Usefulness of Morphology-Voltage-P-wave duration (MVP) score as a predictor of atrial fibrillation recurrence after pulmonary vein isolation

2.1 Patient population

Utilizing data from General Hospital of Ningxia medical University, the participants were consecutive refractory symptomatic PAF patients. These patients who were retrospectively enrolled presented to our institution for PVI from January 2010 to December 2018. PAF was defined according to current guidelines. (JCS Joint Working Group 2014) Paroxysmal AF was defined as self-terminating within 7 days after onset documented by previous routine electrocardiograms (ECG) or Holter ECG. Exclusion criteria included the following basis: (a) had a history of previous catheter ablation, cardiac surgery, serious valvular heart disease, or cardiac pacemakers; (b) with low-quality ECG, or without a recorded sinus ECG or echocardiogram before the procedure; (c) were not followed up with a 12-lead ECG or 24-hr Holter recordings at the1st, 3rd, 6th, and 12th month after the ablation procedure; and (d) those patients who did catheter ablation other than radiofrequency ablation such as surgical ablation, cryoballoon. In all, 207 consecutive patients with documented symptomatic were identified and included in the study. All patients underwent transesophageal and transthoracic echocardiography images prior to the procedure for excluding the patients who have intra-atrial thrombus or structural heart disease.

Baseline demographics, medical history, and laboratory data (including preablation age, gender, diabetes mellitus [DM], coronary artery disease [CAD], hypertension, obstructive sleep apnea [OSA], previous stroke or transient ischemic attack [TIA], drug treatment, left atrial [LA] anteroposterior diameter, left ventricular ejection fraction [LVEF], P-wave duration [PWD], interatrial block [IAB], and P-wave amplitude) were all extracted from the hospital electronic medical records. The CHADS2 (Gage et al., 2001), CAAP-AF (Winkle et al., 2016), and MVP scores were calculated for each patient.

2.2 MVP and CAAP-AF score assignment

In Table 1, the MVP ECG risk score was calculated in each patient being assigning 0–2 point for each of the following factors: PWD, IAB, and P-wave amplitude. The CAAP-AF score ranges from 0 to 13 points using baseline characteristics by the CAD, LA size, age, persistent AF, the number of antiarrhythmic drugs failed, and female gender.

2.3 ECG measurement

A standard 12-lead ECG (25 mm/s, 10 mm/mV) was obtained before the ablation procedure. These images were amplified × 10 and measured using software Image J. Each ECG was reviewed blindly by two electrophysiologists. The P-wave onset was identified as the point of initial upward or downward deflection from the baseline, and the offset was defined as the returning point of the waveform to the isoelectric line. P waves will be analyzed after we found the isoelectric interval exists and the P waves had no fusion with the preceding QRS complex or T wave (Figure 1): PWD was measured in leads II, III, and aVF of the 12 surface leads. The wave's peak or nadir to the isoelectric line was measured as the amplitude of the P wave in the lead I. Each ECG lead was measured with at least five consecutive beats as an average. PWD ≥ 120 ms was considered as prolongation. Partial IAB was defined PWD ≥ 120 ms. Advanced IAB was defined as both prolongation and a biphasic(±) morphology in the inferior leads.

2.4 Radiofrequency ablation procedures and follow-up

In all patients, catheter ablation was performed following our standard approach in institutional ablation protocol. Written informed consent was obtained in all patients after discussing the risks and benefits of the radiofrequency ablation procedure. In all cases, the PVI was done using irrigated tip catheter guided by circular mapping catheter and the 3D mapping system, and the energy was delivered with a target temperature of 45°C and a maximal power limit of 40 W. The procedural endpoint was complete absence of all PV spikes during sinus rhythm documented with the two Lasso catheters within the ipsilateral PVs at least 30 min after PV isolation. Linear ablation of the cavotricuspid and/or mitral isthmus was underwent in patients who had right or LA isthmus flutter.

Patients included in this study were followed up with a 12-lead ECG and 24-hr Holter recordings at the 1st, 3rd, 6th, and 12th month after the ablation procedure, and the records were extracted from the hospital electronic medical records. If the patient was symptomatic, a new ECG or 24-hr Holter recording was obtained. After the procedure, all patients received antiarrhythmic drugs if there were neither contraindications nor intolerance. If no recurrent atrial tachyarrhythmia occurred after 2 or 3 months, the drug treatment was discontinued. AF recurrence was defined as documented symptomatic or asymptomatic any atrial arrhythmia lasting more than 30s between 3 and 12 months after ablation.

2.5 Statistical analysis

Data were collected in EpiData (version 3.1 for Windows) and then were imported into IBM SPSS (version 26.0 for Windows) and MedCalc (version 15.2.2 for Windows) for statistical analysis. Data are reported as the means ± standard deviation (SD) for continuous variables and as number of patients and proportions for categorical data. The Kolmogorov–Smirnov test was used to test the distribution of continuous variables. When compared patients with AF recurrences and those who remain in sinus rhythm regarding baseline clinical characteristics, treatment, and outcome, we used independent t test and Mann-Whitney U for continuous variables and chi-square tests (Pearson or Fisher's exact as appropriate) for categorical variables.

Multivariate logistic regression analysis was used to test the independent association of CHADS2, MVP, and CAAP-AF scoring systems with PVI outcome. ROC curves were generated for graphical illustration of these scores’ performance in predicting rhythm outcome, with the area under the curve (AUC) being equivalent to the c index for determining the predictive value for a score. The c indices (i.e., areas under the ROC curves) for the 2 scores were compared by using DeLong's method. Kaplan–Meier analysis was conducted to determine the difference in AF recurrences and those who remain in sinus rhythm within different score categories, with survival curves generated to illustrate survival time between groups. A two-sided p < .05 was considered to be statistically significant.

3.1 Population demographics and electrocardiogram characteristics

Our retrospective analysis included 207 patients with clinical PAF underwent PVI totally. Table 2 includes the demographics and clinical characteristics of the patients who developed AF recurrence and those who remain in sinus rhythm. Of these patients, 67 (32.3%) developed recurrent AF over the course of the one-year follow-up period (Table 2). There was a significant difference between left atrial size (36.9 ± 5.1 versus 39.0 ± 5.0; p = .009) and AAD failed (61.5 versus 38.5; p = .030) in patients who had recurrence of AF relative to those without recurrence. The prevalence of cardiovascular risk factors such as diabetes, CAD, hypertension, and OSA did not differ between 2 groups. The ECG characteristics of patients with and without recurrence are shown in Table 2. The patients with recurrence had longer P-wave durations (108.8 ± 14.4 versus 104.3 ± 11.0; p < .001) and higher prevalence of advanced IAB (p < .001; Table 2). Patients with recurrent AF also had a higher baseline of CAAP-AF and MVP score. We found that, in general, the higher the CAAP-AF and MVP score, the higher the percentage of patients who had recurrence of AF at 1 year. AF recurrence rates progressively increased with parallel increasing in MVP and CAAP-AF scores. The CHADS2 score was not significantly different between the 2 groups.

3.2 Risk score for atrial fibrillation

Using the multivariate logistic regression analyses all three scores in Table 3, the MVP was significant predictors of AF recurrences (OR 2.749 95%CI 1.965–3.847 p = .000). The area of the MVP score under the curve in the ROC analysis was 0.789 (95% CI 0.730–0.840, p < .001) for all patients included in the study (Figure 2). The MVP score was a predictive factor of AF recurrence after PVI with a cut-off value of >3 (sensitivity = 53.03%, specificity = 89.87%) (Table 4). In view of the ROC curves based on the MVP, and CAAP-AF scores in predicting events, the differences between the areas under the curves reached statistical significance. MVP score is better than CAAP-AF and Chads2 in predicting the recurrence of AF. Kaplan–Meier curves show recurrence of atrial fibrillation in patients with different MVP score (Figure 3). Patients with scores above 3 had a higher rate of recurrence of atrial tachyarrhythmia (p < .001 by log-rank test).