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The American College of Cardiology and the American Heart Association unveiled the first guidelines for the diagnosis and treatment of hypertrophic cardiomyopathy (HCM) -- guidelines that detail recommendations for genetic testing.

Genetic testing, according to the guidelines simultaneously published online by Circulation: Journal of the American Heart Association and the Journal of the American College of Cardiology, is recommended in patients with atypical presentation of HCM (class I, level of evidence B) and may be considered to identify first-degree family members at risk of the disease (class IIa, level B).

But genetic testing to assess the risk of sudden cardiac death in patients with HCM was considered less certain (class IIb, level B).

In addition, in those with pathogenic mutations but without the HCM phenotype, the guidelines recommend (class I, level B) serial ECG, transthoracic echocardiography (TTE), and clinical assessments at periodic intervals depending on age.

"HCM is widely misperceived as a fatal condition, but a diagnosis of HCM is not a diagnosis of sudden cardiac death," said lead author Bernard J. Gersh, MB, ChB, DPhil, from the Mayo Clinic in Rochester, Minn., in a statement. "We now have effective treatments to help most patients manage the condition, although it remains the most common cause of sudden death in the young and in competitive athletes."

The reason that cardiologists and surgeons felt the need for guidelines is because the frequency of HCM is higher than initially perceived, "and a realization that many aspects of clinical management, including the use of diagnostic modalities and genetic testing, lack consensus," Gersh and colleagues wrote.

They also noted that two different approaches to septal reduction therapy and the potential use of an implantable cardioverter defibrillator have "created considerable controversy."

The recommendations, they cautioned, apply to patients with established HCM and "to a variable extent to patients with a high index of suspicion of the disease."

HCM is a genetic disorder which changes the way the heart functions. It can cause sudden cardiac death and often does not have symptoms. Abnormal thickening of the heart can also obstruct blood flow, for which surgery is often needed.

The disease occurs in about one in 500 people and is the most common inherited heart disease. Yet, many cardiologists might see only one new case of HCM a year. The guidelines, therefore, are meant to consolidate the evidence and aid in diagnosing and treating the disease.

For example, in the initial evaluation of someone with HCM, the guidelines recommend a 12-lead ECG and 24-hour Holter monitoring to detect ventricular tachycardia and to identify those who might benefit from an implantable cardioverter defibrillator (class I, level B for all).

Regarding echocardiography, the guidelines recommend TTE be used in the initial evaluation of all patients suspected of the disease, and also for family members in some cases (class I, level B).

Periodic screening with TTE is recommended for children of patients, starting by age 12 or earlier and especially if they are engaging in competitive sports (class I, level C).

The guidelines noted that periodic echo exams of patients with HCM "can be useful" every one to two years (class IIa, level C) and exercise treadmill can be used to determine functional capacity (class IIa, level C).

MR imaging received class I recommendation when TTE is inconclusive (level B) and to glean additional information that might influence patient management (level B).

The authors suggested that CT imaging may be useful in some patients with chest pain to determine the presence or extent of coronary artery disease, as well as SPECT or PET imaging (class I and II, all level of evidence C).

Other recommendations include:

• Drug therapy with beta-blockers, verapamil, or disopyramide can control symptoms such as shortness of breath (class I, level B)
• Surgical septal myectomy received a class IIa, level B recommendation, as did catheter-based alcohol septal ablation if surgery is contraindicated
• However, if a surgical candidate prefers alcohol septal ablation, he or she may choose it over surgery (class IIb, level B)
• A pacemaker can be considered for patients who are not candidates for septal reduction therapy (class IIb, level B)

The writing committee included representatives from the American Association for Thoracic Surgery, American Society of Echocardiography, American Society of Nuclear Cardiology, Heart Failure Society of America, Heart Rhythm Society, Society for Cardiovascular Angiography and Interventions, and the Society of Thoracic Surgeons.

The authors noted "the lack of high levels of evidence regarding HCM provided by clinical trials" but acknowledged that "a guideline document based on expert consensus that outlines the most important diagnostic and management strategies would be helpful."

From the American Heart Association:

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