Thrombus detection in the left atrial appendage using contrast-enhanced MRI: a pilot study.

OBJECTIVE: Left atrial thrombi are an important cause for embolism-related morbidity and mortality. Transesophageal echocardiography (TEE), the clinical reference, is semiinvasive; thus, we aimed to assess the value of contrast-enhanced cardiovascular MRI for the detection of thrombus in the left atrial appendage. CONCLUSION: The image quality was good for both 2D perfusion (grade 4 +/- 1) and 3D turbo fast low-angle shot (FLASH) (grade 4 +/- 1, n.s.). Compared with TEE, 2D perfusion, 3D turboFLASH, and the combination of both techniques yielded sensitivities of 47/35/44%, specificities of 50/67/67%, positive predictive values of 73/75/80%, and negative predictive values of 25/27/29%, respectively. The size of the thrombus was overestimated by 2D perfusion (66%) and by 3D turboFLASH (25%) and agreement for location and shape of thrombus was 50% and 75% for 2D perfusion and 75% and 50% for 3D turboFLASH, respectively. The TEE thrombus size was significantly larger in patients with true-positive diagnoses by 2D perfusion (148%) and by 3D turboFLASH (151%) when compared with patients with false-negative diagnoses (p < 0.05 for both). No such difference was found for image quality, time delay between TEE and MRI examination, and location and shape of thrombi. Contrast-enhanced MRI lacks diagnostic accuracy for the detection of thrombi in the left atrial appendage. Future technical improvements are essential to establish this technique as a noninvasive alternative to TEE.

Diagnosis of patent foramen ovale using contrast-enhanced dynamic MRI: a pilot study.

OBJECTIVE: The aim of this study was to evaluate the feasibility of dynamic contrast-enhanced MRI for detection of patent foramen ovale. SUBJECTS AND METHODS: Fifteen patients with and five patients without patent foramen ovale underwent transesophageal echocardiography and MRI, which were performed during the Valsalva maneuver. Grading results (grade 0, no patent foramen ovale and grades 1-3, minor to major enhancement due to intracardiac shunt) were assessed visually. Signal-intensity curves in the left atrium and in a pulmonary vein served to underline the diagnosis. RESULTS: The diagnoses of all patients with (15/15) and without patent foramen ovale (5/5) were correct compared with the findings of the reference transesophageal echocardiography. In 12 (60%) of 20 patients, the grading scores were identical, and in four (20%) of 20 patients, the scores differed by more than one grade. Overall, there was a good correlation of grading scores (r = 0.7, p < 0.05). Using signal-intensity curves, we found that the patients with patent foramen ovale showed an additional signal peak in the left atrium before the enhancement of the pulmonary vein because of an intracardiac shunt. In three of 15 patients with patent foramen ovale, an atrial septal aneurysm was correctly diagnosed. CONCLUSION: This pilot study shows that MRI is a new noninvasive method to detect patent foramen ovale and atrial septal aneurysm. A grading is possible but warrants further investigation regarding its predictive value and impact on treatment strategies.