ABSTRACT
AIM: To assess improvement in arterial opacification by optimising the contrast medium dosing protocol for computed tomography (CT) prior to trans-catheter aortic valve implantation (TAVI). MATERIALS AND METHODS: A wide variation in arterial opacification was observed in the initial CT TAVI protocol (standard protocol). The practice was optimised by considering the time required for the examination and optimising contrast medium flux. This became the optimised protocol with a 30-second contrast medium bolus of iodine flux 15-19 mg iodine/kg body weight/second (mg/kg/s). Attenuation (mean HU) in (a) the ascending aorta (gated systolic acquisition) and (b) the ascending, descending thoracic (at carina), infra-renal abdominal aorta, and right common iliac artery (non-gated acquisition) was measured. Thirty-one sequential optimised examinations were compared to 31 prior standard protocol examinations. RESULTS: There was no difference between the standard and optimised groups regarding age, sex, weight, body mass index (BMI), or voltage. The mean bolus durations were 24.9±4.4 seconds for the standard and 30±0.3 seconds for the optimised protocols (p<0.001). Although there was no difference in the attenuation in the gated ascending aorta (p>0.99), there was improvement at all other anatomical points in the non-gated examinations of the optimised protocol (p<0.002). CONCLUSION: Optimising contrast medium flux and matching bolus duration to the CT technology dramatically improves the vascular access component of TAVI planning and provides a reliable method to achieve objectively enhanced arterial opacification. This work highlights how to obtain good arterial contrast medium opacification in haemodynamically fragile patients without excessive contrast medium volumes.
Subject(s)
Iodine , Transcatheter Aortic Valve Replacement , Aortic Valve , Catheters , Contrast Media , Humans , Tomography, X-Ray Computed/methods , Transcatheter Aortic Valve Replacement/methodsABSTRACT
AIM: To determine the diagnostic accuracy of an automated artificial intelligence derived right ventricle/left ventricle diameter ratio (RV/LV) computed tomography pulmonary angiography (CTPA) analysis tool to detect pulmonary hypertension (PH) in patients with suspected PH referred to a specialist centre. MATERIALS AND METHODS: The present study was a retrospective analysis of a prospectively maintained database of 202 consecutive patients with suspected PH, who underwent CTPA within 12 months of right heart catheterisation (RHC). Automated ventricular segmentation and RV/LV calculation (Imbio LLC, Minneapolis, MN, USA) was undertaken on the CTPA images. PH diagnosis was made using the RHC reference standard. RESULTS: The automated RV/LV correlated more strongly with RHC metrics than main pulmonary artery (MPA) diameter and MPA to ascending aorta diameter ratio (MPA/AA) measured manually (mean pulmonary arterial pressure [mPAP] r=0.535, R2 = 0.287 p<0.001; pulmonary vascular resistance [PVR] r=0.607, R2 = 0.369 p<0.001). In the derivation cohort (n=100), the area under the receiver-operating curve for automated RV/LV discriminating PH was 0.752 (95% confidence interval [CI] 0.677-0.827, p<0.001). Using an optimised Youden's Index of ≥1.12 classified from derivation, automated RV/LV ratio analysis was more sensitive for the detection of PH with higher positive predictive value (PPV) when compared with manual MPA and MPA/AA in the validation cohort (n=102). Automated RV/LV compromise (1.12) and specific (1.335) thresholds were strongly predictive of mortality (log-rank 7.401, p=0.007 and log-rank 16.075, p<0.001 respectively). CONCLUSION: In suspected PH, automated RV/LV diameter thresholds have high sensitivity for PH, outperform manual MPA and MPA/AA and can predict survival.
