ECG

ECG

1. Main Deflections of ECG

   • QRS Complex represents ventricular depolarisation. Abnormally wide if greater than 3 squares. Q waves in some leads are sometimes abnormal
   • PR Interval is time taken for electrical activity to pass through AV Node. Return to isoelectric line at the end of P wave. Abnormal if greater than 5 small squares or less than 2-3 squares
   • P Wave represents Atrial depolarisation. Should be no higher than 3mm. Abnormal if inverted, broad, notched, tall and peaked.
   • ST Segment occurs in a period of unchanged polarity. It should return to isoelectric line. Occurs in interval of unchanged polarity. Abnormal if elevated or depressed
   • T wave represents ventricular repolarisation. Points same way as QRS should be no taller than 5mm. Abnormal if tall , peaked, flat or intverted
   • U wave is not always seen. Repolarisation of bundle branches
   • QT Interval is the complex relationship between QT interval and heart rate. Long QT can cause sudden death, from VT. Causes are usually heredity or certain drug therapies.
   • Isoelectric Line - Where the recording returns to during periods of no electrical movement

2. Techniques in monitoring: Choose leads which give a good picture with easy to see p wave

   • Prepare skin well
   • Attach new electrodes
   • Poor picture: Change lead view, change amplitude

3. Arrhythmias

   • Arrhythmia is a disturbance of your heart’s usual electrical rhythm. Arrhythmias can happen at any age and mostly they aren’t serious.
   • •Sinus tachycardia. This is when your heartbeat is still regular, but faster than it should be. It’s normal in certain situations, such as during exercise or if you have a fever, but may also occur at other times for no obvious reason. Conditions such as an overactive thyroid gland or anaemia may cause sinus tachycardia. Although normal heart rate can reach 100 beats per minute (bpm) when you’re at rest, you may feel some discomfort if the rate is faster than you’re used to for a particular level of activity.
   • •Sinus bradycardia. This is when your heartbeat is still regular, but slower than usual (fewer than 60 bpm). Bradycardia is common in athletes but can also occur if you’re exposed to the cold and have a low body temperature or are resting or sleeping. If your heart rate is extremely slow, you may feel dizzy or faint.
   • •Ectopic beats. These are extra heartbeats but they don’t result in any blood being pumped from your heart. You feel an ectopic heartbeat as a missed beat and the next beat is then more powerful – you feel this as a thump. You may get ectopic beats every few beats or even every beat – this results in a slow, thumping rhythm (bigeminy). Ectopic beats are very common and rarely mean that you have a heart problem. They are most noticeable when you’re resting
   • Symptoms: •palpitations •dizziness •fainting or collapsing •breathlessness •chest pain •tiredness
   • Treatments Include: to slow down your heart rate, such as beta-blockers, or antiarrhythmic medicines, such as amiodarone and flecainide. Pacemaker may be advised. Vagal Manoeuvres, Surgery