Key Points
- To evaluate how subacute and chronic healing myocardial infarction alters epicardial activation wave front dynamics, organization, and cycle length during ventricular fibrillation.
- Assessed 17 dogs across three groups: subacute healing myocardial infarction at 1 week (n=6), chronic healing myocardial infarction at 8 weeks (n=5), and noninfarcted controls (n=6).
- Recorded 112 epicardial electrograms and generated 91 vector loops per cycle across anterior infarcted and lateral noninfarcted walls using a 2.5-mm spaced plaque electrode during induced ventricular fibrillation.
- Quantified wave front area, spatial linking across interelectrode distances (2.5 to 7.5 mm), and cycle length across early cycles and after 5 seconds of ventricular fibrillation.
- Mean wave front areas were significantly larger in subacute (97 ± 4 mm² early; 78 ± 3 mm² late) and chronic MI (94 ± 5 mm² early; 78 ± 5 mm² late) compared to noninfarcted controls (73 ± 5 mm² early; 61 ± 3 mm² late).
- Mean ventricular fibrillation cycle length was significantly prolonged in subacute (121 ± 13 ms) and chronic MI (127 ± 13 ms) compared with controls (98 ± 5 ms), showing regional slowing specifically over anterior infarcted walls.
- Spatial linking at 7.5 mm was lower in control animals than in infarcted groups, confirming smaller wave front sizes, less activation organization, and faster conduction velocities in normal myocardium.
Structured PICO
Does the presence of subacute or chronic healing myocardial infarction alter the characteristics of ventricular fibrillation in a canine model?
PPopulation17 dogs (6 with subacute healing myocardial infarction [1 week], 5 with chronic healing myocardial infarction [8 week], and 6 without myocardial infarction)
IInterventionInduction of ventricular fibrillation by programmed stimulation
CComparatorDogs without myocardial infarction (normal control animals)
OOutcomeEpicardial activation characteristics during ventricular fibrillation (wave front size, cycle length, conduction velocity, degree of organization)surrogate
The presence of regional myocardial infarction alters the characteristics of ventricular fibrillation, resulting in larger activation wave fronts, longer cycle lengths, slower conduction velocities, and greater organization compared to normal hearts.