Respiratory

Pulmonary vascular disease

Pulmonary Embolism

Introduction

  • Always consider with acute or subacute onset of breathlessness where there are risk factors
  • Pulmonary embolism is a cause of sudden death

Aetiology

  • Hospitalised, pregnant, previous VTE and those with significant comorbidities
  • All hospitalised patients should be risk assessed and considered for prophylaxis.
  • PE occurs in 15-20 patients per 1000 in hospital or which 2-5 are fatal

Assessment

Assess the modified Wells criteria should be applied to determine if PE is unlikely (score <4) or likely (score >4)

The modified Wells Criteria include the following

  • Clinical Symptoms of DVT (3 points)
  • Other diagnosis less likely than PE (3 points)
  • Heart rate >100 (1.5 points)
  • Immobilization or surgery in previous four weeks (1.5 points)
  • Previous DVT/PE (1.5 points)
  • Haemoptysis (1 point)
  • Malignancy (1 point)

Clinical

  • Small emboli: If multiple and recurrent leads to progressive breathlessness and ultimately cor pulmonale and pulmonary hypertension
  • May be subtle with confusion especially in elderly.
  • Medium sized: Dyspnoea, possibly haemoptysis, pleuritic chest pain.
  • Large: Usually when blood to more than two lobes is obstructed
  • There is acute right heart failure with marked dyspnoea, urge to defaecate (often collapse in toilet), chest pain, tachycardia, raised JVP and loud P2 on auscultation
  • Blood gases show Type 1 respiratory failure and Echocardiogram may show RV dysfunction
  • Hypotension.

Risks

  • Old age, Obesity, Perioperative
  • Immobility e.g stroke, severe illness, spinal injury, Guillain-Barre syndrome, trauma
  • HONK, localised trauma, phlebitis, previous DVT/PE, Post MI, Pregnancy, Pelvic tumour
  • Procoagulant - Polycythaemia, sickle cell disease, Hyperviscosity, Protein C and S deficiencies, Smoking, malignancy, Oral contraceptive pill, HRT.

Investigations

  • FBC and U&E, LFT's typically normal.
  • Arterial Blood gases - low pO2 and low/normal PCO2 (Type 1 RF)
  • D-Dimer: Only those patients classified as low or intermediate risk of PE should undergo quantitative D-dimer testing
  • The rest should have imaging either VQ or CTPA
  • If the D-dimer level is below your local lab cut off level then the diagnosis of PE can be excluded
  • The D-Dimer test is sensitive but not specific for PE
  • It is elevated in infections, malignancies and other processes
  • It is a degradation product of cross-linked fibrin.
  • ECG findings: Commonest is a sinus tachycardia, New atrial fibrillation, Others include S1Q3T3 pattern, right ventricular strain, new incomplete right bundle branch block
  • ECG may be normal.
  • CXR - a normal CXR is entirely compatible with A large PE, segmental collapse, pleural effusion, area of lung infarction, raised hemidiaphragm, prominent pulmonary artery and a localised absence of vascular markings
  • CXR can be done in pregnancy with suitable shielding of fetus.
  • Troponin I/T are elevated in 30-50% of large PE's
  • Echocardiogram - Right atria and Right ventricle dilated, Tricuspid regurgitation.
  • V/Q scanning is used in many centres as the preferred initial imaging especially in pregnancy. However of less use when the CXR is abnormal. A ventilation scan is done using inhaled radioactive xenon gas
  • Perfusion is measured using radiolabelled albumin macro aggregates. These are then compared to look for areas of mismatch. A PE can be identified by an area of ventilation but low perfusion.
  • CT Pulmonary angiogram (CTPA)is the imaging modality of choice in almost all patients. In pregnancy concerns about radiation to the maternal breast (the fetus can be shielded)
  • Imaging of lower limb veins may find a DVT and so indirectly make the diagnosis especially when coupled with an elevated dimer
  • Alternatives include just doing a radioisotope perfusion scan but this exposes fetus to some radiation
  • Consult local guidelines in pregnancy

Management

  • ABCs - High FiO2 oxygen, analgesia, cardiac monitoring best in a CCU/ITU when compromised
  • Thrombolysis should be considered in a patient with a large compromising PE where there is hypotension or signs of RV dysfunction
  • Possible strategy is Alteplase 10 mg IV over 1-2 minutes followed by 90 mg over 2 hours. A lower dose is given for those under the 65 Kg
  • Enoxaparin is usually started at 1.5 mg/kg per day (reduced dose given with renal impairment)as soon as there is clinical suspicion and stopped when PE has been disproved
  • If a PE is identified then Enoxaparin is continued until INR > 2.0. 3-6 months warfarin therapy for a first Idiopathic PE is routine but possibly shorter where there is an identifiable temporary precipitant
  • There should be an overlap of warfarin and heparin for a few days as warfarin can cause a transient pro coagulant condition until fully Warfarinised.
  • IVC filters may be used where there is a high risk of VTE and anticoagulation is not possible in the short term. Newer devices can be removed after 6 weeks. Left in filters tend to clot off and can cause long term problems. Warfarin may be added if the bleed risk has subsided.
  • In pregnancy a CXR to exclude other pathology and USS should be done first as finding a DVT will necessitate anticoagulation. If negative then local policy will suggest either ventilation part of VQ scanning may be the safest. However it is important to make an accurate diagnosis and CTPA but here are worries about carcinogenesis on the pregnant breast.
  • Warfarin is teratogenic in pregnancy and LMWH is usually given. Nearer delivery IV heparin can be given and stopped prior to delivery and restarted afterwards
  • D-dimer is elevated in pregnancy but if normal may be useful - some advocate its use
  • Misdiagnosis and failure to treat must be balanced with risks of imaging and treatment
  • Recurrent PEs require lifelong warfarin

Cor Pulmonale

Introduction

  • Cor pulmonale is right ventricular failure secondary to chest disease

Aetiology

  • Hypoxia is a pulmonary vasoconstrictor

Causes

  • COPD in almost all cases
  • Primary pulmonary hypertension
  • Recurrent pulmonary emboli
  • Sickle cell disease
  • Bronchiectasis
  • Interstitial lung disease
  • Cystic fibrosis
  • Ankylosing spondylitis
  • Chronic Hypoventilation

Clinical

  • Progressive ascites, leg oedema, Elevated JVP
  • Loud P2 and RV S3, Parasternal heave, Hepatomegaly

Investigations

  • FBC ? polycythaemia
  • ABGs - hypoxia and possibly hypercarbia
  • ECG - AF, P pulmonale, RVH, RAD
  • CXR - prominent pulmonary artery
  • USS - hepatomegaly

Management

  • Carefully correct hypoxia, Diuretics may help fluid retention, Warfarin for PE's Steroids, bronchodilators for COPD
  • Smoking cessation, Pulmonary rehabilitation, Treat cause, Long term oxygen therapy

Pulmonary hypertension

Introduction

  • Increased pulmonary hypertension leads to right heart failure

Aetiology

  • Pressures in the pulmonary arterial circulation are much lower than systemic arterial pressures
  • The diagnosis of Pulmonary hypertension is based on the mean pulmonary arterial pressure > 25 mmHg at rest and 30 mmHg at exercise.
  • Pulmonary hypertension may be primary or secondary depending on whether a secondary cause can be found.

Clinical

  • Findings include Loud P2 (Pulmonary valve closure) and Right sided S3, RV heave
  • Large 'a' wave in JVP, TR and large 'v' wave in JVP and a Pulmonary systolic flow murmur

Investigations

  • ECG - RVH and RBBB and P pulmonale
  • CXR - enlarged PA + pruning of peripheral vessels
  • Echocardiogram - RV dilatation and TR
  • Catheter studies to assess right sided pressures in some
  • CT-PA - may suggest diagnosis of recurrent PE as a cause
  • Lung biopsy - pathology shows plexiform lesions and in situ thrombosis

Primary Pulmonary hypertension

Introduction

  • A rare disease causing an increase in pulmonary hypertension with no obvious cause

Aetiology

  • There appears to be an Autosomal dominant familial type with a mutation in the type II bone morphogenetic protein receptor gene (BMPR2)
  • Primarily affects predominately women aged 20-30 with

Clinical

  • Progressive fatigue and breathlessness and right heart failure and death.

Investigations

  • CXR
  • Cardiac catheterisation to measure right sided pressures
  • Echocardiography
  • Lung biopsy in some

Management

  • Oxygen for hypoxia
  • All patients should be anticoagulated with warfarin as this improves prognosis in severe pulmonary hypertension
  • Consider digoxin, diuretics and oxygen
  • Some respond well to high dose calcium channel blockers - only those with evidence of response should be continued on them such as Amlodipine 20 mg/day or Nifedipine 240 mg /day
  • Iloprost therapy (Prostacyclin) by infusion or nebulized to those with NYHA classification III or IV
  • Endothelin receptor antagonists Bosentan
  • Sildenafil (viagra) has been used and has effects similar to nitric oxide
  • Single or double-lung transplant or Heart lung transplantation
  • Advice is that Pregnancy contraindicated, Exercise limited, Avoid flying / hypoxia and Venesect significant polycythaemia

Secondary Pulmonary hypertension

Introduction

  • There is an identifiable cause usually lung disease
  • Cor pulmonale is really secondary pulmonary hypertension due to hypoxic vasoconstriction of pulmonary vessels and parenchymal and vascular changes - Emphysema most commonly
  • There is chronic elevation of pulmonary artery pressure above 25 mmHg at rest or > 30 mmHg with exercise although the WHO definition raises the systolic pulmonary artery pressure to 40 mmHg

Causes

  • Chronic Obstructive Pulmonary disease
  • Interstitial lung disease
  • Idiopathic -Primary Pulmonary Hypertension
  • Multiple Pulmonary emboli
  • Congenital heart disease with Eisenmenger's
  • Mitral stenosis
  • Weakness of respiratory muscles
  • Chest wall deformities
  • Sickle cell disease
  • Dexfenfluramine
  • Left Ventricular Failure
  • Left atrial myxoma
  • Living at High altitude
  • Scleroderma.

Investigations

  • ECG - RVH and RBBB and P pulmonale
  • CXR - enlarged PA + pruning of peripheral vessels
  • Echo - RV dilatation and TR
  • Mean pulmonary artery pressure readings mean > 25 mmHg at rest.
  • CT-PA - may suggest diagnosis of recurrent PE as a cause

Management

  • Long term oxygen therapy to reduce the hypoxaemia and pulmonary vasoconstriction is indicated as well as to improve morbidity and decrease mortality
  • Diuretics are used but care so as not to reduce volume that impairs RV filling
  • ACE inhibitors have little effect and may worsen the situation and there is no evidence either for low dose Beta-Blockers
  • Warfarin is indicated in those for when the cause is unknown or the cause is thrombotic e.g Multiple PEs, presence of AF or veno-occlusive disease.