We sought to assess the frequency and clinical implications of left ventricular apical ballooning (LVAB) in patients who had been admitted to the medical ICU for noncardiac physical illnesses. Ninety-two consecutive patients who were admitted to the medical ICU from March to May 2003 were prospectively enrolled. Patients underwent echocardiography on the day of ICU admission, and on the third and seventh days in the hospital. LVAB was defined as symmetric severe hypokinesia or akinesia of the left ventricular wall, except for the basal part of the left ventricle, with a < 50% ejection fraction. Of the 92 patients, 65 (71%) were men, and they had a mean (+/- SD) age of 63 +/- 11 years. LVAB was observed in 26 patients (28%), with a mean lowest ejection fraction of 33 +/- 8% (range, 19 to 46%). Compared with the 66 patients (72%) without LVAB, those with LVAB had a higher frequency of sepsis (62% vs 14%, respectively; p < 0.001), a higher prevalence of hypotension on ICU admission, more frequent use of inotropic agents, and a higher frequency of cardiomegaly and pulmonary edema (p < 0.005 for each). Sepsis was the only variable associated with the development of LVAB (odds ratio, 9.2; 95% confidence interval, 2.4 to 35.8; p < 0.001). The development of Q-wave or ST-segment displacement was associated with LVAB, but the sensitivities were 12% and 19%, respectively. Serum creatine kinase level was elevated in 12 of 26 patients (46%) with LVAB. The normalization of this condition occurred in 20 of 26 patients (77%) a mean duration of 7.4 +/- 5.6 days later (range, 2 to 25 days). The mean 2-month survival rate was lower in patients with LVAB than in those without (71 +/- 6% vs 52 +/- 10%, respectively; p = 0.047). LVAB develops in a considerable number of patients who are admitted to the medical ICU, and echocardiography is useful in detecting this phenomenon.