Hypertrophic Cardiomyopathy

By admin Last updated Sep 23, 2023

Ovid: 5-Minute Sports Medicine Consult, The

Matthew P. Boyd

Anne M. Garrison

Vikram Narula

Basics

Description

Asymmetric nondilated left ventricular hypertrophy (LVH), with or without outflow obstruction
Mostly inherited autosomal-dominant disease, but many cases are sporadic.
Primary cause (35%) of sudden atraumatic death in athletes <35 yrs
Death results from ventricular tachycardia either due to or in the absence of LV outflow obstruction (some patients have arrhythmogenic foci).
Synonym(s): Idiopathic subaortic stenosis; Asymmetric septal hypertrophy

Epidemiology

Incidence of hypertrophic cardiomyopathy (HCM) is 0.2% or 1:500 in the general population.
Incidence of sudden cardiac death in athletes <35, mostly due to HCM, is 1:250,000.

Risk Factors

Family history of unexplained or early (<40 yrs) cardiac death
Age from 12–30 yrs old
Prior history of syncope
Abnormal BP response to exercise

Diagnosis

History

History is negative for most patients.
Direct and specific questions are important, and parents should be questioned as well.
Providers should also inquire about prescription medications and drugs of abuse.

Physical Exam

Most common initial presentation is syncope or sudden cardiac death (SCD) with exertion
Palpations
Exertional chest pain
Most patients with HCM have a completely normal physical examination.
Murmur:
- In rare cases where murmur is detected, it usually is midsystolic and heard at the mid left sternal border.
- Murmur is ominous if it increases with maneuvers to decrease LV end-diastolic (LVED) filling. These maneuvers cause dynamic obstruction in the LV outflow tract.
- Maneuvers include rising from squatting to standing, moving from supine to vertical position, and performing the Valsalva maneuver.
- Murmur decreases when LVED filling increases, while moving from standing to squatting (LV free wall moves away from the septum with increased filling).
- Benign murmurs usually become louder while squatting and decrease on rising.
- Such murmurs are common with improved fitness from training, as described with the AHS.
- Athletes with significant outflow obstruction eventually may have pansystolic blowing murmur of mitral regurgitation radiating to the axilla.
Any diastolic murmur indicates other cardiac pathology requiring workup.

Diagnostic Tests & Interpretation

Lab

Genetic family screening is available.
Clinicians may be increasingly faced with the dilemma of making recommendations regarding sports participation for subjects who have only preclinical evidence of HCM (genotype positive-phenotype negative).

Imaging

Electrocardiogram:
- LVH findings
- Increased voltage
- Repolarization abnormalities
- Prominent deep Q waves in left precordial leads
- Ischemic ST changes in 90% of cases

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Holter:
- Not commonly used for screening, but may reveal paroxysmal atrial fibrillation and ventricular tachycardia, which frequently are symptomatic.
Echocardiogram:
- Echocardiogram usually shows LV wall thickening measured on the free wall as >15 mm.
- The wall thickness is characteristically asymmetric, with the interventricular septum and anterolateral thicker than the posterior wall.
- Unlike patients with HCM, athletes with AHS (fit, young adults who also have murmurs) have right ventricular hypertrophy and increased LV volumes or total LV diameter. These findings represent physiologic adaptations to increased plasma volume.

Diagnostic Procedures/Surgery

Exercise stress testing is useful for evaluation of symptomatic patients, but its value in screening asymptomatic subjects is controversial.

Differential Diagnosis

Athletic heart syndrome (AHS)
Myocarditis/pericarditis
Coronary artery anomalies
Aortic stenosis
Prolonged QT syndrome
Marfan syndrome
Wolff-Parkinson-White syndrome
Arrhythmogenic right ventricular dysplasia
Exercise-induced asthma
Costochondritis
Gastroesophageal reflux

Ongoing Care

36th Bethesda Conference recommendations for activity for individuals with HCM:

Athletes with a probable or unequivocal clinical diagnosis of HCM should be excluded from most competitive sports, except possibly low-intensity sports. This recommendation includes athletes with and without symptoms or LV outflow obstruction.
Given that the risk of SCD may be reduced in older individuals (>40 yrs) with HCM, an alternative of individual judgment may be used in selected older athletes only when each of the following clinical features is absent:
- Ventricular tachycardia (sustained or nonsustained) on ambulatory electrocardiogram
- Family history of SCD due to HCM, particularly if <40 yrs old
- History of syncope or other clinically relevant episodes of impaired consciousness
- Severe hemodynamic abnormalities, including dynamic LV outflow tract gradient >50 mm Hg
- Exercise-induced hypotension
- Moderate-to-severe mitral regurgitation, enlarged left atrium (>50 mm), or paroxysmal atrial fibrillation
- Presence of abnormal myocardial perfusion
- These recommendations are not altered if medical or surgical treatment is undertaken in a given athlete.
Although the clinical significance and natural history of genotype positive-phenotype negative individuals remains unresolved, no compelling data are available at present with which to preclude these patients from competitive sports in the absence of cardiac symptoms or family history of sudden death.

Additional Reading

Beckerman J, Wang P, Hlatky M. Cardiovascular screening of athletes. Clin J Sport Med. 2004;14:127–133.

Maron BJ, Ackerman MJ, Nishimura RA, et al. Task Force 4: HCM and other cardiomyopathies, mitral valve prolapse, myocarditis, and Marfan syndrome. J Am Coll Cardiol. 2005;45:1340–1345.

Maron BJ, Doerer JJ, Haas TS, et al. Sudden deaths in young competitive athletes: analysis of 1866 deaths in the United States, 1980–2006. Circulation. 2009;119:1085–1092.

Rizvi AA, Thompson PD. Hypertrophic cardiomyopathy: who plays and who sits. Curr Sports Med Rep. 2002;1:93–99.

Rowland TW. Evaluating cardiac symptoms in the athlete: is it safe to play? Clin J Sport Med. 2005;15:417–420.

Codes

ICD9

425.1 Hypertrophic obstructive cardiomyopathy
425.4 Other primary cardiomyopathies

Clinical Pearls

Avoid physical activities that require exertion while awaiting diagnosis as this may exacerbate your potential condition.
HCM is a rare genetic disease that can cause abnormal beating of the heart, especially with exercise. It is difficult to control, and even those who are treated probably should avoid all strenuous exercise unless HCM is proven not to be the diagnosis.
There is a significant risk of death in people who have true HCM. Exercise increases this risk in some athletes. Certain exercises may be permitted after the true diagnosis and extent of the problem are clear.
Only very low-intensity exercises (Class IA sports) are considered possibly acceptable, including golf, billiards, bowling, cricket, curling, and riflery.