Frequency, Predictors, and Clinical Impact of Valvular and Perivalvular Thrombus After Transcatheter Aortic Valve Replacement.

BACKGROUND: Subclinical aortic valve complex (valvular and perivalvular) thrombus is not rare after transcatheter aortic valve replacement (TAVR). The risk factors and clinical implications of these findings remain uncertain. OBJECTIVES: This study sought to evaluate the frequency, predictors, and clinical outcome of aortic valve complex thrombus after TAVR. METHODS: In the ADAPT-TAVR (Anticoagulation Versus Dual Antiplatelet Therapy for Prevention of Leaflet Thrombosis and Cerebral Embolization After Transcatheter Aortic Valve Replacement) trial comparing edoxaban vs dual antiplatelet therapy in TAVR patients without an indication for chronic anticoagulation, the frequency of valvular (subclinical leaflet thrombus) and perivalvular (supravalvular, subvalvular, and sinus of Valsalva) thrombus was evaluated by 4-dimensional computed tomography at 6 months. The association of these phenomena with new cerebral thromboembolism on brain magnetic resonance imaging, neurologic and neurocognitive dysfunction, and clinical outcomes was assessed. RESULTS: Among 211 patients with 6-month computed tomography evaluations, 91 patients (43.1%) had thrombus at any aortic valve complex, 30 (14.2%) patients had leaflet thrombus, and 78 (37.0%) patients had perivalvular thrombus. A small maximum diameter of the stent at the valve level and low body surface area were independent predictors of aortic valve complex and perivalvular thrombus, and decreased renal function was an independent predictor of leaflet thrombus. No significant differences were observed in new cerebral lesions, neurologic or neurocognitive functions, or clinical outcomes among patients with or without valvular or perivalvular thrombus. CONCLUSIONS: Subclinical aortic valve complex (valvular and perivalvular) thrombus was common in patients who had undergone successful TAVR. However, these imaging phenomena were not associated with new cerebral thromboembolism, neurologic or neurocognitive dysfunction, or adverse clinical outcomes. (Anticoagulation Versus Dual Antiplatelet Therapy for Prevention of Leaflet Thrombosis and Cerebral Embolization After Transcatheter Aortic Valve Replacement [ADAPT-TAVR]; NCT03284827).

Longer Length of Delayed-Contrast Filling of Clot on 4-Dimensional Computed Tomographic Angiography Predicts Cardiogenic Embolism.

Background and Purpose- We hypothesized the length of delayed-contrast filling sign (DCFS) of intraarterial clot, indicating contrast medium penetration into the thrombus, was associated with stroke etiology. Methods- We retrospectively included patients with large vessel occlusion in anterior circulation who underwent computed tomographic perfusion within 24 hours poststroke onset. We defined DCFS as contrast medium diffusion through the thrombi after the arterial peak phase on 4-dimensional computed tomographic angiography derived from computed tomographic perfusion. We measured the length of DCFS and investigated its value for predicting the stroke etiology. Results- Three hundred twenty-one patients were analyzed, and their stroke etiologies included cardiogenic embolism (CE, n=167), large artery atherosclerosis (n=64), other etiology group (n=4), and undetermined etiology (n=86). CE patients had longer length of DCFS than non-CE patients (2.3 versus 0.5 mm; P<0.001). The optimal cutoff value of DCFS length for predicting CE was 1.5 mm. The sensitivity, specificity, positive predictive value, and negative predictive value of a length of DCFS >1.5 mm for predicting CE were 83.2%, 70.8%, 75.5%, and 79.6%. Conclusions- Longer length of DCFS was associated with CE in patients with large vessel occlusion in anterior circulation, which may provide stroke etiology information.

Investigating the potential impact of four-dimensional computed tomography (4DCT) on toxicity, outcomes and dose escalation for radical lung cancer radiotherapy.

AIMS: To investigate the potential dosimetric and clinical benefits predicted by using four-dimensional computed tomography (4DCT) compared with 3DCT in the planning of radical radiotherapy for non-small cell lung cancer. MATERIALS AND METHODS: Twenty patients were planned using free breathing 4DCT then retrospectively delineated on three-dimensional helical scan sets (3DCT). Beam arrangement and total dose (55 Gy in 20 fractions) were matched for 3D and 4D plans. Plans were compared for differences in planning target volume (PTV) geometrics and normal tissue complication probability (NTCP) for organs at risk using dose volume histograms. Tumour control probability and NTCP were modelled using the Lyman-Kutcher-Burman (LKB) model. This was compared with a predictive clinical algorithm (Maastro), which is based on patient characteristics, including: age, performance status, smoking history, lung function, tumour staging and concomitant chemotherapy, to predict survival and toxicity outcomes. Potential therapeutic gains were investigated by applying isotoxic dose escalation to both plans using constraints for mean lung dose (18 Gy), oesophageal maximum (70 Gy) and spinal cord maximum (48 Gy). RESULTS: 4DCT based plans had lower PTV volumes, a lower dose to organs at risk and lower predicted NTCP rates on LKB modelling (P < 0.006). The clinical algorithm showed no difference for predicted 2-year survival and dyspnoea rates between the groups, but did predict for lower oesophageal toxicity with 4DCT plans (P = 0.001). There was no correlation between LKB modelling and the clinical algorithm for lung toxicity or survival. Dose escalation was possible in 15/20 cases, with a mean increase in dose by a factor of 1.19 (10.45 Gy) using 4DCT compared with 3DCT plans. CONCLUSIONS: 4DCT can theoretically improve therapeutic ratio and dose escalation based on dosimetric parameters and mathematical modelling. However, when individual characteristics are incorporated, this gain may be less evident in terms of survival and dyspnoea rates. 4DCT allows potential for isotoxic dose escalation, which may lead to improved local control and better overall survival.

Determination of internal target volume from a single positron emission tomography/computed tomography scan in lung cancer.

PURPOSE: The use of four-dimensional computed tomography (4D-CT) to determine the tumor internal target volume (ITV) is usually characterized by high patient radiation exposure. The objective of this study was to propose and evaluate an approach that relies on a single static positron emission tomography (PET)/CT scan to determine the ITV, thereby eliminating the need for 4D-CT and thus reduce patient radiation dose. METHODS AND MATERIALS: The proposed approach is based on the concept that the observed PET image is the result of a joint convolution of an ideal PET image (free from motion and partial volume effect) with a motion-blurring kernel (MBK) and partial volume effect. In this regard, the MBK and tumor ITV are then estimated from the deconvolution of this joint model. To test this technique, phantom and patient studies were performed using different sphere/tumor sizes and motion trajectories. In all studies, a 4D-CT and a PET/CT image of the sphere/tumor were acquired. The ITV from the proposed technique was then compared to the maximum intensity projection (MIP) volume of the 4D-CT images. A Dice coefficient of the two volumes was calculated to represent the similarity between the two ITVs. RESULTS: The average ITVs of the proposed technique were 97.2% ± 0.3% and 81.0% ± 16.7% similar to the MIP volume in the phantom and patient studies, respectively. The average dice coefficients were 0.87 ± 0.05 and 0.73 ± 0.16, respectively, for the two studies. CONCLUSION: Using the proposed approach, a single static PET/CT scan has the potential to replace a 4D-CT to determine the tumor ITV. This approach has the added advantage of reducing patient radiation exposure and determining the tumor MBK compared to 4D-CT/MIP-CT.