Optimal Catheter Ablation of Persistent AFib: The STAR AF 2 Trial

Educational Objectives

Distinguish between ablation of persistent atrial fibrillation (AF) and paroxysmal AF.

Summary

Interviewer: C. Richard Conti, MD, MACC

Take-home Messages:

• Ablation of persistent AF is challenging and typically has less favorable outcomes compared to paroxysmal AF.
• In the largest randomized trial to examine outcomes of catheter ablation in persistent AF, catheter ablation with pulmonary vein isolation achieved reasonable outcomes.
• Adding complex fractionated electrograms or additional lines of ablation increased procedural time (perhaps increasing risk) with no benefit in AF reduction.

The concept of “less may be more” may apply to ablation for persistent atrial fibrillation. In the largest randomized trial to examine outcomes of ablation in persistent AF (N = 589), patients were randomized to either pulmonary vein ablation (PVA; sometimes referred to as pulmonary vein isolation or PVI) alone, PVA plus ablation of atrial regions of the heart that produce abnormal electrograms, or PVA plus ablation of linear lesions in the left atrium.

It’s an important question, because the optimal ablation approach is unclear for patients with persistent AF. AF is often triggered by ectopic atrial activity emerging from the pulmonary veins, so by electrically isolating the veins and blocking the “triggers,” initiation of AF can be prevented in a substantial number of patients. The strongest evidence supporting the efficacy of catheter ablation for paroxysmal AF is in younger patients with little to no structural heart disease.

However, AF ablation is being used increasingly for persistent AF, and in these patients data on the efficacy of a “trigger-based” ablation strategy are conflicting. Many studies have shown that success rates of PVA are lower in patients with persistent AF. In order to improve outcomes for persistent AF, operators sometimes use more extensive ablation based on linear lesions or complex fractionated electrograms (CFEs) in addition to PVI. However, use of more extensive ablative techniques increase both procedural time and fluoroscopic exposure, as well as risk of complications.

STAR AF II

STAR AF II is the acronym for the Substrate and Trigger Ablation for Reduction of Atrial Fibrillation Part 2 trial. In the pilot STAR AF trial, when PVI was combined with CFE ablation, the more aggressive strategy was more effective than either approach alone, particularly in patients with persistent AF.¹ However, the patient numbers for the persistent AF subgroup analysis were quite small, so results were inconclusive.

The specifics of the approaches studied in the larger STAR AF II trial² were:

• PVA = PV antral isolation with documentation of both entrance and exit block by a circular mapping catheter
• PVA + CFE = PVI followed by mapping and ablation of complex fractionated electrograms during AF identified by validated software using a 3-dimensional (3D) mapping system
• PVA + lines = PVI followed by a left atrial roof line and a line along the mitral valve isthmus with documentation of bidirectional block confirmed by prespecified pacing maneuvers

Repeat ablation procedures were allowed — ideally 3 to 6 months after the first procedure, using the identical randomized strategy as the first ablation. Patients were followed for 18 months with a visit, electrocardiogram (ECG), and 24-hour Holter monitoring at 3, 6, 9, 12, and 18 months. Data were collected weekly by phone for the 18 months as well as whenever symptoms occurred.

Additional CFE or lines ablation increased procedural time (Table 1) without providing any significant benefit (Table 2). PVI alone achieved freedom from recurrence in about 50% of patients — comparable to published success rates from randomized, multicenter trials in paroxysmal AF.

Table 1 STAR AF II: Procedural Characteristics

	PVI	PVI + CFE	PVI + LINES	p value
Procedure time (min)	166.95 ± 54.83	229.16 ± 83.20	222.56 ± 89.37	<0.0001
Mapping time (min)	13.89 ± 6.64	18.75 ± 14.01	14.38 ± 7.68	<0.0001
Fluoroscopy time (min)	29.35 ± 16.21	42.11 ± 21.70	40.91 ± 24.97	0.0003

PVI = pulmonary vein isolation; CFE = complex fractionated electrograms

Table 2 STAR AF II: Primary and Secondary Outcomes

	PVI	PVI + CFE	PVI + LINES	p value
Freedom from AF after 1 procedure	59 %	48 %	44 %	0.15
Freedom from AF/AFL/AT after 1 procedure	49 %	41 %	37 %	0.15
Freedom from AF after 2 procedures	72 %	60 %	58 %	0.18
Freedom from AF/AFL/AT after 2 procedures	60 %	50 %	48 %	0.24
Percentage of patients still on AAD at 18 mo	11 %	12 %	12 %	0.35

PVI = pulmonary vein isolation; CFE = complex fractionated electrograms; AF = atrial fibrillation; AFL = atrial flutter; AT = atrial tachycardia; AAD = anti-arrhythmic drug

Atul Verma, MD, Southlake Regional Health Centre, Newmarket, Ontario, Canada, said, “The more complex ablation procedures took almost an hour longer with about 33% more x-ray exposure for both operator and patient. And yet they offered absolutely no increased benefit over the more minimal procedures. If anything, the more minimal procedures had a better outcome, although the differences were not statistically significant.”

Readings

1. Verma A, Mantovan R, Macle L, et al. Substrate and Trigger Ablation for Reduction of Atrial Fibrillation (STAR AF): A randomized, multicentre, international trial. Eur Heart J 2010;31:1344-56

2. Verma A, Sanders P, Macle L, et al. Substrate and Trigger Ablation for Reduction of Atrial Fibrillation Trial-Part II (STAR AF II): design and rationale. Am Heart J 2012;164:1-6.

Disclosures

Atul Verma, MD
St Jude Medical Inc (G); Medtronic Inc (G); Biosense Webster Inc (G)

Interviewer: C. Richard Conti, MD, MACC
This author has nothing to disclose.

The planning committee reported nothing to disclose.

A = Advisory panel B = Speakers’ bureau C = Consultant fees/honoraria D = Data and Safety Monitoring Board E = Equity interests/stock options F = Fellowship support G = Grant support L = Licensing Agreement O = Other relationship R = Royalties S = Salary W = Expert witness

Acknowledgements

CME/CE INFO

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The Audio- Digest Foundation designates this enduring material for a maximum of 0 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

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Lecture ID:

AC470404

Expiration:

This CME course qualifies for AMA PRA Category 1 Credits™ for 3 years from the date of publication.

Instructions:

To earn CME/CE credit for this course, you must complete all the following components in the order recommended: (1) Review introductory course content, including Educational Objectives and Faculty/Planner Disclosures; (2) Listen to the audio program and review accompanying learning materials; (3) Complete posttest (only after completing Step 2) and earn a passing score of at least 80%. Taking the course Pretest and completing the Evaluation Survey are strongly recommended (but not mandatory) components of completing this CME/CE course.

Estimated time to complete this CME/CE course:

Approximately 2x the length of the recorded lecture to account for time spent studying accompanying learning materials and completing tests.

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