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Risks of Tight BP Control May Outweigh Benefits

Feb 1, 2012

In diabetes patients, the stroke-preventing benefits of bringing systolic blood pressure below 130 mmHg may be offset by an increased risk of cardiac events.

In a current published study researchers say some guidelines call for “more aggressive antihypertensive treatment in diabetes”: systolic pressures below 130 mm Hg and diastolic pressures below 80 mm Hg.

But Dr. Josep Redon from Institute of Health Carlos III, Hospital Clinico Universitario, Valencia, Spain and colleagues say that in a post hoc analysis of data from the ONTARGET investigators, “The relationship between blood pressure and overall cardiovascular risk had a similar pattern in diabetic and nondiabetic patients over a wide range of baseline and in-treatment blood pressure values.”

“We can suggest that as far as the relationship with blood pressure is concerned there may be no reason to consider diabetics separately from other high-risk patients.”

The primary endpoint (a composite of cardiovascular death, myocardial infarction, stroke, or hospitalization for congestive heart failure) occurred in significantly more diabetics than nondiabetics (20.2% vs 14.2%). The secondary outcomes (each of the components of the composite endpoint) were also significantly more common in diabetic patients.

Diabetic patients had a higher risk of the primary outcome and of all its components than nondiabetic patients for all systolic blood pressure quartiles.

In both groups, the risk of stroke was higher in the top two quartiles of systolic blood pressure than in the lowest quartile, but there was no relationship in either group between baseline systolic blood pressure and the incidence of the other events.

As for the relationship between blood pressure on treatment and outcome, there was no evidence of any adverse effect of low systolic blood pressure on any cardiovascular outcome, except for cardiovascular mortality, which was significantly increased in patients with a baseline systolic blood pressure below 130 mm Hg who had the greatest systolic blood pressure reduction.

When in-treatment systolic blood pressure was examined by decile, there was a progressive reduction in the incidence of stroke down to 115 mm Hg systolic blood pressure, whereas there was a J-curve relationship for the other outcomes. For cardiovascular death, the nadir of the J-curve was around 135.6 mm Hg for diabetic patients and 133.1 mm Hg for nondiabetic patients.

For diastolic blood pressure, the primary outcome was most common in patients with the lowest or highest in-trial diastolic blood pressure (for both diabetic and nondiabetic patients), regardless of the systolic blood pressure.

What are the therapeutic implications of these findings? “In both diabetic and nondiabetic patients, progressively greater systolic BP reductions were accompanied by reduced risk for the primary outcome only if baseline systolic BP levels ranged from 143 to 155 mm Hg,” the authors say.

They continue, “Around or below an initial systolic blood pressure of 130 mm Hg, antihypertensive treatment should be implemented with caution because of the possibility of untoward cardiac effects that could counterbalance the beneficial consequences of aggressive blood pressure reduction for stroke. This might also apply to diastolic blood pressure values of 67 mm Hg or less.”

“Clearly,” they add, “more evidence from prospective trials is necessary to learn whether high-risk diabetic patients with blood pressure levels between 130 and 140 mm Hg should be treated to lower blood pressure levels.”

J Am Coll Cardiol 2012;59:74-83.