Table 4. Specialised investigations for chronic dyspnoea.

Investigation	Possible diagnoses
Cardiopulmonary exercise testing	Deconditioning, obesity, psychogenic dyspnoea, cardiac or respiratory disease
Holter monitor	Arrhythmia
Cardiac MRI	Cardiomyopathy, diastolic dysfunction, intra-cardiac thrombus, valvular heart disease
Myocardial perfusion scan, stress echocardiogram, CT coronary angiogram	Coronary ischaemia, cardiac failure
Cardiac catheterisation (coronary angiography, right heart catheterisation, dynamic haemodynamic analysis)	Coronary artery disease, pulmonary hypertension, valvular heart disease, cardiomyopathy, heart failure with preserved ejection fraction, constrictive pericardial disease, restrictive cardiomyopathy
Bronchoscopy or surgical lung biopsy	Pulmonary malignancy, infection, inflammatory processes, interstitial disease processes, sarcoidosis
V/Q scan	Acute or chronic thromboembolism
FeNO	Asthma
Lung ultrasound	Pleural effusion, pulmonary oedema
Thoracocentesis	Pleural effusion
CT sinuses	Chronic sinusitis, upper airway obstruction
Upper gastrointestinal endoscopy, oesophageal pH monitoring	Gastro-oesophageal reflux disease, aspiration pneumonitis
Muscle biopsy	Myopathies

MRI, magnetic resonance imaging; CT, computed tomography; V/Q ventilation/perfusion; FeNO, fraction of exhaled nitric oxide.