R-wave detection by subcutaneous ECG. Possible use for analyzing R-R variability.

BACKGROUND: Atrial arrhythmia (AA) discrimination remains a technological challenge for implanted cardiac devices. We examined the feasibility of R-wave detection by a subcutaneous far field ECG (SFFECG) and analysis of these signals for R to R variability as an indicator of atrial arrhythmia (AA). METHODS: Surface ECG and SFFECG (from the pacemaker pocket) were recorded in sixteen patients (61.5 +/- 11.4 years) with AA. The SFFECG was recorded with a pacemaker sized four electrode array acutely placed in the pacemaker pocket during implantation. The signals were analyzed to obtain peak-to-peak R wave amplitude and R to R interval variability (indicative of AAs). RESULTS: In sixteen patients R waves were visually discernible in all recordings. The percentage over and under detection for automatic R wave recognition SFFECG was 3 and 9%, respectively. R to R variability analysis using the SFFECG produced results concordant to those using the surface ECG. CONCLUSION: SFFECG might be a helpful adjunct in implantable device systems for detection of R waves and may be used for measurement of R to R variability.