To the Editor Pasternak et al1 report that the effectiveness of metoprolol succinate and carvedilol in patients with heart failure is similar. Counteracting neurohormonal hyperactivation through β-blockers represents an established cornerstone for the treatment of heart failure. However, owing to their glycometabolic effects there are some issues concerning the use of β-blockers in patients with diabetes mellitus, which account for approximately one-third of patients with heart failure.2,3 The large and accurate population study by Pasternak et al1 could be very helpful in unveiling potentially diverse outcomes in diabetic patients receiving a selective β1-adrenergic receptor blocker (metoprolol succinate) vs a nonselective β1-β2-α1–blocker (carvedilol), providing meaningful clinical and pathophysiological insights. Indeed, the different adrenergic receptors play a key role in the regulation of glucose homeostasis and insulin release.3,4 Unfortunately, the authors did not report any analysis on the group of diabetic patients, albeit clearly indicating the presence of patients receiving insulin or oral hypoglycemics.1