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High-spatial-resolution delayed enhancement MR imaging allows noninvasive identification of scar induced by radio frequency ablation following isolation therapy of the pulmonary vein, say researchers. In an initial experience study published in the June issue of Radiology, researchers from Beth Israel Deaconess Medical Center and Harvard Medical School found high-spatial-resolution delayed enhancement MR imaging allows noninvasive identification of scar induced by radio frequency ablation following isolation therapy of the pulmonary vein.

Dr. Dana C. Peters and colleagues evaluated a total of 23 subjects that included 16 men and seven women (mean age 54 years). Fifteen of them had the left atrium examined before ablation, and the other 18, at least 30 days after ablation.

A reader with four 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.

Dr. Peters's results stated that no subject demonstrated pre-ablation delayed enhancement of the atrial or pulmonary vein wall, whereas post-ablation delayed enhancement was identified in all 100 per cent. In patients after ablation, a partial to completely circumferential delayed enhancement pattern could be identified for the left inferior pulmonary vein that encompassed 88 per cent ± 11 of the circumference. Only 62 per cent of patients demonstrated more than 90 per cent circumferential delayed enhancement.

Researchers also noted that the signal-to-noise ratio of blood was 12, and the signal-to-noise ratios of the pre and post ablation left atrial wall were 15 and 22, respectively. A relationship between delayed enhancement wall thickness and the inverse of the time interval from ablation was also identified.

The study was supported by grants from the American Heart Association and the National Institutes of Health.