Correction to: Systolic modified Look-Locker inversion recovery myocardial T1 mapping improves the accuracy of T1 and extracellular volume fraction measurements of patients with high heart rate or atrial fibrillation.

The article "Systolic modified Look-Locker inversion recovery myocardial T1 mapping improves.

Systolic modified Look-Locker inversion recovery myocardial T1 mapping improves the accuracy of T1 and extracellular volume fraction measurements of patients with high heart rate or atrial fibrillation.

Image data for T1 mapping are generally acquired during mid-diastole period. However, T1 mapping tends to fail for patients with high heart rate or atrial fibrillation because of short or irregular R-R interval. Focusing on the evidence that the timing of systole is more stable than that of diastole from the R wave, we compared systolic T1 mapping with conventional diastolic T1 mapping for all participants (n = 58) by visual scoring of T1 calculation error. The systolic scores were significantly better than the diastolic scores (p < 0.05). This advantage of the systolic scores was confirmed selectively for patients with atrial fibrillation (p < 0.05, n = 19). The successful number of nonrigid image registration alignment for extracellular volume fraction (ECV) analysis also increased significantly for systolic images compared with diastolic images (p < 0.05). Thus, systolic T1 mapping improves the accuracy of T1 values and ECV analysis.

Evaluation of Simultaneous Dual-radioisotope SPECT Imaging Using (18)F-fluorodeoxyglucose and (99m)Tc-tetrofosmin.

OBJECTIVES: Use of a positron emission tomography (PET)/single-photon emission computed tomography (SPECT) system facilitates the simultaneous acquisition of images with fluorine-18 fluorodeoxyglucose ((18)F-FDG) and technetium ((99m)Tc)-tetrofosmin. However, (18)F has a short half-life, and 511 keV Compton-scattered photons are detected in the (99m)Tc energy window. Therefore, in this study, we aimed to investigate the consequences of these facts. METHODS: The crosstalk correction for images in the (99m)Tc energy window involved the dual energy window (DEW) subtraction method. In phantom studies, changes in the count of uniform parts in a phantom (due to attenuation from decay), signal detectability in the hot-rod part of the phantom, and the defect contrast ratio in a cardiac phantom were examined. RESULTS: For (18)F-FDG in the step-and-shoot mode, nearly a 9% difference was observed in the count of projection data between the start and end positions of acquisition in the uniform part of the phantom. Based on the findings, the detectability of 12 mm hot rods was relatively poor. In the continuous acquisition mode, the count difference was corrected, and detectability of the hot rods was improved. The crosstalk from (18)F to the (99m)Tc energy window was approximately 13%. In the cardiac phantom, the defect contrast in (99m)Tc images from simultaneous dual-radionuclide acquisition was improved by approximately 9% after DEW correction; the contrast after correction was similar to acquisition with (99m)Tc alone. CONCLUSION: Based on the findings, the continuous mode is useful for (18)F-FDG acquisition, and DEW crosstalk correction is necessary for (99m)Tc-tetrofosmin imaging.

The change in the tissue characterization detected by magnetic resonance imaging after radiofrequency ablation of isthmus-dependent atrial flutter.

BACKGROUND: Radiofrequency (RF) ablation produces thermal necrosis and electrophysiological conduction block when lesions are transmural. However, the phenomenon of endocardial edema may prevent the ablative energy from reaching the deeper layers of the myocardium. METHODS: Sixty-seven patients underwent RF ablation of the cavotricuspid isthmus (CTI) for isthmus-dependent atrial flutter (AFL; 54 males, 61±9 years). Cardiac magnetic resonance (CMR) imaging was performed 1 day before ablation, and the length and morphology of the CTI were determined. In addition, 1 day and 1 month after ablation, the change in the wall thickness, prevalence of a high signal in the delayed enhancement (DE) and T2-weighted images at the CTI were evaluated. RESULTS: Before ablation, DE regions at the CTI were found in 2 patients with a concave type and 1 with a pouch type. No region with a high T2 signal at the CTI was observed in any of the 67 patients. One day after ablation, high T2 signals were detected at the CTI, and the wall thickness was significantly augmented (p<0.0001). CMR also revealed a DE at the CTI in 46 patients (69%). One month after ablation, the thickened wall with a high T2 signal recovered to baseline, and a DE at the CTI was found in 56 patients (84%). CONCLUSIONS: CMR is useful for assessing the creation of endocardial edema and scar tissue resulting from CTI ablation. These results may correlate with the anatomical isthmus block after ablation in a large portion of the patients with isthmus-dependent AFL.

Thickening of the left atrial wall shortly after radiofrequency ablation predicts early recurrence of atrial fibrillation.

BACKGROUND: Inflammatory responses following atrial fibrillation (AF) ablation may aggravate arrhythmogenic activity and cause an early recurrence of AF (ERAF). METHODS AND RESULTS: In 56 patients who underwent circumferential pulmonary vein ablation (CPVA) for paroxysmal AF, cardiovascular magnetic resonance imaging (CMRI) was evaluated in 5 subdivided left atrial (LA) regions before the CPVA and at 1 day and 1 month after. At a mean of 7+/-10 days after the CPVA, 23 patients (41%) developed 1 or more episodes of AF (ERAF group), while 33 patients (59%) remained free from AF during the first month of follow up (no-ERAF group). LA wall thickness increased 1 day after the CPVA in both groups, as demonstrated by high T2-weighted signal. The LA roof thickness and its increase, however, were greater in the ERAF group than in the no-ERAF group (P<0.05). Regions of delayed enhancement (DE) were also frequently detected in both groups, but the total number of DE regions did not differ between the 2 groups. The thickening of the LA wall associated with a high T2-weighted signal resolved within 1 month. No significant difference between the 2 groups was found in any of the CMRI parameters before or 1 month after CPVA. CONCLUSIONS: Thickening of the LA roof shortly after CPVA may predict an ERAF.

The characteristics and distribution of the scar tissue predict ventricular tachycardia in patients with advanced heart failure.

BACKGROUND: Contrast-enhanced magnetic resonance imaging (CMR) identifies scar tissue as hyperenhanced areas. We sought to clarify the relationship between the scar characteristics and occurrence of sustained ventricular tachycardia (VT) in patients with advanced heart failure. METHODS: CMR was performed in 29 patients with dilated cardiomyopathy (DCM group) and 18 patients with ischemic cardiomyopathy (ICM group). The characteristics, volume, and distribution of the hyperenhanced areas were analyzed by CMR. The CMR parameters and clinical arrhythmic events were compared between the two groups. RESULTS: In the DCM group, almost all hyperenhanced areas were nontransmural, and presented frequently in the midwall layer. The volume of the hyperenhanced areas and total number of hyperenhanced segments were greater in patients with sustained VT than in those without. On the other hand, in the ICM group, transmural or subendocardial hyperenhanced areas were detected in the territory of the coronary arteries. The volume of the hyperenhanced areas and total number of transmural hyperenhanced segments in patients with sustained VT were unexpectedly smaller than in those without. However, the percentage of nontransmural hyperenhanced segments was greater in patients with sustained VT than in those without. CONCLUSIONS: The presence and magnitude of the nontransmural scar tissue may predict sustained VT in patients with advanced heart failure. There was the possibility that a recruitment bias was responsible for the finding of the smaller scars in the ICM patients with sustained VT.