FAQ for pre-TAVI (transcatheter aortic valve implantation) imaging

Any modern CT scanner capable of doing cardiac CT should be enough to do TAVI imaging. 128 slice scanners and above configurations are desirable
The scan is indicated in patients who are suffering from severe aortic stenosis and are at very high risk for open-heart surgery
Hence less invasive transaortic valve implantation through percutaneous vascular access is preferred
The scan is mostly done to assess the size of the aortic annulus and other important metrics of the aortic root so that a suitable implant can be sized before the procedure
All the routine preparation which are advised for a patient undergoing a cardiac CT are applicable for these patients
The actual requirement depends on the patient and the scanner being used
The rule of thumb is to match the injection flow rate and duration of injection to that of the combined time needed to cover the areas of interest
The heart and the ascending aorta should be scanned with retrospective ECG gating
A second run covering from clavicle till the greater trochanters of the femora can be planned to assess the subclavian and femoral access
Since most of the patients anyway end up getting a catheter angiogram before the actual TAVI procedure it is not mandatory to image the coronary arteries for assessment of coronary artery disease burden hence heart rate control is not essential.
But having said that if there is an indication to assess the coronary arteries especially in a case of post bypass graft patient, heart rate control can be achieved using any non-beta-blocker medication like Ivabradine.
So the actual heart rate control depends on whether you are planning to assess the coronary arteries in the study are not
All the measurements at the aortic root level are ideally done in a systolic phase
The first and foremost measurement which Radiologist must know how to process is to identify the annular plane and calculating the aortic annulus diameter using perimeter and area methods
Next comes the heights of the coronary Ostia from the annular plane
The length of the aortic valve leaflets
The minimum diameter of the femoral arteries or subclavian arteries based on the approach planned
The tortuosity of the iliac arteries
The radiologist role is to do his assessment so that any gross deviation from the findings given by the Radiologist and the device company will alert the Clinician to do a double-check before proceeding with the procedure
It is primarily the responsibility of the Radiologist to identify any other confounding pathology which can be seen in the scan which can alter the course of the management of the patient. For example, finding a tumor in the lungs or any abdominal viscera or identifying a Stanford type B dissection, etc
Compiled by: Dr Vijayabhasker Noori & Dr Vishnu Vardhan Ravilla
Consultant Radiology