An unwell older woman with bradycardia and confusion on digoxin

Diagnosis: digoxin toxicity with a junctional bradyarrhythmia, precipitated by verapamil, on a background of new acute kidney injury.

The reasoning runs medicine by medicine:

• Verapamil is the key event. It inhibits P-glycoprotein, increasing digoxin absorption and reducing its clearance, so the level rises even at an unchanged digoxin dose. It also adds direct negative chronotropy at the AV node and is contraindicated in heart failure with reduced ejection fraction. Two prescribers each made a defensible single decision that became unsafe together.
• Digoxin is largely cleared unchanged by the kidney. With creatinine rising from 110 to 178 micromol/L, clearance falls and a previously stable dose accumulates. Her small body mass (52 kg) and age further reduce the volume of distribution and clearance.
• Furosemide can cause hypokalaemia and hypomagnesaemia, both of which potentiate digoxin binding at the Na/K-ATPase. Her potassium of 4.8 is not low, but with an AKI and digoxin toxicity it must be watched closely - a rising potassium here signals severity, not safety.
• Perindopril and carvedilol do not cause toxicity but both contribute to the bradycardia and blunted compensatory response.

The symptoms are textbook: anorexia, nausea and vomiting (often the earliest), confusion, and xanthopsia with yellow halos. The ECG completes the picture with a junctional bradycardia and the downsloping 'reverse tick' ST depression. A level of 3.9 nmol/L is well above the therapeutic range, though the decision to treat rests on the patient and the ECG, not the number alone.

Resuscitation and monitoring first

• Move to a monitored area, continuous ECG, IV access, oxygen if needed, and 12-lead ECGs serially.
• Stop digoxin and stop verapamil.
• Send repeat U&E, magnesium, calcium, thyroid function, glucose and a digoxin level; group and hold.
• Treat symptomatic bradycardia with atropine 0.5-0.6 mg IV (up to 3 mg total) and have transcutaneous pacing and an adrenaline infusion ready if she becomes haemodynamically unstable.
• Correct magnesium and potassium cautiously; do not aggressively chase a potassium of 4.8 downwards.

When to give digoxin-specific antibody fragments

Give them, not just consider them, for: life-threatening arrhythmia (ventricular tachycardia or fibrillation, complete heart block, asystole), hyperkalaemia above about 5.5-6 mmol/L in the setting of toxicity, a very high level (above roughly 10-15 nmol/L), or a significant acute overdose. She is on the borderline: if her bradycardia becomes symptomatic or refractory, or her potassium climbs, give fragments early rather than waiting. Dose is calculated from level and weight per local protocol, or 10-20 vials empirically if the level is unavailable. Seek cardiology and ICU input early.

What to avoid

• Calcium salts - classically avoided in digoxin toxicity because of the risk of 'stone heart'.
• Other negative chronotropes - further beta-blockade, diltiazem or amiodarone.
• Electrical cardioversion unless absolutely unavoidable; if it must be done, use low energy with pacing and fragments available, as it can precipitate ventricular fibrillation.
• Do not simply observe a confused, bradycardic patient on a ward without monitoring.

Medication changes

• Verapamil must not be restarted. It is contraindicated in heart failure with reduced ejection fraction and was the precipitant. Document the reason clearly in the notes and on the discharge summary.
• Digoxin: if it is still needed for rate control, reduce to 62.5 micrograms daily (or alternate days) given her age, weight and creatinine, with a level and U&E check at 1-2 weeks. Aim for a trough of 0.5-0.9 nmol/L in heart failure and AF, not the old upper limit of the range.
• Rate control strategy: carvedilol is already in place; optimise it rather than adding another AV-nodal blocker. If rate remains uncontrolled, involve cardiology - a low-dose digoxin with careful monitoring, or consideration of rhythm control/ablation, is safer than re-adding a non-dihydropyridine calcium channel blocker.
• Furosemide: review the dose, check U&E after any change, and give clear 'sick day' rules - hold the diuretic and perindopril during vomiting or dehydration and seek advice.
• Heart failure therapy: this admission is a prompt to review whether she is on guideline therapy (including an SGLT2 inhibitor) and to refer to the heart failure nurse.

What to tell her and her daughter

Explain in plain language that two medicines interacted and that she became unwell because the digoxin built up when her kidneys were stressed. Give a written, updated medicine list, tell every future prescriber and pharmacist that she takes digoxin, and warn about the early symptoms - nausea, loss of appetite, visual changes, confusion, a slow pulse - with clear instructions to stop the digoxin and call an ambulance. Arrange GP review within a week and a medication reconciliation by the pharmacy.