Clinical Practice Guideline

for

CARDIOMYOPATHY

Developed for the

Aerospace Medical Association

by their constituent organization

American Society of Aerospace Medicine Specialists

 

Overview: The term cardiomyopathy broadly encompasses any disease of the myocardium associated with cardiac dysfunction.  Primary cardiomyopathies encompass four disease entities in which the abnormality is intrinsic to the myocardium itself: idiopathic or dilated cardiomyopathy (DCM), hypertrophic cardiomyopathy (HCM), restrictive cardiomyopathy (RCM), and arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D).  Secondary cardiomyopathies refer to disease states in which the primary abnormality is extrinsic to the myocardium but results in cardiac dysfunction.  The most common secondary cardiomyopathies are ischemic cardiomyopathy (ICM) secondary to coronary artery disease, hypertensive cardiomyopathy (commonly isolated diastolic dysfunction), Chagas’ disease-related cardiomyopathy, and cardiomyopathy secondary to valvular heart disease.  Although different categorization schemes have been proposed, this functional approach to classification has proven to be the most clinically and aeromedically useful and will be used here.

 

DCM is typically characterized by left ventricular dilation, systolic dysfunction, and a general reduction in overall contractility.  The natural history of DCM is not well-established, although the 5-year mortality rate ranges from 20-50%.  Individual predictions of morbidity and mortality vary substantially, however disease severity correlates well with outcomes.  DCM is most common in middle-aged men, and has an overall incidence of 5-8/100,000/year.  Symptoms are generally progressive and include those of left-heart failure (fatigue, exercise intolerance, dyspnea, etc).  Associated right-heart failure and/or global chamber enlargement are late signs.  Although the final cause of death in individuals with DCM is typically systolic failure, arrhythmias, thromboembolic events, and sudden death may occur at any time.  Post-partum cardiomyopathy is a type of DCM.

 

Viral myocarditis is considered the likely etiology for many cases of idiopathic DCM.  There may thus be some confusion whether a case is more appropriately considered myocarditis or DCM.  Typically, myopericarditis will present acutely with chest discomfort, characteristic ECG changes, elevated cardiac enzymes and regional or diffuse left ventricular wall motion abnormality.  DCM with diffuse hypokinesis may be the end result of viral myocarditis, presenting either with symptoms of left ventricular dysfunction or diagnosed incidentally on echocardiography.

 

HCM is characterized by hypertrophy of the left ventricle, usually in an asymmetric fashion involving the base of the LV septum.  Multiple anatomic variations are known to occur, however, including concentric and apical-only patterns.  HCM is characterized by the development of scar tissue and disorganized myofibrils.  Thus, ventricular arrhythmias and sudden death are common.  While HCM is known to be an autosomal dominant heritable disorder, roughly half of all cases are spontaneous in nature.  Nevertheless, familial screening of identified probands is usually undertaken, particularly in the young.  The prevalence of HCM is broadly estimated at 20-200/100,000.  It is most commonly diagnosed in the 4th and 5th decades but has been identified in all age groups including stillborns.  Although a pressure gradient of the left ventricular outflow tract is a distinctive clinical feature, it is present in only about 25% of patients.  Symptoms, when present, commonly include dyspnea, angina, fatigue, presyncope, and syncope.  In younger populations, HCM is commonly confused with athlete’s heart; HCM will not regress with cessation of athletic activity, however.

 

Both DCM and HCM may be misdiagnosed locally, because of the unfamiliarity of some clinicians with cardiac variants seen in relatively young and athletic subjects such as many in the military aviator population.  Ejection fraction at rest may be low normal or mildly reduced (45-50%) in athletic individuals compared to clinical norms (50-70%), resulting in a misdiagnosis of mild DCM.  And left ventricular wall thickness may be upper normal to mildly increased (12-13 mm) compared to clinical norms (7-11 mm), resulting in a misdiagnosis of pathologic left ventricular hypertrophy or mild HCM.  Thus, cardiology review is necessary for all diagnosed cardiomyopathies, to confirm (or refute) the diagnosis, then advise regarding prognosis and waiver eligibility in accordance with approved policy. 

 

The hallmark of restrictive cardiomyopathy (RCM) is severely abnormal diastolic function.  The ventricular walls are excessively rigid and impede filling, resulting in pulmonary and systemic venous congestion.  RCM must be differentiated from constrictive pericarditis, which can be successfully surgically treated.  RCM can be a primary disorder or secondary to infiltrative or scarring processes that involve the myocardium such as amyloidosis, sarcoidosis, or scleroderma.  Other rare causes such as hypereosinophilic syndrome and endomyocardial fibrosis are usually seen only in certain geographic areas such as equatorial Africa and South America.  Common symptoms include exercise intolerance, dyspnea, fatigability, and weakness.  RCM is typically relentlessly progressive, poorly responsive to most therapies, and associated with a high mortality rate.

 

Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) has received heightened attention in recent years because of its association with ventricular tachycardia and sudden death, particularly in younger populations.  It is characterized by fibro-fatty replacement of the right ventricular myocardium.  This results in a predisposition towards potentially lethal ventricular arrhythmias, and the usual clinical presentation is sustained or non-sustained ventricular tachyarrhythmias and/or sudden cardiac death.

 

Finally, secondary cardiomyopathies such as ischemic cardiomyopathy, hypertensive cardiomyopathy, and valvular cardiomyopathy all have variable prognoses depending on the severity and treatment of the underlying disease.  If left untreated, all may progress to a terminal stage of irreversible myocardial dysfunction marked by systolic and/or diastolic failure, dilation, and an increased likelihood of associated arrhythmias, thromboembolic events, and sudden death.  The development of a secondary cardiomyopathy is considered an aeromedical endpoint for the above disorders, and is usually not compatible with a return to flight status recommendation.  Aeromedical disposition will be based on policies for the underlying disorder and the impact of the secondary cardiomyopathy on prognosis.

 

Aeromedical Concerns: There are two primary aeromedical concerns for individuals with cardiomyopathy.  The first is the risk of sudden incapacitation.  The risk of sudden death, arrhythmias, and/or thromboembolic events is generally correlated with the overall degree of cardiac dysfunction, although as noted above some types of cardiomyopathy (notably HCM and ARVC/D) are more likely to be associated with potentially suddenly incapacitating symptoms.  Secondly, even mild degrees of myocardial dysfunction may be incompatible with military aviation duties due to an associated reduction in exercise tolerance, the need for complex medical therapy, and the need for frequent access to specialized medical care.  Specifically, standard-of-care medical therapy for cardiomyopathy usually involves multiple hemodynamic, vasoactive, chronotropic, and diuretic medications which may alter physiologic responses to some aeromedical environments such that the aviator cannot perform his or her usual duties without an undue increase in risk to themselves, the crew, or the mission.  Device therapies for cardiomyopathies are not waiverable due in part to the unacceptably high complication rates associated with the devices themselves.

 

Medical Work-up: Essential to a good evaluation is a thorough history to include description of symptoms before and after the acute episode, all medications, and the current activity level.  Required tests include and ECG, chest X-ray and official reading of the test, official report of all performed echocardiograms, and reports of all associated tests such as treadmill, Holter monitor, cardiac catheterization, cardiac CT or MRI.  A detailed cardiology report is also mandatory.  If military, the results of the medical evaluation board will be required.

 

Aeromedical Disposition:

 

Air Force: Cardiomyopathy is disqualifying for all classes of flying in the Air Force.  Diagnoses of cardiomyopathies may be made following acute symptomatic episodes or in an asymptomatic subject receiving an echocardiogram for a variety of clinical and/or aeromedical indications.  Waiver submissions should be made only after resolution of any acute episode, stabilization of the medical regimen, and release of the individual back to full unrestricted activities by the treating cardiologist.  Most members diagnosed with any type of cardiomyopathy will also need to meet an MEB prior to waiver submission.  Waivers for members with all but the most mild degrees of cardiomyopathy will only be considered after the individual has been released to full unrestricted activity and found fit for continued military duty by an MEB.

 

Aeromedical Consultation Service (ACS) review is required for all locally diagnosed cardiomyopathies however, to confirm (or refute) the diagnosis and advise regarding prognosis and waiver eligibility.  Mild cases of DCM which resolve over time might be considered for waiver after ACS evaluation.  And some secondary cardiomyopathies may be waiver eligible, based on policies for the underlying disorder and the impact of the secondary cardiomyopathy on overall prognosis.  Typically, this will involve definitive therapy that results in an aeromedically acceptable result, including resolution of the cardiomyopathy.  Resolution of tachycardia-induced cardiomyopathy is one example.  Return of left ventricular and left atrial size and function to normal after successful surgical repair of severe mitral regurgitation is another.

 

Army: Cardiomyopathy is a disqualifying condition specified in AR 40-501 Standards of Medical Fitness and the aeromedical policy is articulated in a specific Aeromedical Policy Letter on the topic.  The aeromedical concerns of the Army are similar to those of the USAF.  Waiver may be considered in only the very mildest of cases with minimal hemodynamic and echocardiographic abnormalities and after the exclusion of underlying pathology.  Cardiomyopathy must have been felt due to a reversible cause, with complete resolution of cardiovascular findings, an ejection fraction >50%, and not requiring supportive medications.  True primary hypertrophic cardiomyopathy is generally not granted a waiver and; in fact, it is considered disqualifying for all military duties in the Army.  A unique entity to military personnel has been the identification of vaccine related myopericarditis, which has been seen to have a favorable prognosis even with initial identification of a dilated cardiomyopathy.  Waiver for this unique subclass of cardiomyopathy will be considered 6 months from time of acute of illness.

 

Navy: True primary hypertrophic cardiomyopathy (e.g., IHSS) is rare, and is not usually discovered until post-mortem.  This condition is disqualifying for general duty, and no waivers are recommended either for accession to general duty or special duty. Waiver will only be considered in the very mildest of cases with no hemodynamic and minimal echocardiographic abnormalities and after the exclusion of underlying pathology.  If the myopathy is secondary to other pathology, that condition is the basis of disqualification. If the hypertrophic changes are documented to have resolved after treatment, a waiver recommendation may be considered.  The majority of patients with idiopathic cardiomyopathy are disqualified from military flying. If a waiver is requested, refer to NOMI for evaluation.

 

Civilian: Cardiomyopathy, per se is not absolutely disqualifying.  It depends on several things.  Each case is reviewed on its own merits. Viral myocarditis that is on the mend has been granted issuance provided there is no heart failure, evidence of predisposition to arrhythmias, and proof that there is improvement. Cases of ischemic cardiomyopathy are also certificated providing there  is no congestive heart failure, sustained cardiac arrhythmias, ischemia on nuclear stress testing, and the ejection fraction is not less than 40%.  In cases of diagnosed hypertrophic cardiomyopathy airmen have only been certificated as limited second-class or third-class.  They cannot have a family history of sudden death, any ischemia or exercise-induced arrhythmias on nuclear stress testing, a Holter monitor that demonstrates arrhythmias especially VTACH, a left ventricular posterior wall greater than 45 mm, and a left atrium greater than 21 mm.  Private pilots have been granted certification with ischemic cardiomyopathy as long as they do not have arrhythmias that are exercise induced, and their ejection fraction is not less than 35%.  It is not unusual for these patients to have internal defibrillators implanted but the FAA does not permit these devices.

 

Waiver Experience:

 

Air Force: Review of AIMWTS showed 16 cases of cardiomyopathy; two FC I, six FC II, and nine FC III.  Eleven (69%) were disqualified due to cardiomyopathy; two FC I, four FC II, and five FC III.  The five granted waivers had cardiomyopathy that resolved (four DCM [peripartum, viral, idiopathic] and one cardiomyopathy associated with atrial fibrillation).

 

Army: The Aeromedical Epidemiological Data Repository (AEDR) catalogs all Army flight physicals since 1960.  There have been approximately 160,000 individual aircrew entered in this database.  During this period of time, there have been 30 cases of cardiomyopathy discovered.  Of those 6 were retained.

 

Navy: Not available at this time.

 

Civilian: The FAA breaks down cardiomyopathies into three categories for its pathology coding: Restrictive cardiomyopathy which has 69 first-, 50 second- and 170 third-class airmen currently issued. Ischemic or congestive cardiomyopathy has 15 first-, 21 second- and 113 third-class currently issued airmen. What used to be known as idiopathic hypertrophic subaortic stenosis and is now called hypertrophic cardiomyopathy has 19 first-, 20 second-, and 75 third-class airmen currently issued.

 

ICD 9 Codes for cardiomyopathy

425.4

Other primary cardiomyopathies (hypertrophic, restrictive, idiopathic, familial, not otherwise specified, congestive, constrictive, obstructive, non-obstructive)

425.9

Secondary cardiomyopathy, unspecified

086.0

Chagas’ disease with heart involvement

 

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References:

 

Cooper LT.  Definition and classification of the cardiomyopathies.  UpToDate.  Online version 15.3, December 22, 2006.

 

Kruyer WB. Cardiology.  In: Rayman RB, ed.  Clinical Aviation Medicine, 4th ed.  New York: Graduate Medical Publishing, LLC, 2006; 153-154 and 234-243.

 

Kruyer WB, Gray GW, Leding CJ.  Clinical aerospace cardiovascular medicine.  In: DeHart RL, Davis JR eds.  Fundamentals of Aerospace Medicine, 3rd ed. Philadelphia: Lippincott Williams & Wilkins, 2002; 335-338, 348-49 and 352.

 

Jacobs AG, Bales AC, Lang RM.  Peripartum cardiomyopathy.  UpToDate.  Online version 15.3, April 27, 2007.

 

 

 

Prepared by Drs. Russ Strader, Bill Kruyer, and Karen Fox

Date: September 26, 2010