Page 72 - Medicine and Surgery

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68 Chapter 2: Cardiovascular system

Management Investigations
If there is compromise of the cardiac output, needle as- Chest X-ray may show cardiac enlargement.
piration of the pericardium should be performed via the ECG may show ST and T wave abnormalities and ar-
xiphisternal route, preferably under radiographic guid- rhythmias.
ance. The needle is inserted 1 cm below the xiphister- Cardiac enzymes are elevated.
num and angled to point towards the left shoulder (45˚). Cardiac biopsy shows acute inflammation.
If the ECG is left in place, with the V lead attached to the ViralIgM antibody titres may be increased.
needle, penetration of the myocardium shows up as ST
elevation. The relief following pericardiocentesis is often Management
temporary, so a fine catheter should be inserted for con- Bed rest and eradication of the acute infection, i.e. sup-
tinuous drainage until the underlying condition is cor- portive therapy. Cardiac failure and arrhythmias may
rected. Definitive surgery is required if needle drainage need treatment.
is unsuccessful.
Prognosis
Disorders of the myocardium Depending on the aetiology the prognosis is usually
good,althoughachroniccardiomyopathymayoccasion-
Myocarditis ally result.
Definition
An acute or chronic inflammatory disorder of the my- Cardiomyopathies
ocardium.
These are diseases of the heart muscle, which may be
primary (intrinsic to myocardium) or secondary (due
Aetiology
to an external or systemic cause).
Myocarditis is often a feature of a systemic infection but
Primary cardiomyopathies include dilated cardiomy-
occasionally septicaemia may lead to focal suppurative
opathy, hypertrophic cardiomyopathy and restrictive
lesions. Known causative factors:
cardiomyopathy. They are classified according to the
Viruses: Coxsackie, cytomegalovirus.

functional abnormality and are described below.
Protozoa: Trypanosoma cruzi (Chagas’ disease), Toxo- Secondary cardiomyopathies occur when ventricular

plasma gondii.
dysfunction results from ischaemia (ischaemic car-
Radiation chemicals and drugs, e.g. cytotoxic agents.

diomyopathy), poorly controlled hypertension (hy-
Bacterial infection, e.g. Corynebacterium, Coxiella.

pertensive cardiomyopathy), valvular disease (valvu-
Myocarditisisanimportantfeatureofrheumaticfever.

lar cardiomyopathy) or other systemic diseases such
as thyrotoxicosis, chronic anaemia, drugs or toxins,
Pathophysiology
viruses and alcohol.
Myocarditis may arise by direct effect, toxin or im-
munopathology.
Dilated cardiomyopathy
Clinical features
Myocarditis is an acute illness characterised by fever and Definition
cardiac failure. Patients often experience chest pain due Progressive ventricular dilatation with normal coronary
to an associated pericarditis. Signs include soft heart arteries.
sounds, third sound, tachycardia and often a pericar-
dial friction rub. Myocarditis may be complicated by Aetiology
arrhythmias. Most cases are idiopathic but are often assumed to fol-
low an undiagnosed viral myocarditis. The commonest
Microscopy identifiable cause is high alcohol intake. Other factors:
The myocardium shows an acute inflammatory reaction Genetic: Single gene mutations and skeletal muscular
with interstitial oedema and cellular infiltration. dystrophies.