[The heart in systolic hypertension].
Among the various forms of systolic hypertension, the primary hyperkinetic heart syndrome (overactivity of the cardiac beta-receptors) and the systolic hypertension in the elderly are the more interesting ones. The former, although involving subjects in the second or third decade of life, is a separate entity from the hyperdynamic phase of primary hypertension. Beta-adrenergic blockade, even at very long-term, is able to normalize all the major features of the syndrome (systolic hypertension, high cardiac output and systolic ejection rate, and variability of the repolarization phase of the electrocardiogram related to changes in the cardiac adrenergic tone). Beta-blockade is not curative and the syndrome reappears as soon as treatment is interrupted. It is a sort of clinical experimental model allowing the following deductions: high cardiac output is able to cause systolic hypertension; its persistence does not promote the development of an elevated systemic vascular resistance; although exposed to some of the stimuli that promote cardiac hypertrophy, such as increased stress of the ventricular wall, very prolonged adrenergic stimulation, activation of the renin system, the syndrome does not evolve towards ventricular hypertrophy. Regarding isolated systolic hypertension in the elderly, the so called de novo and "burned out" hypertension, are currently indicated as the two forms that characterize patients in the seventh and eighth decades of life. Both are interpreted as due to a loss of capacitance of the arterial system. It follows that the great vessels do not propel blood during diastole, thus increasing the hemodynamic burden on the left ventricle, prolonging diastole and delaying relaxation.(ABSTRACT TRUNCATED AT 250 WORDS)