Imaging workup for shortness of breath

Dr Amit Chakraborty, Aug 2021

Introduction:

Shortness of breath or dyspnoea occurs when the cardiovascular and respiratory systems no longer meet the body’s oxygen requirements. Whilst this is largely multifactorial, the two primary causes are obviously the respiratory system and the cardiovascular system. Lack of haemoglobin may also be implicated with shortness of breath from time to time.

Causes of shortness of breath:

1. Cardiovascular system:

• Congestive cardiac failure
• Acute coronary syndrome
• Cardiomyopathy
• Pericardial effusion
• Other causes such as conduction abnormality (heart block), valve insufficiency or stenosis, vascular compromise such as coronary insufficiency, major mediastinal vessel abnormality

2. Respiratory system:

• Pulmonary disease: Airspace conditions such as pneumonia, pulmonary oedema, aspirationInterstitial disease such as interstitial inflammatory conditions (interstitial pneumonia, infiltrative disease such as sarcoidosis, silicosis), pulmonary fibrosisAirway limitation such as emphysema, asthma, bronchiectasis or chronic bronchitisPulmonary mass: Primary malignancy, metastatic deposits
• Pleural causes: Pleural effusion from a variety of aetiology, pleural disease such as asbestosis or pleural-based tumours
• Problems with major airway: Tracheobronchial fistula, bronchial flaps, growth within the airway such as bronchial adenoma, other conditions such as tracheomalacia
• Other airway problems: External compression from mediastinal lymphadenopathy or cervical lymphadenopathy, pharyngeal or laryngeal abnormalities such as parapharyngeal abscess, laryngeal adenoma or carcinoma

3. Other causes:

Pathology of the chest wall such as rib fracture, myopathy, abnormal shape such as pectus deformity, thoracic curvature problems such as accentuated kyphosis or marked scoliosis, pathology of the diaphragm such as diaphragmatic hernia, diaphragm paralysis or traumatic rupture of the diaphragm

Abdominal pathology: Marked organomegaly causing upward deviation of the diaphragm, large ascites preventing optimal thoracic expansion

Clinical approach:

A comprehensive history and physical examination will often narrow down the differential diagnosis list and point towards the potential cause of shortness of breath.

Imaging workup:

A number of imaging modalities are available for shortness of breath workup. The simplest of these is chest x-ray.

• Chest x-ray:It is the most commonly performed radiological examination. It is quick, simple and inexpensive way of getting a general idea about a patient’s respiratory and cardiovascular system.Advantages:Easily available, quickly obtained and inexpensive.Preliminary indication as to the nature of the problem (if any): Airspace opacity, interstitial changes, pleural effusion, chest wall abnormality, cardiac size, mediastinal contour, diaphragmatic shape and position, soft tissue abnormality, contour of the trachea as well as presence of absence of a mass in the neck.Disadvantage:Insensitive. Small pulmonary nodules, interstitial opacities, small pleural effusion, or small pericardial effusion are often not detectable on a chest x-ray.Dependent on patient position: The sensitivity is greatly reduced if the patient is unable to take a full breath or able to remain upright during the examination.
• CT scan of the chest:Another great tool in assessment of the cardiovascular system. The CT scan examines the lower neck, chest and the upper abdomen in great detail and can often pinpoint the exact cause of the patient’s symptoms. It can accurately detect and quantify airspace conditions, interstitial changes, pulmonary nodules, focal pulmonary mass lesions and pleural effusion.The study is usually performed with intravenous contrast medium. This allows optimal visualisation of the mediastinal great vessels and characterisation of mediastinal and perihilar lymphadenopathy, if any.The cardiac function can often be gleaned based on the dynamics of contrast medium. For example, if the contrast is administered via right arm and there is reflux of contrast in the IVC, it may suggest a degree of right heart dysfunction.Today’s CT scanners are able to obtain high quality diagnostic CT images at a dose that is only slightly more than a chest x-ray. Our ultra-low-dose CT scanners are able to acquire images very quickly with a single short breath-hold.CT scan of the chest would often include the upper abdomen and thus information about potential upper abdominal pathology can also be obtained without additional tests or dose penalty.
• High-resolution CT chest:This is often a second line investigation once the patient has seen a respiratory physician or has had an abnormal CT chest that requires further characterisation. The advantages of a high-resolution CT chest are that it is able to compensate for basal atelectasis. It is able to assess for air trapping and mobile chest masses.Simple assessment of interstitial disease pattern can often be achieved with a single phase (inspiratory) CT chest study. High-resolution chest CT scan is often not necessary.HRCT has the disadvantage of a higher dose. Multiple acquisitions are made, therefore the patient is imaged multiple times at an increased dose penalty.
• Examination of the chest wall:If chest pathology is suspected, ultrasound study may often be a very useful tool. It is able to accurately assess the muscles, pleural spaces (if containing fluid), skin and subcutaneous structures as well as vascularity. This can be supplemented with a chest CT examination which is able to accurately characterise and define rib fractures.
• Cardiac imaging:Significant recent improvements have been made in cardiac imaging. Both structural and physiological information can be obtained by a number of imaging studies available.A simple chest x-ray can often determine the shape and contour of the cardiac silhouette. Conditions such as cardiomyopathy or heart failure can result in an enlargement of the cardiac silhouette.Echocardiography:The popular belief is that echocardiography is the domain of the cardiologists. It is an ultrasound examination and thus appropriately trained radiologists are often able to perform and accurately interpret echocardiograms.Advantages of echocardiography performed at diagnostic imaging centre:
  Cardiac imaging:
  • Patient is usually able to get a much quicker appointment
  • The study report is usually available much earlier
  • The diagnostic accuracy is often similar or better than echocardiography performed at a dedicated cardiology centre.
  • Depending on the initial echocardiographic findings, the patient is often able to be referred to the suitable specialist or tertiary management centre

  Some of our radiologists have undergone extensive training on accreditation to perform echocardiography. Our radiologists are very happy to discuss the needs and the results with you in a timely fashion.

• Cardiac CT:Cardiac CT examination offers a non-invasive approach to accurately characterise the calcium burden of the coronary arteries. It is also able to accurately assess coronary artery stenosis and predict the risk of an acute coronary event. There are recent research articles that suggest that coronary CT examination is as sensitive and specific as a catheter coronary angiogram.CT pulmonary angiogram:This is a specialised CT scan of the chest where the images are acquired after contrast administration. The timing of the acquisition is much earlier than a conventional CT chest study which enables accurate visualisation of the pulmonary arteries and their branches down to the segmental levels. It remains the most sensitive and specific non-invasive method for detecting pulmonary embolism.Shortness of breath workup:We are able to perform most of the above imaging as dictated by clinical need: i.e. the patient only has to visit the imaging centre with one referral. Studies are performed in an expedient fashion and in most cases the reports are available on the same date via online login portal, fax or simply over the telephone to the referrer.