J Am Coll Cardiol. 2005;45(1):43-49.
Background
Coronary artery disease (CAD) is the most common cause of death among diabetic patients. CAD is more likely to be silent in this group, and a high prevalence of abnormal and high-risk single-photon emission computed tomography (SPECT) imaging scans has been shown in asymptomatic diabetic patients.
Objective
The purpose of this study was to identify a subset of asymptomatic diabetic patients who would benefit most from screening SPECT imaging and to examine angiographic findings and prognosis in these patients according to their SPECT imaging categories.
Methods
Data from a nuclear cardiology database and charts were reviewed to screen for asymptomatic diabetic patients. A total of 1427 patients met the eligibility criteria and were included in the study. SPECT images were graded by consensus of 2 experienced observers using a 5-point scale. Results of coronary angiography (within 6 months) and long-term outcomes were collected.
Results
The study population consisted predominantly of middle-aged obese males with a high prevalence of other risk factors. Peripheral arterial disease (PAD) was present in 31% of the cohort. An abnormal stress SPECT imaging scan was seen in 58% of these patients, with 18% of the scans considered as high risk. Seven variables were shown to be independently associated with a high-risk scan: presence of Q waves on electrocardiogram (ECG), PAD, glycosylated hemoglobin, male gender, age, pharmacologic stress testing, and low-density lipoprotein cholesterol. Of these, ECG Q waves and presence of PAD demonstrated the strongest associations. Coronary angiography was performed in 49% of patients with high-risk scans. Of these, 61% had left main, 3 vessel, and/or proximal left anterior descending artery disease. Annual mortality rates for patient subsets categorized by SPECT imaging scans were as follows: 5.9% for high risk, 5.0% for intermediate risk, and 3.6% for low risk. Annual mortality rate in patients without ECG Q waves or PAD and with a completely normal SPECT imaging scan was lower but was still 2.9%.
Conclusion
High-risk findings on stress SPECT imaging were present in 18% of asymptomatic diabetic patients without known CAD. Patients with high-risk scans had a high prevalence of severe CAD and a high annual mortality rate. Asymptomatic diabetic patients with ECG Q waves and PAD may benefit the most from CAD screening.
Comments
Diabetic patients pose a challenge to physicians in providing preventive care in the setting of a high incidence and prevalence of occult CAD. This study suggests a role for screening stress SPECT imaging in selected asymptomatic diabetic patients. It should be noted however that the finding of a normal SPECT imaging scan does not ensure significantly lower risk for future cardiac events in this cohort. Hence, "low risk diabetic patient" may be a contradiction in terms, and all diabetic patients warrant aggressive preventive care and risk factor modification. The cost-effectiveness of screening for occult CAD in this group will need to be addressed.