A, Representative ECG of 2 consecutive paced beats (120 ms cycle length) normalized peak-to-peak and superimposed (a and b) to demonstrate ECG T-wave alternans (ECG ALT) in a myocardial infarction (MI) heart but not in a sham. Summary data (right) show that over all experiments MI hearts (n=20) had significantly higher ECG ALT compared with sham hearts (n=8). B, Representative intracellular Ca2+ transients from a sham and MI heart at a pacing cycle length of 120 ms and normalized peak-to-peak demonstrating beat-to-beat Ca2+ transient amplitude alternans (Ca2+ ALT) in MI but not shams. Summary data show that over all experiments, MI hearts (n=7) had significantly higher Ca2+ ALT as compared with sham hearts (n=8).
A, Representative intracellular Ca2+ transients recorded at a slow pacing cycle length (300 ms) and normalized peak-to-peak demonstrate a longer duration (measured at 85% of diastole) in myocardial infarction (MI) compared with sham hearts. Summary data show that Ca2+ transient durations are significantly prolonged in MI hearts (n=6) compared with shams (n=5). B, Western blots against sarcoplasmic reticulum Ca2+ ATPase (SERCA2a) and actin (loading control) for sham and MI hearts. Summary data show that across all hearts (n=3 for each), SERCA2a protein expression was unchanged in MI.
Representative contour maps of epicardial Ca2+ ALT magnitude induced by rapid pacing (120 ms) in a sham and myocardial infarction (MI) heart, overlaid on a schematic of the whole heart. The size of the mapping field corresponds to 14.2×14.2 mm. Ca2+ ALT is absent in the sham; however, large Ca2+ ALT are present in the region of the scar (dashed line) of the MI heart.
A, Contour maps of reactive oxygen species (ROS; green), determined by measuring dichlorodihydrofluorescein diacetate (DCF) fluorescence from the epicardial surface of a sham, myocardial infarction (MI), and MI+allopurinol (ALLO) heart, overlaid on a schematic of the whole heart. B, Shown are consecutive transverse cross-sections (20 μm) from an MI heart. The first slice was stained with H&E (left) and the second was superfused with DCF (right). Black arrows point to the epicardial scar. C, Correlation between ROS and Ca2+ ALT (measured in separate animals) for all sham hearts along with the border zone (BZ) and remote (REM) regions of all MI hearts.
