DCAS Cardiac Emergencies (ACLS) 2 — Questions and Answers
Question 1: The 'Hs and Ts' of cardiac arrest represent potentially reversible causes. Which is an 'H'?
- Hypovolaemia (Correct answer)
- Thrombosis (pulmonary embolism)
- Tension pneumothorax
- Tamponade (cardiac)
Correct answer: Hypovolaemia
The Hs are: Hypovolaemia, Hypoxia, Hydrogen ion excess (acidosis), Hypo/hyperkalaemia, and Hypothermia. The Ts are: Tension pneumothorax, Tamponade, Toxins, and Thrombosis (PE or coronary).
Question 2: STEMI recognition on a 12-lead ECG requires ST elevation of at least:
- 1mm in two or more contiguous limb leads or 2mm in two or more contiguous precordial leads (Correct answer)
- 0.5mm in any lead
- 3mm in a single lead
- 5mm in the precordial leads only
Correct answer: 1mm in two or more contiguous limb leads or 2mm in two or more contiguous precordial leads
STEMI criteria: ≥1mm ST elevation in two contiguous limb leads or ≥2mm in two contiguous precordial leads (V1-V6), with specific modified criteria for left bundle branch block and posterior MI.
Question 3: The pre-hospital 12-lead ECG transmission to the cardiac catheterisation laboratory is important because:
- It enables the cath lab to activate and prepare before the patient arrives, reducing door-to-balloon time (Correct answer)
- It replaces the need for in-hospital ECG interpretation
- It allows remote physicians to provide definitive STEMI treatment
- It documents baseline rhythm for medicolegal purposes only
Correct answer: It enables the cath lab to activate and prepare before the patient arrives, reducing door-to-balloon time
Pre-hospital ECG transmission and 'cath lab activation' protocols allow the interventional cardiology team to be ready before patient arrival, reducing the total ischaemic time (first medical contact to balloon) in STEMI.
Question 4: Complete AV block (third-degree heart block) with bradycardia causing haemodynamic compromise is treated pre-hospital with:
- Transcutaneous pacing (TCP) as first-line, with atropine 0.5mg IV if pacing is unavailable (Correct answer)
- Adenosine 6mg IV rapid push
- Amiodarone 300mg IV bolus
- Digoxin loading dose
Correct answer: Transcutaneous pacing (TCP) as first-line, with atropine 0.5mg IV if pacing is unavailable
TCP provides immediate rate control in complete AV block with haemodynamic compromise; atropine may increase ventricular rate as a temporising measure, but the definitive pre-hospital treatment is transcutaneous pacing.
Question 5: Atropine is indicated in which cardiac emergency?
- Symptomatic sinus bradycardia or first/second-degree (Mobitz I) AV block (Correct answer)
- Ventricular fibrillation
- Supraventricular tachycardia
- Complete (third-degree) AV block in infranodal location
Correct answer: Symptomatic sinus bradycardia or first/second-degree (Mobitz I) AV block
Atropine blocks vagal tone to increase heart rate — effective for sinus bradycardia and nodal blocks; it is not effective for infranodal complete AV block and is not indicated in VF/pVT.
Question 6: The maximum compression depth for adult CPR according to current guidelines is:
- At least 5cm but not more than 6cm (Correct answer)
- At least 3cm
- Exactly 4cm
- As deep as possible without limit
Correct answer: At least 5cm but not more than 6cm
Current guidelines recommend 5-6cm compression depth in adults to generate adequate cardiac output during CPR; compressions deeper than 6cm are associated with increased injury risk without additional survival benefit.
DCAS Cardiac Emergencies (ACLS) 2
The 'Hs and Ts' of cardiac arrest represent potentially reversible causes.
Which is an 'H'?