Effects of angiotensin-converting enzyme inhibition on transient ischemia: the Quinapril Anti-Ischemia and Symptoms of Angina Reduction (QUASAR) trial

Rationale and design of the Women's Ischemia Trial to Reduce Events in Nonobstructive CAD (WARRIOR) trial

BACKGROUND

Approximately half of all women with anginal symptoms and/or signs of ischemia and no obstructive coronary artery disease (INOCA) referred for coronary angiography have elevated risk for major adverse cardiac events (MACE), poor quality of life and resource consumption. Yet, guidelines focus on symptom management while clinical practice typically advocates only reassurance. Pilot studies of INOCA subjects suggest benefit with intensive medical therapy (IMT) that includes high-intensity statins and angiotensin converting enzyme inhibitors (ACE-I) or receptor blockers (ARB) to provide the rationale for a randomized pragmatic trial to limit MACE.

METHODS

The Women's IschemiA TRial to Reduce Events In Non-ObstRuctive CAD is a multicenter, prospective, randomized, blinded outcome evaluation (PROBE design) of a pragmatic strategy of IMT vs usual care (UC) in 4,422 symptomatic women with INOCA (NCT03417388) in approximately 70 United States sites. The hypothesis is that IMT will reduce the primary outcome of first occurrence of MACE by 20% vs. UC at ∼2.5 year followup. Secondary outcomes include quality of life, time to return to "duty"/work, healthcare utilization, angina, cardiovascular death and individual primary outcome components over 3 years follow-up. The study utilizes web-based data capture, e-consents, single IRB and centralized pharmacy distribution of strategy medications directly to patients' homes to reduce site and patient burden. A biorepository will collect blood samples to assess potential mechanisms.

CONCLUSIONS

The results of this trial will provide important data necessary to inform guidelines regarding how best to manage this growing and challenging population of women with INOCA.

The clinical significance of continuous ECG (ambulatory ECG or Holter) monitoring of the ST-segment to evaluate ischemia: a review

Silent ischemia is a common manifestation of coronary artery disease (CAD). Continuous ECG (cECG) monitoring is an effective tool for assessing the frequency and duration of silent ischemic episodes for patients with CAD and for risk stratifying asymptomatic patients or those after an acute coronary syndrome by identifying those at increased risk for future cardiovascular events or death. cECG also allows monitoring of the effectiveness of therapy in patients with CAD. Treatment strategies targeted toward the elimination of silent ischemia have shown that revascularization was better than medical therapy in eliminating silent ischemia, but large scale, prospective studies targeting silent ischemia as a treatment endpoint are still lacking. Future research is warranted to study the effects of newer medical agents or the selected use of revascularization in those patients with persistent silent ischemia despite current medical regiments.

Meta-analysis of randomized trials of angioedema as an adverse event of renin-angiotensin system inhibitors

Angioedema is a rare, potentially life-threatening adverse event of renin-angiotensin system inhibitors. The objective of the present study was to determine the risk of angioedema from randomized clinical trials. A PubMed/CENTRAL/EMBASE search was made for randomized clinical trials from 1980 to October 2011 in patients on angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), or direct renin inhibitor (DRI). Trials with a total number of patients ≥100 and a duration of ≥8 weeks were included for analysis. Incidence of angioedema was pooled by weighing the incident rate of each trial by the inverse of the variance. Twenty-six trials with 74,857 patients in the ACE inhibitor arm with 232,523 person-years of follow-up, 19 trials with 35,479 patients on ARB with 122,293 person-years of follow-up, and 2 trials with 5,141 patients on DRI with 1,735 person-years of follow-up met the inclusion criteria and were included in the analysis. In head-to-head comparison in 7 trials, risk of angioedema with ACE inhibitors was 2.2 times higher than with ARBs (95% confidence interval [CI] 1.5 to 3.3). With ACE inhibitors and ARBs, incidence of angioedema was higher in heart failure trials compared to hypertension or coronary artery disease trials without heart failure (p <0.0001). Weighted incidence of angioedema with ACE inhibitors was 0.30% (95% CI 0.28 to 0.32) compared to 0.11% (95% CI 0.09 to 0.13) with ARBs, 0.13% (95% CI 0.08 to 0.19) with DRIs, and 0.07% with placebo (95% CI 0.05 to 0.09). In conclusion, incidence of angioedema with ARBs and DRI was <1/2 than that with ACE inhibitors and not significantly different from placebo. Incidence of angioedema was higher in patients with heart failure compared to those without heart failure with ACE inhibitors and ARBs.

Effects of antihypertensive treatments on incidence of diabetes: a case-control study

AIMS

Aim of this case-control study is the assessment of the relationship between antihypertensive treatment and incidence of diabetes in an unselected cohort of subjects participating in a screening program for diabetes.

METHODS

A case-control study nested within a cohort of nondiabetic subjects with a mean follow-up of 27.7 ± 11.3 months was performed, comparing 40 cases of incident diabetes and 160 controls matched for age, sex, body mass index, fasting plasma glucose, 2-h post-load glycemia, smoking and alcohol abuse.

RESULTS

When considering antihypertensive treatment at enrolment, a lower proportion of cases was exposed to ACE-inhibitors/angiotensin receptor blockers (ACE-i/ARB) in comparison with controls. A non-significant trend toward a higher exposure to diuretics, which were mainly represented by thiazide diuretics, was observed in cases. In a multivariate analysis, including both ACE-i/ARB and diuretics, a protective effect of ACEi/ARB, and an increased risk with diuretics were observed. Similar results were obtained in alternative models, after adjusting for systolic and diastolic blood pressure at enrolment, diagnosis of hypertension, concurrent treatment with β-blockers or calcium-channel blockers, and number of antihypertensive medications.

CONCLUSIONS

Diuretics seem to be associated with a higher incidence of diabetes, whereas treatment with ACEi/ARB could have a protective effect.

Effects of angiotensin-converting enzyme inhibitors beyond lowering blood pressure--are they important for doctors?

Large clinical trials and experimental studies have indicated that not all of the beneficial properties of angiotensin-converting enzyme inhibitors (ACE-Is) can be attributed to the lowering of blood pressure. The aim of this study was to assess doctors' opinions about the importance of the cardioprotective effects of ACE-Is beyond lowering blood pressure. The study participants (685 physicians) filled in a questionnaire testing doctors' knowledge of all of the therapeutic effects of ACE-Is not directly associated with lowering blood pressure and their clinical importance. In addition, each doctor filled in 20 questionnaires for subsequent patients treated with any ACE-I. Fifty-nine percent of the investigated physicians were aware of most of the therapeutic effects of ACE-Is. The most important therapeutic effects for the respondents were the following: reduction of peripheral resistance, inhibition of left ventricle hypertrophy, inhibition of vascular remodeling and atherosclerotic plaque stabilization. The most commonly prescribed ACE-Is were perindopril, lisinopril and chinalapril for inhibition of left ventricular hypertrophy and perindopril, ramipril and chinalapril for inhibition of arterial wall remodeling. The ACE-Is that were used to reduce peripheral vessel resistance included perindopril, lisinopril and trandolapril. Drugs used to stabilize the plaque included perindopril, lisinopril and cilazapril. The therapeutic effects of ACE-Is beyond lowering blood pressure were considered to be valid and important in daily clinical practice for the prevention of cardiovascular diseases and diabetic complications. The attribution of the effects of a particular ACE-I was not always in accordance with evidence-based medicine. The obtained treatment outcomes were attributed to the entire group of ACE-Is.

Zofenopril in the treatment of patients with arterial hypertension and stable coronary heart disease: effects on oxidative stress and flowdependent vasodilatation

Aim. To compare the effects of ACE inhibitors zofenopril and perindopril on endothelial function and oxidative stress (OS) in patients with stable CHD and AH. Material and methods. In total, 40 patients with stable CHD (Functional Class II-III effort angina) and Stage 1-2 AH received zofenopril (7,5-30 mg/d; mean dose 18,6±8,8 mg/d; n=17) or perindopril (2-8 mg/d; mean dose 4,1±2,1 mg/d; n=23) for 12 weeks. At baseline and in the end of the study, all patients underwent reactive hyperemia test (RHT), to assess flow-dependent vasodilatation of brachial artery, and the measurement of OS parameters (malone dialdehyde, MDA, in low-density lipoproteins, MDALDL) and antioxidant parameters (superoxide dismutase (SOD) and glutathione peroxidase (GPO) activity in erythrocytes).

Results. In both groups, a similar reduction in systolic and diastolic blood pressure levels was observed. In the zofenopril group, a significant elevation in brachial artery diameter increase during RHT, a significant increase in GPO activity, and some reduction in MDALDL levels were observed, which points to antioxidant system (AOS) activation and OS reduction. No similar changes of these parameters were observed in the perindopril group. Conclusion. In patients with stable CHD and AH, zofenopril, but not perindopril, reduced OS severity and increased AOS system activity, which was associated with improved endothelial-dependent vasodilatation.

Quinaprilat: a review of its pharmacokinetics, pharmacodynamics, toxicological data and clinical application

BACKGROUND

Quinaprilat is an ACE inhibitor for intravenous use especially in patients with arterial hypertension or chronic heart failure. In contrast to the oral prodrug quinapril, it has not been approved for clinical application.

OBJECTIVE

In this review, the pharmacokinetic and pharmacodynamic profile of quinaprilat as well as toxicological data and results of preclinical and clinical studies are summarized.

METHODS

In a PubMed search for the terms "quinaprilat" and "quinapril", literature relevant for this review was selected.

RESULTS

Quinaprilat is a potent nonsulfhydryl selective ACE inhibitor with a short elimination half-life of 2 - 3 h, but due to slow dissociation from tissue ACE, once daily dosing is sufficient for effective ACE inhibition. Quinaprilat is excreted mainly in urine. In long-term animal studies, quinaprilat was not teratogenic, mutagenic or carcinogenic. However, due to the risk of fetal and neonatal morbidity and death, it should not be administrated in pregnancy. Quinaprilat is characterized by an excellent safety profile; adverse events occur infrequently and are rarely serious.

CONCLUSION

Quinaprilat is an attractive ACE inhibitor, which potently inhibits tissue ACE.

Divergences in antihypertensive therapy in special situations in nephrology

CONTEXT AND OBJECTIVE

The choice of an antihypertensive drug is based on several criteria and specific situations give rise to doubt and controversy. The aim here was to evaluate physicians approaches towards treatment with antihypertensive agents in specific situations.

DESIGN AND SETTING

Cross-sectional study, at Universidade Federal de São Paulo, São Paulo.

METHODS

A questionnaire was applied during a nephrology meeting to evaluate individual approaches towards each hypothetical clinical situation. The questionnaire consisted of five multiple-choice questions (clinical cases) concerning controversial aspects of antihypertensive therapy.

RESULTS

A total of 165 questionnaires were analyzed. Most participants were nephrologists (93.2%). There was a preference for angiotensin-converting enzyme (ACE) inhibitors in at least two of the cases. Only 57.2% of the physicians were correct in choosing beta-blockers as the first-line drugs for patients with ischemic coronary disease. Moreover, 66.2% chose ACE inhibitors as the first-line drugs for patients with chronic kidney disease and proteinuria. About 5% of the physicians did not follow the current recommendations for the use of ACE inhibitors in diabetic patients with microalbuminuria. The most controversial question concerned the first-line drug for advanced chronic kidney disease. Most physicians were correct in choosing calcium channel blockers and avoiding ACE inhibitors in renovascular hypertension in the case of a patient with a single functioning kidney.

CONCLUSIONS

Most physicians adopted the correct approach, but some had an alternative strategy for the same situations that was not based on evidence.

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-converting enzyme and vascular remodeling

Vascular remodeling is the result of a close interplay of changes in vascular tone and structure. In this review, the role of angiotension-converting enzyme (ACE) and the impact of ACE inhibition on vascular remodeling processes during vascular injury and restenosis, hypertension, atherosclerosis, and aneurysm formation are discussed. The role of ACE and angiotensin II (Ang II) in neointimal thickening has been firmly established by animal studies and is mediated by Ang II type 1 (AT(1)) receptor signaling events via monocyte chemoattractant protein-1 and NAD(P)H oxidase. ACE and Ang II are involved in the remodeling of large and resistance arteries during hypertension; here, cell proliferation and matrix remodeling are also regulated by signaling events downstream of the AT(1) receptor. In atherosclerosis, Ang II is involved in the inflammatory and tissue response, mediated by various signaling pathways downstream of the AT(1) receptor. Although ACE inhibition has been shown to inhibit atherosclerotic processes in experimental animal models, results of large clinical trials with ACE inhibitors were not conclusive. Remodeling of vessel dimensions and structure during aneurysm formation is counteracted by ACE inhibition. Here, a direct effect of ACE inhibitors on matrix metalloproteinase activity has to be considered as part of the working mechanism. The role of ACE2 in vascular remodeling has yet to be established; however, ACE2 has been shown to be associated with vascular changes in hypertension and atherosclerosis.

Effects of zofenopril on myocardial ischemia in post-myocardial infarction patients with preserved left ventricular function: the Survival of Myocardial Infarction Long-term Evaluation (SMILE)-ISCHEMIA study

BACKGROUND

The aim of the study was to investigate the cardioprotective effects of the angiotensin-converting enzyme inhibitor zofenopril in post-myocardial infarction (MI) patients with preserved left ventricular function (LVF).

METHODS

Three hundred forty-nine post-MI patients with preserved LVF (LV ejection fraction >40%) were treated for 6 months with zofenopril 30 to 60 mg (n = 177) or placebo (n = 172) according to a double-blind, randomized study design. The primary end point of the study was the combined occurrence of significant ST-T abnormalities on ambulatory electrocardiography (ECG), ECG abnormalities or symptoms of angina during standard exercise test, recurrence of MI, and need for revascularization procedures for angina.

RESULTS

The primary end point occurred in 20.3% of zofenopril-treated and 35.9% of placebo-treated patients (P = .001), despite no differences in blood pressure control, LVF, and concomitant therapy. ST-T depression during ambulatory ECG occurred in 22.7% of patients treated with placebo and 10.7% of those undergoing ACE-inhibition treatment (P = .027). ST-T depression in response to exercise test occurred in 14.2% and 26.7% of patients treated with zofenopril or placebo, respectively, (P = .024), with a lower proportion of zofenopril-treated patients who complained of anginal pain (4.7 vs 14.3%; P = .017), significant ST depression (14.2 vs 26.7%; P = .024), and major ventricular arrhythmias (3.8 vs 10.5%; P = .048). The rate of major cardiovascular events was reduced in patients treated with ACE inhibitor, with a lower rate of development and progression of congestive heart failure.

CONCLUSIONS

The results of the SMILE-ISCHEMIA study support the cardioprotective role of zofenopril when given to patients with normal LVF after acute MI.

Novel therapeutic approaches to treating chronic angina in the setting of chronic ischemic heart disease

Pharmacologic therapy to alleviate symptoms in chronic angina has been enhanced by the recent approval of several novel compounds that complement the traditional approach using beta-adrenergic blocking drugs, calcium antagonists, and long-acting nitrates. In the United States, ranolazine, a drug that inhibits late I(Na), was approved for patients with chronic angina that remain symptomatic on beta-blockers, calcium antagonists, or long-acting nitrates, on the basis of an acceptable safety profile and efficacy in several randomized placebo controlled studies. A slight increase in the QT interval is observed (<10 ms on average) at the maximum approved dose of 1,000 mg twice daily. Therefore, an ECG should be acquired at baseline and during follow-up, and the drug should not be used in patients with QT prolongation or those who are on QT prolonging drugs unless longer term randomized outcome data demonstrates no excess risk. The MERLIN trial of non-ST-elevation acute coronary syndrome (NSTE ACS) randomized 6,560 patients to assess the potential benefit of ranolazine in reducing the composite endpoint of cardiovascular death, myocardial infarction, and recurrent ischemia, with results expected in 2007. In Europe, ivabradine, a drug that inhibits the hyperpolarization-activated mixed sodium/potassium inward I(f) current, which slows the rest and exercise heart rate, was approved in 2005. Ivabradine at a dose of 10 mg twice daily has been shown to have similar efficacy to amlodipine 10 mg once daily or atenolol 100 mg once daily in alleviating chronic angina symptoms. In this review, several other novel investigational approaches are presented and patient selection considerations for the most recent approved drugs for chronic angina are discussed.

Current strategies for the prevention of angina in patients with stable coronary artery disease

PURPOSE OF REVIEW

Angina pectoris affects at least 6.6 million people in the US and approximately 400,000 new cases of stable angina occur each year. Angina may be one of the first signs of ischemic heart disease, although it is likely not causally related to the likelihood of plaque rupture leading to an acute coronary syndrome. Modalities for treatment of angina should be used maximally to improve quality of life and decrease cardiovascular morbidity and mortality. The current recommended pharmacologic and invasive approaches, as well as novel therapies, are reviewed.

RECENT FINDINGS

Antiischemic agents, including beta-blockers, nitrates and calcium channel blockers, remain the mainstay in the prevention of angina. Revascularization via percutaneous interventions or coronary bypass surgery are appropriate in specific cases or when medical treatment fails. Noninvasive treatment options for refractory angina, metabolic agents, and vasodilator therapies are adding to the armamentarium to prevent and treat angina.

SUMMARY

A multifaceted approach is optimal to address the prevention of angina. Once angina is recognized, there are many modalities that lessen the incidence of daily life-induced and exercise-induced angina and ischemia. Angina management is best addressed by pharmacologic and lifestyle interventions.

Ranolazine, a new antianginal drug

The increasing and unmet social and economic burden of ischemic heart disease calls for new antianginal therapies. Ranolazine, a new antianginal agent, has a different mode of action from existing therapies, which act by decreasing indices of cardiac work. Ranolazine mainly affects the late sodium current across the membrane of cardiomyocytes, inducing a cascade of electrophysiologic and metabolic effects with the potential to reduce the cardiac ischemic burden without significantly changing blood pressure and heart rate. In clinical trials, ranolazine has been demonstrated to exert antianginal and anti-ischemic effects in chronic angina. It improves exercise performance, and decreases angina frequency and nitroglycerin use. Ranolazine is well tolerated at therapeutic doses. Larger studies are needed to explore the effects on hard end-points of morbidity and mortality.

Antianginal efficacy of omapatrilat in patients with chronic angina pectoris

Angiotensin-converting enzyme inhibition is not an effective antianginal therapy. Experimental data suggest that broader vasopeptidase inhibition may decrease the magnitude of demand-induced myocardial ischemia. A randomized, double-blind, placebo controlled parallel study evaluated omapatrilat, an inhibitor of angiotensin-converting enzyme and neutral endopeptidase. The primary objective was to compare maximum duration of exercise at peak plasma concentrations. Exercise treadmill studies were performed in 348 patients who had chronic angina at baseline and after 4 weeks of therapy with 80 mg/day omapatrilat or placebo. Safety data were collected and reported for all patients. Treadmill exercise duration at peak was significantly prolonged in the omapatrilat group compared with the placebo group (76.6 +/- 84.2 vs 28.7 +/- 82.2 seconds difference from baseline, p <0.001). Similar statistically significant increases were seen in time to onset of level III/IV angina and time to onset of >/=0.1-mV ST-segment depression (p <0.001). The significant improvements in exercise duration and measurements of myocardial ischemia were not sustained 20 to 28 hours after dosing. Omapatrilat was generally well tolerated in this predominantly normotensive population. The incidence of serious adverse events was 5.2% in the 2 groups. Thus, omapatrilat, an investigational vasopeptidase inhibitor, is effective in prolonging exercise duration and parameters of demand-induced myocardial ischemia in patients who have chronic angina at peak concentrations. The data confirm the proof of principle that broader vasopeptidase inhibition beyond angiotensin-converting enzyme inhibition is required to alleviate symptoms of chronic angina.

Angiotensin Antagonism in Coronary Artery Disease

The renin-angiotensin system (RAS) is an ancient and complex cascade of homeostatic reactions aimed at regulating primordial functions that ensure organ perfusion through the control of blood pressure and the regulation of renal-cardiac activity. However, the over-expression or lack of compensatory mechanisms of any of its components may initiate detrimental effects that potentially lead to disease, a balance that makes the RAS a sequence with a labile physiological equilibrium and with a strong harm potential. These characteristics of the RAS in general, and of the angiotensin converting enzyme (ACE) in particular, make it not only an important complex for the regulation of blood pressure and neuropeptide metabolism, but also a fascinating subject of study from a biochemical, evolutionary and genetic point of view. Pharmacological interventions that influence the RAS by inhibiting the ACE or the angiotensin II type 1 receptor (AT1R) have demonstrated sustained efficacy in reducing the incidence of cardiovascular events and, consequently, vascular mortality in several clinical situations. ACE inhibitors and angiotensin II receptor antagonists (ARAs) reduce blood pressure and have cardio- and vasculoprotective effects. Anti-atherosclerotic effects have also been attributed to these drugs. For these reasons, it has been hypothesised that RAS inhibitors could also reduce the recurrence of ischaemic events after myocardial revascularisation procedures, namely coronary artery by-pass graft surgery (CABG) or percutaneous coronary interventions (PCI). Information available on the effect of ACE inhibitors and ARAs in patients with coronary artery disease (CAD) previously treated with revascularisation techniques indicates a substantial reduction of mortality and infarction in these patients. However, data regarding the progression of CAD, restenosis or reocclusion of vascular conduits of the coronary circulation after myocardial revascularisation are inconsistent. In most studies, the administration of ACE inhibitors neither improved the ischaemic threshold nor reduced the need for new revascularisation procedures. On the contrary, ACE inhibitors have been associated with higher restenosis rates after PCI in some retrospective series. Conversely, a single, exploratory randomised trial demonstrated that the selective AT1R antagonist valsartan significantly reduced stent restenosis after PCI. In patients undergoing CABG, ACE inhibitors did not reduce the risk of graft degeneration or occlusion. Studies that evaluated a possible anti-atherosclerotic effect of ACE inhibitors (including some large randomised trials) have generally been negative.

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.