Despite increased reliance on sophisticated laboratory studies to assess cardiac risk, evidence increasingly suggests that assessment by physical examination for the presence or absence of heart failure provides significant prognostic information regarding mortality risk. In this regard, the usefulness of the Killip classification has been established in the context of sinus tachycardia (ST)-elevation myocardial infarction, but it is less well studied with non–ST-elevation acute coronary syndromes. Khot and colleagues sought to determine the prognostic importance of the Killip classification in non–ST-segment acute coronary syndromes, as well as its predictive value compared with other variables.
The authors collected information on Killip classification or physical examination equivalents from several large clinical trials. Killip class I patients were those without heart failure; class II patients had mild heart failure with rales involving one third or less of the posterior lung fields and systolic blood pressure of 90 mm Hg or higher. Class III patients had pulmonary edema with rales involving more than one third of the lung fields and systolic blood pressure of 90 mm Hg or higher. Class IV patients were those in cardiogenic shock with any rales and systolic blood pressure less than 90 mm Hg, but because there were few of these patients, class III and class IV patients were combined for the purposes of this study. The primary end points were 30-day and six-month all-cause mortality. Other variables included age, heart rate, systolic blood pressure, body mass index, and creatine kinase MB fraction, as well as sex, ST depression, and multiple medical history variables.
Killip classification was available for 26,090 (98.6 percent) of the pooled study patients. Higher Killip classification was a powerful predictor of all-cause mortality: Killip class II was associated with an increase of more than threefold in 30-day mortality, and Killip class III or IV was associated with an increase of more than fivefold for the same period. The absolute mortality differences between Killip classes increased with time. Although patients with Killip classes II to IV accounted for only 11 percent of the study population, they accounted for 30 percent of deaths at 30 days and at six months.
The authors conclude that Killip classification is a powerful independent predictor of all-cause mortality in patients with non–ST-elevation acute coronary syndromes. Five factors—age, Killip classification, heart rate, systolic blood pressure, and ST-segment depression on electrocardiography—provide more than 70 percent of the prognostic information for 30-day and six-month mortality in these patients. The authors note that physical examination findings continue to play a prominent role in early stratification of patients with acute coronary syndromes, regardless of the availability of sophisticated medical equipment and technical expertise.