Abstract 2238: Nitroglycerin Withdrawal Attenuates Coronary Flow Velocity Reserve
Background: Glyceryl trinitrate (GTN) and other organic nitrates play a central role in the treatment of coronary artery disease. However, tolerance and withdrawal associated with GTN use has been reported. It is unknown whether the coronary microcirculation is affected by GTN exposure.
Methods: The study enrolled 13 subjects (60±9 years) with normal coronary arteries confirmed by angiography and without any medications. Before GTN administration, coronary flow velocity reserve (CFVR) in the left anterior descending artery was measured at 3:00 PM by transthoracic Doppler echocardiography with an intravenous infusion of adenosine triphosphate (0.14 mg/kg/min). The ratio of hyperemic to basal averaged diastolic peak velocity (ADPV) was defined as CFVR. Subjects were treated with 5-mg GTN patch, which was applied each evening and replaced every 24 h. After 7 days, the patch was removed at 12:00 AM and the CFVR measurement was repeated during the withdrawal state at 3:00 PM.
Results: Compared with baseline before GTN, there were no significant differences in blood pressure, HR or rate-pressure product during GTN withdrawal. ADPV during GTN withdrawal was not significantly different from baseline (21 ± 6 cm/sec vs.19 ± 5 cm/sec, respectively). Hyperemic ADPV in the withdrawal state (52 ± 12 cm/sec) was significantly decreased compared with baseline (60 ± 15 cm/sec; P<0.05). Consequently, CFVR in the withdrawal state (2.6 ± 0.6) was significantly decreased by 21% compared with baseline (3.3 ± 0.7; P<0.01).
Conclusion: GTN withdrawal attenuates CFVR, which may be partially responsible for adverse cardiac events after sudden discontinuation of GTN therapy.