Download - READING ECG
Anatomy Revisited RCA
› right ventricle› inferior wall of LV› posterior wall of LV (75%)
› SA Node (>80%)› AV Node (60%)
LCA› septal wall of LV› anterior wall of LV› lateral wall of LV› posterior wall of LV (10%)
ECG Graph Paper
Horizontal axis - time 1 small box = 1 mm = 0.04 sec.
o Every 5 lines (boxes) are bolded
Vertical axis - voltage1 small box = 1 mm = 0.1 mV
Paper Speed - 25 mm/sec standard
Calibration of Voltage is Automatic
Both Speed and voltage calibration can be changed on most devices
Paper Speed & Calibration
ECG Waves and Intervals P wave : atrial
contraction; QRS complex :
ventricular contraction;
T wave : ventricular repolarization.
PR interval : time from onset of atrial activation to onset of ventricular activation.
QRS duration : duration of ventricular activation.
PR interval = 0.2 sec (5 small boxes)QRS interval = < 0.12 sec (3 small boxes)QT interval = 0.42 sec (10 small boxes)
Normal ECG
RHYTHM Measure R-R intervals across strip Should find regular distance between R waves Classification• Regular• Irregular
SEE R to R INTERVALR R R
Normal heart rhythm has consistent R-R interval.Mild variations due to breathing also normal
Triplicate method›300-150-100-75-60-50
R-R method›divide 300 by # of large squares between consecutive R waves
6 Second method›multiply # of R waves in a 6 second strip by 10
Measuring heart rate
PR interval Time between onset of atrial depolarisation and the onset of ventricular depolarisation
N: 3-5 small squares (0.12-0.20 sec)
Abnormalities of conduction system
prolonged PR interval
QRS complex
Ventricular depolarisation N: ≤ 2 ½ small squares (0.10 sec)
Delays in ventricular depolarisation
Abnormally wide QRS complex
HYPERACUTE PHASE
Tall T waves :• more then 50% of preceding R wave•Become more symmetrical and pointed •Usually finding not recorded because they have typically resolve by the time the patients seeks Medical assistamce – within minutes
Usually last within minutes
DYNAMIC ECG CHANGES DURING ACUTE MYOCARDIAL INFARCTION
1. Occurs a few hours later2. Development of significant
Pathological Q wave3. Q wave when happened with
or combine with T wave change and ST elevation is consider Acute MI
1. Presence of T wave inversion
2. Suggestive of presence of ischemia
3. T wave inversion may presence before ST segment elevation or may occur at the same time
1. T wave regain normal shape2. ST segment return to baseline3. Q wave remain as evidence that
infarction occurred4. Establishing time of infarction
impossible5. Only possible to recognize the
presence of previous MI
Lateral infarctionLateral infarction
I II III aVR aVL aVF V1 V2 V3 V4 V5 V6
Left circumflexcoronary artery
1. During angina attack the ST segment be temporarily depressed
2. The ST segment will depressed when the infarct does not extend the full thickness of the wall
3. Subendocardial Infarction or injury is identify by flat ST segment depression which may be horizontal or down sloping
Ventricular Tachycardia
The main features of this wide QRS tachycardia that indicate its ventricular origin is the condordance of QRS's in the precordial leads (all QRS's are in the same direction). No P waves.
Unifocal PVCs (ventricular ectopic)
Ventricular extrasystole.QRS wide and abnormal, identical. T abnormal.
Atrial Pacemaker Rhythm
Pacemaker spikes are seen before each QRS complex and initiate a tiny P wave.
SUPRAVENTRICULAR TACHYCARDIA
Characteristic: Absent P wave Rate: 150-300 beats per minute Regular rhythm