ECGs

Introduction It is important to have a good structure for analysing and subsequently reporting an ECG. When reporting an ECG, you should use the same structured approach every time. This is particularly important when first learning about ECGs. A structured approach allows you to systematically assess the ECG in order and not forget any key elements. Once you improve, you’ll start to develop pattern recognition for classic ECG features.  We propose the following structure for analysing and reporting an ECG: Confirm correct patient details Rate Rhythm Cardiac axis P waves, Q waves & QRS complexes ST segments & T waves  QT interval Putting it all together This

Introduction It is important we analyse each aspect of the ECG morphology including P wave, QRS complex, ST segment and T wave. Abnormalities of the P wave, QRS complex, ST segment and T wave can tell us a lot about the patient. Analysing these parts of the ECG should always be taken in context of the rate, rhythm and clinical status of the patient.  Certain changes to the ECG morphology are classical of an underlying pathology. For example, ST elevation is the characteristic feature of an acute ST-elevation myocardial infarction (STEMI). Other changes are non-specific and can be suggestive of multiple pathologies. For

Introduction It is important we analyse each aspect of the ECG morphology including P wave, QRS complex, ST segment and T wave. Abnormalities of the P wave, QRS complex, ST segment and T wave can tell us a lot about the patient. Analysing these parts of the ECG should always be taken in context of the rate, rhythm and clinical status of the patient.  Certain changes to the ECG morphology are classical of an underlying pathology. For example, ST elevation is the characteristic feature of an acute ST-elevation myocardial infarction (STEMI). Other changes are non-specific and can be suggestive of multiple pathologies. For

Introduction Tachycardia refers to an abnormally fast heart rate. Tachycardia is usually defined as an abnormally fast heart rate greater than 100 bpm. We refer to all the abnormally fast heart rhythms as tachyarrhythmias. When a tachyarrhythmia occurs intermittently, we call it paroxysmal. Tachyarrhythmias may develop due to an ectopic foci of electrical activity within the atria, atrioventricular node (AVN) or ventricles. The aetiology of these ectopic foci can get quite complex, but is broadly due to problems with impulse conduction (i.e. transmission of electrical activity) or impulse formation (i.e. generation of electrical activity). Impulse conduction problems: caused by conduction blocks (discussed in our Bradycardia notes) and formation of reentrant

Introduction Bradycardia refers to an abnormally slow heart rate. Bradycardia is usually defined an abnormally slow heart rate less than 60 bpm. We refer to all the abnormally slow heart rhythms as bradyarrhythmias. Bradyarrhythmias may develop due to a variety of intrinsic or extrinsic factors. Intrinsic Within the heart, a slow rate may occur due to failure to initiate, or transmit, electrical activity. Failure to initiate electrical activity can cause another part of the heart to take over as the primary pacemaker. This is called an escape rhythm. For example, if the sinoatrial note (SAN) fails to undergo spontaneous depolarisation the atrioventricular node (AVN) may initiate

Introduction Rate and rhythm are the first things to assess when analysing an ECG. The rate refers to the frequency of electrical activity. It correlates with muscular contraction and therefore heart rate. Normal electrical activity in the absence of contraction is termed ‘pulseless electrical activity’. This rhythm is not compatible with life and can be seen in cardiac arrest. The rhythm refers to the area of the heart that is controlling electrical activity. In other words, the part of the heart that is initiating electrical activity, which then spreads throughout the heart. Due to spontaneous depolarisation, different parts of the heart can initiate electrical

Introduction Conduction through the heart is dependent on pacemaker cells, which are organised into key structures. The heart is a dual pump that sits at the centre of the cardiovascular system. It is composed of both contractile cells and autorhythmic cells (also known as pacemaker cells). Approximately 1% of cardiac tissue is composed pacemaker cells, which are organised into key structures and can undergo spontaneous depolarisation. Depolarisation refers to the electrical changes that occur within a muscle to allow it to contract. The heart is essentially one big muscle that can contract by itself. We can detect these electrical changes, which are associated with