Myocardial ischemia: From disease to syndrome

1. Introduction

In recent years, conceptual models of ischemic heart disease (IHD) have continued to evolve. The hypothesis of obstructive atherosclerotic coronary artery disease (CAD) as the prevalent if not the only cause of myocardial ischemia is now being reconsidered, acknowledging that other mechanisms may precipitate myocardial ischemia, alone or in combination. This new understanding of myocardial ischemia as a multifactorial condition, is based on a large body of scientific evidence proving that obstructive coronary atherosclerosis is not consistently associated with myocardial ischemia and, conversely, that myocardial ischemia often occurs in the absence of obstructive atherosclerosis.

In addition to vascular mechanisms, non-vascular factors, including abnormalities in cardiac energy metabolism and changes in blood rheology secondary to platelet activation and/or inflammation will probably be considered in the near future among the mechanisms responsible for myocardial ischemic syndromes. These concepts underscore the need for embracing a more inclusive understanding of myocardial ischemic syndromes than the traditional, “stenosis-centric” approach would allow.

This document will discuss the need and the implications of a paradigm shift in current clinical practice, consistent with the new understanding of the pathogenesis of myocardial ischemic syndromes.

2. The impact of multiple mechanisms of ischemia on diagnostic approaches

Current management is focused on the “epicardial coronary obstruction-first” approach, assuming that obstructive atherosclerosis remains the primary and proximate cause of myocardial ischemia, and that, in the presence of obstructive atherosclerosis, there is no need to search for other possible alternative or coexisting mechanisms of ischemia. Thus, despite guideline recommendations, contemporary practice remains largely centered on the management of obstructive epicardial CAD, with the therapeutic goal of removing flow-limiting coronary stenoses.

In the future, the identification of the precipitating mechanisms(s) of myocardial ischemia in the individual patient and the prevalence of non-obstructive mechanisms in patients with or without obstructive coronary atherosclerosis is expected to become a key step in the management of patients with chronic ischemic syndromes.