Motion artifacts in cardiac CT. The Novacor left ventricular assist device and its implications for clinical imaging.

PURPOSE: Cardiovascular applications of CT are primarily limited by temporal resolution of the scanner. Recent development in scanner technology has greatly increased temporal resolution. We here describe a standardized method of assessing temporal properties of various CT techniques. MATERIAL AND METHODS: The Novacor left ventricular assist device was mounted in a water-filled circulation phantom and scanned at different pump rates with a spiral CT unit and an electron beam unit. We also evaluated the use of ECG-triggered subsecond scanning on a spiral CT unit. RESULTS: Using the fastest conventional scanning protocol, severe motion artifacts occurred. These artifacts could not be reproduced from image to image, even if the pump rate was adjusted to scan rate (l/s). Electron beam tomography (EBT) reproducibly yielded few artifacts at 100 ms and practically no artifacts at 50 ms scanning time. Even without ECG-triggering, pump motion could be reproduced as a cine-cycle. With the ECG-triggered partial scanning CT technique, limited motion artifacts could be reproduced during diastole at a heart rate of 70-80 beats/min. CONCLUSION: The Novacor ventricular assist device may serve as a benchmark test in the evaluation of new scanning techniques for cardiovascular CT. While EBT presently remains the only CT technique to freeze cardiac motion throughout its cycle, ECG-triggered subsecond scans may, under certain conditions, capture cardiac anatomy in diastole.

Radiologic anatomy of ventricular assist devices.

Ventricular assist devices (VAD) allow for long-term circulatory support of patients with end-stage heart failure. With the increasing duration of circulatory support, diagnostic imaging plays an important role in the management of patients on a VAD. The aim of our review was to analyze the radiologic features of different VADs. From 1987 to 1996, 319 patients (mean age 42 years, range 3 to 74 years) were treated with a VAD. A Berlin Heart VAD was implanted in 263 of the patients, the univentricular Baxtor Novacor was implanted in three patients, and the univentricular CI Heartmate was implanted in 19 patients. All patients were studied by serial chest radiographs. In addition, 70 patients underwent computed tomography (CT), and five patients underwent electron beam CT. The Berlin Heart VAD was used as a biventricular support system in 218 patients. In all cases, the position of the wire-directed cannulae was identified on the chest radiographs, while the exact position of the cannula tip could be visualized by CT only. The plastic cannulae of both the Novacor and the Heartmate were not discernible on radiographs, but required CT for evaluation. Computed tomography also resolved the metal components of the pumps. The titanium-made pump housing of the Heartmate caused beam-hardening artefacts that might conceal fluid accumulations in the pump pocket. Computed tomography is the standard of reference for examinations of cannula position, pump position, and pump components of ventricular assist devices.

Successful mechanical circulatory support for more than two years with a left ventricular assist device in a patient with dilated cardiomyopathy.

A 36-year-old man with dilated cardiomyopathy was supported with a left ventricular assist device for 795 days. During this support time gradual functional recovery was noted. The patient tolerated the device well, enjoyed a good quality of life, and experienced no technical device-related problems. When a suitable donor heart became available, the device was switched off, and native ventricular function was assessed. This was judged to be acceptable, and the left ventricular assist device was successfully explanted. Postexplantation function remained acceptable and improved over the following days. The patient was discharged on the twentieth postoperative day and remains well.

[Presacral meningocele in thalidomide-induced embryopathy]. / Präsakrale Meningozele bei Thalidomid-Embryopathie.

A now 27-year-old man, known to have a thalidomide embryopathy with multiple malformations, including a sacral deformity, developed in the course of a few weeks a disorder of bladder emptying, colicky lower abdominal pain and, finally, abnormal stools. Exploratory laparotomy revealed an anterior sacral meningocele, confirmed by computed tomography with intrathecal contrast medium injection. After surgical removal of the meningocele all bladder and rectal disorders disappeared. The course of the disease and the radiological findings are typical of a space-occupying anterior sacral meningocele.