Guide Diagnosis and Management of Hypertrophic Cardiomyopathy

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Your doctor is likely to recommend an imaging test called an echocardiogram to diagnose hypertrophic cardiomyopathy. This test allows your.
Table of contents

Alice K. The recommendations listed in this document are, whenever possible, evidence based. An extensive evidence review was conducted through January Searches were limited to studies, reviews, and other evidence conducted in human subjects and published in English. Key search words included, but were not limited to, hypertrophic cardiomyopathy HCM , surgical myectomy, ablation, exercise, sudden cardiac death SCD , athletes, dual-chamber pacing, left ventricular outflow tract LVOT obstruction, alcohol septal ablation, automobile driving and implantable cardioverter-defibrillators ICDs , catheter ablation, defibrillators, genetics, genotype, medical management, magnetic resonance imaging, pacing, permanent pacing, phenotype, pregnancy, risk stratification, sudden death in athletes, surgical septal myectomy, and septal reduction.

References selected and published in this document are representative and not all-inclusive. To provide clinicians with a comprehensive set of data, whenever deemed appropriate or when published, the absolute risk difference and number needed to treat or harm are provided in the guideline, along with confidence intervals and data related to the relative treatment effects, such as odds ratio, relative risk, hazard ratio, or incidence rate ratio.

The committee was composed of physicians and cardiac surgeons with expertise in HCM, invasive cardiology, noninvasive testing and imaging, pediatric cardiology, electrophysiology, and genetics. All information on reviewers' RWI was distributed to the writing committee and is published in this document Appendix 2. Although there are reports of this disease dating back to the s, the first modern pathologic description was provided over 50 years ago by Teare 2 and the most important early clinical report by Braunwald et al in The impetus for the guideline is based on an appreciation of the frequency of this clinical entity and a realization that many aspects of clinical management, including the use of diagnostic modalities and genetic testing, lack consensus.

Moreover, the emergence of 2 different approaches to septal reduction therapy septal myectomy and alcohol septal ablation in addition to the ICD has created considerable controversy. The discussion and recommendations about the various diagnostic modalities apply to patients with established HCM and to a variable extent to patients with a high index of suspicion of the disease. Although the Task Force was aware of the lack of high levels of evidence regarding HCM provided by clinical trials, it was believed that a guideline document based on expert consensus that outlines the most important diagnostic and management strategies would be helpful.

To facilitate ease of use, it was decided that recommendations in the pediatric and adolescent age groups would not appear as a separate section but instead would be integrated into the overall content of the guideline where relevant. HCM is a common genetic cardiovascular disease. In addition, HCM is a global disease, 4 with epidemiological studies from several parts of the world 5 reporting a similar prevalence of left ventricular LV hypertrophy, the quintessential phenotype of HCM, to be about 0.

Although HCM is the preferred nomenclature to describe this disease, 7 confusion over the names used to characterize the entity of HCM has arisen over the years. In fact, fully one third of patients have no obstruction either at rest or with physiologic provocation.

The generally accepted definition of HCM, the clinical entity that is the subject of this guideline, is a disease state characterized by unexplained LV hypertrophy associated with nondilated ventricular chambers in the absence of another cardiac or systemic disease that itself would be capable of producing the magnitude of hypertrophy evident in a given patient, 6 , 7 , 9 — 12 with the caveat that patients who are genotype positive may be phenotypically negative without overt hypertrophy.

In terms of LV wall-thickness measurements, the literature at this time has been largely focused on echocardiography, although cardiovascular magnetic resonance CMR is now used with increasing frequency in HCM, 15 and we presume that data with this latter modality will increasingly emerge.

However, it should be underscored that in principle, any degree of wall thickness is compatible with the presence of the HCM genetic substrate and that an emerging subgroup within the broad clinical spectrum is composed of family members with disease-causing sarcomere mutations but without evidence of the disease phenotype ie, LV hypertrophy. In older patients with LV hypertrophy and a history of systemic hypertension, coexistence of HCM is often a consideration. The important distinction between pathologic LV hypertrophy ie, HCM and physiologic LV hypertrophy ie, athlete's heart is impacted by the recognition that athletic conditioning can produce LV, right ventricular, and left atrial LA chamber enlargement, ventricular septal thickening, and even aortic enlargement 26 but is often resolved by noninvasive markers, including sarcomeric mutations or family history of HCM, LV cavity dimension if enlarged, favoring athlete's heart , diastolic function, pattern of LV hypertrophy if unusual location or noncontiguous, favoring HCM , or short deconditioning periods in which a decrease in wall thickness would favor athlete's heart.

In addition, differential diagnosis of HCM may require distinction from systemic hypertension or physiologic athlete's heart 23 or from dilated cardiomyopathy when HCM presents in the end stage. Figure 1. Summary of the nomenclature that distinguishes HCM from other genetic diseases associated with LV hypertrophy. However, it is possible that in the future other nonsarcomeric but also nonmetabolic genes may prove to cause HCM.

Modified with permission from Maron et al. On the basis of the genotype-phenotype data available at this time, HCM is regarded here as a disease entity caused by autosomal dominant mutations in genes encoding protein components of the sarcomere and its constituent myofilament elements. The current weight of evidence supports the view that the vast majority of genes and mutations responsible for clinically diagnosed HCM encode proteins within and associated with the sarcomere, accounting in large measure for those patients described in the voluminous amount of HCM literature published over 50 years.

In conclusion, the writing committee believes that the most prudent recommendation for nomenclature is that hypertrophic cardiomyopathy and the acronym HCM remain a clinical diagnosis limited to those patients in whom 1 overt disease expression with LV hypertrophy appears to be confined to the heart and 2 the definitive mutation is either one of a gene encoding proteins of the cardiac sarcomere or alternatively when the genotype is unresolved using current genetic testing.

The writing committee considers it important to emphasize that HCM is a complex disease entity with a broad and increasing clinical and genetic spectrum. Another advantage is the potential to perform outcomes research on large groups of patients. Although the writing committee does not necessarily recommend that all patients with HCM should be evaluated in such centers, nevertheless, it is the strong view that patients with this disease may well benefit from a clinical environment with specific expertise in HCM. The selection of patients for referral to an HCM center should be based largely on the judgment of the managing cardiologist and the degree to which he or she is comfortable advising and evaluating patients with HCM with a particular clinical profile.

HCM is a heterogeneous cardiac disease with a diverse clinical presentation and course, presenting in all age groups from infancy to the very elderly. Heart failure characterized by exertional dyspnea with or without chest pain that may be progressive despite preserved systolic function and sinus rhythm, or in a small proportion of patients, heart failure may progress to the end stage with LV remodeling and systolic dysfunction caused by extensive myocardial scarring.

AF, either paroxysmal or chronic, also associated with various degrees of heart failure 60 and an increased risk of systemic thromboembolism and both fatal and nonfatal stroke. Figure 2.

Diagnosis and Management of Hypertrophic Cardiomyopathy

Prognosis profiles for HCM and targets for therapy. AF indicates atrial fibrillation. The natural history of HCM can be altered by a number of therapeutic interventions: ICDs for secondary or primary prevention of sudden death in patients with risk factors 54 — 56 ; drugs appropriate to control heart failure symptoms principally those of exertional dyspnea and chest discomfort , 9 , 10 surgical septal myectomy 61 or alcohol septal ablation 62 for progressive and drug-refractory heart failure caused by LVOT obstruction; heart transplantation for systolic or less frequently intractable diastolic dysfunction associated with severe unrelenting symptoms 39 ; and drug therapy or possibly radiofrequency ablation or surgical maze procedure for AF.

The pathophysiology of HCM is complex and consists of multiple interrelated abnormalities, including LVOT obstruction, diastolic dysfunction, mitral regurgitation, myocardial ischemia, and arrhythmias.

Introduction

The original observations by Brock 68 and Braunwald et al 3 emphasized the functional subvalvular LVOT gradient, which was highly influenced by alterations in the load and contractility of the left ventricle. The clinical significance of the outflow tract gradient has periodically been controversial, 69 — 72 but careful studies have shown definitively that true mechanical obstruction to outflow does occur.

Hypertrophic Cardiomyopathy: Guide to Understanding the Condition

Throughout the remainder of this document the term gradient will be used to denote peak instantaneous gradient. Table 2. Obstruction causes an increase in LV systolic pressure, which leads to a complex interplay of abnormalities including prolongation of ventricular relaxation, elevation of LV diastolic pressure, mitral regurgitation, myocardial ischemia, and a decrease in forward cardiac output.

Although the mechanism of the outflow tract gradient in HCM was initially thought to be caused by systolic contraction of the hypertrophied basal ventricular septum encroaching on the LVOT, most recent studies emphasize that during ventricular systole, flow against the abnormally positioned mitral valve apparatus results in drag force on a portion of the mitral valve leaflets, which pushes the leaflets into the outflow tract. Obstruction to LV outflow is dynamic, varying with loading conditions and contractility of the ventricle.


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Patients may have little or no obstruction of the LVOT at rest but can generate large LVOT gradients under conditions such as exercise, the strain phase of the Valsalva maneuver, or during pharmacologic provocation. Importantly, it has been well established that LVOT obstruction contributes to the debilitating heart failure—related symptoms that may occur in HCM 66 , 67 and is also a major determinant of outcome.

References

The presence and magnitude of outflow obstruction are usually assessed with 2-dimensional echocardiography and continuous wave Doppler. It is a late-peaking systolic velocity that reflects the occurrence of subaortic obstruction late in systole, and the peak instantaneous gradient derived from the peak velocity should be reported. However in equivocal cases, cardiac catheterization with isoproterenol infusion may further aid in eliciting a provocable gradient.

Diastolic dysfunction arising from multiple factors is a major pathophysiologic abnormality in HCM that ultimately affects both ventricular relaxation and chamber stiffness. Severe hypertrophy of the myocardium results in an increase in chamber stiffness. Diffuse myocardial ischemia may further affect both relaxation and chamber stiffness. A compensatory increase in the contribution of late diastolic filling during atrial systole is associated with these alterations.

Severe myocardial ischemia and even infarction may occur in HCM. Patients with HCM of any age have increased oxygen demand caused by the hypertrophy and adverse loading conditions. They also have compromised coronary blood flow to the LV myocardium because of intramural arterioles with thickened walls attributable to medial hypertrophy associated with luminal narrowing. It is speculated that autonomic dysregulation 88 is present in patients with HCM and that the fall in blood pressure associated with bradycardia may be an abnormal reflex response to obstruction.

Mitral regurgitation is common in patients with LVOT obstruction and may play a primary role in producing symptoms of dyspnea. The temporal sequence of events of eject-obstruct-leak supports the concept that the mitral regurgitation in most patients is a secondary phenomenon.

Hypertrophic cardiomyopathy (HCM) - Cardiomyopathy UK

The jet of mitral regurgitation is directed laterally and posteriorly and predominates during mid and late systole. An anteriorly directed jet should suggest an intrinsic abnormality of the mitral valve. If the mitral regurgitation is caused by distortion of leaflet motion by SAM of the mitral valve, the severity of the mitral regurgitation may be proportional to the LVOT obstruction in some patients.

Changes in ventricular load and contractility that affect the severity of outflow tract obstruction similarly affect the degree of mitral regurgitation.

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It is important to identify patients with additional intrinsic disease of the mitral valve apparatus prolapse or flail , because this finding influences subsequent treatment options. The clinical diagnosis of HCM is conventionally made with cardiac imaging, at present most commonly with 2-dimensional echocardiography and increasingly with CMR.

Genetic testing, which is now commercially available, is a powerful strategy for definitive diagnosis of affected genetic status and is currently used most effectively in the identification of affected relatives in families known to have HCM. Class I Evaluation of familial inheritance and genetic counseling is recommended as part of the assessment of patients with HCM. Patients who undergo genetic testing should also undergo counseling by someone knowledgeable in the genetics of cardiovascular disease so that results and their clinical significance can be appropriately reviewed with the patient.

Screening clinical, with or without genetic testing is recommended in first-degree relatives of patients with HCM.