A new algorithm for improved detection of aortic valve opening by impedance cardiography

Impedance cardiography (ICG) is a cost-effective, noninvasive technology which is useful for measuring systolic time intervals on the basis of bioimpedance changes in the thorax to applied electrical alternating current. In clinical use, variations in the ICG signal cause ambiguity in the detection of aortic valve opening. Because of the importance of accurate identification of the onset of left ventricular ejection, this ambiguity represents the most significant impediment to reliable ICG analysis of systolic time intervals. In 26 patients, timing of aortic valve opening was simultaneously measured by a new ICG technique and aortic Doppler. The data shows a high correlation (r=0.996) between ICG and Doppler values.