Coronary CT: drug-induced stress examination technique for studying coronary arteries

Abstract

Coronary CT is a low-invasive diagnostic examination that uses contrast medium to explore the coronary arteries, the cardiac cavity and assess the condition of the vessel walls.
It is an examination with greater accuracy than other diagnostic and clinical investigations; in fact, it allows the detailed acquisition of ultra-thin anatomical sections of the coronary vessels and their reconstruction in every plane of space.
Intravenous injection of the contrast medium bolus and cardio-synchronisation enable non-invasive angiography of the coronary arteries, with high anatomical detail and excellent diagnostic accuracy very close to invasive coronarography.
However, this method is not to be considered as an alternative to coronarography, but rather as a complementary diagnostic aid; in fact, the invasive technique remains the approach of choice in patients with acute coronary syndromes. Coronary CT is prescribed in cases of: suspected coronary artery obstruction or stenosis, high risk of atherosclerosis and coronary artery disease, heart failure, dilated cardiomyopathy, patients undergoing cardiac and vascular surgery, such as aortic aneurysms, patients who are candidates for minimally invasive percutaneous aortic valve replacement (TAVI).
The examination can be performed during a resting phase or during a phase in which the patient is under drug-induced stress; in particular, coronaro-CT under stress represents a further step forward for this method.
The examination can be performed during a resting phase or during a phase in which the patient is under drug-induced stress; in particular, coronaro-CT under stress represents a further step forward for this method.
The execution of the examination protocol under pharmacological stress leads to greater diagnostic accuracy, since by combining the information provided by anatomy and perfusion it allows both morphology and cardiac function to be assessed.
Prior to the acquisition, an intravenous infusion of a vasodilator such as adenosine is performed, so as to induce pharmacological stress conditions in the patient that are suitable for demonstrating the presence of perfusion deficits, i.e. inducible ischaemia; consequently, the administration of this drug results in a significant optimisation of the quality of the diagnostic procedure.
The assessment of myocardial perfusion is based on the distribution of iodinated contrast during its passage through the myocardium; since the distribution of contrast medium is determined by the arterial blood supply, myocardial perfusion defects can be identified as hypo-attenuated areas containing reduced amounts of contrast.
A perfusion defect under pharmacological stress that reverses at rest is, by definition, a stress-induced ischaemia, in contrast, an irreversible defect is characteristic of myocardial infarction.