ANKARA, TURKEY. A recent study involving participants in the Framingham Heart Study concluded that a high white blood cell (WBC) count is a risk factor for the development of atrial fibrillation (AF). Now a group of researchers from Hacettepe University of Medicine reports that a high WBC count prior to ablation is a risk factor for AF recurrence post-ablation. More specifically, they found that a high neutrophil count and an elevated neutrophil to lymphocyte ratio (NLR) predicted an increased risk of recurrence.
- White blood cells are cells of the immune system (found in the blood stream) involved in defending the body against infections and foreign materials. A normal WBC count is between 4500 and 10000 cells per microliter.
- Neutrophils are a specialized form of white blood cells that help defend against bacterial and fungal infections. They are the "first responders" to microbial infections; their activity and death in large numbers form pus. A normal neutrophil level is around 50 to 60% of WBC count.
- Lymphocytes are small white blood cells. Blood contains three types – B cells (produces antibodies that bind to pathogens to target them for destruction), T cells and Natural killer cells. A normal lymphocyte level is around 30% of WBC count.
- High levels of WBCs are an indication of a heightened immune system response and the accompanying inflammation.
The Turkish study involved 251 patients with symptomatic paroxysmal (80%) or persistent (20%) atrial fibrillation. The average age of the participants was 54 years, 52% were men, 41% had hypertension, 14% had diabetes, but only 11% had a history of heart disease. Prior to their scheduled ablation all patients underwent transthoracic and transesophageal echocardiography and a CT scan to determine the configuration of pulmonary veins. The ablation was carried out using a 28 mm cryoballoon catheter (Arctic Front). Total average procedure time was 70 minutes and average fluoroscopy time was 14 minutes. Follow-up examinations were performed at 3, 6 and 12 months after the procedure and every 6 months thereafter.
During a mean follow-up of 19 months early recurrence, defined as one or more AF episodes (lasting 30 seconds or longer) occurring during the first 3 months following the ablation (blanking period), developed in 38 patients (15.1%) and recurrence after the blanking period was observed in 60 patients (23.9%). Compared to patients who remained in sinus rhythm during follow-up, those with recurrence were older and had a higher rate of coronary artery disease, persistent AF, early recurrence, reduced left ventricular ejection fraction, increased left atrial diameter, increased WBC count, increased neutrophil count and NLR, and elevated high-sensitivity C-reactive protein (CRP) levels.
However, on multivariate analysis, only an increased left atrial diameter, early recurrence, and an elevated NLR were associated with recurrence. A NLR above 3.15 was highly predictive of recurrence and patients with both an NLR above 3.15 and early recurrence were 19 times more likely to experience later recurrence than those with no early recurrence and a NLR below 3.15.
The researchers conclude that a pre-ablation inflammatory environment is predictive of ablation failure and suggest that treatment of this inflammation with pharmaceutical drugs may improve ablation outcome.Canpolat, U, et al. Role of preablation neutrophil/lymphocyte ratio on outcomes of cryoballoon-based atrial fibrillation ablation. American Journal of Cardiology, Vol. 112, 2013, pp. 513-19 Editor's comment
: The idea that inflammation is a cause of AF has long been debated and it is not yet entirely clear which is the cause and which is the effect. Nevertheless, going into an ablation with a normal WBC count and a low NLR would seem prudent. Of course, inflammation does not arise just out of the blue and it may be even more beneficial if the cause of the inflammation was determined and dealt with prior to ablation.