CardiologyTier 2Topic

Coronary blood flow

Diastolic coronary perfusion

Unique among vascular beds - coronary flow occurs predominantly during diastole (unlike most organs, perfused mainly in systole), because systolic compression of the myocardium collapses the intramural coronary vessels
Explains why tachycardia (shortened diastole) and diastolic hypotension both reduce coronary perfusion, and why bradycardia can paradoxically improve ischaemic symptoms in some settings

Coronary perfusion pressure ~ aortic diastolic pressure - LV end-diastolic pressure - explains why severe aortic stenosis (high LV pressure) or severe hypotension both compromise coronary flow even with normal coronary arteries
Autoregulation maintains flow across a wide pressure range via metabolic (adenosine-mediated) and myogenic mechanisms - flow is tightly coupled to myocardial oxygen demand
The subendocardium is the most vulnerable layer to ischaemia (highest wall tension, furthest from the epicardial supplying vessels, perfused last) - explains the subendocardial predominance of early ischaemic injury

Fractional flow reserve (FFR) during angiography measures the pressure drop across a stenosis to assess its physiological (not just anatomical) significance, based on these flow principles

Explains why tachyarrhythmia can precipitate angina/ischaemia even without new coronary disease, and why heart rate control (beta-blockers) is a core anti-anginal strategy - increasing diastolic filling time for coronary perfusion, not just reducing demand
Stable angina pathophysiology, aortic stenosis (coronary flow compromise at very high LV pressures), microvascular angina

Coronary flow reserve (the ability to augment flow above resting levels) is progressively exhausted as stenosis severity increases, explaining the transition from exertional to rest angina

4 more sections, plus exam facts

Premium unlocks every note across every specialty, and the full exam fact library behind it.