Fibrosis and ischemia: the real risks in hypertensive heart disease

The increased cardiovascular morbidity and mortality in hypertension are related to the target organs (ie, heart, brain, kidneys) involvement from vascular disease. Left ventricular hypertrophy (LVH), the major expression of cardiac involvement, is both a structural and functional adaptation to the afterload imposed by the vascular disease. Without this adaptation, cardiac failure would result much earlier in the natural history of hypertensive heart disease (HHD). However, LVH imposes an independent risk that is even greater than the risk associated with the height of systolic or diastolic pressure. The mechanisms that explain this risk have not been defined precisely; several have been postulated. Among these are the following: 1) coronary hemodynamic alterations associated with HHD (ie, increased coronary vascular and minimal vascular resistance, reduced coronary blood flow and flow reserve, and increased blood viscosity); 2) enhanced predisposition for lethal cardiac arrhythmias, cardiac failure, and accelerated atherosclerosis of the coronary arteries (with exacerbation of the ischemia); and 3) collagen deposition and ventricular fibrosis. From the earliest controlled therapeutic trials, deaths from stroke and coronary heart disease were significantly reduced. However, more recent data have indicated that the prevalence of cardiac failure (CHF) continues to rise progressively. The nature of the CHF is no longer primarily from systolic dysfunction, but is now chiefly from diastolic dysfunction. Diastolic dysfunction occurs primarily in the elderly hypertensive patient or in the patient with ischemic heart disease, both of which are associated with increased collagen deposition. Indeed, these effects continue to be suggested by the data from the Framingham Heart Study as well as NHANES-III that indicate CHF is the most common diagnosis occurring in hospitalized patients over 65 years of age. In this report, both experimental and clinical evidence demonstrating that increased ventricular fibrosis occurs in the spontaneously hypertensive rats and in hypertensive patients are provided, and that treatment with the newer antihypertensive agents reduce ventricular hydroxyproline (ie, collagen) content while, at the same time, improve coronary hemodynamics.