Cardiovascular Critical Care and Arrhythmias
Cardiovascular critical care on this Board blends ischaemic syndromes, rhythm recognition and the pharmacology of the arresting patient. Expect energy levels, drug doses and reversible causes.
Acute coronary syndromes in the ICU
Troponin is a marker, not a diagnosis: interpret the delta and the clinical story. STEMI needs reperfusion - primary PCI within 120 minutes where available. Dual antiplatelet therapy plus anticoagulation, high-intensity statin, and a beta-blocker when there is no shock or heart failure. In cardiogenic shock complicating infarction, early revascularisation saves lives; intra-aortic balloon counterpulsation does not routinely reduce mortality and is reserved for mechanical complications such as papillary muscle rupture or ventricular septal defect.
Unstable versus stable arrhythmia
Unstable means hypotension, ischaemia, altered mentation or heart failure - synchronised cardioversion at 100-200 J biphasic, unsynchronised defibrillation for pulseless ventricular tachycardia or fibrillation. Stable narrow-complex SVT: vagal manoeuvres, then adenosine 6 mg IV, then 12 mg. Atrial fibrillation with rapid ventricular response: rate control with a beta-blocker or diltiazem, rhythm control if new onset and haemodynamically relevant; correct potassium and magnesium first. Stable wide-complex tachycardia: amiodarone 150 mg over 10 minutes or procainamide.
Bradycardia and arrest
Atropine 1 mg IV every 3-5 minutes to a maximum of 3 mg, then transcutaneous pacing, then adrenaline or dopamine infusion. For pulseless arrest: compressions 100-120/min at 5-6 cm depth, minimal interruptions, adrenaline 1 mg every 3-5 minutes, amiodarone 300 mg after the third shock for refractory VF, and a search of the 5H5T list.
Worked example
A 60-year-old on haemodialysis presents with palpitations, BP 80/50, a wide QRS at 180/min and potassium 7.1 mmol/L. This is a hyperkalaemic sine-wave rhythm, not a primary arrhythmia: give intravenous calcium gluconate immediately, then insulin-dextrose, and dialyse. Cardioversion would fail and delay the correct treatment.
Traps
Cardioverting sinus tachycardia. Forgetting magnesium 2 g IV in torsades and stopping QT-prolonging drugs. Using lidocaine first-line in monomorphic VT with a pulse. Delivering unsynchronised shocks to a patient with a pulse. Missing that a new bundle branch block with chest pain may be an occlusion equivalent.