Comparing impedance cardiography and echocardiography in the assessment of reduced left ventricular systolic function

BACKGROUND: An early and accurate diagnosis of chronic heart failure is a big challenge for a general practitioner. Assessment of left ventricular function is essential for the diagnosis of heart failure and the prognosis. A gold standard for identifying left ventricular function is echocardiography. Echocardiography requires input from specialized care and has a limited access in Swedish primary health care. Impedance cardiography (ICG) is a noninvasive and low-cost method of examination. The survey technique is simple and ICG measurement can be performed by a general practitioner. ICG has been suggested for assessment of left ventricular function in patients with heart failure. We aimed to study the association between hemodynamic parameters measured by ICG and the value of ejection fraction as a determinant of reduced left ventricular systolic function in echocardiography. METHODS: A non-interventional, observational study conducted in the outpatients heart failure unit. Thirty-six patients with the diagnosis of chronic heart failure were simultaneously examined by echocardiography and ICG. Distribution of categorical variables was presented as numbers. Distribution of continuous variables was presented as a mean and 95% Confidence Interval. Kruskal-Wallis test was used to compare variables and show differences between the groups. A p-value of <0.05 was considered significant. RESULTS: We found that three ICG parameters: pre-ejection fraction, left ventricular ejection time and systolic time ratio were significantly associated with ejection fraction measured by echocardiography. CONCLUSIONS: The association which we found between EF and ICG parameters was not reported in previous studies. We found no association between EF and ICG parameters which were suggested previously as the determinants of reduced left ventricular systolic function. The knowledge concerning explanation of hemodynamic parameters measured by ICG that is available nowadays is not sufficient to adopt the method in practice and use it to describe left ventricular systolic dysfunction.