Unstable Atrial Fibrillation in a Patient with Severely Reduced Ejection Fraction
A 68-year-old man with ischaemic cardiomyopathy (left ventricular ejection fraction 28%) presents with 6 hours of palpitations and dyspnoea. His regular medications are carvedilol 6.25 mg twice daily, sacubitril–valsartan and spironolactone. His INR has been subtherapeutic for 2 weeks, and apixaban was stopped 5 days ago for a planned colonoscopy. Vital signs: blood pressure 86/54 mmHg, heart rate 148/min irregular, respiratory rate 30/min, SpO₂ 88% on 15 L/min via non-rebreather mask. He is anxious and diaphoretic, with crackles to mid-scapula and cool extremities. ECG shows a narrow-complex irregular tachycardia with no pre-excitation. Bedside echocardiography shows a dilated left ventricle with severe global hypokinesis, no pericardial effusion, and a distended inferior vena cava. Lactate is 3.6 mmol/L.
1. What is your immediate management, and how would you perform and sequence electrical cardioversion in this patient?
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Recognition. This is atrial fibrillation with a rapid ventricular response causing haemodynamic instability: hypotension, pulmonary oedema, hypoxaemia and raised lactate indicate poor end-organ perfusion. Instability here overrides the usual 'rate control first' pathway and the anticoagulation debate.
Immediate actions. Call for senior help and the arrest trolley, apply continuous cardiac monitoring and defibrillator pads, give oxygen, and secure intravenous access. Start norepinephrine early to support the MAP rather than relying on fluid boluses, which will worsen pulmonary oedema in a failing left ventricle with a distended inferior vena cava. Correct obvious precipitants (potassium, magnesium, thyrotoxicosis, sepsis, ischaemia) while preparing to shock.
Cardioversion technique. Use synchronised biphasic cardioversion at 200 J. Confirm the sync markers are tracking the QRS complexes on the monitor before every shock, since irregular rhythms can cause inappropriate triggering. If the first shock fails, repeat at 200 J and then escalate to 360 J, changing pad position (anterior–lateral) and applying pressure. Sedate with a haemodynamically neutral agent such as etomidate or a low-dose ketamine if the patient is not already obtunded; do not delay shock for sedation in a dying patient.
After the shock. Reassess rhythm, blood pressure, oxygenation and lactate. If the rhythm restores but the patient remains hypotensive, look for stunning of the left ventricle, which can last hours to days. If the rhythm recurs, move to pharmacological adjuncts rather than repeated futile shocks.
2. The rhythm recurs after two shocks and he remains hypotensive. What pharmacological strategy would you use for rhythm and rate control in the presence of severe left ventricular dysfunction, and what would you avoid?
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Amiodarone first. Give amiodarone 150 mg intravenously over 10 minutes, then 1 mg/min for 6 hours and 0.5 mg/min thereafter, with blood pressure monitoring during the bolus. It is the safest antiarrhythmic in severe left ventricular dysfunction because it has little negative inotropic effect, and it may both restore sinus rhythm and slow the ventricular response.
Digoxin as an adjunct. In a patient with heart failure and hypotension who cannot tolerate beta-blockade, digoxin can be added for rate control: load 8–12 µg/kg total in divided doses, then 0.125 mg daily, with careful renal dosing and monitoring for toxicity, especially if potassium is low. Its onset is slow, so it supplements rather than replaces amiodarone.
Haemodynamic support. Continue norepinephrine to keep MAP ≥ 65 mmHg, and consider inotropic support or mechanical circulatory support if there is persistent cardiogenic shock. Treat precipitating factors and reassess with echocardiography.
What to avoid. Do not give intravenous beta-blockers or non-dihydropyridine calcium channel blockers (verapamil, diltiazem) - both are negative inotropes and will worsen shock in an ejection fraction of 28%. Avoid class IC agents (flecainide, propafenone) in structural heart disease, avoid dronedarone in decompensated heart failure, and avoid sotalol, which prolongs QT and can cause torsades. Do not rely on digoxin alone for an unstable tachyarrhythmia. If the rhythm and shock remain refractory despite drugs and cardioversion, escalate to urgent electrophysiology or mechanical support rather than stacking negative inotropes.
3. He converts to sinus rhythm after amiodarone and stabilises. How would you manage anticoagulation around the cardioversion and for the longer term?
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Peri-cardioversion. In an unstable patient, cardioversion proceeds without waiting for three weeks of anticoagulation or a transoesophageal echocardiogram. Start therapeutic parenteral anticoagulation immediately (intravenous unfractionated heparin with an appropriate bolus and infusion, or therapeutic low-molecular-weight heparin if renal function allows) and continue it during and after the procedure.
Duration after cardioversion. Anticoagulate for at least 4 weeks after cardioversion regardless of whether sinus rhythm is maintained, because atrial mechanical function recovers slowly and early thromboembolism is well described. His CHA₂DS₂-VASc score is high (age, hypertension, heart failure), so long-term anticoagulation is indicated irrespective of rhythm control.
Choice of agent. Warfarin was subtherapeutic and he has already shown unstable control; a direct oral anticoagulant is preferable unless there is a mechanical valve or moderate-to-severe mitral stenosis. Apixaban 5 mg twice daily is a reasonable choice, with dose reduction only if two of three criteria are met (age ≥ 80 years, weight ≤ 60 kg, creatinine ≥ 1.5 mg/dL). Restart after the colonoscopy once haemostasis is secure, coordinating with the endoscopist: typically 24–48 hours after a diagnostic procedure, longer after polypectomy.
Practical points. Check renal function and full blood count before restarting, counsel on bleeding risk, and arrange follow-up for rate control in heart failure (his carvedilol can be cautiously up-titrated once stable). Do not leave him on heparin indefinitely while the oral decision drifts.