N.S. officials examining 'statistically significant' results for post-bypass surgery mortality

Officials with Nova Scotia Health are examining data showing a post-operative mortality rate above the national average for a certain heart surgery. (Radio-Canada - image credit)
Officials with Nova Scotia Health are examining data showing a post-operative mortality rate above the national average for a certain heart surgery. (Radio-Canada - image credit)

Officials at Nova Scotia Health are reviewing data that show a higher mortality rate after a common heart surgery procedure compared to the national average.

This summer, the Canadian Institute for Health Information (CIHI) released its latest cardiac care quality indicators report. The document reviewed three years of data from hospitals across the country, considering six outcome indicators. From that work, risk-adjusted results are produced.

Although the results for the heart surgery program at the Queen Elizabeth II Health Sciences Centre in Halifax were within the national average for five of the categories, its result for 30-day in-hospital mortality after isolated coronary artery bypass graft surgery, or CABG, was deemed statistically significant.

Sunita Karmakar-Hore, manager of the health system performance reporting team at CIHI, said results are deemed statistically significant when both the upper and lower confidence interval for risk-adjusted rates fall either above or below the national average. The national average for 30-day in-hospital mortality after isolated CABG is 1.5 deaths per 100 patients. CIHI found the interval in Halifax to be between 2.3 and 4.6.

'It's really a flag'

Karmakar-Hore said hospital officials should be paying attention to their data if a result is statistically significant, particularly if it's in an unfavourable direction.

"It's really a flag for the hospital to dig deeper into their data to really understand what's going on with the health-care of those patients and to understand whether there could be process or quality improvements that could be made to improve the result," she said in a recent interview.

Dr. Gail Darling, head of the department of surgery at Dalhousie University and the department of surgery head for the health authority's central zone, said officials are doing that work now.

Darling said she understands why people might have concerns when they hear negative things about the health-care system, but the important thing for the public to know is the results are being investigated.

"I don't think the alarm bells should be going off, by any means, but we should never ignore any of these signals," she said in an interview.

Nova Scotia Health
Nova Scotia Health

Darling said results have been good in the past and officials would look at why that seems to have changed. Coronary artery bypass graft surgery is a procedure used to treat coronary artery disease by bypassing a blockage using a piece of a healthy blood vessel from another part of a patient's body.  About 400 of them are performed each year in Halifax.

Although the CIHI data is risk adjusted, Darling said it doesn't account for all variables. She said the hospital's own database incorporates other factors that she believes more accurately reflects the risk profile of the site's patients.

With that accounting, Darling said outcomes for the procedure at the QEII are "actually pretty good and, in fact, better than expected based on the kinds of patients we have."

Patients are 'more acute, more ill'

Nova Scotia has a high proportion of smokers, diabetes and people who are overweight, all of which contribute to patient risk factors, said Darling. More than half the patients who receive the procedure in Halifax are inpatients, meaning they've come in with symptoms, have been investigated and are sick enough to have to stay in hospital and wait for surgery, said Darling.

The stat is about 30 per cent in the rest of Canada, she said.

"For us, it's probably closer to 60 per cent," said Darling. "So these patients really are more acute, more ill."

A spokesperson for CIHI said the report serves as an important first step in measuring and improving cardiac care in Canada. Risk factor and indicator selection was guided by input from an expert advisory group that included representation from the Canadian Association of Interventional Cardiology and the Canadian Society of Cardiac Surgeons.

Darling said the hospital would look at individual surgeon outcomes to determine if there is an across-the-board issue or if there are outliers.

The effects of workplace on outcomes

Health officials in Halifax reviewing the results are doing so as the cardiac surgery department is undergoing an external review.

That follows ongoing reports about poor behaviour on the part of some members of the unit, including surgeons. Past division reviews have indicated a lack of progress putting an end to destructive behaviour and an inability to bring in a code of conduct with teeth.

Darling acknowledged that such issues can have an effect on performance in a field that "really requires a high-functioning team."

"We know from business literature that high-functioning teams have the best outcomes," she said, adding that "psychological safety" is a key factor in those outcomes.

"That's definitely a question for us based on those historical reviews. The question is, is that still an ongoing problem and we're going to find out more once we get the results of that big external review."

That work is expected to be complete by the end of the month, she said.

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