Inferior vena cava assessment in the bedside diagnosis of acute heart failure

Objectives: The objective of this study was to determine the test characteristics of the caval index and caval-aortic ratio in predicting the diagnosis of acute heart failure in patients with undifferentiated dyspnea in the emergency department (ED). Methods: This prospective observational study was performed at an urban ED that enrolled patients, 50 years or older, with acute dyspnea. A sonographic caval index was calculated as the percentage decrease in the inferior vena cava (IVC) diameter during respiration. A caval-aortic ratio was defined by the maximum IVC diameter divided by the aortic diameter. The sensitivity, specificity, and likelihood ratios of these measurements associated with heart failure were estimated. Results: Eighty-nine patients were enrolled in the study with a mean age of 68 years. A caval index of less than 33% had 80% sensitivity (95% confidence interval [CI], 63%-91%) and 81% specificity (95% CI, 68%-90%) in diagnosing acute heart failure, whereas an index of less than 15% had a 37% sensitivity (95% CI, 22%-55%) and 96% specificity (95% CI, 86%-99%). The sensitivity of a caval-aortic ratio of more than 1.2 was 33% (95% CI, 18%-52%) and the specificity was 96% (95% CI, 86%-99%). Positive likelihood ratios were 10 for a caval index of less than 15%, 4.3 for an index of less than 33%, and 8.3 for a caval-aortic ratio of more than 1.2. Conclusion: Bedside assessments of the caval index or caval-aortic ratio may be useful clinical adjuncts in establishing the diagnosis of acute heart failure in patients with undifferentiated dyspnea.