The open artery hypothesis: potential mechanisms of action.

The postinfarction period is one of intense dynamic activity because the cardiovascular system undergoes a number of adaptive responses attempting to maintain cardiac output. These homeostatic responses contribute to the processes involved in postinfarction ventricular remodeling and involve acute, chronic, systemic, and local reactions. Almost immediately, neurohormones are activated that alter hemodynamic load, and, later, stimulate myocyte hypertrophy, while locally, inflammatory processes clear necrotic debris, reorganize the extracellular matrix, and orchestrate scar formation. Where the initial cardiac insult is sufficiently large (eg, necrosis of more than 40% of left ventricular mass), remodeling responses are exaggerated and may become maladaptive, contributing to the poor long-term prognosis associated with myocardial infarction. Although several studies have shown clear benefits after neurohormonal modulation and/or manipulation of ventricular loading forces in the postinfarction setting, relatively few studies have investigated the potential merits of a patent infarct-related artery during postinfarction ventricular remodeling. In particular, the salutary effects of late revascularization of previously occluded vessels remains controversial. Thus, though this issue remains speculative, our present practice must be governed by circumstantial evidence and hypothetical arguments. This article discusses the potential mechanisms whereby late reperfusion of an infarcted myocardial region may benefit long-term prognosis.