Systematic review and meta-analysis of Murray's law in the coronary arterial circulation

Area of Science:

• Physiology
• Biomedical Engineering
• Cardiovascular Research

Background:

• Murray's law, a physiological principle relating blood flow to vessel diameter (∝D³), informs percutaneous coronary intervention (PCI) minimum lumen area targets.
• The cubic exponent in Murray's law has been debated, with theoretical work suggesting a value closer to 2.33 (7/3).

Purpose of the Study:

• To conduct a meta-analysis to determine the optimal flow-diameter exponent in human and mammalian coronary arteries.
• To compare the empirically derived exponent with existing theoretical models.

Main Methods:

• Systematic review and meta-analysis of studies quantifying flow-diameter exponents in coronary arteries.
• Data sourced from Cochrane, PubMed Medline, Scopus, and Embase databases.
• Random-effects meta-analysis used to pool exponents; risk of bias assessed using NIH tools, funnel plots, and Egger regression.

Main Results:

• Included 18 studies with data from 1,070 coronary trees (372 human, 112 animal).
• The pooled flow-diameter exponent was 2.39 (95% CI: 2.24-2.54), with high heterogeneity (I² = 99%).
• The pooled exponent closely aligns with the theoretical value of 2.33 (7/3).

Conclusions:

• The empirically determined exponent of 2.39 provides a potentially more accurate description of coronary morphometric scaling than Murray's original law.
• Findings have significant implications for assessing, diagnosing, and treating coronary artery disease through interventions like PCI.