Acute breathlessness: a teaching case in clinical reasoning

The presentation

A 72-year-old woman becomes breathless over two days, worse lying flat, waking her at night, with swollen ankles. She has a history of high blood pressure and a previous heart attack. The pattern here — breathlessness on lying flat (orthopnoea), waking at night gasping (paroxysmal nocturnal dyspnoea) and ankle swelling — is characteristic and immediately shifts the differential towards the heart rather than the lungs.

The main differentials

Acute breathlessness in an older adult usually comes down to a handful of causes: heart failure (the heart cannot pump efficiently, so fluid backs up into the lungs), an exacerbation of COPD or asthma, pneumonia, a pulmonary embolism, or an arrhythmia such as fast atrial fibrillation. Anaemia and anxiety can contribute. Each has distinguishing features: fever and productive cough suggest infection; wheeze suggests airways disease; pleuritic pain with risk factors suggests embolism; orthopnoea and oedema suggest heart failure.

Tests that separate the causes

A focused set of investigations does most of the sorting. A chest X-ray can show the congestion and enlarged heart of failure, the consolidation of pneumonia, or a pneumothorax. Blood tests include a BNP or NT-proBNP (a hormone raised in heart failure — a low value makes it unlikely), inflammatory markers for infection, and a D-dimer where embolism is being considered. An ECG looks for arrhythmia or evidence of a new cardiac event, and oxygen saturation and blood gases gauge severity. A bedside echocardiogram, where available, directly assesses heart function.

Reaching a working diagnosis

In this case the examination reveals crackles at both lung bases, a raised jugular venous pressure and pitting ankle oedema; the chest X-ray shows pulmonary congestion and the NT-proBNP is markedly raised. Together these point to acute heart failure with fluid overload. Management is guided by NICE heart-failure pathways — oxygen if needed, diuretics to remove excess fluid, close monitoring, and then addressing the underlying cause and optimising long-term heart-failure medicines. Crucially, the treatment (removing fluid) is almost the opposite of what a severe asthma attack would need, which is why getting the differential right matters.

What the case teaches

Breathlessness is a final common pathway for many conditions, and the history frequently points the way before any test returns. The discipline is to hold several differentials at once, choose tests that discriminate between them, and treat the most likely and most dangerous causes in parallel while confirming the diagnosis. As always, severity assessment — how hard the person is working to breathe, and their oxygen levels — drives the urgency of the response.