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Canine coronary microvascular resistance at vasodilation depends on coronary perfusion pressure
Author(s) -
Wijngaard Jeroen,
Horssen Pepijn,
Hoefer Imo,
Spaan Jos,
Siebes Maria
Publication year - 2012
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.26.1_supplement.lb647
Subject(s) - cardiology , medicine , vasodilation , aortic pressure , perfusion , artery , circumflex , hemodynamics
Objective We tested the premise of a constant microvascular resistance at full vasodilation (Rm) that underlies the concept of fractional flow reserve. Methods In 7 anesthetized dogs, we measured aortic (Pa) and venous (Pv) pressure, flow in the left anterior descending (LAD) artery, distal pressure (Pd) in the left circumflex (LCX) artery. During LCX occlusion, wedge pressure (Pw) was measured and μspheres infused into the LAD at full vasodilation. In one dog, the RCA contribution was determined by left atrial injection of differently colored μsph. Hearts were analyzed using a high‐resolution 3D imaging cryomicrotome. The mass of LCX and LAD perfusion territories was obtained. Assuming equal resistance per gram tissue for LAD and LCX, the weight‐normalized Rm of LCX was determined at Pd and Pw. Collateral flow was calculated as the ratio of μsph in LCX and LAD territories multiplied by LAD flow. Results Accounting for the added 30%RCA contribution to the collateral flow obtained from LAD injection, Rm was 2.3 ± 1.9 times higher at low (Pw= 15.7+4.8 mmHg) compared to normal pressure (Pd=69.3+12.4 mmHg) (p<0.05). Collateral flow from LAD to LCX was 8.6% + 5.3% of LAD hyperemic flow. Conclusions Our data confirm the pressure‐dependence of coronary Rm at vasodilation, which suggests a reason for pressure‐based overestimation of collateral flow. Supported by the Netherlands Heart Foundation (2006B226)