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Intensive control of SBP among patients with diabetes, CAD not associated with improved outcomes, analysis reveals

Tuesday, July 13 2010 | Comments

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What's This? Among patients with diabetes and coronary artery disease (CAD), a systolic blood pressure (SBP) <130 mm Hg is not associated with improved outcomes relative to an SBP ranging from 130 mm Hg to <140 mm Hg, according to an analysis of data from the International Verapamil SR-Trandolapril Study (INVEST).
 
The authors of the analysis noted that hypertension guidelines currently recommend treating patients with diabetes to achieve an SBP <130 mm Hg. To further assess the merits of this lower BP goal, they evaluated the associations between achieved SBP and outcomes in 6,400 of the INVEST participants who were aged 50 years or older and had both diabetes and CAD.
 
During INVEST, the participants were randomized to receive treatment with either a calcium channel blocker-based treatment strategy or a beta blocker-based treatment strategy, with the goals of treatment being an SBP <130 mm Hg and a diastolic BP (DBP) <85 mm Hg. In the current analysis, the researchers categorized patients as having tight SBP control (<130 mm Hg), usual SBP control (130 to <140 mm Hg), or uncontrolled SBP (>=140 mm Hg) based on achieved SBP during treatment.
 
During 16,893 patient-years of follow-up, 12.7% of the tight-control group, 12.6% of the usual-control group, and 19.8% of the uncontrolled group experienced a primary outcome event, which was the first occurrence of all-cause death, nonfatal myocardial infarction, or nonfatal stroke.
 
In an adjusted analysis, the patients with uncontrolled SBP were significantly more likely to experience a primary outcome event than were those with usual SBP control (hazard ratio [HR], 1.46 [95% CI, 1.25-1.71]; P<.001), but there was no significant difference between the tight-control and the usual-control groups (HR, 1.11 [95% CI, 0.93-1.32]; P=.24).
 
In an analysis of all-cause mortality in particular, there was again no significant difference in risk between tight and usual control (adjusted HR, 1.2 [95% CI, 0.99-1.45]; P=.06). However, in an extended follow-up analysis in which the researchers searched the National Death Index to determine rates of all-cause death among the U.S. INVEST participants during the 5-year period following the study, tight SBP control was actually associated with a significantly greater risk of death as compared with usual control (22.8% vs 21.8%; adjusted HR, 1.15 [95% CI, 1.01-1.34]; P=.04).
 
Moreover, among all 2,255 participants in the analysis with tight SBP control, the risk of all-cause mortality at 2 years seemed to increase as SBP decreased. Relative to the participants with an SBP ranging from 125 to <130 mm Hg, the adjusted HR for all-cause death was 1.63 (95% CI, 0.97-2.75; P=.06) among those with an SBP ranging from 110 mm Hg to <115 mm Hg and 2.18 (95% CI, 1.17-4.09; P=.02) among those with an SBP <110 mm Hg.
 
In a review of previously published evidence addressing the potential value of intensive BP control, the study authors acknowledged that some landmark trials--including the United Kingdom Prospective Diabetes Study (UKPDS)--seemed to support recommendations for lower BP goals, while the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial showed no differences between an intensive and standard BP strategy in rates of a first major cardiovascular event, all-cause mortality, or cardiovascular mortality.
 
In a comparison of these 2 trials, the researchers noted that mean baseline SBP in the ACCORD trial was lower than mean SBP achieved in UKPDS, suggesting that the benefit observed with a tight-control strategy in the latter trial was likely due to SBP declining from 160 mm Hg to 144 mm Hg, with less benefit in ACCORD where mean SBP declined from 139 mm Hg to 119 mm Hg with an intensive treatment strategy.
 
In addition, the researchers reviewed data from the Appropriate Blood Pressure Control in Diabetes (ABCD) trial, which showed a significant reduction in the risk of all-cause mortality with intensive BP control. In this trial, they noted, enrolled patients were younger than those in the current INVEST analysis and only half had a history of cardiovascular disease, suggesting that these participants might have been less susceptible to any adverse effects of lower BP. By contrast, in the Irbesartan Diabetic Nephropathy Trial (IDNT), in which 60% of participants had a history of heart disease, the data showed that participants who achieved an SBP <=120 mm Hg had a significantly increased risk of death relative to participants who achieved an SBP >120 mm Hg.
 
Given the findings from the current study and their review of research to date, the authors of the INVEST analysis concluded, "At this time, there is no compelling evidence to indicate that lowering systolic BP below 130 mm Hg is beneficial for patients with diabetes; thus, emphasis should be placed on maintaining SBP between 130 [mm Hg] and 139 mm Hg while focusing on weight loss, healthful eating, and other manifestations of CV morbidity to further reduce long-term cardiovascular risk." (Cooper-DeHoff RM, et al. JAMA 2010;304:61-68.)

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