Failure of protective effect of captopril and enalapril on exercise and dipyridamole-induced myocardial ischemia

Effect of losartan in treatment of exercise-induced myocardial ischemia

Because no controlled clinical studies are available about the possible role of angiotensin II receptor blockers in preventing effort myocardial ischemia, we evaluated the effect of angiotensin II receptor blocker/losartan in preventing exercise-induced myocardial ischemia in patients with coronary artery disease. Twenty-four sedentary patients with chronic stable ischemia were prospectively randomized to 28 days (double blind) of losartan 100 mg or losartan placebo in 2 divided doses. In each patient the treatment was crossed over to the alternative regimen (28 days, double blind) after a 1-week placebo period (single blind). At the end of each phase a new exercise stress test was performed. At baseline, systolic blood pressure was significantly decreased after losartan 100 mg compared with losartan placebo. At submaximal exercise, systolic blood pressure and rate-pressure product were lower after losartan 100 mg administration compared with losartan placebo, and these findings remained significant at 1-mm ST depression and at peak exercise. Losartan 100 mg administration versus losartan placebo significantly delayed the time to 1-mm ST-depression onset and decreased ST-segment depression at peak exercise and time to recovery of ST-segment depression. Losartan 100 mg administration compared with losartan placebo was able to significantly increase exercise duration and maximal workload during exercise stress testing. In conclusion, in our study, losartan decreased electrocardiographic parameters of myocardial ischemia in patients with coronary artery disease, suggesting a possible role of this drug in treatment of patients with effort myocardial ischemia.

Angiotensin II-Receptor Antagonist Losartan Does not Prevent Nitroglycerin Tolerance in Patients with Coronary Artery Disease

The study evaluated the effect of Losartan in preventing nitrate tolerance during continuous transdermal nitroglycerin (TD-GTN) therapy in patients with coronary disease. Fifteen subjects with chronic stable ischemia evaluated by exercise test, were randomized to 28 days of TD-GTN 20 mg once a day without free interval plus Losartan 100 mg or Losartan-placebo with a double blind crossover design. Myocardial ischemic parameters during stress test were evaluated after each test period and results of Losartan therapy were compared to those with placebo. Time to onset 1 mm ST-depression was significantly higher after acute TD-GTN 20 mg with respect to placebo run-in, sustained TD-GTN 20 mg plus Losartan 100 mg or Losartan-placebo (p < 0.001). ST-depression at peak exercise and time to recovery of ST segment were markedly lower after acute TD-GTN 20 mg compared to placebo run-in (p < 0.05), sustained TD-GTN 20 mg plus Losartan 100 mg (p < 0.001) or Losartan-placebo (p < 0.05). At 1 mm-ST depression and at peak exercise, systolic blood pressure and rate-pressure product significantly decreased after sustained TD-GTN 20 mg plus Losartan 100 mg (p < 0.001, p < 0.05 respectively) with respect to placebo run-in, acute and sustained TD-GTN 20 mg plus Losartan-placebo. Moreover at peak exercise, these data were also observed after acute TD-GTN 20 mg compared to placebo run-in and sustained TD-GTN 20 mg plus Losartan-placebo (p < 0.001). The AT(1) antagonist Losartan administration does not prevent the development of nitrate tolerance during continuous TD-GTN therapy.

Anti-ischemic therapy and stress testing: pathophysiologic, diagnostic and prognostic implications

Anti-ischemic therapy, in particular beta-blockers, is the most commonly employed drug for the control of myocardial ischemia in patients with stable coronary artery disease. Its widespread use also in patients with suspected coronary artery disease has important practical, clinical diagnostic and prognostic implications because diagnostic tests are heavily influenced by its effects. In the present review, the pathophysiological mechanisms of ischemia protection by antianginal therapy are described. Not all stressors are created equal in front of the different classes of antianginal drugs and on their turn the different classes of drugs exert different levels of protection on inducible ischemia. Several clinical implications can be drawn: From the diagnostic viewpoint antianginal therapy decreases test sensitivity, offsetting the real ischemic burden for a too high percentage of false negative tests. From the prognostic viewpoint test positivity in medical therapy identifies a group of subjects at higher risk of experiencing cardiac death and positivity on medical therapy can be considered a parameter of ischemia severity. Nonetheless in patients with known coronary artery disease the ability of antianginal therapy to modify the ischemic threshold at stress testing represent a powerful means to assess therapy efficacy. From a practical viewpoint, the use of antianginal therapy at time of testing has advantages and disadvantages which are largely dependent on the purpose a test is performed: if the purpose of testing is to diagnose ischemia, it should be performed in the absence of antianginal medications. If the purpose of testing is to assess the protective effects of antianginal therapy, the test should be performed on medications.

No effects on myocardial ischaemia in patients with stable ischaemic heart disease after treatment with ramipril for 6 months

OBJECTIVE: To assess the effects of a 6-month angiotensin-converting enzyme (ACE) inhibitor intervention on myocardial ischaemia. METHOD: We randomized 389 patients with stable coronary artery disease to double-blind treatment with ramipril 5 mg/day (n = 133), ramipril 1.25 mg/day (n = 133), or placebo (n = 123). Forty-eight-hour ambulatory electrocardiography was performed at baseline, and after 1 and 6 months. RESULTS: Relevant baseline variables were similar in all groups. Changes over 6 months in duration of >/= 1 mm ST-segment depression (STD), total ischaemic burden and maximum STD did not differ significantly between the treatment groups. There was no difference in the frequency of adverse events between the groups. CONCLUSION: ACE inhibitor treatment has little impact on incidence and severity of myocardial ischaemia in patients with stable ischaemic heart disease.

Echo-dipyridamole stress test evaluation of isosorbide-5-mononitrate efficacy and tolerance in patients with coronary heart disease: interplay with sympathetic activity

In 22 patients with stable myocardial ischemia, we prospectively studied the short- and long-term effects of isosorbide-5-mononitrate (5-ISMN) on dipyridamole-induced myocardial ischemia, the ability of dipyridamole-stress echocardiography to evaluate nitrate tolerance, and the role of activation of the neurohumoral system in nitrate tolerance development, assessed by modifications of catecholamines plasma levels and heart rate variability. After brief treatment with 5-ISMN, dipyridamole-stress echocardiography was negative in 19 of 22 patients (p < 0.001 vs. placebo). During the sustained phase, dipyridamole-stress echocardiography was positive after both placebo and active drug (p = NS vs. placebo). Heart rate variability showed significantly higher values in power of the low frequency (LF) band and low- to high-frequency ratio (L/H), as well as significantly lower values of the power of the high-frequency (HF) band (all p < 0.001) during brief but not during sustained administration of 5-ISMN. Norepinephrine plasma levels were significantly higher (p < 0.001) during short-term 5-ISMN administration but not during the sustained phase. Our results indicate that short-term administration of 5-ISMN antagonizes dipyridamole-induced myocardial ischemia and show the loss of antiischemic efficacy in 95% of patients during sustained treatment, demonstrating that dipyridamole-stress echocardiography is a useful tool to assess the presence of nitrate tolerance. Spectral analysis of heart rate variability and norepinephrine values confirm that brief nitrate administration increases sympathetic activity, a possible crucial trigger event in the development of nitrate tolerance, whereas prolonged nitrate treatment is not associated with prolonged neurohumoral activation.

Verapamil reduces dipyridamole-induced myocardial ischemia in patients with coronary artery disease

The aim of this study was to evaluate the effects of verapamil administration on dipyridamole-induced transient wall-motion abnormalities as detected by two-dimensional echocardiographic monitoring in patients with coronary artery disease. Twenty-eight patients (16 men and 12 women; mean age, 60+/-7 years) with angiographic evidence of significant coronary artery disease, positive dipyridamole echocardiography test results at basal condition on two consecutive days, were prospectively studied. Patients were randomized to verapamil (360 mg/day) or placebo treatments, given in three divided doses daily for 7 days; at the end of this time, each patient crossed over to the alternate regimen. Dipyridamole echocardiographic testing was repeated at the end of each treatment period. Our data demonstrate that verapamil significantly reduces the dipyridamole-induced wall-motion score index, a quantitative marker of acute myocardial ischemia (1.7+/-0.4 vs. 1.3+/-0.2; p<0.001). Hemodynamic data show that the drug reduces heart rate and rate-pressure product at basal condition (heart rate from 75+/-8 to 67+/-9 beats/min; p<0.001; rate-pressure product from 99+/-13 to 86+/-13 U x 10(-2); p<0.001) and at peak dipyridamole infusion (heart rate from 96+/-8 to 89+/-6 beats/min; p<0.001; rate pressure product from 127+/-21 to 118+/-13 U x 10(-2); p<0.05) with respect to placebo treatment. We conclude that verapamil is able to reduce dipyridamole-induced ischemia, as detected by two-dimensional echocardiographic monitoring, in patients with coronary artery disease by reducing, at least partially, myocardial oxygen consumption. Moreover, its beneficial action could be related to the effects of the drug on coronary collateral circulation and on sympathetic modulation.

Protective effect of captopril on ischemic myocardium

The protective effect and mechanism of action of the angiotensin-converting enzyme inhibitor (ACE-I) captopril was investigated in organelles from ischemic myocardial cells in a canine coronary ligation model. Sarcoplasmic reticulum (SR) and mitochondrial fractions were extracted from ischemic and nonischemic myocardial cells from captopril- and saline-treated (control) hearts. Heart rate, cardiac output, and right ventricular systolic blood pressure were similar in the captopril-treated and control groups. Left ventricular systolic blood pressure (LVPs) decreased gradually to 89% of the baseline value after captopril administration, and to 78% of the baseline value after ligation. Ca-ATPase activity in the SR, the respiratory control ratio (RCR) in the mitochondria, and dinitrophenol (DNP)-stimulated ATPase activity were significantly higher in ischemic myocardium from the captopril-treated group than from the saline-treated (control) group. The SH group content of both organelles was higher in the captopril-treated group. Our results suggest that, in addition to their hemodynamic effects, ACE-I agents containing SH groups protect the myocardium from ischemic damage by preventing enzyme oxidation.