The Influence of Catheter Ablation for Atrial Fibrillation on Atrial Electrical
Condition: Atrial Fibrillation
MeSH terms: Atrial Fibrillation; Atrial Remodeling
Study type: Interventional

Summary: 
      This study explored the influence of radiofrequency catheter ablation and cryoballoon
      ablation on atrial electrical remodeling in patients with atrial fibrillation,the
      relationship between atrial electrical remodeling and structural remodeling,and which
      indicators are associated with atrial recurrence after catheter ablation.
    

Detailed description: 
      From September 2017 to September 2019, the investigators enroll consecutive patients with
      symptomatic atrial fibrillation (AF) who were scheduled for an initial catheter ablation,
      including paroxysmal and persistent AF.Patients are divided in to three group: paroxysmal AF
      in radiofrequency ablation group, persistent AF in radiofrequency ablation group, and
      paroxysmal AF in Cryoablation group.

        1. Paroxysmal AF group: The p-wave duration, P wave dispersion and P wave amplitude are
           detected before and 24 hours after procedure.The atrial effective refractory period,
           refractory period dispersion, frequency adaptation and atrial conduction time were
           tested before and after procedure. Detect atrial electromechanical conduction time in
           the tissue doppler before and 1 week after procedure.

        2. Persistent AF group: The p-wave duration, P wave dispersion and P wave amplitude are
           detected 24 hours after procedure.The atrial effective refractory period, refractory
           period dispersion, frequency adaptation and atrial conduction time were tested after
           procedure. Detect atrial electromechanical conduction time in the tissue doppler 1 week
           after procedure.

        3. Method of detection of atrial electrical remodeling: 1). the measurement of surface
           electrocardiogram: the p-wave amplitude, P wave time duration and the p-wave duration
           dispersion (dP =Pmax- Pmin) of the same 12 lead electrocardiogram in the same cardiac
           cycle.Two cardiologists measured the value separately.The investigators record the mean
           value. 2). Atrial effective refractory period (AERP) measured from the high right
           atrium(HRA,the junction of superior vena cava and the right atrium , near the sinus
           node), low lateral right atrium(LLRA,the junction of inferior vena cava and the right
           atrium,on the right atrium free wall side), coronary sinus electrode (CS)7.8, and CS1.2
           at 3 basic drive cycle lengths (CLs) of 600, 500, and 400 ms. Pacing was performed using
           a pulse width of 2 ms and a current output of twice the local diastolic threshold. If
           the latter was 2.0 milliampere (mA), the catheter was replaced and the threshold
           repeated. AERP was measured using an 8-beat drive train and a single extrastimulus
           incremented by 10 ms from a starting point of 170 ms. Every AERP was repeated 3 times,
           and the mean was taken. 3). At each CL, the dispersion of refractoriness was measured by
           subtracting the minimum from the maximum AERP across the 4 sites.

        4. Rate adaption of AERP: With the gradual shortening of the pacing cycle lengths, the
           atrial effective refractory should be shortened accordingly. The rate adaption of AERP
           was observed in different pacing cycle lengths.

        5. Atrial conduction time measured at the HRA after 30 seconds of constant pacing at a CL
           of 600, 500, and 400 ms. Conduction time is measured from the pacing artifact to the
           onset of the first initial sharp deflection recorded to the first A wave at CS1.10 and
           CS1.2. Total atrial conduction time=Pace HRA-Acs1.2; Right atrial conduction
           time=PaceHRA-Acs9.10; Left atrial conduction time=Acs9.10-Acs1.2.6). Atrial
           electromechanical conduction time: three sampling points are taken at lateral mitral
           valve(Sa1), septal mitral valve(Sa2), lateral tricuspid valve (Sa3), in the tissue
           doppler four-chamber view. Atrial electromechanical conduction time is measured from
           electrocardiogram P wave initiation to ultrasound A wave initiation. Total atrial
           electromechanical conduction time=T1-T3;Right atrial electromechanical conduction
           time=T2-T3; Light atrial electromechanical conduction time=T2-T1.

      All patients fill the follow-up form before procedure. After catheter ablation therapy, all
      patients invited to come back to the outpatient clinic every week in the first month, and
      then at 2, 3, 6, 9, and 12 month to follow up. Patients received electrocardiogram and Holter
      monitor examination if with symptoms of palpitations. Those patients with no symptoms
      received electrocardiogram every month and Holter monitor examination every 6 months.
      Recurrence of atrial fibrillation was defined as atrial fibrillation/flutter or atrial
      tachycardia lasting ≥ 30 seconds 3 months after radiofrequency catheter ablation therapy.
      Patients who have AF recurrence within three months after therapy will not be considered for
      repeated radiofrequency ablation.Blood samples (routine blood, high sensitivity c-reactive
      protein,B-type natriuretic peptide (BNP), cystatin C,homocysteine,β2-microglobulin) and
      transthoracic echocardiography indexes (left atrial anterior to posterior diameter, left
      atrial length-diameter,left atrial transverse-diameter,left atrial volume index, mitral e', E
      peak, A peak, E/A,velocity time integral (VTI), left atrial ejection fraction, left atrial
      strain, strain rate and atrial electrical - mechanical conduction time) are recorded in all
      patients at each follow-up. Patients with AF recurrence must have an electrocardiogram or a
      24 hour holter monitor evidence.
    

Intervention name(s): radiofrequency ablation or cryoballoon
Intervention type(s): Procedure
Intervention description(s): Patients in radiofrequency ablation group receive circumferential pulmonary vein isolation,and no additional ablation is performed in the extrapulmonary sites unless the patient is diagnosed with atrial flutter before the operation. And Cryoablation is performed using a single cryoballoon. The diameter of the cryoballoon is determined as 28 mm or 23 mm according to pulmonary venography results.
Allocation: Non-Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Outcomes Assessor)
Primary purpose: Treatment
Keywords: atrial fibrillation; atrial electrical remodeling