Methods

We conducted a systematic review using a predefined protocol and in accordance with the Meta-Analysis of Observational Studies in Epidemiology statement. We identified reports in any language by searching Medline (1950 to March 2009), Embase (1980 to March 2009), and the Cochrane Registry of Controlled Trials (to the first quarter of 2009) for clinical studies evaluating AF catheter ablation in patients with LVSD. Our search combined 3 search themes: (1) terms related to AF, (2) terms related to catheter ablation, and (3) terms designed to identify randomized or observational clinical studies (see the Supplementary Materials for the complete search strategy). We supplemented the database search by scanning the bibliographies of reviews and abstracts from the American Heart Association (2007 and 2008) and the Heart Rhythm Society (2007 to 2009) scientific sessions.

Two reviewers (S.B.W. and A.F.) independently screened the titles and abstracts of all records. We retrieved reports for full-text review if either reviewer believed that they reported original data on patients with LVSD who underwent AF catheter ablation. Reports dealing with total atrioventricular node ablation or open surgical ablation were excluded. We then reviewed the full text of all retrieved studies in duplicate. Reports were included in the systematic review if they (1) reported original results of AF catheter ablation; (2) enrolled patients with LVSD, defined as an LVEF <0.50, either exclusively or in a separately reported group; (3) followed ≥25 patients (4) for ≥6 months; and (5) reported on ≥1 end point of interest. These end points included recurrence of AF or atrial tachycardia (AT), adverse events, and heart failure end points, including changes in LVEF, functional status, quality of life, or mortality. We extracted data about study design and patient characteristics, concomitant medical therapy, details of the ablation procedure, definitions of AF or AT recurrence, and adverse events. We recorded the absolute proportion of recurrent AF or AT as well as any effect measure (relative risk [RR], odds ratio, or hazard ratio) used to compare ablation outcomes in patients with and without LVSD. Finally, we extracted data relevant to study quality, using a published guide for evaluating the internal validity of observational studies. We considered sample selection, baseline clinical characteristics, measures taken to monitor for asymptomatic recurrence of AF or AT, blinding of outcome assessment, completeness of follow-up, and statistical methods used to minimize bias.

Measured data were recorded as mean ± SD. We calculated the Mantel-Haenszel pooled RR of recurrent AF or AT after ablation in patients with versus without LVSD. We also calculated the pooled absolute change in the LVEF during follow-up. We used Cochran’s Q statistic to assess between-study heterogeneity. In the absence of significant heterogeneity, fixed-effects models were used to calculate pooled effects. When heterogeneity was present, we used random-effects models and sought to identify its source(s) by performing stratified analyses on the basis of patient and study characteristics. A p value <0.05 was considered statistically significant. Stata version 11 (StataCorp LP, College Station, Texas) was used for analysis.

Results

The results of our search and selection are detailed in Figure 1 . The database search yielded 1,925 citations, 37 of which were selected for full-text review. Bibliographic hand search did not yield additional reports. One reviewed abstract met the inclusion criteria and has since been published. After full-text review, 8 reports were included. The reasons for exclusion of the others are listed in Figure 1 .

Progress through the systematic review. HCM = hypertrophic cardiomyopathy.

Table 1 outlines the characteristics of the included studies. The 8 reports, published from 2004 to 2009, followed a total of 1,851 patients who underwent AF catheter ablation, 483 of whom had LVSD. There were 7 single-center observational studies, most originating from centers whose investigators make frequent contributions to the published research on AF catheter ablation. The remaining study was the Pulmonary Vein Isolation Versus AV Nodal Ablation With Biventricular Pacing for Patients With Atrial Fibrillation With Congestive Heart Failure (PABA-CHF) randomized trial.

Table 1

Study and patient characteristics

Characteristic	Chen et al (2004)		Hsu et al (2004)		Tondo et al (2006)		Gentlesk et al (2007)		Nademanee et al (2008)	Khan et al (2008)		Lutomsky et al (2008)		De Potter et al (2010)
Prospective design	No		No		Yes		Yes		Yes	Yes (RCT)		Yes		No
Multicenter	No		No		No		No		No	Yes		No		No
Sample size	377		116		105		366		635	81		70		72
Low-LVEF sample	94 (25%)		58 (50%)		40 (38%)		67 (18%)		129 (20%)	81 (100%)		18 (26%)		36 (50%)
Patient characteristics	Low LVEF	Normal LVEF	Low LVEF	Normal LVEF	Low LVEF	Normal LVEF	Low LVEF	Normal LVEF		Abl	BiV	Low LVEF	Normal LVEF	Low LVEF	Normal LVEF
Mean age (years)	57	55	56	56	57	56	54	54	67	60	61	—	—	52	51
Men	80%	78%	88%	88%	70%	88%	93%	76%	67%	95%	88%	—	—	89%	94%
Mean AF duration (months)	72	60	80	79	36	48	67	71	40	48	47	—	—	44	78
Mean number of AADs used	3	3	3	3	3	3	—	—	2.6	—	—	—	—	—	—
Paroxysmal AF	41%	55%	9%	9%	25%	23%	70%	82%	40%	49%	55%	100%	100%	39%	—
CAD	91%	22%	20%	9%	25%	29%	18%	9%	215	73%	68%	—	—	25%	—
Nonischemic CM			66%	7%	50%	3%	74%	—	11%	—	—	—	—	50%	—
Valvular HD	16%	13%	16%	5%	25%	18%	9%	5%	17%	—	—	—	—	11%	—
Other structural HD	—	—	6%	0%	—	—	—	—	—	—	—	—	—	14%	—
NYHA class ≥II	100%	5%	100%	—	—	—	—	—	—	100%	100%	—	—	—	—
Mean LVEF	0.36	0.54	0.35	0.66	0.33	0.64	0.42	0.61	0.30	0.27	0.29	0.41	0.60	0.41	0.63
Mean LA diameter (mm)	47	45	50	46	48	44	44	48	—	49	47	—	—	43	43
Primary ablation procedure	PVI plus		PVI plus		PVI plus		PVI		CFAE	PVI plus		PVI		PVI plus
Mean number of procedures	1.2	1.1	1.5	1.5	1.3	1.2	1.6	1.3	1.7	1.2	N/A	1.0	1.0	1.4	1.4
Mean follow-up (months)	14	15	12	12	14	14	20	20	27	6	6	6	6	14	17
Definition of AF/AT recurrence	Any episode		Any episode		Any episode		Any episode		Any episode	Any episode		Any episode		Any episode
Blanking period (months)	1		0 ⁎		1		1		3	2		1		3
Detection of asymptomatic AF recurrence
ECG timing (months)	2, 3, 6, 12		—		1, 3, 6, 12		Per 3		Per 3	—		—		3, 6, 12
Holter monitoring (months)	3, 6, 12		1, 3, 6, 12		1, 3, 6, 12		—		Per 12	—		—		3, 6, 12
TTM	At 1 month		—		3 per week		—					Daily for 6 months		—
ER	—		—		—		At 6 weeks and 6 months		—	At 2–6 months		—		—

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