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

Beneficial effects of intracoronary nicorandil on microvascular dysfunction after primary percutaneous coronary intervention: demonstration of its superiority to nitroglycerin in a cross-over study

PURPOSE

In patients undergoing primary percutaneous coronary intervention (PCI) for the treatment of ST-segment elevation myocardial infarction (STEMI), coronary microvascular dysfunction is associated with poor prognosis. Coronary microvascular resistance is predominantly regulated by ATP-sensitive potassium (KATP) channels. The aim of this study was to clarify whether nicorandil, a hybrid KATP channel opener and nitric oxide donor, may be a good candidate for improving microvascular dysfunction even when administered after primary PCI.

METHODS

We compared the beneficial effects of nicorandil and nitroglycerin on microvascular function in 60 consecutive patients with STEMI. After primary PCI, all patients received single intracoronary administrations of nitroglycerin (250 μg) and nicorandil (2 mg) in a randomized order; 30 received nicorandil first, while the other 30 received nitroglycerin first. Microvascular dysfunction was evaluated with the index of microcirculatory resistance (IMR), defined as the distal coronary pressure multiplied by the hyperemic mean transit time.

RESULTS

As a first administration, nicorandil decreased IMR significantly more than did nitroglycerin (median [interquartile ranges]: 10.8[5.2-20.7] U vs. 2.1[1.0-6.0] U, p=0.0002).As a second administration, nicorandil further decreased IMR, while nitroglycerin did not (median [interquartile ranges]: 6.0[1.3-12.7] U vs. -1.4[-2.6 to 1.3] U, p<0.0001). The IMR after the second administration was significantly associated with myocardial blush grade, angiographic TIMI frame count after the procedure, and peak creatine kinase level.

CONCLUSION

Intracoronary nicorandil reduced microvascular dysfunction after primary PCI more effectively than did nitroglycerin in patients with STEMI, probably via its KATP channel-opening effect.

Optimal starting time of acquisition and feasibility of complementary administration of nitroglycerin with intravenous beta-blocker in multislice computed tomography

OBJECTIVES

We determined the optimal starting time of acquisition after sublingual nitroglycerin (NTG) administration and evaluated the effects on multislice computed tomographic (MSCT) images of a complementary administration of sublingual NTG with beta-blocker.

METHODS

Sixty patients who underwent MSCT coronary angiography (CA) were randomly divided into 2 groups as follows: 30 patients given an intravenous administration of beta-blocker (landiolol hydrochloride, mean dose of 0.032 mg/kg per minute; group B); and 30 patients given a coadministration of intravenous beta-blocker and sublingual NTG (0.3 mg; group N). Blood pressure and heart rate were recorded every 1 minute after NTG administration. In addition, the maximum diameters of the proximal and distal lesions in each coronary artery were measured, and the number of assessable segments was calculated.

RESULTS

Blood pressure significantly decreased and heart rate significantly increased 4 minutes after NTG administration. The number of assessable segments was significantly greater in group N than in group B. The maximum diameters of the distal lesions of the left anterior descending and left circumflex arteries and both proximal and distal lesions of the right coronary artery were significantly larger in group N than in group B.

CONCLUSIONS

It is advisable to obtain MSCT images after sublingual NTG administration because nitrates are always given during conventional CA and may prevent beta-blocker-induced coronary spasm. The optimal starting time for MSCT CA is approximately 3 minutes after sublingual NTG administration.

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.

Coronary hemodynamic effects of atrial natriuretic peptide in humans

Studies of the effects of atrial natriuretic peptide on the coronary circulation have yielded conflicting results in animals and have not been fully investigated in human subjects. To further characterize the direct coronary hemodynamic actions of atrial natriuretic peptide in humans and to assess the safety of its administration in patients with coronary artery disease, incremental doses of synthetic atrial natriuretic peptide and nitroglycerin were infused into the left coronary artery in 14 patients, 11 of whom had coronary artery disease. Both agents caused dose-related increases in total coronary sinus blood flow. The largest dose of atrial natriuretic peptide given to all patients (100 micrograms) increased mean coronary sinus blood flow from 127 +/- 7 to 149 +/- 9 ml/min (p less than 0.05) and decreased coronary vascular resistance from 0.93 +/- 0.07 to 0.81 +/- 0.05 mm Hg/ml per min (p less than 0.05); mean arterial blood pressure and heart rate were not affected by this dose of atrial natriuretic peptide. The greatest changes in coronary sinus blood flow (+25%) and coronary vascular resistance (-18%) after atrial natriuretic peptide administration occurred in the patients with coronary artery disease and no other associated cardiovascular disease. The maximal effects of atrial natriuretic peptide were similar to those of nitroglycerin, and no untoward effects were observed. Thus, atrial natriuretic peptide is a direct coronary vasodilator in humans. Its maximal dose effects are similar to those of nitroglycerin and were well tolerated in this small group of patients. The physiologic importance and therapeutic potential of atrial natriuretic peptide in patients with coronary artery disease merit further investigation.

Changes in diameter of coronary narrowings and translesional hemodynamics after intracoronary nitroglycerin

The effect of intracoronary nitroglycerin on coronary stenosis dimensions and translesional hemodynamics was evaluated in 38 subjects (74 stenoses) referred for diagnostic coronary arteriography. Quantitative coronary arteriography was performed with standard Newtonian fluid dynamic equations used to estimate transstenotic gradients. Since intracoronary nitroglycerin can induce significant myocardial hyperemia (increased flow velocity), with increased translesional pressure gradients and a decrease in distal intraluminal pressure, the potential effect on subendocardial flow distribution was also analyzed. Minimum stenotic diameter significantly increased postnitroglycerin (NTG) (preNTG 1.42 vs postNTG 1.82 mm, p less than 0.01), with a decrease in relative percent diameter stenosis (preNTG 45.7 vs postNTG 40.7%, p less than 0.05). When changes in minimum stenotic diameter were analyzed according to stenosis severity (quartiles), the greatest effect was noted in those lesions with the least severe stenosis (quartile no. 1, 0.49 vs quartile no. 4, 0.32 mm, p less than 0.05). If coronary blood flow velocity remains at baseline values (4 cm/s), intracoronary nitroglycerin was predicted to significantly decrease transstenotic pressure gradients (preNTG 1.01 vs postNTG 0.82 mm Hg, p less than 0.05), with the greatest change shown in severe lesions (quartile no. 4, preNTG 3.79 to postNTG 2.28 mm Hg, p less than 0.01). Accelerated coronary flow velocity (myocardial hyperemia) increased calculated translesional pressure gradients (4 cm/s, 0.82 mm Hg vs 20 cm/s, 8.00 mm Hg, p less than 0.01), despite simultaneous stenotic vasodilation. Hemodynamic obstruction was particularly dependent on coronary flow velocity in the most severe stenoses (quartile no. 4, 4 cm/s, 2.28 vs 20 cm/s, 28.78 mm Hg, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Impaired coronary vasodilator reserve in the immediate postcoronary angioplasty period: analysis of coronary artery flow velocity indexes and regional cardiac venous efflux

The ratio of peak hyperemic/basal mean coronary flow velocity, an index of coronary vasodilator reserve, immediately after coronary angioplasty normalizes in less than 50% of patients. To evaluate other indexes of coronary vasodilator capacity, both intracoronary arterial velocity and cardiac venous efflux were measured at rest and during vasodilator-induced coronary hyperemia (intracoronary nitroglycerin and papaverine) before and after angioplasty in 27 patients; 17 patients had measurements of intracoronary velocity alone and 10 had thermodilution measurements of great cardiac vein flow. Coronary flow velocity responses were also measured in 6 angiographically normal segments in patients undergoing angioplasty and in 10 normal left coronary artery segments in patients with normal coronary arteries or isolated right coronary artery disease. Despite significant angiographic (72 +/- 12 to 23 +/- 11% diameter narrowing) and hemodynamic (49 +/- 12 to 19 +/- 12 mm Hg aortocoronary gradient) improvement, coronary vasodilator reserve ratios for both arterial velocity and venous flow after angioplasty were only minimally affected. Angioplasty did not significantly increase rest coronary vein flow or artery flow velocities, but did result in significantly higher papaverine responses after angioplasty. Mean and phasic coronary velocity, diastolic coronary flow velocity integral and measured great cardiac vein flow ratios were significantly lower when compared with those in 16 angiographically normal coronary artery segments. These data indicate that maximal hyperemic coronary flow velocity is increased after angioplasty, but the reserve ratios, calculated by any of several flow velocity indexes, remain minimally improved. Angiographic correlations (percent coronary diameter, absolute diameter or cross-sectional area) with variables of coronary blood flow or velocity suggest that no single variable is useful in assessing angioplasty results. However, postangioplasty arterial mean velocity and diastolic flow velocity integral are nearly normalized in most patients, whereas relative changes remain attenuated. These findings are important in studies assessing coronary vasomotor responses in patients with atherosclerotic coronary disease, especially after angioplasty.

Effects of nitroglycerin and nifedipine on coronary and systemic hemodynamics during transient coronary artery occlusion

Nitroglycerin (NTG) and nifedipine (NIF) have the potential to augment coronary blood flow in addition to reducing peripheral determinants of myocardial oxygen demand as a synergistic protective mechanism during ischemia. To examine these effects, systemic and coronary hemodynamic responses were measured continuously before and during brief periods of myocardial ischemia induced by left anterior descending coronary balloon occlusion in 26 patients undergoing angioplasty (PTCA). Data were compared for two matched occlusion periods, one control and one "drug" occlusion. In 17 patients (NTG group), 200 micrograms of intracoronary NTG was given immediately before coronary occlusion. In nine patients (NIF group), 10 mg of sublingual NIF was given 15 minutes before the "drug" occlusion. NTG significantly but transiently reduced mean arterial pressure (91 +/- 11 to 82 +/- 15 mm Hg, p less than 0.05) and augmented basal coronary blood flow (95 +/- 38 to 127 +/- 54 ml/min, p less than 0.05) but did not alter great vein blood flow (59 +/- 29 vs 61 +/- 29 ml/min) or coronary occlusion pressure (25 +/- 7 to 24 +/- 7 mm Hg) during ischemia. NIF significantly reduced systolic, diastolic, and mean arterial pressure (119 +/- 21 to 95 +/- 8 mm Hg, p less than 0.001) and heart rate-pressure product from control. NIF maintained basal great vein blood flow (125 +/- 41 to 106 +/- 57 ml/min) during reduced myocardial oxygen demand, but did not affect great vein blood flow (73 +/- 29 to 79 +/- 37 ml/min) or coronary occlusion pressures during ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of beta-adrenergic blockade on nitroglycerin-induced augmentation of regional coronary blood flow in patients

Although beta-adrenergic blockade may increase coronary vascular resistance in some patients with severe ischemic heart disease, the effects of beta blockade on the nitroglycerin (NTG)-induced augmentation of coronary blood flow have not been elucidated. Therefore, systemic hemodynamic and anterior left ventricular regional coronary blood-flow (thermodilution) data were measured during administration of NTG into the left coronary artery, before and 10 min after intravenous propranolol (0.1 mg/kg) in 22 patients. Six patients (Group 1) had normal left coronary arteries and nine (Group 2) had severe coronary artery disease with at least greater than 70% narrowing of the left anterior descending artery. In seven additional patients (three without and four with greater than 70% left anterior descending coronary artery disease), measurements were obtained with constant-paced heart rates (Group 3). Before beta blockade, NTG (200 mcg) significantly increased anterior regional great-vein flow [for Group 1, 84 +/- 38% (81 +/- 20 to 140 +/- 60 ml/min); Group 2, 39 +/- 41% (61 +/- 26 to 83 +/- 38 ml/min); and Group 3, 87 +/- 55% (75 +/- 36 to 144 +/- 86 ml/min)]. In Groups 1 and 2, beta-adrenergic blockade reduced heart rate 10% (p less than 0.01) but did not affect mean arterial or pulmonary artery pressures.(ABSTRACT TRUNCATED AT 250 WORDS)

Nitroglycerin-induced coronary vasodilatory responses in patients during isometric handgrip exercise

Intracoronary nitroglycerin is frequently administered during invasive procedures such as coronary angioplasty or thrombolysis which may be associated with pain and sympathetic neural stimulation. Whether sympathetic-mediated reflex vasoconstriction interferes with nitroglycerin-induced augmentation of coronary blood flow is unknown. Therefore, coronary and systemic hemodynamics were measured in 19 patients during isometric handgrip exercise (3 min x 25% maximal effort), during intracoronary nitroglycerin, and during handgrip plus intracoronary nitroglycerin. Nine patients had no significant left anterior descending coronary artery stenosis (group 1) and ten patients had greater than 70% left anterior descending coronary artery stenosis (group 2). Handgrip exercise increased heart rate, mean arterial pressure, and coronary sinus and great vein flow 15% while increasing coronary resistance 10%. Intracoronary nitroglycerin (200 micrograms) reduced mean arterial pressure -4 +/- 6% and increased great cardiac vein flow 35-72%. Anterior left ventricular regional coronary flow responses to intracoronary nitroglycerin were unaffected by sympathetic stimulation for group 1. Group 2 had a greater increase in great vein flow with intracoronary nitroglycerin plus handgrip compared to nitroglycerin alone due to increased mean arterial pressure with no change in the great vein resistance. These data indicate that sympathetic stimulation does not alter the nitroglycerin-induced augmentation of coronary sinus and great vein blood flow in patients with and without significant left anterior descending coronary artery stenosis. In patients undergoing invasive interventions who may have increased circulating catecholamines, mild sympathetic (isometric) stimulation does not appear to interfere with the coronary vasodilatory responses to intracoronary nitroglycerin.

Attenuation of nitroglycerin-induced coronary hyperemic blood flow in patients with left anterior descending coronary collaterals

Although intracoronary nitroglycerin (NTG) is frequently administered to patients having occluded coronary arteries undergoing invasive procedures such as percutaneous transluminal coronary angioplasty or thrombolysis, the extent of NTG-induced augmentation of myocardial blood flow in patients with collaterally filled occluded arteries is incompletely understood. To examine NTG-induced increases in coronary blood flow in patients with occluded left anterior descending coronary arteries (LAD), coronary and systemic hemodynamics were measured during bolus administration of NTG into the left coronary artery in 10 patients with normal LAD (Group 1), 11 patients with greater than 70% and less than 100% narrowing of the LAD (Group 2), and 10 patients who had total occlusion of the LAD with angiographic collateral filling and anterior ventricular wall motion abnormalities (Group 3). NTG increased anterior regional great vein flow (thermodilution) from 72 +/- 19 to 140 +/- 60 ml/min (p less than 0.05), 67 +/- 27 to 108 +/- 66 ml/min (p less than 0.05), and 59 +/- 27 to 74 +/- 36 ml/min (p = NS vs. control, p less than 0.05 vs. peak flow for Group 1) with relative increases from control of 91 +/- 41%, 56 +/- 34%, and 25 +/- 22% for the three groups, respectively. The percent change for Group 3 was significantly lower than both Groups 1 (p less than 0.01) and 2 (p less than 0.05). These data indicate that myocardial hyperemic blood flow responses to intracoronary NTG are markedly attenuated in patients with occluded but collaterally supplied vessels. During invasive procedures in these patients, although significantly attenuated, intracoronary NTG may potentially provide a beneficial effect by augmenting blood flow through collaterals or in adjacent regions.

Effect of nicardipine on determinants of myocardial ischemia occurring during acute coronary occlusion produced by percutaneous transluminal coronary angioplasty

In 10 patients undergoing percutaneous transluminal coronary angioplasty of the left anterior descending coronary artery (LAD), the clinical, electrocardiographic and hemodynamic effects of acute intravenous calcium channel antagonism with nicardipine (2 mg over 1 minute, followed by a constant infusion of 25 to 50 micrograms/min) were assessed during temporary LAD occlusion. Onset of myocardial ischemia during coronary occlusion was prevented or delayed after administration of nicardipine in 7 of the 10 patients. During infusion of nicardipine and during LAD occlusion, residual great cardiac vein blood flow increased in 9 of 10 patients compared with residual flow during occlusion before nicardipine (10%, p less than 0.05). Nicardipine also decreased mean aortic pressure, but was associated with a reflex-mediated increase in heart rate. Overall, the double product, an index of global myocardial oxygen demand, decreased 7% (p less than 0.05). Thus, nicardipine usually diminished ischemia induced by acute transient coronary occlusion by increasing collateral flow while oxygen demand decreased.