In type 2 diabetes, coronary artery disease (CAD), the major cause of mortality, is often diagnosed late because of silent myocardial ischemia (MI) (1). Asymptomatic type 2 diabetic patients, particularly those with additional atherogenic factors predisposing to a more severe coronary risk (i.e., those “at high risk”) have to be, therefore, screened for CAD (2). Exercise electrocardiogram (ECG) is the most utilized screening test; however, several type 2 diabetic patients cannot exercise because of amputations or claudicatio and, as a whole, exercise ECG is not applicable also because of fatigue, dizzines, and hypertensive response in 30% of “at high risk” type 2 diabetic patients (3). Whatever the reason for exercise inability, these patients have a higher mortality rate (4) and they particularly deserve, therefore, to be screened for CAD (2).
This study aimed to evaluate the accuracy of dobutamine stress echocardiography (DSE) in detecting severe CAD in asymptomatic “at high risk” type 2 diabetic patients who were unable to exercise. In asymptomatic type 2 diabetic patients, DSE shows a 100% positive predictive value (5), but its negative predictive value is unknown. “At high risk” was defined as peripheral vascular disease (lumen stenosis ≥40% at ultrasound Doppler) and/or two or more of the following: family history of MI before 65 years of age, albumin excretion rate (AER) >20 μg/min, hypertension (>140/90 mmHg, or antihypertensive treatment), dyslipidemia (LDL cholesterol >13.3 mmol/l, HDL cholesterol <0.9 mmol/l, or <1.1 mmol/l in male or female, triglycerides >2.26 mmol/l, or antidyslipidemic treatment), and currently smoking. Exclusion criteria were symptoms or resting ECG signs of MI, age >70 years, and severe disease with poor prognosis.
Accuracy of DSE was measured against coronary angiography (CA), defined as positive if severe coronary stenosis (SCS) (≥70% lumen reduction) was observed.
DSE and CA were independently interpreted by two “blind” investigators. According to the Helsinki Declaration, all patients gave informed consent for this study.
A total of 56 consecutive patients were recruited, but DSE was not applicable/diagnostic in 21 (37%) because of either poor transthoracic window (n = 12, 21%) or submaximal stress (n = 9, 16%). CA was performed in the remaining 35 patients (16 males and 19 females, aged 63 ± 6 years, BMI 30 ± 5 kg/m2, diabetes duration 15 ± 8 years, HbA1c 8.5 ± 2%). Of these, 72% had peripheral vascular disease, 60% family history of MI, 46% increased AER, 75% hypertension, 85% dyslipidemia, and 65% were smokers. Of the 35 patients, 19 (54%) showed SCS, 7 (20%) showed three-vessel, 6 (17%) showed two-vessel, and 6 (17%) showed one-vessel disease. No significant differences in clinical and metabolic features were observed between patients with or without SCS. Although not an aim of our study, these data indicate a high prevalence (54%) of severe CAD in asymptomatic “at high risk” type 2 diabetic patients unable to exercise. Of the 19 patients with SCS, 4 (all with three-vessel disease) were DSE positive (true positive) and 15 were DSE negative (false negative). Of the 16 patients with no SCS, 1 was DSE positive (false positive) and 15 DSE negative (true negative). Overall, DSE accuracy was 54% (i.e., sensitivity = 21% and specificity = 94%). Positive and negative predictive values were 80 and 50%, respectively.
In conclusion, our data indicate a very poor sensitivity and negative predictive value of DSE in detecting severe CAD in “at high risk ” type 2 diabetic patients unable to exercise.
Address correspondence to Dr. Simonetta Bacci, Unit of Endocrinology, Scientific Institute “Casa Sollievo della Sofferenza,” Viale Cappuccini 71013, San Giovanni Rotondo, Foggia, Italy. E-mail: firstname.lastname@example.org.