J-curve linkt bloeddruk aan meeste CV events bij CAD patiënten
J-curve defines BP link with most CV endpoints in CAD patients
Low blood pressure (BP) is associated with an increased risk for cardiovascular events in people with coronary artery disease (CAD), analysis of the TNT trial has found.
The study, which is reported in the European Heart Journal, reignites the "J-curve" controversy and suggests that targeting lower BPs does not always improve outcomes.
Franz Messerli (Columbia University College of Physicians and Surgeons, New York, USA) and team re-analyzed data from the Treating to New Targets (TNT) trial. This was a double-blind study involving 10,001 people with CAD who were randomly assigned to receive atorvastatin 10 mg or 80 mg.
For their post-hoc analysis, Messerli's team looked at the relationship between average systolic and diastolic BP (in 10-mmHg increments) during the trial and the occurrence of cardiovascular events (ie, CAD death, myocardial infarction, cardiac arrest, or stroke).
The median duration of follow-up was 4.9 years, during which 9.8% of participants suffered a primary outcome event.
The relationship between systolic BP and the primary composite outcome followed a J-shaped curve, report Messerli et al, with the risk being raised at low and high BPs.
After adjusting for baseline covariates, the risk for cardiovascular events in patients with a systolic BP of 110 mmHg or lower was similar to or higher than that in patients with a systolic BP of over 160 mmHg. The risk was lowest at a systolic BP of 146.3 mmHg.A similar J-shaped curve was seen for the relationship between diastolic BP and the primary outcome, with the risk being lowest at 81.4 mmHg.
When the team looked at secondary endpoints they found similar J-shaped curves for both diastolic and systolic BPs and the risks for all-cause mortality, death from CAD, and nonfatal myocardial infarction.
For the outcome of stroke, by contrast, the risk fell continuously with lower systolic BPs, but again was J-shaped for diastolic BP. Finally, lower BP (both diastolic and systolic) was associated with an increased risk for angina.
"It should be noted that the curve was relatively flat for BPs 140-120/80-70 mmHg, with exponential increase in the risk of primary outcome for BP 110-120/60-70 mmHg. However, for the outcome of stroke, lower was better with SBP," write Messerli et al.
They conclude: "Our findings negate the dictum that with BP, lower is always better (except perhaps for systolic BP and stroke)."