Breathlessness, cardiac or respiratory?

Ed: It’s a common clinical dilemma – working out if breathlessness is cardiac or respiratory!

When identifying the causes of breathlessness the checklist of possibilities cover most of the biology of the respiratory and cardiac systems, mental health, and haematological and renal factors. Breathlessness might occur at any point on the continuum from oxygen supply to the lungs to its consumption by the tissues. For the clinician trying to sort out a predominant cardiac cause of breathlessness from a respiratory one going through Table 1 may help – it contains a non-exhaustive list of possible mechanisms.

Table 1. Causes of breathlessness

Cardiac	Increased left-sided intracavity filling pressure heart failure due to myocardial dysfunction (HFrEF, HFpEF)* left-sided valvular dysfunction (aortic or mitral stenosis or regurgitation) acute or recent myocardial ischaemia* Arrhythmia* (tachyarrhythmia, bradyarrhythmia, ectopy, AF, atrioventricular disassociation) Low cardiac output (left-sided): pulmonary hypertension hypovolaemia cardiac shunt cardiac compression (pericardial constriction, cardiac tamponade, tension pneumothorax)
Respiratory	Hypoxia pulmonary parenchymal abnormality – infection (pneumonia*), fibrosis, destruction (emphysema), oedema, alveolar haemorrhage and compression (pleural effusion and pneumothorax) airway obstruction (asthma*, bronchitis, upper airway) ventilation–perfusion mismatch (pulmonary embolus and pulmonary shunt) Central respiratory drive abnormality (pharmacological, metabolic) Musculoskeletal respiration abnormality skeletal myopathy respiratory muscle fatigue chest wall abnormality (kyphoscoliosis, thoracic skeletal pain and obesity*)
Peripheral muscle oxygen extraction abnormality or inefficiency	Poor physical fitness* Myopathy
Anxiety	Panic attack, chronic anxiety state
Anaemia, iron deficiency*
Hyperventilation	Acidosis (renal failure, ketoacidosis, shock) Pharmacological cause Thyrotoxicosis

∗ Common and potentially reversible factors that contribute to breathlessness; AF=atrial fibrillation, HFpEF= heart failure with preserved ejection fraction; HFrEF= heart failure with reduced ejection fraction.

Breathlessness assessment

Evaluation of a patient presenting with breathlessness will vary dependent on clinical situation such as acuity, age of the patient and their prior medical history.

The case history should determine the duration and severity – based on the New York Heart Association functional classification – of breathlessness and whether there are predisposing factors (e.g. effort and emotion).

If heart failure is suspected, the GP should enquire as to whether the patient has orthopnoea, paroxysmal nocturnal dyspnoea or associated symptoms such as chest pain, palpitations, dizziness, syncope, swollen ankles and abdominal bloating. Physical examination should include assessment of vital signs (heart rate and rhythm, blood pressure, respiratory rate and temperature), peripheral perfusion, volume status (JVP, peripheral and sacral oedema, ascites and hepatic congestion), cardiac palpitation and auscultation (apex beat, gallop rhythm and murmurs) and auscultation of lung fields (air entry, crackles and wheeze).

Basic investigations include non-invasive measurement of oxygen saturation, 12-lead ECG, chest X-ray, serum biochemistry (electrolytes, renal function and liver function) and full blood count. Further investigations will depend on clinical circumstances and findings from the initial clinical workup.

Requirement for more urgent evaluation or referral

Table 2. When to consider early referral (red flags)

Symptoms	Orthopnoea Paroxysmal nocturnal dyspnoea Syncope Ischaemic chest pain
Signs	Tachycardia (heart rate >100 beats/min.) Bradycardia (heart rate <40 beats/min.) Hypotension (systolic BP <90 mmHg) Hypoxaemia Gallop rhythm Significant heart murmur
Investigations	Evidence of ischaemia or infarction on 12-lead ECG Pulmonary oedema on chest X-ray Raised cardiac troponin level Moderate or severe valvular heart disease on echocardiography Left Ventricular Ejection Fraction ≤40% Ischaemia on stress testing

BP=blood pressure, ECG=electrocardiogram, Both tables Reproduced from National Heart Foundation of Australia and Cardiac Society of Australia and New Zealand: Guidelines for the Prevention, Detection, and Management of Heart Failure in Australia 2018.

To assist identifying patients with Heart Failure and then to focus on how to manage worsening symptoms refer to the updated national guidelines. www.heartfoundation.org.au/for-professionals/clinical-information/heart-failure. For the full text see https://www.heartlungcirc.org/article/S1443-9506(18)31777-3/fulltext

Acknowledgement: The author wishes to acknowledge the assistance provided by Assoc/Prof Tom Briffa, Director, Centre for Health Services & Cardiovascular Research Groups, Perth, in preparing this article.

References available on request.

Questions? Contact the editor.

Author competing interests: nil relevant disclosures.

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