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
Narrow Complex Tachycardia
Last updated 3rd December 2020
Last updated on 26th July 2013 by Calum Murray
First classify as regular (see below) or irregular (usually AF)
Regular Narrow Complex Tachycardias
- Sinus Tachycardia
- AV Nodal Re-entrant Tachycardia
- Atrial Flutter
- Accessory Pathway Tachycardia eg WPW
- Atrial Tachycardia
Sinus Tachycardia
- P waves have normal morphology, are upright in lead II and precede every QRS complex with VR up to 150/min – shown below
- Causes are hypotension, hypovolaemia, hypoxia, fever, anxiety, pain, thyrotoxicosis.
- The key is to find and treat the cause.
AV Nodal Reentrant Tachycardia (AVNRT)
- Often referred to as Paroxysmal SVT though it is merely one of several paroxysmal SVTs.
- In the common form of AVNRT (90%) the P waves and QRS usually coincide so that you cannot see the P wave separately. Usually conducts 1:1 with ventricular rate 150-200/min – shown below
- In the uncommon form of AVNRT (10%), the P wave is visible after the corresponding QRS, giving QRS-P-T complex – shown below.
- May cardiovert with carotid sinus massage (CSM) or valsalva manoeuvre – remember to have the ECG running.
- If CSM fails, try adenosine or verapamil with ECG running.
Atrial Flutter
- Flutter waves usually 300/min (range 250-350/min), but not always obvious – the example shown is the rhythm strip of the ECG below
- Best to consider that a narrow complex at 150/min is atrial flutter with 2:1 block until proven otherwise.
- CSM and adenosine may cause transient AV block exposing flutter waves – remember to have the ECG running.
- Usually best to correct any non cardiac causes e.g. infection, hypoxia, hypokalaemia before attempting cardioversion.
- Unlike AF, ventricular rate responds less well to digoxin though digoxin still appropriate if heart failure.
- If you know flutter present for <24hours and structurally normal heart, Rx amiodarone 300mg IV, followed by DC shock starting at 50J, then 100J, 150J and 200J if fails to cardiovert.
- Amiodarone should be given by central line (or PIC line) whenever possible. It should never be given into a small vein on the back of the hand. A large antecubital vein is permissible for the first 300mg in an emergency.
- If you don’t know when flutter began and haven’t had a cardiac assessment then rate control and anticoagulate with LMWH.
- If flutter present >24 hrs could consider cardioversion after TOE or anticoagulate, control rate with ß-blocker or verapamil & defer cardioversion for 4 weeks.
Atrial Tachycardia
- Much less common than AVNRT
- P waves usually visible and have morphology different from P waves in sinus rhythm eg inverted in lead II (see below)
- May conduct 1:1 with VR 120-200/min, or exhibit AV block
- AV block classically seen as digoxin toxic rhythm
- CSM and adenosine may cause transient AV block exposing ectopic focus.
- Consider cardioversion if compromIsed.
- Beta-blocker most likely to help control heart rate.
- Thromboprophylaxis not required
Accessory Pathway Tachycardia eg WPW
- An accessory pathway is an abnormal tract between atria and ventricles capable of conducting impulses in either direction
- ECG in sinus rhythm classically shows a short PR interval and a delta wave aka Wolff-Parkinson-White pattern – shown below
- The commonest WPW tachy has narrow complex and is indistinguishable from AV nodal re-entrant tachy – impulse goes down AV node and back up the accessory pathway.
- WPW can also cause broad complex tachy, usually fast AF with VR up to 250/min, if conducts down accessory pathway and back up AV node – shown below
- Catheter ablation is Rx of choice in symptomatic patients
- Drug of choice is Flecainide or Amiodarone. Verapamil and digoxin shorten refractory period of accessory pathway and may precipitate VF, so avoid if WPW previously diagnosed.
Adenosine
- Acts on AV node by binding to adenosine receptors in the conducting tissue, decreasing HR.
- Will usually cardiovert patients with AVNRT.
- Avoid in asthma, severe COPD or if taking Dipyridamole
- Always warn the patient they may feel transiently breathless, lightheaded and have chest tightness.
- Give 6mg as a rapid IV bolus followed by a saline flush. If ineffective give a 2nd bolus of 12mg,
- If still ineffective consider increase to 18mg, providing the previous boluses were well tolerated.
- Always cardiovert with continuous cardiac monitoring.
Verapamil
- Acts on AV node
- Useful alternative for patients who cannot take adenosine (but avoid if known to have WPW).
- Rx 5mg IV over 5min, repeated if necessary after 5min.
- Avoid if broad complex tachycardia as may convert VT to asystole
- Avoid if on ß-blocker as may become profoundly bradycardic or hypotensive