Impairment of the myocardial vasomotor response to cold pressor stress in collateral dependent myocardium.
OBJECTIVE
To study the vasomotor response (cold pressor/basal flow) in myocardium perfused entirely by collaterals, using the reflex sympathetic stimulation of cold pressor stress.


METHODS
Regional myocardial blood flow was measured in collateral dependent and in remote myocardium using positron emission tomography with 15O water at basal and at cold pressor stress. Regional ischaemia was measured with 18F-fluorodeoxyglucose (FDG).


METHODS
Nine patients (mean (SD) age 53 (6) years) with an occluded coronary artery supplied entirely by collaterals from other angiographically normal arteries.


RESULTS
In remote myocardium, basal and cold pressor flow were 0.99 (0.26) and 1.46 (0.60) ml/min/g (P < 0.05), respectively, a myocardial vasomotor response of 1.46 (0.45). In collateral dependent myocardium, basal and cold pressor flow were 0.91 (0.20) and 0.87 (0.35) ml/min/g, respectively (the latter value, P < 0.05 v remote region), a myocardial vasomotor response of 0.97 (0.43) (P < 0.05 v remote region). The myocardial vascular resistance (mean arterial pressure/flow) during cold pressor was higher in the collateral dependent than in remote myocardium, at 147.0 (61.1) and 85.6 (32.3) mm Hg.min.g/ml (P < 0.05), respectively, but with no relative increase in FDG uptake.


CONCLUSIONS
In contrast to the decrease in myocardial resistance in remote myocardium with cold pressor, an increase was observed in collateral dependent myocardium suggesting a vasoconstrictor response in resistive vessels, without demonstrable myocardial ischaemia.
Uren
N G
NG
Department of Medicine, Hammersmith Hospital, London, United Kingdom.
Crake
T
T
Tousoulis
D
D
Seydoux
C
C
Davies
G J
GJ
Maseri
A
A
D003080:Cold Temperature; D003097:Collateral Circulation; D003327:Coronary Disease / Q000000981:diagnostic imaging / Q000503:physiopathology*; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012018:Reflex; D013312:Stress, Physiological; D014055:Tomography, Emission-Computed; D014655:Vascular Resistance / Q000502:physiology; D014661:Vasoconstriction / Q000502:physiology; D014666:Vasomotor System / Q000503:physiopathology*