Cardiology
Killip Classification
Heart failure severity in acute MI.
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Background
The Killip classification grades the severity of heart failure in a patient with acute myocardial infarction (MI) based on clinical examination findings. It has four classes: I, no clinical signs of heart failure; II, crackles at the lung bases, a third heart sound or raised jugular venous pressure; III, frank pulmonary oedema; and IV, cardiogenic shock. It was developed in the coronary care unit setting and uses readily observable bedside signs. Higher classes reflect greater haemodynamic compromise.
Interpreting the result
Killip class is strongly prognostic: in-hospital mortality rises markedly from class I through to class IV. Class I carries the lowest risk, classes II and III represent progressively increasing risk from pulmonary congestion and oedema, and class IV (cardiogenic shock) carries the highest mortality and demands urgent escalation. The class helps risk-stratify patients at the bedside and is incorporated into broader risk scores. It should be reassessed as the clinical picture evolves.
Worked example
A patient admitted with an acute MI is found on examination to have bibasal crackles and a raised jugular venous pressure, but is not in florid pulmonary oedema or shock. This places them in Killip class II, indicating mild-to-moderate heart failure and an increased in-hospital mortality compared with class I.
Pearls / pitfalls
- It is a clinical, examination-based score — accuracy depends on careful auscultation and assessment of the jugular venous pressure.
- Class IV (cardiogenic shock) is a medical emergency requiring immediate haemodynamic support and, usually, urgent revascularisation.
- Reassess the class over time; a patient can deteriorate from class I to a higher class during the admission.
- It complements rather than replaces comprehensive risk tools such as GRACE in acute coronary syndromes.
Evidence & validation
Described by Killip and Kimball in 1967 from coronary-care-unit experience, the classification has been repeatedly validated as an independent predictor of mortality in acute MI and is used within contemporary risk tools and guidelines for acute coronary syndromes.
Frequently asked questions
What does a higher Killip class mean?
A higher class indicates more severe heart failure complicating the MI and a higher in-hospital mortality. Class IV, cardiogenic shock, carries the worst prognosis and requires urgent intervention.
Is the Killip class based on tests or examination?
It is based on clinical examination findings — lung crackles, a third heart sound, raised jugular venous pressure, pulmonary oedema and signs of shock. No specific test result is required to assign the class.
When should the Killip class be assessed?
It is assessed at presentation with acute MI and should be reassessed as the patient's condition changes. Deterioration to a higher class signals worsening heart failure and the need to escalate care.
How does Killip class relate to other risk scores?
It is one component of overall risk assessment and features within broader tools such as the GRACE score. It provides a quick bedside estimate of risk but does not replace comprehensive scoring.
References
- Killip T, Kimball JT. Treatment of myocardial infarction in a coronary care unit. A two year experience with 250 patients. Am J Cardiol. 1967;20(4):457–464.
- Collet JP, et al. 2020 ESC Guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation. Eur Heart J. 2021.
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