R/S Ratio Variability in Lead V1 Observed between Selected Four 1-Minute ECG Fragments of 24-Hour ECG as a Predictor of Incomplete Resynchronization during Full 24-Hour ECG: Pilot Study

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About 30% of patients do not have an effective cardiac resynchronization therapy (CRT). Routine assessment of CRT by devices interrogation (DI) is not entirely reliable. Additional information provide detailed QRS analysis in 24-hour ECG, however it is time-consuming. The aim of the study was the assessment of R/S ratio variability in lead V1 between selected fragments of 24-hour ECG as a predictor of incomplete biventricular pacing (BIVP) during full 24-hour ECG.


The 12-lead 24-hour ECGs of 43 patients with sinus rhythm were studied. During 24-hour ECG the 6-minute walk test (6MWT) was performed. The CRT was assessed by analyzing DI and full 24-hour ECG and four 1-minute fragments of these ECG recordings: during the minimum and the maximum heart rate and at the 1st and last minute of 6MWT.


During DI the effective (>95%) BIVP was present in 36 patients (83.7%). Analysis of full 24-hour ECG confirmed appropriate BIVP in 31 patients (72%) and suspected incomplete BIVP (≤95%) in 12 patients (28%). In 9/12 patients the R/S ratio variability in lead V1 was visible between selected ECG fragments of 24-hour ECG. These results were not associated with the results of DI but were significantly associated with full 24-hour analysis of QRS.


R/S variability in lead V1 between selected fragments of 24-hour ECG can be considered a predictor of potentially incomplete BIVP confirmed by further complete 24-hour ECG analysis in patients with appropriate pacing reported during DI.

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