence in almost half of the patients with proven atrial fibrillation recurrence,” Charitos et al wrote. They added: “This low sensitivity becomes even more striking if one considers that the flipping of a fair coin would have provided the same sensitivity for the detection of atrial fibrillation recurrence in these patients. The direct implication of these results is that the evaluation of pharmacological or interventional therapies when a 24-hour holter monitoring is employed as a monitoring strategy should be interpreted cautiously because a great proportion of patients will be misclassified, atrial fibrillation recurrence will be underdiagnosed and therapeutic success will be overestimated.”
According to Charitos et al, longer and greater frequency holter monitoring had an increased sensitivity-for example, three sessions of 30-day holter monitoring per year would have a sensitivity of 82%. However, the authors stated that such a strategy “seems unrealistic because it has been shown that complex or prolonged IRM strategies severely affect patient compliance.”
As well as reviewing the effectiveness of IRM to detect episodes of atrial fibrillation recurrence, Charitos et al also examined the aggregation of the atrial fibrillation burden and proposed a measure to evaluate the temporal distribution of the atrial fibrillation burden (atrial fibrillation density). They found that patients with a low burden but high density atrial fibrillation would benefit the most from CM.
Concluding, the authors wrote: “Because of the low sensitivity of intermittent rhythm monitoring, the results of pharmacological or invasive interventions for AF when evaluated with intermittent monitoring should be considered with caution because chance has an immeasurable effect on the detection of atrial fibrillation recurrence, and as such a great proportion of patients will be misclassified, atrial fibrillation recurrence will be underdiagnosed, and therapeutic success will be overestimated. For the scientific evaluation of atrial fibrillation treatments, CM should be strongly recommended.”