Automatic measurement of short-term variability of repolarization captures modulation by pacing on human electrograms

Figures

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  Figure 1. Study design. (A) Flowchart of patient population and selection of signals for analysis. (B) Pacing protocol during study measurements with each pacing mode applied for 1 minute in first study and 2 minutes in the follow-up study. AAI80 = atrial pacing at 80 beats/min; AV = atrioventricular; DDD = dual-chamber pacing; DDD80 = dual-chamber pacing at 80 beats/min; ECG = electrocardiogram; EGM = electrogram; excl. = excluded; ICD = implantable cardioverter-defibrillator; SR = sinus rhythm; STV-ARI = short-term variability of repolarization determined from the activation recovery interval.

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  Figure 2. Schematic overview of the fiducial segment averaging technique to measure short-term variability of repolarization (STV). (A) STV determined on the electrocardiogram with fiducial segment averaging. Complexes were aligned at the R peak, onset of the QRS complex, and the T-wave end to determine QT interval for each individual beat. (B) STV determined on the electrogram from the activation recovery interval (ARI) with fiducial segment averaging. The fiducial points were defined as the minimum dV/dt of the QRS complex as the ARI onset and the maximum dV/dt of the T-wave as the ARI offset.

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  Figure 3. Schematic overview of the automatic method to measure short-term variability of repolarization (STV). (A) STV determined on the electrogram from the activation recovery interval (ARI) using the automatic method. Ventricular sensing indicates the start of repolarization and establishes a dynamic window based on the RR interval. For dual-chamber pacing, the ARI offset is set as 60% of the area under the curve (AUC) of the first derivative of the T-wave. (B) For sinus rhythm and atrial pacing, a window of 120 ms was opened around the point determined in panel A and ARI offset was defined as maximum |dV/dt|.

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  Figure 4. Modulation of short-term variability (STV) of repolarization by pacing. Decrease of STV from sinus rhythm (SR) to atrial pacing at 80 beats/min (AAI80) and dual-chamber pacing at 80 beats/min (DDD80) measured by (A) STV determined on the electrocardiogram with fiducial segment averaging (STV-QTFSA), (B) STV determined on the electrogram from the activation recovery interval with fiducial segment averaging (STV-ARIFSA), and (C) STV determined on the electrogram from the activation recovery interval with the automatic method (STV-ARIauto). ∗P < .05 using mixed-model analysis of variance.

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  Figure 5. Comparison between the gold standard and automatic method to measure short-term variability of repolarization (STV) on the cardiac electrogram. (A) Linear regression between STV determined on the electrogram from the activation recovery interval with fiducial segment averaging (STV-ARIFSA) and STV determined on the electrogram from the activation recovery interval with the automatic method (STV-ARIauto). (B) Bland-Altman analysis comparing STV-ARIFSA and STV-ARIauto.