The lung circulation offers a low resistance to flow compared to the systemic circulation and the normal mean pulmonary artery pressure at rest is 1014 mmHg (compared to mean systemic arterial pressure of about 90 mmHg). Pulmonary hypertension is characterized by elevated pulmonary artery pres-sure (> 25 mmHg at rest) and secondary right ventricular failure.
Pulmonary hypertension occurs due to an increase in pulmonary vascular resistance or an increase in pulmonary blood flow. Specific causes are listed in Table 10.13.
Exertional dyspnoea, lethargy and fatigue are the initial symptoms due to an inability to increase cardiac output with exercise. As right ventricular
|Table 10.13 Causes of pulmonary hypertension|
|Pulmonary arterial hypertension:|
Idiopathic (no cause indentified)
Systemic sclerosis, systemic lupus erythematosus, rheumatoid arthritis
Drugs: long term use of cocaine and amphetamines, dexfenfluramine
Portal hypertension (portopulmonary hypertension)
Congenital heart disease with systemic-to-pulmonary communication (atrial septal defect, ventricular septal defect)
Chronic haemolytic anaemia
Pulmonary veno-occlusive disease
|Pulmonary hypertension secondary to:|
|Left heart disease: valvular, systolic dysfunction, diastolic dysfunction
Lung disease and/or hypoxia, e.g. chronic obstructive pulmonary disease, obstructive sleep apnoea, lung fibrosis
Thromboembolic occlusion of proximal or distal pulmonary vasculature
Multifactorial mechanisms: myeloproliferative disorders, sarcoidosis, glycogen storage disease
failure develops there is peripheral oedema and abdominal pain from hepatic congestion. On examination there is a loud pulmonary second sound, and a right parasternal heave (caused by right ventricular hypertrophy). In advanced disease there are features of right heart failure (cor pulmonale): elevated jugular venous pressure with a prominent V wave if tricuspid regur-gitation is present, hepatomegaly, a pulsatile liver, peripheral oedema, ascites and a pleural effusion. There are also features of the underlying disease.
The aim of investigation is to confirm the presence of pulmonary hypertension and demonstrate the cause:
■ Chest X-ray shows enlarged proximal pulmonary arteries which taper distally. It may also reveal the underlying cause (e.g. emphysema, calci-fied mitral valve).
■ ECG shows right ventricular hypertrophy and P pulmonale (p. 411).
■ Echocardiography shows right ventricular dilatation and/or hypertrophy and may also reveal the cause of pulmonary hypertension, e.g. intra-cardiac shunt. It is possible to measure the peak pressure with Doppler echocardiography.
The initial treatment is oxygen, warfarin (due to a higher risk of intrapulmo-nary thrombosis), diuretics for oedema and oral calcium-channel blockers as pulmonary vasodilators, together with treatment of the underlying cause. In more advanced disease treatment is aimed at decreasing pulmonary vascular resistance and includes oral endothelin receptor antagonists (bosenten, sitax-entam), prostanoid analogues (inhaled iloprost, treprostinil, beraprost), intra-venous epoprostenol and oral sildenafil. In primary pulmonary hypertension there is a progressive downhill course and many patients ultimately require heart and lung transplantation.
Pulmonary embolism (PE)
PE is a common and potentially lethal condition. Unfortunately the diagnosis is often missed because the presenting symptoms are vague or non-specific. Emboli usually arise from thrombi in the iliofemoral veins (deep venous thrombosis, p. 487). The risk factors for thromboembo-lism are listed on page 238. Rarely PE results from clot formation in the right heart.
A massive embolism obstructs the right ventricular outflow tract and therefore suddenly increases pulmonary vascular resistance, causing acute right heart failure. A small embolus impacts in a terminal, peripheral pulmonary vessel and may be clinically silent unless it causes pulmonary infarction. Lung tissue is ventilated but not perfused, resulting in impaired gas exchange.
■ Small/medium PEs present with breathlessness, pleuritic chest pain, and haemoptysis if there is pulmonary infarction. On examination the patient may be tachypnoeic and have a pleural rub and an exudative (occasionally bloodstained) pleural effusion can develop.
■ Massive PE presents as a medical emergency: the patient has severe central chest pain and suddenly becomes shocked, pale and sweaty, with marked tachypnoea and tachycardia. Syncope and death may follow rapidly. On examination the patient is shocked, with central cyanosis. There is elevation of the jugular venous pressure, a right ventricular heave, accentuation of the second heart sound and a gallop rhythm (acute right heart failure).
■ Multiple recurrent PEs present with symptoms and signs of pulmonary hypertension (see above), developing over weeks to months.
A clinical pre-test probability score of PE is used prior to investigation (Table
10.14) which helps to decide on the most appropriate first-line diagnostic test and interpretation of the results (Emergency Box 10.5):
■ Chest X-ray, ECG and blood gases may all be normal with small/medium emboli and any abnormalities with massive emboli are non-specific. The chest X-ray and ECG are useful to exclude other conditions that may present similarly. The chest X-ray may show decreased vascular mark-ings and a raised hemidiaphragm (caused by loss of lung volume). With pulmonary infarction, a late feature is the development of a wedge-shaped opacity adjacent to the pleural edge, sometimes with a pleural effusion. The commonest ECG finding is sinus tachycardia or there may be new onset atrial fibrillation. The features of acute right heart strain
Table 10.14 Revised Geneva score for the clinical prediction of a pulmonary embolism
Age > 65 years
Previous deep venous thrombosis or pulmonary embolism
Surgery or fracture within 1 month
Unilateral leg pain
Heart rate (b.p.m.)
Pain on leg deep vein palpation and unilateral oedema
NB: diagnosis of pulmonary embolism is not excluded on this basis alone; about 8% of
may be seen: tall peaked P waves in lead II, right axis deviation and right bundle branch block. Arterial blood gases show hypoxaemia and hypo-capnia with massive emboli.
■ Plasma D-dimers are a subset of fibrinogen degradation products released into the circulation when a clot begins to dissolve. D-dimers are, however, elevated in many other conditions (e.g. cancer, pregnancy, post-operatively) and a positive result is not diagnostic of thromboembolic disease. The value of D-dimer testing is in patients with a low pre-test clinical probability score (Table 10.14 and Emergency Box 10.5).
■ Spiral CT with intravenous contrast (CT pulmonary angiography, CTPA) images the pulmonary vessels directly and is highly sensitive for the detection of large proximal pulmonary emboli. It is increasingly being used as the diagnostic test of choice for patients with suspected PE. Subsegmental emboli may be missed and occasionally patients may need further imaging (Emergency Box 10.5). One of the benefits over V/Q scan is the ability to detect alternative pathology that may explain the clinical presentation.
■ Radionuclide lung scan (V/Q scan) demonstrates areas of ventilated lung with perfusion defects (ventilation-perfusion defects). Pulmonary embo-lism is excluded in patients with a normal scan. However, there is high incidence of non-diagnostic scans especially in patients with coexistent chronic lung disease who will then need further imaging.
■ Ultrasound will detect clots in the pelvic or iliofemoral veins.
■ MRI gives similar results and is used if CT is contraindicated.
■ Echocardiography is diagnostic in massive PE and can be performed at the bedside. It demonstrates proximal thrombus and right ventricular dilatation.
This is summarized in Emergency Box 10.5. At present, the only definite indication for thrombolysis in acute massive embolism is persistent arterial hypotension. Surgical embolectomy is occasionally undertaken if thrombo-lysis is contraindicated or ineffective. In contrast, patients who are cardio-vascularly stable and who have no co-existent serious medical pathology can be treated at home once the diagnosis is conữmed. Anti-coagulation is continued for 6 weeks to 6 months (see p. 246) depending on the likelihood of recurrence of thromboembolism, and lifelong treatment is indicated for recurrent emboli. Insertion of a vena caval filter is used to prevent further emboli when emboli recur despite adequate anticoagulation or in high-risk individuals where anti-coagulation is contraindicated.
Pulmonary embolism in pregnancy
Pulmonary embolism occurs more frequently in pregnancy and is the leading cause of maternal death in the developed world. Compression ultrasonography of the legs is the initial investigation. CTPA is required if ultrasound is normal and delivers a lower dose of radiation to the fetus than V'IQ scanning. Warfarin is teratogenic and confirmed PE is treated with LMWH.
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
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BODY FLUID COMPARTMENTS
REGULATION OF BODY FLUID HOMEOSTASIS
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DISORDERS OF POTASSIUM REGULATION
DISORDERS OF MAGNESIUM REGULATION
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INVESTIGATION OF RENAL DISEASE
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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
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11. Respiratory disease
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THE THIRST AXIS
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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
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HEADACHE, MIGRAINE AND FACIAL PAIN
SPINAL CORD DISEASE
DEGENERATIVE NEURONAL DISEASES
DISEASES OF THE PERIPHERAL NERVES