Physiology ? about ECG waves

[mistiffy]

I have a question about the waves on an ECG tracing. We covered the different ECG waves in Physiology and one of the questions on the test was, during what time does the ventricle contract? Our answers were: prior to the p wave, following the QRS complex, or immediately before the T wave. To me, and I could be totally wrong here, immediately before the T wave and following the QRS complex are the same thing! Needless to say, I put following the QRS complex because this represents ventricular depolarization where the ventricle contracts. I got the question wrong, the correct answer was immediately before the T wave. So I am confused right now as to what the difference is between what happens after the QRS complex and immediately before the T wave, because it sounds the same to me. If someone could put this into layman's terms for me, I would really appreciate it! Thanks!

[EricJRN, MSN, RN]

Picky question! Ventricular contraction actually starts about midway through the QRS, but no blood is really pumped until the ST segment, which is the segment just prior to the T wave. The ST doesnt techncally follow the QRS because there is a small upward deflection after the S (but before the ST) that gets the tracing back to baseline.

This link offers a diagram:

http://sprojects.mmi.mcgill.ca/cardiophysio/EKGQRScomplex.htm

You could argue that the question wasn't clear or accurate.

[EricJRN, MSN, RN]

Actually, in regard to the S wave, never mind. That last upward deflection is part of the S. I'm not sure what to make of the rationale now.

[mistiffy]

Thank you for your reply! I, along with several other students, argued this question and how misleading it is, the instructor really wouldn't hear it. Oh, well I guess, I was just curious as to what the rationale was behind this question because my instructor doesn't want to explain it, but thinks that it was a very easy question and that we all should have got that right. Thanks again.

[fiveofpeep]

I have a question about the waves on an ECG tracing. We covered the different ECG waves in Physiology and one of the questions on the test was, during what time does the ventricle contract? Our answers were: prior to the p wave, following the QRS complex, or immediately before the T wave. To me, and I could be totally wrong here, immediately before the T wave and following the QRS complex are the same thing! Needless to say, I put following the QRS complex because this represents ventricular depolarization where the ventricle contracts. I got the question wrong, the correct answer was immediately before the T wave. So I am confused right now as to what the difference is between what happens after the QRS complex and immediately before the T wave, because it sounds the same to me. If someone could put this into layman's terms for me, I would really appreciate it! Thanks!

Yeck My test for the EKG, etc is on tuesday and I know if I ever saw a question like that I would freak out! I wonder if the teacher told you specifically in class which one he/she would choose. Such a question seems grossly unfair.

For us, ST seg = ventricular systole/contraction