What is the Killip classification?

Killip Classification System

The Killip classification is a clinical tool that provides an estimate of the severity of myocardial derangement in patients with acute myocardial infarction (AMI) based on physical examination findings and chest X-ray results. 1

The Four Stages of Killip Classification

The classification consists of four stages that stratify patients according to the severity of heart failure following AMI:

• Stage I: No heart failure. No clinical signs of cardiac decompensation.
• Stage II: Heart failure. Diagnostic criteria include rales, S3 gallop, and pulmonary venous hypertension. Pulmonary congestion with wet rales in the lower half of the lung fields.
• Stage III: Severe heart failure. Frank pulmonary edema with rales throughout the lung fields.
• Stage IV: Cardiogenic shock. Signs include hypotension (SBP < 90 mmHg) and evidence of peripheral vasoconstriction such as oliguria, cyanosis, and diaphoresis (sweating). 1

Clinical Significance and Prognostic Value

The Killip classification has substantial prognostic implications:

• It strongly predicts both short-term and long-term mortality after AMI 2

• Mortality rates increase significantly with higher Killip class:

  • Class I: Approximately 2-10% in-hospital mortality
  • Class II: 10-20% in-hospital mortality
  • Class III: Up to 90% in-hospital mortality
  • Class IV: 36-100% in-hospital mortality 3, 4

• The classification provides more than 70% of the prognostic information when combined with four other factors: age, heart rate, systolic blood pressure, and ST depression 5

Clinical Application

The Killip classification should be determined immediately upon presentation in all patients with suspected AMI to:

1. Guide initial treatment decisions
2. Determine the level of monitoring required
3. Identify patients who may need more aggressive interventions

Management Considerations by Class

• Class I: Standard AMI management
• Class II: Additional heart failure treatment with diuretics and careful monitoring
• Class III: Requires aggressive treatment of pulmonary edema, including oxygen therapy and possibly non-invasive or invasive ventilation
• Class IV: Immediate interventions for cardiogenic shock, including consideration of mechanical circulatory support and urgent revascularization 1

Important Clinical Pearls

1. While originally developed for ST-elevation MI, the Killip classification has proven valuable in non-ST-elevation acute coronary syndromes as well 5

2. The classification retains its prognostic value even in the era of primary reperfusion therapy 4

3. Patients in higher Killip classes (especially III and IV) represent a small percentage of AMI patients (approximately 9-15%) but account for a disproportionately high percentage of deaths (around 30%) 5

4. The classification has recently been validated in myocardial infarction with non-obstructive coronary arteries (MINOCA), where higher Killip class still predicts worse outcomes 6

5. Early primary angioplasty has contributed to decreased mortality in Killip IV patients, though appropriate medical therapy remains critically important 4

The Killip classification remains a simple yet powerful bedside tool that helps clinicians rapidly assess risk and guide management decisions in patients with acute myocardial infarction.