Heart Anatomy + ECG
Aaqid Akram MBChB (2013)
Clinical Education Fellow
L Subclavian Artery
Brachiocephalic Trunk
L Common Carotid Artery
Superior Vena Cava
Arch of the Aorta
Pulmonary Artery
L Atrium
L Pulmonary Vein
R Atrium
Aortic Valve (Semilunar)
Fossa Ovalis
Mitral Valve (Bicuspid)
Chordae Tendinae
L Ventricle
Papillary Muscle
Pulmonary Valve
Tricuspid Valve
Endocardium
Inferior Vena Cava
R Ventricle
Myocardium
Septum
Ligamentum Arteriosum
Circumflex Artery
L Anterior Descending
Artery
R Coronary Artery
Cardiac Cycle
Introduction
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Wash Hands
Introduce yourself
Confirm patient + ALLERGY STATUS
Explain investigation to patient
Gain verbal consent
Offer chaperone (Chest will be exposed)
– If opposite sex you require a chaperone for your
own safety
The ECG Machine
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Power (plugged/battery)
Demographics
Paper
All leads intact
Stickers available
Scale – vertical axis
(0.1mV = 1mm = 1 small
square)
Placing Stickers
There’s only 10 leads….
How can it be a 12 lead ECG?
Interpreting an ECG
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Demographics
Obvious abnormality
Rate
Rhythm
Axis
P wave
PR Interval
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QRS Complex
ST segment
T wave
Summary
Rate
• 1500 small squares (0.04 seconds) = 60s
• No of small squares between R-R = x
• 1500/x = ventricular rate per minute
• If normal calibration  rhythm strip = 50 large
squares (0.2seconds) = 10 seconds
• Count QRS complexes on rhythm strip
• Multiply by 6 = ventricular rate per minute
Rhythm
• Sinus = p wave before every QRS Complex
• Regular = QRS complexes equidistant
– Mark 3 R-R points on the edge of a paper
– Move to next three complexes
– Do the marks on the paper correlate to the R
waves?
Axis
P
Wave
T
Wave
P wave
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Atrial depolarisation (Sino Atrial Node)
2-3 mm high
0.06 – 0.12 seconds duration
Usually positive deflection throughout ECG
Peaked/enlarged = atrial hypertrophy
Inverted = retrograde/reverse conduction
Absent = conduction by route other than SA
PR Interval
• Impulse from atria to AV Node, Bundle of His,
bundle branches
• 0.12 – 0.2 seconds duration
• Short = impulse did not originate from SA
• Long = AV Block
1st Degree Heart Block
1st Degree:
– QRS complex after every P wave
– Prolonged PR Interval
– No Rx necessary unless symptomatic
2nd Degree Heart Block
Mobitz Type 1 (Wenckebach):
– Each successive impulse from SA node delayed
slightly longer than previous impulse
– A QRS complex is dropped
– Cycle repeats
2nd Degree Heart Block
Mobitz Type 2:
– Occasional SA impulses fail to cause ventricular
depolarisation
– Regular P waves, but some dropped QRS
complexes
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2:1 Heart block
3rd Degree Heart Block
• Complete Heart Block:
– Impulses from atria cannot pass the AV node
– Atria depolarise independently to ventricles
– Life threatening
QRS Complex
• Deep wide Q waves may suggest old infarct
• Total duration <0.12 seconds
• >0.12 seconds = ventricular conduction delay
Bundle Branch Block
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Bundle branch fails to conduct impulses
Ventricles contract at slightly different times
Block further down the bundle = hemiblock
Cell-cell conduction slower than via
specialised pathway therefore prolonged
depolarisation
• New Left Bundle Branch Block = ACS
QT Interval
• Time from ventricular depolarisation to
ventricular repolarisation
• Varies according to heart rate
• QTc = corrected QT interval to 60bpm
• Males <450 ms / Females <470 ms
• Prolonged QT interval increases risk of life
threatening arrhythmias
Torsades de Pointes
Drugs affecting QT Interval
Drug
Type
Amiodarone
Antiarrhytmic
Amitriptylline
Antidepressant
Chlorpromazine
Antipsychotic/antiemetic
Clarithromycin
Antibiotic
Droperidol
Sedative/antiemetic
Erythromycin
Antibiotic
Fluoxetine
Antidepressant
Haloperidol
Antipsychotic
Ketoconazole
Antifungal
Levofloxacin
Antibiotic
Methadone
Opiate agonist
Quinidine
Antiarrhythmic
Sertraline
Antidepressant
Sotalol
Antiarrhythmic
Sumatriptan
Anti migraine
ST Segment
• Segment affected if acute ischaemia/infarction
• Elevation = >1mm
• Depression = >0.5mm
T Wave
• Ventricular repolarisation
• Usually upright deflection
• Tented T waves = hyperkalaemia/myocardial
injury
• Inverted T wave = ischaemia
• Camel Hump = hidden P/U wave
Summary
• Present all positive findings and important
negative findings.
• Advise on urgency of management.
Supraventricular Tachycardia
Atrial Flutter
Atrial Fibrillation
Ventricular Tachycardia
Ventricular Fibrillation
Asystole
Any Questions?
Thank You