NOVEL INVESTIGATIVE TOOLS IN PATIENTS WITH SUSPECTED INHERITED HEART RHYTHM DISORDERS

Abstract

Patients with inherited heart rhythm disorders (IHRD) attend regional specialty clinics to undergo a series of cardiac investigations, including ECG, Holter monitor, and exercise tests. Cardiac patch monitors may help reduce the burden of hospital-based testing and extend the ability to capture ambient arrhythmias, changes in heart rate with daily activities and physiologic exercise. We compared home-based patch monitoring to conventional Holter monitoring and exercise testing. Patients assessed at St. Paul’s Hospital from the BC Inherited Arrhythmia Clinic (catchment 4.6 million persons) underwent single ECG lead patch monitoring for seven days (Icentia CardioSTAT device) in a prospective feasibility study, compared to conventional testing modalities. Corrected QT intervals were measured and calculated according to Bazett’s formula. 39 patients underwent seven-day patch monitoring (median age 44 years (range 15-70), 61% male). In a follow-up interview, 76% of patients expressed satisfaction and preferred the device over Holter monitor. The median duration of monitoring was 7.0 days (range 2.0-7.3), with 12% noise during the first 24-hours (median 176 minutes, range 25min-12h). All but one patient was in sinus rhythm throughout (one patient with known atrial fibrillation). The median HR, PAC and PVC burden, and supraventricular and ventricular runs are reported, with strong correlations in all variables between monitoring modalities, except for PVC burden and supraventricular runs (Table). Patch monitors demonstrated variability in ectopic burden over seven days (PACs: 114±451 over 24-hours vs. 161±527 over seven days; PVCs: 388±942 over 24-hours vs. 428±972 over seven days). Compared to the median PAC and PVC burden over seven days, Holter monitoring under- or overestimated ectopy by over 20% in 84% of cases (PAC variation: median 7%, range -100 to +43,000%; PVC variation: median 33%, range -100 to +867%). Corrected QT intervals correlated across monitoring modalities at rest (Figure, Pearson Correlation 0.781 and 0.776), but demonstrated poor correlation at peak heart rate compared to exercise testing (Pearson Correlation 0.098 and 0.161). Most patients (82%) did not reach 85% of the age-predicted maximum heart rate on the patch monitor. The cardiac patch monitor is a reliable option in the diagnostic work-up of patients with suspected IHRD, with basic measurements consistent with other devices. The burden of PACs and PVCs varies significantly day-to-day, and prolonged monitoring may provide for more reliable quantification and improved arrhythmia detection in patients with suspected IHRD. QTc measurements were reproducible at rest, but correlation at peak heart rates was poor and requires further investigation.View Large Image Figure ViewerDownload Hi-res image Download (PPT)