What does this tracing show?

Sinus bradycardia at about 50/min with a PR interval of 380 ms, every P conducted

Complete AV block with a narrow junctional escape at about 50/min

2:1 AV block, with every second P wave failing to conduct

Sinus bradycardia at about 50/min with a PR interval of 180 ms and normal conduction

Second-degree block, Mobitz I, with progressive PR lengthening and a dropped beat

Given the PR interval measured on this tracing, what is the appropriate next step?

Admit to a monitored bed with continuous ECG telemetry and serial ECGs

Discharge with a cardiology clinic appointment in two weeks and a repeat ECG then

Give atropine 500 micrograms intravenously and repeat the ECG in one hour

Refer for a permanent dual-chamber pacemaker before he leaves the department

Start bisoprolol 2.5 mg orally for the palpitations and review him in the morning

Lightheadedness and palpitations for three days

Forestry worker. Spent August clearing scrub; treated an expanding red rash on the thigh himself with antiseptic cream about four weeks ago. No regular medication, no drugs, no family history of sudden death. Referred in by his GP after an ECG at the surgery.

Stage 2 of 2

He is admitted overnight. Borrelia burgdorferi IgM and IgG come back positive and intravenous ceftriaxone is started. At the 07:00 round he says he felt very heavy-legged walking to the toilet; the nurse recorded a pulse of 38 and a blood pressure of 104/62. A fresh 12-lead is taken at the bedside.

Tracing 2 of 2 for the quiz “Lightheadedness and palpitations for three days”. — 12-lead recorded on the monitored bed the next morning. Open this tracing in the studio

Observations

HR: 38
SpO₂ (%): 98
Respiratory rate: 15
Temperature (°C): 37.2
Systolic BP (mmHg): 104
Diastolic BP (mmHg): 62

Bloods

Borrelia Ig G: positive
Borrelia Ig M: positive
Troponin T (ng/L): 18
Potassium (mmol/L): 4.2

What has changed on this tracing compared with the one taken at triage?

AThe sinus node has stopped and a junctional rhythm at about 38/min conducts back to the atria after each QRS Your answer
BP waves at about 80/min now bear no relation to a regular narrow escape at about 38/min Correct answer Your answer
CConduction is now 2:1 from an atrial rate of about 80/min, giving a ventricular rate of about 38/min Your answer
DConduction is now 3:2 with a constant PR interval and every third P wave dropped Your answer
EThe sinus rate has fallen to about 38/min and the PR interval has lengthened further, with every P still conducted Your answer

How should his conduction be managed from here?

AContinue intravenous ceftriaxone on a monitored bed with transvenous pacing immediately available Correct answer Your answer
BStart an isoprenaline infusion on the ward and repeat the ECG in the morning Your answer
CSwitch to oral doxycycline and discharge him once the ventricular rate is above 50/min Your answer
DImplant a permanent dual-chamber pacemaker during this admission Your answer

Lightheadedness and palpitations for three days

The case

On arrival

Observations

Observations

Bloods

Diagnosis

Discussion