Integrated Concepts (a) Referring to Figure 20.34, find the time systolic pressure lags behind the middle of the QRS complex. (b) Discuss the reasons for the time lag.
a.) The time lag between systolic pressure and middle of the QRS complex is 0.25 s
b.) The QRS complex is the result of the depolarization of the ventricles, which causes it to contract. The pressure decreases at this time which leads to diastolic pressure. The heart is polarized after this contraction which raises the pressure to its maximum value making the heart ready for the next beat. The fact that the maximum pressure is approximately 1/3 of a heart cycle after the QRS complex says that during 2/3 of the cycle the heart is doing work, during the last 1/3 it is resetting to start again.