The merits of long-term oral β-blocker therapy following an MI—reduced reinfarction and mortality—are beyond question. The rationale for studying early β-blockade in COMMIT lies in its uncertain value on top of current standard treatment. When the use of intravenous β-blockers in emergency treatment of MI was studied in more than two dozen trials in the 1970s and 1980s, it did show a moderate benefit; however, those trials mainly enrolled lower risk patients. As a result of the uncertain efficacy, the use of intravenous β-blockers during acute MI varies widely throughout the world, from more than 50% of cases in Sweden, to 20% in the United States, and in fewer than 1% in the United Kingdom.
“We know β-blocker therapy is beneficial long-term in people who have heart attack or heart failure. This trial is really telling us when to start, and perhaps how to start—more gradually, more carefully, targeting people when they're stable,” he said.
Discussant Dr. Cannon said his take from COMMIT regarding early β-blocker therapy was that “one size—or dose in this case—does not fit all.”
“We really should think of avoiding IV β-blockade for patients with evidence of compromised left ventricular function, and in those patients. … Start a β-blocker after a day or two when the patient is stable,” he said. “On the other hand, low- to medium-risk patients did have a benefit in reduction of recurrent MI and VF, and this therapy was safe and beneficial in thrombolytic-treated patients, so these patients would be appropriate candidates for the IV followed by oral β-blocker.”