Importance of myocardial ischaemia for recruitment of coronary collateral circulation in dogs.
OBJECTIVE
The aim of the study was to investigate collateral coronary flow and regional myocardial function following different coronary occlusion protocols.


METHODS
Effects of brief left anterior descending artery (LAD) occlusions in dogs (using a pneumatic occluder around the proximal artery) on collateral circulation were evaluated using three different protocols, each producing the same period of pressure gradient across the collateral network: (1) 10 s occlusion X 30 at 1 min intervals; (2) 1 min occlusion X 5 at 1 min intervals; (3) 5 min occlusion X 1. Each protocol was followed by a 10 s occlusion after a further 1 min period.


METHODS
14 mongrel dogs of either sex were used, weight 10-21 kg.


RESULTS
Left ventricular pressure, left circumflex coronary artery (LCCA) flow, and subendocardial segment shortening (% delta L) in the area perfused by the LAD were monitored. Collateral blood flow from LCCA to LAD territory was measured as a stepwise decrease in LCCA flow on release of LAD occlusion. During the first 10 s of occlusion, % delta L decreased from 23.6(SEM 2.2)% to 14.2(2.9)%. After protocol (1), % delta L decreased from 23.1(2.2)% to 14.8(3.0)%. By contrast, after protocol (2) and (3) % delta L decreased only slightly, from 22.7(2.6)% to 20.5(2.8)%, and from 22.4(2.4)% to 19.8(2.4)%, respectively. Although collateral blood flow remained unchanged after protocol (1), it increased from 1.6(0.4) ml.min-1 during the first LAD occlusion to 3.0(0.7) ml.min-1 (p less than 0.05) after protocol (2), and to 3.5(0.6) ml.min-1 (p less than 0.05) after protocol 3. Haemodynamic measurements prior to each 10 s LAD test occlusion remained unchanged throughout the experiment.


CONCLUSIONS
The pressure gradient across the collateral network cannot dilate pre-existing collateral vessels by itself, but ischaemia related metabolites may play an important role in the recruitment of collateral circulation.
Yamanishi
K
K
Second Department of Internal Medicine, Toyama Medical and Pharmaceutical University, Japan.
Fujita
M
M
Ohno
A
A
Sasayama
S
S
D000818:Animals; D001783:Blood Flow Velocity; D001794:Blood Pressure; D003097:Collateral Circulation / Q000502:physiology*; D003250:Constriction; D003326:Coronary Circulation / Q000502:physiology*; D003327:Coronary Disease / Q000503:physiopathology*; D003331:Coronary Vessels / Q000503:physiopathology; D004285:Dogs; D005260:Female; D006339:Heart Rate; D008297:Male; D013997:Time Factors