Unit 4 - Electrocardiogram Flashcards
What is this?
a P-QRS-T complex
What is occuring at the p wave?
atrial depolarization
What occurs during the P-Q interval?
atrioventricular conduction - travels through the AV node
What occurs in the QRS complex?
ventricular depolarization
What occurs during the S-T interval?
the end of ventricular depolarization and the beginning of repolarization
What is occuring at the t-wave?
ventricular repolarization - it can be positive or negative
What is a lead axis?
the connection of two parts of the body by electrodes and wires with the ECG
What are the clinically useful leads?
I, II, III, aVR, aVL, aVF
What is the MEA?
the average of all instantaneous mean electrical vectors occurring sequentially during depolarization of the ventricles
Why is MEA clinically useful?
Estimation is clinically useful because deviations from it can mean that there is an abnormality somewhere in the heart, and the lead showing the abnormality can tell us exactly what is going on
What is a heart rate?
the number of beats or complexes per minute
How do you estimate the MEA?
Choose lead with most isoelectric QRS and Find lead perpendicular to this
OR
Choose lead with tallest R wave MEA points to positive pole of this lead
Why does the sinus node control the heart’s rhythm?
Because it is the first one to depolarize. The AV node is not as fast and gets ‘washed over by a wave’ so it has to start over and try and depolarize again
How would you describe a normal sinus rhythm?
every P has a QRS and every QRS has a P
How would you describe a supraventricular rhythm?
there is a funky p wave; it is positive with a different shape, it has a negative deflection, or it doesnt exist
How would you describe a ventricular rhythm?
wide and bizarre, depolarization is occuring much more slowly
How would you describe a premature sinus wave?
it comes in earlier than the other normal sinus rhythms; sometimes the p wave is absent
How would you describe a late rhythm?
it is known as an escape rhythm and there is an abnormal amount of space between the t wave and the proceeding p wave
How would you describe 1 degree AV block?
a prolonged P-Q interval
How would you describe a 2nd degree AV block?
some normal sinus complexes and then some unconducted p wave
How would you describe a 3rd degree AV block?
There is no electrical activity that passes all of the way through; the p waves are alone, the QRS complexes are alone
What are the ECG characteristics of artial fibrilation?
fast heart rate, irregular rhythm, normal QRS complex, no p-waves, sometimes there are little 1/2 p waves
What are the consequences of atrial fibrillation?
poor cardiac output, fast heart rate - less time to fill ventricles, can lead to blood clots
What would a venrtricular fibrillation ECG look like?
normal sinus rhythms, then ventricular premature rhythms, then ventricular tacchycardia; there is no meaningful contraction
