A typical electrocardiograph is constructed from 12 leads, created from pairs of

Question

A typical electrocardiograph is constructed from 12 leads, created from pairs of surface electrodes placed on the skin surface. The QRS cycle represents depolarization of the right and left ventricles during heart contractions. 1. Assume that ECG electrodes are placed on the right arm (RA), left arm (LA), and left leg (LL), are all 60 cm from the heart, and the body tissue resistivity is =0.8 Ohms*m. Assume the electrodes sensing surfaces have an area of 1 cm2. What is the resistance of body tissue between the heart and each electrode? Assume the heart creates a voltage of 120 mV over one QRS cycle. What is the current passing through the body, from heart to electrodes? a. b. c. Three leads are ,, and IIl, created by LA-RA, LL-RA, and LL-LA voltages, respectively. At which angles are these leads oriented? Sketch a diagram of the leads. Sketch a 4- chambered heart in the middle of the electrodes, and label the left and right atria, left and right ventricles, and the septum. Match the leads to the regions of the heart each lead is most sensitive to, electrically. Review the pdf with the diagram about the ECG. Define what is happening in the heart during the Q, R, and S phases of the ECG cycle. How much electrical power do the ventricles release in one QRS cycle? Estimate. You will need to construct a circuit from the ventrical walls and septa, assume a resistivity, and calculate resistance by estimating heart wall cross-sectional area and length of the ventricle perimeter. What are three problems with ECG recordings (error factors)? d. e. f. g.

Explanation / Answer

a,R=p*L/A

where p is resistivity,L is length and A is area of contact

converting all the given values into S.I units we have A=0.00001sq.m

L=0.6m and p=0.8 ohm.m

by substituting values in the given formula,we have

R=0.8*0.6/0.00001

. =4800 ohm

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.