recognising abnormalities in ECG's Flashcards
which lead would you look at to interpret rhythm
lead 2 - shows best P waves
what can be described as a sinus rhythm
regular rhythm, heart rate between 60-100bpm, present P waves, shape of P waves I upright in leads 1 and 2
P-R interval = 3-5 small boxes
QRS interval = < 3 small boxes
every P wave is followed by QRS and every QRS followed by P wave
what is heart block
AVN conduction block - delay/failed conduction from atria to ventricles via bundle of HIS
what happens during first degree heart block
partial block of AVN. prolonged PR interval > 5 small boxes
what happens during the 2 types of second degree heart block
morbitz type 1 - successively longer PR intervals until QRS is dropped - cycle starts again
morbitz type 2 - PR intervals don’t lengthen but QRS is suddenly dropped
what happens during 3rd degree heart block
complete failure of AVN. a ventricular pace maker takes over from AVN which makes QRS very wide because takes longer to depolarise than purkinje fibres. may have what seems to be dropped QRS because P waves and QRS are happening unsynchronised as they are under different control
causes of heart block
actue myocardial infarction - block of right coronary artery which would usually supply AVN
degenerative changes
what is bundle branch block
delayed conduction of branches of bundle of HIs = wide QRS as ventricular depolarisation takes longer
what is a supra ventricular rhythm and examples
abnormal rhythm due to irregular beats in SAN, ectopic beats in the atrium or irregular beats originating from the AVN after this follows same pathway across the ventricles. atrial pathway is abnormal e.g atrial fibrillation
what is a ventricular rhythm and examples
abnormal ventricular rhythm and pathway. is wide, complex and bizarre. e.g ventricular ectopic beats, ventricular tachycardia and ventricular fibrillation.
describe atrial fibrillation; how it arises and how it look =s on an ECG
arises from multiple atrial foci, no P waves, just wavy baseline. because there are so many random impulses from the atria not all can be passed on to AVN sue to its refectory period = narrow QRS, irregular RR intervals- because normals atrial conduction lost
explain the effect of ventricular ectopic beats
focus in the ventricle- much slower conduction because doesn’t pass through purkinje system = wide QRS with different shape to normal.
explain ventricular tachycardia and what it can lead to
3 consecutive ventricular ectopies at least - v dangerous, fast regular and broad beats. can lead to ventricular fibrillation
what is ventricular fibrillation
abnormal, chaotic, fast ventricular fibrillation. no coordinated contraction = NO CARDIAC OUTPUT = cardiac arrest
which ECG leads can show which coronary artieries are affected after ischameia/ MI
right coronary artery = II, III and aVF
LAD= V1-V4
circumflex artery = I, aVL, V5 and V6
caused by narrowing or occlusion
difference between schema and MI
ischaemia - no muscle necrosis, use blood test to check for troponin.
MI - muscle necrosis is present. can be STEMI or nonSTEMI
what is a STEMI
complete occlusion of coronary artery by thrombus = ST elevation - requires urgent re-profusion . use different leads to find out which coronary artery has been occluded
changes seen in the ECG of a STEMI
injury = ST elevation and then once necrosis has taken place ST gone and Q wave appears. deep Q wave. this is due to window from necrosis which can see opposite side of heart - this activity is picked up . look at pic
what is a non- STEMI
subchondral injury in the myocardium. causes ST depression and T wave inversion - behaves as is current is moving toward the injury . look at pic to fully understand
describe stable angina
has same ECG trace as non-STEMI. only way to differentiate is to do a blood test to test for myoctye injury - troponin.
what is unstable angina
normal at rest but then during exercise get ST depression
what is hyperkalaemia (increased extracellular potassium)
increased potassium =less negative RMP and depolarisation of membrane = inactivation of sodium channels -heart becomes less excitable. at v high potassium you get merged S and T and looks like maths sine wave. v wide QRS too. must look at pic because also changes depending on amount of K+
what is hypokalaemia (decreased extracellular potassium)
greater difference in RMP = hyper polarisation. may cresults in low T wave and high U wave look at pic
