Beta-adrenergic blockade and myocardial perfusion in coronary artery disease: differential effects in stenotic versus remote myocardial segments.
Beta-adrenergic blocking agents are widely used in coronary artery disease (CAD), although their impact on myocardial blood flow (MBF) and coronary flow reserve (CFR) remains unclear. We studied the effect of long-term beta-blocker treatment (carvedilol or metoprolol) on coronary microcirculation in CAD patients using PET.


METHODS
Regional and global resting and adenosine-induced hyperemic MBF and CFR were measured with 13N-ammonia and PET in 36 CAD patients before and after 12 wk of oral therapy with either carvedilol, 50 mg/d, or metoprolol, 100 mg/d.


RESULTS
Beta-blockade decreased global resting MBF in proportion to cardiac work (from 0.86 +/- 0.20 to 0.77 +/- 0.14 mL/min/g, P < 0.05) without affecting global hyperemic flow. Hyperemic MBF was significantly lower in stenosis-dependent segments than in remote segments (1.76 +/- 0.64 vs. 2.04 +/- 0.67 mL/min/g, P < 0.05) at baseline but was comparable in both after treatment (2.02 +/- 0.68 vs. 1.90 +/- 0.78 mL/min/g, P = not statistically significant [NS]), resulting in a significant CFR increase in stenotic segments (+15%, P < 0.05) but not in remote segments (+9%, P = NS).


CONCLUSIONS
The beneficial effect of beta-adrenergic blockade can be explained by the reduction in oxygen consumption (= decreased demand) but also by a modest improvement in vasodilator capacity (= increased supply). The improvement in CFR is found predominantly in stenosis-dependent rather than remote segments.
Nuclear Cardiology Section, University Hospital, Zurich, Switzerland.
Pascal
P
Koepfli
Christophe A
CA
Wyss
Mehdi
M
Namdar
Michael
M
Klainguti
Gustav K
GK
von Schulthess
Thomas F
TF
Lüscher
Philipp A
PA
Kaufmann
D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use*; D000641:Ammonia; D002227:Carbazoles / Q000627:therapeutic use*; D002247:Carbon Isotopes; D000077261:Carvedilol; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging* / Q000188:drug therapy*; D003326:Coronary Circulation / Q000187:drug effects; D023921:Coronary Stenosis / Q000000981:diagnostic imaging* / Q000188:drug therapy* / Q000209:etiology; D003331:Coronary Vessels / Q000000981:diagnostic imaging / Q000187:drug effects; D005260:Female; D006801:Humans; D008297:Male; D008790:Metoprolol / Q000627:therapeutic use*; D008875:Middle Aged; D011412:Propanolamines / Q000627:therapeutic use*; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D016896:Treatment Outcome
D000319:Adrenergic beta-Antagonists; D002227:Carbazoles; D002247:Carbon Isotopes; D011412:Propanolamines; D019275:Radiopharmaceuticals; D000077261:Carvedilol; D000641:Ammonia; D008790:Metoprolol