SAQ 464 – Cardiology – unstable broad complex tachycardia requiring cardioversion

Cardiology – unstable broad complex tachycardia requiring cardioversion.

a. ECG findings and diagnosis

• Regular broad-complex tachycardia.
• Rate approximately 170-180/min or faster.
• LBBB morphology consistent with right ventricular origin.
• No clear P waves or AV dissociation may be present depending on the strip.
• Haemodynamic compromise with BP 90/50 mmHg makes this an unstable tachyarrhythmia.
• Unifying diagnosis: ventricular tachycardia in suspected ARVC/arrhythmogenic right ventricular cardiomyopathy.

b. Synchronized cardioversion

• Call for senior ED, anaesthetic/resuscitation help; move to resus, attach defibrillator, ECG, BP and SpO2 monitoring.
• Explain briefly and obtain consent if time permits while preparing for immediate synchronized cardioversion.
• Give high-flow oxygen if needed, establish IV access and prepare fluids/vasopressors for peri-sedation hypotension.
• Apply pads and select synchronized biphasic shock, commonly 100-200 J for broad-complex tachycardia according to local protocol.
• Provide titrated procedural sedation/analgesia, for example fentanyl 0.5-1 microgram/kg IV plus small aliquots of propofol 0.5-1 mg/kg IV, or ketamine 0.5-1 mg/kg IV if hypotension is a concern.
• Deliver the synchronized shock, reassess rhythm and perfusion immediately, and escalate energy/repeat synchronized shocks if unsuccessful.
• After conversion, continue monitoring, correct electrolytes, avoid AV-nodal-only agents if pre-excited AF is a concern, and arrange urgent cardiology/ICU review.