MONTREAL — Suboptimal glycemic control, elevated plasma osteoprotegerin, and presence of serum interleukin-6 were risk factors for progression of coronary artery calcification in a prospective study of asymptomatic patients with type 2 diabetes.
Despite having no known coronary artery disease, a significant proportion (30%) of the 398 patients followed in the study had atherosclerosis progression, Dr. Avijit Lahiri said at the annual meeting of the American Society of Nuclear Cardiology.
The study provides insight into the risk factors for progression of coronary calcification and establishes the role of combining cardiac CT for coronary artery calcium (CAC) imaging with simultaneous single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) in uncomplicated, stable, asymptomatic patients with type 2 diabetes, Dr. Lahiri said.
CAC can be used to identify patients with increased atherosclerotic burden, but it does not identify obstructive coronary artery disease, explained Dr. Lahiri, director of cardiac imaging and research at Wellington Hospital in London. Therefore, there is a need to use combined MPI to detect silent ischemia. “Interestingly, these tests had a synergistic value on prognosis,” he said in an interview. “Thus, it would be cost effective to exclude those without CAC for further testing.”
The original study included 510 patients, of whom 20 went on to have cardiac events, and 402 were willing to participate in the current follow-up study. Four scans were technically inadequate, resulting in a cohort of 398 patients. Their mean age was 53 years; 61% were male; and their average serum glycosylated hemoglobin (HbA1c) was 8%.
All patients underwent CAC imaging, as well as a clinical evaluation—at baseline and about 2.5 years later—that measured HbA1c; serum interleukin-6 and C-reactive protein; and plasma osteoprotegerin. Those with a CAC score of more than 100 Agatston units at baseline also underwent MPI using a 2-day stress-rest protocol with technetium-99m sestamibi and dipyridamole and maximum treadmill exercise. Progression/regression of coronary calcification was defined as a change in the square root-transformed volumetric CAC score of 2.5 mm
At baseline, 211 (53%) of the 398 patients had coronary artery calcification. At follow-up, atherosclerosis progression was observed in 118 (30%) patients, including 22 (5.5%) who had no calcification at baseline, Dr. Lahiri said. Regression was noted in 3 (0.8%), and there was no change in 277 (70%).
At baseline, 24 patients had an abnormal perfusion scan. Progression of ischemia was seen in 14 patients, regression in 8, and no change in 2.
In a univariate analysis, age, male gender, presence of hypertension, and baseline HbA1c were predictors of atherosclerosis progression. There was no significant association between calcium scores and serum levels of C-reactive protein or IL-6. Surprisingly, statin use was a negative predictor, Dr. Lahiri said.
In a multivariate logistic regression model, serum HbA1c was one of the most important factors influencing progression. Poor glycemic control raised the risk of progression 10.5-fold, whereas the risk increased 2.5-fold for elevated plasma osteoprotegerin and 2.1-fold for IL-6.
SPECT images show progression of atherosclerosis in the right coronary and left circumflex arteries (arrows) of a patient with diabetes over a period of 1.7 years. Photos courtesy Dr. Avijit Lahiri
The tests were synergistic on prognosis. It would be cost effective to exclude those without CAC for further testing. DR. LAHIRI