The evolution of systolic blood pressure as a strong predictor of cardiovascular risk and the effectiveness of fixed-dose ARB/CCB combinations in lowering levels of this preferential target

Elevated blood pressure is an important cardiovascular risk factor. Although targets for both diastolic blood pressure (DBP) and systolic blood pressure (SBP) are defined by current guidelines, DBP has historically taken precedence in hypertension management. However, there is strong evidence that SBP is superior to DBP as a predictor of cardiovascular events. Moreover, achieving control of SBP is assuming greater importance amongst an aging population. In spite of the growing recognition of the importance of SBP in reducing cardiovascular risk and the emphasis by current guidelines on SBP control, a substantial proportion of patients still fail to achieve SBP targets, and SBP control is achieved much less frequently than DBP control. Thus, new approaches to the management of hypertension are required in order to control SBP and minimize cardiovascular risk. Fixed-dose combination (FDC) therapy is an approach that offers the advantages of multiple drug administration and a reduction in regimen complexity that favors compliance. We have reviewed the latest evidence demonstrating the efficacy in targeting SBP of the most recent FDC products; combinations of the calcium channel blocker (CCB), amlodipine, with angiotensin receptor blockers (ARBs), valsartan or olmesartan. In addition, results from studies with new classes of agent are outlined.

Results of the ONTARGET and TRANSCEND studies: an update and discussion

The renin angiotensin aldosterone system (RAAS) plays an important role in the pathophysiology of cardiovascular disease. Angiotensin converting enzyme inhibitors (ACEi) have proven benefit in reducing cardiovascular events in patients at high risk. Angiotensin receptor blockers (ARB) have been demonstrated to have benefit in the management of heart failure and to be non-inferior to ACEi in patients with left ventricular dysfunction after a myocardial infarction (MI). Yet until now, there has been no trial to support the use of the ARB for vascular protection. The ONTARGET study showed that the ARB telmisartan conserved 95% of the vascular protective properties of the ACEi ramipril, given at similar doses to a similar patient group as had been previously shownin the HOPE study to benefit from ACE inhibition with ramipril. The TRANSCEND study in a similar population of patients who were intolerant of ACEi despite the primary endpoint being neutral, showed a trend to a benefit for the combined secondary endpoint of cardiovascular death, MI and stroke, with excellent tolerance of the ARB. The reasons for neutral result of the TRANSCEND study result include an underpowered study, and pre-treatment with a RAAS inhibitor in a high proportion of patients. These studies indicate that an ARB can be used for vascular protection in high risk individuals in the place of an ACEi. However ACEi will probably remain the first choice due to the greater body of supportive evidence.

Effect of angiotensin receptor blockade on endothelial function: focus on olmesartan medoxomil

Endothelial dysfunction is the common link between cardiovascular disease risk factors and the earliest event in the cascade of incidents that results in target organ damage. Angiotensin II, the terminal pressor effector arm of the renin-angiotensin-aldosterone system, increases blood pressure (BP) by vasoconstriction and sodium and fluid retention, and has a pro-oxidative action that induces endothelial dysfunction and contributes to vascular remodeling. Angiotensin receptor blockers (ARBs) reduce BP and morbidity and mortality in patients with hypertension, ventricular hypertrophy, diabetes mellitus, and renal disease. Olmesartan medoxomil is a long-acting, well-tolerated, effective ARB that prevents or reverses endothelial dysfunction in animal models of atherosclerosis, hypertension, diabetes, nephropathy, and retinopathy. Olmesartan medoxomil, a prodrug of olmesartan approved for the treatment of hypertension, has been shown to ameliorate endothelial dysfunction in patients with hypertension or diabetes. In randomized studies, the drug reduces vascular inflammation and the volume of large atherosclerotic plaques, increases the number of regenerative endothelial progenitor cells in the peripheral circulation, improves endothelium-dependent relaxation, and restores the normal resistance vessel morphology. Importantly, the impact of olmesartan medoxomil on endothelial dysfunction is thought to be independent of BP lowering.

Fixed combination of losartan and hydrochlorothiazide and reduction of risk of stroke

A fixed-dose combination of losartan/hydrochlorothiazide (HCTZ) therapy may be a logical choice for antihypertensive treatment, including for initial therapy in patients with blood pressure elevation >20/10 mmHg above treatment target. The renin-angiotensin-aldosterone-system-activating effect of hydrochlorothiazide augments the efficacy of blocking the angiotensin II type 1 (AT1) receptor with losartan. Some adverse effects associated with hydrochlorothiazide, including increased risk for new-onset diabetes mellitus, may be offset by losartan. Losartan was frequently administered with hydrochlorothiazide in the Losartan Intervention For Endpoint reduction in hypertension (LIFE) study, in which there was a 25% risk reduction for stroke in the losartan-based compared with the atenolol-based treatment group. The efficacy, tolerability, and convenience of losartan/HCTZ combination therapy may increase patient compliance and lower risk for stroke, a devastating outcome in patients with hypertension.

Cardiovascular risk reduction by reversing endothelial dysfunction: ARBs, ACE inhibitors, or both? Expectations from the ONTARGET Trial Programme

Endothelial dysfunction is the initial pathophysiological step in a progression of vascular damage that leads to overt cardiovascular and chronic kidney disease. Angiotensin II, the primary agent of the renin-angiotensin system (RAS), has a central role in endothelial dysfunction. Therefore, RAS blockade with an angiotensin receptor blocker (ARB) and/or angiotensin-converting enzyme (ACE) inhibitor provides a rational approach to reverse endothelial dysfunction, reduce microalbuminuria, and, thus, improves cardiovascular and renal prognosis. ARBs and ACE inhibitors act at different points in the RAS pathway and recent evidence suggests that there are differences regarding their effects on endothelial dysfunction. In addition to blood pressure lowering, studies have shown that ARBs reduce target-organ damage, including improvements in endothelial dysfunction, arterial stiffness, the progression of renal dysfunction in patients with type 2 diabetes, proteinuria, and left ventricular hypertrophy. The ONgoing Telmisartan Alone in combination with Ramipril Global Endpoint Trial (ONTARGET) Programme is expected to provide the ultimate evidence of whether improved endothelial function translates into reduced cardiovascular and renal events in high-risk patients, and to assess possible differential outcomes with telmisartan, the ACE inhibitor ramipril, or a combination of both (dual RAS blockade). Completion of ONTARGET is expected in 2008.

Candesartan in heart failure

Candesartan cilexetil is a nonpeptide selective blocker of the angiotensin II receptor sub-type 1. It is a prodrug that is converted to its active metabolite during its variable absorption. It is highly protein bound with a small volume of distribution and a nine-hour half-life. Candesartan is one of two angiotensin receptor blockers approved for use in heart failure. MEDLINE was searched using OVID and PubMed to evaluate the evidence for using candesartan in patients with heart failure. Pharmacologic and pharmacokinetic evaluations, as well as clinical trials, were selected and are presented in this review. Clinical evidence supports the indication for use in systolic heart failure. Results for use in patients with diastolic heart failure were non-significant. Candesartan was well tolerated in the trials, with hyperkalemia, renal dysfunction, and hypotension being the most common adverse events. Use of angiotensin receptor blockers with angiotensin-converting enzyme inhibitors needs further study; however, candesartan appears to provide added benefit in this setting. Candesartan is a safe and effective option for patients with systolic heart failure. Data regarding other angiotensin receptor blockers is underway.

Reducing the risks of sudden death and heart failure post myocardial infarction: utility of optimized pharmacotherapy

Current guidelines define the standard of care for patients after myocardial infarction (MI), with particular focus on patients with significant ventricular dysfunction. Inherent in these recommendations are assumptions about the relative risks and benefits, as well as the costs, of the available options. This review will consider strategies to prevent sudden death and heart failure post-MI by utilization of pharmacologic therapies--angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARB), aldosterone antagonists, statins, and beta-blockers--in parallel with the approaches reviewed elsewhere in this supplement. A patient-centric approach necessitates that drugs in each class be compared for efficacy within this patient population. Clinical trials have demonstrated the efficacy of several drugs, such as ACE inhibitors, beta-blockers, and aldosterone antagonists, in patients post-MI, yet these benefits do not seem to be reflected in the epidemiologic data. This may reflect underutilization of these therapies or, alternatively, support the notion that efficacy in clinical trials does not assure effectiveness in clinical practice. The latter point is a subject of ongoing investigation, while the former is being addressed through quality-of-care initiatives. In clinical practice, aggressiveness is key, starting with patient education. If patients understand their risks better, compliance and adoption of a more ideal lifestyle seem more likely. However, even with educational programs, human nature teaches us that marked change in behavior is difficult and therefore, to minimize risks, particularly of sudden death and heart failure post infarction, an optimized pharmacologic regimen serves as a powerful tool.

Use of angiotensin II receptor blockers alone and in combination with other drugs: a large clinical experience trial

Angiotensin II (Ang II) receptor blockers are the newest class of antihypertensive drugs to be developed. No large-scale clinical trials have been performed to evaluate their efficacy alone, or in combination with other drugs. A large-scale, eight week, open-label, non-placebo-controlled, single-arm trial evaluated the efficacy, tolerability and dose-response of candesartan cilexetil, 16-32 mg once-daily, either as monotherapy or as part of combination therapy, in a diverse hypertensive population in actual practice settings. 6465 patients with high blood pressure, of whom 52% were female and 16% African American, with a mean age of 58 years, were included. 5446 patients had essential hypertension and 1014 patients had isolated systolic hypertension. In order to be included in this study, patients had either untreated or uncontrolled hypertension (systolic blood pressure (SBP) 140-179 mmHg and/or diastolic blood pressure (DBP) 90-109 mmHg inclusive at baseline), despite a variety of other antihypertensive drugs. Of the 5156 patients with essential hypertension and at least one post baseline efficacy measurement, the mean pretreatment blood pressure (BP) was 156/97 mmHg. Candesartan cilexetil monotherapy reduced mean SBP/DBP by 18.0/12.2 mmHg. Similarly, in the 964 patients with isolated systolic hypertension and at least one post baseline efficacy measurement, candesartan cilexetil monotherapy reduced SBP/DBP from 158/81 by 16.5/4.5 mmHg. Candesartan cilexetil was similarly effective when employed as add-on therapy. When added to baseline antihypertensive medication in 51% of the patients with essential hypertension not achieving BP control, additional reduction in BP was achieved regardless of the background therapy, including diuretics (17.8/11.7 mmHg) calcium antagonists (16.6/11.2 mmHg), beta-blockers (16.5/10.4 mmHg), angiotensin-converting enzyme inhibitors (ACE-I) (15.3/10.0 mmHg), and alpha blockers (16.4/10.4 mmHg). Likewise, when candesartan cilexetil was used as add-on therapy in patients with isolated systolic hypertension, there was a consistent further reduction of mean SBP/DBP, regardless of the background therapy. Moreover, these monotherapeutic or add-on efficacy benefits were seen regardless of age (<65 or >65 years), gender, or race. Despite the open-label design of the study which enhances efficacy owing to the placebo effect, the Ang II receptor blocker, candesartan cilexetil either alone, or as an add-on therapy, is highly effective for assisting in the control of systolic and diastolic hypertension.

Angiotensin receptor blockers in heart failure after the ELITE II trial

Specific blockers of the angiotensin type1 receptor, angiotensin receptor blockers (ARBs), have been introduced as an alternative to angiotensin-converting enzyme inhibitors (ACEi) for the treatment of heart failure. In comparison with ACEi, ARBs are better tolerated and have similar effects on haemodynamics, neurohormones and exercise capacity. Early studies have suggested that ARBs might have a superior effect on mortality. However, the first outcome trial, ELITE II (Losartan Heart Failure Survival Study), did not show any significant difference between losartan and captopril in terms of mortality or morbidity. This commentary outlines the role of ARBs in the treatment of heart failure.