Aims: Although well supported by postmortem studies, the reliability of carotid atherosclerosis as surrogate marker of coronary atherosclerosis has been put in doubt by in vivo studies showing a poor correlation between carotid intima-media thickness (IMT) detected by external carotid ultrasound (ECU) and coronary stenosis assessed by quantitative coronary angiography (QCA). In the present study, we have investigated whether a stronger in vivo correlation between the two arteries can be obtained by using homogeneous variables such as carotid and coronary IMT, detected by ECU and intravascular ultrasound (IVUS), respectively.
Methods and results: ECU, QCA, and IVUS measurements were made in 48 patients. Carotid IMT was correlated with both angiographic and IVUS findings. A significant but weak correlation was observed between ECU and QCA variables (r approximately 0.35, P < 0.05); the correlation between ECU and IVUS measurements of IMT was higher, with correlation coefficients ranging from 0.49 to 0.55. In patients with a QCA diagnosis of normal/intermediate coronary atherosclerosis, the presence of a carotid-IMT(mean) > 1 mm was associated with an 18-fold increase in risk of having a positive IVUS test (OR = 17.99, 95% CI 1.83-177.14, P= 0.013) and with a seven-fold increased risk of having a significant IVUS coronary stenosis (OR = 7.4, 95% CI 1.27-44.0, P = 0.028).
Conclusion: Carotid atherosclerosis correlates better with coronary atherosclerosis when both circulations are investigated by the same technique (ultrasound) using the same parameter (IMT). This supports the concept that carotid IMT is a good surrogate marker of coronary atherosclerosis.