hypertrophic cardiomyopathy

肥大型心筋症 HCM

WordNet

1. a disorder (usually of unknown origin) of the heart muscle (myocardium) (同)myocardiopathy

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/05/09 21:50:12」(JST)

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Hypertrophic cardiomyopathy
Illustration of Hypertrophic Cardiomyopathy
Classification and external resources
ICD-10	I42.1–I42.2
ICD-9	425.4
OMIM	192600
DiseasesDB	6373
MedlinePlus	000192
eMedicine	med/290 ped/1102 radio/129
Patient UK	Hypertrophic cardiomyopathy
MeSH	D002312

Not to be confused with dilated cardiomyopathy or any other cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is a primary disease of the myocardium (the muscle of the heart) in which a portion of the myocardium is hypertrophied (thickened) without any obvious cause, creating functional impairment of the cardiac muscle. It is a leading cause of sudden cardiac death in young athletes. The occurrence of hypertrophic cardiomyopathy is a significant cause of sudden unexpected cardiac death in any age group and as a cause of disabling cardiac symptoms. Younger people are likely to have a more severe form of hypertrophic cardiomyopathy.

HCM is frequently asymptomatic until sudden cardiac death, and for this reason some suggest routinely screening certain populations for this disease.

A cardiomyopathy is a disease that affects the muscle of the heart. With HCM, the myocytes (cardiac contractile cells) in the heart increase in size, which results in the thickening of the heart muscle. In addition, the normal alignment of muscle cells is disrupted, a phenomenon known as myocardial disarray. HCM also causes disruptions of the electrical functions of the heart. HCM is most commonly due to a mutation in one of 9 sarcomeric genes that results in a mutated protein in the sarcomere, the primary component of the myocyte (the muscle cell of the heart). These are predominantly single-point missense mutations in the genes for beta-myosin heavy chain (MHC), myosin-binding protein C, cardiac troponinT, or tropomyosin. These mutations cause myofibril and myocyte structural abnormalities and possible deficiencies in force generation.

While most literature so far focuses on European, American, and Japanese populations, HCM appears in all racial groups. The prevalence of HCM is about 0.2% to 0.5% of the general population.

Signs and symptoms

The clinical course of HCM is variable. Many patients are asymptomatic or mildly symptomatic. The symptoms of HCM include dyspnea (shortness of breath) due to stiffening and decreased blood filling of the ventricles, exertional chest pain (sometimes known as angina) due to reduced or restricted blood flow to the coronary arteries, uncomfortable awareness of the heart beat (palpitations) due to the aforementioned ischemia, as well as disruption of the electrical system running through the abnormal heart muscle, lightheadedness, fatigue, fainting (called syncope) and sudden cardiac death. As mentioned, Dyspnea is largely due to increased stiffness of the left ventricle, which impairs filling of the ventricles, but also leads to elevated pressure in the left ventricle and left atrium, causing back pressure and interstitial congestion in the lungs. Symptoms are not closely related to the presence or severity of an outflow tract gradient. Often, symptoms mimic those of congestive heart failure (esp. activity intolerance & dyspnea), but treatment of each is different. Beta blockers are used in both cases, but treatment with diuretics, a mainstay of CHF treatment, will exacerbate symptoms in hypertrophic obstructive cardiomyopathy by decreasing ventricular preload volume and thereby increasing outflow resistance (less blood to push aside the thickened obstructing tissue).

Major risk factors for sudden death in individuals with HCM include prior history of cardiac arrest or ventricular fibrillation, spontaneous sustained ventricular tachycardia, family history of premature sudden death, unexplained syncope, LV thickness greater than or equal to 30 mm, abnormal exercise blood pressure and nonsustained ventricular tachycardia.

Genetics

Gene	Locus	Type
MYH7	14q12	CMH1 (192600)
TNNT2	1q32	CMH2 (115195)
TPM1	15q22.1	CMH3 (115196)
MYBPC3	11p11.2	CMH4 (115197)
?	?	CMH5
PRKAG2	7q36	CMH6 (600858)
TNNI3	19q13.4	CMH7
MYL3	3p	CMH8 (608751)
TTN	2q24.3	CMH9
MYL2	12q23-q24	CMH10
ACTC1	15q14	CMH11 (612098)
CSRP3	11p15.1	CMH12 (612124)

Familial hypertrophic cardiomyopathy is inherited as an autosomal dominant trait and is attributed to mutations in one of a number of genes that encode for one of the sarcomere proteins.

About 50-60% of patients with a high index of clinical suspicion for HCM will have a mutation identified in at least 1 of 9 sarcomeric genes. Approximately 45% of these mutations occur in the β myosin heavy chain gene on chromosome 14 q11.2-3, while approximately 35% involve the cardiac myosin binding protein C gene. Since HCM is typically an autosomal dominant trait, children of a single HCM parent have 50% chance of inheriting the disease-causing mutation. Whenever a mutation is identified through genetic testing, family-specific genetic testing can be used to identify relatives at-risk for the disease.

In individuals without a family history of HCM, the most common cause of the disease is a de novo mutation of the gene that produces the β-myosin heavy chain.

An insertion/deletion polymorphism in the gene encoding for angiotensin converting enzyme (ACE) alters the clinical phenotype of the disease. The D/D (deletion/deletion) genotype of ACE is associated with more marked hypertrophy of the left ventricle and may be associated with higher risk of adverse outcomes.

Some mutations could have more malignant potential compared to others (β myosin heavy chain). For example, troponin T mutations were originally associated with a 50% mortality before the age of 40. However, a more recent and larger study found a similar risk to other sarcomeric protein mutations

Pathophysiology

Individuals with HCM have some degree of left ventricular hypertrophy. Usually this is an asymmetric hypertrophy, involving the inter-ventricular septum, and is known as asymmetric septal hypertrophy. This is in contrast to the concentric hypertrophy seen in aortic stenosis or hypertension. About two-thirds of individuals with HCM have asymmetric septal hypertrophy.

About 25% of individuals with HCM demonstrate an obstruction to the outflow of blood from the left ventricle during rest. In as much as 70% of patients however obstruction can be provoked under certain conditions. This is known as dynamic outflow obstruction, because the degree of obstruction is variable and is dependent on the loading conditions (ventricular filling and arterial blood pressure) and the contractility state of the left ventricle.

Myocardial hypertrophy and extracellular fibrosis predispose to increased left ventricular stiffness which in concert with compromised cellular energetics and abnormal calcium handling lead to diastolic dysfunction manifested as dyspnea and exercise intolerance.

The altered structure of the coronary vessels and increased diastolic pressure (reduced blood supply) together with the hypertrophy and the outflow tract obstruction (increased demand) cause myocardial ischemia that is manifested as angina and may be responsible for the triggering of ventricular arrhythmias.

In about 30% of patients there are abnormal vascular responses and inability to increase systolic blood pressure during exercise. This is attributed to exaggerated cardiac inhibitory reflexes initiated by increased myocardial wall stress and to elevated levels of vasodilating substances (natriuretic peptides).

Dynamic outflow obstruction

Dynamic outflow obstruction (when present in HCM) is usually due to systolic anterior motion of the anterior leaflet of the mitral valve. Systolic anterior motion of the mitral valve (SAM) was initially thought to be due to the septal subaortic bulge, narrowing the outflow tract, causing high velocity flow and a Venturi effect—a local underpressure in the outflow tract. Low pressure was thought to suck the mitral valve anteriorly into the septum. But SAM onset is observed to be a low velocity phenomenon: SAM begins at velocities no different from those measured in normal hearts. Hence, the magnitude and importance of Venturi forces in the outflow tract are much less than previously thought, and Venturi forces cannot be the main force that initiates SAM.

Recent echocardiographic evidence indicates that drag, the pushing force of flow is the dominant hydrodynamic force on the mitral leaflets. In obstructive HCM the mitral leaflets are often large and are anteriorly positioned in the LV cavity due to anteriorly positioned papillary muscles that at surgery are often "agglutinated" onto the LV anterior wall by abnormal attachments.

The mid-septal bulge aggravates the malposition of the valve and redirects outflow so that it comes from a lateral and posterior direction. The abnormally directed outflow may be visualized behind and lateral to the enlarged mitral valve, where it catches it, and pushes it into the septum There is a crucial overlap between the inflow and outflow portions of the left ventricle. As SAM progresses in early systole the angle between outflow and the protruding mitral leaflet increases. A greater surface area of the leaflets is now exposed to drag which amplifies the force on the leaflets – drag increases with increasing angle relative to flow. An analogy is an open door in a drafty corridor: the door starts by moving slowly and then accelerates as it presents a greater surface area to the wind and finally it slams shut. The necessary conditions that predispose to SAM are: anterior position of the mitral valve in the LV, altered LV geometry that allows flow to strike the mitral valve from behind, and chordal slack. SAM may be considered anteriorly directed mitral prolapse. In both conditions the mitral valve is enlarged and is displaced in systole by the pushing force of flow resulting in mitral regurgitation.

Because the mitral valve leaflet doesn't get pulled into the left ventricular outflow tract (LVOT) until after the aortic valve opens, the initial upstroke of the arterial pulse will be normal. When the mitral valve leaflet gets pushed into the LVOT, the arterial pulse will momentarily collapse and be followed by a second rise, as the left ventricular pressure overcomes the increased obstruction that SAM of the mitral valve causes. This can be seen on the physical examination as a double tap upon palpation of the apical impulse and as a double pulsation upon palpation of the carotid pulse, known as bifid pulse.

Screening

Main article: Hypertrophic cardiomyopathy screening

Although HCM may be asymptomatic, affected individuals may present with symptoms ranging from mild to critical heart failure and sudden cardiac death at any point from early childhood to seniority. HCM is the leading cause of sudden cardiac death in young athletes in the United States, and the most common genetic cardiovascular disorder. One study found that the incidence of sudden cardiac death in young competitive athletes declined in the Veneto region of Italy by 89% since introduction of routine Hypertrophic Cardiomyopathy Screening of athletes. As of 2010, however, studies have shown that the incidence of sudden cardiac death, among all HCM patients, has declined to one percent, or less. HCM can be detected with an echocardiogram with 80%+ accuracy, which can be preceded by screening with an electrocardiogram (ECG) to test for heart abnormalities. Cardiac magnetic resonance imaging (CMR), considered the gold standard for determining the physical properties of the left ventricular wall, can serve as an alternative screening tool when an echocardiogram provides inconclusive results. For example, the identification of segmental lateral ventricular hypertrophy cannot be accomplished with echocardiography alone. Also, left ventricular hypertrophy may be absent in children under thirteen years of age. This undermines the results of pre-adolescents’ echocardiograms. Researchers, however, have studied asymptomatic carriers of a HCM-causing mutation through the use of CMR and have been able to identify crypts in the interventricular septal tissue in these patients. It has been proposed that the formation of these crypts is an indication of myocyte disarray and altered vessel walls that may later result in the clinical expression of HCM. Lastly, giving warning of heart abnormalities in only 3% of patients before sudden cardiac death, the gathering of family history and physical examination alone are ineffective. A possible explanation for this is that the gathering of family history only focuses on whether sudden death occurred or not. It fails to acknowledge the age at which relatives suffered sudden cardiac death, as well as the frequency of the cardiac events. Furthermore, given the several factors necessary to be considered at risk for sudden cardiac death, and that no factor is more important than another, there exists ambiguity regarding when to implement special treatment.

United States

There are several potential challenges associated with routine screening for HCM in the United States. First, the U.S. athlete population of 15 million is almost twice as large as Italy's estimated athlete population. Second, these events are extremely rare in the U.S., with fewer than 100 deaths due to HCM in competitive athletes per year, or about 1 death per 220,000 athletes. Lastly, genetic testing would provide a definitive diagnosis; however, due to the numerous HCM-causing mutations, this method of screening is complex, and is not cost-effective. Therefore, genetic testing in the United States is limited to individuals which exhibit clear symptoms of HCM. This ensures that the test is not wasted on detecting other causes of ventricular hypertrophy (due to its low sensitivity), and that family members of the individual are educated on the potential risk of being carriers of the mutant gene(s).

In the United States such screening is not routine and the American Heart Association has "consistently opposed" routine screening.

Canada

Canadian genetic testing guidelines and recommendations for individuals diagnosed with HCM are as follows.

• The main purpose genetic testing is for screening family members.
  • According to the results, at-risk relatives may be encouraged to undergo or avoid extensive testing.

• Genetic testing is not meant for confirming a diagnosis.
  • If the diagnosed individual has no relatives that are at risk, then genetic testing is not required.

• Genetic testing is not intended for risk assessment or treatment decisions.
  • Evidence only supports clinical testing in predicting the progression and risk of developing complications of HCM.

For individuals suspected of having HCM

• Genetic testing is not recommended for determining other causes of left ventricular hypertrophy (such as athlete's heart, hypertension, and cardiac amyloidosis).
  • HCM may be differentiated from other hypertrophy-causing conditions using clinical history and clinical testing.

Diagnosis

A diagnosis of hypertrophic cardiomyopathy is based upon a number of features of the disease process. While there is use of echocardiography, cardiac catheterization, or cardiac MRI in the diagnosis of the disease, other important factors include ECG and genetic test (although not primarily used for diagnosis) findings and if there is any family history of HCM or unexplained sudden death in otherwise healthy individuals.

Obstructive and non-obstructive

Depending on whether the distortion of normal heart anatomy causes an obstruction of the outflow of blood from the left ventricle of the heart, HCM can be defined as obstructive or non-obstructive.

• The obstructive variant of HCM, hypertrophic obstructive cardiomyopathy (HOCM) has also historically been known as idiopathic hypertrophic subaortic stenosis (IHSS) and asymmetric septal hypertrophy (ASH).

• Another, non-obstructive variant of HCM is apical hypertrophic cardiomyopathy, also called Yamaguchi Syndrome or Yamaguchi Hypertrophy, first described in individuals of Japanese descent.

Physical examination

Differentiating hypertrophic cardiomyopathy and valvular aortic stenosis

	Aortic stenosis	Hypertrophic cardiomyopathy
Echocardiography
Aortic valve calcification	Common	No
Dilated ascending aorta	Common	Rare
Ventricular hypertrophy	Concentric LVH	Asymmetric, often involving the septum
Physical examination
Murmur of AI	Common	No
Pulse pressure after PVC	Increased	Decreased
Valsalva maneuver	Decreased intensity of murmur	Increased intensity of murmur
Carotid pulsation	Normal or tardus et parvus	Brisk, jerky, or bisferiens pulse (a collapse of the pulse followed by a secondary rise)

The physical findings of HCM are associated with the dynamic outflow obstruction that is often present with this disease.

Upon auscultation, the heart murmur will sound similar to the murmur of aortic stenosis. However, a murmur due to HCM will increase in intensity with any maneuver that decreases the volume of blood in the left ventricle (such as standing abruptly or the strain phase of a Valsalva maneuver). Administration of amyl nitrite will also accentuate the murmur by decreasing venous return to the heart. Classically, the murmur is also loudest at the left parasternal edge, 4th intercostal space, rather than in the aortic area.

If dynamic outflow obstruction exists, physical examination findings that can be elicited include the pulsus bisferiens and the double apical impulse with each ventricular contraction. These findings, when present, can help differentiate HCM from aortic stenosis. In addition, if the individual has premature ventricular contractions (PVCs), the change in the carotid pulse intensity in the beat after the PVC can help differentiate HCM from aortic stenosis. In individuals with HCM, the pulse pressure will decrease in the beat after the PVC, while in aortic stenosis, the pulse pressure will increase. However, the murmur intensity increases with both aortic stenosis and HCM post-PVC.

Cardiac catheterization

Pressure tracings demonstrating the Brockenbrough–Braunwald–Morrow sign
AO = Descending aorta; LV = Left ventricle; ECG = Electrocardiogram.

After the third QRS complex, the ventricle has more time to fill. Since there is more time to fill, the left ventricle will have more volume at the end of diastole (increased preload). Due to the Frank–Starling law of the heart, the contraction of the left ventricle (and pressure generated by the left ventricle) will be greater on the subsequent beat (beat #4 in this picture). Because of the dynamic nature of the outflow obstruction in HCM, the obstruction increases more than the left ventricular pressure increase. This causes a fall in the aortic pressure as the left ventricular pressure rises (seen as the yellow shaded area in the picture).

Upon cardiac catheterization, catheters can be placed in the left ventricle and the ascending aorta, to measure the pressure difference between these structures. In normal individuals, during ventricular systole, the pressure in the ascending aorta and the left ventricle will equalize, and the aortic valve is open. In individuals with aortic stenosis or with HCM with an outflow tract gradient, there will be a pressure gradient (difference) between the left ventricle and the aorta, with the left ventricular pressure higher than the aortic pressure. This gradient represents the degree of obstruction that has to be overcome in order to eject blood from the left ventricle.

The Brockenbrough–Braunwald–Morrow sign is observed in individuals with HCM with outflow tract gradient. This sign can be used to differentiate HCM from aortic stenosis. In individuals with aortic stenosis, after a premature ventricular contraction (PVC), the following ventricular contraction will be more forceful, and the pressure generated in the left ventricle will be higher. Because of the fixed obstruction that the stenotic aortic valve represents, the post-PVC ascending aortic pressure will increase as well. In individuals with HCM, however, the degree of obstruction will increase more than the force of contraction will increase in the post-PVC beat. The result of this is that the left ventricular pressure increases and the ascending aortic pressure decreases, with an increase in the LVOT gradient.

While the Brockenbrough–Braunwald–Morrow sign is most dramatically demonstrated using simultaneous intra-cardiac and intra-aortic catheters, it can be seen on routine physical examination as a decrease in the pulse pressure in the post-PVC beat in individuals with HCM.

Treatment

Asymptomatic patients

A significant number of patients with hypertrophic cardiomyopathy do not have any symptoms and will have normal life expectancies, though they should be counseled to avoid particularly strenuous activities or competitive athletics. These patients should also be screened for risk factors for sudden cardiac death. In patients with resting or inducible outflow obstructions, situations that will cause dehydration or vasodilation (such as the use of vasodilatory or diuretic blood pressure medications) should be avoided. Septal reductions therapy is not recommended in asymptomatic patients.

Medications

The primary goal of medications is to relieve symptoms such as chest pain, shortness of breath, and palpitations. Beta blockers are considered first-line agents, as they can slow down the heart rate. For patients who cannot tolerate beta blockers or do not have good control of symptoms with beta blockers, nondihydropiridine calcium channel blockers such as verapamil can be used. These medications also decrease the heart rate, though their use in patients with severe outflow obstruction, elevated pulmonary artery wedge pressure and low blood pressures should be done with caution. Dihydropyridine calcium channel blockers should be avoided in patients with evidence of obstruction. For patients who continue to have symptoms despite the above treatments, disopyramide can be considered for further symptom relief. Diuretics can be considered for patients with evidence of fluid overload, though cautiously used in those with evidence of obstruction. Patients who continue to have symptoms despite drug therapy can consider more invasive therapies.

Surgical myectomy

Surgical septal myectomy is an open heart operation done to relieve symptoms in patients who remain severely symptomatic despite medical therapy. It has been performed successfully for more than 25 years. Surgical septal myectomy uniformly decreases left ventricular outflow tract obstruction and improves symptoms, and in experienced centers has a surgical mortality of less than 1%, as well as 85% success rate. It involves a median sternotomy (general anesthesia, opening the chest, and cardiopulmonary bypass) and removing a portion of the interventricular septum. Surgical myectomy resection focused just on the subaortic septum, to increase the size of the outflow tract to reduce Venturi forces may be inadequate to abolish systolic anterior motion (SAM) of the anterior leaflet of the mitral valve. With this limited sort of resection the residual mid-septal bulge still redirects flow posteriorly: SAM persists because flow still gets behind the mitral valve. It is only when the deeper portion of the septal bulge is resected that flow is redirected anteriorly away from the mitral valve, abolishing SAM. With this in mind, a modification of the Morrow myectomy termed extended myectomy, mobilization and partial excision of the papillary muscles has become the excision of choice. In selected patients with particularly large redundant mitral valves, anterior leaflet plication may be added to complete separation of the mitral valve and outflow. Complications of septal myectomy surgery include possible death, arrhythmias, infection,incessant bleeding, septal perforation/defect, stroke.

Alcohol septal ablation

Alcohol septal ablation, introduced by Ulrich Sigwart in 1994, is a percutaneous technique that involves injection of alcohol into one or more septal branches of the left anterior descending artery. This is a technique with results similar to the surgical septal myectomy procedure but is less invasive, since it does not involve general anaesthesia and opening of the chest wall and pericardium (which are done in a septal myomectomy). In a select population with symptoms secondary to a high outflow tract gradient, alcohol septal ablation can reduce the symptoms of HCM. In addition, older individuals and those with other medical problems, for whom surgical myectomy would pose increased procedural risk, would likely benefit from the lesser invasive septal ablation procedure.

When performed properly, an alcohol septal ablation induces a controlled heart attack, in which the portion of the interventricular septum that involves the left ventricular outflow tract is infarcted and will contract into a scar. Which patients are best served by surgical myectomy, alcohol septal ablation, or medical therapy is an important topic and one which is intensely debated in medical scientific circles.

Ventricular pacing

The use of a pacemaker has been advocated in a subset of individuals, in order to cause asynchronous contraction of the left ventricle. Since the pacemaker activates the interventricular septum before the left ventricular free wall, the gradient across the left ventricular outflow tract may decrease. This form of treatment has been shown to provide less relief of symptoms and less of a reduction in the left ventricular outflow tract gradient when compared to surgical myectomy. Technological advancements have also lead to the development of a dual-chamber pacemaker, which is only turned on when needed (in contrast to a regular pacemaker which provides a constant stimulus). Although the dual-chamber pacemaker has shown to decrease ventricular outflow tract obstruction, experimental trials have only found few individuals with improved symptoms. Unfortunately, researchers suspect that these reports of "improved" symptoms are due to a placebo effect.

• Procedure includes an incision on the anterolateral area below the clavicle. Two leads are then inserted; one into the right atria and the other into the right ventricular apex via the subclavian veins. Once in place, they are secured and attached to the generator which will remain inside the patient's fascia, anterior to the pectoral muscle. Complications of this procedure include infection, electrical lead and generator malfunction which will require replacement.

Cardiac transplantation

In cases that are refractory to all other forms of treatment, cardiac transplantation is one option. It is also the only treatment available for end-stage heart failure. However, transplantation must occur before the onset of symptoms such as pulmonary vessel hypertension, kidney malfunction, and thromboembolism in order for it to be successful. Studies have indicated a seven-year survival rate of 94% in patients after transplantation.

Society and culture

Notable cases

British comedy actor Leonard Rossiter died from hypertrophic cardiomyopathy in 1984 while waiting to go onstage at the Lyric Theatre, London.

After the death of Marc-Vivien Foé of Cameroon during a 2003 FIFA Confederations Cup match, his autopsy revealed hypertrophic cardiomyopathy. Miklós "Miki" Fehér, a Hungarian football player who died during a match on January 25, 2004, also suffered from HCM.

The autopsy of actor Corey Haim identified HCM as one of the contributing causes (along with pneumonia and coronary arteriosclerosis) for his death in 2010.

Internet personality Ben Breedlove of Austin, Texas died on December 25, 2011, from HCM at age 18.

English footballer Mitchell Cole died from HCM on December 1, 2012 after retiring earlier in the year due to the condition.

Other noted athletes believed or suspected to have died from HCM include NFL players Thomas Herrion, Mitch Frerotte, Gaines Adams, and Derrick Faison; NBA players Reggie Lewis, Jason Collier, and Kevin Duckworth; NHL player Sergei Zholtok; long distance runner Ryan Shay; Loyola Marymount basketball star Hank Gathers; Loyola Marymount soccer player David Kucera; Western Kentucky University basketball player Danny Rumph; Kansas State football player Anthony Bates; LSU baseball player Wally Pontiff Jr.; Russian ice hockey star Alexei Cherepanov; and American strongman Jesse Marunde.

The Ontario Hockey League's Mickey Renaud Captain's Trophy honors former Windsor Spitfires captain Mickey Renaud, who died of HCM at age 19.

On December 10, 2008, NBA player Cuttino Mobley announced his retirement due to HCM.

The disease also ended the career of former Wake Forest star Robert O'Kelley, after a mandatory EKG in Brazil discovered his condition in 2006.

Current University of Denver assistant hockey coach David Carle was originally recruited to play for the team, but retired from playing after being diagnosed with HCM at the NHL draft combine. He was nonetheless drafted in the 7th round by the Tampa Bay Lightning.

Former Arsenal and Watford goalkeeper Manuel Almunia announced his retirement on August 26, 2014 after being diagnosed with HCM.

In children

Hypertrophic cardiomyopathy (HCM) is one of the most uncommon cardiac malformations encountered in pediatric cardiology. This attributed largely to the phenotypes is usually absent, incomplete, or delayed into adulthood. Most of current information pertaining HCM arises from studies in adult populations, and the implication of these observations for pediatric population is often uncertain. Nonetheless, recent studies in pediatric cardiology have revealed that HCM accounts for 42% of childhood cardiomyopathies with an incidence report of 0.47/100,000 in children. Further, in asymptomatic cases, sudden death is considered one of the most feared complications associated with the disease in select pediatric population. Consequently, the recommended practice is to start screening children of affected individuals throughout childhood to detect cardiac abnormalities at an early stage in hope to prevent further complication of the disease.

Generally, the diagnosis of HCM in a pediatric population is made during assessment for murmur, congestive heart failure, physical exhaustion, and genetic testing of children of affected individuals. Specifically, echocardiogram (ECHO) has been used as a definitive noninvasive diagnostic tool in nearly all children. ECHO assesses cardiac ventricular size, wall thickness, systolic and diastolic function, and outflow obstruction. Thus, ECHO has been chosen as an ideal means to detect excessive wall thickening of cardiac muscle in HCM.

In HCM, treatment strategies aimed to reduce disease symptoms and lower the risk of sudden death. Due to the heterogeneity of the disease, treatment is usually modified according to individual patients needs. β-blockers improve left ventricular filling and relaxation and thereby improve symptoms. In some pediatric patients, β–blockers drugs (e.g. propranolol) were shown to effectively reduce the risk of sudden death. Further, calcium channel blockers (verapamil) and antiarrhythmic drugs maybe used as an adjunct therapy to β-blockers in symptomatic children. Nonetheless, further testing is needed to determine their definitive benefits.

Other animals

Echocardiography of Hypertrophic-obstructive cardiomyopathy (HOCM) in a cat.

Feline hypertrophic cardiomyopathy (HCM) is the most common heart disease in domestic cats; the disease process and genetics are believed to be similar to the disease in humans. In Maine Coon cats, HCM has been confirmed as an autosomal dominant inherited trait. Numerous cat breeds have HCM as a problem in the breed. The first genetic mutation (in cardiac myosin binding protein C) responsible for feline HCM was discovered in 2005 in Maine Coon cats. A test for this mutation (A31P) is available. About one third of Maine Coon cats tested for the mutation are either heterozygous or homozygous for the mutation, although many of the cats that are heterozygous have no overt evidence of the disease on an echocardiogram (low penetrance). Some Maine Coon cats with clinical evidence of hypertrophic cardiomyopathy test negative for this mutation, strongly suggesting that another cause exists in the breed. The cardiac myosin binding protein C mutation identified in Maine Coon cats has not been found in any other breed of cat with HCM but more recently another myosin binding protein C mutation has been identified in Ragdoll cats with HCM. As in humans, feline HCM is not present at birth but develops over time. It has been identified for the first time in cats as young as 6 months of age and at least as old as 7 years of age.

Clinically cats with hypertrophic cardiomyopathy commonly have systolic anterior motion of the mitral valve (see graphic). Cats with severe HCM often develop left heart failure (pulmonary edema; pleural effusion) because of severe diastolic dysfunction of the left ventricle. They may also develop a left atrial thrombus that embolizes, most commonly, to the terminal aorta creating acute pain and rear limb paralysis (see below). Sudden death can also occur but appears to be uncommon.

There is no cure for feline HCM. Many but not all cats have a heart murmur. Many cats that have a heart murmur do not have HCM. Frequently the first signs that a cat has HCM are tachypnea/dyspnea due to heart failure or acute pain and paralysis due to systemic thromboembolism. While medication is commonly given to cats with HCM that have no clinical signs, no medication has been shown to be helpful at this stage and it has been shown that an ACE inhibitor is not beneficial until heart failure is present (at which time a diuretic is most beneficial). Diltiazem generally produces no demonstrable benefit. Atenolol is commonly administered when severe systolic anterior motion of the mitral valve is present.

Feline arterial thromboembolism (FATE) is relatively common and devastating complication of feline HCM and other feline cardiomyopathies. The thrombus generally forms in the left atrium, most commonly the left auricle. Formation is thought to be primarily due to blood flow stasis. Classically the thromboembolus lodges at the iliac trifurcation of the aorta, occluding either one or both of the common iliac arteries. Clinically this presents as a cat with complete loss of function in one or both hind limbs. The hind limbs are cold and the cat is in considerable pain. Emboli may, rarely, lodge in other locations, most commonly the right front limb and the renal arteries.

Clopidogrel (Plavix) is used to try to prevent left atrial thrombus formation in cats with HCM and a large left atrium. The FATCAT study at Purdue University demonstrated that it is superior to aspirin for the prevention of a second thrombus from forming in cats that have already experienced a clot. Thrombolytic agents (e.g., tissue plasminogen activator) have been used with some success to break down an existing aortic thromboembolus, but their cost is high and outcome appears to be no better than giving a cat time (48–72 hours) to break down its own clot. Pain management is extremely important. The prognosis for cats with FATE is often poor as they are likely to have significant HCM already and a recurrent bout of FATE is likely. For this reason euthanasia is often a valid consideration.

In July 2013, Rigo, a 42-year-old Western lowland gorilla, resident in Melbourne Zoo and father of Mzuri, the first gorilla born by artificial insemination, died unexpectedly as a result of HCM. The condition is not uncommon in male gorillas over the age of 30, and in many cases there is no sign of the disease until the individual's sudden death.

See also

• Sudden death (athletes)

References

External links

• Hypertrophic cardiomyopathy at DMOZ
• GeneReviews/NIH/NCBI/UW entry on Familial Hypertrophic Cardiomyopathy Overview
• National Heart, Blood, and Lung Institute Cardiomyopathy Page
• Hypertrophic Cardiomyopathy Patient Learning Center

UpToDate Contents

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• 1. 特殊な問題の治療を含む肥大型心筋症のマネージメントの概要 overview of hypertrophic cardiomyopathy management including treatment of special problems
• 2. 肥大型心筋症の臨床症状、診断、および評価 clinical manifestations diagnosis and evaluation of hypertrophic cardiomyopathy
• 3. 肥大型心筋症における内科的治療 medical therapy in hypertrophic cardiomyopathy
• 4. 肥大型心筋症の自然経過 natural history of hypertrophic cardiomyopathy
• 5. 肥大型心筋症の遺伝学 genetics of hypertrophic cardiomyopathy

English Journal

• Cardiac and skeletal muscle expression of mutant β-myosin heavy chains, degree of functional impairment and phenotypic heterogeneity in hypertrophic cardiomyopathy.

• Di Domenico M, Casadonte R, Ricci P, Santini M, Frati G, Rizzo A, Carratelli CR, Lamberti M, Parrotta E, Quaresima B, Faniello CM, Costanzo F, Cuda G.SourceDepartment of General Pathology, II University, Napoli, Italy.
• Journal of cellular physiology.J Cell Physiol.2012 Oct;227(10):3471-6. doi: 10.1002/jcp.24047.
• Several mutations in distinct genes, all coding for sarcomeric proteins, have been reported in unrelated kindreds with familial hypertrophic cardiomyopathy (FHC). We have identified nine individuals from three families harboring two distinct mutations in one copy of the β-myosin heavy chain (β-MHC
• PMID 22213221

• Functional consequences of abnormal Cx43 expression in the heart.

• Fontes MS, van Veen TA, de Bakker JM, van Rijen HV.SourceDepartment of Medical Physiology, University Medical Center, Utrecht, The Netherlands.
• Biochimica et biophysica acta.Biochim Biophys Acta.2012 Aug;1818(8):2020-9. Epub 2011 Aug 3.
• The major gap junction protein expressed in the heart, connexin43 (Cx43), is highly remodeled in the diseased heart. Usually, Cx43 is down-regulated and heterogeneously redistributed to the lateral sides of cardiomyocytes. Reverse remodeling of the impaired Cx43 expression could restore normal cardi
• PMID 21839722

Japanese Journal

• Cardioscopic Detection of Left Ventricular Thrombi : With Special Reference to a Comparison With Left Ventriculography and Echocardiography

• UCHIDA Yasuto,UCHIDA Yasumi,SAKURAI Takeshi,KANAI Masahito,SHIRAI Seiichiro,NAKAGAWA Osamu
• Circulation journal : official journal of the Japanese Circulation Society 75(8), 1920-1926, 2011-07-25
• … 12.5% of 57 patients with stable angina, 0% of 9 with unstable angina, 45.2% of 42 with acute myocardial infarction, 23.2% of 43 with old myocardial infarction, 61.9% of 21 with idiopathic acute myocarditis, 44.3% of 68 with idiopathic chronic myocarditis, 33.3% of 6 with rheumatic valvular disease, 25.7% of 31 with idiopathic dilated cardiomyopathy and in 8.0% of 12 with idiopathic hypertrophic cardiomyopathy. …
• NAID 10029127978

• Endocardial and Epicardial Deformations in Cardiac Amyloidosis and Hypertrophic Cardiomyopathy : 2-D Feature Strain Echocardiography

• DI BELLA Gianluca,MINUTOLI Fabio,PINGITORE Alessandro,ZITO Concetta,MAZZEO Anna,AQUARO Giovanni D.,DI LEO Rita,RECUPERO Antonino,STANCANELLI Claudia,BALDARI Sergio,VITA Giuseppe,CARERJ Scipione
• Circulation journal : official journal of the Japanese Circulation Society 75(5), 1200-1208, 2011-04-25
• … Background: The aim of the present study was to analyze epicardial (EPI) and endocardial (ENDO) strain (S) in patients with transthyretin-related cardiac amyloidosis (TTR-CA) and hypertrophic cardiomyopathy (HCM) using echocardiography (TTE) with 2-dimensional feature tracking imaging (FTI). …
• NAID 10028147758

• Combined Measurements of Cardiac Troponin I and Brain Natriuretic Peptide Are Useful for Predicting Adverse Outcomes in Hypertrophic Cardiomyopathy

• KUBO Toru,KITAOKA Hiroaki,OKAWA Makoto,YAMANAKA Shigeo,HIROTA Takayoshi,BABA Yuichi,HAYATO Kayo,YAMASAKI Naohito,MATSUMURA Yoshihisa,YASUDA Nobufumi,SUGIURA Tetsuro,DOI Yoshinori L.
• Circulation journal : official journal of the Japanese Circulation Society 75(4), 919-926, 2011-03-25
• … Background: Although serum cardiac troponin I (cTnI) and plasma brain natriuretic peptide (BNP) have become clinically important tools as diagnostic and prognostic markers for ischemic heart disease and heart failure, the usefulness of these biomarkers for risk stratification of hypertrophic cardiomyopathy (HCM) is not clear. …
• NAID 10028103447

• 肥大型心筋症の早期心筋障害に対するBMIPP心筋シンチと造影MRIの比較研究

• 川出 昌史,寺岡 邦彦,平野 雅春,五十嵐 祐子,山田 昌央,近森 大志郎,高沢 謙二,山科 章
• 東京醫科大學雜誌 69(1), 55-63, 2011-01-30
• NAID 10027806340

Related Links

• Hypertrophic cardiomyopathyとは - goo Wikipedia (ウィキペディア)

Hypertrophic cardiomyopathy (HCM) is a primary disease of the myocardium (the muscle of the heart) in which a portion of the myocardium is hypertrophied (thickened) without any obvious cause. [1] [2] [3] [4] [5] [6] It is perhaps best ...

• Hypertrophic cardiomyopathy: MedlinePlus Medical Encyclopedia

Hypertrophic cardiomyopathy (HCM) is a condition in which the heart muscle becomes thick. Often, only one part of the heart is thicker than the other parts. The thickening can make it harder for blood to leave the heart ...

Related Pictures

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★リンクテーブル★

リンク元	「肥大型心筋症」「HCM」
拡張検索	「apical hypertrophic cardiomyopathy」「non-obstructive hypertrophic cardiomyopathy」「dilated phase of hypertrophic cardiomyopathy」
関連記事	「hypertrophic」

「肥大型心筋症」

　　[★]

英

hypertrophic cardiomyopathy HCM, HCMJ

関

心筋症

定義

• 肥大型心筋症とは以下2つを特徴とする疾患群である(2005年の特発性心筋症調査研究班の手引き)。

• 1. 左室ないしは右室心筋の肥大
• 2. 心肥大に基づく左室拡張能低下

• ただし、基礎疾患ないし全身性の異常に続発し類似した病態を示す二次性心筋症(特定心筋症)は除外すること。

臨床検査による定義

• 心エコー検査もしくは心臓MRIで、15mm以上の最大左室壁厚(肥大型心筋症の家族歴がある場合は13mm以上)があること。

ESCのガイドライン 2014年による診断基準

• 1. 1つ以上のsegmentにおいて、15mm以上の左室壁肥厚が認められる。これは心エコー検査、CMRなどの画像診断を用い、安静時での評価による。
• 2. 13～14mmの壁肥厚の場合、肥大型心筋症の診断は家族歴、心臓以外の症状や兆候、心電図所見、遺伝子検査、各種画像検査での評価を含めた総合的な判断となる。
• 3. 左室壁肥厚が15mm以上の肥大型心筋症患者の第1度近親者以内の親族については、心エコー検査、CMR、心臓 CTなどの画像診断で 1 つ以上の segmentにおいて13mm以上の左室壁肥厚を認めた場合、肥大型心筋症の可能性を考慮する。

病因

• 半数が常染色体優性遺伝による。sarcomere complexを構成する蛋白をコードする遺伝子の異常による。この遺伝子にはβミオシン重鎖、トロポニンT、ミオシン結合蛋白Cをコードするものがある。(PHD.259)　→　蛋白の構造異常によるからAD

病型

心筋症診療ガイドライン（2018年改訂版） - 日本循環器学会

• 閉塞性肥大型心筋症 HOCM
• HNCM

• 1. 閉塞性肥大型心筋症 HOCM

• HOCM(basal obstruction)：安静時に30mmHg以上の左室流出路圧較差を認める
• HOCM(labile/provocable obstruction)：安静時に圧較差は30mmHg未満であるが、運動などの生理的な誘発で30mmHg以上の圧較差を認める

• 2. 非閉塞性肥大型心筋症 non-obstructive HCM,NHCM：安静時および誘発時に30mmHg以上の圧較差を認めない
• 3. 心室中部閉塞性心筋症 MVO 肥大に伴う心室中部での30mmHg以上の圧較差を認める
• 4. 心尖部肥大型心筋症 apical HCM：心尖部に限局して肥大を認める
• 5. 拡張相肥大型心筋症 dilated phase of HCM,D-HCM：肥大型心筋症の経過中に、肥大した心室壁厚が減少・菲薄化し、心室内腔の拡大を伴う左室収縮力低下(左室駆出率50％未満)をきたし、拡張型心筋症様病態を呈する

病理

• pattern of extensive disarray. Short, wide, hypertrophied fibers are oriented in chaotic directions and surrounded by numerous cardiac fibroblasts and extracellular matrix.(PHD.259)　→　これが拡張障害や不整脈の原因となる

症状

胸部症状

左室拡張障害に伴う左室拡張末期圧の上昇による肺毛細管圧の上昇、また左室内腔の狭小化による低心拍出量などが関連

• 労作時息切れ
• 呼吸困難

相対的心筋虚血が原因となりうる

• 胸痛
• 胸部絞扼感

• 動悸(不整脈(PAC,VPC,af)、頻脈、収縮力の増大に伴う過収縮)

脳症状

不整脈(心室頻拍、心室細動)ないし流出路狭窄による動作時・起立時の血圧低下が原因となる。血管拡張薬などの禁忌薬の使用時、起立動作時、飲酒時などに好発する。

• 立ちくらみ
• 眼前暗黒感
• 失神

症候

• dyspnea, palpirations, bifid apical impulse, coarse systolic murmur at the left sternal border, and ventricular hypertrophy with asymmertric septal thickening on echo cardiogram.(Q book p.304)

• bifid apical impulse: the forceful atrial contraction may also result in a palpable presystolic impulse over the cardiac apex (=double apical impulse)
• coarse systolic murmur: LA contraction into the stiffened LV

身体所見

PHD.262

心音

• S4：肥大した左心室壁に対して左心房が無理に血液を送り込むため
• double apical impulse：心尖部で触れる。左心房の懸命な収縮＋左心室の収縮
• (左室流出路が狭窄している場合)systolic murmur at the left lower sternal border　→　AS like でダイアモンド型の駆出期雑音を生じる
• (左室流出路が狭窄している場合)holosystolic blowing murmur at apex by MR　→　僧帽弁前尖を左室流出路に引き寄せるからMRが生じる。汎収縮期雑音を生じる。(also see PHD.44)
• 各種手技による雑音の変化。ASと反対の挙動を示す

• 静脈還流量減少によりmurmurが増強

• Valsalva maneuver
• standing

• 静脈還流量増加によりmurmurが減弱

• elevating one's leg
• increasing sympathetic tone
• squatting　→　HOCMにおいて、姿勢性めまいは一般的。The LV thus decreases in size and outflow tract obstruction intensifies.(PHD.262)

検査

頚動脈圧

• 二峰性頚動脈波

• 左室流出路が狭窄している場合は、頚動脈圧波の収縮期早期における急峻な立ち上がりと急激な低下がみられる(PHD.262)。HOCMでは収縮中期に駆出される血液量が低下し収縮期の脈波が二つの峰を形成する(参考2)。

その他、二峰性の頚動脈が認められる病態：大動脈閉鎖不全症、閉塞性肥大型心筋症、開存の大きい動脈管開存症、Valsalva洞破裂

心エコー

Mモードで観察

• 左心室壁の肥厚
• 非対称性中隔肥大(ASH)
• 僧帽弁前尖の収縮期前方運動(SAM)：循環血液量の減少と左室の過収縮による(YN.C-135)
• 大動脈弁の収縮中期半閉鎖：HOCMでは収縮中期に駆出される血液量低下のために大動脈弁が閉鎖しそうになる(参考2)
• 僧帽弁後退速度 DDRの低下：左心室のコンプライアンスが低下することにより、左室への血液流入速度が低下するため(YN.C-135)

心電図

• ST下降、T波の陰転化、左室高電位、QRS時間の院長、Q波異常 (ECGP.118)
• V3-V5における巨大陰性T波　→　心尖部肥大型心筋症

[show details]

V3-V6のST低下と陰性T波

治療

PHD.264

• 生活療法：激しい運動や競争をするような運動は避ける　→　突然死のリスクが高まる。
• 薬物療法：

• βブロッカー：(1)心筋酸素需要減少→狭心痛・呼吸困難↓、(2)左室流出路の圧勾配減少←心収縮力の低下により左室流出路の狭窄が解除される、(3)心室充満量増加←HR低下による、(4)心室期外収縮抑制。ただし、βブロッカーは不整脈による死亡は抑制できないらしい。
• カルシウムチャネル拮抗薬：(1)心室のコンプライアンス上昇(reduce ventricular stiffness)、(2)βブロッカーが不応の患者での運動耐性を上げる。
• 抗不整脈薬：心室細動や心室性頻拍から死に至ることがあるため。
• 抗菌薬：閉塞性肥大型心筋症では感染性心内膜炎が起こりやすいため。

• 埋め込み型除細動器 ICD：高リスクの患者に適応
• カテーテルインターベンション：percutaneous septal albation
• 手術療法：myomectomy

注意

• 利尿薬

禁忌

• 硝酸薬 (禁忌と言い切って良いのか知らないが、お手軽教科書には大抵禁忌と書いてある)

参考

• 1. 分かりやすい

http://www.nurs.or.jp/~academy/igaku/s1/s14222.htm

• 2.

http://kokushinado.ame-zaiku.com/circu/4_hm.html

• 3. 肥大型心筋症の診療に関するガイドライン

2007年改訂版

http://www.j-circ.or.jp/guideline/pdf/JCS2007_doi_h.pdf

2012年改訂版

http://www.j-circ.or.jp/guideline/pdf/JCS2012_doi_h.pdf

国試

• 105B041

「HCM」

　　[★] 肥大型心筋症 hypertrophic cardiomyopathy

「apical hypertrophic cardiomyopathy」

　　[★]

同

心尖部肥大型心筋症, APH

同

心尖部肥大型心筋症, AHCM

「non-obstructive hypertrophic cardiomyopathy」

　　[★] 非閉塞性肥大型心筋症

「dilated phase of hypertrophic cardiomyopathy」

　　[★] 拡張相肥大型心筋症

「hypertrophic」

　　[★]

• adj.

• 肥大性の、肥大型の、肥厚性の、肥大症の

関

hyperplastic