Relation between ischaemic threshold measured during dobutamine stress echocardiography and coronary angiographic features

BACKGROUND: Stress echocardiography has become an accepted method for the evaluation of coronary artery disease (CAD). One potential advantage of dobutamine over other stressors used with echocardiography is the possibility of assessing the ischaemic threshold. AIM: This study explores the relation between the ischaemic threshold measured during dobutamine stress echocardiography (DSE) and coronary angiographic features. METHODS: Two hundred consecutive patients with positive high-dose (2.5-40 μg/kg/min) DSE test results were prospectively enrolled. Ischaemic threshold was recorded for all patients using the formula defined by the American Society of Echocardiography i.e. heart rate at which evidence of ischaemia first occurs divided by 220 minus the patient's age then multiplied by 100. All patients underwent coronary angiography, with recording of: (i) number of vessels (≥ 2.5 mm diameter) showing significant (≥ 70%) stenosis; (ii) maximum degree (percentage) of luminal stenosis; and (iii) worst atherosclerotic lesion type, among the affected coronary vessels. RESULTS: The mean age of the whole study cohort was 58.32 ± 10.5 years, 158 (79%) being male. 170 (85%) patients showed significant CAD, defined as ≥ 1 coronary vessel showing significant (≥ 70%) stenosis. Patients with single vessel disease showed a significantly higher ischaemic threshold (84.5 ± 0.3%) compared to two vessel (78 ± 2.2%) and multi-vessel disease (71.4 ± 2.8%) groups (p < 0.001). Patients with the worst lesions, i.e. type B, showed a significantly higher ischaemic threshold (81.6 ± 4.8%, p < 0.05), yet most of them (70%) showed single vessel disease. No statistically significant correlation was found between ischaemic threshold and degree of maximum luminal stenosis. Receiver operating characteristic curve analysis revealed that a recorded ischaemic threshold value of ≤ 75% predicted multi-vessel CAD with a sensitivity of 90%, a specificity of 97%, a positive predictive value of 87.5% and a negative predictive value of 97.8%. CONCLUSIONS: Ischaemic threshold measured during high-dose DSE test significantly correlates with the number of significantly stenosed coronary arteries. However, it does not correlate with the degree of vessel stenosis. These findings provide further support regarding the utility of DSE in the clinical evaluation of patients with CAD.