HYPE and TENSION in Hypertension. Debating the latest hypertension guidelines

Abstract

Background: The latest American College of Cardiology/American Heart Association (ACC/AHA) hypertension guidelines promote radical changes to hypertension management - achieving a normal blood pressure (BP) defined as <120 mm Hg systolic and <80 mm Hg diastolic in all. The “rationale” for this re-definition of hypertension remains hotly debated and has been rejected by a variety of bodies.

Method: This article approaches the hype and the tensions in hypertension from five different perspectives: (1) Physiology - pressure and flow in a pipe are related to the 4^th power of the radius, hence very small changes in radius require a significant pressure increase to maintain the same flow to maintain oxygen distribution to tissues - the cardinal function of the heart. Chronic SNS and HPA-axis activation results in persistent vasoconstriction and thus chronically elevated BP. (2) Epidemiology - BP is non-linearly distributed across the community and increases with inflammaging across the lifespan. Ethnic as well as socioeconomic factors are associated with elevated BP levels, most likely to the chronic activation of the SNS and HPA-axis with increasing disadvantage. (3) Disease, an emergent phenomenon - A complex adaptive systems understanding shows that health and disease are a “whole of system” phenomenon with a high degree of robustness. Its underlying physiological mechanisms mostly maintain a healthy functional state and only occasionally result in dysfunctional disease states. (4) Overselling risks and benefits - what matters is absolute risk and absolute benefit/harm. The misunderstanding of basic statistics, namely that large studies are required to demonstrate small differences rather than an indicator of magnitude and veracity of benefit shown by it, allows ‘snake oil merchants’ to promote interventions tapping into fear. While risk perception varies, most people regard treatments with an NNT of >30 as not worth the effort. (5) The need for wisdom in clinical care.

Results and Discussion: Peter Drucker emphasised there is a distinction between doing things right and doing the right thing. Doing the right thing requires contextualisation of data and information gleaned from clinical trials in the context of the patient in front of the clinician; many elderly people require “high BP” to maintain cerebral perfusion that allows them to think, not fall, and to maintain their independence. Hence, we should come to terms with the fact that non-linear physiological phenomena cannot be approached with a cause-and-effect mindset; that quality of life is often more important to people than the label of their morbidities and that after all the sum of all causes of mortality always add up to 100%. Conclusion: Wisdom has no easy answers, doing the right thing entails taking account of the best available data and information, being honest about the magnitude of the real benefits and the real risks of treatments, contextualising those for the context of every person and valuing his/her best-informed choice without resentment or fear.