The neutrophil/lymphocyte ratio (NLR) has recently emerged as better indicator of inflammation and oxidative stress and has been widely studied in several cardiovascular diseases. In the present study, we evaluated the role of the preablation NLR in atrial fibrillation (AF) recurrence after cryoballoon-based catheter ablation. A total of 251 patients (47.8% women, age 54.12 ± 10.9 years, 80.1% with paroxysmal AF) with symptomatic AF underwent cryoablation. At a mean follow-up of 19.0 ± 6.6 months, 60 patients (23.9%) had developed AF recurrence. The patients who developed AF recurrence had had a greater preablation NLR (3.53 ± 0.95 vs 2.65 ± 0.23, p <0.001) and a higher white blood cell count, neutrophil count, and high-sensitivity C-reaction protein levels. On multivariate regression analysis, the preablation NLR (hazard ratio 2.15, 95% confidence interval 1.70 to 2.73, p <0.001), left atrial diameter (hazard ratio 1.09, 95% confidence interval 1.04 to 1.14, p <0.001) and early AF recurrence (hazard ratio 2.99, 95% confidence interval 1.71 to 5.23, p <0.001) were independent predictors of AF recurrence after cryoablation. Using a cutoff level of 3.15, the preablation NLR predicted AF recurrence during follow-up with a sensitivity of 84% and specificity of 75%. Patients with a preablation NLR >3.15 had a 2.5-fold increased risk of developing AF recurrence after cryoablation. In conclusion, an elevated preablation NLR was associated with increased AF recurrence after cryoballoon-based catheter ablation. Our results support the role of a preablation inflammatory environment in the development of AF recurrence after ablation therapy but suggest that other factors are also important.
Catheter ablation of atrial fibrillation (AF) with the primary aim of pulmonary vein (PV) isolation has become an effective and safe therapeutic option for patients with symptomatic and drug-refractory AF. Despite the improved procedural outcomes with advances in ablation techniques, postablation AF recurrence has continued to be a major clinical problem after PV isolation, occurring in 25% to 50% of patients during follow-up. Several inflammatory parameters have been studied to predict the success rate of PV isolation and select appropriate patients for invasive strategy; however, the results have not been consistent. To the best of our knowledge, the effect of the preprocedural neutrophil/lymphocyte ratio (NLR), as an oxidative stress and inflammatory marker, on AF recurrence after cryoballoon-based PV isolation has not been previously studied. In the present study, we aimed to determine whether the presence of a preablative inflammatory state, determined using known clinical parameters and conventional markers of inflammation, including high-sensitivity C-reactive protein, white blood cell count, and NLR, could be associated with AF recurrence after cryoablation.
Methods
In the present prospective and observational study, we enrolled 251 consecutive patients who had undergone PV isolation with the cryoballoon technique for documented AF from September 2010 to November 2012. All the patients had symptomatic paroxysmal or persistent AF and ≥1 antiarrhythmic drugs had previously failed. Patients who had episodes of AF lasting >7 days were defined as having persistent AF, and those whose episodes self terminated within 7 days were defined as having paroxysmal AF.
Patients who had moderate to severe valvular disease, left atrial (LA) thrombus, uncontrolled thyroid dysfunction, preprocedural significant coronary artery stenosis, myocardial infarction or cardiac surgery in the previous 3 months, a contraindication to anticoagulation, pregnancy, or a LA diameter >55 mm were excluded from the present study. Furthermore, those with recent infection, malignancy, blood dyscrasia, autoimmune or inflammatory disease, renal failure, hepatic failure, or current therapy with corticosteroids and nonsteroidal anti-inflammatory drugs were excluded from the present study.
A detailed medical history regarding the AF and related cardiovascular and/or systemic conditions was taken for all patients. The symptomatic severity was recorded using the European Heart Rhythm Association score.
All patients provided informed consent before enrollment in the present study, which was in compliance with the principles outlined in the Declaration of Helsinki. The institutional ethics committee approved the study.
All patients underwent standard transthoracic echocardiography to rule out a structural abnormality, transesophageal echocardiography to rule out LA thrombus, and multidetector computed tomography to evaluate the PV configuration. Anticoagulation was stopped ≥48 to 72 hours before the procedure, and the preprocedural interval was bridged with enoxaparin 1 mg/kg. Antiarrhythmic drugs were discontinued 5 half-lives before the procedure.
Blood samples for the complete blood count analysis (with differential analysis) were collected in ethylene-diamine-tetraacetic acid–anticoagulated Monovette tubes (Sarstedt, Leicester, United Kingdom) 24 hours before cryoablation. The calibration was assessed daily using the commercial calibrant (Beckman Coulter, Fullerton, California) and monitored 3 times daily using internal quality control material. The NLR was calculated using data obtained from the complete blood count differential analysis. High-sensitivity C-reactive protein measurement was done using an automatized analyzer (Beckman Coulter IMMAGE) using nephelometric measurement 24 hours before cryoablation.
All procedures were performed with the patient under conscious sedation using boluses of midazolam. The invasive arterial blood pressure, oxygen saturation, and electrocardiogram were continuously monitored throughout the entire procedure. The right femoral vein and left femoral vein or artery punctures were performed using the Seldinger technique. A 6F steerable decapolar catheter (Dynamic Deca, Bard Electrophysiology, Lowell, Massachusetts) was placed in the coronary sinus. A single transseptal puncture using the modified Brockenbrough technique (BRK-1, St. Jude Medical, Minnetonka, Minnesota) was performed under fluoroscopic guidance, and an 8F transseptal sheath (Biosense Webster, Diamond Bar, California) was placed into the left atrium. Once LA access was obtained, heparin boluses were repeatedly administered to maintain the activated clotting time at 300 to 350 seconds. The sheath was then exchanged for the 12F steerable transseptal sheath (FlexCath, Medtronic CryoCath, Minneapolis, Minnesota) over a guidewire (0.032 in., 180-cm Super Stiff, St. Jude Medical, St. Paul, Minnesota). The baseline potentials of all PVs were recorded using a Lasso catheter (Biosense Webster). We paced the distal coronary sinus to confirm the presence of the left PV potentials. In all patients, the 28-mm cryoballoon catheter (Arctic Front, Medtronic CryoCath LP, Kirkland, Quebec, Canada) was used for PV isolation. The cryoballoon was maneuvered to all PV ostia using the steerable 12F sheath and a guidewire inserted through the lumen of the balloon catheter. The balloon was inflated in the left atrium and then directed toward the PV ostia. The assessment of balloon occlusion was performed through injection of 50% diluted contrast through the cryoballoon catheter’s central lumen. The duration of each freezing cycle was 300 seconds. A minimum of 2 consecutive freezing cycles for each targeted PV was delivered, with excellent or good occlusion. The procedure systematically began with the left superior, then the left inferior, followed by the right superior, and ended with the right inferior PV. The right phrenic nerve was constantly paced from the superior vena cava during freezing at the right-sided PVs. Also, direct palpation of the right hemidiaphragmatic excursion was performed during phrenic nerve stimulation. At the end of the procedure, PV conduction was re-evaluated using the Lasso catheter. Successful PV isolation was defined as the elimination (or dissociation) of all PV potentials recorded using the Lasso catheter.
Oral anticoagulation with warfarin was initiated 4 to 6 hours after the procedure, and concomitant enoxaparin 1 mg/kg was administered until a target international normalized ratio of 2.0 to 3.0 was reached. For the next 3 months, the patients continued with the antiarrhythmic drug regimen they had been prescribed before the ablation procedure. Thereafter, the procedural outcomes were assessed with the patients not using the antiarrhythmic drug regimen.
Follow-up examinations were performed at 3, 6, and 12 months after the procedure and every 6 months thereafter, or earlier if they developed symptoms consistent with recurrent AF. The need for oral anticoagulation was also evaluated after 3 months using the CHA 2 DS 2 VASc score.
Acute procedural success was defined as electrical isolation of all PVs. The first 3 months after AF ablation was defined as the blanking period. Early recurrence of AF was defined as the detection of AF (≥30-second duration assessed with electrocardiographic monitoring) within 3 months of ablation. AF recurrence was defined as the detection of AF (≥30-second duration assessed with electrocardiographic monitoring) >3 months after AF ablation.
The continuous variables are presented as the mean ± SD and categorical variables as percentages. The Shapiro-Wilk criterion was used for the assessment of normality. The study population was assigned to quartiles (Q) according to the preablation NLR (Q1, <2.12; Q2, 2.12 to 2.58; Q3, 2.59 to 3.42; Q4, >3.42). A comparison of multiple mean values was performed using the Kruskal–Wallis tests or analysis of variance, as appropriate. Comparisons of continuous data between the 2 groups (recurrence vs no recurrence) were made using an unpaired t test. The categorical data were compared in both groups using the chi-square test. Correlations were assessed using Spearman’s rank test. Receiver operating characteristic curve analysis was used to determine the optimum cutoff levels of the preprocedural NLR and LA diameter to predict the recurrence of AF after cryoablation. The interval to AF recurrence was plotted using Kaplan-Meier curves for patients with AF stratified by the NLR quartile (with a blanking period of 3 months after cryoablation applied). Cox proportional hazards regression analysis was used to test the effect of the explanatory variables on AF recurrence, adjusted for other variables. A p value <0.05 was considered statistically significant. All analyses were performed, using the Statistical Package for Social Sciences software, version 20.0 (SPSS, Chicago, Illinois).
Results
The study population consisted of 251 patients (age 54.12 ± 10.9, 47.8% women), with either paroxysmal (n = 201) or persistent (n = 50) AF. The thromboprophylaxis history was warfarin in 76 patients (30.3%), clopidogrel in 20 patients (7.9%), and aspirin in 192 patients (76.5%). The clinical, echocardiographic, and laboratory data of the study population are listed in Table 1 .
| Parameter | Total (n = 251) | Recurrence | p Value | |
|---|---|---|---|---|
| No (n = 191) | Yes (n = 60) | |||
| Clinical | ||||
| Age (yrs) | 54.12 ± 10.9 | 53.1 ± 10.7 | 57.3 ± 10.8 | 0.008 |
| Women | 120 (47.8) | 96 (50.3) | 24 (40) | 0.107 |
| BMI (kg/m 2 ) | 25.5 ± 5.8 | 24.6 ± 4.5 | 26.4 ± 5.1 | 0.085 |
| History of CAD ∗ | 27 (10.8) | 16 (8.4) | 11 (18.3) | 0.031 |
| Diabetes mellitus | 36 (14.3) | 26 (13.6) | 10 (16.7) | 0.345 |
| Dyslipidemia † | 49 (19.5) | 33 (17.3) | 16 (26.7) | 0.081 |
| Hypertension | 104 (41.4) | 74 (38.7) | 30 (50) | 0.082 |
| Alcohol intake ‡ | 20 (8.0) | 14 (7.3) | 6 (10) | 0.335 |
| Current smoker | 83 (33.1) | 57 (29.8) | 26 (43.3) | 0.051 |
| AF type | <0.001 | |||
| Paroxysmal | 201 (80.1) | 166 (86.9) | 35 (58.3) | |
| Persistent | 50 (19.9) | 25 (13.1) | 25 (41.7) | |
| AF duration (yrs) | 6.1 ± 4.5 | 5.4 ± 3.5 | 8.1 ± 6.5 | <0.001 |
| LA diameter (mm) | 38.5 ± 5.36 | 37.7 ± 4.6 | 41.5 ± 6.5 | <0.001 |
| LVEF (%) | 64.5 ± 6.0 | 65.2 ± 3.9 | 62.3 ± 9.7 | 0.001 |
| Failed antiarrhythmic agents | 1.75 ± 0.70 | 1.60 ± 0.45 | 1.83 ± 0.74 | 0.068 |
| EHRA score | 2.96 ± 0.6 | 3.13 ± 0.62 | 2.91 ± 0.59 | 0.076 |
| Statins | 45 (17.9) | 34 (17.8) | 11 (18.3) | 0.245 |
| ACE inhibitor or ARB | 128 (51) | 97 (50.8) | 31 (51.7) | 0.442 |
| Preprocedural laboratory test | ||||
| Hemoglobin (g/dl) | 13.5 ± 1.9 | 13.6 ± 1.9 | 13.5 ± 1.8 | 0.593 |
| WBC count (×10 9 /L) | 7,815 ± 2,367 | 7,462 ± 2,345 | 8,940 ± 2,085 | <0.001 |
| Neutrophil count (×10 9 /L) | 5,321 ± 1,125 | 4,912 ± 1,257 | 6,623 ± 1,700 | <0.001 |
| Lymphocyte count (×10 9 /L) | 1,866 ± 138 | 1,862 ± 137 | 1,882 ± 139 | 0.317 |
| Monocyte count (×10 9 /L) | 543 ± 44 | 543 ± 46 | 541 ± 36 | 0.765 |
| NLR | 2.86 ± 0.62 | 2.65 ± 0.23 | 3.53 ± 0.95 | <0.001 |
| High-sensitivity C-reactive protein (mg/L) | 1.78 ± 0.37 | 1.77 ± 0.36 | 1.81 ± 0.36 | 0.007 |
| Follow-up | ||||
| Early recurrence | 38 (15.1) | 11 (5.8) | 27 (45) | <0.001 |
| Follow-up duration (mo) | 19 ± 6.6 | 18.45 ± 6.4 | 20.9 ± 6.9 | 0.010 |
∗ Defined as history of ischemic heart disease.
† Defined as total cholesterol ≥200 mg/dl or treatment with a lipid-lowering agent.
‡ Defined as ≤1 drink/day for women and ≤2 drinks/day for men, with those with heavy drinking and alcohol abuse excluded.
Acute procedural success was achieved in 1,035 of 1,040 PVs (99.5%). The median cryoballoon application per PV was 2 episodes (range 2 to 5). The mean procedural and fluoroscopy time was 70.6 ± 4.8 minutes (range 50 to 90) and 14.3 ± 4.1 minutes (range 10 to 25). Major complications developed in 3 patients (1.19%), including intraprocedural pericardial tamponade that was successfully treated with percutaneous drainage in 2 patients and femoral arteriovenous fistula that was surgically repaired in 1 patient. Minor complications were seen in 14 patients (5.5%) and included temporary phrenic nerve palsy in 4 patients and inguinal hematoma and/or pseudoaneurysm in 10 patients.
After a mean follow-up period of 19 ± 6.6 months (range 8 to 29), early recurrence developed in 38 patients (15.1%), and recurrence after the blanking period was observed in 60 patients (23.9%). Redo catheter ablation using a radiofrequency technique was performed in 10 of 60 patients with recurrent AF. The patients with AF recurrence were older and had a higher rate of coronary artery disease, nonparoxysmal AF, and early recurrence, a reduced left ventricular ejection fraction, an increased LA diameter, an increased white blood cell count, an increased neutrophil count, and high-sensitivity C-reactive protein levels, and an increased NLR ratio ( Table 1 and Figure 1 ) compared with those who remained in sinus rhythm (p <0.05).
The baseline demographic and clinical data of the patients stratified by NLR quartile are listed in Table 2 . The patients in Q4 had a higher rate of nonparoxysmal AF, an increased AF duration, an increased white blood cell count, an increased neutrophil count, a reduced lymphocyte count, an increased NLR ratio, and a higher rate of early AF recurrence and recurrence ( Figure 2 ) compared with those in Q1, Q2, and Q3 (p <0.05).
| Parameter | Q1 (<2.12; n = 60) | Q2 (2.12–2.58; n = 59) | Q3 (2.59–3.42; n = 68) | Q4 (>3.42; n = 64) | p Value |
|---|---|---|---|---|---|
| Clinical | |||||
| Age (yrs) | 53.8 ± 10.8 | 54.3 ± 11.2 | 53.6 ± 11.7 | 54.8 ± 9.9 | 0.917 |
| Women | 32 (53.3) | 29 (49.2) | 32 (47.1) | 27 (42.2) | 0.659 |
| BMI (kg/m 2 ) | 24.3 ± 5.1 | 24.9 ± 5.4 | 25.6 ± 4.8 | 26.3 ± 5.6 | 0.085 |
| Current smoker | 20 (33.3) | 20 (33.9) | 19 (27.9) | 24 (37.5) | 0.343 |
| Diabetes mellitus | 9 (15.0) | 11 (18.6) | 12 (17.6) | 4 (6.2) | 0.177 |
| Hypertension | 24 (40.0) | 26 (44.1) | 31 (45.6) | 23 (35.9) | 0.682 |
| History of CAD ∗ | 4 (6.7) | 5 (8.5) | 10 (14.7) | 8 (12.5) | 0.445 |
| Dyslipidemia † | 10 (16.7) | 10 (16.9) | 15 (22.1) | 14 (21.9) | 0.786 |
| Alcohol intake ‡ | 3 (5.0) | 2 (3.4) | 5 (7.4) | 10 (15.6) | 0.056 |
| AF type | <0.001 | ||||
| Paroxysmal | 56 (93.3) | 51 (86.4) | 53 (77.9) | 41 (64.1) | |
| Persistent | 4 (6.7) | 8 (13.6) | 15 (22.1) | 23 (35.9) | |
| AF duration (yrs) | 5.2 ± 2.6 | 5.6 ± 4.0 | 5.5 ± 3.6 | 7.9 ± 6.4 | 0.003 |
| EHRA score | 2.83 ± 0.58 | 3.0 ± 0.58 | 2.96 ± 0.63 | 3.06 ± 0.6 | 0.199 |
| LA diameter (mm) | 38.6 ± 5.6 | 38.3 ± 4.6 | 38.4 ± 5.2 | 39.0 ± 5.9 | 0.854 |
| LVEF (%) | 65.2 ± 4.6 | 65.0 ± 3.9 | 63.7 ± 6.1 | 64.1 ± 8.2 | 0.462 |
| Statins | 10 (16.6) | 10 (16.9) | 12 (17.6) | 13 (20.3) | 0.084 |
| ACE inhibitor or ARB | 31 (51.7) | 30 (50.8) | 34 (50) | 33 (51.5) | 0.335 |
| Preprocedural laboratory test | |||||
| Hemoglobin (g/dl) | 13.46 ± 1.94 | 13.4 ± 1.8 | 13.9 ± 2.0 | 13.4 ± 1.9 | 0.658 |
| WBC count (×10 9 /L) | 7,170 ± 2,192 | 7,957 ± 2,275 | 7,223 ± 2,329 | 8,918 ± 2,274 | <0.001 |
| Neutrophil count (×10 9 /L) | 4,752 ± 1,918 | 4,923 ± 2,000 | 5,022 ± 2,383 | 6,540 ± 1,685 | <0.001 |
| Lymphocyte count (×10 9 /L) | 1,990 ± 1,000 | 1,894 ± 804 | 1,805 ± 802 | 1,790 ± 900 | <0.001 |
| Monocyte count (×10 9 /L) | 538 ± 43 | 545 ± 46 | 547 ± 48 | 539 ± 39 | 0.592 |
| NLR | 2.08 ± 0.12 | 2.40 ± 0.14 | 2.78 ± 0.27 | 3.63 ± 0.81 | <0.001 |
| High-sensitivity C-reactive protein (mg/L) | 1.73 ± 0.37 | 1.79 ± 0.35 | 1.80 ± 0.38 | 1.79 ± 0.37 | 0.704 |
| Follow-up | |||||
| Follow-up period (mo) | 18.9 ± 5.9 | 18.8 ± 6.6 | 18.2 ± 6.8 | 20.3 ± 6.9 | 0.330 |
| Early recurrence | 4 (6.7) | 6 (10.2) | 11 (16.2) | 17 (26.6) | 0.011 |
| Recurrence | 4 (6.7) | 6 (10.2) | 13 (19.1) | 37 (57.8) | <0.001 |
∗ Defined as a history of ischemic heart disease.
† Defined as total cholesterol ≥200 mg/dl or treatment with a lipid-lowering agent.
‡ Defined as ≤1 drink/day for women and ≤2 drinks/day for men, with those with heavy drinking and alcohol abuse excluded.
