Hypertrophic cardiomyopathy in 2013: Current speculations and future perspectives

Hypertrophic cardiomyopathy (HCM), the most variable cardiac disease in terms of phenotypic presentation and clinical outcome, represents the most common inherited cardiomyopathic process with an autosomal dominant trait of inheritance. To date, more than 1400 mutations of myofilament proteins associated with the disease have been identified, most of them “private” ones. This striking allelic and locus heterogeneity of the disease certainly complicates the establishment of phenotype-genotype correlations. Additionally, topics pertaining to patients’ everyday lives, such as sudden cardiac death (SCD) risk stratification and prevention, along with disease prognosis, are grossly related to the genetic variation of HCM. This review incorporates contemporary research findings and addresses major aspects of HCM, including preclinical diagnosis, genetic analysis, left ventricular outflow tract obstruction and SCD. More specifically, the spectrum of genetic analysis, the selection of the best method for obstruction alleviation and the need for a unique and accurate factor for SCD risk stratification are only some of the controversial HCM issues discussed. Additionally, future perspectives concerning HCM and myocardial ischemia, as well as atrial fibrillation, are discussed. Rather than enumerating clinical studies and guidelines, challenging problems concerning the disease are critically appraised by this review, highlighting current speculations and recommending future directions.     

WJC 6~th Anniversary Special Issues(3):Cardiomyopathy Hypertrophic cardiomyopathy in 2013:Current speculations and future perspectives

Hypertrophic cardiomyopathy(HCM),the most variable cardiac disease in terms of phenotypic presentation and clinical outcome,represents the most common inherited cardiomyopathic process with an autosomal dominant trait of inheritance.To date,more than 1400 mutations of myofilament proteins associated with the disease have been identified,most of them "private" ones.This striking allelic and locus heterogeneity of the disease certainly complicates the establishment of phenotype-genotype correlations.Additionally,topics pertaining to patients' everyday lives,such as sudden cardiac death(SCD)risk stratification and prevention,along with disease prognosis,are grossly related to the genetic variation of HCM.This review incorporates contemporary research findings and addresses major aspects of HCM,including preclinical diagnosis,genetic analysis,left ventricular outflow tract obstruction and SCD.More specifically,the spectrum of genetic analysis,the selection of the best method for obstruction alleviation and the need for a unique and accuratefactor for SCD risk stratification are only some of the controversial HCM issues discussed.Additionally,future perspectives concerning HCM and myocardial ischemia,as well as atrial fibrillation,are discussed.Rather than enumerating clinical studies and guidelines,challenging problems concerning the disease are critically appraised by this review,highlighting current speculations and recommending future directions.     

Long‐term outcomes for different surgical strategies to treat left ventricular outflow tract obstruction in hypertrophic cardiomyopathy

Aims

Surgical intervention is used to treat dynamic left ventricular outflow tract obstruction (LVOTO) in hypertrophic cardiomyopathy. This study assesses the effect of different surgical strategies on long‐term mortality and morbidity.

Methods and results

In total, 347 patients underwent surgical intervention for LVOTO (1988–2015). Group A (n = 272) underwent septal myectomy; Group B (n = 33), septal myectomy and mitral valve (MV) repair; Group C (n = 22), myectomy and MV replacement; and Group D (n = 20), MV replacement alone. Median follow‐up was 5.2 years (interquartile range 1.9–7.9). The mean resting LVOT gradient improved post‐operatively from 71.9 ± 39.6 mmHg to 13.4 ± 18.5 mmHg (P < 0.05). Overall, 72.4% of patients improved by >1 New York Heart Association (NYHA) class; 58.9% of patients undergoing MV replacement alone did not improve their NYHA class. There were 5 perioperative deaths and 20 late deaths (>30 days). Survival rates at 1, 5 and 10 years respectively were 98.4, 96.9, 91.9% in Group A; 97.0, 92.4, 61.6% in Group B; 100.0, 100.0, 55.6% in Group C; and 94.7, 85.3, 85.3% in Group D (log‐rank, P < 0.05). Long‐term (>30 days) complications included atrial fibrillation (29.6%), transient ischaemic attack/stroke (2.4%) and heart failure hospitalisation (3.2%). There were 16 repeat surgical interventions at 3.0 years.

Conclusion

Septal myectomy is a safe procedure resulting in symptomatic improvement in the majority of patients. The annual incidence of non‐fatal disease‐related complications after surgical treatment of LVOTO is relatively high. Patients who underwent MV replacements had poorer outcomes with less symptomatic benefit in spite of a similar reduction in LVOT gradients.

     

血管紧张素原基因多态性与肥厚型心肌病的相关性分析

目的 探讨血管紧张素原(AGT)基因的单核苷酸多态性(SNP)位点A943580G与肥厚型心肌病(HCM)的相关性.方法 用PCR-RFLP方法对225个HCM病人和243个正常人的AGT的SNP位点A943580G进行基因分型(此位点与黑色人种中的高血压病人的最大早期充盈速度有关).结果 携带AA和AG基因型的HCM病人的左心室流出道梗阻率明显高于GG基因型的梗阻率(30.1%比17.0%,P＜0.05).通过对发病年龄,性别,室间隔厚度,HCM家族史以及家族猝死史进行调整后,携带A等位基因(AA AG)的HCM病人左心室流出道梗阻率要高于GG基因型病人(OR=2.4,95%CI 1.2 to 4.8).结论 AGT的A等位基因可能是HCM病人发生左心室流出道梗阻的危险因子.     

Right ventricular involvement in hypertrophic cardiomyopathy: Patterns and implications

Although hypertrophic cardiomyopathy (HCM) is the most common inherited cardiomyopathy worldwide, the criteria for its definition and most of the literature concern the left ventricle, thus confirming the theory that the right ventricle is the neglected one. Right ventricular (RV) involvement includes structural and functional changes with significant impact on clinical presentation and prognosis. The pattern of RV hypertrophy can be variable with possible dynamic obstruction. Histological findings suggest similar pathogenetic changes in both ventricles supporting the common myopathic process with sarcomeric mutations. Systolic dysfunction of the RV is subtle, and the classical echocardiographic indices are usually within normal limits, while global longitudinal strain is significantly impaired. Diastolic dysfunction of the RV is also evident in patients with HCM possibly due to fibrosis of the RV free wall and/or the obstruction of the RV filling with significant prognostic implications. RV involvement in HCM is associated with increased incidence of supraventricular and ventricular arrhythmias, severe dyspnea, pulmonary thromboembolism, progressive heart failure, and increased risk of sudden cardiac death. Therefore, the RV should be routinely included in the detailed assessment of patients with HCM.     

Mitral valve abnormalities in decedents of sudden cardiac death due to hypertrophic cardiomyopathy and idiopathic left ventricular hypertrophy

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A novel approach in the use of radiofrequency catheter ablation of septal hypertrophy in hypertrophic obstructive cardiomyopathy

ObjectiveAlcohol septal ablation (ASA) is a therapeutic alternative to surgical myectomy in patients with hypertrophic obstructive cardiomyopathy (HOCM). However, the anatomical variability of the septal branch, risk of complete heart block, and late onset ventricular arrhythmias are limitations to its therapeutic usage. There is recent interest in the use of radiofrequency catheter ablation (RFCA) as a therapeutic option in HOCM. We aimed to assess the safety and efficacy of RFCA in the treatment of symptomatic HOCM.MethodsSeven patients with symptomatic HOCM (mean age 43.7 ± 15.6 years, five males), and significant left ventricular outflow tract (LVOT) gradient despite optimal drug therapy, underwent ablation of the hypertrophied interventricular septum. These patients had unfavorable anatomy for ASA. Ablation was performed under 3D electro-anatomical system guidance using an open irrigated tip catheter. The region of maximal LV septal bulge as seen on intracardiac echocardiography was targeted. Patients were followed up at 1, 6, and 12 months post-procedure.ResultsThe mean baseline LVOT gradient by Doppler echocardiography was 81 ± 14.8 mm of Hg which reduced to 48.5 ± 22.6 (p = 0.0004), 49.8 ± 19.3 (p = 0.0004), and 42.8 ± 26.1 mm of Hg (p = 0.05) at 1, 6, and 12 months respectively. Symptoms improved at least by one NYHA class in all but one patient. One patient developed transient pulmonary edema post-RFA. There were no other complications.ConclusionRFCA of the hypertrophied septum causes sustained reduction in the LVOT gradient and symptomatic improvement among patients with HOCM. Electroanatomical mapping helps to perform the procedure safely.     

Cardiac index: A superior parameter of cardiac function than left ventricular ejection fraction in risk stratification of hypertrophic cardiomyopathy

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Mitral valve remodeling in the development of obstructive hypertrophic cardiomyopathy

Approximately 2/3 of patients with hypertrophic cardiomyopathy (HCM) have significant left ventricular outflow tract obstruction (LVOTO), which is caused by the interaction mitral valve apparatus and the hypertrophied septum. The contribution of mitral valve remodeling to the development of obstruction over time has never been described. We analyzed retrospectively 40 patients with HCM and no baseline obstruction followed up for a median of 2179 days. At follow up, 13 patients developed significant LVOTO. Patients who developed LVOTO had longer posterior leaflets and longer anterior leaflet residual length.     

Long term exercise capacity in patients with hypertrophic cardiomyopathy treated with percutaneous transluminal septal myocardial ablation

BACKGROUND: In hypertrophic obstructive cardiomyopathy, percutaneous transluminal septal myocardial ablation (PTSMA) improves functional capacity in the short term. However, long term functional capacity is unknown. AIM: To assess the long term exercise capacity of patients with hypertrophic obstructive cardiomyopathy undergoing PTSMA. METHODS: Twenty three patients (56.5% male, mean age 44.5+/-13.6 years) who underwent PTSMA were included. All patients had also undergone a symptom limited cardiopulmonary exercise treadmill test before the procedure, then after 3 months (early follow-up) and after a mean 7.2+/-1.0 years (long term follow-up). RESULTS: Before PTSMA, mean maximal pressure gradient in the left outflow tract (LVOTGmax) was 82+/-29 mmHg, 17 patients had NYHA functional class> or = III and peak oxygen uptake (pVO2) was 18+/-4 ml/kg/min. PTSMA led to a reduction in mean LVOTGmax (to 29+/-19 mmHg, p<.0001), improvement of heart failure symptoms (NYHA> or =III in 1 patient, p<.0001) and an increase of pVO2 (to 22+/-6 ml/kg/min, p=.0002) at short term. LVOTGmax, functional class and pVO2 did not change significantly during long term follow-up compared to early follow-up. However, there was a continuous improvement in percentage predicted pVO2 over time. CONCLUSIONS: In patients with hypertrophic obstructive cardiomyopathy and symptoms of heart failure, PTSMA leads to stable long term improvement of objectively measured exercise capacity.     

Inducibility of life-threatening ventricular arrhythmias is related to maximum left ventricular thickness and clinical markers of sudden cardiac death in patients with hypertrophic cardiomyopathy attributable to the Asp175Asn mutation in the alpha-tropomyosin gene

We investigated inducibility of life-threatening arrhythmias with programmed ventricular stimulation (PVS) in relation to clinical markers of sudden cardiac death (SCD) in subjects with hypertrophic cardiomyopathy (HCM) attributable to the Asp175Asn mutation in the α-tropomyosin gene (TPM1-Asp175Asn). PVS was performed with up to three extrastimuli and distribution of markers of SCD was evaluated in 21 adult subjects with the TPM1-Asp175Asn. Sustained polymorphic ventricular tachycardia (VT) or ventricular fibrillation (VF) was induced in seven of 21 subjects (33%). Inducible subjects had more severe left ventricular hypertrophy (LVH) and an increased number of markers of SCD (family history of SCD, syncope or presyncope, fall in systolic blood pressure (BP) during exercise, documented non-sustained VT (NSVT), and marked LVH) compared to non-inducible subjects (IVS 2.4 ± 0.3 cm vs. 1.6 ± 0.5 cm, P < 0.001; and two to three vs. one to two markers of SCD, P = 0.007, respectively). In conclusion, in HCM attributable to the Asp175Asn mutation in the α-tropomyosin gene, life-threatening arrhythmias were induced in one third of the patients. Inducibility was associated with the maximum left ventricular (LV) thickness and the number of markers of SCD, suggesting that in HCM patients with an identical causative mutation, susceptibility to ventricular arrhythmias is related to the cardiomyopathic phenotype.     

Syncope in hypertrophic cardiomyopathy: mechanisms and consequences for treatment.

Hypertrophic cardiomyopathy (HCM) is an inherited disease with marked phenotypic variability that includes the extent of hypertrophy, the presence and severity of symptoms, and the natural history of the disease. Symptoms of impaired consciousness (syncope and pre-syncope) occur in approximately 15-25% of patients with hypertrophic cardiomyopathy (HCM). In young patients a history of recurrent syncope is associated with an increased risk of sudden death. Detailed investigations identify a probable mechanism in a minority of these, usually paroxysmal atrial fibrillation or ventricular tachycardia. In the majority, however, no likely mechanism is found despite extensive investigation. Although this may be the case, it is still of vital importance to exclude potentially treatable causes of syncope.     

Sudden cardiac death in patients with nonischemic cardiomyopathy

Sudden cardiac death (SCD) is an important cause of mortality worldwide. Although SCD is most often associated with coronary heart disease, the risk of SCD in patients without ischemic heart disease is well-established. Nonischemic cardiomyopathies, including idiopathic dilated cardiomyopathy, hypertrophic cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy represent three unique disease entities that have been shown to be highly associated with SCD and ventricular arrhythmias. A variety of risk stratification tools have been investigated, although the optimal strategy remains unknown. Identification of the arrhythmogenic substrate and treatment of ventricular arrhythmias in these subgroups can be challenging. Herein, we aim to discuss the current understanding of the anatomic and electrophysiologic substrate underlying ventricular arrhythmias and highlight features that may be associated with a higher risk of SCD in these 3 conditions.