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Cardiology Research

Short Communication

Volume 14, Number 5, October 2023, pages 403-408

Outcomes After Supraventricular Tachycardia Ablation in Patients With Group 1 Pulmonary Hypertension

Pulmonary hypertension (PH) is associated with right ventricular pressure overload [1]. This can lead to atrial remodeling, increasing the risk of supraventricular tachycardias (SVTs) [2, 3]. Catheter ablation safely and effectively treats SVT in the general population [4]. Patients with group 1 PH have structural abnormalities that may make SVT ablation more technically challenging and increase the risk of arrhythmia recurrence. Prior studies of SVT ablation outcomes in PH patients have either included all World Health Organization (WHO) PH classes or excluded some SVT types [5-7]. This study aimed to address incompletely characterized SVT ablation outcomes specifically in patients with group 1 PH.

Following institutional review board approval, we performed a retrospective study of patients with group 1 PH who underwent SVT ablation between January 1, 2012 and December 31, 2022 at University of Texas Southwestern Medical Center. Relevant cases were identified by searching for patients with a diagnosis code for PH and a prescription for group 1 PH-specific therapies (epoprostenol, treprostinil, selexipag, ambrisentan, bosentan, macitentan, riociguat, sildenafil, and tadalafil) who underwent cardiac ablation for atrial fibrillation (AF), atrial flutter (AFL), atrial tachycardia (AT), or atrioventricular nodal reentrant tachycardia (AVNRT). Chart review was performed to confirm eligibility and abstract baseline data (medications, exercise tolerance and WHO functional status, transthoracic echocardiogram (TTE)/cardiac magnetic resonance imaging (cMRI)/right heart catheterization (RHC) results). Only the most recent data within 1 year of the index procedure were recorded. Diagnosis date was defined as the date of the first RHC demonstrating PH (mean pulmonary artery pressure > 20 mm Hg) or via an explicitly stated date in clinic notes, whichever was earlier. Cardiac indices were measured via thermodilution when possible and via the Fick method otherwise. Clinic and procedure notes were searched to determine the course of the index procedure and recurrences at 3 months and 1 year. Recurrence was determined by any mention of recurrent tachycardia symptoms and a cardiologist-confirmed electrocardiogram demonstrating an arrhythmia pattern ablated in the index procedure. If multiple arrhythmias of one type were initially ablated (e.g., multiple AFL foci) and no repeat ablation was performed to identify the recurrent focus, all foci were assumed to have recurred. If a repeat ablation occurred, only the demonstrated arrhythmias were documented as recurrent. Mann-Whitney U-tests and Fisher’s exact tests with an alpha of < 0.05 were performed as appropriate to investigate differences between patients with and without recurrence. Logistic regression was performed to investigate whether attempting to ablate any specific SVT was associated with post-procedural decompensation, defined as the need for pressor support to maintain mean arterial pressures > 65 mm Hg and transfer to intensive care unit (ICU).

Ethics approval and informed consent waiver were obtained from institutional IRB.

Thirty-eight patients (male: 17 (44.7%); female: 21 (55.3%)) of age 53.7 ± 13.7 years with group 1 PH were included. Baseline characteristics are presented in Table 1; while all patients were classified as group 1 PH, significant pulmonary or cardiovascular comorbidities were present in nine (23.7%) patients, including three patients with a wedge pressure > 15 mm Hg. Index ablations were attempted for 60 arrhythmias (5 AF; 8.3%, 36 AFL; 60%, 15 AT; 25%, 4 AVNRT; 6.7%). A summary of initial success rates and outcomes stratified by ablation location is provided in Table 2. All AT ablation targets with recorded locations were in the right atrium. Of five atypical AFL ablation targets, one was in the right atrium and four were in the left atrium; all noted AFL recurrences were of left atrial targets. Of 14 failed initial ablations, nine (64.3%) failed due to an inability to sustain the arrhythmia for sufficient time to map and ablate, two (14.3%) failed due to hemodynamic instability forcing procedure termination, two (14.3%) failed due to patient intolerance of the procedure length, and one (7.1%) failed due to unknown reasons. One recurrent typical flutter was successfully re-ablated at 3 months; this flutter recurred again at 1 year and no re-ablation was attempted. Two recurrent typical flutters were successfully re-ablated at 1 year. No repeat AF or AT ablations were attempted.

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Table 1. Baseline Patient Characteristics Stratified by Presence of Any Recurrence of an Initially Ablated Arrhythmia During Maximum Available Follow-Up Time

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Table 2. Initial Success Rates and Outcomes of Attempted Ablations Stratified by Arrhythmia Type

No baseline patient characteristics were significantly associated with recurrence. There was a trend towards lower left ventricular ejection fractions and higher pulmonary capillary wedge pressures in patients experiencing recurrent arrhythmias which did not reach statistical significance. Fifteen (39.5%) procedures were performed using general anesthesia; 23 (60.5%) were performed using anesthesia-monitored moderate sedation. There was one (2.6%) peri-procedural death secondary to acute mixed respiratory failure triggered by procedural moderate sedation for ablation of AF. There were seven (18.4%) post-procedural decompensations requiring initiation of pressors and transfer to the medical ICU, including three (42.9%) patients receiving moderate sedation and four (57.1%) patients receiving GA (P = 0.40). In all but one patient, pressors were weaned off in less than 48 h. Post-procedural decompensations were noted in five (18.5%) index procedures involving typical AFL ablation, two (22.2%) index procedures involving AT ablation, and two (50%) index procedures involving AVNRT ablation. No index procedure involving AF or atypical AFL ablation resulted in post-procedural decompensation. None of the included SVT ablation types were significantly associated with post-procedural decompensation in a logistic regression model.

Retrospective studies in patients with group 1 PH have associated untreated SVTs with right ventricular failure, declines in exercise capacity, diuretic-resistant volume overload, and excess mortality [8]. These studies also suggest that restoration of sinus rhythm can reverse SVT-associated clinical declines.

Despite the known benefits of rhythm control in PH, pharmacologic rhythm control was infrequently used in our population, reflecting the particularly challenging nature of anti-arrhythmic drug use in these patients with severe structural heart disease and precarious hemodynamics [8]. Current European Society of Cardiology (ESC) guidelines on the management of SVTs specifically recommend against the use of flecainide and propafenone in patients with structural heart disease, note numerous cardiac and extracardiac side effects of amiodarone (some of which strongly affect patients with PH, e.g., negative inotropic side effects, drug-drug interactions, and long-term toxicity), and urge caution regarding excess mortality produced by the pro-arrhythmic effects of several anti-arrhythmic drugs (e.g., class 1A agents, sotalol) [9, 10]. With pharmacologic therapy limited by toxicity, definitive rhythm control via catheter ablation is an attractive option.

Registry studies of SVT ablations in the general population have demonstrated procedural death and complication rates of < 1% [11, 12]. By contrast, in this high-risk population, procedural mortality was 2.6%, and 18.4% of patients required pressor support and intensive care peri-procedurally. This is unsurprising given the severity of PH in our population as demonstrated by markedly elevated pulmonary pressures and evidence of right heart failure on cardiac imaging in a majority of patients. Additionally, these outcomes are in line with anesthesia outcomes in PH in general [13]. The relatively high post-procedural ICU admission rate, while a concern, is in part intentional, as our institutional protocols recommend a very low threshold for the initiation of pressors or pressor-inotropes during anesthesia in PH so as to reduce risk of more severe decompensation. Despite these measures, one periprocedural death occurred, highlighting the careful risk/benefit considerations required in this population [14]. The ablation success rates and outcomes reported in this study will help inform future clinical decision making and studies in this unique group.

Prior large studies of SVT ablations in the general population have reported high initial success rates of 93.1-96.4% for AF, 96.0-98.3% for typical AFL, 79-90% for atypical AFL, 98.9-99.8% for AVNRT, and 84.3-93.6% for AT [11, 12, 15-18]. Lower initial success rates for all arrhythmia types were observed in this study; atypical AFL and AT were particularly difficult to ablate successfully. A combined 28.6% of procedures failed due to either hemodynamic instability forcing termination or patient intolerance of extended procedure length, reflecting the underlying clinical fragility of patients with PH.

Studies of SVT ablations in the general population have shown long-term (i.e., average follow-up of 12 months or greater) recurrence rates of 29.8-45.6% for AF, 10.9-30% for typical AFL, 23-27% for atypical AFL, 22-32.3% for AT, and 3.9-4.5% for AVNRT [15, 18-23]. This study demonstrated qualitatively comparable recurrence rates for typical AFL and AT and higher rates for atypical AFL and AF. AF ablation in particular exhibited a 100% recurrence rate at 1 year, indicating that the long-term utility of AF ablation must be very carefully considered in this population. Given the small sample size (n = 4 with AF), further study is also needed to better assess recurrence rates. There was a trend towards higher pulmonary capillary wedge pressures and lower left ventricular ejection fractions being associated with recurrence, possibly indicating that patients with concomitant group 1 PH and left-sided heart failure are at especially high risk of recurrence. However, these results should be interpreted with caution as our analysis was not adjusted for multiple comparisons. Despite high recurrence rates overall, few repeat ablations were performed, possibly due to concerns about safety of additional ablations, concerns for recurrence despite repeat ablation, and concerns for competing risks limiting the benefit of repeat ablation.

Limitations of the study include its small sample size, clinical heterogeneity (reflecting the rarity of group 1 PH patients), and long duration of inclusion. Risk/benefit and overall outcomes may differ based on both patient and institutional factors, and we would recommend caution in the management of these high-risk patients.

Overall, this study demonstrates that SVT ablation in group 1 PH can be performed with moderate risk of peri-procedural morbidity and mortality. Compared to the general population, initial success rates are lower across all SVTs and 1-year recurrence rates are higher for some SVTs. Clearer determination of what risk factors (e.g., higher pulmonary artery/right atrial pressures, more severe right ventricular failure, or larger right atrial sizes) produce higher individual risk of recurrence will require larger multicenter studies.

Acknowledgments

None to declare.

Financial Disclosure

None to declare.

Conflict of Interest

None to declare.

Informed Consent

Informed consent waiver was obtained from institutional IRB.

Author Contributions

Study design: TS, KC, NP; data collection: TS; data analysis: TS; manuscript preparation and review: TS, KC, NP.

Data Availability

The data supporting the findings of this study are available from the corresponding author upon reasonable request.

Abbreviations

SVT: supraventricular tachycardia; PH: pulmonary hypertension; WHO: World Health Organization; AF: atrial fibrillation; AFL: atrial flutter; AT: atrial tachycardia; AVNRT: atrioventricular nodal reentrant tachycardia; TTE: transthoracic echocardiogram; cMRI: cardiac magnetic resonance imaging; RHC: right heart catheterization

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