Impact of Septal Myectomy on Left Atrial Volume and Left Ventricular Diastolic Filling Patterns: An Echocardiographic Study of Young Patients with Obstructive Hypertrophic Cardiomyopathy

Mitral Valve Interventions for Hypertrophic Obstructive Cardiomyopathy

The mitral valve (MV) plays an important role in the pathophysiology of hypertrophic obstructive cardiomyopathy (HOCM). Dynamic left ventricular outflow tract (LVOT) obstruction, caused by systolic anterior motion (SAM), is a common occurrence in most patients with hypertrophic cardiomyopathy and is directly associated with the MV apparatus. First line therapy for HOCM patients is pharmacological, and surgical intervention is often indicated for patients who do not respond to medical therapy. Emerging research on mitral disease in HOCM, specifically mitral regurgitation (MR), demonstrates that these patients frequently do not respond to standard therapeutic options, and can benefit from MV interventions. In this review, we describe the involvement of the MV in the pathogenesis of HOCM, discuss medical therapy, and explore available mitral procedures. Surgical myectomy, often combined with various modifications to the MV apparatus, is frequently necessary to achieve a durable resolution of LVOT obstruction and SAM-related MR. Alcohol septal ablation, an alternative to surgical myectomy, will be briefly mentioned. We also emphasize the role of transcatheter edge-to-edge repair (TEER) as a promising and novel therapeutic option for HOCM patients. Over time, TEER has established itself as an effective and safe procedure, demonstrating success across a spectrum of anatomical variations. The leaflet modification and movement restriction achieved through TEER help reduce SAM and, consequently, have the potential to alleviate LVOT obstruction and SAM-related MR. Furthermore, we propose a treatment algorithm for cases where TEER is a potential course of action for patients who are at high risk for other interventions.

Treatment Strategies for Hypertrophic Cardiomyopathy: Surgical

Septal myectomy is a well-established procedure for septal reduction in patients with obstructive hypertrophic cardiomyopathy (HCM) who have not responded to medical treatment. The surgical approach is tailored to the unique pathophysiology and septal morphology of the patient. Extended transaortic myectomy is the standard procedure for patients with isolated subaortic obstruction, the most common type of HCM. However, transapical myectomy is a useful adjunct for patients with long or midventricular obstruction and is our preferred technique for ventricular enlargement in patients with severe symptomatic diastolic heart failure because of extensive apical hypertrophy. Septal myectomy provides excellent postoperative outcomes as regards symptom relief and functional improvement, and operative morbidity and mortality rates are low in experienced centers. This article summarizes our current surgical management of patients with HCM and details operative methods and outcomes.

Contemporary Surgical Management of Hypertrophic Cardiomyopathy

More than half of symptomatic patients with hypertrophic cardiomyopathy (HCM) have left ventricular outflow tract (LVOT) obstruction. Septal reduction therapy by septal myectomy can dramatically relieve exertional dyspnea, chest pain, and presyncope in properly selected patients and is an important management pathway for many patients. The distribution and degree of hypertrophy in patients with obstructive HCM are variable and, as discussed in this review, can influence clinical manifestations of the disease and surgical management. Subaortic septal hypertrophy is the most common phenotype of obstructive HCM associated with LVOT obstruction, but midventricular obstruction and apical hypertrophy may occur in isolation or in conjunction with subaortic septal hypertrophy. In many comprehensive HCM centers, transaortic septal myectomy is the preferred method of septal reduction therapy for symptomatic patients with obstructive HCM. Early surgical approaches aimed at alleviating left LVOT obstruction were hampered by a lack of understanding of the anatomy and pathophysiology of obstructive HCM. With the advent of Doppler echocardiography and, more recently, cardiac magnetic resonance imaging, surgeons can precisely assess the location and degree of obstruction, left ventricular size and function, and morphology and function of the mitral valve. This review discusses the current understanding of the role of septal myectomy in the management of patients with HCM and details contemporary operative methods.

Effects of septal myectomy on left atrial and left ventricular function in obstructive hypertrophic cardiomyopathy

AIMS

Mechanical function of the left atrium (LA) and the left ventricle (LV) has been demonstrated to be a prognostic factor in patients with hypertrophic cardiomyopathy (HCM). We explore whether myocardial mechanical function can be improved by septal reduction therapy in symptomatic obstructive HCM.

METHODS AND RESULTS

Among 65 patients who underwent septal myectomy for symptomatic obstructive HCM from 2006 to 2022, 44 were analysed after excluding those who underwent simultaneous valve repair or replacement or maze operation. LA and LV functional variables including LA strain and LV global longitudinal strain were evaluated by two-dimensional and speckle-tracking echocardiography and compared before and 1 year after surgery. After septal myectomy, LA volume index (58.1 ± 18.3 vs. 45.3 ± 14.6 mL/m2 , P = 0.001) decreased significantly. As LV end-systolic dimension increased after surgery, the LV ejection fraction decreased (73.8 ± 6.7 vs. 62.9 ± 8.3%, P < 0.001). LA strain (24.4 ± 9.3 vs. 30.5 ± 13.6%, P = 0.004) improved after septal myectomy, but LV global longitudinal strain deteriorated (-12.6 ± 3.6 vs. -11.6 ± 4.3%, P = 0.033), mainly related to worsening non-septal longitudinal strain (-14.4 ± 4.3 vs. -10.9 ± 8.4%, P = 0.005).

CONCLUSIONS

As haemodynamic loads due to LV outflow tract obstruction was relieved through surgical septal reduction therapy in patients with symptomatic obstructive HCM, there was a significant reduction in LA volume and restoration of LA mechanical dysfunction. However, LV mechanical dysfunction deteriorated even after surgical septal reduction therapy.

Medical Therapies to Improve Left Ventricular Outflow Obstruction and Diastolic Function in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy-both obstructive hypertrophic cardiomyopathy (oHCM) and nonobstructive hypertrophic cardiomyopathy (nHCM) subtypes-is the most common monogenic cardiomyopathy. Its structural hallmarks are abnormal thickening of the myocardium and hyperdynamic contractility, while its hemodynamic consequences are left ventricular outflow tract or intracavitary obstruction (in oHCM) and diastolic dysfunction (in both oHCM and nHCM). Several medical therapies are routinely used to improve these abnormalities with the goal to decrease symptom burden in patients with HCM. Current guidelines recommend nonvasodilating beta blockers as first-line and nondihydropyridine calcium channel blockers followed by disopyramide as second- and third-line medical therapies for symptomatic oHCM and give weaker recommendations for beta blockers and calcium channel blockers in nHCM. These recommendations are based on small studies-mostly nonrandomized-and expert opinion. Our review will summarize the available data on the effectiveness of commonly prescribed medications used in oHCM and nHCM to uncover knowledge gaps, but also new data on cardiac myosin inhibitors.

Reverse remodeling of left atrium assessed by cardiovascular magnetic resonance feature tracking in hypertrophic obstructive cardiomyopathy after septal myectomy

BACKGROUND

Assessing the structure and function of left atrium (LA) is crucial in hypertrophic obstructive cardiomyopathy (HOCM) because LA remodeling correlates with atrial fibrillation. However, few studies have investigated the potential effect of myomectomy on LA phasic remodeling in HOCM after myectomy using cardiovascular magnetic resonance (CMR) feature tracking (FT). This study aims to evaluate the LA structural and functional remodeling with HOCM after myectomy by CMR-FT and to further investigate the determinants of LA reverse remodeling.

METHODS

In this single-center study, we retrospectively studied 88 patients with HOCM who received CMR before and after myectomy between January 2011 and June 2021. Preoperative and postoperative LA parameters derived from CMR-FT were compared, including LA reservoir function (total ejection fraction [EF], total strain [εs], peak positive strain rate [SRs]), conduit function (passive EF, passive strain [εe], peak early negative strain rate [SRe]) and booster function (booster EF, active strain [εa], late peak negative strain rate [SRa]). Eighty-six healthy participants were collected for comparison. Univariate and multivariate linear regression identified variables associated with the rate of change of εa.

RESULTS

Compared with preoperative parameters, LA reservoir function (total EF, εs, SRs), booster function (booster EF, εa, SRa), and SRe were significantly improved after myectomy (all P < 0.05), while no significant differences were observed in passive EF and εe. Postoperative patients with HOCM still had larger LA and worse LA function than healthy controls (all P < 0.05). After analyzing the rates of change in LA parameters, LA boost function, especially εa, showed the most dramatic improvement beyond the improvements in reservoir function, conduit function, and volume. In multivariable regression analysis, minimum LA volume index (adjusted β = - 0.39, P < 0.001) and Δleft ventricular outflow tract (LVOT) pressure gradient (adjusted β = - 0.29, P = 0.003) were significantly related to the rate of change of εa.

CONCLUSIONS

Patients with HOCM after septal myectomy showed LA reverse remodeling with a reduction in LA size and restoration in LA reservoir and booster function but unchanged LA conduit function. Among volumetric and functional changes, booster function had the greatest improvement postoperatively. Besides, preoperative LAVmin index and ΔLVOT might be potential factors associated with the degree of improvement in εa.

Association between left ventricular reverse remodeling and long-term outcomes after alcohol septal ablation for hypertrophic obstructive cardiomyopathy

There is a paucity of data regarding the effect of left ventricular (LV) reverse remodeling (r-LVR) on diastolic function and outcomes after alcohol septal ablation (ASA) in patients with hypertrophic obstructive cardiomyopathy (HOCM). The aim of this study was to identify the impact of r-LVR on the outcome and the predictors of such changes after ASA. Eighty-seven patients (57.5% men) were enrolled and underwent both echocardiography and cardiovascular magnetic resonance (CMR) imaging at baseline and 27 months after the procedure. The study population was divided into two groups by the degree of r-LVR. Compared to the greater r-LVR group, the lesser r-LVR group had a significantly larger LV mass (LVM) and lower diastolic function parameters at baseline. The greater r-LVR group had significantly greater LVM regression and improvement of diastolic function after ASA. Kaplan‒Meier analysis showed significantly worse composite events in the lesser r-LVR group after ASA (P = 0.016). After adjusting for multiple clinical variables, r-LVR was associated with an improved E/e' (β = 0.390, p < 0.001) and reduced events (hazard ratio: 0.795; 95% confidence interval (CI), 0.644-0.983; p = 0.034). Preablation LVM was associated with a decreased probability of r-LVR (β = -0.228, p = 0.021) and diastolic function improvement (β= -0.245, p = 0.006). r-LVR was associated with long-term outcome benefit in patients with HOCM. Preablation LVM prevented LV from favoring reverse remodeling and thus may be a potential parameter for risk stratification and prognosis after ASA treatment.

Left atrial remodeling postseptal myectomy for severe obstructive hypertrophic cardiomyopathy: Analysis by two-dimensional speckle-tracking echocardiography

BACKGROUND

Septal myectomy relieves left ventricular outflow obstruction (LVOTO) and is associated with excellent long-term outcomes. LVOTO is associated with diastolic dysfunction and increased left atrial (LA) size. We sought to investigate the changes in LA volumes and function postmyectomy and the association between these changes with clinical outcomes postmyectomy.

METHODS

Sixty-six hypertrophic cardiomyopathy patients undergoing myectomy were retrospectively studied. Preprocedural and 6- to 18-month postmyectomy follow-up transthoracic echocardiographic images were obtained. LA volumes and strain were assessed by two-dimensional speckle-tracking echocardiography.

RESULTS

Left atrial volumes, that is, indexed maximal, minimal, and pre-A volumes reduced postmyectomy, yet remained increased compared to controls (105.6 ± 34.5 mL vs 84.9 ± 26.7 mL, 45.2 ± 25.7 mL vs 35.4 ± 22.6 mL, 70.1 ± 31.4 mL vs 35.4 ± 22.6 mL, respectively, P < 0.05). The total emptying index did not improve postmyectomy and remained lower than controls (58.6 ± 12.4 vs 59.9 ± 12.8, P = NS) whereas atrial contraction improved, yet did not normalize (active emptying index 36.1 ± 14.9 vs 41.1 ± 16.2, P < 0.05). The conduit volume remained reduced postmyectomy (18.6 ± 13.3 mL vs 16.6 ± 15.1 mL, P = NS). LA strain also did not improve postmyectomy (26.8 ± 7.3 vs 28.5 ± 8.8, P = NS). A multivariable logistic regression identified preprocedural E/e' ratio and indexed maximal LA volume, as independent predictors for LA volume reduction ≥20% postmyectomy. During a mean follow-up of 4.9 ± 2.3 years postmyectomy, 24.2% of the patients developed atrial fibrillation and <5% of patients were severely symptomatic. We found no associations between LA volumes/function and atrial fibrillation or symptoms postmyectomy.

CONCLUSION

Postmyectomy LA volumes decreased, and the contractile function improved. There was no association between LA volumes/function and clinical outcomes postmyectomy. Notably, the LA remained enlarged (though to a lesser degree) with reduced strain and emptying fraction, suggesting possible atrial myopathy.

Septal Ablation for Hypertrophic Obstructive Cardiomyopathy: Transcoronary and Endocardial Approach

Septal reduction therapy is the gold standard treatment method for symptomatic, hypertrophic obstructive cardiomyopathy. Although surgical myectomy is a well-established and effective technique with decades of experience in its application, use of transcoronary alcohol septal ablation has increased precipitously owing to the less-invasive nature of the procedure. Moreover, endocardial septal ablation therapy is a relatively newly defined modality, and outcomes of the procedure are not clearly elucidated yet. In this review, we aimed to present nonsurgical septal reduction approaches in patients with hypertrophic obstructive cardiomyopathy.

Effects of septal myectomy on left ventricular diastolic function and left atrial volume in patients with hypertrophic cardiomyopathy

Ventricular septal myectomy in patients with obstructive hypertrophic cardiomyopathy (HC) has been shown to reduce left ventricular (LV) outflow tract (LVOT) gradient and improve symptoms, although little data exist regarding changes in left atrial (LA) volume and LV diastolic function after myectomy. We investigated changes in LA size and LV diastolic function in patients with HC after septal myectomy from 2004 to 2011. We studied 25 patients (age 49.2 ± 13.1 years, 48% women) followed for a mean of 527 days after surgery who had serial echocardiography at baseline and at most recent follow-up, at least 6 months after myectomy. In addition to myectomy, 3 patients (12%) underwent Maze surgery and 13 (52%) underwent mitral valve surgery, of whom 5 had a mitral valve replacement or mitral annuloplasty. Patients with mitral valve replacement or mitral annuloplasty were excluded from LV diastolic function analysis. LA volume index decreased (from 47.2 ± 17.6 to 35.9 ± 17.0 ml/m(2), p = 0.001) and LV diastolic function improved with an increase in lateral e' velocity (from 7.3 ± 2.9 to 9.8 ± 3.1 cm/sec, p = 0.01) and a decrease in E/e' (from 14.8 ± 6.3 to 11.7 ± 5.5, p = 0.051). Ventricular septal thickness and LVOT gradient decreased, and symptoms of dyspnea and heart failure improved, with reduction in the New York Heart Association functional class III/IV symptoms from 21 (84%) to 1 (4%). In conclusion, relief of LVOT obstruction in HC by septal myectomy results in improved LV diastolic function and reduction in LA volume with improved symptoms.

The regional myocardial microvascular dysfunction differences in hypertrophic cardiomyopathy patients with or without left ventricular outflow tract obstruction: assessment with first-pass perfusion imaging using 3.0-T cardiac magnetic resonance

PURPOSE

To assess regional myocardial microvascular dysfunction differences in hypertrophic cardiomyopathy (HCM) patients with or without left ventricular outflow tract obstruction using 3.0-T cardiac magnetic resonance (CMR) first-pass perfusion imaging.

MATERIALS AND METHODS

Forty-two HCM patients, including 25 HCM patients with left ventricular outflow tract obstruction (HOCM), 17 HCM patients without left ventricular outflow tract obstruction (NOHCM), and 14 healthy subjects underwent CMR. The left ventricular (LV) function, left ventricular end-diastolic wall thickness (EDTH), and diameter of left ventricular outflow tract (LVOT) were measured and calculated. Based on the signal-time curve of the first-pass myocardium perfusion imaging, perfusion parameters including upslope, time to peak, and peak intensity, were assessed and compared by using one-way analysis of variance and independent t tests.

RESULTS

On the first-pass perfusion imaging, lower upslope and peak intensity and longer time to peak were found in HCM patients compared with normal subjects (all p<0.05). In contrast to the NOHCM group, the average time to peak of the HOCM group was increased (13.30 ± 4.82 s vs 16.28 ± 4.90 s, p<0.05), but first-pass perfusion upslope was reduced (4.96 ± 2.55 vs 2.58 ± 0.77, p<0.05). According to the bull's-eye model, the HOCM group's average thickness of basal segments was thicker than the NOHCM group, especially the anteroseptal, inferolateral, and anterior wall values, with a corresponding lower first-pass perfusion upslope than the NOHCM group (all p<0.05). A significant correlation was observed between first-pass perfusion upslope and LV EDTH (r=-0.551, p<0.001) and LVOT diameter (r=0.472, p<0.001).

CONCLUSIONS

The regional myocardial microvascular dysfunction differences in hypertrophic cardiomyopathy (HCM) patients with or without left ventricular outflow tract obstruction can be detected with first-pass perfusion CMR imaging.

A retrospective clinical study of transaortic extended septal myectomy for obstructive hypertrophic cardiomyopathy in China

OBJECTIVES

The aim was to assess the early and mid-term clinical effects of transaortic extended septal myectomy (TAESM) on obstructive hypertrophic cardiomyopathy (HCM) in China.

METHODS

Ninety-three consecutive patients [57 men; mean age 45.8 ± 13.4 (11–74) years] with obstructive HCM underwent TAESM in Fuwai hospital. Their clinical data were analysed retrospectively. All the patients had drug-refractory symptoms and left ventricular outflow tract (LVOT) obstruction with a resting or physically provoked gradient of ≥50 mmHg. Preoperative transthoracic, intra-operative transoesophageal and postoperative transthoracic echocardiography was performed to assess LVOT gradients, septal thickness, LVOT diameter, mitral valve function, etc. Systolic anterior motion (SAM) of the anterior mitral valve leaflet had been detected in all preoperatively.

RESULTS

All the surgical procedures of the 93 patients were technically successful. The average length of postoperative stay was 7.8 ± 3.7 days. The 30-day and in-hospital mortality was 0%. Initial postoperative transoesophageal echocardiography (TEE) demonstrated marked reduction in LVOT gradient (91.76 ± 25.08 to 14.34 ± 13.44 mmHg, P < 0.0005) and significant improvement in mitral regurgitation (MR; P < 0.0005). Concomitant surgical procedures were carried out in 37 (39.8%). Complete atrioventricular block occurred in 3, complete left bundle branch block in 44, intraventricular conduction delay in 18, complete right bundle branch block in 2, transient renal dysfunction in 2 and transient intra-aortic-balloon-pumping was needed in 2. No other complications were observed during hospital stay. During a follow-up of 10.72 ± 11.02 (1–24) months, there were no readmissions or deaths, and all patients subjectively reported an obvious decrease in limiting symptoms and a significant increase in physical ability. At the latest follow-up, the New York Heart Association functional class decreased from 3.09 ± 0.60 (2–4) preoperatively to 1.12 ± 0.32 (1–2) (P < 0.0005); the LVOT gradient remained low at 14.78 ± 14.01 mmHg; MR remained absent (51) or at mild-(41)-to-moderate-(1) levels and SAM resolved completely in 98.9% (92 of 93) patients.

CONCLUSIONS

TAESM provides excellent relief from LVOT obstruction in HCM patients, with a conspicuous clinical and echocardiographic outcome at early and mid-term follow-up. For obstructive HCM and cardiac comorbidities, concomitant cardiac procedures with TAESM can be performed with low risk and satisfactory results.

Hypertrophic cardiomyopathy in childhood

Hypertrophic cardiomyopathy has important differences in children compared with adults, particularly with regard to the range of causes and the outcomes in infants. Survival is highly dependent on etiology, particularly in the youngest patients, and pursuit of the specific cause is therefore necessary. The clinical utility of defining the genotype in children with familial hypertrophic cardiomyopathy exceeds that at other ages and has a highly favorable cost/benefit ratio. Although most of the available information concerning treatment and prevention of sudden death is derived in adults, management of children requires consideration of the differences in age-specific risk/benefit ratios.

Left atrial volume in children without heart disease and in those with ventricular septal defect or patent ductus arteriosus or hypertrophic cardiomyopathy

In adults, the left atrial (LA) volume has been shown to reflect diastolic function and is a powerful predictor of cardiac morbidity and mortality. Normative LA volume values in children and the effect of loading conditions on the LA volume in those with congenital heart disease are lacking. The purposes of the present study were to (1) establish normal LA volume values for children, (2) assess the effect of left ventricular volume loading conditions on LA volume, and (3) describe the effect of abnormal myocardial relaxation on the LA volume. We retrospectively reviewed the echocardiograms from 3 pediatric cohorts: group N (n = 522), children with normal echocardiographic findings; group VSD/PDA (n = 71), children with ventricular septal defect (VSD; n = 50) or patent ductus arteriosus (PDA; n = 21); and group HC (n = 63), children with hypertrophic cardiomyopathy (HC). In group N, we identified the LA volume indexed to the body surface area (LA volume index) as a consistent measure of the LA volume in children 3 to 23 months old (mean 16 ± 3 ml/m(2)) and 2 to 17 years old (mean 22 ± 4 ml/m(2)). LA dilation was more common in group VSD/PDA than in group N (27% vs 2%, p <0.0001) and in children with moderate or large shunts than in those with smaller shunts (61% vs 5%, p <0.0001). In group HC, the LA volume index correlated with the mitral valve E/e' ratio (p <0.0001). In conclusion, this is the first study to establish normal pediatric LA volume values. The LA volume index is a reproducible measure of LA size in children ≥ 3 months old. The LA volume index reflects a chronically increased left ventricular volume load in children with VSD or PDA and chronically elevated left ventricular filling pressures in children with HC.

Diastolic dysfunction and its histopathological correlation in obstructive hypertrophic cardiomyopathy in children and adolescents

BACKGROUND

Histopathologic hallmarks of hypertrophic cardiomyopathy (HCM) include myocyte hypertrophy and disarray as well as interstitial and endocardial fibrosis. Published correlations between echocardiographic parameters and histopathologic findings are scarce.

METHODS

All patients aged <20 years (n = 45; 15 female patients; median age, 14 years) with obstructive HCM undergoing septal myectomy at the Mayo Clinic from 2003 to 2007 were identified. A retrospective review of echocardiographic data was performed, and these data were compared with the histologic findings from the myectomy specimens.

RESULTS

Histopathologic analysis of myectomy specimens revealed significant myocyte hypertrophy (100%), myocyte disarray (98%), interstitial fibrosis (95%), and subendocardial fibrosis (97%). On multivariate regression analysis, there was a significant relationship between the degree of myocyte disarray and echocardiographic markers of left ventricular diastolic dysfunction.

CONCLUSION

The results of this study suggest that myocyte disarray is a key factor responsible for diastolic dysfunction in pediatric patients with obstructive HCM. These findings provide novel insights into the mechanism of diastolic dysfunction in HCM that warrant further study.