Introduction: According to Starling's law, low serum colloid osmotic pressure related to hypoproteinaemia is likely to modulate the pulmonary capillary hydrostatic pressure threshold of pulmonary oedema formation. We therefore examined the clinical relevance of bedside tissue Doppler echocardiography in the emergency diagnosis of new-onset heart failure with normal ejection fraction (HFnlEF) according to serum protein concentration.
Methods: A total of 105 consecutive elderly patients presenting with acute severe dyspnoea were prospectively enrolled. B-type natriuretic peptide (BNP) concentration and spectral tissue Doppler-derived septal E/E' ratio were obtained at presentation. Serum protein concentration was measured immediately after clinical stabilization, with a value of less than 6g/dL defining hypoproteinaemia.
Results: The diagnostic performance of E/E' was excellent in normoproteinaemic patients (n=71; area under the receiver-operating characteristic [ROC] curve 0.97; p<0.001) and reasonable in hypoproteinaemic patients (n=34; area under ROC curve 0.83; p<0.001). By multivariable logistic regression analysis, E/E' provided independent and incremental diagnostic information over the Boston score and BNP concentration in patients with a normal serum protein concentration (p<0.01). Critical elevation of pulmonary capillary pressure, defined as E/E'>15, was present in 93% of patients with HFnlEF and normoproteinaemia versus 55% of patients with HFnlEF and hypoproteinaemia (p=0.0017).
Conclusion: Septal E/E'>15 is clinically relevant for the emergency diagnosis of new-onset HFnlEF among elderly patients with normal serum protein concentration. Lower abnormal values less than 15 should be considered predictive of this condition in the setting of hypoproteinaemia.