Despite advances in the treatment of acute myocardial infarction, 30-day rehospitalization rates remained fairly constant from 1987 to 2010.
Rehospitalizations ranged from a high of 23% in 1987 to a low of 19% in 2010 – but that difference was not statistically significant, Dr. Shannon Dunlay and her colleagues reported in the July 3 issue of Annals of Internal Medicine
During that period, treatment advances were obvious. There was a significant decrease in fibrinolysis and significant increases in angiography, reperfusion, and percutaneous coronary intervention (PCI). But those improvements didn’t affect 30-day readmission rates, and in fact, seem to be a driver of them, the researchers, led by Dr. Dunlay, a cardiology fellow at the Mayo Clinic, Rochester, Minn., wrote.
"Angiography, reperfusion, and revascularization are mainstays of therapy in acute MI, and complications are associated with a high risk for rehospitalization," they wrote.
They also noted that "as the prevalence of such comorbid conditions as diabetes and COPD [chronic obstructive pulmonary disease] increases over time, rehospitalizations after acute MI may continue to shift toward noncardiovascular causes." Other medical comorbidities, including hypertension, hyperlipidemia, and obesity, were also significantly associated with readmission rates (Ann. Intern. Med. 2012; 157:11-18).
The authors found that 43% of the readmissions were related to the incident heart attack or its treatment, 30% were unrelated, and a relationship was unclear in 27%.
The review encompassed 3,010 cases extracted from the Rochester Epidemiology Project, a database that links patient records from three facilities in Olmstead County, Minn. The patients’ mean age was 67 years and did not change over the study period.
In-hospital survival improved over time (89% in 1987 and 96% in 2010).
There were significant changes in comorbid conditions from 1987 to 2010, including hypertension (61%-69%), hyperlipidemia (50%-68%), diabetes (22%-24%), and obesity [a body mass index of at least 30 kg/m2] (33%-38%).
Treatment changes included a significant decrease in fibrinolysis (28%-1%), and significant increases in reperfusion/revascularization (64%-69%), PCI (51%-63%), and angiography (76%-85%). The median length of stay dropped from 5 days to 3 days – also a significant change.
Increasing rates of complications were associated with these changes in treatment, the records showed. Ten percent of patients who underwent PCI had a complication. These included vascular or bleeding complications (6%), stroke (0.3%), and renal failure (5%). Of the vascular or bleeding complications, 63% were access site complications, most of which were groin hematomas.
The complication rate was low among patient receiving fibrinolysis (2%). Two percent of patients who had a coronary artery bypass graft (CABG) procedure had an associated stroke. The complication rate was 8% among patients who had angiography, with or without reperfusion. Most of those (5%) had acute renal failure, with three patients requiring dialysis. The other patients had vascular or bleeding complications.
Thirty-day rehospitalizations were required in 561 patients (19%), who were admitted a total of 643 times – 484 patients were admitted once, 72 twice, and 5 three times. Three percent (87) of the patients died within 30 days; among these, 19 were in a readmission when they died.
Readmission rates were 23% from 1987 to 1992; 22% from 1993 to 1998; 22% from 1999 to 2004; and 19% from 2005 to 2010.
The most common reasons for rehospitalization were ischemic heart disease (15%), respiratory or other chest symptoms (10%), heart failure (9%), and cardiac arrhythmias (6%). Other reasons included procedural complications (92%); fluid/electrolyte problems (2%); and hypotension, pneumonia, embolism/thrombosis, and stroke or transient ischemic attack (about 1%) each.
Angiography was performed in 24% of readmissions and PCI in 9%. Of these, 25% were repeat PCIs of the same vessel.
There were 44 CABG procedures among the readmitted group (28 planned). Forty-five percent of those undergoing a revascularization had been treated medically during their initial hospitalization.
Some treatments significantly increased the risk of 30-day readmission; most of that association was driven by procedural complications:
• Angiography with complications: hazard ratio, 2.40.
• Reperfusions with revascularization, with complications: HR, 2.12.
Some medical comorbidities also showed significant associations with readmission:
• Diabetes: HR, 1.34.
• Chronic obstructive pulmonary disease: HR, 1.43.
• Heart failure: HR, 1.12.
"Compared with our previous report on rehospitalizations after incident heart failure diagnosis in Olmsted County, COPD, diabetes, and anemia were common risk factors for rehospitalization among patients with incident MI and heart failure," the authors said. These risk factors "may be of particular importance as future targets in preventing rehospitalizations in patients hospitalized with cardiovascular disease."
The National Institutes of Health sponsored the study. The researchers reported having no relevant financial conflicts of interests.