Neuroadrenergic effects of calcium channel blockers: a developing concept

Sympathetic mechanisms, organ damage, and antihypertensive treatment

Sympathetic activation characterizes essential hypertension, contributing to the development and progression of the high blood pressure state. Throughout the years, evidence has been accumulated to show that adrenergic overdrive also participates in the pathogenesis of the end-organ damage associated with hypertension, including cardiac hypertrophy, left ventricular diastolic dysfunction, and heart failure, as well as the vascular structural and functional alterations that frequently can be detected in large, medium-size, and small arteries. Adrenergic overdrive also participates in the renal insufficiency and failure that may accompany the clinical course of the hypertensive state. This paper reviews evidence collected over the past few years documenting the importance of neurogenic factors in the development and progression of end-organ damage. The therapeutic implications of this evidence are also highlighted.

Sympathetic overdrive and cardiovascular risk in the metabolic syndrome

Sympathetic neural factors are involved in energy balance as well as in blood pressure control. This represents the background for the hypothesis that an adrenergic overdrive may be implicated in the development and/or progression of the metabolic syndrome. Indirect and direct markers of sympathetic drive have confirmed this hypothesis, by showing the occurrence of an adrenergic activation both at the cardiac and peripheral vascular level. It is likely that this sympathetic dysfunction is triggered by reflex mechanisms (arterial baroreceptor impairment), metabolic factors (insulin resistance), and humoral agents (angiotensin II, leptin). The adrenergic overdrive exerts a number of adverse effects on the cardiovascular system, by favoring the genesis of cardiac hypertrophy, vascular hypertrophy, arterial remodeling and endothelial dysfunction and thereby aggravating the already elevated cardiovascular risk profile of the patient. This carries obvious clinical and therapeutic implications, including the suggestion that sympathetic inhibition should be included among the goals of both pharmacological and non-pharmacological interventions employed in the treatment of the metabolic syndrome.

Counteracting the sympathetic nervous system in essential hypertension

PURPOSE OF REVIEW

This paper will provide an up-to-date overview of the adrenergic effects of the different classes of antihypertensive drugs in uncomplicated hypertension, as well as in hypertension associated with obesity, renal failure, diabetes or congestive heart failure.

RECENT FINDINGS

Animal and human studies unequivocally show that sympathetic activation characterizes the hypertensive state and participates in the development, maintenance and progression of elevated blood pressure values. Evidence has also been provided that elevated sympathetic cardiovascular influences are involved in the pathogenesis of left ventricular hypertrophy, vascular hypertrophy and atherogenesis, as well as in the occurrence of metabolic disarray (i.e. metabolic syndrome, hypercholesterolemia, hyperinsulinemia and insulin resistance), which frequently accompany the hypertensive state. Antihypertensive drugs with confirmed sympathoinhibitor effects are represented by beta-blockers, angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers. In the case of the latter two classes of antihypertensive compounds the sympathoinhibitory effects have been shown to be associated with beneficial metabolic and cardiovascular effects, a finding that supports the use of these drugs in complicated hypertension.

SUMMARY

Investigation of the adrenergic effects of antihypertensive drugs has had a significant impact on cardiovascular pharmacology and hypertension treatment. Although remarkable progress has been made on this topic in recent years, future studies aimed at assessing the sympathetic effects of combination drug treatment will be helpful in improving the clinical use of the association of two or more drugs in hypertension treatment.