Clinical reasoning notes. The point of an investigation is the question it answers.
The reasoning chain: is it really heart failure → what type (reduced or preserved ejection fraction) → what caused it → what tipped the patient into this episode → what is it doing to other organs.
1. Which tests?
| Test | The question it answers |
|---|---|
| NT-proBNP or BNP | Is this heart failure? A normal level makes it unlikely |
| Echocardiogram | Confirms the diagnosis; ejection fraction (reduced or preserved); the valves (rheumatic heart disease); the cause |
| ECG | Ischaemia, arrhythmia (atrial fibrillation), left ventricular hypertrophy |
| Chest X-ray | Pulmonary oedema, cardiomegaly, pleural effusions |
| Full haemogram | Anaemia, which worsens or can cause heart failure |
| Urea, creatinine, electrolytes | Kidney function before starting diuretics or ACE inhibitors; potassium |
| Liver tests, thyroid tests, glucose, lipids | Congestive liver disease; a thyroid cause; risk factors |
| Troponin | Is an acute coronary syndrome the trigger? |
| HIV test | HIV cardiomyopathy |
2. Then ask the two questions that matter
What caused it? Hypertension, rheumatic heart disease, ischaemic heart disease, cardiomyopathy (including HIV, peripartum, alcohol, and dilated cardiomyopathy of unknown cause), anaemia, thyroid disease, pericardial disease.
What precipitated this episode? Infection, missed drugs, arrhythmia (new atrial fibrillation), a heavy salt load, NSAIDs, anaemia, a new ischaemic event.
3. Features to recognise
- Left heart failure: breathlessness, orthopnoea, paroxysmal nocturnal dyspnoea, basal crackles, third heart sound.
- Right heart failure: raised JVP, ankle swelling, tender enlarged liver, ascites.
- Look for the cause on examination: a murmur, an irregular pulse, goitre, pallor.
4. Management in outline
- Treat the congestion: loop diuretics, oxygen if hypoxic, sit the patient up.
- Treat the cause and the trigger: control blood pressure, rate or rhythm, treat infection, correct anaemia, repair or replace a diseased valve.
- Long-term therapy for reduced ejection fraction (each class reduces deaths or admissions): ACE inhibitor or ARB, beta-blocker, mineralocorticoid antagonist, and an SGLT2 inhibitor where available.
- Avoid NSAIDs, and be careful with fluids and with some calcium channel blockers.
- Teach daily weights, salt and fluid advice, and adherence. Follow up in a heart failure clinic.
5. Where tests can mislead
- BNP is raised in kidney failure, atrial fibrillation, older age and pulmonary embolism, and lower in obesity. Interpret it with the picture.
- A normal chest X-ray does not exclude heart failure.
- Check the creatinine and potassium again 1 to 2 weeks after starting an ACE inhibitor or a mineralocorticoid antagonist.
Examiner questions
- A patient is breathless and the BNP is normal. How likely is heart failure?
- Name four precipitants of an acute episode in a known heart failure patient.
- Why do you want a haemoglobin and thyroid tests in heart failure?
Practice questions
1. The investigation that best separates reduced from preserved ejection fraction is: A. Chest X-ray · B. ECG · C. BNP · D. Echocardiogram · E. Troponin Answer: D.
2. Which investigation gives a clue that a patient with new heart failure may have a treatable cause such as HIV? A. Troponin · B. HIV test · C. Lipid profile · D. Urinalysis · E. Peak flow Answer: B.
3. Which drug should be avoided in heart failure because it causes fluid retention? A. Furosemide · B. Bisoprolol · C. Enalapril · D. Ibuprofen · E. Spironolactone Answer: D.