The alternative "ischemic" cascade in coronary microvascular disease

Area of Science:

• Cardiology
• Physiology

Background:

• The classical ischemic cascade model accurately predicts findings in epicardial coronary artery disease.
• However, it inadequately explains ischemia-like changes in conditions with normal coronary arteries, such as syndrome X, hypertension, and hypertrophic cardiomyopathy.

Purpose of the Study:

• To propose an integrated view of myocardial ischemia, incorporating an alternative cascade model for microvascular disease.
• To highlight the diagnostic limitations of traditional stress testing in microvascular dysfunction.

Main Methods:

• Review of clinical experience and pathophysiological understanding of ischemic syndromes.
• Analysis of the relationship between ECG changes, perfusion abnormalities, and echocardiographic findings in various cardiac conditions.

Main Results:

• Stress-induced ischemic-like ECG changes are common in microvascular disease, often without echocardiographic abnormalities.
• These ECG changes correlate with impaired coronary flow reserve and endothelial dysfunction.
• In hypertrophic cardiomyopathy, ST segment depression predicts adverse events.

Conclusions:

• The classical ischemic cascade model should be expanded to include an alternative cascade for microvascular disease, where ECG changes precede perfusion deficits.
• Myocardial ischemia is heterogeneous, and stress echocardiography may miss milder forms of ischemia.
• Considering coronary flow reserve and endothelial function provides a more complete physiological truth beyond anatomical "lies" on the ECG.