A Unitary Concept of Experimental and Clinical Hypertensive Cardiovascular Disease

A UNITARY CONCEPT OF EXPERIMENTAL AND CLINICAL HYPERTENSIVE CARDIOVASCULAR DISEASE ARTHUR GROLLMAN, M.D., Ph.D., F.A.C.P.* The often used term "hypertension" and a condition ofelevated blood pressure are usually considered synonymous. Such usage is confusing because many physiologic as well as pathologic conditions are characterized by a rise in blood pressure. So fundamental a function ofthe cardiovascular system as the blood pressure must change in response to many normal, as well as abnormal, conditions; hence the failure to differentiate the various conditions characterized by a rise in blood pressure and the application ofthe term "hypertension" to as varieda group ofconditions as the systolic hypertension observed in generalized arteriosclerosis, the transient elevation in blood pressure observed at times ofstress or in connection with the chronic injection ofsuch drugs as the corticoids, as wellas the disorder designated clinically as "hypertensive cardiovascular disease" must inevitably lead to confusion. The last-named condition, the subject ofthis paper, is a common disorder affecting about 7 per cent of the population; it has been the subject ofconsiderable investigation, particularly during the last two decades. The mass ofliterature, experimental as well as clinical, on the subject of hypertension does not lend itself to obvious correlation because of the tendency to consider any elevation in blood pressure synonymous with "hypertension." The purpose ofthis paper is to try to correlate the extant data—experimental and clinical—and, without any attempt to summarize this vast literature, to present a unified theory which accounts for all the available facts, permits correlation of the clinical and experimental data, and points the way for further investigation. * Department of Experimental Medicine, University of Texas Southwestern Medical School, Dallas, Texas. 208 Arthur Grollman · Hypertensive Cardiovascular Disease Perspectives in Biology and Medicine · Winter 1939 I. is Hypertensive Cardiovascular Disease a Specific Entity? Many authorities have denied the existence ofhypertension as an entity and consider it to be comparable to "fever"—a manifestation ofvarious etiologically distinct conditions characterized by elevated blood pressure. One eminent authority (i) suggests that we consider the disorder an "artifact ," inasmuch as there is no gradation from the normal to the hypertensive blood pressure level. Others (2), without differentiating "systolic hypertension" from "hypertensive cardiovascular disease," suggest that we alter the standards to be considered normal for a given age because of the frequency with which elevations in blood pressure are observed. Such attitudes obviously demand that we define hypertensive cardiovascular disease by criteria in addition to the elevated blood pressure whichjustify its being considered a definite disease entity and demonstrate the probability ofa specific mechanism as the underlying cause ofthis disturbance. Although extremely variable in its course and duration, hypertensive cardiovascular disease has definite clinical, physiologic, and pathologic characteristics which distinguish it from other conditions manifesting an elevated blood pressure. In its most commonly occurring form, designated "essential hypertension," it is hereditary and apparently congenital. In other cases it is secondary to obvious lesions which affect the vascular or parenchymatous tissue ofthe kidney. The hemodynamic characteristic ofhypertensive cardiovascular disease is a sustained elevation in systolic and diastolic blood pressure secondary to an increased peripheral resistance with a normal cardiac output. This differentiates it from "systolic" hypertension secondary to arteriosclerosis and the elevations in blood pressure observed in such conditions as coarctation of the aorta, hyperthyroidism, arteriovenous fistulae, psychic disturbances , physical exercise, etc. The most objective findings in hypertensive disease are the cardiac hypertrophy and arteriolosclerosis which are its morphologic characteristics. The latter, demonstrable during life by ophthalmoscopic examination, aids in evaluating the severity ofthe condition. These morphologicchanges are so characteristic that the presence ofthe disease may be recognized at autopsy without knowledge of the level of the patient's blood pressure during life. Except in its earliest stages, one usually has little difficulty determining whether or not a patient has hypertension by the clinical, hemodynamic, 209 and pathologic criteria outlined above. However, the most convincing evidence for the view that this disease represents a distinct entity is the fact that it can be induced with regularity in laboratory animals. In the latter, hypertension occurs spontaneously only rarely, and only with evident disease ofthe kidney or urinary tract. The claim that spontaneous hypertension is common in the dog is a...