Electrocardiac signal is one of the most important signals which is used to trigger ventricular assist device (VAD), and the delay time of VAD assistance is very important to get a satisfied result. Proper delay will give VAD relatively enough time to assist, avoiding left heart failure caused by the collision of the heart and VAD during systolic phase. This becomes much more important when the left atrium drainage is insufficient. The aim of our study is to set up an equation to calculate the delay time by RR interval. We try to set up an equation about RR and R-Ao like: R-Ao = A x (RR)n + B(A and B are constant). RR represents the RR interval and R-Ao represents the duration of the period between the peak point of QRS and the point of aortic valve closing; First, calculate RR according to weighting average method, and then, calculate the anticipant R-Ao according to the before-mentioned equation. After adjustment, R-Ao will be used as assistance delay time. R-R interval was measured in 457 selected pediatric patients who were undergiong left heart catheterization and who did not have arrhythmias. From the ECG recording during catheterization, R-R interval was measured while R-Ao was obtained from aortic pressure wave chart; Plot graphs with R-Ao as dependent variable and (RR)n as independent variable; find out correlating model and calculate the arguments A and B of R-Ao = A x (RR)n + B. The results showed that the relation between (RR)1/3 and R-Ao is the most significant, the relation coefficient is 0.733, the regress coefficient is -0.182 (P < 0.001) and the interception is 1.070. This means that R-Ao = (-0.182) (RR) 1/3 + 1.070. The likelyhood degrees of different sections differ markedly. When heart rate is less than 120 beats per min. The relation argument is about 0.733 while 0.45 when heart rate is more than 120 beats per min, Therefore, we can use the equation R-Ao = (-0.182) (RR)1/3 + 1.070 to calculate R-Ao when heart rate is less than 120 beats per min.
Adolescent ; Algorithms ; Child ; Child, Preschool ; Counterpulsation ; methods ; Electrocardiography ; Heart ; physiology ; Heart-Assist Devices ; Humans ; Signal Processing, Computer-Assisted