cardiology: ecg Flashcards
purpose of performing ecg
1) physiologic parameters
2) coronary blood supply
3) conduction system
4) electrolyte abnormalities
5) structural problems
6) infection/inflammation
7) drugs (SE/toxicity)
8) extra cardiac disease (respi/thyroid)
9) physiological response (fever, fear, anxiety, hypovolemic shock, vasovagal syncope)
10) trauma
what is the tetrad in tetralogy of fallot
1) rvh
2) ps
3) overriding aorta
4) vsd
draw and label components of ecg
1) PR interval
2) PR segment
3) QRS interval
4) ST interval
5) ST segment
6) QT interval
7) RR interval
2 key characteristics of SA node
1) automaticity
2) intrinsic rate
avn does not allow 1:1 conduction beyond ___
150
position of v1 lead
4th intercostal space to the right of sternum
position of v2 lead
4th intercostal space to the left of sternum
position of v4 lead
5th intercostal space mid clavicular line
position of v3 lead
directly between v2 and v4
position of v5 lead
level with v4 at left anterior axillary line
position of v6 lead
level with v5 at left midaxillary line
bipolar lead I
RA & LA
bipolar lead II
RA & LL
bipolar lead III
LA & LL
augmented unipolar lead aVR
RA
augmented unipolar lead aVL
LA
augmented unipolar lead aVF
LL
what surface/region/coronary artery of the heart do leads I, II, aVL look at?
left lateral surface
LV
LCx
what surface/region/coronary artery of the heart do leads II, III, aVF look at?
inferior surface
mainly RV (some LV)
RCA
what surface/region/coronary artery of the heart do leads V1, V2 look at?
anteroseptal region
mainly LV
LAD
what surface/region/coronary artery of the heart do leads V3, V4 look at?
IV septum and LV
LV
LCx
what surface/region/coronary artery of the heart do leads V5, V6 look at?
anterior/lateral wall of LV
LV
LCx
what surface/region/coronary artery of the heart does lead avR look at?
lateral surface
what surface/region/coronary artery of the heart does lead avR look at?
lateral surface
physiological significance of P wave
depolarisation of atria in response to SA node triggering
physiological significance of PR interval
delay of AV node to allow filling of ventricles
physiological significance of QRS complex
depolarisation of ventricles
physiological significance of ST segment
beginning of ventricle repolarisation (should be flat)
physiological significance of T wave
ventricular repolarisation
what does size of QRS complex represent?
muscle mass
approach to interpreting ecg
1) check normal features first (speed, scale)
2) 7+2 step plan
what does each large square on ecg represent?
200ms (0.2s)
what does each small square on ecg represent?
40ms (0.04s)
what is the scale of an ecg?
10mm/mV
what are the 7 +2 steps of an ecg?
7 steps:
1) rhythm
2) rate
3) conduction interval
4) heart axis
5) p wave
6) qrs complex
7) st segment
+2 steps:
1) compare with previous ecg
2) conclusion
maximum height of P waves in sinus rhythm in leads II and/or III
2.5mm
what is considered tachycardia?
> 100bpm
what is considered narrow complex tachycardia?
QRS < 120ms
>100bpm
types of REGULAR narrow complex tachycardia
1) sinus tachycardia
2) atrial tachycardia
3) atrial flutter with fixed conduction
4) SVT: AV nodal re-entry tachycardia (AVNRT), orthodromic AVRT, junctional tachycardia
causes of sinus tachycardia
- fever
- pain
- sepsis
- hypovolemia/haemorrhage
- drugs: adrenaline, atropine, antihistamines, b agonists, sympathomimetics, GTN
- endocrine: thyrotoxicosis
- serious life threatening conditions: myocarditis, pulmonary embolism, CCF, ectopic pregnancy
what is considered wide complex tachycardia?
QRS > 120ms
what criteria describes the features of VT?
brugada criteria
features of VT based on brugada criteria
- fusion beats
- absence of RS complex in precordial leads
- concordance in precordial leads (all QRS upwards or downwards)
- RS interval > 100ms
- AV dissociation
- atypical LBBB
features of AVNRT
- regular, 180-250/min
- P in QRS complex (resulting in RsR’ in V1)
- young patients and paroxysmal
- treatment: valsalva/carotid massage/adenosine
what type of wide complex tachycardia is torsades de pointes?
polymorphic ventricular tachycardia
how does torsades de pointes usually present?
pulseless in cardiac arrest
treatment for torsades de pointes?
IV MgSO4 1g x 1-2 doses
usual demographic for VT
older patient with previous MI
reference range for bradycardia
<60bpm
reference range for 1st degree heart block
PR interval > 200ms (>1 large square/>5 small squares)
types of second degree heart block
1) mobitz I (wenckebach phenomenon)
2) mobitz II
describe mobitz I heart block
progressive PR interval prolongation culminating in non-conducted P wave (usually benign)
usual wenckebach pattern of P:QRS
3: 2
4: 3
5: 4
cause of mobitz I heart block
reversible conduction block at AV node
- drugs; bb, ccb, digoxin, amiodarone
- increased vagal tone in athletes
- MI
- myocarditis
- post cardiac surgery
describe mobitz II heart block
intermittent non-conducted P waves without progressive prolongation of PR interval
cause of mobitz II heart block
failure of conduction at level of his-purkinje system
mobitz II is more likely than mobitz I to be associated with _____ , _____ and progression to ____ ?
haemodynamic compromise
severe bradycardia
3rd degree heart block
describe 3rd degree heart block
no relationship between p wave and qrs complex (absence of AV conduction)
typical presentation of 3rd degree heart block
severe bradycardia with av dissociation (independent atrial and ventricular rates)
method to calculate HR on ecg
300/number of large squares between 2 consecutive R waves
OR
no. of QRS complexes in rhythm strip x 6
normal PR interval
120-200ms (3-5 squares)
conduction interval in WPW syndrome
PR interval <120ms + delta wave
PR interval <120ms without delta wave
lown-ganong-levine syndrome
normal QTc interval
<420ms in men
<450ms in women
formula for calculation of QTc
bezett’s formula
what is bezett’s formula?
QTc = QT interval/ (RR)^1/2
QTc: corrected QT interval
QT interval: Q wave to end of T wave
RR: time from 2 consecutive RR waves
reference range for prolonged QTc
> 450ms
causes of prolonged QTc
1) electrolyte imbalances (hypokalemia/calcemia/magnesemia)
2) hypothermia
3) raised ICP
4) post MI
5) congenital long QT syndromes (romano-ward syndrome, jervell and lange nielsen)
6) drugs
inheritance pattern of romano-ward syndrome
AD
inheritance pattern of jervell and lange-nielsen
AR
a/w congenital deafness
drugs which cause prolonged QTc interval
1) antipsychotics
2) type IA, IC and III anti arrhythmics
3) tricyclic antidepressants
4) antihistamines
5) others: chloroquines, hydroxychloroquine, quinine, macrolides (erythromycin, clarithromycin)
reference range for shortened QTc
<350ms
causes of shortened QTc
1) hypercalemia
2) congenital short QT syndrome (K+ channel defect - AD)
3) digoxin effect
normal cardiac axis
-30deg to +90deg
causes of left axis deviation (lead I +ve and AVF -ve)
- may be normal in short and fat individuals
- LVH
- RV infarct
- L anterior hemiblock
causes of right axis deviation (lead I -ve and AVF +ve)
- may be normal in tall and thin individuals
- RVH
- congenital diseases involving R heart
- LV infarct
- L posterior hemiblock (rare)
- dextrocardia
- reversal of arm leads
normal PR interval
0.12-0.2s
describe p wave in p pulmonale
peaked, tall P wave
height in p wave on inferior leads (II, III, aVF) in p pulmonale
> 2.5mm
height of p wave in V1 and V2 in p pulmonale
> 1.5mm
causes of p pulmonale
1) cor pulmonale
2) tricuspid stenosis
3) congenital heart disease (pulmonary stenosis, ToF, primary pulmonary HTN)
causes of absent p wave
1) AF
2) junctional/ventricular rhythm
describe p wave in p mitrale
bifid, broad
what does p mitrale indicate
LA enlargement
what does p pulmonale indicate
RA enlargement
p mitrale is a precursor to ____
AF
appearance of p wave in lead II in p mitrale
bifid p wave >40ms between both peaks
total p wave duration >110ms
appearance of p wave in lead V1 in p mitrale
biphasic p wave with terminal negative portion >40ms
terminal negative portion > 1mm deep
causes of p mitrale
1) mitral stenosis (classical)
2) mitral regurgitation
3) systemic HTN
4) aortic stenosis
5) HOCM
causes of p wave inversion
ectopic atrial rhythm e.g. MAT
normal duration of QRS complex
≤ 120ms (3 small squares)
causes of pathologic Q waves in V1/V2
old STEMI
what is the index for voltage criteria of LVH?
sokolow-lyon-index
what is the voltage criteria for LVH according to the sokolow-lyon index?
R in V5/V6 + S in V1 > 35mm
normal R wave progression
R increases V1-V5
R>S beyond V3
types of abnormal R wave progression
1) no R wave
2) exaggerated R wave progression
3) reversed R wave progression
4) small R waves with little progression
what does absence of R wave indicate
evolved/old anterolateral STEMI (+ Q waves)
what does exaggerated R wave progression indicate
LVH
what does reversed R wave progression indicate
RVH
what does small R waves with little progression indicate
pericardial effusion
5 causes of large R waves in V1
1) dextrocardia
2) RVH
3) posterior AMI
4) type A WPW
5) RBBB
causes of microvoltages (<5mm) of QRS complex
1) cardiac tamponade/pericardial effusion/pericarditis
2) hypothyroidism
3) pleural effusion/pneumothorax
4) cardiomyopathy (e.g. amyloidosis)
5) COPD (hyperinflated chest + leads located far away from heart)
6) obesity (thick chest wall + leads located far away from heart)
causes of widened QRS complexes (>3 small squares)
1) BBB
2) pre excitation (WPW)
3) ventricular extrasystoles/VT
4) complete heart block
causes of ST elevation (>1mm)
1) AMI (STEMI)
2) coronary vasospasm (printzmetal’s angina)
3) pericarditis
4) benign early repolarisation
5) hyperkalemia
6) LBBB
7) LVH
8) ventricular aneurysm
9) ventricular paced rhythm
10) raised ICP
11) brugada syndrome
features of pericarditis on ecg
1) globally raised ST segments
2) saddle shaped ST elevations
3) PR depression in all leads
4) PR elevation in aVR
appearance of T waves in hyperkalemia
tall tented T waves
cause of brugada syndrome
mutation in na+ channel
what factors unmask/augment brugada syndrome?
- fever
- ischemia
- drugs
- hypokalemia
- hypothermia
- post cardioversion
drugs which unmask/augment brugada syndrome
1) na+ channel blockers (e.g. flecainide, propafenone
2) ca2+ channel blockers
3) alpha agonists
4) beta blockers
5) nitrates
6) cholinergics
7) alcohol/cocaine
who is the most perfect girl in the world?
chlochlo!
types of brugada syndrome ecg patterns
1) type 1: coved type ST segment elevation
2) type 2: saddleback type ST segment elevation
3) type 3: saddleback type st segment elevation <1mm
describe type 1 brugada’s syndrome
1) brugada’s sign +
2) one of the following:
- documented VF or polymorphic VT
- F/H of sudden cardiac death at <45yo
- coved type ECGs in family members
- inducibility of VT with programmed electrical stimulation
- syncope
- nocturnal agonal respiration
describe brugada’s sign
coved ST segment elevation >2mm in >1 of V1-V3 + negative T wave
describe type 2 brugada syndrome
> 2mm of saddleback shaped st elevation
describe type 3 brugada syndrome
morphology of either type 1 or 2 but with <2mm of ST segment elevation
causes of ST depression (≥1mm)
1) ischemia/unstable angina
2) NSTEMI
3) digoxin (reverse tick sign)
4) reciprocal changes in STEMI
5) posterior MI (leads V1-V3)
6) hypokalemia
7) supraventricular tachycardia
8) RBBB
9) RVH
10) LBBB
11) LVH
12) ventricular paced rhythm
causes of peaked T wave
1) hyperkalemia
2) hypermagnesemia
3) hyperacute T wave in STEMI (less tented, broad base)
4) normal grusin type II variant
causes of flat and prolonged T wave
hypokalemia
physiological causes of T wave inversion
- normal in children
- normal in V1 in males, V1-V2 in females
pathological causes of T wave inversion
1) subendocardial ischemia
2) LVH
3) PE (V1-V3)
4) electrolyte imbalances
5) bundle branch block
6) ventricular hypertrophy (‘strain’ patterns)
7) hypertrophic cardiomyopathy
8) raised ICP
pathological causes of u waves
hypokalemia
hypomagnesemia
ecg features of RBBB
1) typical RSR’ pattern (m shaped QRS) in V1-3 (right rabbit ear taller)
2) wide slurred s wave in lateral leads (I, aVL, V5-6)
3) broad QRS > 120ms
4) axis deviation to either side
5) limb leads have non specific triphasic pattern
6) ST depression and T inversion
mode of depolarisation of RV in RBBB
cell to cell conduction
causes of RBBB
1) may be normal
2) acquired
- right ventricular hypertrophy/cor pulmonale
- pulmonary embolus
- ischaemic heart disease
- rheumatic heart disease
- myocarditis or cardiomyopathy
- degenerative disease of conduction system
3) congenital
- congenital heart disease (e.g. ASD)
- ebstein’s anomaly
ecg features of LBBB
1) triphasic pattern in lateral leads V5-6
2) dominant s wave in V1
3) QRS duration of >120ms
4) broad monophasic R wave in lateral leads (I, aVL, V5-6)
5) absence of Q waves in lateral leads (I, V5-6; small waves allowed in aVL)
6) prolonged R wave peak time >60ms in left precordial leads (V5-6)
causes of LBBB
1) aortic stenosis
2) ischaemic heart diseaes
3) hypertension
4) dilated cardiomyopathy
5) anterior MI
6) primary degenerative disease (fibrosis) of conducting system (e.g. Lenegre disease)
7) hyperkalemia
8) digoxin toxicity
name of scoring system for acute coronary system in LBBB
smith- modified sgarbossa’s criteria
describe smith-modified sgarbossa’s criteria
1) concordant ST elevation ≥1mm in ≥ 1 lead
2) concordant ST depression ≥1mm in ≥1 lead of V1-V3
3) proportionally excessive discordant STE in ≥ 1 lead anywhere with ≥ 1mm STE (as defined by ≥25% of the depth of the preceding S wave)
conduction system supplied by RCA
- SAN, AVN, bundle of his
- variable twig to posterior fascicle of LBB
conduction system supplied by LCA
- RBB and anterior fascicle of LBB
- variable twig to posterior fascicle of LBB
- anterior STEMI: RBBB + left posterior hemiblock
ecg features in left anterior hemiblock
1) left axis deviation of at least -45
2) rS complexes in inferior leads II, III, aVF
3) qR complexes in lead I and aVL
pathophysiology of left anterior hemiblock
- usually due to previous ischemic insult
- delayed activation of anterior portion of LV due to blocked/delayed transmission in anterior fascicle
ecg features of left posterior hemiblock
1) R axis deviation 90-180 degrees
2) normal QRS complex
3) presence of qR complex in inferior leads II, III, aVF
4) rS complex in lead I
types of combined blocks
1) bifascicular block
2) trifascicular block
describe bifascicular blocks
RBBB + left anterior/posterior hemiblock
- RBBB + left axis deviation
desecribe trifascicular blocks
RBBB + LAFB + 1st degree heart block
- high risk of entering complete heart block
types of ectopic beats
1) escape beats
2) premature beat
describe escape beats
- failure of SAN to discharge (dysfunctional SAN) > beat later than expected
- pause BEFORE ectopic beat (sinus arrest)
describe premature beats
- ectopic pacemaker discharges before SAN > beat earlier than expected
- pause AFTER ectopic beat
- normal SAN
define escape rhythm
ectopic pacemaker continues pacemaking function to maintain CO
types of escape rhythms
1) atrial escape rhythm
2) junctional escape rhythm
3) ventricular escape rhythm
HR in atrial escape rhythm
normal; 60-80bpm
HR in junctional escape rhythm
40-60 bpm
regular
HR in ventricular escape rhythm
20-40bpm
regular
morphology of atrial escape rhythm
indistinguishable from sinus rhythm
morphology of junctional escape rhythm
1) no P waves
2) narrow QRS
consequences of junctional escape rhythm
usually tolerated
management of junctional escape rhythm
treat underlying cause