Tight BP control confers no additional benefit with respect to cardiovascular outcomes in patients with diabetes and CAD compared with usual control, a major trial has shown. It may actually worsen outcomes in the long-term.

The INVEST study randomly assigned 22,576 patients to two BP lowering regimens starting with verapamil SR or atenolol and adding

in an ACEI, thiazide diuretic or both. The main trial results were published in 2003 and showed no difference in cardiac outcomes between the two approaches.

This recently published post hoc analysis of the original data categorised 6,400 diabetes patients with established CAD according to the degree of BP control actually achieved. A systolic BP >140mmHg = uncontrolled, <130mm Hg = tight control and 130-140mmHg = usual control.

The primary endpoint was a composite of death, MI or stroke.

The results showed a significantly greater incidence of the primary outcome in the uncontrolled versus usual control group, 19.8% vs 12.6%, hazard ratio 1.46 (95% CI: 1.25-1.71, p<0.001) but no significant difference was seen between the usual and tight control groups, 12.6% vs 12.7%, HR 1.11 (95% CI: 0.93-1.32, p=0.24).

These findings were mirrored for all-cause mortality, 11.0% tight, 10.2% usual and 15.4% uncontrolled.

However, the slight albeit not significant increase in mortality seen in the tight versus usual control group, HR 1.20 (95% CI: 0.99-1.45, p=0.06) did reach significance over an extended period of follow up, 22.8% vs 21.8%, HR 1.15 (95% CI: 1.01-1.32, p=0.04).

The J shaped curve for BP is well documented with cardiac event rates declining with BP reduction up to a point when event rates once again begin to rise at very low pressures. It is also accepted that tight BP control results in a significant reduction in stroke and prevents microvascular events such as retinopathy and nephropathy. Certainly stroke is considerably more BP dependent than coronary heart disease. So where does all this leave us for diabetes patients with established coronary disease?

The authors conclude that aiming for a systolic BP lower than 130mmHg has no advantages over usual care and indeed could be harmful over the long term in this patient population. Although this was essentially a subgroup analysis the findings are in keeping with other trials such as ACCORD and should prompt us to exercise caution in lowering BP too aggressively in diabetes patients with CAD.

Dr Peter Savill