Accuracy of Intravascular Ultrasound Evaluation for the Assessment of Native Valve Measures in Patients Undergoing TAVI: Preliminary Results.

INTRODUCTION

Transcatheter aortic valve implantation (TAVI) technique represents a real revolution in the field of interventional cardiology and medicine, in particular for the treatment of severe aortic valve stenosis in elderly patients or in patients when the periprocedural risk for the traditional surgical option is considered too high, as an alternative to the traditional aortic valve replacement. Although experience on the valves of the last generation is still limited in terms of time, the data currently available are definitely moving in the direction of a minimum hospital mortality (1%) as well as a drastic reduction in the incidence of complications when compared to the devices of the previous generation. Finally, the evolution of specified materials of the newest generation have greatly enhanced safety and efficacy of TAVI procedures in the last years. In order to ensure the selection of the most appropriate valve and the success of the procedure, the role of cardiac imaging (computed tomography scan evaluation and angiography) is crucial. These examinations require the use of contrast medium in patients suffering from renal dysfunction at the baseline. The need for fluoroscopy and angiography using contrast agents to aid positioning of the valve may lead to contrast-induced nephropathy (CIN) as one form or one etiology of acute kidney injury (AKI), which is associated with increased morbidity and mortality. The aim of our study is to investigate the accuracy of intravascular ultrasound (IVUS-a technique which does not need contrast) for the assessment of native valve measures in patients undergoing TAVI by comparing values obtained with IVUS to those ones previously obtained in the same patients with computed tomography (CT) scans.

MATERIAL AND METHODS

We enrolled 25 consecutive patients (10 males, average age 81.3±5,1 years) who underwent TAVI with femoral access in our Cardiac Surgery Cath-Lab (University of Bari) from January to October 2015 (Logistic EuroSCORE 21.6±15.4%; STS score mortality 20.9±14.9%). Each patient scheduled for TAVI underwent coronary angiography and high resolution angio-CT in order to obtain a complete evaluation (diameters, perimeters, and areas at annulus level, -3mm level, +15mm level, height of coronary ostia, shape, and conformation of left ventricle outflow tract, conformation, and calcifications of aortic and ileo-femoral axis) to choose the most suitable prosthetic aortic valve for each patient. In all patients, during the procedure (before the prosthetic valve implantation), we executed a manual IVUS pullback (from left ventricle outflow tract to ascending aorta) by using a 7F IVUS probe (Volcano Corporation, San Diego, CA). On the recorded IVUS pullback, a second operator (who did not know the values obtained by CT measurements) identified the aortic annulus and, at this level, measured: minimum and maximum diameter; perimeter; derived perimeter, and area. The t-student test has been used to compare the averages of these IVUS values to the CT ones. A p value< 0.05 was considered as statistically significant.

RESULTS

Independently from the kind and size of implanted prosthetic valve, no statistical differences were found when the averages of all considered parameters (obtained both with CT and IVUS) were compared. The following are the results obtained: minimum diameter (CT: 19,62mm±1,10 vs. IVUS: 19,55mm±1,40; p=0.41); maximum diameter (CT: 24,73mm±2,42 vs. IVUS: 25,9mm±1,80; p=0.08); perimeter (CT: 72,05mm±4,36 vs. IVUS: 73,32mm±6,09; p=0.164); derived perimeter (CT: 22,94mm±1,40 vs. IVUS: 23,32mm ± 1,95; p=0,198); and area (CT: 3,99cm2 ±0,97 vs. IVUS: 4,06 cm2 ± 0,47; p=0,073) (Figs. 1-3).

CONCLUSIONS

These preliminary data suggest accurate IVUS measures when compared to CT in the evaluation of valve parameters considered (minimum and maximum diameters, area, perimeter, and derived perimeter at the annulus level). In order to confirm these findings and to give them statistical significance, it will be necessary to increase the sample size.