Comparison of the effects of nitroprusside and nitroglycerin on coronary size

Coronary Hyperemic Dose Responses of Intracoronary Sodium Nitroprusside

Background— Sodium nitroprusside is one of several agents considered effective for treating the no-reflow phenomenon during acute coronary interventions. However, the coronary hyperemic dose responses and systemic hemodynamic effects of intracoronary nitroprusside have yet to be determined in humans. The purpose of this study was to compare the hyperemic and hemodynamic responses of intracoronary nitroprusside to intracoronary adenosine in patients during cardiac catheterization with angiographically normal anterior descending arteries.

Methods and Results— In 21 patients, coronary blood flow velocity (0.014-inch Doppler flow wire), heart rate, and blood pressure were measured in unobstructed left anterior descending coronary arteries at rest, after intracoronary adenosine (30- to 50-μg boluses), and after 3 serial doses (0.3-, 0.6-, and 0.9-μg/kg boluses) of intracoronary nitroprusside. Coronary reserve was calculated as hyperemia/basal coronary flow velocity. In an additional 9 patients with intermediate stenoses (53±7%), 14 fractional flow reserve (FFR) measurements (using 0.014-inch pressure wire) were performed with both intracoronary adenosine and nitroprusside (0.6 μg/kg). Intracoronary nitroprusside produced equivalent coronary hyperemia with a longer duration (≈25%) compared with intracoronary adenosine. Intracoronary nitroprusside (0.9 μg/kg) decreased systolic blood pressure by <20%, with minimal change in heart rate, whereas intracoronary adenosine had no effect on these parameters. FFR measurements with intracoronary nitroprusside were identical to those obtained with intracoronary adenosine ( r =0.97).

Conclusions— Compared with adenosine, intracoronary nitroprusside produces an equivalent but more prolonged coronary hyperemic response in normal coronary arteries. Intracoronary nitroprusside, in doses commonly used for the treatment of the no-reflow phenomenon, can produce sustained coronary hyperemia without detrimental systemic hemodynamics. On the basis of FFR measurements compared with adenosine, sodium nitroprusside also appears to be a suitable hyperemic stimulus for coronary physiological measurements.

Dose-related effects of intracoronary nitroglycerin on coronary hyperemia in patients with coronary artery disease

Although intracoronary nitroglycerin (NTG) is frequently required during percutaneous transluminal coronary angioplasty or thrombolysis, the dose-related hemodynamic effects and the extent to which intracoronary NTG--induced coronary hyperemia is limited in patients with coronary artery disease have not been defined. Therefore, we studied 19 patients with coronary artery disease (nine with no or minimal luminal narrowing of the left anterior descending coronary artery [group 1] and 10 with significant left anterior descending coronary stenosis [group 2]; mean arterial pressure and thermodilution coronary sinus and great cardiac vein blood flow were measured during bolus administrations of 50, 200, and 300 micrograms of intracoronary NTG. During the NTG-induced hyperemia, mean arterial pressure decreased 0%, 4% (both p = NS), and 6% (p less than 0.05) after 50, 200, and 300 micrograms doses, respectively. heart rate did not change. Global coronary hyperemia was greatest for 200 micrograms with coronary blood flow increasing (74 +/- 32% in group 1 and 53 +/- 25% for group 2) but was significantly different from 50 micrograms only in group 2 patients. Moreover, the regional coronary blood flow responses were attenuated in group 2 compared to group 1 for 50 micrograms, 18 +/- 13% vs 38 +/- 18%, and for 200 micrograms, 35 +/- 15% vs 72 +/- 34% (both p less than 0.05), with the reduction of regional coronary resistance in group 2 attenuated for all three doses of intracoronary NTG. The 300 micrograms dose did not provide further augmentation of either global or regional coronary blood flow or greater reduction in coronary resistance.(ABSTRACT TRUNCATED AT 250 WORDS)

Functional differences in blood vessels determined from studies with calcium-channel blockers. Functional changes in forearm resistance vessels of men with primary hypertension

Vascular smooth muscle is activated through 2 major systems. One, which can be inhibited by calcium-entry blocking agents, involves the influx of calcium through potential-sensitive channels. The other, which can be inhibited by sodium nitroprusside, involves the entry of calcium through agonist-controlled channels and probably its mobilization from within the cell as well. Human veins, muscular arteries and resistance vessels show differing patterns of response to agents that selectively inhibit the 2 activation systems. The responses indicate that physiologic contractions of cutaneous veins and muscular arteries depend on the agonist-controlled system; contractions of veins induced by high concentrations of potassium depend on the potential-sensitive system as, probably, does local spasm in arteries. The tone of resistance vessels depends on a balance between the potential-sensitive and agonist-controlled systems. The forearm resistance vessels of men with primary hypertension respond to verapamil with larger-than-normal dilatation compared with that induced by nitroprusside. This is interpreted as showing an increased contribution to resistance vessel tone from the potential-sensitive system. This functional abnormality does not depend on the inhibition of sodium pump activity that is known to occur in hypertension, because it cannot be reproduced by local infusion of ouabain. It probably results from a primary disorder of calcium handling by the cell membrane.

Comparison of coronary hemodynamic effects of nitroprusside and sublingual nitroglycerin with anterior descending coronary arterial occlusion

This study compares the coronary hemodynamic effects of an infusion of nitroprusside and of sublingual nitroglycerin in the same patients. The coronary hemodynamic responses of the anterior left ventricular (LV) region to both drugs were studied in 9 patients whose anterior descending branch of the left coronary artery was filled by collaterals. Before and during administration of each drug (given in doses designed to produce similar changes in LV diastolic pressure), heart rate, LV and aortic pressure, and anterior regional flow, oxygen delivery and lactate metabolism were measured. Given in this manner, as expected, both drugs decreased the double product of heart rate and systolic pressure. Concomitant with these changes, anterior regional blood flow increased or decreased modest amounts or did not change with either drug. Similar directional flow changes or no change occurred in 6 patients and directionally different changes in the other 3 patients. The ratio of mean aortic pressure or of the double product to anterior regional flow consistently decreased during the administration of both drugs. Additionally, anterior regional myocardial oxygen uptake remained similar during both drug periods compared with control values. Anterior region lactate extraction was abnormal (less than 10%) in 4 of the 9 patients during the initial control period. Lactate extraction was usually normal during both the nitroprusside and the nitroglycerin periods. In general, coronary hemodynamic values were remarkably similar during both of these periods. Thus, although relative differences in systemic arterial and venous dilation were obtained with nitroprusside and nitroglycerin, similar and beneficial coronary hemodynamic changes generally occurred.