In a recent study, people with diabetes needing the most common type of open heart surgery fared almost as well as those without diabetes while in hospital. Once discharged, however, it was a different story.
People with diabetes were more likely to have worse long-term outcomes than people without diabetes, the researchers found.
The initial hospitalization costs and costs of recovery were also higher among people with diabetes.
Heng Zhang, MD, of Fuwai Hospital in Beijing, China, led this study.
Dr. Zhang and colleagues noted that 11.3 percent of people living in the United States have diabetes, and diabetes rates are increasing.
Diabetes is a risk factor for coronary artery disease — a disease in which there is narrowing and blockage in the arteries, the tubes that carry oxygen and blood to the heart.
Many people with diabetes eventually need surgery called coronary artery bypass grafting (CABG). CABG is a procedure in which a healthy artery or vein is grafted (connected) to the blocked artery and goes around the blockage so oxygen-rich blood can make it to the heart. Several blocked arteries can be bypassed in one surgery.
For this study, Dr. Zhang and team looked at 9,240 people who had CABG at Fuwai Hospital between January 1999 and the end of 2008. Of these, 2,682 patients had diabetes and 6,558 did not.
Of those with diabetes, 375 patients managed their condition with diet alone, 481 controlled their diabetes with insulin, and 1,826 used oral medication.
The patients returned for follow-up after they were discharged from the hospital at one month, six months and 12 months, and then were seen annually. Those who did not make follow-up visits were followed up by a research nurse. Medical records were used to see how patients fared. There was follow-up data available for 96.3 percent of patients, and patients were followed for an average of 3.7 years.
While in hospital, death rates were similar for both groups — 1 percent of those without diabetes and 1.2 percent of those with diabetes.
Also while hospitalized, diabetes patients requiring insulin were slightly more likely to develop kidney failure than all other patients in the study, but this was the only in-hospital difference between diabetes patients and those without diabetes.
During follow-up, 294 patients died. Of all deaths, the incidence was 11.3 diabetes patients and 8.5 patients without diabetes per 1,000 person-years.
The diabetes patients who did not do well after their release from the hospital were those who managed their diabetes with medication or insulin. Patients whose diabetes was controlled through diet alone recovered as well as those who did not have diabetes.
It's important to note that those diabetes patients who could control their diabetes through diet alone did the best after surgery, said Dr. Barry Sears, an American biochemist best known for creating and promoting the Zone diet.
“It is not surprising that diabetic patients have greater risks than non-diabetic patients because their elevated blood sugar levels will increase inflammation throughout the body," Dr. Sears said. "What is surprising is the diabetic patients who were managing their diabetes by diet had essentially the same long-term cardiovascular outcomes after coronary bypass surgery as the non-diabetic patients. It was the cohort of diabetic patients taking drugs or insulin that had greater long-term cardiovascular problems than the non-diabetic patients. “
The study also showed that of those who had strokes after surgery, there were 31 diabetes patients and 21.7 patients without diabetes per 1,000 person-years.
Compared to patients without diabetes, those with diabetes had more major adverse cardiovascular and cerebrovascular (involving the blood vessels supplying the brain) events after their surgery. These events occurred at a rate of 52.6 diabetes patients and 40 patients without diabetes per 1,000 person-years.
The financial cost of the surgery and cost of subsequent adverse events were also higher for people with diabetes. Diabetes patients needed more medications and were more often readmitted to the hospital for adverse events, such as heart attacks or strokes, after discharge. At two years after surgery, costs for diabetes patients in the study were about $1,623 higher than for people without diabetes.
The study's authors concluded that adverse events among diabetes patients who underwent CABG were worse and cost more than those of people without diabetes. These findings have serious implications, as more people are diagnosed with diabetes all the time, the authors noted.
Dr. Sears said that since the diabetes patients in the study who did best were those who managed diabetes through diet alone, the conclusion is that long-term diabetes management by diet after coronary bypass surgery appears to be better than treatment with medications. “This may be due to the fact that those diabetic patients managing their diabetes by the diet are also probably doing more to manage their lifestyle (i.e., exercise and stress reduction) than those diabetic patients taking drugs or insulin,” he said.
“The recommendation for every diabetic patient after coronary bypass should be a much more aggressive lifestyle management program. I would think the dietary recommendations of the Joslin Diabetes Research Center at Harvard Medical School would be an excellent starting point for such patients especially since they are essentially those of the Zone Diet," Dr. Sears said.
In a commentary accompanying this study, Michael E. Jessen, MD, of the University of Texas Southwestern Medical Center in Dallas, Texas, said that this study by Dr. Zhang and team is a call to action for surgeons to think about diabetes control and costs for these patients.
“Further research is needed to test management strategies that might reduce the adverse events and decrease the costs of care in this patient population," Dr. Jessen wrote. "As the number of diabetics continues to rise and health care costs are under increasing scrutiny, these efforts should receive a high priority.”
This study by Dr. Zhang and colleagues was published May 29 in The Annals of Thoracic Surgery.
No conflicts of interest were disclosed by the authors. The study was funded by the Key Project in the National Science and Technology Pillar Program during the Twelfth 5-Year Plan Period.