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CVS > ECG interpretations > Flashcards

ECG interpretations Flashcards

1
Q

what is the QT interval and why is it corrected for?

A
  • QT interval is the time taken for depolarisation and repolarisation of ventricle.
  • varies with heart rate so needs to be observed in relation to HR.
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2
Q

what does prolonged QT indicate?

A
  • usually 0.44-0.45 secs so, if longer than that suggests prolonged ventricular repolarisations associated with arrhythmias.
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3
Q

name some characteristics of normal sinus rhythms.

A
  • HR 60-100bpm.
  • QRS preceded by normal P wave.
  • PR constant.
  • QRS < 100ms unless delay at interventricular spread.
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4
Q

what is an atrioventricular conduction block?

A
  • delay/failure of conduction of impulses from A–>V via ANV and BOH.
  • first degree, second degree ( mobitz type 1,2 ), third degree heart block.
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5
Q

what causes heart block?

A 
- degeneration of electrical conduction system w/ age.
( sclerosis, fibrosis )
- acute myocardial ischaemia.
- medication.
- valvular heart disease.
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6
Q

what is a first degree AV block?

A
  • depolarisation from SAN spreads to ventricles, but delay in conduction resulting in lengthened PR.
  • may be a sign of coronary artery disease etc.
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7
Q

what is second degree block : mobitz type 1?

A
  • lengthening of the PR intervals and then failure of conduction through to ventricles, resulting in lack of QRS and cycle starts again.
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8
Q

what is second degree block : mobitz type 2?

A
  • PR remains fairly constant with a sudden atrial depolarisation without subsequent ventricular depolarisation so no QRS.
  • irregular ventricular rhythm which may progress to complete heart block.
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9
Q

what is a third degree block?

URGENT PACEMAKER REQUIRED.

A
  • complete failure of spread of conduction to ventricles causing ‘escape mechanism’ (ventricular pacemaker) to take over.
  • 20 to 40bpm which is too slow to maintain BP.
  • wide QRS.
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10
Q

describe the effects of a bundle branch block.

A
  • delay in conduction within bundle branches : RBBB or LBBB.
  • P, PR normal.
  • wide QRS as ventricular depolarisation delayed.
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11
Q

what is a supra-ventricular arrhythmia?

A
  • involves the atria.
  • problem in SAN, AVN or atrium itself.
  • usually concerns tachycardia and narrow QRS complexes.
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12
Q

what can you see in atrial fibrillation?

A
  • no distinct P waves just a wavy baseline.
  • irregular R-R intervals.
  • AVN receives impulses fast and irregularly from cardiac tissue.
  • not all conducted.
  • when conducted normal QRS.
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13
Q

what are the ECG variations seen in Afib?

A
  • HR can be fast (>100), slow (<60) or normal.
  • irregularly irregular.
  • coarse fibrillation or fine fibrillation.
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14
Q

what are the haemodynamic effects of Afib?

A
  • atria quiver, ventricle contraction normal.
  • HR and pulse ‘irregularly irregular’
  • increased blood stasis in atria as loss pf contraction.
  • LA clots so risk of ischaemic stroke secondary to emboli as it may enter LV and systemic.
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15
Q

what is PVC? ( premature ventricular ectopic contractions)

A
  • impulse doesn’t spread via fast His-purkinje, so slower depolarisation of ventricle so wide QRS.
  • abnormal contraction begins at ventricle premature to expected.
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16
Q

what is ventricular Tachycardia?

A
  • more than 3 consecutive PVC may cause.
  • VTACH if persistent may progress to ventricular fibrillation.
  • no adequate cardiac output.
17
Q

what is ventricular fibrillation?

A
  • abnormal, chaotic ventricular depolarisation.
  • impulses from numerous ectopic sited in ventricle.
  • ventricles quiver, no cardiac output as no coordinated contraction.
  • if sustained cardiac arrest!!
18
Q

define ischaemia.

A
  • lack of perfusion but no muscle necrosis (infarction)

- blood tests negative for markers of myocyte necrosis like cardiac troponins.

19
Q

define myocardial infarction.

A
  • muscle necrosis present, so blood test positive for cardiac troponins.
  • STEMI or non-STEMI.
20
Q

what is a STEMI?

ST segment elevation myocardial infarction.

A
  • complete occlusion of coronary artery causing ST elevation as impulse spread abnormal.
  • depending on area of damage ECG from that view affected accordingly.
21
Q

in anterior cardiac wall necrosis what artery is affected?

A
  • left anterior descending artery which carries almost 50% of blood for coronary circulation. ‘widow maker’
  • V3 and V4 sees changes in ECG the most. V2 if septum involved.
22
Q

what does a normal Q wave suggest?

with that in mind, what would a pathological Q wave suggest?

A
  • small Q waves show normal spread of left to right depolarisation on septum.
  • deeper Q seen in leads 3, aVR and none from V1-V3.
  • myocardial necrosis means no electrical activity in dead tissue, so no AP.
  • In anterior wall MI a Q wave seen in V1-V2 abnormally.
23
Q

what other conditions may cause prominent Q waves?

A
  • pulmonary embolism causes Q in lead 3.
24
Q

what is unstable angina?

A
  • ST segment depression while the patient has pain caused by severe ischaemia.
25
Q

what is non- STEMI?

A
  • actual cardiac muscle damage occured but not of entire heart muscle wall.
26
Q

what happens to ST segment at ischaemia/ non-STEMI?

A
  • depression of ST as impulse transversing damaged tissue and moving away from recording electrode.
27
Q

what happens to t wave at ischaemia/ non-STEMI?

A
  • inversion of T wave due to Myocardial ischaemia or non-STEMI damage to area supplied by the coronary artery.
28
Q

what is stable angina?

A
  • ST depression during exercise due to coranary disease; atherosclerotic plaque focising on narrowing.
29
Q

what are the cardiac implications in hypokalaemia?

A
  • palpitations.
  • arrhythmia.
  • cardiac arrest.
30
Q

what ECG changes can be observed in hypokalaemia?

A
  • greater PR.
  • T wave flattening and inversion.
  • ST depression.
  • U waves (repolarisation of purkinje)
31
Q

what are the cardiac implications in hyperkaelemia?

A
  • heart less excitable.
  • palpitations.
  • arrhythmias.
  • cardiac arrest.
32
Q

what ECG changes can be observed in hyperkaelemia?

A
  • tall T waves.
  • loss of p waves.
  • wide QRS.

CVS (12 decks)

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