ecg basics & cardicac physiology
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ECG BASICSECG BASICS&&
PHYSIOLOGYPHYSIOLOGYOFOF
HEARTHEARTSUBHANJAN DASSUBHANJAN DAS
Heart is a pumping Heart is a pumping organorgan
How heart keeps How heart keeps pumping?pumping?
1.special structure of cardiac muscle1.special structure of cardiac muscle syncytial naturesyncytial nature both resting membrane potential & both resting membrane potential &
action potential are different form action potential are different form skeletal muscleskeletal muscle
2.auto rhythmicity of heart2.auto rhythmicity of heart
Action potential of heart Action potential of heart musclemuscle
Factors affecting action Factors affecting action potentialpotential
1 K+ concentration1 K+ concentration 2 Ca++ concentration2 Ca++ concentration 3Na+ concentration3Na+ concentration 4 temperature4 temperature
Excitation contraction Excitation contraction couplingcoupling
Excitation contraction Excitation contraction couplingcoupling
Duration of contractionDuration of contraction
Atria 0.2secAtria 0.2sec Ventricle 0.3 secVentricle 0.3 sec Normally contraction time is 40% of Normally contraction time is 40% of
cardiac cycle. When heart rate cardiac cycle. When heart rate increases 3 times it is 65% of increases 3 times it is 65% of cardiac cycle.cardiac cycle.
Relaxation decreasesRelaxation decreases Ventricular filling decreasesVentricular filling decreases
Cardiac cycleCardiac cycle
Atrial systoleAtrial systole
IMCIMC
ejection phaseejection phase
IMRIMR
Heart soundsHeart sounds
Regulation of pumpingRegulation of pumping
1Frank Starling mechanism1Frank Starling mechanism 2 autonomic innervation2 autonomic innervation Within physiological limit heart Within physiological limit heart
pumps all the blood that comes to it pumps all the blood that comes to it without allowing excessive pooling without allowing excessive pooling of blood in the veins of blood in the veins
Parasympathetic Parasympathetic innervationinnervation
Effects of autonomic Effects of autonomic stimulationstimulation
Chronotropic effect Chronotropic effect Dromotropic effectDromotropic effect Bathmotropic effectBathmotropic effect Inotropic effectInotropic effect
Effects of autonomic Effects of autonomic stimulationstimulation
Sympathetic stimulation: HR can go Sympathetic stimulation: HR can go upto 250 bpm in young individual.upto 250 bpm in young individual.
Parasympathetic stimulation: HR Parasympathetic stimulation: HR can go down to zero. Although vagal can go down to zero. Although vagal escape follows.escape follows.
Both Sympathetic and Both Sympathetic and parasympathetic system maintain a parasympathetic system maintain a low level firing at resting condition.low level firing at resting condition.
Energy considerationsEnergy considerations Source: oxidative respirationSource: oxidative respiration FA- biggest sourceFA- biggest source glucose/ lactate also usedglucose/ lactate also used Energy efficiency max 20-25%, rest Energy efficiency max 20-25%, rest
is converted to heat (HF: 5-10% )is converted to heat (HF: 5-10% ) Expenditure increases when Expenditure increases when ventricles are ventricles are
dialateddialated BP is elevatedBP is elevatedEnergy expenditure is measured by Energy expenditure is measured by
oxygen comsumptionoxygen comsumption
Special conductive Special conductive systemsystem
Rate of discharge Rate of discharge
SA node 70-80 bpmSA node 70-80 bpm AVnode 40-60 bpmAVnode 40-60 bpm AV bundle 15-40 bpmAV bundle 15-40 bpm
Autorhythmicity of SA Autorhythmicity of SA nodenode
Autorhythmicity of SA Autorhythmicity of SA nodenode
Autorhythmicity of SA Autorhythmicity of SA nodenode
Autorhythmicity of SA Autorhythmicity of SA nodenode
Autorhythmicity of SA Autorhythmicity of SA nodenode
Special conductive Special conductive systemsystem
Nodal delayNodal delay .09sec AV node.09sec AV node .04 sec penetrating .04 sec penetrating
portionportion Additional .03 sec Additional .03 sec
internodal pathwayinternodal pathway
Ectopic pacemakerEctopic pacemaker
Heart blockHeart block Stokes Adams syndromeStokes Adams syndrome
ECGECG
Heart muscle wraps around heart Heart muscle wraps around heart like a double spiral with a fibrous like a double spiral with a fibrous septa between the spiral layers.septa between the spiral layers.
Flow of currentFlow of current
leadsleads
Other leadsOther leads Chest leads 6 in no.Chest leads 6 in no. + pole connected to chest, -ve to all 3 + pole connected to chest, -ve to all 3
limbslimbs Infrequently 7Infrequently 7th th & 8 & 8thth chest leads & chest leads &
esophageal leads used.esophageal leads used. aVR- Rt +veaVR- Rt +ve aVF- Lt leg +veaVF- Lt leg +ve aVL- Lt arm +veaVL- Lt arm +ve Recording of V1 V2 upside down as it is Recording of V1 V2 upside down as it is
more closer to base rather than apexmore closer to base rather than apex
Axis of leadsAxis of leads
Vector Vector
Instantaneous mean vector:Instantaneous mean vector:
At any given instance the total amount At any given instance the total amount of current flowing in the heart is of current flowing in the heart is represented in magnitude and represented in magnitude and direction by the vector. Current direction by the vector. Current flows from DEPOLARISED to flows from DEPOLARISED to POLARISED area i.e. NEGATIVE to POLARISED area i.e. NEGATIVE to POSITIVE POSITIVE
Vector analysisVector analysis
Closer the angle higher is the Closer the angle higher is the componentcomponent
+ve vector: reading above the +ve vector: reading above the baselinebaseline
- ve vector: reading below the - ve vector: reading below the baselinebaseline
Mean vectorMean vector
Axis deviationAxis deviation
1Normal:1Normal:
20degree to left, 100 degree to right20degree to left, 100 degree to right
Lt RtLt Rt
Expiration InspirationExpiration Inspiration
Supine StandingSupine Standing
Fat Tall/ leanFat Tall/ lean
2Hypertrophy / conduction block2Hypertrophy / conduction block
Left Deviation : Left Deviation : pathologicalpathological
HypertensionHypertension Aortic valve stenosisAortic valve stenosis RegurgitationRegurgitation LBBBLBBB
LBBB Left Deviation LBBB Left Deviation
Right DeviationRight Deviation
Pulmonary stenosisPulmonary stenosis Fallots tetralogyFallots tetralogy VSDVSD Pulmonary hypertensionPulmonary hypertension RBBBRBBB
Right DeviationRight Deviation
Vector analysis: axis Vector analysis: axis deviationdeviation
High voltage ECGHigh voltage ECG
Normally peak of R to bottom of S: Normally peak of R to bottom of S: 0.5 to 2 mv0.5 to 2 mv
Abnormally large: summation of all 3 Abnormally large: summation of all 3 leads >4mvleads >4mv
Cause :hypertrophyCause :hypertrophy
Low voltage ECGLow voltage ECG
1 decreased current production1 decreased current production
low muscle mass: common in old low muscle mass: common in old MI propagation also slowed- MI propagation also slowed- prolongationprolongation
2 reduced conduction2 reduced conduction A. pericardial effusionA. pericardial effusion B. pulmonary emphysemaB. pulmonary emphysema 3 flow in AP axis3 flow in AP axis
rotation of axisrotation of axis
Prolonged QRS complexProlonged QRS complex Normal : 0.06- 0.08 secNormal : 0.06- 0.08 sec Hpertrophy or dilatation of ventricles: Hpertrophy or dilatation of ventricles:
conduction prolonged .09- .12secconduction prolonged .09- .12sec
Prolongation in BBB- propagation Prolongation in BBB- propagation through muscle:through muscle:
>.09 sec abnormal>.09 sec abnormal>.12- almost certain to be pathological >.12- almost certain to be pathological
block in ventricular conduction systemblock in ventricular conduction system>.14 – complete block>.14 – complete block
Bizzare QRS complexBizzare QRS complex
1 scar tissue 1 scar tissue 2 Multiple block2 Multiple block
Current of injuryCurrent of injury
Current of injuryCurrent of injury
Injured area: depolarised- emits –Ve Injured area: depolarised- emits –Ve charge.charge.
Injury: mechanical/ infection/ Injury: mechanical/ infection/ ischemiaischemia
As the area remains continuously As the area remains continuously depolarised a current flow in the depolarised a current flow in the ventricle even before QRS starts. This ventricle even before QRS starts. This is Current of injury.is Current of injury.
Axis deviation also presentAxis deviation also present
Current of injuryCurrent of injury J pointJ point
No current flows when the ventricles No current flows when the ventricles are fully depolarised. So the iso are fully depolarised. So the iso electric point is seen at the end of QRS electric point is seen at the end of QRS complex.this is called J point.complex.this is called J point.
ST segment shiftST segment shift
As the Current of injury is present the As the Current of injury is present the TP segment is shifted. But in common TP segment is shifted. But in common practice it is considered TP is in iso practice it is considered TP is in iso electric line. So this phenomenon is electric line. So this phenomenon is usually termed as ST segment shiftusually termed as ST segment shift
Current of injuryCurrent of injury
Current of injuryCurrent of injury
T WAVE ABNORMALITYT WAVE ABNORMALITY
Arrhythmias Arrhythmias
1 tachycardia 1 tachycardia
>100bpm, normal but shorter waves>100bpm, normal but shorter waves
Causes:Causes:
Temperature- 10beats/degree F upto Temperature- 10beats/degree F upto 105degree 105degree
Sympathetic stimulationSympathetic stimulation
toxicitytoxicity
2 bradycardia:2 bradycardia:
<60 bpm<60 bpm
Athletes, carotid sinus syndromeAthletes, carotid sinus syndrome
Due to increased vagal stimulationDue to increased vagal stimulation
Sinus arrhythmiaSinus arrhythmia
Can result from any circulatory reflex Can result from any circulatory reflex that alters the strength of the that alters the strength of the autonomic signal to SA nodeautonomic signal to SA node
Respiratory type results from spill over Respiratory type results from spill over of signals from the medullary of signals from the medullary respiratory centre to vasomotor centre.respiratory centre to vasomotor centre.
Normal 5% variation in inspiration and Normal 5% variation in inspiration and expiration.expiration.
Deep breathing: 10%Deep breathing: 10%
Sinoatrial blockSinoatrial block
Block in SA nodeBlock in SA node No P waveNo P wave AV nodal rhythm AV nodal rhythm Normal QRS-TNormal QRS-T Slow Slow
AV BlocksAV Blocks
Ischemia of AV node/ bundleIschemia of AV node/ bundle Compression of bundle: scar/ Compression of bundle: scar/
calcified portioncalcified portion Inflammation of AV node/ bundleInflammation of AV node/ bundle
myocarditis/ diptheria/ rheumatic myocarditis/ diptheria/ rheumatic feverfever
Extreme vagal stimulation:Extreme vagal stimulation:
carotid sinus syndromecarotid sinus syndrome
AV blockAV block
A.A. IncompleteIncomplete
1. first degree: prolonged PR 1. first degree: prolonged PR interval (>.20 sec). Conduction is interval (>.20 sec). Conduction is delayed but no actual blockage.delayed but no actual blockage.
May prolong upto .35-.45 secMay prolong upto .35-.45 sec
The measurement of duration The measurement of duration gives estimate of severity.gives estimate of severity.
2. second degree2. second degree
here also PR prolonged. Some here also PR prolonged. Some beats strong enough to go through beats strong enough to go through block some are not. So for some P block some are not. So for some P wave QRS complex is present wave QRS complex is present whereas for some it is absent. whereas for some it is absent.
2:1/3:2/3:1 rhythms are present 2:1/3:2/3:1 rhythms are present sometimessometimes
Third degreeThird degree
No impulse propagation to AV nodeNo impulse propagation to AV node Atrioventricular dissociationAtrioventricular dissociation
Atria 100 bpm ventricle Atria 100 bpm ventricle 40 bpm40 bpm
Bundle branch blockBundle branch block
A branch of the bundle delays A branch of the bundle delays propagationpropagation
Normal side contracts firstNormal side contracts first Duplication of 1Duplication of 1stst heart sound heart sound Prolonged QRSProlonged QRS More severe when on the left sideMore severe when on the left side
Arborisation blockArborisation block
Purkinje fibre dysfunction due to Purkinje fibre dysfunction due to chronic myocardial damagechronic myocardial damage
Other abnormalitiesOther abnormalities
Stokes Adams syndromeStokes Adams syndrome
Borderline ischemia of conductive Borderline ischemia of conductive tissuetissue
Electrical alternansElectrical alternans
tachycardiatachycardia
IschaemiaIschaemia
Myocarditis Myocarditis
Digitalis toxicityDigitalis toxicity
Premature beatsPremature beats
Extrasystole & compensatory pauseExtrasystole & compensatory pauseo Local areas of ischemiaLocal areas of ischemiao Small calcified plaques at different Small calcified plaques at different
points of heart- irritatingpoints of heart- irritatingo Mechanical stimulation during cardiac Mechanical stimulation during cardiac
catheterisationcatheterisationo Toxic irritation nicotine, caffeine, drugsToxic irritation nicotine, caffeine, drugso Pulse deficite & bigeminal pulsePulse deficite & bigeminal pulse
AV nodal/ bundle premature contractionAV nodal/ bundle premature contraction
P wave not distinct, atria & ventricles P wave not distinct, atria & ventricles depolarises at the same timedepolarises at the same time
Ventricular premature contractionVentricular premature contraction
prolonged QRS due to volume conductionprolonged QRS due to volume conduction
High voltage as one voltage depolarises High voltage as one voltage depolarises before anotherbefore another
Inverted t waveInverted t wave
Ventricular fibrillationVentricular fibrillation Contraction of ventricular muscle mass Contraction of ventricular muscle mass
without coordination and at a high ratewithout coordination and at a high rate Some of muscle fibres contract at any Some of muscle fibres contract at any
given time and others relax so heart is given time and others relax so heart is neither in systole nor diastoleneither in systole nor diastole
Caused by reentry, facilitated by:Caused by reentry, facilitated by:
Long pathway – dilated heartLong pathway – dilated heart
Decreaesd conduction speed: high K+, Decreaesd conduction speed: high K+, ischemia, purkinje blockischemia, purkinje block
Low refractory period: repeated stimulant/ Low refractory period: repeated stimulant/ epinephrineepinephrine
Thank youThank you
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