Estimation of left ventricular systolic function by single transpulmonary thermodilution

Objective. The single-indicator transpulmonary thermodilution technique (PiCCO system) provides two derived indices of cardiac systolic function: the cardiac function index and the global ejection fraction. We used transesophageal echocardiography to compare theses indices with left ventricular fractional area of change only for patients with no isolated right ventricular dysfunction. (The global cardiac systolic function may be decreased despite preserved left ventricular function in this situation.) Design. Prospective, open, clinical study. Setting. Intensive care unit (ICU) in a university hospital. Patients. Thirty-three mechanically ventilated patients. Intervention. Left ventricular fractional area of change (LVFAC) was measured using transesophageal echocardiography. The cardiac function index (CFI) and the global ejection fraction (GEF) were determined from transpulmonary thermodilution-derived cardiac output and thoracic volumes. Measurements and main results. Transesophageal echocardiography identified 3 patients with isolated right ventricular failure (PiCCO underestimated LVFAC in this situation). Significant correlations were established between LVFAC and CFI (r=0.87, n=30, p<0.0001) or GEF (r=0.82, n=30, p<0.0001). The mean differences between measured LVFAC and LVFAC estimated with CFI or GEF were 0.8+/-8.5% (range: -17 to 14%) and 0.8+/-9.0% (range: -21 to 19%), respectively. Area under the receiver operating characteristics curves for the estimation of LVFAC greater than or equal to40% using CFI or GEF was 0.92. CFI >4 and GEF >18% estimated LVFAC greater than or equal to40% with respective sensitivities of 86 and 88% and specificities of 88 and 79%. Significant correlations were established between changes of LVFAC and CFI/GEF over time. Conclusions. In mechanically ventilated ICU patients, PiCCO-derived cardiac function index and global ejection fraction provide reliable estimations of LV systolic function but may underestimate it in the cases of isolated right ventricular failure.