Circ: Even minor surgeries may cause death in HF, AF patients

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Postoperative risks for patients with heart failure (HF) and atrial fibrillation (AF) who undergo noncardiac surgery remain poorly defined. In a retrospective study published July 19 in Circulation, researchers found that patients with HF or AF who undergo major or minor noncardiac surgery are at a significantly higher risk of death and rehospitalization than patients with coronary artery disease (CAD). However, the accompanying editorial questioned the conclusions, due to the limited nature of the study data.

In the study, the authors noted that HF and AF are becoming increasingly prevalent, and longer survival of these patient groups suggests that noncardiac surgeries will be required.

Sean van Diepen, MD, and colleagues at the University of Alberta in Edmonton, Canada, linked three administrative databases to identify 38,047 patients with four cardiac conditions who underwent major or minor noncardiac surgery between April 1, 1999, and Sept. 31, 2006, in Alberta. The four mutually exclusive cohorts consisted of non-ischemic HF (NIHF, 7,700 patients), ischemic HF (IHF, 12,249 patients), CAD (13,786 patients) or AF (4,312 patients). The primary clinical outcome was 30-day postoperative mortality. Secondary clinical outcomes were the frequency and cause—cardiac and noncardiac—of 30-day hospital readmission.

The authors reported that the unadjusted 30-day postoperative mortality was 9.3 percent in NIHF, 9.2 percent in IHF, 2.9 percent in CAD and 6.4 percent in AF (each vs. CAD). Among patients undergoing minor surgical procedures, the 30-day postoperative mortality was 8.5 percent in NIHF, 8.1 percent in IHF, 2.3 percent in CAD and 5.7 percent in AF. After multivariable adjustment, postoperative mortality remained higher in NIHF, IHF and AF patients than in those with CAD (NIHF vs. CAD: 2.44 to 3.48; IHF vs. CAD: 1.70 to 2.31; AF vs. CAD: 1.34 to 2.14).

The 30-day rehospitalization rate was 15.5 percent in the NIHF cohort, 15.3 percent in the IHF cohort, 13.3 percent in the CAD cohort and 15.6 percent in the AF cohort. Both NIHF and IHF patients were more likely to be readmitted for cardiac reasons than those with CAD (NIHF vs. CAD; IHF vs. CAD). Within each cohort, the 30-day postoperative readmission with a cardiac diagnosis was 1.8 percent with NIHF, 3.5 percent with IHF, 0.7 percent with CAD and 0.4 percent with AF.

In all cohorts, the most common reason for cardiac readmission was related to the underlying cardiac disease, according to the researchers.

The 30-day postoperative mortality for patients who underwent urgent and emergent surgeries was higher than postoperative mortality for patents who underwent elective and outpatient surgeries. NIHF and IHF patients faced an overall higher risk than patients with CAD or AF, including cases involving minor surgery. The 30-day mortality rate for minor surgeries was 8.5 percent in the NIHF cohort, 8.1 percent in the IHF cohort, 2.3 percent in the CAD cohort and 5.7 percent in the AF cohort.

The authors also noted an association with timing of surgeries. Patients in all four cohorts who underwent surgery within four weeks of their cardiac diagnosis had a higher mortality rate than those who underwent surgery four weeks or more after diagnosis. The HF and AF cohorts showed a two-fold and three-fold postoperative mortality greater rate than the CAD cohort among patients who underwent surgery within four weeks.

“Ours is the first study to report outcomes in HF patients undergoing minor procedures,” the authors wrote. “HF patients are at significantly higher risk than CAD or AF patients, and their absolute risks are substantially higher than previously anticipated. Although the observed rate may have been elevated by inclusion of procedures performed on critically ill inpatients, the four-week postprocedural mortality in HF and AF patients undergoing strictly outpatient minor procedures was still in excess of 4 percent and 2 percent, respectively.”

They continued, “These analyses suggest that HF patients are not at low risk of adverse postoperative events even when they undergo low-risk outpatient surgical procedures such as colonoscopy or cystoscopy.”

In an accompanying editorial, Aldo P. Maggioni, MD, of the AMNCO Research Center in Florence, Italy, who praised the study for adding to clinicians’ knowledge base for reducing postoperative risk in HF and AF patients, also cautioned that the study’s limitations prevent the findings from being generalized in the patient setting. The limitations included a limited number of clinical variables in the data.

Maggioni wrote that with respect to HF, “the classification in ischemic/nonischemic is too vague,” adding that AF cohort selection relied on a definition of a prior admission with a primary diagnosis of AF, but in clinical practice the majority of AF patients do not need hospitalization to manage the condition. “Only the subset of hospitalized patients was considered, and the generalization of the message to all patients with atrial fibrillation is not appropriate,” he argued.

He identified another major limitation as a lack of an appropriately defined cause of death. “In this context, the causes of death have been not appropriately defined and validated; therefore, it is very difficult to plan strategies that could be useful in the postoperative risk reduction,” Maggioni wrote. “This aspect is particularly true for patients with atrial fibrillation for whom anticoagulation therapy or heart/rhythm control strategies could be more specifically and appropriately planned, where a better definition of the poor postoperative outcomes would be useful.”

The authors acknowledged limitations related to the use administrative data and concluded that future research should focus on identifying perioperative risk factors and developing risk predictive models for HF and AF patients.

The researchers reported sources of funding included the Canadian Institutes of Health Research and the Alberta Heritage Foundation for Medical Research.