Clinical value of multidetector CT coronary angiography as a preoperative screening test before non-coronary cardiac surgery

Objective

Myocardial scintigraphy and/or conventional angiography (CA) are often performed before cardiac surgery in an attempt to identify unsuspected coronary artery disease which might result in significant cardiac morbidity and mortality. Multidetector CT coronary angiography (MDCTCA) has a recognised high negative predictive value and may provide a non‐invasive alternative in this subset of patients. The aim of this study was to evaluate the clinical value of MDCTCA as a preoperative screening test in candidates for non‐coronary cardiac surgery.

Methods

132 patients underwent MDCTCA (Somatom Sensation 16 Cardiac, Siemens) in the assessment of the cardiac risk profile before surgery. Coronary arteries were screened for ?50% stenosis. Patients without significant stenosis (Group 1) underwent surgery without any adjunctive screening tests while all patients with coronary lesions ?50% at MDCTCA (Group 2) underwent CA.

Results

16 patients (12.1%) were excluded due to poor image quality. 72 patients without significant coronary stenosis at MDCTCA were submitted to surgery. 30 out of 36 patients with significant (?50%) coronary stenosis at MDCTCA and CA underwent adjunctive bypass surgery or coronary angioplasty. In 8 patients, MDCTCA overestimated the severity of the coronary lesions (>50% MDCTCA, <50% CA).No severe cardiovascular perioperative events such as myocardial ischaemia, myocardial infarction or cardiac failure occurred in any patient in Group 1.

Conclusions

MDCTCA seems to be effective as a preoperative screening test prior to non‐coronary cardiac surgery. In this era of cost containment and optimal care of patients, MDCTCA is able to provide coronary vessel and ventricular function evaluation and may become the method of choice for the assessment of a cardiovascular risk profile prior to major surgery.Since its introduction in the 1960s,¹ conventional coronary angiography (CA) has been considered the gold standard for the diagnosis of coronary artery disease because of its high contrast, temporal and spatial resolution.^2,3,4 In the past few years, we have witnessed a considerable increase in diagnostic and interventional procedures. Despite the high degree of accuracy (73–89%) of non‐invasive diagnostic tests such as exercise ECG, myocardial scintigraphy and stress‐echocardiography in detecting myocardial ischaemia,⁵ about 20% of patients undergoing CA due to a positive result of these non‐invasive tests, had no evidence of coronary lesions.^6,7Multidetector CT (MDCT), introduced into clinical practice in 2000, has demonstrated excellent technical characteristics for coronary artery evaluation. Results in the literature show a high degree of diagnostic accuracy in detecting significant coronary lesions and, particularly, an excellent capability of excluding them, due to negative predictive values ranging from 96 to 99%.^{8,9,10,11,12,13,14,15,16,17,18}Patients who are candidates for major non‐coronary cardiac or vascular surgery, such as heart valve replacement, aortic aneurysm and aortic dissection, require a complete assessment of potentially dangerous co‐morbidities. There is a 5 to 10% perioperative cardiac morbidity rate during vascular surgery, even in patients at low risk for coronary disease.¹⁹ According to Paul et al.²⁰ there is a 17% risk of severe multivessel disease in low clinical risk asymptomatic patients undergoing vascular surgery. American College of Cardiology/American Heart Association (ACC/AHA) guidelines for preoperative evaluation before major surgery recommend stratification of ischaemic heart disease with clinical and non‐invasive tests.^19,20,21,22 The diagnostic accuracy is 68 to 77% for exercise ECG and 73 to 85% for stress‐echocardiography. Myocardial scintigraphy provides an accuracy of 87–89% in patients with normal resting ECG, with a radiation exposure ranging from 4.6 to 20?mSv,²³ almost equivalent to MDCT coronary angiography (MDCTCA). However, for certain high‐risk patients, ACC guidelines suggest proceeding directly with coronary angiography rather than performing a non‐invasive test. Therefore, in clinical practice, CA is often performed before major vascular or cardiac surgery. Considering that millions of surgical procedures are probably performed every year worldwide (eg, 95?000 heart valve replacements/year in the USA),^6,7 several hundred thousand negative CAs are still performed.After some years of validation studies comparing MDCTCA with CA, studies on clinical utility are now warranted to demonstrate whether and how this technique can change and improve the current management of patients. The purpose of this study is to evaluate the clinical impact of MDCTCA as a preoperative screening test for cardiac risk assessment in patients who are candidates for major non‐coronary cardiac surgery and who are asymptomatic for ischaemic heart disease.