Tachydysrhythmias Flashcards
What is tachycardia?
Resting heart rate of > 100 bpm in adults
General Approach to tachycardia: Is the patient stable or unstable?
- Monitor in high acuity area with continuous cardiac and vitals monitoring
- Assess responsiveness and pulse. If pulseless, begin CPR
- ABCs, set IV plug
- Assess for clinical features of UNSTABLE patient: Chest pain, Hypotension, AMS, Pulmonary edema, Shock (CHAPS)
- 12 lead ECG if patient is stable
Ddx for:
Narrow, regular complex tachycardia
- Sinus tachycardia
- Supraventricular tachycardia
- Atrial flutter with fixed conduction
- Atrial tachycardia
Ddx for:
Narrow, irregular complex tachycardia
- Atrial fibrillation (**most common)
- Atrial flutter with varying conduction
- Multifocal atrial tachycardia
Ddx for:
Wide, regular complex tachycardia
- Monomorphic ventricular tachycardia
- Metabolic/Drug
- SVT with antidromic conduction through an accessory pathway eg WPW
- SVT with abberancy/bundle branch block
- Any narrow, regular tachycardia with a bundle branch block
Pathophysiology of Atrial Flutter
An atrial re-entrant rhythm that overrides the sinus node leading to atrial depolarisation at a rate of 300/min as seen as flutter waves in ECG resulting in saw toothed baseline.
Due AV nodal refractory period, conduction to the ventricles (ventricular depolarisation) occurs at regular intervals in 2:1 or 3:1 ratio, resulting in a ventricular rate of 150 or 100 beats per minute.
Sinus tachycardia: Key Features
- Narrow, regular complex tachycardia
- Normal-looking P wave before every QRS complex
Sinus tachycardia: Causes
- Physiological e.g. exercise, infection, pyrexia, dehydration
- Emotional: Pain, Anxiety
- Emergencies: acidosis, pulmonary embolism, cardiac tamponade, significant bleeding with hypovolaemia
- Hyperthyroidism
- Medications
Sinus tachycardia: Treatment
Treat underlying cause
Atrial Flutter: Key Features
*narrow, regular or irregular complex tachycardia
- Saw toothed baseline flutter waves in some of the leads
- Lack of TP segment in the leads with a saw toothed pattern
- Ventricular rate typically about 100 or 150 bpm
- Rhythm is regular in cases with fixed conduction ratio
- If the conduction ratio varies, then the rhythm is irregular
Pathophysiology of Atrial Fibrillation
Many ectopic atrial foci depolarising almost simultaneously (fibrillating), hence ventricular depolarisation occurs irregularly.
- Reentrant Circuits: The disorganized impulses lead to the formation of reentrant circuits within the atria. These circuits continuously stimulate different parts of the atrial myocardium, causing the atria to fibrillate (quiver) rather than contract effectively.
- Impaired Conduction: The rapid, irregular impulses overwhelm the atrioventricular (AV) node, which tries to regulate the transmission of impulses to the ventricles but often cannot keep up. This results in an irregular ventricular response rate.
Atrial Fibrillation: Key Features
- Irregularly irregular rhythm
- Fine or coarse fibrillatory waves may be present. Coarse waves may mimic P waves
- Absence of P waves before every QRS complex
- Absence of isoelectric baseline
Atrial Flutter/Fibrillation: Treatment
- Treat reversible causes - infection, AMI, thyrotoxicosis, alcohol, acute PE, myocarditis
- Rate control
a. No HF
- Diltiazem
- Verapamil
- Esmolol
- Metoprolol
- Procainamide
b. HFpEF
- CCB or BB
c. HFrEF
- Amiodarone
- Digoxin - Start anticoagulants if patient’s CHA2DS2VASc is 2 or more
- valvular AF: warfarin
- non-valvular AF: DOAC
FOR chronic control, consider +
4. Rhythm control
- Amiodarone
- Transesophageal echocardiogram (TEE) TRO atrial thrombi, anticoagulate if present
- Synchronised electrical cardioversion
CHA2DS2VASc score
Congestive heart failure
Hypertension
Age >/= 75 years
Diabetes mellitus
Stroke/TIA/thromboembolism
Vascular disease (prior MI, PAD, aortic plaque)
Age 65-74years
Sex category: Female
Supraventricular tachycardia
It refers to all atrioventricular tachydysrhythmias that occurs above the ventricles (Bundle of His) and the types of SVT depends on the source of the electrical signal
- AVNRT, AVRT, atrial flutter/fibrillation, atrial tachycardia
Most common cause of SVT
Atrioventricular nodal re-entrant tachycardia
Pathophysiology of AVNRT
Re-entrant circuit is formed
Re-entry point of electrical impulse is back through the AV node and into the atria again
Pathophysiology of AVRT
Re-entrant circuit is formed
Re-entry point of electrical impulse is through an accessory pathway (additional electrical pathway between atrium and ventricle)
- Conduction can be orthodromic or antidromic
Orthodromic AVRT
Conduction of electrical impulse is from atrium to ventricles through AV node and then some impulses will reenter the atrium through the accessory pathway
Antidromic AVRT
Conduction of some electrical impulse goes from atrium to ventricles through the accessory pathway then will reenter the atrium through AV node
SVT: Key features
- Narrow, regular complex tachycardia
- Absence of P wave before every QRS complex
Stable SVT: Treatment
- Non-pharmacological manoeuvre
- Modified valsava manoeuvre
- Carotid sinus massage - Pharmacological treatment
- IV adenosine* (T1/2 is 8s, blocks AV node)
- IV diltiazem
- IV verapamil
Unstable SVT: Treatment
Synchronised electrical cardioversion
Unstable Atrial flutter/Afib: Treatment
Synchronised cardioversion
- Atrial flutter: 50J
- Atrial fibrillation: 100J
Ventricular tachycardia
A regular, wide complex tachycardia that is sustained for >/= 30 seconds
- QRS complex > 120ms wide
- Rate > 120bpm
Ventricular tachycardia: Key features
CABAM
Concordance
- When all the precordial leads point in the same direction
Axis
- Northwest Axis
- QRS positive in aVR
- Negative in I and aVF
Beats: Fusion and capture beats
AV dissociation
- A and V don’t talk
*most common feature
Morphology
- Deviations from normal BBB morphology suggests VT
Stable ventricular tachycardia: Treatment
- IV amiodarone
- IV lignocaine
- IV procainamide
- If pharmaco fails: elective synchronised cardioversion (in ED if unstable)
Pulseless VT: Treatment
Start CPR (ACLS)
Torsades de pointes: Treatment
- Correct electrolyte abnormalities causing prolonged QT especially hypoMg and hypoK.
- IV MgSO4 1-2g over 60-90s then 1-2g/h infusion.
- Consider overdrive pacing under the care of a cardiologist.
- Halt any drugs which may cause QT prolongation. (Eg. Procainamide, amiodarone, sotalol, TCAs, macrolides.)
Polymorphic VT: Treatment
- Amiodarone for chemical cardioversion.
- Look for evidence of ischemia.
- Look out for QTc>500ms or ‘R on T’ phenomenon suggesting impending TdP development.
Most common arrythmia in children
SVT
What is Wolff-parkinson white syndrome?
Subtype of SVT
- presence of extra accessory pathway (aka bundle of Kent) outside of AV node and bundle of His
- allows electrical conduction to escape from atrium to ventricle EARLIER than expected
- causing pre-excitation of ventricles
Key features of WPW syndrome
- Regular broad complex tachycardia
- Short PR interval (no proper isoelectric line between P wave and QRS)
- Delta wave (slurred upstroke at the beginning of QRS)
Must do investigation for first presentation of AF
Thyroid function tests
