Some Australian heart failure patients with reduced ejection fraction (HFrEF) are still not getting guideline-recommended treatment, and researchers are trying to figure out why.

A retrospective study of 989 hospitalised HFrEF patients revealed “large evidence-practice gaps” in condition management — and particularly, angiotensin converting enzyme inhibitor/angiotensin II receptor blocker (ACEI/ARB) and aldosterone antagonist use — despite their indications, guideline endorsement and known benefits.

While contraindications and drug intolerance may account for some of these gaps, there’s plenty they don’t explain.

Identifying and understanding gaps and their drivers could open “potential avenues for improved HFrEF management”, the authors suggest.

Where are the gaps? 

Published in Internal Medicine Journal, the study assessed medication and device use in patients admitted to one of six Sydney hospitals between 2015 and 2016 against local and international guidelines.

It found that beta-blocker and diuretic use was “high among eligible patients” (88% actual use/94% recommended and 88%/99% respectively), yet ACEIs/ARBs and aldosterone antagonists were underprescribed (66%/89% and 41%/77%).

Automated internal cardiac defibrillators (AICDs) and cardiac resynchronisation therapy (30%/66% and 13%/29) were also underused in eligible patients, the authors reported.

Over one-year follow-up, 15% of patients died and 44% were readmitted to hospital at least once.

What’s driving them?

“This study is the first comprehensive audit of physician adherence to HFrEF therapy guidelines in Australia, accounting for individual patient indications and contraindications,” the authors wrote.

“This enabled estimation of evidence-practice gaps sizes for specific therapies, highlighting potential avenues to improve HFrEF management.”

They wrote that previous studies on Australia’s guideline adherence compared prevalence of therapy use to other international cohorts and were unable to grasp “the true magnitude of evidence-practice gaps” based on individuals’ indications and contraindications.

Even as the latter approach showed strong guideline adherence around beta blocker-use, 15% of patients received an agent without a demonstrated benefit in HFrEF.

“Immediate-release metoprolol tartrate was the most common. This is despite trial data showing statistical equivalence to placebo and inferiority to carvedilol in terms of mortality risk. This is in contrast to slow-release metoprolol succinate, which appears to have a similar mortality benefit to other HF-specific beta-blockers,” the authors wrote.

The larger gap in ACEI/ARB use may be partly explained by undocumented contraindications and intolerance, as well as “a local reluctance to initiate an ‘antihypertensive therapy’ in normotensive HFrEF patients, despite guidelines recommending therapy without reference to blood pressure apart from symptomatic hypotension”.

Similarly, drug intolerance may have contributed to reduced aldosterone antagonist use, since the evidence-practice gap was most-pronounced in patients with pre-existing heart failure. However, “a perception that these agents have similar indications to loop and thiazide diuretics, despite evidence of robust improvements in HFrEF outcomes independent of fluid overload or having been previously reserved for treatment of more severe heart failure” may have played a role in their low overall use.

“Given the magnitude of the evidence-practice gap and low treatment cost, aldosterone antagonists are a particularly attractive area of focus to improve HFrEF management.”

The remaining gaps “may reflect a reluctance to begin multiple therapies in an acute setting” and infrequent therapy initiation in an outpatient setting.

Regarding medical devices, “increased implementation may be an important focus for improving HFrEF management in Australia”, although it may be restricted to two-thirds of patients with an underlying ischaemic aetiology, they suggested, noting that the DANISH study found “no all-cause mortality benefit of AICDs in [non-ischaemic] cardiomyopathy”.

The study, with its bold claims about its ability to better define evidence-practice gaps, could have overestimated their size, hobbled by its retrospective nature, and inability to capture undocumented contraindications, New York Heart Association class, frailty and overall prognosis.

Nonetheless, the gaps do exist and present potential paths to better HFrEF management, the authors concluded.