The Killip classification is a system used in individuals with an acute myocardial infarction (heart attack), in order to risk stratify them. Individuals with a low Killip class are less likely to die within the first 30 days after their myocardial infarction than individuals with a high Killip class.

The study

The study was a case series

Case series

A case series is a medical research descriptive study that tracks patients with a known exposure given similar treatment or examines their medical records for exposure and outcome. It can be retrospective or prospective and usually involves a smaller number of patients than more powerful...

 with unblinded, unobjective outcomes, not adjusted for confounding factors, nor validated in an independent set of patients. The setting was the coronary care unit

Coronary care unit

A coronary care unit is a hospital ward specialized in the care of patients with heart attacks, unstable angina, Cardiac dysrhythmia and various other cardiac conditions that require continuous monitoring and treatment.-Characteristics:...

 of a university hospital in the USA.

250 patients were included in the study (aged 28 to 94; mean 64, 72% male) with a myocardial infarction. Patients with a cardiac arrest

Cardiac arrest

Cardiac arrest, is the cessation of normal circulation of the blood due to failure of the heart to contract effectively...

 prior to admission were excluded.

Patients were ranked by Killip class in the following way:

• Killip class I includes individuals with no clinical signs of heart failure
  Congestive heart failure
  Heart failure often called congestive heart failure is generally defined as the inability of the heart to supply sufficient blood flow to meet the needs of the body. Heart failure can cause a number of symptoms including shortness of breath, leg swelling, and exercise intolerance. The condition...
  
  .
• Killip class II includes individuals with rales or crackles in the lung
  Lung
  The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...
  
  s, an S_{3, and elevated jugular venous pressure.}
• Killip class III describes individuals with frank acute pulmonary edema.
• Killip class IV describes individuals in cardiogenic shock
  Cardiogenic shock
  Cardiogenic shock is based upon an inadequate circulation of blood due to primary failure of the ventricles of the heart to function effectively....
  
   or hypotension
  Hypotension
  In physiology and medicine, hypotension is abnormally low blood pressure, especially in the arteries of the systemic circulation. It is best understood as a physiologic state, rather than a disease. It is often associated with shock, though not necessarily indicative of it. Hypotension is the...
  
   (measured as systolic blood pressure lower than 90 mmHg), and evidence of peripheral vasoconstriction
  Vasoconstriction
  Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, particularly the large arteries, small arterioles and veins. The process is the opposite of vasodilation, the widening of blood vessels. The process is particularly important in...
  
   (oliguria
  Oliguria
  Oliguria is the low output of urine, It is clinically classified as an output below 300-500ml/day. The decreased output of urine may be a sign of dehydration, renal failure, hypovolemic shock, HHNS Hyperosmolar Hyperglycemic Nonketotic Syndrome, multiple organ dysfunction syndrome, urinary...
  
  , cyanosis
  Cyanosis
  Cyanosis is the appearance of a blue or purple coloration of the skin or mucous membranes due to the tissues near the skin surface being low on oxygen. The onset of cyanosis is 2.5 g/dL of deoxyhemoglobin. The bluish color is more readily apparent in those with high hemoglobin counts than it is...
  
   or sweating).

Conclusions

The numbers below were accurate in 1967. Nowadays, they have diminished by 30 to 50% in every class.

Within a 95% confidence interval

Confidence interval

In statistics, a confidence interval is a particular kind of interval estimate of a population parameter and is used to indicate the reliability of an estimate. It is an observed interval , in principle different from sample to sample, that frequently includes the parameter of interest, if the...

 the patient outcome was as follows:

Killip class I:	81/250 patients;	32% (27–38%).	Mortality rate was found to be at 6%.
Killip class II:	96/250 patients;	38% (32–44%).	Mortality rate was found to be at 17%.
Killip class III:	26/250 patients;	10% (6.6–14%).	Mortality rate was found to be at 38%.
Killip class IV:	47/250 patients;	19% (14–24%).	Mortality rate 67%

The Killip-Kimball classification has played a fundamental role in classic cardiology, having been used as a stratifying criteria for many other studies. Worsening Killip class has been found to be independently associated with increasing mortality in several studies.

Killip class 1 and no evidence of hypotension or bradycardia

Bradycardia

Bradycardia , in the context of adult medicine, is the resting heart rate of under 60 beats per minute, though it is seldom symptomatic until the rate drops below 50 beat/min. It may cause cardiac arrest in some patients, because those with bradycardia may not be pumping enough oxygen to their heart...

, in patients presenting with acute coronary syndrome

Acute coronary syndrome

Acute coronary syndrome is usually one of three diseases involving the coronary arteries: ST elevation myocardial infarction , non ST elevation myocardial infarction , or unstable angina ....

, should be considered for immediate IV beta blockade

Beta blocker

Beta blockers or beta-adrenergic blocking agents, beta-adrenergic antagonists, beta-adrenoreceptor antagonists or beta antagonists, are a class of drugs used for various indications. They are particularly for the management of cardiac arrhythmias, cardioprotection after myocardial infarction ,...

.