Alterations in regional myocardial blood flow after nitroprusside and nitroglycerin in patients with and without significant coronary artery disease

Additive effects of nicorandil on coronary blood flow during continuous administration of nitroglycerin

OBJECTIVES

We examined whether patients with ischemic heart disease (IHD) should be treated with nicorandil, an adenosine triphosphate-sensitive potassium channel opener, in addition to the regular use of nitrates.

BACKGROUND

It has been reported that nicorandil possibly has additive effects on nitroglycerin (NTG) treatment for angina, but the mechanism is not clear.

METHODS

We directly measured anterograde coronary blood flow (CBF) with a Doppler guide wire to examine the effects of intravenous administration of NTG (0.3 mg) and nicorandil (6 mg) during continuous administration of NTG at a sufficient dose (25 microg/min) in subjects with normal and stenotic coronary arteries.

RESULTS

Additional systemic administration of NTG decreased anterograde CBF (normal -19.7%; stenotic -21.2%). In contrast, nicorandil increased anterograde CBF in both normal (54.6%) and stenotic (89.6%) coronary arteries, without the coronary steal phenomenon. There was a tendency toward nicorandil-dilated diameters in the patients with stenotic arteries (p = 0.06). There were no effects of additional administration on pulmonary artery wedge pressure. There was no difference in changes in heart rate and mean aortic blood pressure between NTG and nicorandil therapy.

CONCLUSIONS

These results suggest that in patients treated with nitrates, additional administration of nicorandil is more useful, in terms of increasing CBF, than additional administration of nitrates. Adjunctive use of nicorandil with nitrates may provide the further benefit of myocardial protection and may improve the prognosis of patients with IHD.

The effect of nitroglycerin on pacing-induced changes in myocardial oxygen consumption and metabolic coronary vasodilation in patients with coronary artery disease

In the present study, we assessed the potential effect of nitroglycerin IV (NTG), a donor of exogenous nitric oxide, on metabolic coronary flow control in patients with coronary artery disease. In 12 patients scheduled for coronary artery surgery, arterial blood pressure, pulmonary capillary wedge pressure, coronary sinus blood flow (continuous thermodilution), myocardial oxygen supply (DVO2), and myocardial oxygen consumption (MVO2) were measured at sinus rhythm and in response to atrial pacing at 30 bpm greater than baseline sinus rate. These measurements were repeated during infusion of NTG 1 and 2 microg x kg(-1) x min(-1). At control, in the absence of NTG, MVO2 increased from 13.7 +/- 3.4 mL O2/min during sinus rhythm to 19.3 +/- 5.5 mL O2/min during pacing. NTG 1 and 2 microg x kg(-1) x min(-1) blunted the pacing-induced increase in MVO2 dose-dependently. During NTG 1 microg x kg(-1) x min(-1), MVO2 increased from 12.9 +/- 3.3 mL O2/min at sinus rhythm to 17.3 +/- 4.7 mL O2/min during pacing (P = 0.01 versus control pacing); during NTG 2 microg x kg(-1) x min(-1), MVO2 increased from 13.4 +/- 3.3 mL O2/min to 15.9 +/- 3.7 mL O2/min (P = 0.008 versus control pacing). However, the pacing-induced increase in DVO2 per mL O2/min increase in MVO2 (delta DVO2/delta MVO2), was significantly greater during the infusion of NTG 2 microg x kg(-1) x min(-1) (1.85 +/- 0.56; P = 0.023) compared with control (1.51 +/- 0.22). This was associated with an increase in coronary sinus hemoglobin oxygen saturation (30% +/- 5% at control pacing and 34% +/- 6% during pacing with NTG 2 microg x kg(-1) x min(-1); P = 0.018), which indicates that during the infusion of NTG, there was more metabolic coronary vasodilation than achievable solely on the basis of the metabolic stimulus.

IMPLICATIONS

Our findings suggest that nitroglycerin, a donor of exogenous nitric oxide, reduces pacing-induced increases in myocardial oxygen consumption and enhances metabolic coronary vasodilation in patients with coronary artery disease, in whom endogenous nitric oxide activity may be reduced.

Myocardial effects of adenosine- and sodium nitroprusside-induced hypotension: a comparative study in patients anaesthetized for abdominal aortic aneurysm surgery

The effects of adenosine and sodium-nitroprusside (SNP) on central and myocardial haemodynamics and metabolism were evaluated during fentanyl anaesthesia (100 micrograms.kg-1) in six patients with peripheral vascular disease. The investigation was performed during stable anaesthesia, before scheduled abdominal aortic graft surgery. Adenosine and SNP were infused intravenously in random order over 20 min, leaving a 30-min control period in between. The vasodilators were titrated in order to reduce mean arterial pressure by approximately 25%. Adenosine (90 +/- 20 micrograms.kg-1.min-1) reduced mean arterial pressure from 10.9 +/- 0.3 to 8.4 +/- 0.4 kPa (82 +/- 3 to 63 +/- 3 mmHg), and SNP (0.7 +/- 0.1 micrograms.kg-1.min-1) from 11.0 +/- 0.2 to 8.4 +/- 0.3 kPa (83 +/- 3 mmHg to 63 +/- 3 mmHg), during the hypotension period. Cardiac index remained unaffected during induced hypotension with both vasodilators, while heart rate increased during SNP infusion (8 +/- 3%) and remained unaffected with adenosine. Left ventricular stroke work index and myocardial oxygen consumption decreased during SNP infusion (33 +/- 3% and 17 +/- 5%, respectively), while these parameters were unchanged with adenosine. Adenosine hypotension increased coronary sinus flow 1-2 fold (128 +/- 26%), together with increased coronary sinus oxygen content (96 +/- 11%). In contrast, coronary sinus flow decreased during SNP hypotension (-15 +/- 4%) with unaffected coronary sinus oxygen content. It is concluded that adenosine, in contrast to SNP, is associated with a hyperkinetic myocardial circulation.