Regional beat-to-beat variability of repolarization increases during ischemia and predicts imminent arrhythmias in a pig model of myocardial infarction

Figures

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  Figure 1.. Assessment of beat-to-beat variation of repolarization (BVR) in a pig model of myocardial infarction and sudden cardiac death. A: anterior-posterior angiographic views of the left coronary arteries (left) illustrating occlusion of the mid left anterior descending artery (LAD; middle). A, right: cardiac magnetic resonance imaging of the infarcted heart 1 mo after ischemia-reperfusion (I/R) illustrating 21% infarction of left ventricular mass. Red arrows indicate infarct scar. B: schematic illustrating the ECG electrode placement in the pig (left) and examples of the 12-lead ECG at baseline and during ischemia (right); note the dramatic ST changes in V1–V6. C: illustration of the experimental design and selected taken to analyze BVR. aVF, augmented vector foot; aVL, augmented vector left; aVR, augmented vector right; ECG, electrocardiogram; LCX, left circumflex coronary artery; VT/VF, ventricular arrhythmia; n, number of animals.

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  Figure 2.. Beat-to-beat variation of repolarization (BVR) increases during regional ischemia and is related to the extent of injury. A: summary data of 12-lead ECG ST-segment deviation (left) and serum troponin after 120 min acute myocardial ischemia (right); n = 16 myocardial infarction (MI) and 8 sham. One-way and mixed-effects model ANOVA with Bonferroni posttest, respectively. B, left: example of Poincaré plots of the QT interval at baseline and during ischemia in MI (top) and sham (bottom) animals. B, right: summary data of 12-lead ECG BVR; n = 16 MI and 8 sham. Mixed-effects model ANOVA with Bonferroni posttest. C, left: correlation between cumulative BVR and ST deviation in all 12 ECG leads. C, right: correlation between cumulative BVR and serum troponin; n = 16 MI. Linear regression analysis. ANOVA, analysis of variance; aVF, augmented vector foot; aVL, augmented vector left; aVR, augmented vector right; ECG, electrocardiogram; n, number of animals.

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  Figure 3.. Heart rate and QT interval during ischemia. A: summary data of heart rate [in beats/min, (bpm)] at baseline and during ischemia. B: summary data of QT interval duration in the 12 ECG leads at baseline and during ischemia in myocardial infarction (MI; top) and sham (bottom). C: summary data of QT dispersion at baseline and during ischemia; n = 16 MI and 8 sham. Mixed-effects model ANOVA with Bonferroni posttest. ANOVA, analysis of variance; aVF, augmented vector foot; aVL, augmented vector left; aVR, augmented vector right; ECG, electrocardiogram; n, number of animals.

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  Figure 4.. Beat-to-beat variation of repolarization (BVR) increases further before spontaneous ventricular fibrillation (VF) during ischemia. A: typical example of spontaneous onset VF during acute myocardial ischemia (AMI; top), and Kaplan–Meier plots of freedom from ventricular arrhythmia (VT/VF) during AMI. Log-rank test. B, left: summary data of temporal BVR changes during AMI in relation to the occurrence of VF and matched time points (by duration of ischemia) in six sex- and weight-matched animals without VF. B, right: summary data of the change in BVR from B, left; n = 10 animals with (VF +ve) and 6 animals without (VF −ve) VF. Multilevel mixed-effects linear model with Bonferroni correction. C: summary data of the incidence of premature ventricular complexes (PVCs) during AMI; n = 10 VF +ve and 6 VF −ve. Multilevel mixed-effects linear model with Bonferroni correction. VT, ventricular tachycardia; n, number of animals.

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  Figure 5.. Beat-to-beat variation of repolarization (BVR) is elevated and associated with arrhythmia vulnerability in chronic myocardial infarction (MI). A, left: example of midventricular short-axis cMRI indicating 19.0% infarction (red arrows) after 1 mo. A, right: summary data of infarct size, n = 12 MI and 7 sham; two-tailed t test. B: serum creatinine kinase concentration at baseline, ischemia, and after 1 mo. Mixed-effects model ANOVA with Bonferroni posttest. C, left: summary data of BVR after 1 mo in MI (n = 9) and sham (n = 7); two-tailed t test. C, right: correlation between infarct size and BVR; n = 9 MI. Linear regression analysis. D: illustration of programmed stimulation protocol to induce ventricular arrhythmia (VT/VF; top) and the algorithm used to assess inducibility index based on aggressiveness of stimulation protocol (bottom). E, top: correlation between infarct size and VT/VF inducibility and bottom, correlation between BVR and VT/VF inducibility; n = 8 MI. Linear regression analysis. ANOVA, analysis of variance; LV, left ventricular; VF, ventricular fibrillation; VT, ventricular tachycardia; n, number of animals.