ECG Flashcards
What is an ECG?
→ Graphic representation of electrical potential difference changes against time of the myocardium throughout the cardiac cycle
What needs to happen to the P.D for the cardiac cell to contract?
→ The p.d across the cellular membrane must change from negative to positive
How do changes in potential difference occur ?
→ They occur through the flow of ions through specialized ion channels
→ Flow freely through gap junctions
What is a dipole in relation to cardiac cells?
→ During depolarization and repolarization
→ Different currents flowing across the cell membrane at various points
→ a potential difference is created between one part of the cell and another
When is there no electrical field in the heart?
→ when cell is depolarized or repolarized
→ cell is resting potential
What is set up around the dipole?
→ an electrical field
What is the sinus rhythm?
→ Initiated by SAN → Traverses atria → Through the AV node → Rapid conduction through Purkinje → ventricular myocardium
What is the P wave?
→ both atrial depolarization
→120-200ms
What is the PR segment?
→ The AV node delay
What is the QRS complex?
→ The depolarization of both ventricles
→ typical range 80-110 ms
What is the QT interval?
→ ventricular depolarization and repolarization
→ 350-420 ms
what is long QT syndrome?
→ Sudden death
What is the ST segment?
→ isoelectric segment between the end of QRS and the start of T wave
What is a depression of the ST segment indicative of?
→ Ischaemia
What is an elevation of the ST segment indicative of?
→ Myocardial infarction
