Pulmonary vein isolation (PVI) for paroxysmal atrial fibrillation (PAF) has limited success. The superior vena cava (SVC) has been identified as one of the most common non-pulmonary vein triggers for PAF. It is estimated that SVC isolation (SVCI) could improve the clinical results for patients with PAF. However, results from previous studies about SVCI remain controversial. It is possible that safety concerns for SVCI outweigh its benefits and lead to inadequate ablation. To address this issue, the introduction of a quantitative ablation index (AI) for SVCI may provide a solution.

The goal of this prospective, randomized controlled trial is to test the efficacy and safety of quantitative SVCI in addition to PVI in PAF. Participants with PAF will be randomly assigned to either PVI group or PVI+ quantitative SVCI group in a 1:1 ratio and will be followed up for 12 months. The main questions it aims to answer are:

1. Evaluate the efficacy of PVI+SVCI guided by quantitative AI.
2. Assess the safety of PVI+SVCI guided by quantitative AI.

The primary end point is treatment success at 3 months after the index ablation. The secondary end points include treatment success at 12 months, and safety outcomes.

Catheter ablation has emerged as an effective treatment for drug-refractory PAF and is recommended as first-line therapy by current guidelines. PVI is considered the cornerstone of catheter ablation for atrial fibrillation (AF). However, despite persistent PVI, a subgroup of patients may experience recurrent AF due to focal ectopic discharges originating outside the pulmonary veins. Among the non-pulmonary vein triggers, the SVC stands out as a common culprit, making it a promising ablation target for maintaining sinus rhythm.

Nevertheless, results from previous studies that evaluate the efficacy of SVCI showed conflicting results. One possible explanation is that SVC is adjacent to critical anatomy structures (such as the sinus node and the phrenic nerve), which raises safety concerns and often leads to inadequate ablation.

Therefore, it is necessary to establish standardized ablation procedure for SVCI, ensuring both safety and efficacy. To address this issue, we proposed the concept of "quantitative ablation for SVCI." By introducing AI as a quantitative measure, it is possible to achieve precise catheter ablation while minimizing the risk of procedure-related complications.

The SCORE trial is single-center, prospective, randomized controlled trial aiming to enroll 290 patients with PAF. Participants with PAF will be randomly assigned to either PVI group or PVI+ quantitative SVCI group in a 1:1 ratio, and will be followed up for 12 months. The goal is to determine whether quantitative SVCI could improve clinical results for PAF when added to PVI. The key objectives are as follows:

1. Evaluate the efficacy of PVI+SVCI guided by quantitative AI.
2. Assess the safety of PVI+SVCI guided by quantitative AI.

The primary endpoint of the study is treatment success, defined as freedom from AF, atrial flutter, or atrial tachycardia lasting longer than 30 seconds, at the 3-month follow-up. Secondary endpoints include treatment success at the 12-month follow-up and safety outcomes, including death, stroke/TIA, pericardial tamponade or effusion requiring drainage, pulmonary vein stenosis, superior vena cava stenosis, diaphragmatic nerve injury or paralysis, sinus node dysfunction, and atrial esophageal fistula.

Inclusion Criteria:

• Symptomatic paroxysmal AF that are unresponsive to antiarrhythmic drugs (one or more than one).
• Willing to undergo catheter ablation for AF.
• Age: 40-75 years old.

Exclusion Criteria:

• History of any type of catheter ablation for cardiac arrhythmias.
• History of any type of thoracic surgery, including cardiac surgery.
• History of malignant tumors.
• History of permanent pacemaker implantation.
• Peripherally inserted central catheter for long-term
• Heart failure (left ventricular ejection fraction ≤40% or NYHA class III~IV).
• Sinus node dysfunction
• Allergy to contrast agents.
• Pregnancy or lactation.
• Age: <40yrs or >75yrs.