Losartan for cardiovascular disease in patient's with and without diabetes in the LIFE study

Review: Implications from hypertension outcome trials for the management of patients with hypertension and diabetes

The UKPDS highlighted the importance of blood pressure control in patients with type 2 diabetes. In this review I draw on data from the INSIGHT and other recent outcome trials in hypertension which provide clear evidence that it is the achievement of good control of blood pressure, irrespective of the initial choice of drug, that is the major determinant of outcome. The INSIGHT trial provides hard evidence of how resistant to treatment patients with diabetes really are. In this review I offer a theoretical and practical solution in the form of a stepwise algorithm using multiple therapies.

Does it matter where we measure blood pressure?

Although blood pressure measured at the brachial artery plays a central role in our understanding and management of cardiovascular risk, in recent years great emphasis has been placed on the importance of central blood pressure. It seems straightforward that knowledge of the blood pressure directly affecting the major organs is important for understanding the pathophysiology and treatment of cardiovascular risk. However, the field has been troubled by controversies over measurement techniques and difficulty in designing therapies to modify central but not peripheral blood pressure. In this review, we consider the physiology underlying the change in blood pressure through the arterial tree and how central blood pressure can be measured. In addition, we review the evidence regarding the relationship of central BP to cardiovascular disease and the effects of treatment. New measurement techniques and evidence regarding the specific benefits of therapies in modulating central haemodynamics mean that this is a rapidly developing area, and understanding the concept of central blood pressure will be vital in the future.

Current role of beta-blockers in the treatment of hypertension

IMPORTANCE OF THE FIELD

It is important to know which patients with hypertension will benefit from beta-blocker therapy and which beta-blockers should be used in the treatment of hypertension to reduce cardiovascular events and mortality.

AREAS COVERED IN THIS REVIEW

Studies between 1981 and 2009 using a Medline search are reported. Beta-blockers should be used to treat hypertension in patients with previous myocardial infarction, acute coronary syndromes, angina pectoris, congestive heart failure, ventricular arrhythmias, supraventricular tachyarrhythmias, diabetes mellitus, after coronary artery bypass graft surgery, and in patients who are pregnant, have thyrotoxicosis, glaucoma, migraine, essential tremor, perioperative hypertension, or an excessive blood pressure response after exercise.

WHAT THE READER WILL GAIN

The use of beta-blockers as first-line therapy in patients with primary hypertension has been controversial. However, the 2009 guidelines of the European Society of Hypertension state that large-scale meta-analyses of available data confirm that diuretics, beta-blockers, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers and calcium channel blockers do not significantly differ in their ability to lower blood pressure and to exert cardiovascular protection both in elderly and in younger patients.

TAKE HOME MESSAGE

The key message of this paper is that atenolol should not be used as an antihypertensive drug and that the degree of reduction of mortality, myocardial infarction, stroke and congestive heart failure by antihypertensive therapy is dependent on the degree of lowering of aortic blood pressure. Newer vasodilator beta-blockers such as carvedilol and nebivolol may be more effective in reducing cardiovascular events than traditional beta-blockers, but this needs to be investigated by controlled clinical trials.

Aliskiren

Aliskiren is the first orally active inhibitor of renin to be approved for clinical use as an antihypertensive agent. The development program has established that at the licensed doses of 150 mg and 300 mg, there are dose-related falls in blood pressure comparable to those seen with other major classes of antihypertensive drugs and that these falls are associated with a placebo level of side effects. Aliskiren was found to be effective either as monotherapy or in combination with drugs from the other major classes. As expected, there was a greater benefit from adding aliskiren to natriuretic drugs than to other blockers of the renin system. However, there was also some consistent benefit from dual renin blockade. Aliskiren is likely to be of most value in patients uncontrolled by, or intolerant of, other classes. Rational understanding of the renin system will maximize its value, for instance, by encouraging greater use of natriuretic agents in patients with resistant hypertension to render their hypertension renin dependent. Whether there are cardiovascular benefits other than blood pressure control in blocking the renin system remains to be demonstrated. It is hoped that long-term outcome studies with aliskiren will finally allow this question to be answered.

Renin: friend or foe?

Renin maintains blood pressure through vasoconstriction when there is inadequate salt to maintain volume. In populations where blood pressure is more often high than low, and vascular death more common than haemorrhage or dehydration, therapeutic reductions in renin secretion or response are valuable. Whether long-term benefits are due entirely to blood pressure reduction remains unproved. The pathway can be blocked at its rate-limiting step (beta blockade or direct renin inhibition), the synthesis of the active product, angiotensin II, or at the receptor for angiotensin. Because renin and sodium are the two main factors in blood pressure control, and renin levels vary inversely with sodium load, blood pressure control requires a combination of natriuresis and blocking the consequential increase in renin activity. Being a large and stable molecule, renin is among the easiest and cheapest of hormone measurements. Understanding the simple biochemistry and physiology of renin permits optimal use of the drugs acting to raise or suppress this hormone.

The latest generation of beta-blockers: New pharmacologic properties

beta-Blockers have generally demonstrated smaller reductions in cardiovascular events, compared with other antihypertensive classes, despite similar reductions in blood pressure. This may be due to the ineffectiveness of traditional beta-blockers, such as atenolol, in reducing central aortic pressure, a strong, independent predictor of cardiovascular outcome. However, the beta-blocker class is heterogeneous, and some newer beta-blockers, which exhibit vasodilatory effects independent of beta-blockade, provide beneficial effects on arterial stiffness and endothelial dysfunction, which may lead to reductions in central aortic pressure and improvements in clinical outcomes. For example, the vasodilating beta-blocker nebivolol was shown to improve forearm blood flow and arterial stiffness and, in a large clinical study, to significantly reduce morbidity and mortality, independent of left ventricular ejection fraction, among patients with chronic heart failure. Further research is warranted to investigate any potential differences between traditional and newer vasodilating beta-blockers on cardiovascular outcomes.

Angiotensin receptor blockade in the challenging era of systolic hypertension

Systolic blood pressure is a major cardiovascular risk factor which is often associated with arterial stiffness. Markers of arterial stiffness, such as pulse pressure and carotid-femoral pulse wave velocity, have been proved independent predictors of cardiovascular risk. Recent evidence suggests that the renin-angiotensin system is involved in the pathogenesis of systolic hypertension and arterial stiffness. Outcome trials have shown impressive cardiovascular protection by reducing systolic blood pressure (BP) with drug treatment. However, in clinical practice systolic hypertension remains largely uncontrolled, first, because systolic BP goal is more difficult to be reached than diastolic and, second, because physicians are often reluctant to intensify treatment in patients with systolic BP close to 150 mmHg. Recent trials have focused on the effects of antihypertensive drugs not only on blood pressure, but also on pulse pressure and pulse-wave velocity. Blockade of the renin-angiotensin-aldosterone system, using angiotensin-converting enzyme inhibitors and more recently angiotensin receptor blockers, has been shown to provide beneficial effects on arterial stiffness that appear to be independent of their antihypertensive effects. Recent outcome trials have shown significant cardiovascular protection with angiotensin receptor blockers. These drugs have an excellent placebolike profile of adverse effects which is maintained when these drugs are combined with low-dose diuretics. Therefore, an angiotensin receptor blocker-based treatment strategy appears to be an attractive and evidence-based approach for the management of systolic hypertension, the reduction of arterial stiffness and the prevention of cardiovascular disease.