Left ventricular flow components and myocardial deformation following treatment for hypertrophic obstructive cardiomyopathy: a retrospective cardiac magnetic resonance-based cohort of mavacamten vs. septal myectomy

Introduction

Hypertrophic obstructive cardiomyopathy (HOCM) is a cardiomyopathy most commonly caused by pathogenic variants in sarcomere protein genes. It is characterized by asymmetric septal hypertrophy leading to left ventricular outflow tract (LVOT) obstruction (1). Its core pathophysiological elements include diastolic dysfunction, LVOT obstruction, and consequent abnormal intracavitary hemodynamics. These factors collectively increase the risk of heart failure and sudden cardiac death (1,2). In previous treatment strategies, septal myectomy has been a crucial intervention for symptomatic, drug-refractory HOCM, aimed at relieving symptoms and preventing complications (3-5). Meanwhile, emerging targeted drug therapies, such as mavacamten [a cardiac myosin inhibitor (CMI)], reduce the need for septal reduction therapy and consistently improve LVOT pressure gradients and symptoms (6,7). With the gradual adoption of new medications, given the significant differences between these two therapies in terms of invasiveness, cost, accessibility, and risk-benefit profile (8,9), a direct, in-depth, and multi-dimensional comparison of their treatment effects is essential for guiding personalized clinical decision-making.

In healthy individuals, myocardial cells within the ventricular walls are arranged in an ordered, laminar fashion along different directions, enveloping the ventricles. This unique architecture allows the various muscle fiber layers to interact in a highly coordinated manner, generating synergistic contraction that produces the left ventricular (LV) hemodynamics necessary to maintain effective circulation (10). Cardiac magnetic resonance (CMR) imaging, as a non-invasive, high-resolution examination method, can simultaneously assess the myocardial detailed structure, function, and intraventricular hemodynamics (11). On one hand, CMR feature tracking (CMR-FT) analysis can non-invasively and quantitatively evaluate myocardial deformation in different spatial directions, which cannot be distinguished by LV ejection fraction (LVEF) alone. Particularly, the subtle changes in global longitudinal strain (GLS) in HOCM patients after pharmacotherapy or surgery reveal the treatment-induced improvements in myocardial mechanical function, and its prognostic value has been established in hypertrophic cardiomyopathy (HCM) (12,13). On the other hand, four-dimensional flow (4D-flow) technology enables a comprehensive assessment of intraventricular hemodynamics. This imaging technique can semi-automatically provide three-dimensional quantification of the inflow and outflow proportions within the LV cavity at different time points in the cardiac cycle. Furthermore, growing evidence supports the role of 4D-flow CMR in detecting subtle hemodynamic abnormalities across various cardiovascular diseases (14-16).

Therefore, CMR-FT and 4D-flow CMR constitute an imaging framework for evaluating HOCM treatment efficacy from the two dimensions of myocardial deformation and hemodynamics, respectively. To date, no studies have compared myocardial deformation function and ventricular hemodynamics via CMR in HOCM patients treated with mavacamten vs. septal myectomy. This study aims to integratively apply these two technologies to systematically compare the differential effects of mavacamten and septal myectomy on improving myocardial deformation and LV flow components. The goal is to provide a more comprehensive and in-depth evidence base for optimizing clinical treatment strategies. We present this article in accordance with the STROBE reporting checklist (available at https://cdt.amegroups.com/article/view/10.21037/cdt-2025-aw-547/rc).

Methods

Study population

This retrospective cohort study reviewed CMR images from HOCM patients who received either mavacamten treatment or underwent septal myectomy at Guangdong Provincial People’s Hospital between February 2021 and May 2023. CMR was performed before treatment and at the 30-week timepoint (during continued medication or post-operation). Additionally, 10 healthy volunteers with no history of heart disease or cardiovascular risk factors were included. Although the HOCM patients treated with mavacamten were participants in the multicenter mavacamten trial project (NCT05174416) involving the Department of Cardiology at Guangdong Provincial People’s Hospital, it is important to note that this study constitutes an entirely new retrospective comparative analysis and is not a prespecified subgroup analysis of the prospective clinical trial.

The inclusion criteria for HOCM patients were: (I) meeting the clinical diagnostic criteria for HOCM established by the American Heart Association (17); (II) LVEF ≥50% (mavacamten group: LVEF ≥55%; myectomy group: LVEF ≥50%); (III) age ≥18 years; (IV) patients completed septal myectomy or started mavacamten within 3 months after CMR examination; and (V) underwent CMR at baseline, after septal myectomy, or after 30 weeks of continuous mavacamten use. Exclusion criteria were: (I) comorbid cardiac diseases such as coronary artery disease or valvular heart disease; (II) invasive cardiac treatments during follow-up or prior to the study; (III) 4D-flow image quality insufficient for analysis; (IV) observation of LV dysfunction (LVEF <50%) requiring discontinuation of treatment within 30 weeks of starting treatment in the mavacamten group; and (V) explicitly declined to sign the informed consent form for this study (as shown in Figure 1). Baseline information, including demographic characteristics, medication use, and comorbidities, was extracted from electronic medical records. This study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. It was approved by the Ethics Committee of Guangdong Provincial People’s Hospital (ethical approval No. KY2024-1100-01, approval date: January 7, 2025), and all subjects provided written informed consent.

Figure 1 Flowchart of study participant recruitment. 4D-flow, four-dimensional flow; HOCM, hypertrophic obstructive cardiomyopathy; MRI, magnetic resonance imaging.

CMR protocol

This study utilized a 3.0 T magnetic resonance scanner (Ingenia, Philips Healthcare, Best, the Netherlands) with a 32-channel cardiac coil for CMR image acquisition. Electrocardiographic triggering and respiratory gating were routinely applied. For cine imaging, a stack of short-axis planes from the apex to the base, along with long-axis planes (two-, three-, and four-chamber views), was collected using a single-shot balanced standard steady-state free-precession (bSSFP) sequence. The parameters of cine imaging were as follows: field of view (FOV), 240×240 mm²; voxels, 1.5×1.5×8 mm³; repetition time (TR)/echo time (TE), shortest/shortest; sense factor, 1.8; minimum inversion time, 105 ms; and flip angle, 45°. The 4D-flow scan was performed using retrospective ECG gating and respiratory gating while the subjects were at rest and breathing freely. To obtain ideal, homogeneous data, subjects were instructed to maintain even breathing with minimal and consistent abdominal movement and a stable respiratory rate before scan positioning. The scanning parameters were as follows: velocity encoding (VENC) 130–200 cm/s; TR 3.8 ms; TE 2.1 ms; voxel size 3×3×3 mm³; flip angle 7–15°; 25–30 reconstructed cardiac phases. The scan time was approximately 8–12 minutes.

CMR imaging analysis

All CMR analyses were performed using commercially available software CVI42 (version 5.13.5, Canada Circle Cardiovascular, Calgary, AB, Canada). The images were analyzed by two experienced radiologists who were blinded to all clinical information of the patients, including the specific interventions received (i.e., mavacamten therapy or septal myectomy). The endocardial and epicardial contours of the left ventricle were automatically outlined from the base to the apex on the short-axis planes. The LV maximum wall thickness (LVMWT) was manually measured. The LV end-diastolic volume (LVEDV), LV end-systolic volume (LVESV), stroke volume (SV), cardiac output (CO), LVEF, and LV mass were obtained by tracing the end-diastole and end-systole circles. LV mass, LVEDV, and LVESV were indexed to body surface area.

CMR tissue tracking analysis

CMR tissue tracking analysis was performed in the FT module. The endocardial and epicardial LV borders at end diastole were semiautomatically delineated with manual adjustment on cine images. The contours were automatically tracked throughout the cardiac cycle and manually corrected to ensure accurate boundary tracking. The strains were computed at each myocardial point, covering the whole myocardium on each section. The number of myocardial points corresponds to that of pixels between the endocardial and epicardial contours. The global peak systolic strain for the LV in all three directions was obtained by averaging the values from the myocardial points (Figure 2).

Figure 2 FT strain and 4D-flow components. FT with LV strain overlay on cine SSFP image and blood flow pathline visualization of the four flow components throughout the cardiac cycle for a 78-year-old woman with HOCM: DF (green), RIF (yellow), DEF (blue), and RV (red). 4D-flow, four-dimensional flow; DEF, delayed ejection flow; DF, direct flow; FT, feature tracking; HOCM, hypertrophic obstructive cardiomyopathy; LV, left ventricular; RIF, retained inflow; RV, residual volume; SSFP, steady-state free precession.

Analysis of LV flow components

Analysis was performed using a method previously validated by Eriksson (18). Briefly, the software identified the mitral and aortic valve positions on the three-chamber cine sequence to define the boundaries for estimating LV flow parameters. After confirming the valve positions, the software options were selected to match them to the segmented geometric model, with manual adjustments made to the position and size of the mitral and aortic valves when necessary to achieve automatic image registration between the cine and velocity magnitude images. Pathlines were emitted from the center of each voxel and tracked both forward and backward to cover systole and diastole. The ventricular blood particles were automatically separated by the pathlines into four distinct blood flow components, including (I) direct flow (DF): blood that enters the LV during diastole and leaves during systole within the same cardiac cycle; (II) retained inflow (RIF): blood that enters the LV during diastole but is not ejected during systole within the same cardiac cycle; (III) delayed ejection flow (DEF): blood that is already in the LV at the beginning of diastole and is ejected during systole; and (IV) residual volume (RV): blood that remains within the LV for at least two consecutive cardiac cycles (19,20) (Figure 2). A more detailed description is provided in Appendix 1.

Cardiac surgery

In this study, patients with HOCM who underwent septal myectomy all received the modified extended Morrow procedure (17). All operations were performed by experienced cardiac surgeons who performed the procedures each have over 10 years of experience in cardiac surgery, with a personal case volume exceeding 40 septal myectomies. As a regional HCM diagnosis and treatment center, Guangdong Provincial People’s Hospital has performed an average of approximately 30 septal myectomy procedures per year over the past 5 years. The detailed surgical procedure was described in Appendix 1, and detailed surgical data for all HOCM patients are documented in Table S1. In the myectomy group of this study, no severe adverse events such as postoperative complications, including complete atrioventricular block, pacemaker implantation, or surgery-related mortality, were observed.

Statistical analysis

CMR data before and after treatment were statistically analyzed using SPSS software (version 25.0; SPSS Inc., Armonk, NY, USA). Continuous, normally distributed data are expressed as mean ± standard deviation (SD), while non-normally distributed variables are expressed as median [first quartile (Q1), third quartile (Q3)]. Categorical variables are presented as percentages and were compared using Fisher’s exact test. Changes in various CMR parameters from baseline are presented in figures as mean values with corresponding 95% confidence intervals (CIs).

For within-group differences in the surgical group and the mavacamten group: if the differences were normally distributed, paired t-tests were used to compare parameters at baseline and follow-up CMR; otherwise, the paired Wilcoxon signed-rank test was used. For between-group differences comparing the myectomy group and the mavacamten group: if the differences were normally distributed, independent samples t-tests were used; otherwise, the Mann-Whitney U test was used. For comparing differences among the myectomy group patients, the mavacamten group patients, and healthy volunteers: one-way analysis of variance (ANOVA) with Tukey’s post-hoc test was applied.

To assess the reproducibility of LV global strain and flow component measurements, blinded readers analyzed 15 randomized CMR images (including 5 healthy controls, 5 HOCM patients at baseline, and 5 HOCM patients at 30 weeks). Intra- and inter-observer reproducibility was evaluated by the intraclass correlation coefficient (ICC) analysis, calculated using a two-way random-effects model for absolute agreement. All P values <0.05 were considered statistically significant.

Results

Participant characteristics

Finally, a total of 56 subjects were initially identified. After applying the inclusion and exclusion criteria, 30 subjects were finally enrolled for analysis. They were divided into three groups: 10 HOCM patients treated with mavacamten, 10 HOCM patients who underwent septal myectomy, and 10 healthy volunteers without a history of heart disease or cardiovascular risk factors (as shown in Figure 1). The specific reasons for exclusion during screening were as follows: (I) comorbid coronary artery disease (myectomy group: n=6); (II) invasive cardiac treatments during follow-up or prior to the study (myectomy group: n=4); (III) 4D-flow image quality insufficient for analysis (myectomy group: n=6; mavacamten group: n=2); (IV) observation of LV dysfunction (LVEF <50%) requiring discontinuation of treatment within 30 weeks of starting treatment in the mavacamten group (n=0); and (V) explicitly declined to sign the informed consent form for this study (myectomy group: n=3).

There were no statistically significant differences among the three groups in terms of age, sex distribution, or body surface area (P≥0.05). Furthermore, HOCM patients in the mavacamten group and the myectomy group were comparable regarding prior use of beta-blockers, non-dihydropyridine calcium channel blockers, statins, and laboratory cardiac biomarkers (P≥0.05) (Table 1). Additionally, 80% HOCM patients in the myectomy group underwent concomitant mitral apparatus management along with septal myectomy (Table S1).

LV structure, function, myocardial deformation, and LV flow components at baseline

At baseline, LVMWT, LV mass index (LVMI), LVEF, global LV strain, and LV flow components were all similar between the myectomy group and the mavacamten group (P≥0.05). However, compared to the healthy control group, both HOCM patient groups had significantly lower DF and higher RV (all P<0.001), as shown in Table 2.

Outcomes after treatment

As shown in Tables 2,3 and Table S2, at the 30-week follow-up, both the myectomy group and the mavacamten group showed significant improvements in LV structure, function, myocardial deformation, and LV flow components.

LV structure and function

At week 30, both the mavacamten group and the myectomy group showed a reduction in LVMWT, LVMI, and LVEF compared to baseline: LVMWT: 25.10±6.40 vs. 20.90±5.30 mm, P=0.001 (mavacamten); 22.90±4.36 vs. 19.70±4.42 mm, P=0.006 (myectomy); LVMI: 113.30±43.13 vs. 89.40±34.91 g/m², P<0.001 (mavacamten); 92.83±29.69 vs. 74.61±26.22 g/m², P<0.001 (myectomy); LVEF: 69.9%±3.14% vs. 64.6%±2.07%, P<0.001 (mavacamten); 66.75%±3.26% vs. 63.58%±3.65%, P=0.006 (myectomy).

It is noteworthy that the magnitude of reduction from baseline to 30 weeks in LVMWT, LVMI, and LVEF was not statistically different between the two HOCM patient groups (mavacamten vs. myectomy): LVMWT: −4.2±2.78 vs. −3.2±2.86 mm, mean between-group difference: 1.00 mm (95% CI: −1.65 to 3.65), P=0.44; LVMI: −24.00±13.78 vs. −17.66±10.91 g/m², mean between-group difference: 6.28 g/m² (95% CI: −3.97 to 16.53), P=0.21; LVEF: −5.30%±2.31% vs. −3.17%±2.79%, mean between-group difference: 2.13% (95% CI: −0.28% to 4.54%), P=0.08. At 30 weeks, LVEF remained within the normal range in both the mavacamten and myectomy groups.

Furthermore, LVOT gradient decreased significantly from baseline to 30 weeks in both the mavacamten and myectomy groups, although there were subtle differences in the magnitude of reduction between the two groups: −79.80±17.87 vs. −67.70±37.94 mmHg, mean between-group difference: −12.10 mmHg (95% CI: −29.96 to −11.76), P=0.044.

LV myocardial deformation (strain)

Compared to baseline, all strain parameters significantly improved at week 30 in both HOCM patient groups: mavacamten group: GLS: −8.02%±2.92% vs. −10.56%±3.06%, P=0.001; global circumferential strain (GCS): −16.00%±2.04% vs. −17.46%±1.84%, P<0.001; global radial strain (GRS): 27.02%±4.85% vs. 30.36%±5.46%, P=0.001; myectomy group: GLS: −8.07%±2.66% vs. −10.84%±3.02%, P<0.001; GCS: −14.31%±2.70% vs. −17.63%±3.67%, P=0.007; GRS: 24.71%±6.37% vs. 33.12%±9.28%, P=0.01, as shown in Figure 3.

Figure 3 LV global strain in patients with HOCM treated with mavacamten or septal myectomy at baseline and 30 weeks and in healthy controls. Compared to baseline, all strain parameters (GLS, GCS, and GRS) significantly improved at week 30 in both mavacamten group and myectomy group. GCS, global circumferential strain; GLS, global longitudinal strain; GRS, global radial strain; HOCM, hypertrophic obstructive cardiomyopathy; LV, left ventricular.

Importantly, the magnitude of improvement in strain parameters from baseline to week 30 was not statistically different between the two treatment groups (mavacamten vs. myectomy): GLS: −2.54%±1.57% vs. −2.77%±1.44%, mean between-group difference: −0.24% (95% CI: −1.65% to 1.18%), P=0.73; GCS: −1.46%±0.54% vs. −3.31%±3.05%, mean between-group difference: −1.85% (95% CI: −3.91% to 0.21%), P=0.09; GRS: 3.34%±2.30% vs. 8.40%±8.77%, mean between-group difference: 5.06% (95% CI: −0.97% to 11.09%), P=0.10. However, at week 30, none of the LV strains had normalized to the level of the healthy control group in either HOCM patient group (P≥0.05).

LV flow components

At week 30, DF significantly increased, while RV significantly decreased from baseline in both the mavacamten and myectomy groups: mavacamten group: DF: 23.51%±4.72% vs. 29.05%±2.92%, P<0.001; RV: 37.49%±4.60% vs. 30.27%±2.19%, P=0.001; myectomy group: DF: 25.00%±5.5% vs. 34.43%±5.84%, P=0.001; RV: 37.55%±6.77% vs. 24.08%±6.75%, P<0.001. Of note, compared to the mavacamten group, the myectomy group showed a slight advantage in improving both DF and RV (mavacamten vs. myectomy): DF: 5.54%±2.02% vs. 9.43%±5.63%, mean between-group difference: 3.89% (95% CI: 0.27% to 7.86%), P=0.02; RV: −7.22%±4.33% vs. −13.47%±4.38%, mean between-group difference: −6.25% (95% CI: −10.39% to −2.11%), P=0.005, as shown in Figures 4,5.

Figure 4 LV flow components in healthy controls and HOCM patients treated with mavacamten or septal myectomy at baseline and 30 weeks. From baseline to 30 weeks, DF significantly increased, while RV significantly decreased from baseline in both the mavacamten and myectomy groups. DF, direct flow; HOCM, hypertrophic obstructive cardiomyopathy; LV, left ventricular; RV, residual volume.

Figure 5 The changes in DF and RV of all HOCM patients treated with mavacamten or septal myectomy at baseline and 30 weeks. DF, direct flow; HOCM, hypertrophic obstructive cardiomyopathy; RV, residual volume.

Reproducibility of LV global strains and flow components

Table S3 presents the intra- and interobserver reproducibility. According to the interpretive framework of Cicchetti (21), the ICC for both intraobserver (range, 0.82–0.96; mean: 0.89) and interobserver (range, 0.71–0.90; mean: 0.82) measurements all fall within the excellent agreement category (ICC ≥0.75).

Discussion

This retrospective study systematically evaluated and compared the short-term therapeutic effects of mavacamten and septal myectomy in patients with HOCM by integrating CMR-FT and 4D-flow techniques. Preliminary investigation revealed that both treatment strategies significantly improved myocardial structure, myocardial deformation and hemodynamics after 30 weeks, although slight differences were observed in LV flow components.

Previous studies have separately confirmed that both mavacamten and septal myectomy improve GLS (12,13), suggesting enhanced myocardial mechanical performance. Our study further demonstrates that during short-term follow-up, both HOCM groups showed significant and comparable improvements in all myocardial strain parameters (GLS, GCS, and GRS). This indicates that both therapies effectively restore the myocardium’s multi-directional deformation capacity and alleviate mechanical dyssynchrony. The fact that these improvements were comparable between groups and did not reach statistical significance for inter-group differences is likely influenced by the limited statistical power of our small sample size. Previous research has found that after septal myectomy in HOCM patients, circumferential strain (CS) decreases at the resection site while improving in the free wall (22). The study by Yang et al. reported that despite this improvement in free wall CS, the overall GCS decreased post-operatively compared to pre-operative levels (13). Indeed, although the resection in septal myectomy is localized to a specific area of the left ventricle, it leads to global improvements in the entire chamber (23). The significant improvement in GCS observed in our study could potentially be attributed to the possibility that the potential localized deterioration of CS at the resection site was far less significant than the overall improvement contributed by other myocardial segments. Such discrepancies may stem from differences in the extent and location of myocardial resection (23,24), which can differentially impact regional myocardial deformation. Furthermore, variations in patient baseline characteristics and follow-up timepoints. Additionally, the limited statistical power due to the small sample size may also contribute to the differing results. Future large-sample studies are necessary to further elucidate the evolutionary patterns of myocardial strain following septal myectomy.

There exists a profound intrinsic connection between intracavitary hemodynamics and myocardial deformation, which together form the core physiological basis of cardiac pump function. A previous study has identified significant correlations between global LV myocardial strain parameters and intraventricular flow components (25). In this study, both treatment methods improved LV hemodynamics while enhancing myocardial deformation capability. However, in this small cohort, septal myectomy was associated with a greater magnitude of improvement in increasing DF and reducing RV. Mavacamten has been proven to reduce LVOT obstruction, improve functional status, and reduce the need for septal reduction therapy in HOCM patients (7,26,27). LVOT obstruction is often associated with mitral apparatus abnormalities, such as elongated mitral valve leaflets, abnormal chordal attachment, and papillary muscle morphology (28,29). Previous research indicates that CMI like mavacamten alleviate outflow tract obstruction by reducing ventricular contractility and minimizing systolic LVOT collapse (30). However, they may not correct inherent anatomical issues, such as abnormalities of the mitral apparatus, in the short term. A recent study by Saleh et al. (30) suggested that elongation of the mitral valve leaflets impedes ejection through the LVOT, potentially affecting mavacamten’s therapeutic efficacy. In contrast, septal myectomy directly resects hypertrophied myocardium and is often combined with mitral valve procedures (such as anterior leaflet release or valvuloplasty) (31). This surgical approach structurally relieves outflow tract obstruction and eliminates systolic anterior motion (SAM) of the mitral valve. Notably, another comparative analysis between interventional therapy (alcohol septal ablation) and CMI showed a similar short-term improvement in mitral regurgitation to mavacamten (32), and both these treatment methods cannot correct inherent anatomical problems like mitral apparatus abnormalities in the short term. In this study, most HOCM patients in the myectomy group underwent concomitant mitral apparatus procedures, which may introduce significant inter-group heterogeneity. Consequently, the observed differences in the degree of hemodynamic improvement are likely partially attributable to this additional surgical intervention, rather than solely reflecting the efficacy difference between septal myectomy and mavacamten alone. Further exploration and more nuanced studies for clarification remain necessary. With the gradual adoption of CMI, although studies confirm that CMI reduces the need for surgical intervention to some extent (6,7), cost remains a significant factor influencing patients’ treatment decisions in the real world. Mavacamten, as a novel targeted therapy, still entails high treatment costs and currently requires long-term maintenance, in addition to regular safety monitoring (33). In contrast, septal myectomy is a one-time invasive procedure with high initial costs but offers relatively durable structural and functional improvement, avoiding the costs of long-term medication (34). Therefore, a careful discussion of the specific risks and benefits for individual patients should be an important direction for clinical decision-making in future real-world studies.

Additionally, compared with the healthy control group, HOCM patients in this study exhibited the same reduced DF and elevated RV. It is noteworthy that this pattern of reduced DF and elevated RV is also observed in diseases characterized by LV systolic dysfunction (16,35). The similar abnormalities observed in this study in HOCM patients with hyperdynamic systolic states are likely closely related to their significant diastolic dysfunction and the intraventricular flow inefficiency caused by obstruction (36,37). The study by Ashkir et al. showed that non-obstructive HCM patients, conversely, exhibited a larger proportion of DF compared to healthy controls (38). This may suggest that reduced DF and elevated RV could be regarded as an important hemodynamic characteristic distinguishing HOCM from non-obstructive HCM. This hypothesis not only provides a new dimension for understanding the pathophysiology of HOCM but also urgently awaits further exploration in future studies.

Study limitations

There are several limitations in this study. First is the issue of selection bias. The study’s small sample size and single-center origin, the inclusion of only treatment-tolerant medication‑group patients who completed 30-week therapy with full follow‑up data, the failure to enroll patients who discontinued early due to adverse events or were lost to follow‑up, and the non‑random allocation of drug or surgical treatment—all of these factors may introduce selection bias, which substantially may limit the generalizability of the results. Second, the 30-week follow-up period is relatively short, preventing an assessment of the long-term efficacy and stability of the two treatments. Finally, the analysis of 4D-flow data still partially relies on post-processing methods, and its reproducibility is associated with operator experience. Future studies with larger sample sizes, multi-center designs, and long-term follow-up are necessary. Combining more precise quantitative hemodynamic indicators will help to further clarify the advantages, disadvantages, and applicable populations of the two treatment strategies, providing greater significance for guiding clinical practice.

Conclusions

In conclusion, both mavacamten and septal myectomy are highly effective treatment strategies for HOCM. They both comprehensively improve LV structure, function, and myocardial deformation, with comparable degrees of improvement in the short term. However, septal myectomy appears to offer a modest advantage in the short-term improvement of LV flow components, which may be related to the concurrent correction of mitral apparatus abnormalities during surgery. The long-term 4D-flow CMR outcomes following treatment in HOCM patients remain unknown. Future research is necessary to further explore the long-term efficacy of both pharmacological and surgical treatments, as well as the evolutionary patterns of hemodynamics. Additionally, reduced DF and elevated RV may be important hemodynamic characteristics of HOCM.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://cdt.amegroups.com/article/view/10.21037/cdt-2025-aw-547/rc

Data Sharing Statement: Available at https://cdt.amegroups.com/article/view/10.21037/cdt-2025-aw-547/dss

Peer Review File: Available at https://cdt.amegroups.com/article/view/10.21037/cdt-2025-aw-547/prf

Funding: This work was supported by the National Key Research and Development Program of China (No. 2023YFC2414206), the National Natural Science Foundation of China (No. 82371903 to H.L.), the Guangdong Provincial Science and Technology Planning Project (No. 2023B110009), the Guangzhou Clinical High-tech, Major, and Distinctive Technology Projects (No. 2023P-TS43 to H.L.), the Natural Science Foundation of Guangdong Province (No. 2024A1515012087 to H.L.), the Science and Technology Projects in Guangzhou (No. 2025A04J4778 to Y.Y.), and the Guangdong Provincial Key Laboratory of Artificial Intelligence in Medical Image Analysis Application (No. 2022B1212010011).

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://cdt.amegroups.com/article/view/10.21037/cdt-2025-aw-547/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. This study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. It was approved by the Ethics Committee of Guangdong Provincial People’s Hospital (ethical approval No. KY2024-1100-01, approval date: January 7, 2025), and all subjects provided written informed consent.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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