ECG part 2 Flashcards
Describe wolf parkinson white syndrome
Where there is an accessory electrical pathway connecting the atria to the ventricles meaning that current can be conducted without being slowed by the AV node.
Describe three abnormalities found on ECG with WPW and their causes.
Decreased PR interval and slurred upstroke in QRS complex
The accessory pathway in WPW is faster than the AV node pathway and so some of the ventricle depolarises early, resulting in a short PR interval and a slurred upstroke to the QRS complex.
Re-entrant supraventricular tachycardia. Longer P wave and decreased RR interval . Current re-enters atria causing longer more frequent depolarisation- flows on to ventricles
Treatment of WPW
Drug to control fast rhythm.
Ablation of the accessory pathway
Describe long QT syndrome
Heart disease where there is abnormally long delay between depolarisation and repolarisation of the ventricles.
How does long QT syndrome manifest on ECG
Prolongation of the QT interval (beginning of the QRS to end of T wave)
What are the two common causes of long QT syndrome
Drug induced and genetic mutations typically relating to ion channels
How does hyperkalaemia typically manifest on ECG
Faster repolarisation due to increased K+, this shows as tall peaked P waves
How does hypokalaemia manifest on ECG
Flat T waves
Describe the manifestation of long QT syndrome
Long QT interval often results in abnormal depolarisation of the ventricles, this causes differences in the ‘refractoriness’ of myocytes which can lead to abnormal ventricle activation and thus arrhythmia
What occurs in hypercalacaemia on ECG
Increased Ca2+ leads to inactivation of L-type calcium channels. This reduces the duration of the Ca2+ transient and this action potential duration. Thus QT interval is shortened.
Define infarction
Tissue necrosis caused by lack of oxygen
Define ischaemia
Prolonged lack of oxygen due to interrupted blood supply
For ischaemia, injury and infarction what are the components in ECG that are loosely associated with these events
Ischaemia- T wave
Injury- ST segment
Infarction- QRS complex
What are typically the only residual sign of a MI
Pathological Q waves
Describe the changes to the T wave in ischaemic heart disease
Tall peaked T waves localised to the leads facing the area of injury.
The mechanism for this relates to K+ leakage from damaged myocytes, more rapid repolarisation (as increased ability to reach nernst potential for K+ due to increased K+ permeability)
