iRhythm Holdings Inc. (NASDAQ: IRTC) presented data at the Heart Rhythm Society's annual meeting showing that short-term cardiac monitoring misses significant arrhythmias in post-ablation and pregnancy patients.

The company analyzed 11,051 patients who underwent atrial fibrillation ablation and used Zio ambulatory ECG devices for monitoring. The study found that 26% of patients had their first detected AF recurrence beyond 48 hours, suggesting that standard 24-48 hour Holter monitoring would miss these cases. Among patients with paroxysmal AF, 29.8% had recurrence detected after 48 hours.

A separate study examined 486 pregnant women using extended monitoring. Arrhythmias were detected in 37.7% of patients, with clinically significant arrhythmias found in 13.6%. Notably, 60% of arrhythmias were first detected after 48 hours of monitoring.

"Monitoring of 48 hours or less leads to false negatives of AF recurrence in 30% of those monitored in the year following-PVI," said Mintu Turakhia, Chief Medical and Scientific Officer at iRhythm.

The findings have implications for clinical decision-making, particularly regarding anticoagulation management after ablation procedures. The OCEAN trial, which used 24-48 hour monitoring strategies, may have missed AF recurrence in a substantial portion of patients based on these results.

For the pregnancy study, the median analyzable time was 99.2%, indicating high-quality data collection during extended monitoring periods. The research addresses a gap in evidence for arrhythmia detection during pregnancy, where cardiovascular disease remains a leading cause of pregnancy-related deaths.

The studies add to iRhythm's clinical evidence supporting extended cardiac monitoring over shorter-duration alternatives for comprehensive arrhythmia detection across patient populations.