Are beta blockers really cardioprotective?

From the results of a large prospective cohort study:

Objective

To assess the relationship between use of β-blockers and all-cause mortality in patients with and without diabetes.

Patients and Methods

Using data from the US National Health and Nutrition Examination Survey 1999-2010, we conducted a prospective cohort study. The study participants were followed-up from the survey participation date until December 31, 2011. We used a Cox proportional hazards model for all-cause mortality analysis. The multivariate-adjusted hazard ratios (HRs) of the participants taking β-blockers were compared with those of the participants not taking β-blockers.

Results

This study included 2840 diabetic participants and 14,684 nondiabetic participants. Compared with diabetic participants not taking a β-blocker, all-cause mortality was significantly higher in diabetic participants taking any β-blocker (HR, 1.49; 95% CI, 1.09-2.04; P=.01), taking a β1-selective β-blocker (HR, 1.60; 95% CI, 1.13-2.24; P=.007), or taking a specific β-blocker (bisoprolol, metoprolol, and carvedilol) (HR, 1.55; 95% CI, 1.09-2.21; P=.01). In addition, all-cause mortality in diabetic participants with coronary heart disease (CHD) was significantly higher in those taking beta-blockers, compared with those not taking beta-blockers (HR, 1.64; 95% CI, 1.08-2.48; P=.02), whereas that in non-diabetic participants with CHD was significantly lower in those taking beta-blockers (HR, 0.68; 95% CI, 0.50-0.94; P=.02). A propensity score–matched Cox proportional hazards model yielded similar results.

Conclusion

Use of β-blockers may be associated with an increased risk of mortality for patients with diabetes and among the subset who have CHD.

An editorial in the same issue provided a nice perspective on the overall issue of cardioprotection attributed to beta blockers.

Several important points can be made:

The idea of cardioprotective beta blockers came from trials in post MI patients, done decades ago, showing reduced mortality attributable to beta blockers.

Those trials were conducted in the pre-reperfusion era and thus tended to involve patients with chronically occluded arteries and larger infarcts with significant scars. This represents a substantially different population compared to the post MI patients we treat today.

The idea of cardioprotective beta blockers was inappropriately extrapolated to areas of cardiovascular medicine outside these clinical trials.

The editorial concludes:

..the only ironclad indication for cardioprotection with β-blockers remains heart failure with reduced ejection fraction,11, 12 the very indication that decades ago was the only contraindication for β-blocker therapy.4