BRADYDYSRHYTHMIAS

Question 1

DDX

Answer 1

RHYTHMS:

Sinus Bradycardia

SA Block

AV Block

CRITICAL CAUSES:

METABOLIC
Hyper K+
Hypothermia

SYSTEM
Cardiac Ischemia

DRUGS:
CCB
BB
Digoxin
Clonidine
EtOH
Opiates

Question 2

SINUS BRADYCARDIA

Answer 2

Normal sinus P waves and PR intervals

1:1 AV conduction

Atrial rate slower than 60 beats/min

Question 3

Second-Degree Mobitz I (Wenchenbach) AV Block

Answer 3

Progressive prolongation through AV node until atrial impulse is blocked
b. After dropped beat, AV conduction returns to normal
c. Conduction ratio can be fixed or variable

Question 4

Second-Degree Mobitz II AV Block

Answer 4

Constant PR interval with intermittent nonconducted atrial beats
b. QRS usually wide

PP interval should be constant. If non conducted P waves occur early in the rhythm with no constant PP interval, consider frequent PAC’s

If bundle branch block or bifascicular block is present, it favours the diagnosis of Mobitz II vs. Mobitz I.

Question 5

Third-Degree (Complete) AV Block

Answer 5

No AV conduction
b. Ventricular rate slower – paced by an escape pacemaker from AV OR infranodal conduction system
c. Block at the level of AV node, junctional escape rhythm occurs with a ventricular rate of 40 – 60 beats / min with a NARROW QRS COMPLEX
d. Infranodal block, ventricles driven by ventricular escape rhythm with a ventricular rate of < 40 beats / min with a WIDE QRS COMPLEX

Question 6

HYPERKALEMIA

Answer 6

Peaked T Waves
Widening of the QRS
Prolonged QRS
Prolonged PR
Flattening and eventual loss of the Ps
Tachycardias, Bradys, AV blocks, sinus pause,

Any slow rhythm can be Hyper K+

Hyper K+ can mimic a STEMI!!!!

Look for peaked Ts, wide QRS, lack of Ps

Question 7

BETA BLOCKER / CALCIUM CHANNEL BLOCKER TOXICITY

Answer 7

• Sinus bradycardia
• 1st degree, 2nd degree and 3rd degree AV block
• Junctional bradycardia
• Ventricular bradycardia

A prolonged PR interval is an early sign of beta-blocker or calcium-channel blocker toxicity — even in the absence of significant bradycardia.

Question 8

DIGOXIN TOXICITY

Answer 8

• Supraventricular tachycardia (due to increased automaticity)
• Slow ventricular response (due to decreased AV conduction)
• Frequent PVCs (the most common abnormality), including ventricular bigeminy and trigeminy
• Sinus bradycardia
• Slow Atrial Fibrillation
• Any type of AV block (1st degree, 2nd degree & 3rd degree)
• Regularised AF = AF with complete heart block and a junctional or ventricular escape rhythm
• Ventricular tachycardia, including polymorphic and bidirectional VT

Question 9

HYPOTHERMIA

Answer 9

1. Bradyarrythmias: sinus brady, afib with slow ventricular response, slow junctional rhythm, varying AV block
2. Osborne Waves (J waves): positive deflection at the J point, amplitude proportional to degree of hypothermia
3. Prolonged PR, QRS, and QT intervals
4. Shivering Artifact: fuzziness at the ECG baseline
5. Ventricular Ectopics
6. Cardiac arrest due to VT, AF or asystole