Study assesses the use of tomography in detecting coronary disease in diabetics

The test has detected a degree of arterial obstruction in 42.2% of a sample of 90 patients with no history of cardiovascular disease.

By Karina Toledo

Agência FAPESP – By using computerized tomography exams on a group of 90 diabetics with no history or symptoms of cardiovascular disease, researchers at the University São Paulo (USP) have determined that 42.2% (38) of the patients presented a degree of obstruction of the coronary arteries. In 15.5% (14) of the cases, the coronary artery disease observed was significant; in other words, the vessels were over 50% obstructed.

By comparing the test results of diabetics whose blood glucose levels were controlled with those of patients with uncontrolled diabetes, the scientists observed that in the second group, it was more common to find atheromatous plaques considered to be “vulnerable” (not calcified and also causing local vascular remodeling), the rupture of which is responsible for nearly two-thirds of all heart attacks.

The project, entitled “Diagnosis of asymptomatic cardiovascular disease in carriers of type 2 diabetes,” was coordinated by Dr. Antonio Carlos Lerario of the Hospital das Clínicas of the USP School of Medicine, with funding from FAPESP.

“Our objective was to evaluate whether this non-invasive diagnostic imaging method would be as effective as the standard method in the early detection of coronary artery disease in diabetic patients. In this group, acute myocardial infarction and stroke are the main causes of death. In addition, the incidence of these problems is higher than that in the general population,” Lerario stated.

According to the researcher, previous studies had already indicated that diabetes favors the appearance of cardiovascular risk factors such as dyslipidemia and hypertension. Moreover, the disease is related to increased inflammation and oxidative stress in the cells of the endothelium, which causes a type of premature aging of the blood vessels.

According to the researcher, the most common technique currently used for assessing coronary artery disease is catheterization, which consists of inserting a long, thin and flexible tube through a blood vessel in the arm, groin or neck and threading it to the heart. This technique is invasive and requires anesthesia and the use of contrast dye to make the atheromatous plaques visible.

Computerized tomography angiography, however, is a non-invasive way to obtain a detailed three-dimensional image of the heart and blood vessels using X-rays and complex equipment controlled by high-tech computers. Among the disadvantages of using this technology are its high cost and the lengthy duration of the procedure.

“Most of the methods for diagnosing coronary artery disease are unable to evaluate the presence of vulnerable plaques. Tomography enables the detection of the atherosclerotic processes, measuring the degree of stenosis (narrowing of the vessel) and estimating the amount of calcium in the plaques,” Lerario explained.

Another possibility would be to conduct an intravascular ultrasound, a type of catheterization in which a miniaturized ultrasound probe is attached to the end of the catheter. However, according to Lerario, this method is even more expensive than tomography and requires the examiner to be highly skilled.

Assessment

The study was conducted on male and female diabetics who were monitored at the HC-USP outpatient facility, although only half had their blood glucose under control. The patients ranged in age from 40 to 65 years, but all had been diagnosed as diabetic less than 10 years ago.

All patients had undergone a clinical examination and an electrocardiogram stress test that revealed no cardiovascular problems. Computerized tomography angiography indicated that 42.2% of the 90 patients had a certain degree of obstruction. When considering only the group with uncontrolled blood glucose levels, the rate increased to 60%.

The rate of patients with significant obstruction was 15.5% when considering all diabetics, and this percentage jumped to 24.4% when considering only those with uncontrolled blood glucose levels. This group also included a higher number of affected coronary segments and non-calcified plaques, which are considered to be higher risk.

According to Lerario’s assessment, the study did not present enough robust evidence to recommend the use of computerized tomography as routine diagnostic test in these cases; to do so would require additional studies with a larger patient sample.

Meanwhile, said the researcher, the results proved that tomography is able to diagnose coronary artery disease as precisely as catheterization, and less invasively. “Furthermore, the results show that a small plaque can sometimes be more dangerous than a large one. I think that the key message is that not only does the level of obstruction need to be taken into account when assessing risk but also the type of plaque,” Lerario stated.