Primary heart failure

1. Description of the problem

Primary heart failure is best defined as a condition affecting heart muscle function not associated with other structural causes.

Cardiomyopathy is a general term referring to diseases of the myocardium. Clinically and pathologically cardiomyopathy can be divided into dilated, hypertrophic, and restrictive types. Myocarditis, an inflammatory process that affects the myocardium and pericardium is a precursor to and one of the causes of dilated cardiomyopathy.

Clinical features

For patients with dilated cardiomyopathy symptoms of heart failure include respiratory distress due to pulmonary edema; abdominal pain due to hepatic engorgement and failure to thrive due to chronic heart failure. Peripheral edema is not common in childhood. Occasionally arrhythmias or chest pain might be the presenting complaint, especially in a patient with myocarditis. Syncope or cardiac arrest is the more likely acute presentation of patients with hypertrophic cardiomyopathy.

Key management points

Primary management is to establish a diagnosis. A chest X-ray is usually the first test suggesting cardiovascular involvement and demonstrates cardiac enlargement and pulmonary edema in dilated cardiomyopathy. In patients with acute onset myocarditis dilation may not have occurred although pulmonary congestion may be present. This is also true of patients with restrictive disease although their presentation is seldom of acute cardiovascular collapse.

Children presenting with vague abdominal pain are often misdiagnosed at first with abdominal pathology or enteritis. A high index of suspicion resulting in a chest X-ray and echocardiogram will establish the diagnosis of a cardiac problem. Exclusion of secondary (structural) causes of heart failure then will establish the diagnosis as primary heart failure.

2. Emergency Management

Follow the ABCs of resuscitation:

The degree of intervention will be determined by the status and acuity of the patient.

A. Airway management. Intervention with supplemental oxygen or mechanical ventilation may be necessary.

B. Vascular access for monitoring, blood chemistries and gases and drug infusions. Minimally these patients need good peripheral IV access. Central venous and arterial access need to be considered.

C. Assess circulatory adequacy and need to pharmacologic support.

D. Drugs. See below.

E. ECMO. Consider some form of mechanical circulatory support in someone presenting with or heading towards circulatory collapse.

Management points not to be missed

During or after stabilization of the patient, the following should be considered to help establish the potential cause of the cardiomyopathy. If the child is to be placed on mechanical circulatory support, one should obtain most of the blood tests prior to administration of blood products.

Initial Studies:

Family and personal history

Chest X-ray

Echocardiogram (including relatives and tissue Doppler imaging)

Urine

Organic acids including 3-methylglutaconic acid

UA

Amino acids

Blood

BNP

Lactic acid

Pyruvate

SMA-7

Glucose

Ca2+

Mg2+

Selenium

CBC with diff

CPK (MM, MB, total)

Troponin T or I

Liver function studies

Carnitine

Acylcarnitine profile

Cholesterol

Thyroid function studies

Plasma for amino acids

ESR

Viral serologies including adenovirus

Cytogenetics

Skeletal muscle biopsy

Histology

EM

Mitochondrial respiratory chain analysis, acyl CoA DH analysis
Endomyocardial biopsy (with hemodynamic catheterization and angiographic evaluation of structural lesions)

Histology

EM

PCR for vital genome

Mitochondrial respiratory chain analysis

Blood for cell lines

Cardiac MRI for myocarditis

Genetics consultation to include comprehensive metabolic/enzymatic evaluation and genetic screening for genes known to be involved in hypertrophic cardiomyopathy.

Strong consideration of drawing all transplant labs particularly before administration of IVIG.

Drugs and dosages

Acute pharmacologic intervention might include the following:

Milrinone: 0.5-1.0 mcg/kg/min

Nesiritide 0.1 mcg/kg; 0.01-0.03 mcg/kg/min

Dopamine: (5-10 mcg/kg/min) for hypotension

Epinephrine (0.05-1.0 mcg/kg/min) for hypotension

Norepinephrine (0.05-0.1 mcg/kg/min)

Vasopressin: Not recommended by AHA due to insufficient data. However, if used; 0.4 units/kg following resuscitation then 0.002-0.005 units/kg/hr (max 0.01 unit/kg/hr).

Dobutamine (5-10 mcg/kg/min). Although this is often used with milrinone in the face of poor left ventricular function, we prefer not to use it if possible as it increases myocardial oxygen demand.

Diuretics for congestive symptoms

Furosemide (1-2 mgs/kg/dose q 6,8,12 or 24 hrs, or 0.3 mgs/kg/hr)

Antiarrhythmics: depending on the arrhythmia present

Cardioversion: 0.5-1.1 joule/kg (may increase to 2 joules/kg if no effect)

Adenosine: 0.1-0.4 mg/kg (max 6 mg) rapid IV push for supraventricular tachycardia

Lidocaine: 1mg/kg IV bolus (wide complex tachycardia only); 20mcg/kg/min infusion

Amiodarone 5 mg/kg over 20-60 min; 5-7 mcg/kg/min. May rebolus 1-2 times if no effect.

Intra Venous Immune Globulin (IVIG): 1-2 gm/kg

For Myocarditis:

As the cellular inflammation in myocarditis resembles that seen in cardiac transplant rejection, physicians have hypothesized that immunosuppression in myocarditis might be beneficial. Experimental results in murine myocarditis have been mixed.

Despite numerous case reports on the treatment of myocarditis with immunosuppression, including steroids, cyclosporine, azathioprine and OKT3, there is no longitudinal data to support this form of therapy. In a randomized adult trial using steroids with either cyclosporin or azathioprine in patients with biopsy-proven myocarditis, there was no benefit in the treated group.

However, based on a small study which did not reach clinical significance, many pediatric centers prescribe to the concept that intravenous immune globulin (IVIG) has a benefit and routinely use it (1-2 grams/kg over 12-24 hrs). If this is to be used and the child may require cardiac transplantation, all transplant labs should be drawn before the IVIG is given. For non-infectious myocarditis, specifically autoimmune disease, immunosuppression may be of benefit.

3. Diagnosis

The first diagnosis to be established is that the presenting symptoms are due to cardiac involvement. This is easy when the presenting symptom is a hemodynamically compromising arrhythmia but less obvious when the presentation is abdominal pain.

Cardiac causes can be suggested by a chest X-ray but confirmed with an echocardiogram. The echocardiogram will generally exclude structural heart defects but if not, following stabilization of the child, cardiac catheterization or other imaging modalities may be necessary.

A BNP level is a simple test almost universally available now and should be performed in anyone where heart failure is a consideration. An elevated level (>100) should lead to a formal cardiac evaluation.

The flow diagram above lists the tests to be performed to help establish a specific cause. History may lead one to the diagnosis of post partum cardiomyopathy, or xanthrocycline cardiotoxicity, for example, while a family history of muscular dystrophy will lead in another direction. The table in the next section lists the diagnostic algorithm of patients presenting with a dilated poorly functioning left ventricle, including secondary causes to be excluded.

The combination of a BNP, EKG, chest X ray and echocardiogram will establish the diagnosis of a cardiac cause for the presenting symptoms. An endomyocardial biopsy or cardiac MRI (cMRI) can be used to diagnose myocarditis. In patients with an acute onset of cardiovascular collapse, the probable diagnosis is myocarditis.

ECMO support may be required and if so, there is a fair chance of recovery unless the inciting organism is a parvo virus. Those patients often do not recover. Although cMRI is useful in diagnosing myo or myo-pericarditis in stable patients presenting with chest pain and EKG changes, it does not identify a specific organism or separate viral myocarditis from other inflammatory conditions (e.g. giant cell myocarditis, autoimmune causes, etc.).

Pathophysiology

Dilated cardiomyopathy is a disease process of many causes that affect heart muscle function eventually resulting in diminished cardiac output and symptoms of heart failure. Presentation may be acute or chronic.

When function gradually deteriorates over a long period of time, patients will eventually present with a severely diminished ejection fraction (<20%) and significant cardiac enlargement on chest X-ray, whereas rapid deterioration of cardiac function may lead to a more acute presentation with less severe cardiac dysfunction (ejection fraction >30%) and less or no cardiac enlargement on chest X-ray.

Patients adapt to slow progressive disease and often feel asymptomatic (although on careful history they are not), whereas abrupt changes in cardiac function produce acute symptoms.

Myocarditis is a pathologic process characterized by inflammation of the myocardium leading to cellular necrosis and myocardial dysfunction. Although often thought of as a viral or post-viral process, causes of myocarditis are numerous and include infectious (viral, bacterial, fungal, yeast, rickettsial, protozoal and parasites) as well as non-infectious (toxins, drugs, autoimmune diseases and Kawasaki’s disease etiologies).

Hypertrophic Cardiomyopathy (HCM) is a familial disorder of cardiac muscle that affects sarcomeric proteins resulting in myocyte and myofibrillar disorganization and fibrosis. HCM has an autosomal dominant pattern of inheritance although morphologic evidence of disease may be absent in 20% of carriers.

Mutations in any of ten genes that code for sarcomeric proteins may result in HCM, however some mutations are relatively benign whereas others are associated with early death. There is no direct association of hypertrophy with left ventricular outflow tract obstruction, but the isolated apical hypertrophy form of the disease seldom shows obstruction.

Only 25% of patients with HCM have left ventricular outflow tract obstruction. Young children may also demonstrate fixed right ventricular outflow tract obstruction. Hypertrophic phenotypes similar to but distinct from HCM are found in patients with Noonan’s Syndrome, mitochondrial myopathies and metabolic disorders (e.g. infant of diabetic mother, Pompe’s disease, etc.).

Restrictive cardiomyopathy is the least common of all forms of cardiomyopathy. Patients with restrictive cardiomyopathy have abnormal diastolic function as the noncompliant ventricular myocardium impedes ventricular filling. Systolic function is relatively unimpaired. Functionally, restrictive cardiomyopathy resembles constrictive pericarditis, which is also characterized by normal or near normal systolic function but abnormal diastolic function.

Although the etiology of restrictive disease is often idiopathic, known causes include endomyocardial fibrosis, infiltrative disorders (amyloidosis, hemochromatosis and sarcoidosis), carcinoid syndrome, systemic sclerosis and radiotherapy to the chest.

Differental Diagnosis of a Patient with a Dilated Poorly Functioning Left Ventricle Based on Age

1) Fetal:

1) AV malformation (vein of Galen)

2) Myocarditis

3) Severe outflow obstruction

4) Severe valve insufficiency

5) Tachyarrhythmias

6) Severe anemia (immune hydrops)

7) Bradyarrhythmias (congenital complete heart block)

2) Newborn to 1 Year Old:

1) Myocarditis

2) Endocardial Fibroelastosis:(EFE)

3) Barth syndrome

4) Carnitine deficiency

5) Selenium deficiency

6) Anomalous Left Coronary Artery from Pulmonary Artery (ALCA)

7) Kawasaki Disease (KD)

8) Critical Aortic Stenosis (AS)

9) Supraventricular Tachycardias (SVT)

10) Arterio-venous malformation (especially vein of Galen)

11) Calcium deficiency

12) Hypoglycemia

13) Left ventricular non-compaction

14) Mitochondrial cardiomyopathy

15) Nemaline myopathy

16) Minicore-multicore myopathy

17) Myotubular myopathy

3) 1 Year to 10 Years Old:

1) Familial Dilated Cardiomyopathy (FDCM)

2) Barth syndrome

3) Myocarditis

4) Arrhythmogenic right ventricular

5) Endocardial Fibroelastosis (EFE)

6) Carnitine deficiency

7) Selenium deficiency

8) Anomalous Left Coronary Artery from Pulmonary Artery (ALCA)

9) Kawasaki Disease (KD)

10) Supraventricular Tachycardias (SVT)

11) Toxic (Adriamycin)

12) b-ketothiolase deficiency

13) Ipecac toxicity

14) Systemic lupus erythematosus

15) Polyarteritis nodosa

16) Hemolytic-uremic syndrome

17) Mitochondrial cardiomyopathy

18) Nemaline myopathy

19) Minicore-multicore myopathy

20) Myotubular myopathy

4) > 10 Years of Age

1) Familial dilated cardiomyopathy

2) X-linked Dilated Cardiomyopathy (XLCM)

3) Myocarditis

4) Supraventricular Tachycardia (SVT)

5) Congenital Heart Disease (Ebstein’s, etc.) (CHD)

6) Post-operative congenital heart disease

7) Mitochondrial Cardiomyopathy (P/O CHD)

8) Chagas disease

9) Arrhythmogenic right ventricular dysplasia (ARVD)

10) Eosinophilic cardiomyopathy

11) Adriamycin toxicity

12) Pheochromocytoma

13) Duchenne Muscular Dystrophy/Becker Muscular Dystrophy (DMB/BMD)

14) Emery-Dreifuss Muscular Dystrophy (EDMD)

15) Hemochromatosis

16) Limb-girdle muscular dystrophy

17) Myotonic dystrophy

18) Peripartum cardiomyopathy

19) Alcoholic cardiomyopathy

Epidemiology

Dilated cardiomyopathy is the most common of the three cardiomyopathies with an incidence of 1-8 cases/100,000 and a prevalence of about 36 cases/100,000.

Hypertrophic cardiomyopathy has a prevalence of 2.5/100,000, however the diagnosis of HCM is often delayed until adulthood.

Restrictive cardiomyopathy is rare and importantly must be differentiated from restrictive pericarditis, which is treatable by pericardiectomy.

Myocarditis is a sporadic disease, once thought to be caused primarily by coxsackie B virus but adeno and parvo viruses have become common recently.

Special considerations for nursing and allied health professionals.

What's the evidence?

Pharmacologic Therapy:

Myocarditis:

Mason, J, O’Connell, J, Herskowitz, A, Rose, N, McManus, B. “A clinical trial of immunosuppressive therapy for myocarditis”. N Engl J Med. vol. 333. 1995. pp. 269-75.

Druker, NA, Colan, SD, Lewis, AB. “Gamma-globulin treatment of acute myocarditis in the pediatric population”. Circulation. vol. 5. 1994. pp. 65-9.

Noutsias, M, Pauschinger, M, Poller, WC. “Immunomodulatory treatment strategies in inflammatory cardiomyopathy: current status and future perspectives”. Expert Rev Cardiovasc Ther. vol. 2. 2004. pp. 37-51.

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