Wednesday, 18 January 2012

ECG's and other deviant behaviour (part 1)

After an awesome and enlightening tutorial on ECG's from my new consultant, I thought I'd share some of the tips I wrote down. I appreciate a lot of people find ECG's old hat and this will not be high level stuff, but I've struggled with interpreting them for ages and found most lecturers to be lacking when it came to the slightly more complicated stuff (read: axis deviation). Anyway, this is the first part of my notes. Hope you find them useful.

As always comment on patient name, age, date that the ECG was taken (mention if chest pain was noted when ECG was taken).

  • Check the paper speed! (hopefully it will be 25mm/ sec)
  • Count the number of big squares between R waves and divide 300 by the number of squares
  • Regular? If not approximate rate by counting 30 big squares and count number of R waves then times by 10 to get the bpm
  • Sinus rhythm describes a QRS complex preceded by a normal P wave (Lead II is best for visualising P-waves, hence its use as rhythm strip

Cardiac deviation
  • To determine whether or not the heart is deviated to the left or the right look at leads I, II and III. Determine which leads are positive and which are negative; to do this compare the peak and trough around the isoelectric line and sum them. A positive lead has a higher peak than trough and a negative lead has a lower trough than peak.
    • If I and II are both positive, the heart is normally aligned
    • If I is positive and II is negative, the heart is left deviated
    • If III is positive and I and II are negative, the heart is right deviated
  • Further to this, when looking at I, II and III determine which is closest to isoelectric (the peak = the trough). The heart is at 90 degrees to that lead - though check that aVR is negative to confirm correct lead placement.
  • Are there P waves preceding every QRS complex? If not you may be looking at Atrial Fibrillation.
  • If there is a P wave, what kind of shape is it? If it M-shaped, it might well be P-mitrale. This is commonly seen in mitral valve disease, particularly mitral stenosis or a dilated/ hypertrophic left atrium. A tall, peaked P wave is indicative of P-pulmonale or right-atrium dilation/ hypertrophy caused by conditions such as COPD.
To be continued!

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