Efficacy and safety of myectomy and radiofrequency septal ablation for treating hypertrophic obstructive cardiomyopathy

Abstract

Background

Novel treatments are needed for patients with severely symptomatic obstructive hypertrophic cardiomyopathy (oHCM). Radiofrequency (RF) septal ablation has emerged as a promising technique for improving the left ventricular outflow tract (LVOT) gradient and alleviating symptoms, potentially achieving outcomes comparable to the gold-standard surgical myectomy.

Objectives

To compare the 1-year efficacy and safety of surgical myectomy with RF septal ablation in patients with oHCM.

Methods

This observational, retrospective cohort study included patients aged≥18 years with oHCM and an LVOT gradient≥50 mm Hg, unresponsive to medical therapy, who underwent surgical myectomy or RF septal ablation between 2012 and 2022.

Results

The mean age was 49.8±14 and 56.9±10.9 years for the myectomy and RF groups, respectively, with the same sex distribution. The proportions of patients in functional class III distributions were 54.5% and 76.1% in the myectomy and RF groups, respectively. The LVOT gradient was 108.6±49.8 and 101.1±40.3 mm Hg for the myectomy and RF groups, respectively. Procedural success, defined as a reduction in the LVOT gradient to <50 mm Hg or an improvement to functional class I or II, showed no significant difference between the groups (HR: −3.5; 95% CI: −20.2 to 13.12; p=0.673). Complications occurred in 57.6% and 4.6% of the patients in the myectomy and RF groups, respectively (p<0.001).

Conclusions

RF septal ablation and surgical myectomy demonstrated similar efficacy in reducing LVOT gradients and improving symptoms. However, RF ablation exhibited a superior safety profile.

Correspondence to Dr Larissa Ventura Ribeiro Bruscky; [email protected]

WHAT IS ALREADY KNOWN ON THIS TOPIC

• Surgical myectomy has long been considered the gold standard treatment for severe symptomatic obstructive hypertrophic cardiomyopathy (oHCM).

• Radiofrequency (RF) septal ablation is a less invasive alternative with the potential to achieve similar reductions in left ventricular outflow tract (LVOT) gradients and symptom improvement.

WHAT THIS STUDY ADDS

• Our single-centre, retrospective cohort study demonstrated that at the 1-year follow-up, RF septal ablation was as effective as surgical myectomy in reducing LVOT gradients and improving symptoms.

HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY

• RF septal ablation is a promising alternative treatment for patients with oHCM who are unresponsive to medical therapy.

• Further multicentre clinical studies and randomised trials are warranted to validate the long-term efficacy and safety of RF septal ablation compared with surgical myectomy.

Introduction

Hypertrophic cardiomyopathy (HCM) is a genetically determined disease characterised by increased left ventricular mass.¹ Approximately 70% of patients with HCM exhibit left ventricular outflow tract (LVOT) obstruction, which is associated with symptoms such as dyspnoea, chest pain and syncope. For patients with obstructive HCM (oHCM) and an LVOT gradient≥50 mm Hg who remain symptomatic despite optimal medical therapy, invasive interventions such as surgical myectomy and alcohol septal ablation (ASA) are considered.²

Myectomy, first described by Morrow and Brockenbrough in 1961, remains the gold-standard surgical treatment for oHCM. This procedure involves transaortic resection of the hypertrophied basal interventricular septum under cardiopulmonary bypass. Experienced centres demonstrate <1% mortality and clinical success rates exceeding 90%.³ However, myectomy may pose increased risks for patients with comorbidities or in centres with limited surgical expertise (<10 surgeries annually). Consequently, less invasive alternatives such as ASA have emerged.⁴

ASA offers lower perioperative morbidity and requires less resource-intensive postoperative care. However, its applicability is limited by anatomical constraints, as up to 20% of patients are unsuitable candidates owing to unfavourable coronary anatomy and unpredictable extent of myocardial damage.⁵

To address these limitations, radiofrequency (RF) septal ablation has emerged as a minimally invasive, alternative, independent of coronary anatomy. Analogous to electrophysiological techniques, RF energy is applied to the endocardial surface of the interventricular septum via a retrograde aortic or anterograde atrial septal approach under echocardiographic guidance.⁶

This study aimed to compare the safety and efficacy of RF septal ablation with those of myectomy in patients with oHCM over 1 year.

Methods

Study overview, objectives and population

This observational, retrospective cohort study based on medical records included patients aged≥18 years with oHCM and LVOT≥50 mm Hg with refractory symptoms despite optimal medical therapy. Patients underwent surgical myectomy or RF septal ablation between 2012 and 2022, with a minimum follow-up of 1 year. We hypothesised that catheter-based septal ablation using electrophysiology and transoesophageal echocardiography would achieve similar outcomes to surgical myectomy. The primary objective was to compare 1-year efficacy, whereas the secondary objective was to assess 1-year safety.

Inclusion and exclusion criteria

Patients with HCM and LVOT obstruction who underwent myectomy or septal ablation were included. Exclusion criteria included patients who underwent combined procedures (such as valve repair/replacement or coronary bypass), prior cardiac surgery, ejection fraction <50% and limited acoustic window.

Description of the RF ablation technique

RF ablation was primarily performed via an aortic retrograde approach under general anaesthesia. Ultrasound guidance was used to perform two femoral venous punctures and one femoral arterial access using 7F introducers. Under transoesophageal echocardiography guidance, the septal aspect of the left ventricle was mapped with the catheter, and multiple RF energy deliveries were administered in the vicinity of the aliasing region. The ablation power was titrated between 60 and 80 watts, with a target temperature of 60°C, and each RF application was maintained for 90–120 s in areas located at least 1 cm away from the His bundle recordings. In instances where the His bundle recordings were in close proximity to the target area, ablation was performed in the nearest safe region. Furthermore, when the target area exhibited hypokinesis along with significant oedema gradients, the ablation was reassessed and subsequently terminated. Consequently, no conduction lesions requiring pacemaker implantation were observed.

Study endpoints

The primary efficacy endpoint was LVOT gradient reduction to <50 mm Hg or an improvement in New York Heart Association (NYHA) functional class (I or II). Secondary endpoints included stroke, acute myocardial infarction, all-cause mortality, renal failure requiring dialysis, transfusion, pacemaker implantation and infection.

Statistical analysis

Descriptive analysis results were presented using graphs and tables. Fisher’s exact test and the Shapiro-Wilk normality test were applied for categorical and numerical variables. Normally distributed variables were analysed using paired t-tests, whereas non-normally distributed variables were analysed using Wilcoxon tests. A significance level of α=5% was considered for all inferential analyses (R Software, Vienna, Austria).

Results

Study population

This study enrolled 81 patients who underwent myectomy (n=33) or RF septal ablation (n=48) between 2012 and 2022. Two patients in the RF septal ablation group were excluded because of a concomitant diagnosis of aortic stenosis requiring invasive valve intervention. Ultimately, 46 patients underwent RF septal ablation.

Table 1 presents the baseline characteristics of the study population. The cohort was predominantly women (70.9%), with a mean age of 49.8 and 56.9 years in the myectomy and RF septal ablation groups, respectively (p=0.018). The myectomy group had a higher proportion of patients in NYHA functional class IV than the RF ablation group (15 of 33 (45.5%) vs 10 of 46 (22.2%); p=0.048). Additionally, the myectomy group had more current or former smokers (14 of 33 (64.6%) vs 15 of 46 (32.6%); p=0.032) and more individuals using amiodarone (11 of 33 (33.3%) vs 10 of 46 (21.7%); p=0.001) than the RF ablation group.

Table 1

Baseline clinical characteristics of patients undergoing myectomy and RF septal ablation

	Myectomy (n=33)	RF septal ablation (n=46)	P value
Age, years	49.8±14	56.9±10.9	0.018
Sex			0.616
Men	11 (33.3%)	12 (58.2%)
Women	22 (66.7%)	34 (73.9%)
Race			0.578
White	26 (78.8%)	31 (67.4%)
Black	3 (9.1%)	7 (15.2%)
Mixed race	4 (12.1%)	8 (17.4%)
NYHA functional class			0.048
III	18 (54.5%)	35 (76.1%)
IV	15 (45.5%)	10 (23.9%)
Family history of HCM			0.05
Yes	5 (15.2%)	10 (21.7%)
No	28 (84.8%)	30 (65.2%)
Ignore	0 (0%)	6 (13%)
Medical history
Hypertension	21 (63.6%)	30 (65.2%)	1
Dyslipidaemia	19 (57.6%)	21 (45.7%)	0.364
Type 2 diabetes	8 (24.2%)	11 (23.9%)	1
Coronary artery disease	4 (12.1%)	7 (15.2%)	0.754
Obesity	12 (36.4%)	20 (43.5%)	0.643
Asthma	2 (6.1%)	2 (4.4%)	1
Smoking/former smoking	14 (64.6%)	15 (32.6%)	0.032
Background HCM therapy
Beta-blocker	31 (93.9%)	45 (97.8%)	0.568
Calcium channel blocker	7 (21.2%)	10 (21.7%)	1
Amiodarone	11 (33.3%)	2 (4.3%)	0.001
Furosemide	8 (24.2%)	9 (19.6%)	0.782
Disopyramide	1 (3%)	3 (6.5%)	0.636
ICD	6 (18.2%)	7 (15.2%)	0.765
ECG cardiac rhythm			0.549
Atrial fibrillation	4 (12.1%)	2 (4.4%)
Sinus rhythm	28 (84.8%)	41 (91.1%)
Pacemaker	1 (3%)	2 (4.4%)
Heart rate, beats per minute	64.6±9.1	64.4±7.7	0.940
Systolic blood pressure, mm Hg	126.8±20.4	126.3±19.6	1
Body mass index, kg/m2	29.4±5.8	30.5±5.9	0.414
Serum NT-proBNP, pg/mL	1.941±1.528	1.980±1.942	0.784
Serum creatinine, mg/dL	0.9±0.3	1.0±0.2	0.238

NT-proBNP: N-terminal pro–B-type natriuretic peptide

HCM, hypertrophic cardiomyopathy; ICD, implantable cardioverter-defibrillator; NYHA, New York Heart Association; RF, radiofrequency.

Table 2 presents echocardiographic data of the myectomy and RF septal ablation groups. None of the groups showed differences in any of the evaluated parameters (paired samples).

Table 2

Baseline echocardiographic characteristics of patients undergoing myectomy and RF septal ablation

	Myectomy (n=33)	RF septal ablation (n=46)	P value
LVEF (%)	67.7±4.9	66.4±3.2	0.180
LVOT (mm Hg)	108.6±49.8	101.1±40.3	0.796
Septum (mm)	19.7±4.6	18.3±3.1	0.267
Diastolic dysfunction			0.083
Grade I	17 (51.5%)	18 (39.2%)
Grade II	9 (27.3%)	19 (41.3%)
Grade III	0 (0%)	0 (0%)
Indeterminate	0 (0%)	9 (19.5%)
Not evaluated	7 (21.2%)	0 (0%)
PASP (mm Hg)	47.9±8.2	46.1±9	0.419
SAM	28 (84.8%)	34 (77.3%)	0.563
Left atrial (mm)	46.9±6.3	47.1±6.9	0.916
Left atrial volume index (mL/m2)	53.3±12.1	56.2±17.4	0.940
Mitral regurgitation			0.149
Absent	0 (0%)	2 (4.4%)
Mild	12 (36.4%)	25 (55.6%)
Moderate	15 (45.5%)	14 (31.1%)
Severe	6 (18.2%)	4 (8.9%)
Aortic regurgitation			0.820
Absent	20 (60.6%)	27 (58.7%)
Mild	13 (39.4%)	19 (41.3%)
Moderate	0 (0%)	0 (0%)
Severe	0 (0%)	0 (0%)
LVEDD (mm)	45.6±6.2	46±4.9	0.747

LVEDD, left ventricular end-diastolic diameter; LVEF, left ventricular ejection fraction; LVOT, left ventricular outflow tract; PASP, pulmonary artery systolic pressure; RF, radiofrequency; SAM, systolic anterior motion of the mitral valve.

Study endpoints

Primary outcome

Efficacy

Procedural success, defined as the reduction of LVOT gradient to <50 mm Hg or an improvement in NYHA functional class to I or II, did not significantly differ between individuals who underwent myectomy and those who underwent RF septal ablation (HR: −3.5; 95% CI: −20.2 to 13.12; p=0.673).

Compared with 85.4% of the group that underwent RF septal ablation, 88.9% of individuals who underwent myectomy achieved an LVOT gradient reduction to <50 mm Hg or an improvement in NYHA functional class to I or II after 1 year (figure 1).

Figure 1. Efficacy and safety of myectomy and radiofrequency (RF) septal ablation for the treatment of hypertrophic obstructive cardiomyopathy. *Efficacy: defined as a reduction in the left ventricular outflow tract to less than 50 mm Hg or an improvement in New York Heart Association functional class to class I or II. **Safety: included the evaluation of the occurrence of symptoms indicative of stroke, acute myocardial infarction, all-cause mortality, acute renal failure requiring dialysis, the need for blood transfusion, the need for pacemaker implantation and skin or bloodstream infections.

Reduction of LVOT gradient

The LVOT gradient decreased from 108.6 mm Hg (± 49.8) to 24.6 mm Hg (± 46.8) in the myectomy group (mean difference of −85.6) and from 101.1 mm Hg (± 40.3) to 43.3 mm Hg (±35.7) in the RF ablation group (mean difference of −58.8; p=0.064). Figures 2 and 3 illustrate the changes in these variables.

Figure 2. Profile plot of left ventricular outflow tract (LVOT) gradient reduction 1 year after myectomy (blue line) and radiofrequency (RF) septal ablation (red line).

Figure 3. Box plot of the difference between postprocedure and preprocedure left ventricular outflow tract (LVOT) gradient in patients undergoing myectomy (left) and radiofrequency (RF) septal ablation (right).

When one component of the primary outcome was analysed separately, the reduction in LVOT gradient to <50 mm Hg was similar in both groups. Compared with 26 of 41 patients (63.4%) in the RF ablation group, 22 of 27 patients (81.5%) in the myectomy group achieved LVOT gradient values below 50 mmHg. The absolute difference between the groups was −18.1% (95% CI: −39.6% to 3.46%), with a p value of 0.098 (figure 4). These results suggest that myectomy and RF septal ablation have similar efficacies in reducing LVOT gradient to <50 mm Hg.

Figure 4. left ventricular outflow tract gradient (LOVTG)<50 mm Hg 1 year after myectomy (left) and radiofrequency (RF) septal ablation (right).

Reduction of dyspnoea by NYHA functional class

Baseline NYHA functional classes in the myectomy group were III (54.55%) and IV (45.45%), progressing after 1 year to NYHA class III in 15.15%, II in 30.3% and I in 39.39% of patients. In contrast, the RF ablation group had baseline NYHA functional classes of III (76.09%) and IV (23.91%), regressing after 1 year to NYHA class IV in 2.17%, III in 17.39%, II in 32.61% and I in 41.3% of patients (figure 5).

Figure 5. New York Heart Association (NYHA) functional class progression in patients undergoing myectomy (left) and radiofrequency (RF) septal ablation (right).

When one component of the primary outcome was analysed separately, the improvement in the NYHA functional class to I or II was similar in both groups. Compared with 34 of 43 patients (79.1%) in the RF ablation group, 23 of the 28 patients (82.1%) in the myectomy group achieved NYHA class I or II. The absolute difference between the groups was −3.1% (95% CI: −22.4% to 16.29%), with a p value of 0.752 (figure 6). These results suggest a similar efficacy between myectomy and RF septal ablation in improving NYHA functional class.

Figure 6. New York Heart Association (NYHA) functional class I or II dyspnoea 1 year after myectomy. RF, radiofrequency.

Secondary outcome

Safety

The secondary outcome of the study was a safety assessment of both procedures by evaluating the incidence of the following adverse events:

• Stroke.

• Acute myocardial infarction.

• All-cause mortality.

• Acute renal failure requiring haemodialysis.

• Ventricular septal defect.

• Need for blood transfusion.

• Need for pacemaker implantation.

• Skin or bloodstream infection.

When analysed collectively, complications occurred in 19 (57.6%) patients in the myectomy group, compared with 3 (6.5%) in the RF septal ablation group (p<0.001), indicating a superior safety profile for RF septal ablation. This difference was influenced by the occurrence of ventricular septal defects in 5 (15.2%) patients, the need for pacemaker implantation in 8 (24.2%) patients, acute renal failure requiring haemodialysis in 5 (15.2%) patients, blood transfusion in 12 (36.4%) patients and bloodstream infections in 6 (18.2%) patients in the myectomy group. In contrast, none of the patients in the RF septal ablation group developed these complications. Table 3 summarises the complications observed in both groups.

Table 3

Postprocedural complications

Variable	Myectomy (n=33)	RF septal ablation (n=46)	P value
Ventricular septal defect	5 (15.2%)	0 (0%)	0.012
Pacemaker	8 (24.2%)	0 (0%)	<0001
All-cause mortality	5 (15.2%)	1 (2.3%)	0.078
Acute myocardial infarction	0 (0%)	1 (2.3%)	0.75
Stroke	2 (6.1%)	0 (0%)	0.18
Haemodialysis	5 (15.2%)	0 (0%)	0.012
Blood transfusion	12 (36.4%)	0 (0%)	<0001
Skin infection	3 (9.1%)	0 (0%)	0.075
Bloodstream infection	6 (18.2%)	0 (0%)	0.005
Any complication	19 (57.6%)	2 (4.6%)	<0001

RF, radiofrequency.

In the RF ablation group, one case of acute myocardial infarction (2.3%) and one death (2.3%) were observed. In contrast, the myectomy group had five deaths (15.2%) (p=0.078) and no cases of acute myocardial infarction (p=0.75), though these differences were insignificant.

Discussion

This study evaluated the efficacy of both procedures using the criteria from the VALOR-HCM study (Assessment of the Efficacy and Safety of Mavacamten in Adults With Symptomatic Obstructive Hypertrophic Cardiomyopathy Who Are Eligible for Septal Reduction Therapy), such as reducing the LVOT gradient to <50 mm Hg or improving dyspnoea to NYHA class I or II.⁷ It was conducted at the Instituto Dante Pazzanese de Cardiologia, compared surgical myectomy and RF ablation in patients with oHCM. Treatment selection was based on procedural availability, ensuring unbiased assessment. All patients had preserved ventricular function, significant LVOT gradients (>100 mm Hg), pulmonary hypertension and left atrial enlargement. Diastolic function data were missing for 21.2% of patients undergoing myectomy because of outdated echocardiographic protocols before the 2016 guideline update.

Patients undergoing RF ablation were older (56.9±10.9 years) than those undergoing myectomy (49.8±14 years, p=0.018), reflecting the increased surgical risks in older populations. A higher proportion of patients who underwent myectomy were NYHA class IV; however, this likely did not influence treatment selection, as all patients were symptomatic (NYHA III or IV).

After 1 year, 88.9% and 85.4% of the patients in the myectomy and RF ablation achieved these outcomes, respectively, with no significant differences between the groups. These results align with the reported myectomy success rates of 90–95%, which were slightly lower in this study, likely because of differences in surgical volumes.^{3 8 9} LVOT gradient reductions were comparable between the groups. Myectomy reduced gradients from 108.6±49.8 to 24.6±46.8 mm Hg, with 63.4% achieving gradients <50 mm Hg. RF ablation reduced gradients from 101.1±40.3 to 43.3±35.7 mmHg, consistent with earlier studies from the same centre.⁶ Previous meta-analyses have reported gradient reductions of up to 97.6 mm Hg, supporting the effectiveness of RF ablation.¹⁰

Symptomatic relief was also similar between the groups. In this study, 82.1% and 79.1% of patients in the myectomy and RF ablation group achieved NYHA class I or II, respectively, with no significant difference (p=0.752). These findings are consistent with those of previous studies reporting >90% NYHA class improvement after myectomy.^{9 11} Studies have reported that the proportion of patients with NYHA functional class III/IV decreased from 51% to none.¹²

Safety outcomes are critical when comparing therapies. The mortality rate for the myectomy group was 15.2% (five cases), which was significantly higher than the <1% reported in high-volume centres.¹³ This discrepancy may be attributed to the small sample size, case complexity and patient selection at this tertiary care centre. Conversely, RF ablation had a mortality rate of 2.3%, comparable to the 2.2% reported in the literature.¹⁴ The complication rate for myectomy exceeded expectations for specialised centres, likely reflecting disease severity and procedural challenges in this cohort.

A Brazilian study of 12 patients undergoing RF septal ablation reported significant LVOT gradient reductions (96.8±34.7–36.1±23.8 mm Hg, p=0.0001) after 1 year, with no major complications.⁶ A US study demonstrated that 10 of 11 patients achieved an 85% reduction in resting and provoked LVOT gradients, with marked NYHA functional class improvement.¹⁵ These findings support RF ablation as a potential alternative to myectomy, warranting direct comparisons of their safety and efficacy.

This observational study has inherent limitations. Its design and small sample size limit the ability to perform robust multivariate analyses and increase the risk for residual confounding. Additionally, the study cohort consisted predominantly of Caucasian patients treated in high-volume HCM centres, limiting generalisability to other populations or lower-volume centres. Future randomised prospective trials are required to confirm the equivalence of these methods.

In patients with highly symptomatic oHCM meeting guideline criteria for septal reduction therapy, RF ablation was as effective as gold-standard myectomy in reducing the LVOT gradient and improving NYHA functional class to I or II, with RF ablation being the safer option.

Competency in patient care and procedural skills

In patients with symptomatic oHCM, myectomy was as effective as RF ablation in reducing the LVOT gradient and improving NYHA functional class to I or II.

We would like to express our gratitude to the Department of Cardiomyopathies at the Dante Pazzanese Institute of Cardiology for their exceptional medical services and valuable contributions to the research. We also thank the hospital administration and medical teams for their collaborative work in supporting patients, conducting examinations and analysing clinical cases. Special thanks go to the patients for their trust, which enabled the continuous improvement of care. Finally, we thank our families for their unwavering support and understanding throughout this journey; their encouragement was essential for completing this work.

Data availability statement

Data may be obtained from a third party and are not publicly available. No data are available.

Ethics statements

Patient consent for publication

Not applicable.

Ethics approval

Collected data were used solely for this study, and patient anonymity was preserved. This study involves human participants and was approved by ethics committee of the Instituto Dante Pazzanese de Cardiologia (CAAE: 57364322.3.0000.5462, opinion number: 5.395.718) on 9 May 2022. Project presentation: In the CEP Protocol: 5246. Participants gave informed consent to participate in the study before taking part.

Footnote

Contributors All the authors contributed equally to the conception, design, data collection, analysis, interpretation of the study and drafting of the manuscript. All authors played an integral role in ensuring the quality and integrity of this study. All the authors have reviewed and approved the final manuscript for submission. LVRB is the guarantor.

Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

Competing interests None declared.

Provenance and peer review Part of a topic collection; Not commissioned; externally peer-reviewed.

Author note Diversity information: This study was conducted in Brazil, a developing nation, at a public hospital that relies on government funding. The lead author, a young woman, underscores the significance of diversity in scientific leadership. Furthermore, the author team was deliberately composed of equally representative men and women, demonstrating our commitment to promote gender equality and inclusivity in the pursuit of clinically impactful research.

References

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