ECG Abnormalities Flashcards
Differentiate between supraventricular and ventricular abnormal rhythms on an ECG
Supraventricular abnormal rhythms have normal QRS complexes
Ventricular abnormal rhythms have widened QRS complex and conduction not via usual His-purkinje system
Identify atrial fibrillation on an ECG
Multiple atrial foci, impulses chaotic
Atrial depolarisation uncoordinated - no P-wave, just wavy baseline, irregular R-R intervals
Atria quiver rather than contract
Impulses arrive at AV node at rapid irregular rate
Only some conducted to ventricles - AV node not refractory
Stagnation of blood due to irregular contraction could lead to clotting
Pulse and heart rate irregularly paced
Ventricles depolarise and contract normally
Irregularly irregular wave
What is heart block
AV conduction blocks where there is delay/failure of conduction of impulses from atrium to ventricles via AV node and bundle of His
Identify first degree heart block on ECG
Slow conduction in AV node and bundle of His
PR interval prolonged - more than 5 squares
Normal P-wave and QRS complex
Normally asymptomatic
Identify secondary degree heart block on ECG
Mobitz type 1 (Wenkebach phenomenon)
Progressive lengthening of PR interval until one P-wave is not conducted
Allows AV node to recover, and cycle begins again
Mobitz type 2
PR interval normal
Sudden non-conduction of a beat - lost QRS complex
High risk of progression to complete heart block
Identify third degree heart block on ECG
Atrial depolarisation normal but impulses not conducted to ventricle
Ventricular pacemaker (escape rhythm) takes over
Rate is very slow (30-40bpm) - wide QRS complex
Heart rate often too slow to maintain blood pressure and perfusion - urgent pacemaker insertion required
No relationship between P-waves and QRS complex
P-R interval completely variable from beat to beat
Identify ventricular ectopic beats on ECG
Ectopic focus in ventricular muscle (irregular signal beginning)
Normal sinus beat but sudden wide QRS complex
Impulse not spread via the fast His-purkinje system
Slower depolarisation of ventricle
Identify ventricular tachycardia on ECG
More than 3 consecutive ventricular ectopics
Persistent ventricular tachycardia is a dangerous rhythm - needs urgent treatment
High risk of ventricular fibrillation
Fast, regular and broad beats
Identify ventricular fibrillation on ECG
Abnormal, chaotic, fast ventricular depolarisation
Impulses from numerous ectopic sites in ventricular muscle
Ventricle doesn’t contract in coordinated way and thus no cardiac output = cardiac arrest
Require defibrillation to restore rhythm
Identify left bundle branch block on ECG
Wide QRS complex as ischaemia of heart delays signals
Goes down one bundle, begins to depolarise before other bundle depolarises
Non-synchronous ventricle contraction
Linked to mitral regurgitation
Fixed by re-sync two ventricles - place lead into left and right ventricle
Identify myocardial ischaemia on an ECG
ST segment depression and T wave inversion at the respective lead
Sub-endocardial region is most vulnerable - not full thickness ischaemia
Exercise ECG can better detect ischaemia
Identify myocardial infarction on ECG
ST segment elevation Muscle injury extends full thickness from endocardium to epicardium
What is meant by pathological Q waves
Normal Q-wave are short and narrow
Pathological if more than 1 small square wide, more than 2 small squares deep
Identify hyperkalaemia on ECG
Resting membrane potential less negative, thus heart less excitable
Tall ‘tented’ T waves
ST depression if serious
Identify hypokalaemia on ECG
T wave becomes flatter and could be inverted
ST depression
U-wave formed which follows T-wave
