Radiofrequency ablation in patients undergoing mitral valve surgery with or without giant left atria: A retrospective, single-center, cohort study

doi:10.21203/rs.3.rs-1330046/v1

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Research Article

Radiofrequency ablation in patients undergoing mitral valve surgery with or without giant left atria: A retrospective, single-center, cohort study

https://doi.org/10.21203/rs.3.rs-1330046/v1

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Background

For patients with giant left atria, outcomes of surgical ablation remain controversial. We aimed to compare the efficacy of radiofrequency ablation between patients undergoing mitral valve surgery with and without giant left atria.

Methods

This retrospective, single-center, cohort study investigated patients who underwent mitral valve surgery and concomitant radiofrequency ablation from 2009 to 2019. Patients were divided into non-giant left atria (diameter ≤65 mm, n=1,543) and giant left atria (diameter >65 mm, n=241) groups. Five-year freedom from atrial tachyarrhythmia recurrence and thromboembolic event rates were assessed with death as the competing risk factor with and without propensity-score matching.

Results

Patients with giant left atria had higher mortality (10.8% versus 6.2%, P=0.008) and readmission rates for heart failure than those without (12.0% versus 6.8%, P=0.004). Atrial tachyarrhythmia recurrence rates were higher in patients with giant left atria than those without (49% versus 24% at 5 years, P<0.001), but the cumulative incidence of thromboembolic events before (P=0.944) and after (P=0.695) propensity-score matching were comparable.

Conclusions

Radiofrequency ablation effectively prevented thromboembolic events in patients with giant left atria, despite significant atrial tachyarrhythmia recurrence. Atrial tachyarrhythmia recurrence did not increase the risk of thromboembolic events. A lower success rate should be considered when deciding whether to perform surgical ablation in patients with giant left atria.

giant left atrium

radiofrequency ablation

outcome

competing risk

thromboembolic events

Atrial fibrillation (AF) is the most common type of arrhythmia in clinical practice, affecting an estimated 2.8% of the general population and 10% of patients undergoing cardiac surgery.¹ Radiofrequency ablation (RFA) has been shown to reduce the burden of AF during follow-up when performed concomitantly with other indicated cardiac surgeries, especially mitral valve (MV) surgery.²

Increased left atrium (LA) size has been established as a significant risk factor for treatment failure of AF after a maze procedure. LA size itself may also influence the maintenance of sinus rhythm (SR).^3,4 Specifically, treatment guidelines and expert consensus suggest that patients with a giant LA (GLA, LA diameter [LAD]>65 mm) have significantly increased recurrence rates of AF after catheter ablation.^5,6 However, there is no clear consensus regarding surgical ablation on the LAD line. Although several studies suggest that LAD>65 mm is an independent risk factor for AF recurrence after surgical ablation, Ad et al.⁷ maintained that surgical ablation was an effective treatment method in patients with large LA, who had acceptable SR maintenance rates when compared with those of a small LA group. However, via multivariate logistic regression, Baek et al.⁸ found that a LAD>65 mm is an independent risk factor for long-term AF recurrence after surgical ablation. Furthermore, the credibility of the results was questioned due to the limited sample size, and the possibility of interference of several confounding factors. Moreover, few studies have directly compared long-term thromboembolic event risk in GLA and non-GLA (NGLA) patients.

Therefore, this retrospective cohort study aimed to evaluate the long-term effect of RFA in patients undergoing MV surgery with GLA, and compare thromboembolic event risk associated with GLA and NGLA. We present the following article in accordance with the STROBE reporting checklist.

Patient population

From January 2009 to December 2019, 2,124 patients underwent MV surgery and concomitant RFA. Patients undergoing emergency/salvage surgery with previous cardiac or maze surgery or previous incomplete RFA were excluded (n=340). Of those initially screened, 1,784 were available for analysis. These patients were treated through biatrial (n=1483) or left atrial (n=301) lesions. We conducted a left atrial procedure in patients with LAD≤45 mm without tricuspid valve surgery. Subsequently, patients were divided into the following two groups according to LAD at the time of surgery: NGLA (n=1543) and GLA (n=241) groups. All patients underwent conventional echocardiography by professional sonologists at our center preoperatively. Thereafter, anterior and posterior diameters of the LA were obtained. Preoperative characteristics and intraoperative data of the two groups were evaluated and compared.

Surgical methods

All procedures were performed by two experienced surgeons (Dr. Han and Dr. Li) using routine cardiopulmonary bypass with bicaval and aortic cannulation under moderate hypothermia. The procedure was performed using a bipolar ablation system in all patients, and methods were based primarily on prior work by Wang et al.⁹

Follow-up and postoperative care

Patients were followed up at 3, 6, and 12 months, and annually, thereafter. During each follow-up, patients underwent medical history, physical, and electrocardiogram (ECG) or 24-hour Holter monitoring evaluations. During the study, 71% (1265/1784) of the patients underwent 24-hour monitoring during follow-up. According to the consensus statement of the United States Heart Rhythm Society in 2017, recurrence is defined as any attack of AF, atrial flutter (AFL), or atrial tachycardia lasting more than 30 seconds after a 3-month blanking period.

All patients received postoperative antiarrhythmic drugs (AADs) and anticoagulants unless contraindicated. Postoperative atrial tachyarrhythmias (ATAs) unresponsive to AADs were cardioverted before discharge. Patients with persistent bradycardia due to junctional rhythm were closely observed for 7–14 days to allow for sinus node recovery. If symptomatic bradycardia remained, a dual-chamber pacemaker was implanted. AADs were discontinued in patients with normal SR at 2–3 months postoperatively. For patients receiving bioprosthetic valve implantation or repair, warfarin was administered for 3 months if the SR values were stable. Warfarin was continued beyond this duration if AF or atrial flutter persisted. For patients receiving a mechanical valve, warfarin was used continuously. The median follow-up time was 36.0 months [interquartile range: 13.0–48.0]. At 1 and 5 years, 71% (1,223/1,723) and 51% (419/822) of patients were available for follow-up, respectively.

Statistical methods

Continuous variables are expressed as means ± standard deviation or as medians and interquartile ranges (as appropriate). Student’s t-test was used to compare normally distributed continuous variables, whereas the Mann–Whitney U test was used for skewed distributions. Categorical variables were compared using χ^༒ analysis. Composite endpoint survival (freedom from ATA recurrence and death) between subgroups delineated by LAD (≤65 and >65 mm) was reported as a Kaplan–Meier estimate. The probability of being both alive and ATA recurrence-free is equivalent to the probability of experiencing neither competing risk, as described subsequently. ATA recurrence, thromboembolic events (TEs), and readmission due to congestive heart failure were evaluated using competing risk analysis. Death during the follow-up period served as the competing risk, and perioperative variables with a P value <0.1 served as covariates.

Propensity score (PS) matching was conducted, estimated using a logistic model, and groups were matched within a caliper of 0.1 PS standard deviations. Covariates were based on 26 clinical variables including sex; age; body mass index (BMI); mitral disease etiology; MV surgery type; combination with coronary artery bypass grafting, tricuspid valvuloplasty, or aortic valve surgery; history of preoperative pacemaker implantation, chronic lung disease, chronic kidney disease, hypertension, diabetes, smoking, and stroke; New York Heart Association (NYHA) classification >II; left atrial thrombosis; left ventricular ejection fraction; duration and type of AF; cardiopulmonary bypass and cross-clamp time; perioperative application of continuous renal replacement therapy, extracorporeal membrane oxygenation, or intra-aortic balloon pump; operator; and ablation energy and devices.

Data analysis was performed using SPSS version 22 (SPSS, Inc., Chicago, IL, USA) and R 3.6.1 using the cmprsk package (R Foundation for Statistical Computing, Vienna, Austria).

Baseline characteristics

As expected, between-group preoperative demographic differences were observed regarding BMI, AF type, NYHA class III/IV heart failure rate, rheumatic MV disease rate, preoperative pacemaker rate, and LA thrombus (Table 1). Compared with the GLA group, the NGLA group had a significantly lower BMI (23.6±3.1 versus 25.1±3.1 kg/m², P<0.001) and incidence of rheumatic diseases (589/1543 [38.2%] versus 136/241 [56.4%], P<0.001), preoperative pacemaker (24/1543 [1.6%] versus 9/241 [3.7%], P=0.020), and LA thrombus (253/1543 [16.4%] versus 53/241 [22.0%], P=0.032). Patients in the NGLA group had elevated NYHA class III/IV heart failure rates (1227/1543 [79.5%] versus 176/241 [73.0%], P=0.022) and incidence of paroxysmal AF (613/1543 [39.7%] versus 63/241 [26.1%], P<0.001).

Table 1

Baseline characteristics of all patients
Variable	NGLA(1543)	GLA(241)	P value
Age, y, mean (SD)	59.0±10.7	60.4±8.9	0.060
Male sex, n (%)	604 (39.1)	102 (42.3)	0.348
BMI, kg/m², mean (SD)	23.6±3.1	25.1±3.1	<0.001
AF duration, median [IQR]	18.0 [12.0, 24.0]	18.0 [12.0, 24.0]	0.638
Paroxysmal AF, n (%)	613 (39.7)	63 (26.1)	<0.001
LVEF(%), mean (SD)	59.8±7.2	59.7±6.6	0.725
NYHA class III or IV, n (%)	1227(79.5)	176 (73.0)	0.022
Rheumatic disease, n (%)	589(38.2)	136(56.4)	<0.001
Preoperative PM, n (%)	24(1.6)	9(3.7)	0.020
Chronic lung disease, n (%)	66(4.3)	10(4.1)	0.927
Diabetes, n (%)	221(14.3)	38(15.8)	0.554
Hypertension, n (%)	233(15.1)	38(15.8)	0.788
Chronic kidney disease, n (%)	45(2.9)	5(2.1)	0.462
LA thrombus, n (%)	253(16.4)	53(22.0)	0.032
Smoker, n (%)	237 (15.4)	45 (18.7)	0.190
Peripheral vascular disease, n (%))	106(6.9)	15(6.2)	0.711
Previous stroke, n (%)	164(10.6)	26(10.8)	0.940
Bold and italics values indicate those found to be statistically significant. AF, atrial fibrillation; BMI, body mass index; GLA, giant left atria; IQR, interquartile range; LA, left atrium; LVEF, left ventricular ejection fraction; NGLA, non-giant left atria; NYHA, New York Heart Association; PM, pacemaker; SD, Standard deviation.

Perioperative outcomes

Perioperative outcomes of NGLA and GLA cohorts are summarized in Table 2. NGLA patients had longer cardiopulmonary bypass (133.1±46.4 minutes versus 120.7±31.0 minutes, P<0.001) and cross-clamp (96.3±31.2 minutes versus 88.5±27.2 minutes, P <0.001) times, and tended have a larger proportion of mitral valvuloplasty (1084/1543 [70.3%] versus 157/241 [65.1%], P=0.089), and higher incidence of concomitant coronary artery bypass grafting than those with GLA. However, GLA patients had a higher incidence of reoperation from bleeding (27/241 [11.2%] versus 48/1543 [3.1%], P=0.089). Five patients in the GLA group experienced a postoperative cerebrovascular accident compared with 26 (2.1% versus 1.7%, P=0.667) of the NGLA group. Cerebrovascular accident was defined as stroke or other thromboembolism occurring outside the 30-day postoperative period. GLA patients tended to have greater 30-day mortality rates than NGLA patients (8/241 [3.3%] versus 29/1543 [1.9%], P=0.145). The causes of 30-day mortality of the cohorts were similar and included low cardiac output syndrome, septic shock, and multisystem organ failure.

Table 2

Perioperative outcomes
Variable	NGLA(1543)	GLA(241)	P value
CPB time, min, mean (SD)	133.1±46.4	120.7±31.0	<0.001
Cross-clamp time, min, mean (SD)	96.3±31.2	88.5±27.2	<0.001
MVP, n (%)	1084(70.3)	157(65.1)	0.089
+CABG, n (%)	85(5.8)	4(3.0)	0.011
+AV surgery, n (%)	459(28.7)	68(26.2)	0.628
+TVP, n (%)	1261(81.7)	185(76.8)	0.068
Operated by Dr.Han, n (%)	939(60.9)	139(57.7)	0.348
Medtronic devices, n (%)	469(30.4)	61(25.3)	0.108
Biatrial lesions, n (%)	1292(83.7)	193(80.1)	0.158
IABP, n (%)	36(2.3)	5(2.1)	0.803
ECMO, n (%)	2(1.5)	6(2.1)	0.734
CRRT, n (%)	73(4.7)	10(4.1)	0.690
Reoperation for bleeding, n (%)	48 (3.1)	27 (11.2)	<0.001
Permanent pacing, n (%)	10(0.6)	1(0.4)	0.667
Cerebrovascular accident, n (%)	26(1.7)	5(2.1)	0.667
Mediastinitis, n (%)	18(1.2)	2(0.8)	0.644
30-d mortality, n (%)	29(1.9)	8(3.3)	0.145
Bold and italics values indicate those found to be statistically significant. AV, aortic valve; CABG, coronary artery bypass grafting; CPB, cardiopulmonary bypass; CRRT, continuous renal replacement therapy; ECMO, extracorporeal membrane oxygenation; GLA, giant left atria; IABP, intra-aortic balloon pump; MVP, mitral valvuloplasty; NGLA, non-giant left atria; SD, Standard deviation; TVP, tricuspid valvuloplasty.

Late outcomes

The incidence rates of late events are shown in Table 3. There were 26 late deaths in the GLA group compared with 95 (26/241 [10.8%] versus 95/1543 [6.2%], P=0.008) in the NGLA group. GLA patients had a higher incidence of ATA recurrence (94/241 [39.0%] versus 275/1543 [17.89%], P<0.001) and readmission due to congestive heart failure (29/241 [12.0%] versus 105/1543 [6.8%], P=0.004) than NGLA patients. The rates of TE (15/241 [6.2%] versus 83/1543 [5.4%], P=0.592) or reoperation (3/241 [1.2%] versus 24/1543 [1.6%], P=0.713) between the patients with GLA and NGLA did not significantly differ.

Table 3

Late outcomes
Variable	NGLA(1543)	GLA(241)	P value
Late death, n (%)	95(6.2)	26(10.8)	0.008
ATA recurrence, n(%)	275(17.8)	94(39.0)	<0.001
Thromboembolic events, n (%)	83(5.4)	15(6.2)	0.592
Reoperation, n (%)	24(1.6)	3(1.2)	0.713
Admission due to congestive heart failure, n (%)	105(6.8)	29(12.0)	0.004
Bold and italics values indicate those found to be statistically significant. ATA, atrial tachyarrhythmias; GLA, giant left atria; NGLA, non-giant left atria.

Efficacy

At years 1, 2, 3, 4, and 5, the probability of remaining alive and free of ATA recurrence was estimated to be 92%, 82%, 76%, 71%, and 66%, respectively, in the NGLA cohort. The ATA recurrence-free survival was estimated to be 80%, 69%, 59%, 52%, and 43%, respectively, at each timepoint for the GLA cohort. There was significant difference in ATA recurrence-free survival between the two groups, as shown in Figure 1.

Similar results were found when examining the SR maintenance off AADs at 1, 2, 3, 4, and 5 years in the NGLA group, with freedom of 89% (1234/1382), 80% (838/1043), 72% (514/710), 63% (275/438), and 60% (129/216), respectively (Figure 2). In the GLA group, 82% (190/232), 73% (141/192), 68% (100/145), 61% (59/94), and 53% (24/45) of patients were free of ATAs and AADs at the same timepoints. Freedom from ATAs and AADs between the elderly patient and younger groups also significantly differed at postoperative years 1 (P=0.001), 2 (P=0.030), and 5 (P=0.043).

Similarly, the cumulative survival rates significantly differed between GLA and NGLA patients (Figure 3A, P<0.001). At years 1, 2, 3, 4, and 5, the probability of remaining alive was estimated to be 97%, 96%, 93%, 91%, and 89%, respectively, in the NGLA cohort, while the cumulative survival rates were estimated to be 96%, 93%, 89%, 85%, and 82%, respectively, at each timepoint in the GLA cohort.

The estimated incidence of first ATA recurrence at 1, 2, 3, 4, and 5 years for the NGLA patient population was 6%, 14%, 17%, 21%, and 24%, respectively, while the estimated incidence of first ATA recurrence of the GLA group was 16%, 26%, 36%, 41%, and 49% at respective timepoints (Figure 3B, P<0.001). The cumulative incidence of ATA recurrence was significantly higher in the GLA than in the NGLA group (subdistribution hazard ratio [SHR]: 2.286, 95% confidence interval [CI]: 1.816–2.877, P<0.001).

Furthermore, the cumulative incidence of readmission due to congestive heart failure was significantly higher in the GLA group than in the NGLA group (SHR: 1.621, 95% CI 1.071 to 2.454, P=0.022, Figure 3C). However, the cumulative incidence of TE (SHR: 1.020, 95% CI 0.590 to 1.764, P=0.944, Figure 3D) of both groups did not significantly differ.

Propensity score matching

After PS, 448 samples (224 pairs) were retained. Preoperative and perioperative variables of matched groups did not significantly differ (Table 4). However, the mortality rates of the two matched groups differed significantly (P<0.001). The cumulative incidence of ATA recurrence was significantly higher in GLA patients than in NGLA patients (SHR: 4.801, 95% CI: 3.288–7.011, P<0.001), while the risks of TE (SHR: 0.873, 95% CI: 0.442–1.724, P=0.695) and readmission due to congestive heart failure (SHR: 1.116, 95% CI: 0.653–1.907, P=0.688) of the matched groups were comparable. The results are shown in Figure 4.

Table 4

Preoperative and perioperative characteristics of matched sample
Variable	NGLA(224)	GLA(224)	SMD	P value
Age, y, mean (SD)	59.4±10.5	59.4±8.5	.006	0.974
Male sex, n (%)	89 (39.7)	91 (40.6)	.040	0.777
BMI, kg/m2, mean (SD)	24.4±3.1	24.3±3.0	.020	0.823
AF duration, median [IQR]	18.0 [12.0, 24.0]	18.0 [12.0, 24.0]	.004	0.820
Paroxysmal AF, n (%)	78 (34.8)	71 (32.1)	.128	0.263
LVEF(%), mean (SD)	59.8±6.9	60.1±7.4	.008	0.669
NYHA class III or IV, n (%)	169 (75.6)	171 (76.4)	.049	0.748
Rheumatic disease, n (%)	100(44.9)	105(46.9)	.128	0.134
Preoperative PM, n (%)	2(1.2)	3(1.7)	.079	0.773
Chronic lung disease, n (%)	8(3.6)	9(4.3)	.093	0.796
Diabetes, n (%)	33(14.9)	40(17.9)	.128	0.197
Hypertension, n (%)	37(16.9)	39(17.6)	.068	0.854
Chronic kidney disease, n (%)	8(3.9)	7(3.4)	.013	0.853
LA thrombus, n (%)	40(18.1)	42(18.8)	.091	0.811
Smoker, n (%)	29 (13.0)	34 (15.2)	.130	0.225
Peripheral vascular disease, n (%))	15(6.7)	15(6.7)	.000	1.000
Previous stroke, n (%)	29(13.0)	36(16.3)	.186	0.166
CPB time, min, mean (SD)	124.3±37.2	124.4±33.9	.005	0.952
Crossclamp time, min, mean (SD)	91.3±30.7	91.6±28.6	.006	0.883
MVP, n (%)	139(62.1)	140(62.3)	.084	0.943
+CABG, n (%)	9(4.3)	7(3.4)	.076	0.789
+AV surgery, n (%)	58(26.2)	56(25.7)	.030	0.942
+TVP, n (%)	179(80.1)	185(82.6)	.045	0.649
Operated by Dr.Han, n (%)	127(56.7)	128(57.3)	.018	0.527
Medtronic devices, n (%)	66(29.7)	64(28.7)	.046	0.595
Biatrial lesions, n (%)	182(81.3)	184(82.1)	.076	0.700
AF, atrial fibrillation; AV, aortic valve; BMI, body mass index; CABG, coronary artery bypass grafting; CPB, cardiopulmonary bypass; GLA, giant left atria; IQR, interquartile range; LA, left atrium; LVEF, left ventricular ejection fraction; MVP, mitral valvuloplasty; NGLA, non-giant left atria; NYHA, New York Heart Association; PM, pacemaker; SMD, Standard mean deviation.

Subgroup analysis

To investigate the impact of ATA recurrence on the incidence of TE, we conducted a subgroup analysis (Figure 5). For patients aged ≥75 years (SHR: 3.034, 95% CI 1.438 to 6.402, P<0.001) and with diabetes (SHR: 1.728, 95% CI 1.210 to 3.910, P<0.001), ATA recurrence increased the TE risk. Furthermore, we divided the GLA cohort into two groups according to rhythm, as follows: AF/atrial flutter (AFL, n=95) and non-AF/AFL (n=146). The baseline characteristics of the two cohorts are summarized in Table 5. The patients in the AF/AFL group had larger LA size (72.1±4.6 versus 69.5±4.1 mm, P<0.001), and higher rates of rheumatic MV disease (61/95 [64.2%] versus 75/146 [51.4%], P<0.042), diabetes mellitus (30/95 [31.6%] versus 8/146 [5.5%], P<0.012), and previous stroke (17/95 [17.9%] versus 9/146 [6.2%], P<0.004) than the patients in the non-AF/AFL group.

Table 5

Baseline characteristics of GLA group (subgroup analysis)
Variable	Non-AF/AFL(146)	AF/AFL(95)	P value
Age, y, mean (SD)	60.1±9.5	60.7±8.0	0.608
Male sex, n (%)	59 (40.4)	43(45.3)	0.456
BMI, kg/m², mean (SD)	25.5±3.3	24.6±2.6	0.020
AF duration, median [IQR]	18.0 [12.0, 24.0]	18.0 [12.0, 24.0]	0.738
Paroxysmal AF, n (%)	47 (32.2)	16 (16.8)	0.008
LA diameter, mm, mean (SD)	69.5±4.1	72.1±4.6	<0.001
LVEF(%), mean (SD)	60.4±6.2	58.4±7.1	0.026
NYHA class III or IV, n (%)	108(74.0)	67 (70.5)	0.558
Rheumatic disease, n (%)	75(51.4)	61(64.2)	0.042
Preoperative PM, n (%)	6(4.1)	3(3.2)	0.692
Chronic lung disease, n (%)	5(3.4)	5(5.3)	0.484
Diabetes, n (%)	8(5.5)	30(31.6)	0.012
Hypertension, n (%)	26(17.8)	13(13.7)	0.396
Chronic kidney disease, n (%)	3(2.1)	2(2.1)	0.979
LA thrombus, n (%)	36(24.7)	19(20.0)	0.400
Smoker, n (%)	26(17.8)	19(20.0)	0.670
Peripheral vascular disease, n (%))	6(4.1)	8(8.4)	0.162
Previous stroke, n (%)	9(6.2)	17(17.9)	0.004
Bold and italics values indicate those found to be statistically significant. AF, atrial fibrillation; BMI, body mass index; GLA, giant left atria; IQR, interquartile range; LA, left atrium; LVEF, left ventricular ejection fraction; NGLA, non-giant left atria; NYHA, New York Heart Association; PM, pacemaker; SD, Standard deviation.

At years 1, 2, 3, 4, and 5, the probability of remaining alive was estimated to be 96%, 93%, 90%, 87%, and 79%, respectively, in the non-AF/AFL group. While the respective survival rates of the AF/AF cohorts were estimated to be 99%, 94%, 88%, 85%, and 82% (Figure 6A).

The risk of readmission due to congestive heart failure (SHR: 1.612, 95% CI 0.816 to 3.182, P=0.169, Figure 6B) tended to be higher in patients with than in those without AF/AFL recurrence. However, the cumulative incidence of TE was comparable between the two groups (SHR: 1.493, 95% CI 0.543 to 4.105, P=0.438, Figure 6C).

This is a large-sample study that evaluated the outcomes of concomitant RFA in patients undergoing MV surgery. Prior literature suggests that RFA is an effective surgical method for treating AF when accompanied with other surgeries, and does not increase the surgical risk in patients with GLA.^10–13 In our study, we analyzed the follow-up findings of 1,784 patients who underwent MV surgery with ablation. The 5-year freedom from ATA rates and the 5-year survival incidence of the total population were 73% and 88%, respectively, and the effectiveness and safety of ablation were satisfactory. This finding is similar to that previously reported by Kim et al.,¹⁴ who enrolled patients with GLA undergoing MV surgery with concomitant surgical ablation; the 5-year AF recurrence-free survival rate was 68.9%, a value significantly higher than that of patients who did not undergo ablation (P<0.001). However, RFA was less effective in maintaining SR in GLA patients, and the estimated incidence rate of first ATA recurrence at 5 years was 49%. This result is similar to that of a multicenter case-control study conducted by Baek et al.,⁷ in which 170 patients who underwent cryoablation concomitant with MV surgery for AF were followed up, and multivariate analysis showed that LAD >65 mm was an independent risk factor for long-term AF recurrence (odds ratio: 4.18, 95% CI: 1.39–12.62, P=0.011). There is a lack of studies comparing the TE risk between patients with GLA and NGLA. In the context of our study, despite the high rate of AF recurrence, patients with GLA did not have a higher TE risk than those with NGLA.

An enlarged LA is closely associated with AF recurrence post-ablation.¹⁵ AF patients with a LAD >55 mm have significantly higher recurrence rates after catheter ablation than those with a LAD<55 mm.⁵ However, no consensus has been reached regarding the cut-off value for LAD indicative of increased AF recurrence risk after surgical ablation. For example, Feyrer et al.¹⁶ analyzed data from 103 patients (78 with LAD<50 mm and 25 with LAD>50 mm) undergoing surgical ablation, revealing that 67% of those with LAD<50 mm were successfully converted to having SR within 3 months post-ablation, while only 48% with LAD>50 mm were successfully converted. Meanwhile, Vural et al.¹⁷ found that LAD was associated with AF recurrence and that sensitivity and specificity values associated with a LAD cut-off value of 50.5 mm for the maintenance of SR were 85.7% and 70.7%, respectively. In addition, some studies have described the association between a LAD cut-off value of 60 mm and AF recurrence after surgical ablation, confirming that LAD>60 mm is a reasonable predictor of AF recurrence after surgical ablation.^18–20 These studies had some notable limitations. First, the sample size was small. Second, confounding factors with potential impacts on results were not effectively eliminated. Third, the impact of death on recurrence was not considered.

However, our center is a surgical center for valvular AF, and a large quantity of data has been accumulated over the past 10 years, increasing the robustness of our findings. This study is among the first to report 5-year follow-up results in patients undergoing mitral surgery to evaluate the efficacy of RFA and compare the risk of TE in patients with or without GLA. We found that ATA recurrence-free survival at 5 years post-surgery was estimated to be 66% in the NGLA group and 43% in the GLA group (P<0.001); however, the cumulative incidence of TE of both groups was similar when applying before or after PS matching methods. Furthermore, AF or AFL recurrence did not increase the TE risk in patients with GLA in a subgroup analysis. The incidence of TE in the AF/AFL group was comparable to that of the non-AF/AFL group (P=0.627). This may be because the majority of AF/AFL patients received anticoagulants (79.6% versus 22.4%, P<0.001). Meanwhile, closure of left atrial appendage significantly prevented TE among patients with AF, despite the significant recurrence of ATAs in patients with GLA.^21,22 In addition, vector flow mapping (VFM) is an important method, in which blood flow in the LA is assessed.²³ VFM of the LA in some GLA patients post-ablation with AF and SR revealed no significant differences in late left ventricular diastole between these patients and healthy controls (Supplementary figure 1). Therefore, it remains to be investigated whether occlusion of left atrial appendage could produce comparable effect to patients with GLA compared with RFA procedure.

This study had some notable limitations. First, this was a single-center, retrospective study. Second, surgery was performed by experienced surgeons, which may prevent the results from being generalizable to other centers. Moreover, an inherent limitation of the design of this study was the lack of continuous patient monitoring, which might lead to examination intervals and the underestimation of ATA recurrence. For example, some patients did not have 24-hour Holter monitoring and were assessed via 12-lead ECG alone. Lastly, while Holter monitoring facilitates the measurement of ATA recurrence, ATA recurrence does not necessarily capture the clinical burden of AF. The clinical burden of AF was not examined in this study because any documented recurrence >30 seconds was defined as failure.

Concomitant RFA is effective and feasible for the restoration of SR in patients with AF associated with MV diseases. GLA (LAD>65 mm) patients had higher rates of mortality and readmission for heart failure than those with NGLA. Further, the efficacy of RFA was lower in patients with GLA than those with NGLA, with an estimated 49% ATA recurrence-free survival at 5 years, while effectively preventing TE. Additionally, recurrence of AF or AFL did not increase the risk of thromboembolic events. A lower success rate should be considered when deciding whether to perform surgical ablation in GLA patients, and whether occlusion of the left atrial appendage produced comparable effects in these patients.

AAD

antiarrhythmic drugs

ATA

atrial tachyarrhythmias

atrial fibrillation

AFL

atrial flutter

BMI

body mass index

GLA

giant left atria

left atrium

LAD

left atrial diameter

mitral valve

NGLA

non-giant left atria

RFA

radiofrequency ablation procedures

sinus rhythm

thromboembolic events

Ethics approval and consent to participate: This study was approved by Anzhen Hospital ethics committee (Approval No. 2021150X). The requirement for obtaining patient informed consent was waived due to the retrospective nature of the study.

Consent for publication: Not applicable.

Availability of data and materials: The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Competing interest: The authors have no conflicts of interest to declare.

Funding: This study was supported by grants from the National Natural Science Foundation of China (82170311). Professor Jiangang Wang owned the funding, the member of designers of this study.

Authors’ contributions:

Q Y collected the data, summarized the data, performed data analysis and drafted and revised the article. YC Z, and KM L were involved in data statistics and drawing. C Z and YQ L performed follow-up and data collection. Y L and C B revised the article. JG W planned the study and study design, and revised the article. All authors read and approved the final manuscript.

Acknowledgment: Not applicable.

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Editorial decision: Major revision
08 Jul, 2022
Reviewers agreed at journal
13 Jun, 2022
Reviewers invited by journal
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Editor assigned by journal
07 Feb, 2022
First submitted to journal
05 Feb, 2022

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Radiofrequency ablation in patients undergoing mitral valve surgery with or without giant left atria: A retrospective, single-center, cohort study

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Abstract

Background

Methods

Results

Conclusions

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Background

Materials And Methods

Patient population

Surgical methods

Follow-up and postoperative care

Statistical methods

Results

Baseline characteristics

Perioperative outcomes

Late outcomes

Efficacy

Propensity score matching

Subgroup analysis

Discussion

Conclusion

Abbreviations

Declarations

References

Supplementary Files

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