Cardiomyopathies comprise a group of diseases of the myocardium that affect the mechanical (hypertrophic, arrhythmogenic right ventricular, dilated and restrictive cardiomyopathy) or electrical function (conduction system disease and ion channelopathies, e.g. long QT syndrome) of the heart. Diagnosis of myocardial disease is usually by imaging (echocardiogram and cardiac MR).
Hypertrophic cardiomyopathy (HCM)
HCM is characterized by marked ventricular hypertrophy in the absence of abnormal loading conditions such as hypertension and valvular disease. There is usually disproportionate involvement of the interventricular septum. The hypertrophic non-compliant ventricles impair diastolic filling, so that stroke volume is reduced. Most cases are familial, autosomal dominant, and caused by mutations in genes encoding sarcomeric proteins, e.g. troponin T and β-myosin. It is the most common cause of sudden cardiac death in young people.
Patients may be symptom-free (and detected through family screening) or have breathlessness, angina or syncope. Complications include sudden death, atrial and ventricular arrhythmias, thromboembolism, infective endo-carditis and heart failure. The carotid pulse is jerky because of rapid ejection and sudden obstruction to the ventricular outflow during systole. An ejection systolic murmur occurs because of left ventricular outflow obstruction, and the pansystolic murmur of functional mitral regurgitation may also be heard.
■ ECG is almost always abnormal. A pattern of left ventricular hypertrophy with no discernible cause is diagnostic.
■ Cardiac imaging shows ventricular hypertrophy (on echo and MR) and fibrosis (on MR).
■ Genetic analysis may confirm the diagnosis and provide prognostic information.
Amiodarone reduces the risk of arrhythmias and sudden death. Individuals at highest risk are fitted with an implantable cardiac defibrillator. Chest pain and dyspnoea are treated with β-blockers and verapamil. In selected cases outflow tract gradients are reduced by surgical resection or alcohol ablation of the septum, or by dual-chamber pacing.
Dilated cardiomyopathy (DCM)
DCM is characterized by a dilated left ventricle which contracts poorly. Inheritance is autosomal dominant in the familial disease.
Shortness of breath is usually the first complaint; less often patients present with embolism (from mural thrombus) or arrhythmia. Subsequently there is progressive heart failure with the symptoms and signs of biventricular failure.
■ Chest X-ray may show cardiac enlargement.
■ ECG is often abnormal. The changes are non-specific and include arrhyth-mias and T-wave flattening.
■ Cardiac imaging shows dilated ventricles with global hypokinesis. Cardiac MR may show other aetiologies of left ventricular dysfunction, e.g. previ-ous myocardial infarction.
Other tests such as coronary angiography, viral and autoimmune screen and endomyocardial biopsy may be needed to exclude other diseases (Table 10.15) that present with the clinical features of DCM.
Heart failure and atrial fibrillation are treated in the conventional way (pp. 440, 429). Cardiac resynchronization therapy and implantable cardiac defi-brillators are used in patients with NYHA III/IV grading. Severe cardiomyopa-thy is treated with cardiac transplantation.
Primary restrictive cardiomyopathy
The rigid myocardium restricts diastolic ventricular filling and the clinical features resemble those of constrictive pericarditis (see later). In the UK the most common cause is amyloidosis. The ECG, chest X-ray and echocardio-gram are often abnormal, but the findings are non-specific. Diagnosis is by cardiac catheterization, which shows characteristic pressure changes. An endomyocardial biopsy may be taken during the catheter procedure, thus providing histological diagnosis. There is no specific treatment and the prog-nosis is poor, with most patients dying less than a year after diagnosis. Cardiac transplantation is performed in selected cases.
Arrhythmogenic right ventricular cardiomyopathy
There is Progressive fibro-adipose replacement of the wall of the right ven-tricle. The typical presentation is ventricular tachycardia or sudden death in a young man.
|Table 10.15 Heart muscle disease presenting with features of dilated cardiomyopathy|
Congenital heart disease
Iníections, e.g. cytomegalovirus, HIV
1. Ethics and communication
2. Infectious diseases
3. Gastroenterology and nutrition
4. Liver, biliary tract and pancreatic disease
Liver, biliary tract and pancreatic disease
LIVER BIOCHEMISTRY AND LIVER FUNCTION TESTS
SYMPTOMS AND SIGNS OF LIVER DISEASE
NON - ALCOHOLIC FATTY LIVER DISEASE (NAFLD)
COMPLICATIONS AND EFFECTS OF CIRRHOSIS
TYPES OF CHRONIC LIVER DISEASE AND CIRRHOSIS
PRIMARY SCLEROSING CHOLANGITIS
BUDD - CHIARI SYNDROME
LIVER DISEASE IN PREGNANCY
CARCINOMA OF THE PANCREAS
NEUROENDOCRINE TUMOURS OF THE PANCREAS
5. Haematological disease
Assessment and treatment of suspected neutropenic sepsis
INHERITED HAEMOLYTIC ANAEMIAS
ACQUIRED HAEMOLYTIC ANAEMIA
THE WHITE CELL
HAEMOSTASIS AND THROMBOSIS
6. Malignant disease
COMMON INVESTIGATIONS IN MUSCULOSKELETAL DISEASE
COMMON REGIONAL MUSCULOSKELETAL PROBLEMS
THE SERONEGATIVE SPONDYLOARTHROPATHIES
Clinical features, Investigations
INFECTION OF JOINTS AND BONES
AUTOIMMUNE RHEUMATIC DISEASES
SYSTEMIC INFLAMMATORY VASCULITIS
DISEASES OF BONE
8. Water, electrolytes and acid–base balance
WATER AND ELECTROLYTE REQUIREMENTS
BODY FLUID COMPARTMENTS
REGULATION OF BODY FLUID HOMEOSTASIS
PLASMA OSMOLALITY AND DISORDERS OF SODIUM REGULATION
DISORDERS OF POTASSIUM REGULATION
DISORDERS OF MAGNESIUM REGULATION
DISORDERS OF ACID - BASE BALANCE
9. Renal disease
INVESTIGATION OF RENAL DISEASE
URINARY TRACT INFECTION
HYPERTENSION AND THE KIDNEY
RENAL CALCULI AND NEPHROCALCINOSIS
URINARY TRACT OBSTRUCTION
ACUTE RENAL FAILURE/ACUTE KIDNEY INJURY
CHRONIC KIDNEY DISEASE
RENAL REPLACEMENT THERAPY
CYSTIC RENAL DISEASE
TUMOURS OF THE KIDNEY AND GENITOURINARY TRACT
DISEASES OF THE PROSTATE GLAND
10. Cardiovascular disease
COMMON PRESENTING SYMPTOMS OF HEART DISEASE
INVESTIGATIONS IN CARDIAC DISEASE
ISCHAEMIC HEART DISEASE
VALVULAR HEART DISEASE
PULMONARY HEART DISEASE
ARTERIAL AND VENOUS DISEASE
DRUGS FOR ARRHYTHMIAS
DRUGS FOR HEART FAILURE
DRUGS AFFECTING THE RENIN - ANGIOTENSIN SYSTEM
NITRATES, CALCIUM - CHANNEL BLOCKERS AND POTASSIUM - CHANNEL ACTIVATORS
11. Respiratory disease
12. Intensive care medicine
13. Drug therapy, poisoning, and alcohol misuse
14. Endocrine disease
PITUITARY HYPERSECRETION SYNDROMES
THE THYROID AXIS
MALE REPRODUCTION AND SEX
FEMALE REPRODUCTION AND SEX
THE GLUCOCORTICOID AXIS
THE THIRST AXIS
DISORDERS OF CALCIUM METABOLISM
DISORDERS OF PHOSPHATE CONCENTRATION
ENDOCRINOLOGY OF BLOOD PRESSURE CONTROL
DISORDERS OF TEMPERATURE REGULATION
15. Diabetes mellitus and other disorders of metabolism
16. The special senses
COMMON NEUROLOGICAL SYMPTOMS
COORDINATION OF MOVEMENT
THE CRANIAL NERVES
COMMON INVESTIGATIONS IN NEUROLOGICAL DISEASE
UNCONSCIOUSNESS AND COMA
STROKE AND CEREBROVASCULAR DISEASE
EPILEPSY AND LOSS OF CONSCIOUSNESS
NERVOUS SYSTEM INFECTION AND INFLAMMATION
HEADACHE, MIGRAINE AND FACIAL PAIN
SPINAL CORD DISEASE
DEGENERATIVE NEURONAL DISEASES
DISEASES OF THE PERIPHERAL NERVES