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Systemic nitric oxide synthase inhibition improves coronary flow reserve to adenosine in patients with significant stenoses

¹Medical Research Council Clinical Sciences Center, Imperial College, Hammersmith Hospital, London, United Kingdom; ²Cardiovascular Center, Nuclear Cardiology, University Hospital, Zurich; and ³Zurich Center for Integrative Human Physiology, University of Zurich, Switzerland

Submitted 26 November 2006 ; accepted in final form 27 July 2007

We studied the impact of systemic infusion of the nitric oxide synthase (NOS) inhibitor N^G-monomethyl-L-arginine (L-NMMA) on coronary flow reserve (CFR) in patients with coronary artery disease (CAD). We have previously demonstrated that CFR to adenosine was significantly increased after systemic infusion of L-NMMA in normal volunteers but not in recently transplanted denervated hearts. At baseline, myocardial blood flow (MBF; ml·min^–1·g^–1) was measured at rest and during intravenous administration of adenosine (140 µg·kg^–1·min^–1) in 10 controls (47 ± 5 yr) and 10 CAD patients (58 ± 8 yr; P < 0.01 vs. controls) using positron emission tomography and ¹⁵O-labeled water. Both MBF measurements were repeated during intravenous infusion of 10 mg/kg L-NMMA. CFR was calculated as the ratio of MBF during adenosine to MBF at rest. CFR was significantly higher in healthy volunteers than in CAD patients and increased significantly after L-NMMA in controls (4.00 ± 1.10 to 6.15 ± 1.35; P < 0.0001) and in patients, both in territories subtended by stenotic coronary arteries (>70% luminal diameter; 2.06 ± 1.13 to 3.21 ± 1.07; P < 0.01) and in remote segments (3.20 ± 1.23 to 3.92 ± 1.62; P < 0.05). In conclusion, CFR can be significantly increased in CAD by a systemic infusion of L-NMMA. Similarly to our previous findings in normal volunteers, this suggests that adenosine-induced hyperemia in CAD patients is constrained by a mechanism that can be relieved by systemic NOS inhibition with L-NMMA.

coronary circulation; autonomic nervous system; ischemic heart disease; cardiac imaging; positron emission tomography

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