Leaflet thrombosis following transcatheter aortic valve implantation

BACKGROUND

Transcatheter aortic valve implantation (TAVI) is increasingly being offered to high-risk patients with symptomatic aortic valve stenosis. Recent reports have suggested a high incidence of subclinical leaflet thrombosis following bioprosthestic aortic valve replacement. We report the frequency and clinical presentation of leaflet thrombosis identified by cardiac CT in patients referred for follow-up contrast enhanced CT angiography following TAVI.

METHODS

91 consecutive patients referred for follow-up contrast-enhanced CT angiography following TAVI were screened for inclusion in this analysis. Out of these, 13 patients were excluded. All CT examinations were performed using a 2nd or a 3rd generation dual-source system (Somatom Definition Flash/Force, Forchheim, Germany). In all patients, retrospectively ECG-gated spiral acquisition with tube modulation was performed to allow for assessment of leaflet motion. All prostheses were analyzed for presence of leaflet thrombosis defined as hypo-attenuated leaflet thickening with or without leaflet restriction. Post-procedural antithrombotic regimen as well as symptom status was documented in all patients.

RESULTS

78 consecutive patients (35 males, 81 ± 4 years) were analyzed. TAVI had been performed in all patients (76 transfemoral access, 2 transapical access) with either balloon-expandable prostheses (4 Sapien XT, 64 Sapien 3) or self-expandable prostheses (5 SJM Portico, 5 Symetis Acurate). Follow-up CT angiography was performed at a median of 4 months following index procedure (Interquartile range 1 month). Leaflet thrombosis was detected in 18 patients (23%, 14 Sapien 3, 1 Sapien XT, 2 SJM Portico, 1 Symetis Acurate). In patients with leaflet thickening on CT, only 11% were on either oral anticoagulation or new oral anticoagulants versus 50% for patients with no leaflet thickening (p 0.002). In patients with leaflet thrombosis, 3 leaflets were affected in 5 patients, 2 leaflets in 5 patients and in 8 patient only 1 leaflet was affected. Clinical symptoms (angina, dyspnea or both) were reported in 2/18 patients with leaflet thrombosis (11%) and in both patients a significant increase of the mean echocardiographic gradient over the prosthesis was documented. The peak and mean echocardiographic gradients obtained at the day of CT examination was significantly higher in symptomatic patients versus asymptomatic patients (peak 46 ± 7 vs. 23 ± 11 mmHg, mean 29 ± 7 vs. 12 ± 6 mmHg, p = 0.01 and 0.002, respectively). Follow-up CT was available for 4 patients with complete resolution of the hypo-attenuated leaflet thickening following treatment.

CONCLUSION

Leaflet thrombosis following TAVI is a relatively frequent finding in patients referred for contrast enhanced CT angiography following TAVI. In the majority of patients it follows a subclinical course and is substantially more frequent in individuals who are not on oral anticoagulation. However, in patients with relevant increase in prosthetic gradients, symptomatic presentations are possible.

Overlapping cross-sections significantly improve the reproducibility of coronary calcium measurements by electron beam tomography: a phantom study

PURPOSE

We conducted phantom studies to investigate whether overlapping cross-sections and volumetric scoring would significantly improve interscan reproducibility of electron beam tomography (EBT) for coronary artery calcium quantification.

METHOD

Fifteen phantoms simulating various amounts of coronary calcification were scanned in five different positions with a slice thickness of 3.0 mm and a table feed of 3.0, 2.5, and 2.0 mm. For the conventional "Agatston score" and a "volume score" (total volume of calcified lesions), interscan variabilities were compared between the three image acquisition protocols.

RESULTS

Agatston score variability was significantly lower for the 2.0 mm table feed than for the 3.0 or 2.5 mm table feed (3.0 mm: 22.9 +/- 10.3%; 2.5 mm: 13.6 +/- 8.2%; 2.0 mm: 8.9 +/- 5.5%). Volume score variability was significantly lower for 2.5 and 2.0 mm table feed than for 3.0 mm table feed (3.0 mm: 21.7 +/- 11.0%; 2.5 mm: 10.9 +/- 5.9%; 2.0 mm: 9.8 +/- 5.9%).

CONCLUSION

Overlapping cross-sections, especially in combination with volumetric scoring, significantly improved interscan reproducibility of EBT calcium quantification in a phantom study.

Variability of repeated coronary artery calcium measurements by electron beam tomography

In 120 patients, the mean interscan variability of coronary calcium quantification by electron beam tomography was 19.9% (median 7.8%) for the traditional calcium score, and 16.2% (median 5.7%) for volumetric scoring. Although this difference was not significant, there was a significant influence of the total amount of calcium, number of acquired images, and image noise on interscan reproducibility.

Contrast enhanced electron beam computed tomography to analyse the coronary arteries in patients after acute myocardial infarction

OBJECTIVE

To evaluate the accuracy of contrast enhanced electron beam computed tomography (EBCT) after acute myocardial infarction in determining patency of the infarct related artery and detecting high grade stenoses and occlusions in the coronary vessels.

DESIGN

Case study using blinded comparison with invasive coronary angiography.

PATIENTS

36 patients (mean age 53 years) 4-70 days after acute myocardial infarction.

INTERVENTIONS

The patients were studied by EBCT and invasive coronary angiography. For EBCT, 50 axial images of the heart (3 mm slice thickness) were acquired. They were triggered by the ECG during breath holding, after intravenous injection of contrast agent. The original images, surface reconstructions, and maximum intensity projections were evaluated for the presence of high grade stenoses and occlusions of the coronary arteries.

MAIN OUTCOME MEASURES

EBCT results were compared with invasive coronary angiography.

RESULTS

Of a total of 144 coronary arteries (left main, left anterior descending, left circumflex, and right coronary artery in 36 patients), 29 (20%) were unevaluable by EBCT. In the remaining arteries, 33 of 36 high grade lesions were correctly detected (92% sensitivity). Specificity was also 92% (73/79). Patency of the infarct related artery was correctly detected in 15 of 16 cases (94%). Five of the 14 occluded infarct related arteries (35%) were mistaken as stenotic but patent, and six could not be assessed.

CONCLUSIONS

EBCT is very accurate in detecting significant coronary artery lesions in patients after acute myocardial infarction, but differentiation between occluded and patent infarct related arteries is currently unreliable.

In-plane coronary arterial motion velocity: measurement with electron-beam CT

PURPOSE

To determine the speed of and changes in the speed of coronary arterial movement during the cardiac cycle with electron-beam computed tomography (CT).

MATERIALS AND METHODS

With electron-beam CT, 20 consecutive cross-sectional images were acquired at the mid right coronary artery (with 50-msec acquisition time, 8-msec intersection delay, 7-mm section thickness, and intravenous administration of 40 mL of contrast agent) in 25 patients. On the basis of the displacement of the left anterior descending, left circumflex, and right coronary arterial cross sections from image to image, movement velocity in the transverse imaging plane was calculated and was correlated with the simultaneously recorded electrocardiogram.

RESULTS

The velocity of in-plane coronary arterial motion varied considerably during the cardiac cycle. Peaks were caused by ventricular systole and diastole and by atrial contraction. The mean velocity was 46.6 mm/sec +/- 12. 5 (SD). The mean velocity of right coronary arterial movement (69.5 mm/sec +/- 22.5) was significantly faster than that of the left anterior descending (22.4 mm/sec +/- 4.1) or the left circumflex coronary artery (48.4 mm/sec +/- 15.0). The lowest mean velocity (27. 9 mm/sec) was at 48% of the cardiac cycle.

CONCLUSION

The lowest velocity of coronary arterial movement, which displays considerable temporal variation, was at 48% of the cardiac cycle.