Utility of impedance cardiography for dyspneic patients in the ED.

Background: Dyspnea is one of the most common emergency department (ED) symptoms, but early diagnosis and treatment are challenging because of multiple potential causes. Hemodynamic parameters may aid in the evaluation of dyspnea, but are difficult to assess. Impedance cardiography is a noninvasive hemodynamic measurement method that may assist in early ED decision making.

Methods: This study is intended to determine the accuracy in differentiating cardiac from noncardiac causes of dyspnea using impedance cardiography-derived hemodynamic parameters compared to ED physician opinion in light of initial history, and physical and laboratory tests. The final diagnosis, made after patient hospital record review, was compared with ED physician and impedance cardiography diagnoses.

Results: A total of 52 patients were included: 14 women and 38 men, aged 68.5 +/- 14.2 years. There were significant differences in values of stroke index (25.7 vs 32.9, P < .05), cardiac index (2.3 vs 3.1, P < .0001), velocity index (35.1 vs 53.2, P < .01), and systolic time ratio (0.55 vs 0.44, P < .05) between the cardiac and noncardiac groups, respectively. Impedance cardiography measurements demonstrated better sensitivity (75% vs 60%), specificity (88% vs 66%), and positive and negative predictive values (79% vs 52% and 85% vs 72%, respectively) compared with those of the ED physician in distinguishing cardiac from noncardiac causes of dyspnea.

Conclusion: Impedance cardiography data result in improvement in ED physician differentiation of cardiac from noncardiac causes of dyspnea.