In this section : Cardiac
Deactivation of Implantable Cardioverter Defibrillator
Extravasation of IV Amiodarone
Anticoagulation for AF, DVT and PE
Patients Returning from Interventional Cardiac Procedure
Cardiology Referrals
STEMI Thrombolysis Protocol
STEMI
Hypertensive Emergencies
Rate Control in AF
Heart Failure
Aortic Dissection
Non ST Elevation MI (NSTEMI)
Suspected Acute Coronary Syndrome
Pericardiocentesis
Pacemakers
Indications for Echocardiography
Bradycardia
Narrow Complex Tachycardia
Anti-Platelet Therapy in Coronary Heart Disease
Management of Acute AF
Rhythm Control in AF
Atrial Fibrillation
Hypertension
Ventricular Tachycardia
Cardiogenic Shock Complicating Acute Coronary Syndrome
Telemetry
Bradycardia
Last updated 6th March 2024
Consider referral to Cardiology for all symptomatic patients
Sinus Bradycardia
- By definition sinus rhythm <60 per minute.
- Common in athletes and young healthy adults
- Pathological causes include inferior MI, drugs esp betablockers, digoxin, and rate lowering calcium antagonists, hypothyroidism, raised intracranial pressure and sick sinus syndrome.
- Does not require treatment unless symptomatic.
Sick Sinus Syndrome
- Usually results from idiopathic fibrosis of the sinoatrial node
- Characterised by sinus bradycardia and long pauses between complexes on the ECG. These may be an exact multiple of the basic sinus interval (sino-atrial block – first trace) or not (sinus arrest – second trace).
- Long pauses may be followed by escape rhythms eg atrial flutter or fibrillation, so called bradycardia-tachycardia syndrome
- Permanent pacing recommended for symptomatic pauses or asymptomatic pauses > 3 seconds (4 seconds in AF).
First Degree AV Block
- Simple prolongation of PR interval > 0.2 seconds (5 small squares).
- QRS complex follows each P wave and PR interval remains constant
- Does not require treatment but needs further investigation if there are symptoms of collapse/lightheadedness
Second Degree AV Block – Mobitz Type 1 (Wenckebach)
- Progressive PR prolongation is followed by a dropped beat.
- Commonly seen overnight in normal people.
- Permanent pacing should occasionally be considered when symptomatic.
Second Degree AV Block – Mobitz Type 2
- Describes dropped beat that is not preceded by PR prolongation.
- Temporary pacing usually required for Mobitz 2 AV block post anterior MI.
- Permanent pacing usually required for Mobitz type 2 chronic AV block.
- In the example shown below every other P wave is not conducted. Also known as 2:1 AV block. Treat as above.
Third Block or Complete AV Block
- Classically (but not typically) presents as Stokes-Adams attack ie transient loss of consciousness without warning.
- ECG shows complete dissociation between P waves (arrowed) & QRS complexes.
- Carries a greater risk of asystole if complexes broad.
- Temporary pacemaker indicated for complete heart block post anterior MI, or inferior MI if symptomatic.
- Permanent pacemaker indicated for most chronic complete heart block.
Bifascicular Block
- Combination of RBBB and left (or right) axis deviation.
- Can indicate advanced conducting system disease.
- Temporary pacemaker indicated for new bifascicular block in anterior MI.
- Permanent pacemaker should be considered for chronic bifascicular block with symptoms eg syncope.
Trifascicular Block
-
- Combination of RBBB, left axis deviation & first degree heart block
- Indicates advanced conducting system disease.
Bradyarrhythmias and Pacemakers
- Indications for temporary & permanent pacemaker as for bifascicular block.
Hyperkalaemia
- The usual sequence of ECG changes is tall T waves, then loss of P waves, broadening of QRS complex, bradycardia and asystole. VF and VT have also been described but are less common.
- The clue that hyperkalaemia might be the cause of bradycardia is therefore a very slow heart rate with broad QRS and no visible P waves
- Rx Calcium gluconate 10% 30ml IV over 2-3 mins, repeating every 5 mins until QRS complex narrows
Junctional Bradycardia
- Same QRS morphology as in sinus rhythm; P waves if present may be inverted and buried in or come after the QRS complex.
- Commonly due to drugs eg digoxin, betablocker
- Rx Atropine if symptomatic. Might have to pace if escape rhythm in sino-atrial disease
Other Indications for Temporary Pacing
- Overdrive pacing for drug resistant ventricular tachycardia.
- Recurrent Torsade de Pointes unresponsive to magnesium.
When To Use Drugs
- Atropine 0.3 to 0.6mg IV bolus, repeated as necessary indicated as temporary measure for any patient with symptomatic bradycardia.
- Isoprenaline infusion for symptomatic bradycardia unresponsive to atropine, if delay occurs initiating transvenous or transcutaneous temporary pacing.
- Dose of isoprenaline is 2mg isoprenaline sulphate in 500ml 5% dextrose to give a concentration of 4 microgram/ml. Start infusion at 15ml/hour (1 microgram/min) titrations up in steps of 1 microgram/min at intervals of 2-3 minutes until a satisfactory heart rate achieved or adverse effects such as hypotension or ventricular arrhythmia occur. Usual max infusion rate is 150ml/hour (10 microgram/min) with cardiology input. Monitor on telemetry and discontinue by weaning slowly.
Links
- Bradyarrhythmias and pacemakers – BMJ 2018;360:k642 For full text, click on link and select ‘Login via OpenAthens’ then use your Knowledge Network Login