Killip Classification: Stratifies risk of in-hospital mortality in patients with acute myocardial infarction based on clinical signs of heart failure.
Guidelines & Evidence
Clinical Details
Section 1
When to Use
When to Use
Routinely in the initial assessment of patients presenting with acute myocardial infarction (AMI)
To rapidly stratify risk of 30-day and in-hospital mortality based purely on bedside clinical signs
To guide intensity of care (e.g., CCU admission vs. step-down unit)
Populations
Originally validated in the pre-reperfusion era (1967), but repeatedly validated in the modern era of primary PCI and potent antithrombotic therapy. Even though overall mortality rates have fallen, the predictive gradient across the four classes remains robust.
Section 2
Formula & Logic
Classification Logic
01
Class I: Individuals with no clinical signs of heart failure. Typical mortality 6% (historical), now 2-3% in modern PCI eras.
02
Class II: Individuals with rales or crackles in the lungs, an S3 gallop, and elevated jugular venous pressure. Lung findings limited to the lower half of the lung fields. Typical mortality 17% (historical), now ~5-8%.
03
Class III: Individuals with frank acute pulmonary edema. Typical mortality 38% (historical), now ~10-15%.
04
Class IV: Individuals in cardiogenic shock or hypotension (systolic blood pressure < 90 mmHg), and evidence of peripheral vasoconstriction (oliguria, cyanosis or diaphoresis). Typical mortality 81% (historical), but remains extremely high today even with advanced MCS/ECMO (~40-50%).
Section 3
Pearls/Pitfalls
Subjectivity and Interobserver Reliability
The Killip classification is highly dependent on bedside physical examination skills, which have poor-to-moderate interobserver reliability among modern clinicians, especially for Class II vs Class III distinction. An S3 gallop can be difficult to auscultate in a noisy ED or CCU environment.
Integration with other scores
Because of its strong predictive power, the Killip class is incorporated directly into the GRACE score. A patient in Killip Class IV automatically receives a massive bump in their 6-month expected mortality in the GRACE model.
Section 4
Evidence Appraisal
Original Publication
Treatment of myocardial infarction in a coronary care unit. A two year experience with 250 patients.
Killip T 3rd et al. • Am J Cardiol.. 1967;20(4):457-64. The landmark paper establishing the classification system.
Modern Validation
Predictive value of the Killip classification in patients undergoing primary percutaneous coronary intervention for acute myocardial infarction.
DeGeare VS et al. • Am J Cardiol.. 2001;87(9):1035-8. Confirmed that Killip classification remains a powerful independent predictor of mortality in the primary PCI era.
