International Study Links Treatment Variations to Mortality in Acute MI

Hospitals in Sweden more consistently follow guideline recommendations for treating patients with acute MI than do their counterparts in the United Kingdom, according to a registry study published online August 7, 2015, ahead of print in the BMJ. That disparity may in part explain why 30-day mortality is higher for UK-based patients, the authors suggest.

Efforts to ensure consistently high-quality care across all hospitals “may not only reduce unacceptable practice variation but also deliver improved outcomes for patients with acute [MI],” write Sheng-Chia Chung, PhD, MHSc, of University College London (London, England), and colleagues.

For the study, the researchers compared the care and outcomes of acute MI patients who were treated between 2004 and 2010 while enrolled in 1 of 2 registries:

• SWEDEHEART/RIKS-HIA, covering 87 hospitals (n = 119,786 patients) in Sweden
• NICOR/MINAP, comprising 242 hospitals (n = 391,077 patients) in England and Wales

Survival Higher in Sweden

Compared with hospitals in the United Kingdom, those in Sweden had a higher median proportion of women and patients with histories of diabetes or heart failure. Also, hospital volume of acute MI patients was greater in Sweden.

The proportion of STEMI patients receiving primary PCI was higher in Sweden than in the United Kingdom (61.9% vs 34.9%), and variation among Swedish hospitals was much lower (interquartile range 16.7% vs 50.7%). Interestingly, any reperfusion for STEMI was more likely in UK hospitals—a difference driven by greater use of thrombolytic therapy. Use of revascularization for NSTEMI was lower in the United Kingdom than in Sweden (19.2% vs 34.8%) with twice the inter-hospital variation (interquartile range 21.9% vs 10.2%).

With regard to predischarge medications, between-hospital variation was lower for antiplatelet drugs than for other secondary prevention drugs in both countries. Beta-blockers were more often prescribed in Swedish hospitals than in UK hospitals, but ACE inhibitor/angiotensin receptor blocker and statin use was higher in the United Kingdom and variation greater in Sweden.

Volume-weighted 30-day mortality was lower in Swedish compared with UK hospitals (7.0% vs 10.1%) and showed less variation (2.1% vs 5.7%). From 2004 to 2010, 30-day mortality decreased from 9.3% to 6.5% in Sweden and from 12.8% to 7.6% in the United Kingdom, as did between-hospital variation, from 3% to 2.8% and from 7.5% to 5.5%, respectively. Between-hospital variation was greater for STEMI than NSTEMI patients in Sweden (2.5% vs 1.8%), but the opposite pattern was seen in the United Kingdom (5.4% vs 7.1%).

After controlling for differences in case mix, hospitals’ provision of guideline-recommended treatment explained 28.1% of the variation in 30-day mortality for Swedish hospitals and 21.6% for UK hospitals.

Lower volume-weighted 30-day mortality was observed in hospitals in the highest quarter for use of guideline-recommended treatments in both regions. Notably, primary PCI was associated with the greatest differences among hospitals in the lowest and highest quarters with mortality rates of 10.7% vs 6.6% in Sweden and 12.7% vs 5.8% in the United Kingdom. For STEMI cases specifically, after adjustment for case mix, patients admitted to hospitals in the highest quarter had a 30% lower risk of death at 30 days in Sweden and a 32% lower risk in the United Kingdom compared with patients admitted to hospitals in the lowest quarter.

Trends Relate to Policy Changes

“In both countries, greater use of guideline-recommended treatment in hospitals was associated with smaller variation in practice,” the authors observe.

The use of primary PCI in the United Kingdom increased in 2008 and variability among hospitals there decreased, both corresponding with the launch of a national policy initiative favoring the procedure, they explain. A similar shift occurred in Sweden in 2006, “reflecting a national consensus that had moved away from thrombolytic treatment at least 2 years earlier than in the [United Kingdom],” Dr. Chung and colleagues report. 

“This 2-year delay in implementation of primary [PCI] in the [United Kingdom] seems to have had adverse consequences, judging by the favorable 30-day odds of mortality for patients with [STEMI] receiving treatment in high-use compared with low-use hospitals,” the study authors explain. Remedying this situation “has the potential to reduce the mortality risk of [STEMI] in both countries,” they say. 

On the other hand, the relatively consistent use of antiplatelet drugs in both countries with little difference in mortality between hospitals “may provide a useful benchmark for other secondary prevention drugs,” they write. “If variations between Swedish and UK hospitals in prescription of all secondary prevention drugs were reduced to the levels recorded for any platelet drugs, important reductions in variation in mortality could probably be achieved.” 

‘Canary in the Coal Mine’  

“Beyond variations in hospital treatment, multiple factors might contribute to the residual variation in mortality between hospitals, including hospital structure (staff expertise, hospital volume, resources), processes of care (treatment protocol, problem solving), and organizational culture,” Dr. Chung and colleagues explain. 

In fact, “low use of guideline-recommended treatment in [underperforming] hospitals may be the ‘canary in the coal mine’ that signals [other] difficulties in implementing high quality care,” the study authors suggest. 

Local efforts to improve care may prove challenging, however, due to “vulnerability of patients and other hospital level and regional factors,” they say. As such, “quality improvement might best be achieved not only by targeting underperforming hospitals but also by the development of system-wide initiatives with the aim of delivering equitable management across all national hospitals from time of admission through to discharge and beyond.

Source: 
Chung S-C, Sundström J, Gale CP, et al. Comparison of hospital variation in acute myocardial infarction care and outcome between Sweden and United Kingdom: population based cohort study using nationwide clinical registries. BMJ. 2015;Epub ahead of print.

Related Stories:

• Sweden Better than United Kingdom at Saving Lives of MI Patients
• PCI Use, Survival Higher in US Elderly AMI Patients vs. Sweden
• Swedish Registry: Guideline Implementation Has Lowered Mortality in AMI Patients