recognising abnormalities in ECG's

Question 1

which lead would you look at to interpret rhythm

Answer 1

lead 2 - shows best P waves

Question 2

what can be described as a sinus rhythm

Answer 2

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

Question 3

what is heart block

Answer 3

AVN conduction block - delay/failed conduction from atria to ventricles via bundle of HIS

Question 4

what happens during first degree heart block

Answer 4

partial block of AVN. prolonged PR interval > 5 small boxes

Question 5

what happens during the 2 types of second degree heart block

Answer 5

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

Question 6

what happens during 3rd degree heart block

Answer 6

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

Question 7

causes of heart block

Answer 7

actue myocardial infarction - block of right coronary artery which would usually supply AVN
degenerative changes

Question 8

what is bundle branch block

Answer 8

delayed conduction of branches of bundle of HIs = wide QRS as ventricular depolarisation takes longer

Question 9

what is a supra ventricular rhythm and examples

Answer 9

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

Question 10

what is a ventricular rhythm and examples

Answer 10

abnormal ventricular rhythm and pathway. is wide, complex and bizarre. e.g ventricular ectopic beats, ventricular tachycardia and ventricular fibrillation.

Question 11

describe atrial fibrillation; how it arises and how it look =s on an ECG

Answer 11

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

Question 12

explain the effect of ventricular ectopic beats

Answer 12

focus in the ventricle- much slower conduction because doesn’t pass through purkinje system = wide QRS with different shape to normal.

Question 13

explain ventricular tachycardia and what it can lead to

Answer 13

3 consecutive ventricular ectopies at least - v dangerous, fast regular and broad beats. can lead to ventricular fibrillation

Question 14

what is ventricular fibrillation

Answer 14

abnormal, chaotic, fast ventricular fibrillation. no coordinated contraction = NO CARDIAC OUTPUT = cardiac arrest

Question 15

which ECG leads can show which coronary artieries are affected after ischameia/ MI

Answer 15

right coronary artery = II, III and aVF
LAD= V1-V4
circumflex artery = I, aVL, V5 and V6

caused by narrowing or occlusion

Question 16

difference between schema and MI

Answer 16

ischaemia - no muscle necrosis, use blood test to check for troponin.
MI - muscle necrosis is present. can be STEMI or nonSTEMI

Question 17

what is a STEMI

Answer 17

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

Question 18

changes seen in the ECG of a STEMI

Answer 18

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

Question 19

what is a non- STEMI

Answer 19

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

Question 20

describe stable angina

Answer 20

has same ECG trace as non-STEMI. only way to differentiate is to do a blood test to test for myoctye injury - troponin.

Question 21

what is unstable angina

Answer 21

normal at rest but then during exercise get ST depression

Question 22

what is hyperkalaemia (increased extracellular potassium)

Answer 22

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+

Question 23

what is hypokalaemia (decreased extracellular potassium)

Answer 23

greater difference in RMP = hyper polarisation. may cresults in low T wave and high U wave look at pic