ECG INTERPRETATION APPROACH NURSING JUNIOR STAFF PHYSICIAN SIMPLIFIED
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The document describes the electrocardiogram (ECG) process, detailing how it measures the heart's electrical activity through specific waves and leads. It explains the normal and abnormal cardiac axes, including causes of deviations, and provides context for interpreting the ECG based on paper speeds and rhythm calculations. Key factors for accurate ECG reading, such as patient identification and calibration, are also emphasized.
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ECG INTERPRETATION APPROACH NURSING JUNIOR STAFF PHYSICIAN SIMPLIFIED
- 1. EDITED BY MOHAMED KHARABISH ICU SPECIALIST
- 4. An electrocardiogram — abbreviated as EKG or ECG — measures the electrical activity of the heartbeat. With each beat, an electrical impulse (or “wave”) travels through the heart. This electrical wave causes the muscle to squeeze and pump blood from the heart. A normal heartbeat on ECG will show the rate and rhythm of the contractions in the upper and lower chambers. The right and left atria or upper chambers make the first wave called a “P wave" — following a flat line when the electrical impulse goes to the bottom chambers or ventricles. The right and left bottom chambers make the next wave called a “QRS complex." The final wave, or “T wave,” represents electrical recovery or return to a resting state for the ventricles.
- 9. Limb leads There are six standard limbs leads, which are recorded from the electrodes that attached to the patients limbs. These leads look at the heart from the vertical plane. •II, III, aVF: inferior leads. Look at the inferior surface of the heart •I, aVL: lateral leads. Look at the left lateral surface of the heart •aVR: right arm lead. looks at the right atrium of the heart.
- 10. The lead connected to the right ankle is a neutral lead, like you would find in an electric plug. It is there to complete an electrical circuit and plays no role in the ECG itself.
- 15. NOTE: due to its location, aVR should always be negative (predominantly negative deflection in QRS complex). If it is positive it may suggest wrong lead placement. So doctor asked u to repeat aVR
- 17. OUR CLASSIC ICU ECG PAPER
- 35. Cardiac axis represents the sum of depolarisation vectors generated by individual cardiac myocytes. Clinically is is reflected by the ventricular axis, and interpretation relies on determining the relationship between the QRS axis and limb leads of the ECG (below diagram)
- 37. Since the left ventricle makes up most of the heart muscle under normal circumstances, normal cardiac axis is directed downward and slightly to the left: •Normal Axis = QRS axis between -30° and +90°. Abnormal axis deviation, indicating underlying pathology, is demonstrated by: •Left Axis Deviation = QRS axis less than -30°. •Right Axis Deviation = QRS axis greater than +90°. •Extreme Axis Deviation = QRS axis between -90° and 180° (AKA “Northwest Axis”).
- 39. Causes of Axis Deviation Right Axis Deviation •Right ventricular hypertrophy •Acute right ventricular strain, e.g. due to pulmonary embolism •Lateral STEMI •Chronic lung disease, e.g. COPD •Hyperkalaemia •Sodium-channel blockade, e.g. TCA poisoning •Wolff-Parkinson-White syndrome •Dextrocardia •Ventricular ectopy •Secundum ASD – rSR’ pattern •Normal paediatric ECG •Left posterior fascicular block – diagnosis of exclusion
- 40. Left Axis Deviation •Left ventricular hypertrophy •Left bundle branch block •Inferior MI •Ventricular pacing /ectopy •Wolff-Parkinson-White Syndrome •Primum ASD – rSR’ pattern •Left anterior fascicular block – diagnosis of exclusion •Horizontally orientated heart – short, squat patient
- 41. Extreme Axis Deviation •Ventricular rhythms – e.g.VT, AIVR, ventricular ectopy •Hyperkalaemia •Severe right ventricular hypertrophy
- 42. Understanding paper speeds •Paper output speed is the rate at which the ECG machine produces a trace •Standard output is 25mm per second •If a different paper speed is used, standard rate calculations will have to be modified appropriately
- 43. The standard paper speed is 25mm/sec: •1 SMALL square (1mm) = 0.04 sec (40ms) •5 SMALL squares (5mm) = 1 LARGE square = 0.2 sec (200ms) •5 LARGE squares = 1 second
- 45. At standard paper speed of 25mm/sec, the rhythm strip comprises of: •250 SMALL squares = 50 LARGE squares = 10 seconds Before calculating rate in beats per minute (bpm), we should understand that a rhythm strip recorded for 1 minute will therefore compromise: •1500 SMALL squares = 300 LARGE squares = 1 minute
- 47. Before beginning ECG interpretation, you should check the following details: •Confirm the name and date of birth of the patient matches the details on the ECG. •Check the date and time that the ECG was performed. •Check the calibration of the ECG (usually 25mm/s and 10mm/1mV).
- 48. What is a normal adult heart rate? •Normal: 60-100 bpm •Tachycardia: > 100 bpm •Bradycardia: < 60 bpm Regular heart rhythm W h a t i s a n o r m a l a d u l t h e a r t r a t e ?