The sooner the beta blockers (BBs) are instituted in patients with myocardial infarction (MI), or heart attack, the better their chances of survival, says a new multi-institute clinical trial by French researcher Dr Etienne Puymirat et al.
Dubbed “life-saving medications”, the clinical benefits of beta blockers in heart failure are undisputed. These drugs resume cardiac rhythm, reduce high blood pressure and protect the heart from another heart attack.
Yet, it has been decades since the effects of beta blockers have been studied in acute myocardial infarction (AMI), albeit the drugs in question are routinely prescribed in AMI patients. Besides, doctors often wonder if BBs should be prescribed for longer duration, say for a year or more, in AMI patients without a heart failure, particularly when rest of the heart functions are preserved.
To dig further into the conundrum, Dr Etienne Puymirat, a cardiologist at European Hospital Georges Pompidou, France, and colleagues, decided to conduct a study – not new or unique in its content but perhaps first to weigh the long-term benefits of BBs in post-AMI in more than a decade.
The researchers collected and analyzed a one-month data from 2,679 patients admitted to various hospitals and centers throughout the country in October 2005. All patients had an acute episode of MI but none had a heart failure or left ventricular systolic dysfunction. Of all the patients, BBs were prescribed in 77% at the time of or within 48 hours of admission; 80% were prescribed BBs at the time of discharge and 89% were still using the drugs by the end of one year.
Researchers noted that both the rate of death and 30-day mortality was far lower in patients prescribed BBs early on — 2.3% vs 8.6% in patients who did not take BBs. When researchers followed up with the patients for one year, they found that prolonged use of BB or its discontinuation after one year did not in any way increase the risk of death among the subjects. It remained far lower than in patients who were not prescribed BBs at the time of discharge — 3.4% vs 7.8%.
Those who continued taking BBs for one whole year even had a lower rate of death after 5 years compared to those who quit them — 7.6% vs 9.2%. Moreover, patients who discontinued BBs after one year required fewer secondary prevention drugs.
The study has its limitations though. For one, it was performed on a limited number of patients. For another, the effects of BBs were studied only in “less severely ill” patients. Most severely ill patients with AMI require emergency measures and less often receive BBs.
The prospective trial was recently published in the BMJ.
Beta Blockers And Divergences Between The European and American Guidelines
Beta blockers are one of the most widely prescribed classes of drugs to treat hypertension, angina, heart attack and heart failure. BBs work by blocking beta receptors located mainly in heart and blood vessels, thereby blocking the effects of noradrenaline – a neurotransmitter that “ups” heart. By blocking beta receptors, BBs lower your heart’s demand for oxygen and let it switch back to its normal rhythm.`
Despite being ubiquitously used for various heart conditions and risk factors, there exists a chasm between American and European guidelines. The Joint National Committee (JNC), US, recommends a diuretic to be used as first-line of treatment for hypertensive patients, whereas the European guidelines do not differentiate between different classes of anti-hypertensive drugs including ACE-inhibitors, beta blockers, diuretics and calcium channel blockers. Hypertension is a major risk factor for MI and renal failure.
There exists a clear agreement in one aspect though, both American and European guidelines endorse BB as the cornerstone of treatment for HF. BBs sit cozily at the top slot with ACE-inhibitors.
As for AMI, the American College of Cardiology and American Heart Association (ACC/AHA) recommend an early use of BB in high risk patients.
When is it OK to Discontinue Beta Blockers In AMI Patients With Normal Systolic Function?
The study at hand vouches for an early use of BBs in patients but when is the time to stop? There exists no clear recommendation regarding the appropriate duration of BB’s use in AMI patients although the ACC/AHA seems to endorse an indefinite use of BB to prevent secondary AMI but only in a specific set of patients, low risk (class IIa). The recommendation is based on limited data though. The paucity of data suggests a need to re-evaluate the recommendations.
A review published some years ago examined the factors that shaped up the current guidelines and concluded the data upon which these recommendations are based is conflicting and there is no rationale to continue BB for more than one year post-AMI. The prolonged use would not benefit low-risk patients or those with preserved left ventricular systolic function.
The new French study validates the review — all stable AMI patients should receive BB to abate chest pain and to reduce secondary risk of heart attack but the use beyond one year has limited or no benefits. For chronic use, statins, a class of cholesterol-lowering drugs, are effective.