2 What is an ECG?A recording of the electrical activity within the heart.
3 What you need to know Basic pathologies that can be picked up on ECG How to calculate heart rateShockable rhythmsHow to localise a pathology from an ECGBasic arrhythmias
4 ECG basicsCheck that this ECG is for the patient in front of you! (Name, DOB, patient number etc)Check which lead the rhythm strip is (usually lead II)At the bottom left is the 'paper speed' (25 mm/s on the horizontal axis) and the sensitivity of the ECG (10mm/mV).
5 ECG stripsThe closest we get to this classical picture is usually in lead II
6 Localising a pathology on ECG LCx is Left Circumflex artery, RCA is Right Coronary Artery, LAD is Left Anterior Descending ArteryII, III and aVF = Postero-inferior heart, supplied by the RCA (ignore the LCx bit on there, it doesn’t matter at this level)I, aVL, V5 and V6 = Left lateral heart, supplied by the LCxV1, V2, V3 and V4 = Anterior and anteroseptal (V1 and V2) heart, supplied by the LAD
8 How to calculate heart rate Method 1: We always print off 10 second ECG strips, so count the number of QRS complexes, multiply this by 6 and you have the heart rate!Method 2: Count the number of large squares between each QRS complex, then divide 300 by this number (this method cannot be used for an irregular rhythm).NOTE: To calculate the heart rate using method 1 you must use the rhythm strip!
9 Arrhythmias on ECG Ventricular or atrial Too fast, too slow or irregularSinus rhythm, regularly regularNormal, tachycardic or bradycardicSinus rhythm, regularly irregularP-P interval varies by more than 10%.Irregularly irregularAtrial fibrillation (VF is effectively pulseless)Arrythmia = abnormalDysrhythmia = problematic
10 Sinus rhythmThis just means that every QRS complex is preceded by a P wave!Note: It does not necessarily mean that every P wave is followed by a QRS complex.
11 How to tell if a rhythm is regular? Check if the ECG printout tells you!Paper strip method
12 How to read an ECG (the official version) Step 1: RhythmStep 2: RateStep 3: Conduction (PQ,QRS,QT)Step 4: Heart axisStep 5: P wave morphologyStep 6: QRS morphologyStep 7: ST morphologyStep 7+1: Compare the current ECG with a previous one
13 What we need to read from an ECG Step 1: What jumps out at you? (VF, VT, irregularly irregular, gross morphological problems, ST elevation indicative of an NSTEMI etc)Step 2: RhythmStep 3: RateStep 4: Conduction (is there conduction?)Step 5: General morphology (is everything about the right size?)Step 6: Compare the current ECG with a previous one (this is less likely to come up in an OSCE, but could do in an exam)Conduction, heart axis and accurate morphology are less important for the basic level we are at, but I will cover them when I teach about heart blocks and when I teach about STEMI’s and NSTEMI’s
14 Normal ECG Rhythm: sinus Rate: 60-100 bpm PQ interval 120-200ms QRS width msHeart axis: between -30 and +90 degreesThe maximal height of the P wave is 2.5 mm in leads II and / or IIIThe p wave is positive in II and AVF, and biphasic in V1The p wave duration is usually shorter than 0.12 seconds (3 small squares)No pathological Q wavesNo left or right ventricular hypertrophyNormal R wave propagation. (R waves increase in amplitude from V1-V5)No ST elevation or depressionT waves should be concordant with the QRS complexThe ECG should not have changed from the previous ECG
19 ECG denotations.The letters "Q", "R" and "S" are used to describe the QRS complexQ: the first negative deflection after the p-wave. If the first deflection is not negative, the Q is absent.R: the positive deflectionS: the negative deflection after the R-waveSmall print letters (q, r, s) are used to describe deflections of small amplitude. For example: qRS = small q, tall R, deep S.R`: is used to describe a second R-wave.