Detection of pulmonary vein and left atrial scar after catheter ablation with three-dimensional navigator-gated delayed enhancement MR imaging: initial experience

PURPOSE: To prospectively evaluate whether scar caused by radiofrequency (RF) ablation of the left atrium (LA) in patients with atrial fibrillation can be depicted with high-spatial-resolution delayed enhancement magnetic resonance (MR) imaging. MATERIALS AND METHODS: All 23 subjects (16 men, seven women; mean age, 54 years +/- 13 [standard deviation]) provided written informed consent; the study was approved by the local institutional review board and was HIPAA compliant. A high-spatial-resolution free-breathing delayed enhancement MR imaging method was developed to detect scar (ie, ablated tissue) in the LA and pulmonary veins (PVs). The LA in 15 patients before ablation and in 18 patients at least 30 days after ablation was examined. A reader with 4 years of experience assessed presence of delayed enhancement on images and circumferential completeness. Signal-to-noise and contrast-to-noise ratios were measured and compared with an unpaired t test. The relationship between measurements of enhancement thickness at the interatrial septum and the number of days after ablation was investigated. RESULTS: No subject demonstrated preablation delayed enhancement of the atrial or PV wall, whereas postablation delayed enhancement was identified in all (100%). In patients after ablation, a partial to completely circumferential delayed enhancement pattern could be identified for the left inferior PV that encompassed 88% +/- 11 of the circumference, but only 62% of patients demonstrated more than 90% circumferential delayed enhancement. The signal-to-noise ratio of blood was 12, and the signal-to-noise ratios of the pre- and postablation left atrial wall were 15 and 22, respectively (P<.05). A relationship between delayed enhancement wall thickness and the inverse of the time interval from ablation was identified (P<.05). CONCLUSION: High-spatial-resolution delayed enhancement MR imaging allows noninvasive identification of scar induced by RF ablation following isolation therapy of the PV.     

Comparison of Mechanical Embolectomy and Intraarterial Thrombolysis in Acute Ischemic Stroke within the MCA: MERCI and Multi MERCI compared to PROACT II

Introduction  Intraarterial thrombolysis and mechanical embolectomy have been studied for endovascular treatment of stroke. The MERCI and Multi MERCI trials of mechanical embolectomy with or without adjuvant intraarterial thrombolysis demonstrated effective recanalization, but with a higher mortality compared with control patients in the PROACT II trial of intraarterial thrombolysis. Differences in trial design may account for this mortality difference. Methods  We identified patients in the MERCI and Multi MERCI trials who would have been eligible for PROACT II. Rates of good outcome (mRS ≤2) and mortality at 90 days were compared, adjusting for differences in baseline NIHSS score and age. Results  Sixty-eight patients enrolled in MERCI and 81 enrolled in Multi MERCI were eligible for PROACT II. In both unadjusted and adjusted analyses, PROACT II-eligible embolectomy patients showed a trend toward better clinical outcomes compared to the PROACT II control arm (adjusted, MERCI 35.4% [p = ns], Multi MERCI 42.8% [p = 0.048], PROACT II control, 25.4%). In both unadjusted and adjusted analyses, mortality rates did not significantly differ between embolectomy patients and PROACT II control patients (adjusted analysis, MERCI 29.1%, Multi MERCI 18.0%, PROACT II control, 27.1%). Compared with the PROACT II treatment group, embolectomy groups showed similar rates of good outcome and mortality. Conclusions  Differences in mortality and proportion of good outcome between the MERCI/Multi MERCI trials and the PROACT II trial are explained by differences in study design and baseline characteristics of patients. Mechanical embolectomy and IA thrombolysis may each be reasonable strategies for acute stroke; a randomized trial is necessary to confirm these results.     

Accuracy of electrocardiographic criteria for atrial enlargement: validation with cardiovascular magnetic resonance

Purpose

In mitral valve prolapse, determining whether the valve is suitable for surgical repair depends on the location and mechanism of regurgitation. We assessed whether cardiovascular magnetic resonance (CMR) could accurately identify prolapsing or flail mitral valve leaflets and regurgitant jet direction in patients with known moderate or severe mitral regurgitation.

Methods

CMR of the mitral valve was compared with trans-thoracic echocardiography (TTE) in 27 patients with chronic moderate to severe mitral regurgitation due to mitral valve prolapse. Contiguous long-axis high temporal resolution CMR cines perpendicular to the valve commissures were obtained across the mitral valve from the medial to lateral annulus. This technique allowed systematic valve inspection and mapping of leaflet prolapse using a 6 segment model. CMR mapping was compared with trans-oesophageal echocardiography (TOE) or surgical inspection in 10 patients.

Results

CMR and TTE agreed on the presence/absence of leaflet abnormality in 53 of 54 (98%) leaflets. Prolapse or flail was seen in 36 of 54 mitral valve leaflets examined on TTE. CMR and TTE agreed on the discrimination of prolapse from flail in 33 of 36 (92%) leaflets and on the predominant regurgitant jet direction in 26 of the 27 (96%) patients. In the 10 patients with TOE or surgical operative findings available, CMR correctly classified presence/absence of segmental abnormality in 49 of 60 (82%) leaflet segments.

Conclusion

Systematic mitral valve assessment using a simple protocol is feasible and could easily be incorporated into CMR studies in patients with mitral regurgitation due to mitral valve prolapse.