[Cardiovascular risk stratification. Systolic, diastolic or pulse pressure?].
It is well known that hypertension is a highly prevalent condition in the population, carries a significant risk of adverse cardiovascular events and is therapeutically difficult to control. These factors render it "a major unsolved - but soluble - mass public health problem". One of the present-day aspects of the complexity of managing patients with high blood pressure (BP) derives from clinical and epidemiological data that have emerged over the past 10 years: the growing importance of the clinical significance of systolic and pulse BP. The pathophysiological basis of these data is based, on the one hand, on a better articulated definition of the components of BP, and on the other, on precise information concerning age-related modifications. The common definition of BP does not take into account pressure fluctuations occurring during the cardiac cycle; in fact, systolic and diastolic BP denote the extreme values of continuous variations in differential pressure. Diastolic BP reflects, to a greater extent, the trend of arterial resistances and mean BP (usually calculated as diastolic BP plus one third of the differential BP, and considered the "stable component" of the arterial sphygmogram) and has long been used as a diagnostic and therapeutic target. Systolic BP is more closely linked to variations in pulse BP (given from the difference between systolic and diastolic BP and considered the "dynamic component" of the arterial sphygmogram) and is produced by a group of factors including left ventricular ejection and the reflection of the sphygmic wave. As age increases, the walls of the aorta and the large elastic arteries progressively harden due to senile degenerative phenomena and the loss of elasticity as well as the progressive diffusion of atherosdclerotic lesions. This leads to the reduced capacity of the arterial wall to distend during the systole with a consequent increase in both systolic and pulse BP. These pathophysiological data have important clinical and prognostic implications and account for the possible diversity of significance to attribute to systolic, diastolic, mean and pulse BP, factors which, in their entirety, can represent an element, albeit partial, of resolvability of problems in managing hypertension. In fact, possibilities of diversification in the stratification of risk of the hypertensive patients may be considered on a pathophysiological basis, with the prospect of better aimed therapeutic interventions. On the whole, it appears that the clinical significance to attribute to pulse BP should be considered not as an alternative to that of systolic and diastolic BP, but rather in complementary terms, with age kept in careful consideration. In practice, by simplifying to a maximum the state of present knowledge, the values of systolic, diastolic, mean and pulse BP are all important in subjects under 60 years old. This indicates that the clinical significance to attribute to diastolic hypertension in young or middle-aged patients, which have been so accurately described by well-known meta-analyses, is not presently under discussion. What seems to change, with respect to the past, is the importance that should be attributed to the systolic and pulse BP in subjects of all ages and in particular to pulse BP in subjects over 60 years old: in these persons, the increase in pulse BP summarizes and integrates the adverse prognostic value of an elevated systolic BP and a low diastolic BP. It should be clearly understood that, in subjects over 60 years old, a high systolic BP and a low diastolic BP mean rigidity of the wall of the aorta and of the main elastic arteries; in these subjects, the isolated increase in diastolic BP, usually easily controllable by antihypertensive treatment, should not cause excessive clinical concern; instead, an increase in systolic BP - even if isolated - and, above all, an increase in pulse BP, should cause greater preoccupation, inasmuch as they are signs of consistent serious structural lesions. In other words, a 60-year-old subject with 150/90 mmHg would have a lesser risk of cardiovascular events, particularly cardiological events, than a contemporary with equal risk factors who has 150/50 mmHg. A large number of clinical studies suggest that an increase in pulse BP seems to predict cardiac ischemic events to a greater extent than the cerebrovascular events, which seem to be predicted to a greater extent by the mean BP. On the therapeutic level, the reference datum is represented by the unequivocal demonstration, furnished by wide scale interventional studies, that in hypertensive patients adequate pharmacological control of both the diastolic and systolic BP, particularly in the elderly, significantly reduces adverse consequences linked to the progression of atherosclerotic disease in the heart, brain and kidney. A degree of complexity is represented by the modest percent of patients in treatment who have BP values < 140/90 mmHg. Only a series of ad hoc studies will enable us to know when and if this negative situation can be resolved, even partially, by the clinical application of new knowledge in the pathophysiological field. From this point of view, it should be kept in mind that ACE-inhibitors, diuretics, dihydropyridinic calcium antagonists and vasopeptidase inhibitors seem to be more effective than beta-blockers in terms of preferential reduction of pulse BP. The contents of the reports that make up the Symposium constitute a valid base of knowledge and represent a concrete stimulus for research initiatives, which in the spirit of "operativeness" of the Area Prevenzione of the Italian Association of Hospital Cardiologists, follow the objective of bringing together scientific and managerial needs.
Pede
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S
Unità Operativa di Cardiologia, Ospedale N. Melli, S. Pietro Vernotico (BR), AUSL BR/1, Brindisi. spede@mail.clio.it
Lombardo
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M
D001794:Blood Pressure; D002318:Cardiovascular Diseases / Q000175:diagnosis* / Q000503:physiopathology*; D006801:Humans; D018570:Risk Assessment