ECG Dr. Amal Al Maqadma Teaching assistant IUG
MI When myocardial blood supply is abruptly reduced to a region of the heart, a sequence of injurious events occur : • Ischemia ( subendocardial or transmural) • Injury • Necrosis, and eventual fibrosis (scarring) if the blood supply isn't restored in an appropriate period of time
Precordial Septal Leads • V1 – V2 – Look at the Septum of the heart – The septal branch of the LAD
Precordial Anterior Leads • V3 – V4 –anterior wall of the left ventricle –The LAD diagonal branch)
Lateral Precordial Leads • I,AVL,V5 – V6 • lateral of the left ventricle • The left circumflex
Inferior border leads • II, III and aVF • the Inferior wall of the RV • Posterior Descending Branch of the RCA.
Posterior MI • No leads look at the posterior wall. • usually associated with inferior and/or lateral wall MI. • The changes of posterior myocardial infarction are seen indirectly in the anterior precordial leads. Leads V1 to V3 face the endocardial surface of the posterior wall of the left ventricle. As these leads record from the opposite side of the heart instead of directly over the infarct, the changes of posterior infarction are reversed in these leads. The R waves increase in size, becoming broader and dominant, and are associated with ST depression and upright T waves. This contrasts with the Q waves, ST segment elevation, and T wave inversion seen in acute anterior myocardial infarction. • ST depression is considered reciprocal ECG changes in what should be ST elevation for acute posterior wall injury.
Principles of ECG recording • Explain the indication and the procedure for the patient. (assurance ) • Ask the patient to take off any metals he/she wears. • Expose the wanted sites. • Cleaning of skin and shaving if necessary. • Place the electrodes in the correct positions . • Instruct the patient to remain still (should not talk during the test ) and relax their shoulders and legs while the recording takes place (1 min)
How to comment on ECG • Name.Age ,Date and time. • Calibration and Speed of paper • RAWIHI :
RAWIHI • R: rate, regularity,rhythm(sinus or asinus), • A: axis. • W:waves. • I :intervals. • H: hypertrophy. • I: ischemia
Normal Sinus Rhythm • Rate = 60-100 beat / minute. • The rhythm is regular • All intervals are within normal limits • There is a P for every QRS and a QRS for every P. • P : QRS ratio = 1 : 1. • The P waves all look the same • Presence of P, QRS, T in each cycle. • Normal shape, time of waves, segments and intervals
Interfering factors • Inaccurate placement of the electrodes • Electrolyte imbalances • Poor contact between the skin and the electrodes • Movement or muscle twitching during the test • Drugs that can affect results include digitalis, quinidine, and barbiturates