Transcatheter Myotomy for Hypertrophic Obstructive Cardiomyopathy

PURPOSE OF REVIEW

To describe the emerging role of transcatheter septal myotomy in the treatment of hypertrophic obstructive cardiomyopathy.

RECENT FINDINGS

Transcatheter septal myotomy was developed to address risk of LVOT obstruction during TMVR, however it has been performed in patients with LVOT obstruction related to hypertrophic cardiomyopathy, in whom it improves symptoms, reduces LVOT gradients, and is associated with low incidence of procedural complications. Transcatheter myotomy is a novel approach to address LVOT obstruction related to hypertrophic cardiomyopathy in patients who are not favorable surgical candidates. The risk of conduction abnormalities with transcatheter septal myotomy appears low. Research is needed to define optimal patient selection and long-term outcomes.

Allele-specific dysregulation of lipid and energy metabolism in early-stage hypertrophic cardiomyopathy

Introduction

Hypertrophic cardiomyopathy (HCM) results from pathogenic variants in sarcomeric protein genes that increase myocyte energy demand and lead to cardiac hypertrophy. However, it is unknown whether a common metabolic trait underlies cardiac phenotype at the early disease stage. To address this question and define cardiac biochemical pathology in early-stage HCM, we studied two HCM mouse models that express pathogenic variants in cardiac troponin T (Tnt2) or myosin heavy chain (Myh6) genes, and have marked differences in cardiac imaging phenotype, mitochondrial function at early disease stage.

Methods

We used a combination of echocardiography, transcriptomics, mass spectrometry-based untargeted metabolomics (GC-TOF, HILIC, CSH-QTOF), and computational modeling (CardioNet) to examine cardiac structural and metabolic remodeling at early disease stage (5 weeks of age) in R92W-TnT+/- and R403Q-MyHC+/- mutant mice. Data from mutants was compared with respective littermate controls (WT).

Results

Allele-specific differences in cardiac phenotype, gene expression and metabolites were observed at early disease stage. LV diastolic dysfunction was prominent in TnT mutants. Differentially-expressed genes in TnT mutant hearts were predominantly enriched in the Krebs cycle, respiratory electron transport, and branched-chain amino acid metabolism, whereas MyHC mutants were enriched in mitochondrial biogenesis, calcium homeostasis, and liver-X-receptor signaling. Both mutant hearts demonstrated significant alterations in levels of purine nucleosides, trisaccharides, dicarboxylic acids, acylcarnitines, phosphatidylethanolamines, phosphatidylinositols, ceramides and triglycerides; 40.4 % of lipids and 24.7 % of metabolites were significantly different in TnT mutants, whereas 10.4 % of lipids and 5.8 % of metabolites were significantly different in MyHC mutants. Both mutant hearts had a lower abundance of unsaturated long-chain acyl-carnitines (18:1, 18:2, 20:1), but only TnT mutants showed enrichment of FA18:0 in ceramide and cardiolipin species. CardioNet predicted impaired energy substrate metabolism and greater phospholipid remodeling in TnT mutants than in MyHC mutants.

Conclusions

Our systems biology approach revealed marked differences in metabolic remodeling in R92W-TnT and R403Q-MyHC mutant hearts, with TnT mutants showing greater derangements than MyHC mutants, at early disease stage. Changes in cardiolipin composition in TnT mutants could contribute to impairment of energy metabolism and diastolic dysfunction observed in this study, and predispose to energetic stress, ventricular arrhythmias under high workloads such as exercise.

Lipid metabolism drives allele-specific early-stage hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) results from pathogenic variants in sarcomeric protein genes, that increase myocyte energy demand and lead to cardiac hypertrophy. But it is unknown whether a common metabolic trait underlies the cardiac phenotype at early disease stage. This study characterized two HCM mouse models (R92W-TnT, R403Q-MyHC) that demonstrate differences in mitochondrial function at early disease stage. Using a combination of cardiac phenotyping, transcriptomics, mass spectrometry-based metabolomics and computational modeling, we discovered allele-specific differences in cardiac structure/function and metabolic changes. TnT-mutant hearts had impaired energy substrate metabolism and increased phospholipid remodeling compared to MyHC-mutants. TnT-mutants showed increased incorporation of saturated fatty acid residues into ceramides, cardiolipin, and increased lipid peroxidation, that could underlie allele-specific differences in mitochondrial function and cardiomyopathy.

Accurate Classification of Non-ischemic Cardiomyopathy

PURPOSE OF REVIEW

This article aims to review the accurate classification of non-ischemic cardiomyopathy, including the methods, basis, subtype characteristics, and prognosis, especially the similarities and differences between different classifications.

RECENT FINDINGS

Non-ischemic cardiomyopathy refers to a myocardial disease that excludes coronary artery disease or ischemic injury and has a variety of etiologies and high incidence. Recent studies suggest that traditional classification methods based on primary/mixed/acquired or genetic/non-genetic cannot meet the precise needs of contemporary clinical management. This article systematically describes the history of classifications of cardiomyopathy and presents etiological and genetic differences between cardiomyopathies. The accurate classification is described from the perspective of morphology, function, and genomics in hypertrophic cardiomyopathy, dilated cardiomyopathy, restrictive cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, left ventricular noncompaction, and partially acquired cardiomyopathy. The different clinical characteristics and treatment needs of these cardiomyopathies are elaborated. Some single-gene mutant cardiomyopathies have unique phenotypes, and some cardiomyopathies have mixed phenotypes. These special classifications require personalized precision treatment, which is worthy of independent research. This article describes recent advances in the accurate classification of non-ischemic cardiomyopathy from clinical phenotypes and causative genes, discusses the advantages and usage scenarios of each classification, compares the differences in prognosis and patient management needs of different subtypes, and summarizes common methods and new exploration directions for accurate classification.

Targeting the sarcomere in inherited cardiomyopathies

Variants in >12 genes encoding sarcomeric proteins can cause various cardiomyopathies. The two most common are hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM). Current therapeutics do not target the root causes of these diseases, but attempt to prevent disease progression and/or to manage symptoms. Accordingly, novel approaches are being developed to treat the cardiac muscle dysfunction directly. Challenges to developing therapeutics for these diseases include the diverse mechanisms of pathogenesis, some of which are still being debated and defined. Four small molecules that modulate the myosin motor protein in the cardiac sarcomere have shown great promise in the settings of HCM and DCM, regardless of the underlying genetic pathogenesis, and similar approaches are being developed to target other components of the sarcomere. In the setting of HCM, mavacamten and aficamten bind to the myosin motor and decrease the ATPase activity of myosin. In the setting of DCM, omecamtiv mecarbil and danicamtiv increase myosin activity in cardiac muscle (but omecamtiv mecarbil decreases myosin activity in vitro). In this Review, we discuss the therapeutic strategies to alter sarcomere contractile activity and summarize the data indicating that targeting one protein in the sarcomere can be effective in treating patients with genetic variants in other sarcomeric proteins, as well as in patients with non-sarcomere-based disease.

Survival Following Alcohol Septal Ablation or Septal Myectomy for Patients With Obstructive Hypertrophic Cardiomyopathy

BACKGROUND

There is little information regarding long-term mortality comparing the 2 most common procedures for septal reduction for obstructive hypertrophic cardiomyopathy (HCM), alcohol septal ablation (ASA), and septal myectomy.

OBJECTIVES

This study sought to compare the long-term mortality of patients with obstructive HCM following septal myectomy or ASA.

METHODS

We evaluated outcomes of 3,859 patients who underwent ASA or septal myectomy in 3 specialized HCM centers. All-cause mortality was the primary endpoint of the study.

RESULTS

In the study cohort, 585 (15.2%) patients underwent ASA, and 3,274 (84.8%) underwent septal myectomy. Patients undergoing ASA were significantly older (median age: 63.0 years [IQR: 52.7-72.8 years] vs 53.7 years [IQR: 44.9-62.8 years]; P < 0.001) and had smaller septal thickness (19.0 mm [IQR: 17.0-22.0 mm] vs 20.0 mm [IQR: 17.0-23.0 mm]; P = 0.007). Patients undergoing ASA also had more comorbidities, including renal failure, diabetes, hypertension, and coronary artery disease. There were 4 (0.7%) early deaths in the ASA group and 9 (0.3%) in the myectomy group. Over a median follow-up of 6.4 years (IQR: 3.6-10.2 years), the 10-year all-cause mortality rate was 26.1% in the ASA group and 8.2% in the myectomy group. After adjustment for age, sex, and comorbidities, the mortality remained greater in patients having septal reduction by ASA (HR: 1.68; 95% CI: 1.29-2.19; P < 0.001).

CONCLUSIONS

In patients with obstructive hypertrophic cardiomyopathy, ASA is associated with increased long-term all-cause mortality compared with septal myectomy. This impact on survival is independent of other known factors but may be influenced by unmeasured confounding patient characteristics.

Post-operative management of hypertrophic obstructive cardiomyopathy

Hypertrophic obstructive cardiomyopathy patients are at increased risk of sudden cardiac arrest due to dynamic left ventricular outflow tract obstruction, myocardial ischaemia and arrhythmias. Septal myectomy remains the gold standard therapy for patients with hypertrophic obstructive cardiomyopathy (HOCM) refractory to other therapy. This review comprehensively focuses on the post-operative management and complications of HOCM patients undergoing surgical correction. Although these patients are at risk of various perioperative complications from anaesthesia and surgery due to the underlying complexity of their disease, surgical myectomy is associated with excellent long-term outcomes if carried out in experienced centers.

Preintervention imaging and intraoperative management care of the hypertrophic obstructive cardiomyopathy patient

With an estimated overall mortality of less than 1 percent per year, hypertrophic cardiomyopathy, is the most common genetic cardiomyopathy. Intraoperative transesophageal echocardiography is the standard of care for assessing patients with hypertrophic obstructive cardiomyopathy undergoing surgical septal myectomy, allowing surgical planning, intraoperative hemodynamic monitoring, and postprocedural assessment of the repair, including detection of immediate complications. At various phases during surgical septal myectomy, the changing hemodynamic conditions may lead to worsening or improvement in left ventricle outflow tract obstruction by change in preload or afterload, systolic anterior motion of the mitral valve, or sympathetic stimulation. These characteristics represent unique challenges in the management of these patients, requiring a comprehensive understanding of the management of all the conditions required to decrease the left ventricle outflow tract gradient avoiding obstruction, which include the maintenance of sinus rhythm, adequate rate avoiding tachycardia and bradycardia, and avoidance of systemic hypotension preserving preload and afterload, with adequate vasoactive agents. The aim of this review is to summarize the perioperative assessment and management of patients undergoing hypertrophic obstructive myopathy surgery.

Propensity score matched comparison of isolated, elective aortic valve replacement with and without concomitant septal myectomy: is it worth it?

BACKGROUND

Septal myectomy during open aortic valve replacement (AVR) is an effective surgical treatment for asymmetric secondary basal septal hypertrophy. Concerns regarding higher rates of complications associated with this procedure have been raised - such as permanent pacemaker implantation. The aim of this study was to compare outcomes and complications of patients with and without concomitant septal myectomy using propensity score matching applied to a large, consecutive single center cohort.

METHODS

A total of 2199 consecutive patients undergoing either AVR with concomitant myectomy (AVR-M, N.=212) or AVR alone (N.=1987) were analyzed (2009-2015). Patients with previous cardiac or emergency surgery, concomitant cardiac procedures and endocarditis were excluded. As reference to previously published data, patient characteristics and outcomes of the overall cohort were examined and for comparison between groups propensity score matching utilized.

RESULTS

In the unmatched cohort, AVR-M patients were older (71.2±8 vs. 67.6±10 years, P<0.001) and more often female (68% vs. 37%, P<0.001) in comparison to patients receiving only AVR. After matching (N.=374) no significant difference in baseline features was evident. No significant difference in hospital mortality (2.1% vs. 1.6%, P=1.000) and pacemaker-implantation rate (5.3% vs. 3.7%, P=0.621) was observed. Mid-term survival was comparable between the two groups (86.1±5% vs. 84.4±5% after 6 years, P=0.957). The overall patient cohort showed a survival comparable to that of an adjusted regional normal population (P=0.178).

CONCLUSIONS

This study demonstrates that concomitant myectomy in patients undergoing AVR is a safe surgical technique resulting in comparable hospital mortality and mid-term survival. Concomitant septal myectomy seems not to be associated with an increased pacemaker implantation rate.

Comparison of expected and observed outcomes for septal myectomy in hypertrophic obstructive cardiomyopathy

BACKGROUND

Septal myectomy remains the criterion standard for treatment of symptomatic, medically refractory hypertrophic cardiomyopathy (HCM). There is no specific surgical risk calculator for septal myectomy.

METHODS

This study compares the outcomes of septal myectomy at a tertiary referral center with predicted outcomes of mitral valve (MV) repair and aortic valve replacement (AVR) using the Society of Thoracic Surgeons Adult Cardiac Surgery Risk Calculator (STS Calculator). A total of 298 consecutive patients with HCM underwent isolated septal myectomy from 2011 to 2014. Observed outcomes of septal myectomy were compared with the STS Calculator predicted risk of isolated MV repair and AVR predicted within this population using 1-sample tests of proportions.

RESULTS

Thirty-day mortality for myectomy in this cohort was zero. STS Calculator predicted risk of mortality for MV repair was 0.7% (P = .14) and for AVR = 1.1% (P = .06). Follow-up for vital status was 6.0 ± 0.7 years, at which 294 (98.7%) patients were alive. Hospital stay length was 4.9 ± 1.9 days. One (0.3%) patient experienced a postoperative deep sternal wound infection, and 1 (0.3%) patient experienced a prolonged ventilated state. Postoperative atrial fibrillation occurred in 64 (21.5%) patients. During 30 days of follow-up, no patients experienced stroke, renal failure, or needed dialysis.

CONCLUSIONS

Septal myectomy, performed in a tertiary referral center, had a 30-day mortality rate of 0% and low morbidity rate. There was no difference between observed myectomy mortality and STS Calculator predicted risk for AVR and MV repair. It is possible that a larger sample could reveal lower mortality than STS prediction.

Hypertrophic obstructive cardiomyopathy: the Mayo Clinic experience

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is a primary myocardial disease characterized by left ventricular hypertrophy in the absence of other etiologies. Clinical presentation may vary from asymptomatic to sudden cardiac death. Medical treatment is the first-line therapy for symptomatic patients. Extended left ventricular septal myectomy is the procedure of choice if medical treatment is unsuccessful or intolerable.

MAYO CLINIC EXPERIENCE

More than 3,000 patients have had septal myectomy for HCM at the Mayo Clinic (MN, USA) from 1993 to 2016. Risk of hospital death after isolated septal myectomy for obstructive HCM is <1% and is similar to the risk of operation for elective mitral valve repair. Complications, such as complete heart block requiring permanent pacemaker, are uncommon (2%), although partial or complete left bundle branch block is a frequent finding on the postoperative ECG. Relief of left ventricular outflow tract (LVOT) obstruction with septal myectomy dramatically improves symptoms and exercise capacity in symptomatic patients with obstructive HCM. More than 90% of severely symptomatic patients have improvement by at least two functional classes, and reduction of outflow gradients by myectomy decreases or eliminates symptoms of dyspnea, angina and/or syncope. Basal obstruction with systolic anterior motion (SAM) is treated by transaortic myectomy. The transapical approach was applied in 115 patients with obstructive midventricular and apical variants of HCM between 1993 and 2012. All patients with midventricular obstruction had gradient relief and none developed an apical aneurysm or ventricular septal defect. Recurrent obstruction after satisfactory myectomy was rare.

CONCLUSIONS

Septal myectomy effectively and definitively relieves LVOT obstruction and cardiac symptoms in patients with obstructive HCM. In experienced centers, early mortality for isolated septal myectomy is less than 1%, and overall results are excellent and continue to improve in the current era.

Outcomes of an extended Morrow procedure without a concomitant mitral valve procedure for hypertrophic obstructive cardiomyopathy

The indications for a concomitant mitral valve (MV) procedure remain controversial for patients with hypertrophic obstructive cardiomyopathy (HOCM). According to previous studies, a concomitant MV surgery was required in 11–20% of inpatient operations. Thus, we aimed to study the outcomes of an extended Morrow procedure without a concomitant MV procedure for HOCM patients who had no intrinsic abnormalities of the MV apparatus. We retrospectively reviewed 232 consecutive HOCM patients who underwent extended Morrow procedures from January 2010 to October 2014. Only 10 (4.31%) patients with intrinsic MV diseases underwent concomitant MV procedures. Of the 232 patients, 230 had no to mild mitral regurgitation (MR) postoperatively. We separated the 232 patients into two groups according to preoperative MR degree. One group is mild MR, and the other is moderate or severe MR. The three-month, one-year, and three-year composite end-point event-free survival rates had no difference between two groups (p = 0.820). When we separated the patients to postoperative no or trace MR group and mild MR group, there was also no difference on survival rates (p = 0.830). In conclusion, concomitant mitral valve procedures are not necessary for HOCM patients with MR caused by systolic anterior motion, even moderate to severe extent.

Long-term clinical and echocardiographic outcomes of extensive septal myectomy for hypertrophic obstructive cardiomyopathy in Chinese patients

Background

There has been limited data addressing outcomes of extensive septal myectomy in Chinese patients with hypertrophic obstructive cardiomyopathy (HOCM). In this study, the objective was to evaluate the clinical and echocardiographic outcomes of extensive septal myectomy in a relative large number of Chinese HOCM patients over long-term follow-up.

Methods

We retrospectively studied 139 consecutive HOCM patients (age 43 ± 15 years, 37 % male) who underwent extensive left ventricular septal myectomy. During the perioperative period, all patients were examined by echocardiography. All-cause death and cardiac death were considered as primary endpoints during follow-up. Perioperative data was obtained by retrospective review of institutional surgical databases. Follow-up data of echocardiography and clinical status was recorded through outpatient interview.

Results

Perioperative events consisted of arrhythmia, retraction injury to aortic valve leaflets, pleural effusion, and hemodialysis and the use of intra-aortic balloon pump. There was no in-hospital mortality. The follow-up period averaged 5.6 ± 0.9 years and overall survivals were 100.0, 99.3, 99.3, 98.5 and 97.8 % at 1, 2, 3, 4 and 5 years, respectively. Left ventricular outflow tract (LVOT) gradient decreased form preoperative 84 ± 17 mmHg to 12 ± 3 mmHg at 2.5 years after surgery and it further reduced to 6 ± 3 mmHg at 5 years after surgery (P < 0.05). Compared with the preoperative levels, interventricualr septal thickness decreased by 32 % while diastole left ventricular inner diameter approximately increased by 10 % and ejection fraction (EF) was significantly elevated during follow-up (P < 0.05). By echocardiography detection, mitral regurgitation was ameliorated for HOCM patients after surgery. There was significant improvement in New York Heart Association (NYHA) class. The proportion of NYHA III and IV decreased from preoperative 58 to 19 % at 2.5 years after surgery and it reduced to 11 % at 5 years after operation.

Conclusion

Extensive septal myectomy offers minimal operative risk and provides long-term relief for LVOT obstruction in Chinese HOCM patients.

Minimally invasive septal myectomy for the treatment of hypertrophic obstructive cardiomyopathy and intrinsic mitral valve disease

OBJECTIVE

Transaortic left ventricular septal myectomy described by Morrow is a classical procedure for the treatment of systolic anterior motion of the mitral apparatus associated with hypertrophic obstructive cardiomyopathy (HOCM). We aimed to review our results of transmitral septal myectomy and mitral valve repair/replacement in patients with intrinsic mitral valve disease associated with HOCM, operated on through a minimally invasive approach.

METHODS

Between 2005 and 2014, 19 patients [7 men (37%); mean (SD) age, 69.4 (14.5) years] were treated with minimally invasive approach for degenerative mitral regurgitation and HOCM. Preoperative peak left ventricular outflow tract (LVOT) gradient was 66 (24) mm Hg. Severe mitral regurgitation was diagnosed in 16 cases (84%). New York Heart Association functional class III to IV heart failure was present in 13 patients (68%).

RESULTS

Fifteen patients (79%) underwent mitral valve replacement, and four patients (21%) underwent mitral valve repair. Left ventricular outflow tract obstruction was corrected directly in all patients via the mitral valve with septal myectomy/myotomy, avoiding aortotomy in majority of the patients. No significant prolongation of extracorporeal circulation/aortic cross-clamping times was observed (P = 0.41 and P = 0.67, respectively) when compared with a similar population without HOCM. No iatrogenic ventricular septal defect developed in treated patients. No hospital mortality occurred. Resting LVOT gradient reduced at discharge to 13 (22) mm Hg (P = 0.025).

CONCLUSIONS

Transmitral left ventricular septal myectomy in patients with degenerative mitral valve disease is quite a simple, feasible, and effective technique and does not require aortotomy in most cases. It can be performed with low early mortality and satisfactory resolution of LVOT obstruction in a minimally invasive setting.

Surgery for hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a genetically determined cardiac disease characterised by otherwise unexplained myocardial hypertrophy of the left ventricle, and may result in left ventricular outflow tract obstruction. It is the most common cause of sudden cardiac death in young adults due to arrhythmias. Septal myectomy is a surgical treatment for HCM with moderate to severe outflow tract obstruction, and is indicated for patients with severe symptoms refractory to medical therapy. The surgical approach involves obtaining access to the interventricular septum via transaortic, transapical or transmitral approaches, and excising a portion of the hypertrophied myocardium to relieve the outflow tract obstruction. Large, contemporary series from centres experienced in septal myectomy patients have demonstrated a low early mortality of <2 %, excellent long-term survival that matches the general population, and durable relief of symptoms.