Arterial hypertension. Does the J curve exist? And then?
The concept that â€˜the lower the blood pressure (BP) achieved the better the outcomeâ€™ rests on the demonstration of a direct relationship between BP and incident outcomes, down to levels of 115 mmHg of systolic BP (sBP) and 75 mmHg of diastolic BP (dBP) carried out in 1 million individuals from 61 cohorts recruited between 1950 and 1990 and followed for about 14 years. The alternative to the â€˜lower the betterâ€™ concept is the hypothesis of a J-shaped relationship, according to which the benefits of reducing sBP or dBP to low values may be dangerous leading even to an increase in total mortality and/or in CV outcomes. Data from contemporary epidemiologic observations,Â (CALIBER study), showed that the relationships between rising BPÂ and increased incidence of outcomes rise continuous even over 85 years of age without the evidence of aÂ J-shapedÂ associationÂ withÂ anyÂ ofÂ theÂ outcomes at any age strata. In the English LongitudinalÂ StudyÂ ofÂ AgeingÂ study (ELSA), a tailored analysis for octogenarians showed that the increase in mortality rates associated with BP ranges appears at sBPÂ <110 mmHg and â‰¥170 mmHg.Â In randomized controlled trials (SPRINT, HYVET and INVEST), the J curve seems to concern mainly patients with anÂ extensive atherosclerotic burden, rather than. An impaired autoregulation of coronary blood flow (CBF) leading to a fall in diastolic BP and resulting in a lowering in the perfusion pressure distal to the epicardial coronary artery stenosis, can eventually leadÂ to myocardial ischemia.Â Diastolic dysfunction can concur in worsening CBF in diastole.Â These features are often seen in elderly patients with heart failure with preserved ejection fraction. The steeper position of the slope of the end-systolic elastance can lead to dramatic increases and decreases in BP for the same change in afterload or preload. This may explain why elderly hypertensives are more prone to suffer of hypertensive crisis and/or hypotension than younger hypertensives. â€œPseudo-hypertensionâ€ caused by structural sclerotic changes in the brachial artery wall may cause overtreatment related falls in blood pressure. Thus, the J curve exists but only in patients with multiple comorbidities and/or extensive atherosclerotic burden.
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