This was a single-center, retrospective analysis of patients with AF who had impaired LV function (LVEF <50%) and who underwent catheter ablation for the AF. We excluded patients receiving hemodialysis or who had structural heart disease and suspicion of other cardiomyopathies by echocardiography. After control of the AF, the patients were divided into two groups based on whether the LVEF was <60% (Group 1) or 60% (Group 2) more than 3 months after ablation. We compared the baseline characteristics between the two groups.
2.2 Echocardiographic data
Echocardiography was performed using various devices (Vivid E95, GE Healthcare Japan Corp.; APLIO Artida, APLIO I900, and APLIO 300, Canon Medical Systems Corp.; and iE, Philips Japan, Ltd.). LVEF and left atrial (LA) volume (LAV) were measured by the modified Simpson’s method and by the prolate-ellipsoid method, respectively. If the patient had a recurrence after ablation, echocardiography was performed >3 months after the arrhythmia resolved.
2.3 CT data
We performed CT before ablation. The LAV determined by CT (LAV-CT) was constructed by Ziostation2 Version 2.9.7.1 (Ziosoft, Inc). The LA appendage and pulmonary veins were removed from the LAV-CT by a manual procedure. Division of the LAV by the body surface area resulted in the LAV index of CT (LAVI-CT).
2.4 Ablation procedure
Patients received intravenous heparin with a target minimum activated clotting time of 300 seconds. AF ablation was performed using a cryoballoon (Arctic Front Advance; Medtronic, Inc) for pulmonary vein isolation (PVI) and a 3-dimentional electroanatomic mapping system (EnSite Precision; Abbott, Inc) in all patients. If the PVI was incomplete, complete PVI was performed with an irrigated radiofrequency (RF) catheter (FlexAbility; Abbott, Inc). Cavotricuspid isthmus line ablation was completed with the RF catheter.
2.5 Post-ablation follow-up
A 12-lead electrocardiogram (ECG) was performed at every visit; 24-hour Holter monitoring and echocardiography were performed according to the physician’s judgment. If patients had a cardiac implantable electronic device (CIED), AF was monitored. Biopsy and CMR were not performed.
2.6 Statistical analysis
Continuous data were described as median and interquartile range and categorical data as numbers and percentages. The Mann–Whitney U test and Fisher exact test were used to compare differences across groups. All tests were 2 sided, and a p value < 0.05 was considered to indicate statistical significance. A receiver operating characteristics (ROC) curve was calculated to identify the optimal cutoff point where sensitivity and specificity would be maximal for the prediction of improved LVEF. The area under the curve (AUC) and its 95% confidence interval were calculated as measures of the accuracy of the data. Statistical analysis was performed using IBM SPSS Advanced Statistics 24 (IBM, Inc). We could not perform multivariable analysis because of the small amount of data.
3 Results
3.1 characteristics of 2 groups at base line and factors for improving LVEF
A total of 32 patients (eight in Group1 and 24 in Group 2) were included in this study. One patient in Group 1 and seven patients in Group 2 had AF controlled by cardioversion and/or medications before ablation. In Group 1, one patient had a CIED before ablation and two patients had it after ablation. LAVI, LAV-CT and LAVI-CT were significantly smaller in Group 2 than in Group 1. Small LAV-CT and LVAI-CT were predictors for improving LVEF. All other characteristics were not significantly different between the groups (Table 1). The AUCs of the LAV-CT and LAVI-CT were 0.810 and 0.823, respectively (Figure 1), and the cutoff values were 147 ml and 79 ml/m2, respectively. The AUCs of the LA diameter (LAD) and LAV of echocardiography were 0.691 and 0.714, the cutoff values were 45.8 mm and 66.6 ml.
3.2 Characteristics of 2 groups after ablation
Post-ablation echocardiography data were not significantly different between the groups except for the LAD. Recurrence of arrhythmia was not significantly different between the groups (Table 2).
4 Discussion
4.1 Major finding
All patients with HF should have ablation for AF,4 but the risk of the procedure’s complications prevents this. We recognize some characteristics of TCM before ablation, and we are willing to recommend patients with possible TCM have ablation.
Small LV dimensions, younger age, and male sex may help to differentiate TCM from DCM.2,5,6 These parameters in this study were not significantly different between the two groups. LAV-CT was significantly different, whereas the difference in the LAV determined by echocardiography was close to significant (p = 0.0519). Patients with DCM have LV dilatation as well as LA dilatation.7 Echocardiography is noninvasive and easy. Small LV dimension, like LA dimension measured by echocardiography (LA diameter <45.8 mm and LAV <66.6 ml, which were the optimal cutoff values), may be helpful for the diagnosis of TCM.
4.2 Variety in Group 1
Patients in Group 1 were classified into two groups. In Group A, their LVEF improved a little. In group B, their LVEF remained the same or decreased. Group A was composed of the following patients: (1) those whose LVEF had been improving, (2) those with overlapping DCM and TCM,1 and (3) those with recurrence of AF. Group B was composed of just DCM or other cardiomyopathies. We should have followed Group 1 longer.
4.3 Limitations
This study has several limitations. It was a single-center study and included a small number of patients. LAV-CT was measured by hand and it might not be exact. Some tests, such as echocardiography, were performed according to individual judgment.
5 Conclusion
LAV-CT <147 mL was a predictor for improving LVEF significantly. Small LAV before ablation may be a predictor for TCM with AF and may be helpful for its diagnosis.
Acknowledgement
We express our thank to Y. Akatsu, medical technologists and members of Clinical research support center at Saiseikai Yokohamashi Tobu Hospital. We would like to thank Enago (www.enago.jp) for the English language review.
Conflict of interests
The authors declare that there are no conflicts of interests.
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