Hypertensive cardiovascular disease. A pathophysiological assessment

Current challenges and unresolved problems in hypertensive disease

Over the past four or five decades, hypertension and cardiovascular medicine has experienced dramatic and innovative changes that have significantly reduced morbidity and mortality. A vast array of new antihypertensive compounds have been developed, which are able to inhibit many pathophysiologic mechanisms of the disease and prevent many of the outcomes in patients with hypertension. Much of this series of therapeutic breakthroughs have been the result of active participation of clinical scientists with tremendous and remarkable knowledge of and experience with the fundamental mechanisms of disease. In more recent years, much new information has appeared concerning the basis genetic and biologic mechanisms involved in cardiovascular and renal diseases. What remains of utmost importance is for members of the academic community with a wide spectrum of experience and points of view to continue to work with the fundamental problems and mechanisms of the diseases.

Left ventricular hypertrophy: dissociation of structural and functional effects by therapy

The heart is one of the major target organs that becomes secondarily involved with the unrelenting and progressive vascular disease of essential hypertension. As a result of this increasing afterload that is imposed upon the left ventricle, the ventricular chamber adapts structurally and functionally. Structural changes involve an increase in muscle mass that is achieved through left ventricular hypertrophy (in a manner similar to the arteriolar changes demonstrated by increased thickening). Unless antihypertensive therapy is interdicted in this disease process, left ventricular failure will ensue as the major cardiac hemodynamic consequence. Left ventricular hypertrophy is also associated with a risk that is independent of the pressure overload and hemodynamic risk. Although antihypertensive therapy will reduce from the hemodynamic alterations, only recently have epidemiological findings suggested that the independent risk of LVH may be reduced with pharmacological therapy. There are no data available to indicate just which agents may reduce the risk from LVH; but relatively recent studies seem to indicate that while all agents may reduce LVH with prolonged therapy only certain classes of agents will do so independent of their hemodynamic factors. Some of these agents, however, may impair cardiac function if arterial pressure is increased abruptly following therapeutic reduction of cardiac mass. Other agents may preserve normal function--or even may improve function. Among those classes of antihypertensive agents that reduce cardiac mass at least in part due to nonhemodynamic factors, are the angiotensin converting enzyme inhibitors, the calcium antagonists, and most adrenergic inhibitors. Evidence will be presented demonstrating the hemodynamic/structural dissociation of those pharmacological agents that reduce cardiac mass with short-term treatment in spontaneously hypertensive rats with left ventricular hypertrophy. Although centrally active adrenolytic, angiotensin converting enzyme (ACE) inhibitors, and calcium antagonists all reduce cardiac mass, their structural and cardiac functional effects differ greatly. Even within the ACE inhibitor group their effects vary--improving, impairing, or not changing the Frank-Starling relationships following reduction in left ventricular mass. We postulate great variability of cardiac intramyocytic penetrance of the pharmacological agents and their local intracellular effects on mitogenesis of the ventricular myocyte. The implications on cardiac function and therapy have vast potential. Therefore, current investigative areas involving new concepts of molecular biology of the cardiac myocyte may provide great promise to the quest of unraveling some of the newly postulated questions: What is the role of ionized intracellular calcium? Do the local renin-angiotensin systems in the cardiac and vascular myocyte participate in the development and regression of hypertrophy?(ABSTRACT TRUNCATED AT 400 WORDS)

Cardiac involvement in hypertension

Despite improved patient detection and pharmacologic therapy, the effect of treatment of hypertension on mortality from coronary artery-related events remains unresolved. Left ventricular (LV) hypertrophy, a known consequence of hypertension, is associated with an excess mortality independent of other known cardiovascular risk factors. Recently, LV hypertrophy accompanying hypertension has been associated with ominous ventricular arrhythmias. However, it does not necessarily follow that regression of LV hypertrophy will reduce this increased mortality. Diastolic dysfunction, manifested by reduced ventricular distensibility of the hypertrophying left ventricle, appears to be an early characteristic of the hypertensive heart since echocardiographic techniques have demonstrated diastolic filling abnormalities in untreated essential hypertensives even before significant LV hypertrophy appears. Not all antihypertensive agents diminish LV mass and improve diastolic dysfunction. Certain sympatholytic agents, calcium antagonists, beta-adrenergic blockers, and the angiotensin-converting enzyme inhibitors appear to diminish LV hypertrophy. However, future studies are needed to determine if these agents that appear to reverse findings of LV hypertrophy and improve diastolic dysfunction will also reduce risk of coronary artery disease and related events.

Reversal of target-organ involvement in systemic hypertension: a pharmacologic experience

Systemic hypertension is a disease manifested by a persistently elevated arterial pressure produced by an increased total peripheral resistance, which is more or less uniformly distributed throughout the component circulations. Unless pressure is reduced and maintained at controlled levels, it will be associated with impaired function of the primary target organs of the disease: brain, heart, kidneys and blood vessels. The effects of an elevated arterial pressure on heart and kidneys and the effects of antihypertensive therapy on target-organ involvement will be discussed. Cardiac involvement primarily relates to left ventricular hypertrophy and its regression with treatment, and in the kidney to altered intrarenal hemodynamics and effects of treatment. The role of calcium antagonists, primarily diltiazem, is discussed with reference to its hemodynamic effects on reducing total peripheral resistance and arterial pressure associated with regression of ventricular hypertrophy and maintenance of renal blood flow without inordinately increasing glomerular hydrostatic pressure. Studies suggest a beneficial role of diltiazem in the treatment of essential hypertension.

Potential mechanisms explaining the risk of left ventricular hypertrophy

Major risk factors have been identified that enhance the chances of cardiovascular morbidity and mortality. These include such modifiable factors as hypertension, hyperlipidemia, obesity, diabetes mellitus, smoking and hyperuricemia. Other factors that also increase risk are not modifiable and include advancing age, male gender and black race. The development of left ventricular (LV) hypertrophy imposes another significant risk for increased morbidity and mortality. Development of LV hypertrophy may be produced by hemodynamic as well as nonhemodynamic mechanisms. Included in the latter group are some of the same factors that in and of themselves participate in the production of increased LV mass (i.e., aging, gender and race, obesity, coronary disease, diabetes and the underlying mechanisms that subserve the hypertensive disease). This article discusses the concept, drawn from clinical and experimental studies, that demonstrate that the additional increased risk of LV hypertrophy may be ascribed to loss of reserve cardiac function, accelerated atherosclerosis, development of abnormal cardiac rhythm secondary to ischemia, fibrosis or drug-induced hypokalemia, inherent predisposition to ventricular dysrhythmias and sudden death, risks directly or coincidentally related to associated diseases or perhaps even the paradoxical risk of beneficial antihypertensive therapy.