From:  Myxoedema coma with complete atrioventricular block: a case report

 Differential diagnosis of complete atrioventricular block in this patient.

Potential causePatient-specific evidenceAssessment
Acute coronary ischaemiaDominant RCA; no culprit lesion or significant stenosis; TIMI 3 flow in all major epicardial vessels.Unlikely
Rate-limiting drug effectNo beta-blocker, non-dihydropyridine calcium-channel blocker, digoxin, amiodarone or ivabradine.Unlikely
Hyperkalaemia/Electrolyte disturbanceAdmission VBG K 4.42 mmol/L; sodium, calcium and magnesium not substantially abnormal. Hyperkalaemia developed only later during severe acidosis.Not the presenting cause
Severe hypothyroidism/Myxoedema comaTSH 106 mIU/L, fT4 0.38 ng/dL; evolving multiorgan syndrome; 2026 consensus-adapted Popoveniuc score 120, highly suggestive of myxoedema coma.Strongly supported as a systemic endocrine emergency
Degenerative conduction-system diseaseAge 75 years, hypertension, diabetes, CAD; markedly wide escape QRS; no previous ECG or EPS.Cannot be excluded; principal competing cause of the AV block
HypothermiaTemperature 36.6°C at presentation.Absent
Infiltrative diseaseNo specific diagnostic work-up was undertaken; no direct evidence established during the short course.Not excluded, not supported
Infective/inflammatory AV blockNo specific Lyme/sarcoid-directed work-up; initial WBC and CRP were not suggestive of marked systemic inflammation.Not established
Iatrogenic AV blockNo preceding cardiac procedure or intervention before presentation.Unlikely
Increased vagal tone / acute neurological causeNo compatible trigger or acute neurological syndrome was documented.Not supported

AV: atrioventricular; CAD: coronary artery disease; CRP: C-reactive protein; ECG: electrocardiogram; EPS: electrophysiological study; RCA: right coronary artery; TSH: thyroid-stimulating hormone; TIMI: thrombolysis in myocardial infarction; VBG: venous blood gas.