Automatic measurement of short-term variability of repolarization to indicate ventricular arrhythmias in a porcine model of cardiac ischaemia

Figures

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  Figure 1. Overview of experimental setup. (A, top) Schematic overview of occlusion of the mid LAD coronary artery to induce VT/VF (A, bottom) illustration of electrode placement for the 12-lead ECG for all study parts, addition of an EGM catheter in Part 2 and a pacemaker for the intervention group of Part 2. (B) Representative traced of the precordial leads of the ECG and first four EGM vectors (EGM in Part 2 only) during ischaemia. Arrows indicate pacing spikes. (C) Experimental design and timepoint taken for assessment of EP parameters. LAD, left anterior descending coronary artery; VT, ventricular tachycardia; VF, ventricular fibrillation; EP, electrophysiological; AAI [SR + 20/min], atrial demand pacing at 20 beats per min faster than sinus rhythm.

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  Figure 2. Schematic overview of techniques to measure short-term variability (STV) of repolarization. (A) STV-QTFSA measured with fiducial segment averaging (FSA) on the ECG. 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. (BI) STV-ARIauto measured with the new automatic method on the EGM. Ventricular sensing indicates the start of repolarization and establishes a dynamic window based on the RR interval. (BII) After blanking of the QRS, ARI offset is determined as 60% of the area under the curve (AUC) of the first derivative of the T-wave.

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  Figure 3. Temporal changes in STV during ischaemia of Part 1. STV-QTFSA increases before VF or VT during ischaemia. Data expressed as mean (bar) ± SD (brackets). *P < 0.05 vs. baseline; ‡<0.05 vs. occlusion. STV-QTFSA, short-term variability of the QT interval calculated with fiducial segment averaging; VF, ventricular fibrillation; VT, ventricular tachycardia.

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  Figure 4. Temporal changes in STV during ischaemia of Part 2. (A) STV-QTFSA increases before VF or VT during ischaemia. (B) STV-ARIauto increases prior to VF or VT during ischaemia. Data expressed as median (bar) ± interquartile range (brackets). Data 1 min before VT/VF and just before VT/VF represent measurements from the control group only (n = 4) due to pace spike interference in the T-wave. *P < 0.05 vs. baseline; STV-QTFSA, short-term variability (STV) of the QT interval calculated with fiducial segment averaging; STV-ARIauto, STV of the activation recovery interval (ARI) of intracardiac electrograms calculated with the new automatic method; VF, ventricular fibrillation; VT, ventricular tachycardia.

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  Figure 5. Comparison of STV-QTFSA and STV-ARIauto values. (A) Spearman’s correlation coefficient of the percentage changes from baseline to the successive three timepoints between STV-QTFSA and STV-ARIEGM. (B) Bland–Altman analysis comparing the difference between STV-QTFSA and STV-ARIauto to the mean. STV-QTFSA, short-term variability (STV) of the QT interval calculated with fiducial segment averaging; STV-ARIauto, STV of the activation recovery interval (ARI) of intracardiac electrograms calculated with the new automatic method; succ., successive.

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  Figure 6. Comparison between control and intervention groups. (A) Number of defibrillation shocks administered. (B) Median time to developing the first VT or VF episode. (C) Percentual change in EF measured at baseline vs. after 1 h of reperfusion. Data expressed as median (bar) ± interquartile range (brackets). *P < 0.05. EF, ejection fraction; VT, ventricular tachycardia; VF, ventricular fibrillation.