CVS Physio Pt 2/2 (ECG n PE) Flashcards
What does ECG measure?
(Using your hand actions) Show the “views” of Leads I, II, III and Leads aVR, aVL and aVF.
Where are the 10 electrodes in 12-lead ECG placed?
(i) Draw out the ECG 12 boxes strip.
(ii) Which ECG box corr to which leads? (draw the pattern on a pic of the ECG).
(iii) Which leads (thus which boxes) then corr to (eg. probs w) which coronary arteries?
1 small box = ?s
1 big box (aka 5 small boxes) = ?s on ECG ppr
Outline the cardiac cycle. (draw ‘pie chart’)
Note: the ELECTRICAL ACTIVITY during each cardiac cycle is represented as a graph on ECG ppr
What does ‘ups’ - positive deflections and ‘downs’ - negative deflections mean in ECG ppr?
Interpret what these mean:
(i) P wave
(ii) QRS complex
(iii) T wave
(iv) PR interval
(v) ST segment (“from end of S to start of T”)
(vi) QT interval (“from start of Q to end of T”)
(vii) RR interval
HINT: RMB THE WAVES, WTV YOU SEE ON ECG = ELECTRICAL ACTIVITY –> you can outline the direction location of the conduction system of heart (specialised muscle fibres transmitting these impulses)
Does depolarisation or repolarisation give rise to systole?
depol –> systole
Does depolarisation or repolarisation give rise to diastole?
repol –> diastole
What’s the formula for using RR interval to calculate HR?
300/(no. of big sq btw RR)
normal HR of 75bpm = ? big squares on ECG ppr
4
Bradycardia = ? bpm = >? big squares on ECG ppr
Tachycardia= ? bpm = <? big squares on ECG ppr
Interpret what these mean:
1. missing P wave
2. prolonged PR interval
3. prolonged QRS interval
4. Tall QRS complex
5. prolonged QT interval (“from start of Q to end of T”)
6. Tall T wave
7. ST segment elevation (“from end of S to start of T”)
8. ST segment depression (“from end of S to start of T”)
9. Prolonged RR interval
IMPNOTE: rmb all these CG waves are the CONDUCTION SIGNALS in conduction syste of heart, not much of what muscular movement is happening - change perspective
Note: why does hyperkalemia cause tall t waves if repolarisation involves the efflux of K+ from cell into an extracellular environment (with increased K+ concentration)?
Ans: During repolarization, K⁺ ions leave the cell through K⁺ channels. In hyperkalemia, the high extracellular K⁺ concentration decreases the driving force for K⁺ to leave the cell, but the increased extracellular K⁺ also enhances K⁺ conductance (opening of more K⁺ channels). This can lead to a quicker repolarization phase.
The quicker repolarization results in the T wave on the ECG being sharper and more peaked, as the cells return to their resting state more rapidly and uniformly.
