Providers not following guidelines for post-AMI aldosterone antagonist use

Although rates of aldosterone antagonist use are increasing slightly over time, the vast majority of acute MI patients eligible for treatment fail to receive it at hospital discharge. The study authors wrote that the reason for this discrepancy between guideline-based therapy and actual prescribing patterns is unclear and should be further studied.

After acute MI, patients with reduced left ventricular ejection fraction (EF) are at increased risk of recurrent cardiovascular events, arrhythmias, heart failure and mortality. Aldosterone antagonist therapy improves survival in patients with chronic heart failure and depressed EF, as demonstrated by the EPHESUS trial (N Engl J Med 2003;348:1309-1321). The American College of Cardiology (ACC)/American Heart Association (AHA) STEMI guidelines published after the EPHESUS trial gave the use of aldosterone inhibitors in post-STEMI patients with an EF at least 40 percent and either symptomatic heart failure or diabetes without contraindications (renal dysfunction, hyperkalemia) a Class I recommendation.

In this study, Andrew N. Rassi, MD, of the cardiology division at Massachusetts General Hospital in Boston, and colleagues analyzed data from the AHA’s Get with the Guidelines–Coronary Artery Disease nationwide database for 81,570 post-AMI patients from 219 hospitals between 2006 and 2009, of whom 11,255 were eligible for aldosterone antagonist therapy.

Among the eligible patients, 9.1 percent were prescribed an aldosterone antagonist at discharge. From January 2006 to December 2009, the use of aldosterone antagonists increased from 6 to 13.4 percent.

When confining the analysis to 144 hospitals with at least 10 patients meeting ACC/AHA guideline criteria, the researchers found that aldosterone antagonist prescription by hospital remained variable (median, 7 percent; range, 0 to 40 percent). In these 144 hospitals, the median number of patients eligible for aldosterone antagonists was 42.5.

Patient and hospital characteristics independently associated with prescription of aldosterone antagonists were a history of diabetes, heart failure, coronary revascularization and larger hospital size. Those with a history of kidney dysfunction, tobacco abuse and higher EF were less likely to be prescribed an aldosterone antagonist.

Possible explanations for the disconnect between guideline recommendations and clinical implementation, according to Rassi et al, include concern for safety (kidney dysfunction/hyperkalemia), effectiveness of laboratory monitoring, misunderstanding of aldosterone-blocking benefits as opposed to a potassium-sparing diuretic, evidence of use based on a single randomized, multicenter trial and plans to initiate therapy after hospital discharge once ACE inhibitors/ARB doses have been up-titrated. However, they added that the “reason for this discrepancy between guideline-based therapy and actual prescribing patterns is unclear and should be further studied.”

In the accompanying editorial, Wilbur Y.W. Lew, MD, of the cardiology section at the VA San Diego Healthcare System, and Anthony N. DeMaria, MD, acknowledged that the reasons underlying this wide disparity between a Class IA recommendation and clinical practice are “not known. However, the possibilities may be related to barriers to the awareness, acceptance or implementation of the guideline.”

Yet, they wrote a lack of awareness is “unlikely” because more than 90 percent of patients received other guideline-recommended therapies including aspirin, beta-blockers, ACEIs or ARBs and lipid-lowering therapy at discharge. “There may be less focus on recommendations that are not included in performance measures or in standard admission order sets,” they noted.  

“When there is a divergence between clinical practice and recommended guidelines, as exists in the use of aldosterone antagonists, the causes need to be identified,” Lew and DeMaria recommended. “If poor adherence results from a lack of knowledge or means of implementation, corrective measures must be taken to improve outcomes. However, it must be accepted that failure to follow guidelines by the vast majority of physicians may indicate that the evidence base is not predictive of the results that will be obtained in contemporary clinical practice.”

Therefore, they suggested that recommendations need to be re-evaluated based on how representative trial enrollees are of contemporary patients encountered by practicing physicians, newly emerging evidence, changes in context and a broad view of why some guidelines are not embraced by physicians and/or patients. “Resolving apparent discrepancies is fundamental to the processes by which advances in medicine and science are made,” Lew and DeMaria concluded.

The study and editorial were published Jan. 8 in the Journal of the American College of Cardiology.