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Cardiovascular surgeries have become progressively more sophisticated and complicated, due to factors such as the increasingly advanced age of patients, significant comorbidities, and increasing surgical complexity—minimally invasive procedures, reoperations and simultaneous procedures such as combined valve surgery and revascularisation, multiple valve replacements, combined valve and vascular surgery, as well as complicated aneurysm surgeries. Traditionally imaging studies with echocardiography and conventional angiography are increasingly complemented by tomographic techniques such as multidetector CT and MRI. In this context, echocardiography and angiography have significant shortcomings due to limited field of view focused on the examined cardiovascular structures, without significant insight into their spatial relationship vis-à-vis surrounding structures. The strength of CT and MRI is in the assessment of the spatial relationship of cardiovascular and extracardiac structures. In addition, the broadening of the scope of practice of both imaging and interventional cardiologists has made it more imperative to understand the various aspects of conventional and minimally invasive cardiovascular surgery. This article discusses the role of tomographic imaging in preprocedural planning and postoperative assessment of cardiac and vascular surgical patients.
Basics of tomographic imaging
MRI provides high resolution anatomic images without the use of ionising radiation and iodinated contrast agents. The commonly used pulse sequences utilised in cardiac MRI include: spin echo or ‘black blood’ images which provide good tissue contrast and anatomic detail, useful for visualising morphology; and gradient echo or ‘white blood’ images, including steady state free precession sequences which are commonly used for cine sequences. Gradient echo images are useful for the quantification of ventricular volume and function, as well as the visualisation of turbulent flow due to valvular disease or intracardiac shunts. Phase contrast velocity encoded imaging quantifies both the velocity and flow of blood through an area of interest. Accurate velocity and flow quantification allows the estimation of gradients across valves, regurgitant volumes, …