A 70-year-old male is admitted after a massive anterior myocardial infarction and initially stabilizes with medical management. Several days later, he suddenly develops ventricular tachycardia followed by cardiac arrest. Histologic remodeling of the infarcted myocardium reveals fibroblast infiltration with deposition of type I collagen, replacing large numbers of necrotic cardiac myocytes. Which of the following best explains the principal cause of death in patients following a massive myocardial infarction?