May rapidly develop heart failure, arrhythmias, or may cause sudden death
There may be a murmur due to cardiac dilatation causing mitral regurgitation
May heal completely, or may progress to dilated cardiomyopathy years later
Grossly, hearts with active myocarditis are described as soft and flabby. The myocardium may be mottled and the heart may be dilated. Microscopically, viral myocarditis is characterized by a (nonspecific) lymphocytic infiltrate with myocyte necrosis.
Chagas disease – the protozoan bug is Trypanosoma cruzi
Important in South America – 80% with heart involvement – may be lethal or may go into chronic phase
Transmitted by insects such as reduvid bug
Microscopically see parasites within myocytes and mixed inflammation
T. Cruzi may also cause destruction of the myenteric plexus of the esophagus, duodenum, colon and ureter with subsequent dilatation of these viscera (megacolon).
Giant Cell Myocarditis
Has a rapid onset with a poor prognosis
Microscopically see myocardial necrosis with lymphocytes, plasma cells, eosinophils and giant cells
Has some overlap with sarcoidosis, but sarcoidosis has a more insidious onset
Some patients may recover completely or with some myocardial fibrosis
A variant is arrhythmogenic right ventricular dysplasia (cardiomyopathy) – a heritable defect that causes heart failure and may cause sudden death in young persons (see Robbins text)
Dilated CM is also known as congestive cardiomyopathy. Dilated CM may cause death either by heart failure or arrhythmia.
Causes of Dilated CM
Burned out myocarditis
EtOH or other toxicity
Peripartum CM occurs late in pregnancy or several weeks to months postpartum – poorly understood – possibly related to circulating anti-angiogenic factors
Genetic – 30% to 50% of cases, variable inheritance, mostly autosomal dominant, & variable defects - one is abnormal cytoskeletal protein like Duchenne & Becker muscular dystrophy
Mostly the cause is unknown
The progression from viral myocarditis to dilated cardiomyopathy has been demonstrated by serial myocardial biopsies. However, in most cases of DCM, the heart shows little or no residual inflammation.
Toxic causes of DCM are hard to prove – no good way to tell apart from other DCM.
The etiology of peripartum CM may be multifactorial, including factors such as hypertension, volume overload, poor nutrition, possible metabolic abnormalities or autoimmune phenomena; recent evidence suggests that it may be related to circulating anti-angiogenic factors (see Robbins text).
Morphology of Dilated CM
Rounded, dilated heart, 2 –3x expected weight
LV wall may be thinner due to dilatation
May see endocardial fibrosis, may see mural thrombus in chambers
Coronary arteries OK
Valves OK, but possible regurg of AV valves due to annulus dilatation
Histology not too exciting – myocyte hypertrophy, some interstitial fibrosis, rarely some residual myocarditis
Has many names:
Idiopathic hypertrophic subaortic stenosis
Hypertrophic obstructive cardiomyopathy
Asymmetric septal hypertrophy
Features a heart that is normal in shape, but with marked wall thickening due to hypertrophy (esp LV) often with asymmetric thickening of the septum and narrowing of the LV cavity
The heart is hypercontractile without LV cavity dilatation
The problem is diastolic filling and LVOT obstruction
Has a better prognosis than DCM, but may cause angina, CHF, A-fib, mural thrombus, infective endocarditis of MV
Can affect children or adults
HCM is one of the most common causes of sudden death in young athletes
The septum may bulge into the left ventricular outflow tract. This acts in concert with the adjacent anterior leaflet of the mitral valve to produce left ventricular outflow tract obstruction. A harsh systolic ejection murmur may be present.
Late cardiac dilatation in the course of HCM may actually relieve the LVOT obstruction.
To diagnose HCM, it is necessary to rule out other causes of myocardial hypertrophy such as hypertension and aortic stenosis.
Sudden death may be due to blockage of the left ventricular outflow by the anterior leaflet of the mitral valve. The leaflet may be sucked into the LVOT by “venturi” action of the blood flowing through the narrowed passage.
HCM can be managed medically better than DCM.
Causes of Hypertrophic CM
Has a genetic basis in all cases. Most are familial and typically autosomal dominant with variable expression; the rest are sporadic
Often genetic errors are in coding for contractile proteins; >100 mutations known
Newer evidence suggests that HCM may arise from a defect in energy transfer from mitochondria to sarcomeres
Investigation of family members of patients with HCM is indicated.
Morphology of Hypertrophic CM
Thickened LV wall at the expense of the cavity, often with asymmetric septal thickening and bulge of septum into LVOT
Heart may be normal in shape (may look normal on a routine chest X-ray), but 2-3x expected weight
Anterior leaflet of MV is thickened, and there may be a “friction lesion” on the LVOT
Histology shows myocyte hypertrophy, some interstitial fibrosis, and sometimes myofiber disarray, especially in septum
Myofibrillar disarray within cardiac myocytes in HCM can be seen with electron microscopy.
This is a disorder of ventricular compliance – The heart is normal in shape but stiff
Constrictive pericarditis is clinically similar – heart is mechanically prevented from contracting well
Causes of Restrictive CM
Things that infiltrate and stiffen the myocardium:
Some storage diseases
Endomyocardial fibrosis (a tropical disease of unknown cause)
Things that thicken and stiffen the myocardium and endocardium:
Endocardial fibroelastosis (in children - occurs with some types of congenital heart disease and rarely occurs alone)
Loeffler endomyocarditis (assoc. with eosinophilia or eosinophilic leukemia)
Endomyocardial fibrosis (a tropical disease of unknown cause)
Idiopathic restrictive CM – myocardium shows patchy or diffuse fibrosis
In RCM the heart is about normal size and the myocardium is firm (“waxy” in amyloidosis).
Transplant arteriopathy is a long term complication (aka graft vascular disease, graft arteriosclerosis) – years to a decade or more – may cause sudden death
Acute cellular rejection is cell mediated and is controllable by drugs such as cyclosporine. Transplant vasculopathy on the other hand, may be mediated more by humoral means, and as yet is not controllable by drugs.
Congenital Heart Disease (CHD)
Def: Abnormality of heart or great vessels present at birth (although may be discovered as an adult)
Usually refers to structural abnormalities such as abnormal chamber and vessel relationships, abnormal connections (holes), obstructions, absence or maldevelopment of structures, and other anatomic abnormalities
By convention, usually does not include congenital tumors, infections, cardiomyopathies
Ranges from trivial (bicuspid aortic valve) to lethal (absent left ventricle)
If severe, causes delayed development, failure to thrive, increased susceptibility to infectious diseases in childhood, cardiac failure, and rarely sudden cardiac death
Increased risk for endocarditis (generally true for any structural abnormality, congenital or acquired; i.e. prosthetic valve)
Increased risk during pregnancy for women with CHD
Appendix II – Kawasaki Syndrome (Mucocutaneous Lymph Node Syndrome)
Kawasaki syndrome is rare, but it is the leading cause of acquired heart disease in children in the United States (great exam question?).
Kawasaki syndrome is an arteritis involving medium and small arteries, often unfortunately the coronary arteries.
The mucocutaneous lymph node syndrome in children is manifested by fever, conjunctival and oral erythema and erosion, erythema of the palms and soles, a skin rash often with desquamation, and enlargement of the cervical lymph nodes. It is usually self-limited.
Approximately 20% develop cardiovascular sequelae ranging from coronary artery ectasia to aneurysm formation to giant (>7 to 8 mm) aneurysm formation.
Death may occur in the acute phase of the disease or shortly thereafter due to coronary artery rupture or thrombosis, or aneurysms may persist after resolution of the acute disease and cause death years later.
The cause of Kawasaki’s is unknown, but it is probably a form of autoimmunity triggered by a variety of infections, most likely viral, in genetically susceptible individuals.