Cardiovascular Disease
Appendix A: Heart Failure and Non-ischemic Cardiomyopathies
Appendix A
Heart Failure (HF)
HF is a complex clinical syndrome that results from any structural or functional impairment of ventricular filling or ejection of blood. The structural or functional impairments can result from disorders of the pericardium, myocardium, endocardium, heart valves, great vessels, or metabolic abnormalities. The disease can have a wide spectrum of left ventricle functional abnormalities ranging from normal left ventricle size and function – i.e., normal ejection fraction (EF) – to severe dilatation with markedly reduced EF.1 Any underlying structural heart disease should be assessed according to the appropriate section of this document.
The cardinal manifestations of HF are dyspnea, fatigue, and fluid retention all of which can limit exercise tolerance. Because some patients can present without signs or symptoms of volume overload, the term “heart failure” is preferred over “congestive heart failure.” HF is not synonymous with either cardiomyopathy or left ventricular dysfunction; these latter terms describe possible structural or functional reasons for the development of HF.1
HF is diagnosed by history and physical examination. While there is no single diagnostic test, ejection fraction (EF) is a useful diagnostic and prognostic tool. Two common classification systems group/stage HF patients based on severity and prognosis: The New York Heart Association (NYHA),3 and American College of Cardiology Foundation/American Heart Association (ACCF/AHA).4
NYHA Grouping 3
The NYHA grouping of HF patients is based on exercise capacity and symptoms (see Table 1). It is a subjective assessment by a clinician and can change over short periods of time, particularly with treatment. Although reproducibility and validity may be problematic, it is an independent predictor of mortality.1,14,15
ACCF/AHA Staging 4
ACCF/AHA stages HF patients into four groups (A-D) according to the development and progression of the disease (see Table 1). The ACCF/AHA stages are progressive; once a patient moves to a higher stage, regression to an earlier stage of HF is not observed.1 Progression in HF stages is associated with reduced 5-year survival and increased plasma natriuretic peptide (BNP) concentrations.16
Table 1. ACCF/AHA Stages of Heart Failure and the New York Heart Association Functional Classifications*
| ACCF/AHA Stages of HF | NYHA Functional Classification |
|
A) At high risk for HF but without structural heart disease or symptoms of HF |
I) No limitation of physical activity. Ordinary physical activity does not cause symptoms of HF. |
| B) Structural heart disease but without signs or symptoms of HF | I) No limitation of physical activity. Ordinary physical activity does not cause symptoms of HF. |
| C) Structural heart disease with prior or current symptoms of HF | I) No limitation of physical activity. Ordinary physical activity does not cause symptoms of HF. |
| II) Slight limitation of physical activity. Comfortable at rest, but ordinary physical activity results in symptoms of HF. | |
| III) Marked limitation of physical activity. Comfortable at rest, but less than ordinary activity causes symptoms of HF. | |
| IV) Unable to carry on any physical activity without symptoms of HF, or symptoms of HF at rest. | |
| D) Refractory HF requiring specialized interventions | IV) Unable to carry on any physical activity without symptoms of HF, or symptoms of HF at rest. |
*Adapted from Yancy, et al. 2013 1
Clinicians should routinely assess the HF patient’s potential for adverse outcome. Numerous methods objectively assess risk, including biomarker testing (e.g., BNP), and a variety of multivariable clinical risk scores. One well-validated risk score, the Seattle Heart Failure Model, is available in an interactive application that provides information about risk of mortality in ambulatory patients with HF.17
Hypertrophic Cardiomyopathy (HCM)
HCM is a relatively common genetic disorder with varying phenotypic expression.12 Mutations in more than a dozen genes encoding sarcomere-associated proteins cause HCM. MYH7 and MYBPC3, encoding β-myosin heavy chain and myosin-binding protein C, respectively, are the two most common genes involved, together accounting for about 50% of the HCM families. In about 40% of HCM patients, the causal genes remain to be identified. The histological features of HCM include myocyte hypertrophy and disarray, as well as interstitial fibrosis. The hypertrophy is also frequently associated with left ventricular diastolic dysfunction.
HCM is characterized by left ventricle that is hypertrophied, but not dilated, with preserved or increased ejection fraction.18 HCM is associated with exertional dyspnea, impaired exercise performance, pre-syncope, syncope, and sudden cardiac death. Most authoritative bodies restrict HCM patients working in safety sensitive positions due to the risk of sudden incapacitating cardiac events.19,20,21
Recent studies, however, suggest that HCM patients with normal left ventricular size are not at increased risk of incapacitating sudden cardiac events.12,22,23 Therefore, it is reasonable to return LEOs with HCM to work if both an echocardiogram and cardiac MRI reveal a normal left ventricular size. Echocardiography may miss left ventricular abnormalities in the anterolateral free wall and apex, therefore both echocardiograms and cardiac MRIs should be performed on an annual basis.12,23 An end-diastolic wall thickness of less than 15 mm is considered normal size for any portion of the left ventricle wall.19 LEOs who have undergone surgical correction for IHSS (e.g., Morrow procedure, etc.) would still need restrictions due to absence of studies demonstrating a long-term reduction in the risk of sudden incapacitating cardiac events.12
Dilated Cardiomyopathy (DCM)
DCM refers to a large group of heterogeneous myocardial disorders characterized by ventricular dilation and depressed myocardial contractility in the absence of hypertension, valvular, congenital, or ischemic heart disease.13 DCM can be subdivided by pathogenesis, such as secondary to a systemic disorder (e.g., Lupus), toxins (e.g., alcohol), infections (e.g., viral), inflammation, or an inherited disorder (typically autosomal dominant).5 In patients where no pathogenesis could be identified are termed “idiopathic” cardiomyopathy. There are some rare reversible causes of DCM, and if these are present, the LEO should be re-evaluated after the underlying condition has been treated.5
DCM is characterized by left or right ventricular enlargement with ventricular wall of approximately normal thickness and varying extent of fibrosis. Patients develop progressive heart failure (e.g., exertional dyspnea, impaired exercise performance), reduced ejection fraction, and increased risk of sudden death.5
Myocarditis
Myocarditis consists of three overlapping phases: 1) acute injury (often caused by a virus); 2) the host innate and acquired immunologic response; and 3) recovery or a transition to scar formation and DCM. The transition from acute myocarditis to chronic DCM probably occurs over months with substantial individual variation.24 Myocarditis is associated with sudden death, particularly in young athletes and those undergoing strenuous physical activity.12,25 Unlike heart failure, the risk of sudden death caused by myocarditis does not appear to correlate with the severity of the myocardial inflammation.12