Fundamentals in clinical coronary physiology: why coronary flow is more important than coronary pressure

Area of Science:

• Cardiovascular Medicine
• Interventional Cardiology
• Physiology

Background:

• Stable ischaemic heart disease (IHD) management increasingly utilizes coronary physiology.
• Fractional flow reserve (FFR), derived from coronary pressure, is widely used to guide revascularization decisions.
• Evidence suggests FFR-guided revascularization is superior to angiography-guided approaches.

Purpose of the Study:

• To highlight that FFR is an indirect estimate of coronary flow.
• To explain why direct coronary flow measurement is physiologically and clinically more important than pressure.
• To discuss the limitations of FFR in clinical decision-making and risk stratification for IHD.

Main Methods:

• Review of existing literature on coronary physiology, FFR, and coronary flow.
• Analysis of the physiological basis of ischaemia and the determinants of myocardial oxygen supply and demand.
• Discussion of the clinical implications and scientific consequences of using FFR as a reference standard.

Main Results:

• FFR is a pressure-derived estimate, not a direct measure of coronary flow.
• Coronary flow is the critical determinant of myocardial ischaemia, not solely coronary pressure.
• Current reliance on FFR may overlook crucial aspects of flow impairment and its clinical impact.

Conclusions:

• Coronary flow measurements offer a more direct and potentially superior approach to assessing ischaemia in IHD compared to FFR.
• Rethinking the gold standard and incorporating direct coronary flow assessment could improve risk stratification and guide revascularization decisions.
• Future research should focus on the clinical utility of direct coronary flow measurements in IHD management.