Downstream resistance effects of intracoronary thrombosis in the stenosed canine coronary artery.
OBJECTIVE
The presence is well established in unstable angina of intracoronary thrombosis in a stenosed epicardial coronary artery. The effects of the thrombus formation on the distal microcirculation are however still unclear.


METHODS
We adapted the Folts canine model of left circumflex coronary arterial stenosis and intracoronary thrombosis by the insertion of a pressure catheter distal to the stenosis and by the use of 15 microns radioactive microspheres for measurement of regional myocardial blood flow. This permitted measurement during circumflex artery occlusion of collateral flow, downstream vascular resistance and collateral resistance.


RESULTS
Distal circumflex resistance, obtained by dividing the distal circumflex coronary pressure gradient by the collateral flow, significantly increased with thrombosis (94.47 +/- 35.72 to 120.06 +/- 34.47; p = 0.0018) mmHg/ml/min/g. Changes in collateral flow and resistance in the presence of thrombosis, during maximum ischaemic vasodilatation, were inconsistent.


CONCLUSIONS
Thrombosis causes increased vascular resistance in the microcirculation distal to the site of injury. This may be of clinical relevance in unstable angina, characterised by episodes of thrombus growth and embolization, in which ischaemic episodes may be worsened by generalised downstream vascular changes.
Mansaray
M
M
National Heart and Lung Institute, Imperial College School of Medicine, Charing Cross Hospital, London, UK. m.mansaray@cxwms.ac.uk
Belcher
P R
PR
Vergroesen
I
I
Wright
Z M
ZM
Hynd
J W
JW
Drake-Holland
A J
AJ
Noble
M I
MI
D000789:Angina, Unstable / Q000503:physiopathology; D000818:Animals; D003097:Collateral Circulation; D003326:Coronary Circulation; D003328:Coronary Thrombosis / Q000503:physiopathology*; D003331:Coronary Vessels / Q000503:physiopathology*; D004285:Dogs; D005260:Female; D008297:Male; D008954:Models, Biological; D014655:Vascular Resistance