Sunday, December 20, 2015

Hypertension treatment. What is the target?

The recent publication(1) of the results of SPRINT (Systolic Blood Pressure Intervention Trial) was received as an important news. It showed that lowering systolic blood pressure in hypertensive patients to a target of less than 120 mm. Hg. produced better results than the generally recommended target of less than 140 mm. Hg.

(More than 9000 patients who were hypertensive and not diabetic, were randomized into 2 groups: one treated to a target systolic pressure of less than 140 mm. Hg. and the other to a target of less than 120 mm. Hg. After about 3 years, the lower target group had a 25% lower relative risk of the primary composite end point of myocardial infarction, acute coronary syndrome, stroke, acute heart failure, and cardiovascular death. In addition, the lower target group had 27% lower risk of all-cause mortality. However, this group also had higher adverse events such as hypotension, syncope, and acute kidney injury or failure. The trial was stopped by the safety monitoring board before completing its planned 5 year period when the difference between the two groups became obvious.)

Interestingly this represented a move in the opposite direction to the last hypertension guidelines of the Joint National Committee (JNC 8)(2) published early 2014, which suggested that the target systolic pressure can be relaxed in people 60 y. old and above to 150 mm. Hg.; a suggestion received with scepticism by many at the time.

Blood pressure is a continuous characteristic in the community with a unimodal distribution curve. There is no clear separation between hypertensive and normotensive people.

(This point was the subject of a well known debate in the forties and fifties of the last century between two British physicians, George W. Pickering who held the idea of a unimodal distribution and thought that primary hypertension represents the pressure of people on the high side of the distribution curve and Robert Plat who claimed that the distribution is bimodal and that primary hypertension is a separate disease entity carried by an autosomal dominant gene. Pickering idea prevailed. It conforms with the present thinking.)

The complications of high blood pressure are the results of the physical effects of blood pressure on the arterial wall and the heart and as such are proportional to the height of blood pressure (correlating more with systolic pressure). They constitute a continuum without cut off points above which complications occur and below which they do not. The lower the pressure, the less are the possible complications. On the other hand lower pressure may impair tissue perfusion and may predispose to thrombosis. The optimum level is that which produces the most benefit and least risk. If going down to 120 mm. Hg. produces a better risk benefit balance then it will be reasonable to make it the target. But one would like this to be confirmed by further studies. The other important point is that every patient is unique and advices based on studies of groups of patients do not necessarily apply to every individual patient. You will have to decide in each patient whether the advantages of further lowering of systolic pressure outweigh the possible risks.
(1) The SPRINT Research Group; A Randomized Trial of Intensive versus Standard Blood Pressure Control; N Engl J Med 2015; 373; 2103-2116.

(2) Report from the panel members appointed to the Eighth Joint National Committee (JNC 8); 2014 Evidence Based Guideline for the Management of High Blood Pressure in Adults; JAMA 2014; 311(5):507-520.