Cardiac output (CO) responses to acute changes in body position and Valsalva maneuver (VM) were proposed to assess cardiac contractile reserve. We investigated the value of sitting position (SP), leg raising (LR), and VM for identifying heart failure (HF) in patients with undifferentiated dyspnea.
It is a prospective study including patients over 18 years old admitted to the emergency department (ED) for dyspnea. Bioimpedance CO was measured at baseline, under SP, LR, and VM. HF diagnosis was based on clinical assessment, serum levels of brain natriuretic peptide (BNP) and echocardiography findings. Study population was divided into patients with heart failure (HF group) and patients without HF (non-HF group). Diagnostic performance of CO change under the three maneuvers was calculated by sensitivity, specificity, likelihood ratio and receiver operating characteristic (ROC) curve.
290 patients were enrolled in the study. The final diagnosis was dyspnea due to congestive heart failure in 147 patients (50.7%). CO change with VM was the most accurate exam in identifying congestive heart failure as the cause of dyspnea with a sensitivity, specificity, positive and negative likelihood ratios of 79%, 60%, 1.97, and 0.36 respectively. Area under ROC curve was 0.62(95% CI, 0.55-0.69), 0.63(95% CI, 0.56-0.69), and 0.70(95% CI, 0.64-0.76) respectively for SP, LR, and VM. In a multivariate analysis, CO change with VM, but not with SP or LR, carried independent diagnostic value (p < 0.001).
the diagnosis of HF can be aided with use of analyzing the effect of VM on non-invasively measured CO among patients admitted to the ED with undifferentiated dyspnea. Diagnostic yield of SP and LR was poor.

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