Unusual vasomotor coronary arterial responses after nitroglycerin

Continuous long-term dosing with oral slow-release isosorbide dinitrate does not reduce incidence of cardiac events in patients with healed myocardial infarction

BACKGROUND

In the short term, isosorbide dinitrate (ISDN) is considered to be therapeutically effective. The long-term effects of treatment with slow-release ISDN are less clear.

HYPOTHESIS

The study was undertaken to investigate the effects of continuous, long-term dosing with oral slow-release ISDN on the incidence of cardiac events in patients with healed myocardial infarction (MI). The study was carried out in accordance with the intention-to-treat principle.

METHODS

In all, 1.102 in- and outpatients, of either gender, with healed MI were randomly divided into groups treated with ISDN (n = 470) and not treated with ISDN (n = 632). Patients in the ISDN group received a continuous regimen of 20 mg of oral, long-acting ISDN three times a day, after meals. The mean observation period was 15.0 +/- 18.5 months. The primary endpoints were nonfatal and fatal recurrent MI, death from congestive heart failure, and sudden death.

RESULTS

There were no significant differences in the baseline characteristics of the patients in the ISDN and no-treatment groups; nevertheless, significantly more patients in the ISDN group experienced cardiac events. In the ISDN group, 35 patients (7.4%) experienced cardiac events during the observation period, versus only 28 patients (4.4%) in the no-treatment group (p < 0.05; odds ratio 1.74; 95% confidence interval 1.04-2.90).

CONCLUSION

Continuous long-term dosing with oral, slow-release ISDN does not reduce and probably increases the incidence of cardiac events among patients with healed MI.

Inhibition of nitrate tolerance without reducing vascular response during eccentric dosing of nitrates

It has been reported that the nitrate tolerance related to continuous dosing of nitrates reduces drug efficacy, and therefore eccentric dosing of nitrates is recommended. In this study, we investigated the appearance of nitrate tolerance related to continuous dosing of nitrates and prevention of nitrate tolerance during eccentric dosing by comparing the grade of coronary dilatation after sublingual nitroglycerin. Of 26 patients with ischemic heart disease who underwent elective cardiac catheterization, 8 patients were continuously administered nitrates, 8 patients were eccentrically administered nitrates, and 10 patients were not treated. We compared the coronary response to sublingual nitroglycerin among the 3 groups. In a coronary vessel without significant stenosis, the coronary vessel area, coronary lumen area, and mean coronary blood flow velocity after sublingual nitroglycerin were measured using intravascular ultrasound (IVUS). In the continuous dosing group, the maximal rate of change in the vessel area after sublingual nitroglycerin was 105 +/- 1 (mean +/- SEM) %, significantly lower than those in the untreated group and the eccentric dosing group (114 +/- 2%, 114 +/- 2%) (p < 0.01, respectively). In conclusion, eccentric dosing of nitrates inhibited the appearance of nitrate tolerance without reducing vascular response.

Eccentric Dosing of Nitrates Does Not Increase Cardiac Events in Patients with Healed Myocardial Infarction

This study was performed to investigate the risk of cardiac events by eccentric or continuous dosing of nitrates in patients with healed myocardial infarction. A total of 573 patients with healed myocardial infarction were assigned to one of two groups: a nitrate-treatment (n =239) and a nontreatment (n =334) group. The nitrate-treatment group was further subdivided into a group receiving eccentric dosing of nitrates (n =153) and a group receiving continuous dosing of nitrates (n =86). The mean observation period was 11.2+/-8.2 months. The cardiac events investigated were nonfatal and fatal recurrent myocardial infarction, death from congestive heart failure, sudden death, worsening angina and rebound angina. Baseline characteristics were also compared among the three groups to determine any effects on outcome. Among the patients receiving eccentric or continuous dosing of nitrates, the rates of cardiac events were 12.7/1,000 person.year and 67.4/1,000 person.year, respectively, whereas the rate was 19.7/1,000 person.year in the nontreated patients. The incidence of cardiac events was significantly greater in patients receiving continuous dosing of nitrates than in the nontreated patients (p <0.05). Continuous dosing of nitrates thus increases cardiac events, and while eccentric dosing of nitrates does not increase them, it is also not effective at preventing them in patients with healed myocardial infarction.

Long-term, continuous treatment with both oral and transdermal nitrates increases cardiac events in healed myocardial infarction patients

This study was performed to investigate the effects of continuous dosing of oral, transdermal (patch), and a combination of the two with nitrate treatments on cardiac events in patients with healed myocardial infarction. In total, 1,291 patients with healed myocardial infarction were assigned 2 groups: treatment with nitrates (n=713) or nontreatment (n=578). Nitrate treatment was subdivided into 3 groups: patch group (n=149), oral group (n=504), and combination group (n=60). The mean observation period was 17.4 +/- 21.1 months. Primary end points were nonfatal and fatal recurrent myocardial infarction, death from congestive heart failure, and sudden death. Baseline characteristics were also compared among the 4 groups to determine any effects on outcome. Among the patients with patch, oral, and combination groups, cardiac events occurred 3.4%, 6.7%, 10.0%, respectively, whereas only 2.9% of the patients treated without nitrates had cardiac events. The incidence of cardiac events was significantly greater in patients with oral nitrates and combination groups compared to patients without nitrates (p<0.01, respectively). Continuous dosing of long-term treatment with both oral and transdermal nitrates increased cardiac events in healed myocardial infarction patients.

Defining the proper role for self-administered sublingual nitroglycerin. A survey of physicians and patients

Within a half-year period, we encountered six cases of patients harmed by the adverse effects of self-administered nitroglycerin--syncope, delayed definitive medical care, and the worsening of nonischemic symptoms. We therefore surveyed 112 patients after a remote myocardial infarction, and 121 cardiologists and internists, regarding the use of sublingual nitroglycerin. Of the physicians, 84 percent routinely prescribed nitroglycerin to patients after a myocardial infarction, and 79 percent of the patients had the tablets available (83 percent of these, at all times). Most patients used the tablets less than once per month, and 37 percent of the patients who always carried nitroglycerin had not used it at all during the preceding year. Although 89 percent of the patients claimed to know when to use the drug, 57 percent had used it or would use it for symptoms such as dizziness, rapid heartbeat, or presyncope. All patients having nitroglycerin claimed it relieved their symptoms, even if the relief was only partial, the time elapsed until relief could not be specified, and the symptoms were of a type unlikely to be relieved by the drug. We suggest that the practice of routinely prescribing nitroglycerin to patients after a myocardial infarction should be reassessed.

Myocardial infarction following sublingual administration of isosorbide dinitrate

A 78-year-old with healed septal necrosis suffered a recurrent myocardial infarction of the anterior wall following the administration of isosorbide dinitrate 5 mg sublingually. After detailing the course of events, we discuss the role of paradoxical coronary spasm and hypotension-mediated myocardial ischemia occurring downstream to significant coronary arterial stenosis in the pathophysiology of acute coronary insufficiency.

Acute myocardial infarction during continuous electrocardiographic ST segment recording. Possible role of bradycardia and hypotension induced by glyceryl trinitrate

A 62 year old man developed an inferior wall myocardial infarction during ambulatory ST segment monitoring. Before the onset of persistent ST segment elevation he had taken several glyceryl trinitrate tablets, which was followed by bradycardia and symptoms of hypotension. Whether a paradoxical reaction to glyceryl trinitrate may have triggered the development of myocardial infarction in this case is uncertain.

Unusual vasomotor coronary arterial responses after reversal of ergonovine induced spasm with glyceryl trinitrate

Unusual vasomotor responses in the coronary arteries occurred in two patients after the administration of glyceryl trinitrate to relieve spasm induced by ergonovine maleate. In one patient after treatment with glyceryl trinitrate and despite dilatation of the adjoining segments a new severe reduction in diameter occurred distally to the segments of the right coronary artery where the ergonovine induced spasm developed. In the other patient the left anterior descending artery filled very slowly after the completely occlusive spasm of the right coronary artery had resolved with glyceryl trinitrate though the circumflex did not. These vasomotor changes were associated with chest discomfort and electrocardiographic abnormalities in both cases. These findings indicate that caution is needed when performing provocative tests even after the ergonovine induced spasm has been reversed with glyceryl trinitrate.

Nitroglycerin-induced coronary vasoconstriction

Nitroglycerin is routinely used during coronary angiography for its vasodilating effects. An unusual case is described in which nitroglycerin induced severe coronary artery spasm. Interpretation of coronary angiograms after nitroglycerin should be made with caution.

Action of intracoronary nitroglycerin in refractory coronary artery spasm

Coronary artery spasm usually responds to sublingual nitroglycerin. This report describes four patients with variant angina and one patient with rest angina who had coronary spasm that was refractory to sublingual or i.v. nitroglycerin. In four patients, spasm occurred spontaneous and in one patient after 0.05 mg of ergonovine. In each case, 25-100 micrograms of intracoronary nitroglycerin promptly (30-45 seconds) resulted in reopacification of the vessel involved in spasm and resolution of evidence for ischemia. Thus, intracoronary nitroglycerin can reverse coronary artery spasm that does not respond to systemic nitroglycerin administration.