Arrhythmias and Conduction Disease — Written Clinical Reasoning

Model answer — Part A: new AF with rapid response in sepsis

Frame the problem first. New AF in sepsis is common and is usually a marker of physiological stress rather than primary cardiac disease. The first question is stability: hypotension, worsening perfusion, ischaemia or pulmonary oedema attributable to the tachycardia would mandate synchronised cardioversion even in a septic patient [1]. His blood pressure of 100/60 on a weaning noradrenaline dose is borderline rather than frankly unstable — but the answer must state that any deterioration buys a shock, not a drug escalation [1].

Treat the driver. Sepsis, hypoxia, hypovolaemia, pain, electrolyte disturbance and catecholamine infusions all perpetuate the arrhythmia. The highest-yield management is aggressive treatment of the sepsis, correction of potassium and magnesium, and review of whether the noradrenaline dose can fall — rate often settles as the physiology settles [1].

Rate versus rhythm reasoning. In the critically ill, rate control is the pragmatic default: cardioversion in septic new AF has a high early recurrence rate while the trigger persists, and antiarrhythmic loading interacts with a shocked circulation. A sensible stated position is rate control now — a beta-blocker if the pressure allows, or digoxin where borderline perfusion limits beta-blockade — with amiodarone reserved for failure, and elective cardioversion reconsidered once the sepsis resolves if AF persists [1] [5]. A strong answer adds the EAST-AFNET 4 framing for later: once recovered, this is recently diagnosed AF with cardiovascular risk factors, where early rhythm-control strategy discussion belongs in outpatient follow-up rather than on the septic ward [2].

Anticoagulation now and at discharge. Do not start therapeutic anticoagulation reflexively during the acute unstable phase — but do not forget it either. The structured answer: calculate CHA₂DS₂-VASc now, reassess bleeding risk while septic and thrombocytopenic-prone, withhold during active instability and any planned procedures, and make a documented decision before discharge — a man of 68 with AF and vascular comorbidity will very likely meet the anticoagulation threshold, where a DOAC is preferred over warfarin for non-valvular AF [3] [4].

Model answer — Part B: syncope with bifascicular block

Frame the problem. Sudden syncope without prodrome, with injury, in a patient with bifascicular block is intermittent complete heart block until proven otherwise. This is a high-risk presentation that mandates admission and telemetry, not outpatient workup [7].

Assessment establishes the phenotype: the history here is the investigation — no prodrome, no postural trigger, brief unconsciousness, rapid recovery, and trauma all point to an arrhythmic mechanism rather than reflex syncope or seizure. Examination looks for a slow or irregular pulse now, heart failure signs, and aortic stenosis; the medication list is reviewed for beta-blockers, calcium channel blockers and digoxin [7].

Investigations: continuous telemetry; serial 12-lead ECGs looking for progression (longer PR, alternating bundle branch block patterns, higher-grade block); echocardiography for structural disease; electrolytes, troponin and thyroid function; and, if the diagnosis remains unproven and pacing is deferred, an implantable loop recorder — the ESC syncope guideline positions ILR early in unexplained high-risk syncope [7]. An electrophysiological study can help where the story is atypical but conduction disease is suspected.

Pacing reasoning. Guidelines support permanent pacing in patients with syncope and bifascicular block when the syncope is unexplained and the clinical phenotype is arrhythmic, because progression to complete heart block is common and the next event may be fatal or injurious [6] [8]. The model answer states this plainly, notes the alternatives (documented intermittent complete block on telemetry would make the indication absolute), and closes with the practicalities: driving advice, injury prevention, and shared decision-making about timing [6].