Effects of surgical septal myectomy on left ventricular wall thickness and diastolic filling

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.

Posterior Wall Thickness Associates With Survival Following Septal Myectomy for Obstructive Hypertrophic Cardiomyopathy

BACKGROUND

The left ventricular (LV) posterior wall thickness (PWT) is a predictor of sudden cardiac death in pediatric patients with hypertrophic cardiomyopathy (HCM), but the prognostic importance of PWT in adults has not been examined.

OBJECTIVES

The goal of this study was to evaluate the association of LV PWT with late survival in adult patients undergoing septal myectomy for obstructive HCM.

METHODS

This single-center study reviewed 2,418 patients who underwent transaortic septal myectomy for obstructive HCM.

RESULTS

The median preoperative PWT was 13 (IQR: 11-15) mm. Patients with PWT >13 mm tended to have systemic hypertension (55.4% vs 49.1%; P = 0.002) and a larger body mass index (median: 30.8 [IQR: 27.1-35.1] kg/m² vs 29.6 [IQR: 26.1-33.9] kg/m²; P < 0.001). Preoperatively, PWT >13 mm was associated with increased septal thickness (median: 21 [IQR: 18-24] mm vs 19 [IQR: 17-22] mm; P < 0.001), greater maximum instantaneous left ventricular outflow tract (LVOT) gradient at rest (median: 67 [IQR: 36-96] mm Hg vs 47 [IQR: 19-79] mm Hg), and increased likelihood of moderate or greater mitral valve regurgitation (54.3% vs 47.3%; P = 0.001). However, PWT was not related to the severity of limitations measured by New York Heart Association functional class (P = 0.674). After adjusting for baseline covariates, greater PWT was an independent risk factor for late mortality after septal myectomy (P = 0.003).

CONCLUSIONS

PWT is a newly identified predictor of reduced long-term survival after septal myectomy that is independent of septal thickness and severity of LVOT gradient. Future studies are warranted to investigate the mechanisms underlying the association and the potential usefulness of PWT in patient management.

Surgical management of diastolic heart failure after septal myectomy for obstructive hypertrophic cardiomyopathy

Objective

Some patients with obstructive hypertrophic cardiomyopathy may remain limited after surgical relief of the subaortic obstruction. In this report, we describe experience in surgical management of patients with advanced diastolic heart failure symptoms after adequate transaortic septal myectomy for obstructive hypertrophic cardiomyopathy.

Methods

We identified adult patients who presented with heart failure symptoms after previous transaortic septal myectomy for obstructive hypertrophic cardiomyopathy and underwent repeat sternotomy for transapical myectomy to enlarge a small left ventricular cavity. Functional recovery after hospital dismissal was assessed through a questionnaire-based survey.

Results

Six patients with previous septal myectomy presented with New York Heart Association functional class III symptoms. Preoperative transthoracic Doppler echocardiography confirmed adequate relief of subaortic outflow tract obstruction with only trivial or mild mitral valve regurgitation; left atrial volume index was increased at 46 mL/m² (range, 44-47 mL/m²). Following transapical myectomy, the left ventricular diameter was enlarged from 23 mm (range, 21-27 mm) to 29 mm (range, 27-31 mm) at end-systole and from 40 mm (range, 38-42 mm) to 43 mm (range, 42-50 mm) at end-diastole. All the patients were alive after a median follow-up of 0.6 years (range, 0.4-3.5 years), and 5 patients responded to a postoperative survey and indicated improvement in their heart condition compared with functional status before the repeat myectomy.

Conclusions

Patients with diastolic heart failure after septal myectomy for obstructive hypertrophic cardiomyopathy may present with systolic cavity obliteration due to excessive myocardial hypertrophy. Repeat transapical myectomy can enlarge the left ventricular chamber and augment the diastolic volume, which results in improved physical capacity and patient-perceived functional status.

Differences in molecular phenotype in mouse and human hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is characterized by phenotypic heterogeneity. We investigated the molecular basis of the cardiac phenotype in two mouse models at established disease stage (mouse-HCM), and human myectomy tissue (human-HCM). We analyzed the transcriptome in 2 mouse models with non-obstructive HCM (R403Q-MyHC, R92W-TnT)/littermate-control hearts at 24 weeks of age, and in myectomy tissue of patients with obstructive HCM/control hearts (GSE36961, GSE36946). Additionally, we examined myocyte redox, cardiac mitochondrial DNA copy number (mtDNA-CN), mt-respiration, mt-ROS generation/scavenging and mt-Ca²⁺ handling in mice. We identified distinct allele-specific gene expression in mouse-HCM, and marked differences between mouse-HCM and human-HCM. Only two genes (CASQ1, GPT1) were similarly dysregulated in both mutant mice and human-HCM. No signaling pathway or transcription factor was predicted to be similarly dysregulated (by Ingenuity Pathway Analysis) in both mutant mice and human-HCM. Losartan was a predicted therapy only in TnT-mutant mice. KEGG pathway analysis revealed enrichment for several metabolic pathways, but only pyruvate metabolism was enriched in both mutant mice and human-HCM. Both mutant mouse myocytes demonstrated evidence of an oxidized redox environment. Mitochondrial complex I RCR was lower in both mutant mice compared to controls. MyHC-mutant mice had similar mtDNA-CN and mt-Ca²⁺ handling, but TnT-mutant mice exhibited lower mtDNA-CN and impaired mt-Ca²⁺ handling, compared to littermate-controls. Molecular profiling reveals differences in gene expression, transcriptional regulation, intracellular signaling and mt-number/function in 2 mouse models at established disease stage. Further studies are needed to confirm differences in gene expression between mouse and human-HCM, and to examine whether cardiac phenotype, genotype and/or species differences underlie the divergence in molecular profiles.

Influence of operator volume on early outcomes of septal myectomy for isolated hypertrophic obstructive cardiomyopathy

Background

Guidelines on the diagnosis and management of hypertrophic cardiomyopathy (HCM) recommend that septal myectomy be performed by experienced operators. However, the impact of operator volume on surgical treatment outcomes for isolated HCM has been poorly investigated.

Methods

From 2002 to 2014, 435 consecutive patients with isolated HCM undergoing myectomy at the Fuwai Hospital were retrospectively enrolled. All 29 surgeons were divided into beginner surgeons (operator volume ≤20) and experienced surgeons (operator volume >20) according to the guidelines for the diagnosis and treatment of HCM. Propensity score matching of patients in the two groups was performed.

Results

Baseline differences included advanced New York Heart Association classification and older age in the experienced surgeon group. After matching, in the beginner surgeon group (107 cases), residual obstruction (18.7% vs. 0.9%, P<0.001) was more common, and the postoperative left ventricular outflow tract pressure gradient (20.7±15.1 vs. 14.3±7.4 mmHg, P<0.001) was higher than that of the experienced surgeon group. In the experienced surgeon group (107 cases), the incidence of mitral valve replacement (1.9% vs. 11.2%, P<0.001) and permanent pacemaker implantation (1.9% vs. 3.7%, P<0.001) was significantly lower than that in the beginner surgeon group. However, there was no difference in procedural mortality (1.9% vs. 1.9%) between the two groups.

Conclusions

Operator volume is an important factor in achieving better obstruction obliteration after septal myectomy in patients with isolated HCM.

Interventional therapies for relief of obstruction in hypertrophic cardiomyopathy: discussion and proposed clinical algorithm

Hypertrophic cardiomyopathy (HCM), a disease formerly thought rare in clinical practice, is now believed to affect as many as 1 in 300 individuals, regardless of race or gender. Rising awareness, coupled with advanced imaging and the development of dedicated HCM centers of excellence, has led to more patients coming to clinical presentation. While some are diagnosed at a young age, others are diagnosed in middle age or well into advanced age. Unfortunately, many such patients have progressed clinically to overt heart failure, or have some combination of advanced symptoms including dyspnea, angina, pre-syncope or syncope, palpitations, and edema. Anatomic subsets, including those with mid-ventricular obstruction or apical disease, with or without apical aneurysm, have also been seen in increasing frequency. Fortunately, both percutaneous and surgical invasive options are available across the spectrum of disease severity and anatomy, with outcomes continuing to improve as the techniques and experience evolve. Advances in both approaches allow targeted and individualized treatment of the majority of these patients. This review will focus on interventional approaches to relief of obstruction, and will provide a current clinical algorithm from our center for determining when an interventional approach may be recommended or optimal over a surgical approach, and vice versa.

Long-Term Prognosis after Myectomy in Hypertrophic Obstructive Cardiomyopathy with Severe Left Ventricular Hypertrophy

Objectives: Patients with hypertrophic obstructive cardiomyopathy (HOCM) and severe left ventricular hypertrophy (maximal left ventricular wall thickness ≥30 mm) are at high risk of sudden cardiac death (SCD). In this study, we aimed to determine whether HOCM patients with severe hypertrophy had a lower incidence of SCD after myectomy. Methods: HOCM patients with severe hypertrophy were consecutively enrolled from Fuwai Hospital in China between 2000 and 2013. Long-term outcomes were retrospectively compared between the 2 groups, namely the myectomy group and medical group. Results: A total of 244 patients (118 in the myectomy group and 126 in the medical group) were involved. The mean follow-up durations for the myectomy and medical groups were 5.07 ± 3.73 and 6.23 ± 4.15 years, respectively. During the follow-up period, the annual cardiovascular mortality rate was 0.84% in the myectomy group and 2.04% in the medical group (p = 0.041). The annual SCD rate was 0.33% in the myectomy group and 1.40% in the medical group (p = 0.040). Multivariate Cox regression analysis showed that myectomy was independently associated with lower rates of cardiovascular death and SCD. Conclusions: In HOCM patients with severe hypertrophy, those that underwent myectomy had a lower risk of cardiovascular death and SCD than those treated with medicines only.

Long-term benefit of myectomy and anterior mitral leaflet extension in obstructive hypertrophic cardiomyopathy

Severely symptomatic patients with obstructive hypertrophic cardiomyopathy (HC) may benefit from surgical myectomy. In patients with enlarged mitral leaflets and mitral regurgitation, myectomy can be combined with anterior mitral leaflet extension (AMLE) to stiffen the midsegment of the leaflet. The aim of this study was to evaluate the long-term results of myectomy combined with AMLE in patients with obstructive HC. This prospective, observational, single-center cohort study included 98 patients (49 ± 14 years, 37% female) who underwent myectomy combined with AMLE from 1991 to 2012. End points included all-cause mortality and change in clinical and echocardiographic characteristics. Mortality was compared with age- and gender-matched patients with nonobstructive HC and subjects from the general population. Long-term follow-up was 8.3 ± 6.1 years. There was no operative mortality, and New York Heart Association class was reduced from 2.8 ± 0.5 to 1.3 ± 0.5 (p <0.001), left ventricular outflow tract gradient from 93 ± 25 to 9 ± 8 mm Hg (p <0.001), mitral valve regurgitation from grade 2.0 ± 0.9 to 0.5 ± 0.8 (p <0.001), and systolic anterior motion of the mitral valve from grade 2.4 ± 0.9 to 0.1 ± 0.3 (p <0.001). The 1-, 5-, 10-, and 15-year cumulative survival rates were 98%, 92%, 86%, and 83%, respectively, and did not differ from the general population (99%, 97%, 92%, and 85%, respectively, p = 0.3) or patients with nonobstructive HC (98%, 97%, 88%, and 83%, respectively, p = 0.8). In conclusion, in selected patients with obstructive HC, myectomy combined with AMLE is a low-risk surgical procedure. It results in long-term symptom relief and survival similar to the general population.

Pattern and degree of left ventricular remodeling following a tailored surgical approach for hypertrophic obstructive cardiomyopathy

Background The role of a tailored surgical approach for hypertrophic cardiomyopathy (HCM) on regional ventricular remodelling remains unknown. The aims of this study were to evaluate the pattern, extent and functional impact of regional ventricular remodelling after a tailored surgical approach. Methods From 2005 to 2008, 44 patients with obstructive HCM underwent tailored surgical intervention. Of those, 14 were ineligible for cardiac magnetic resonance (CMR) studies. From the remainder, 14 unselected patients (42±12 years) underwent pre- and post-operative CMR studies at a median 12 months post-operatively (range 4–37 months). Regional changes in left ventricular (LV) thickness as well as global LV function following surgery were assessed using CMR Tools (London, UK). Results Pre-operative mean echocardiographic septal thickness was 21±4 mm and mean LV outflow gradient was 69±32 mmHg. Following surgery, there was a significant degree of regional regression of LV thickness in all segments of the LV, ranging from 16% in the antero-lateral midventricular segment to 41% in the anterior basal segment. Wall thickening was significantly increased in basal segments but showed no significant change in the midventricular or apical segments. Globally, mean indexed LV mass decreased significantly after surgery (120±29g/m2 versus 154±36g/m2; p<0.001). There was a trend for increased indexed LV end-diastolic volume (70±13 mL versus 65±11 mL; p=0.16) with a normalization of LV ejection fraction (68±7% versus 75±9%; p<0.01). Conclusion Following a tailored surgical relief of outflow obstruction for HCM, there is a marked regional reverse LV remodelling. These changes could have a significant impact on overall ventricular dynamics and function.

Surgical management of obstructive hypertrophic cardiomyopathy: the gold standard

While medication is the first line of therapy in obstructive hypertrophic cardiomyopathy, patients who have symptoms refractory to medical treatment or asymptomatic patients with high resting gradients (>or=30 mmHg) may require septal myectomy. Surgical septal myectomy can be performed safely, with excellent survival, relief from symptoms and low morbidity. Alcohol septal ablation is an alternative to surgical treatment, but late outcomes are uncertain. Although both methods of septal reduction relieve left ventricular outflow tract gradients and improve functional status, the need for permanent pacing appears higher with alcohol ablation compared with surgical myectomy. As our understanding of obstructive hypertrophic cardiomyopathy continues to grow, the indications for intervention will evolve. In our practice, septal myectomy remains the gold standard for treatment of obstructive hypertrophic cardiomyopathy.