Technologist Track Session 03: Ischemic Heart Disease (2018)-Ischemia physiology

Video Transcription

Video Summary

The speaker explains myocardial ischemia as an imbalance between myocardial oxygen supply and demand, distinguishing acute ischemia (acute coronary syndrome, unstable angina, myocardial infarction, possible sudden death) from chronic ischemia in stable patients. Chronic ischemia is usually caused by stable atherosclerotic plaque causing coronary stenosis, but can also result from spasm or anemia. Oxygen demand rises with increased myocardial mass, work, and ventricular size, while coronary flow depends on diastolic pressure, vascular resistance, and myocardial compression. He emphasizes that angiographic narrowing does not reliably predict functional significance, especially in intermediate stenoses, because the coronary circulation is complex. This is why functional testing is needed. He then links the physiology to CMR stress perfusion imaging: adenosine increases flow in normal vessels, but stenosed vessels cannot dilate further, revealing perfusion defects as areas of hypoenhancement. Stress MRI therefore helps detect clinically significant ischemia.

Keywords

myocardial ischemia

acute coronary syndrome

coronary stenosis

stress perfusion MRI

adenosine perfusion imaging