Atrial fibrillation with a rapid ventricular response

Sinus tachycardia with frequent atrial extrasystoles

Anticoagulate and treat the thyrotoxicosis, with cardioversion deferred

Synchronised DC cardioversion today under sedation

Digoxin alone for long-term rate control

Flecainide to restore sinus rhythm chemically

Palpitations for three weeks, worse over the last two days

47-year-old woman. Palpitations for three weeks, worse over the last two days

No cardiac history and no regular medication. Six kilograms of unintended weight loss since the spring, heat intolerance and a fine tremor. Referred by her GP as fast atrial fibrillation for rate control.

Stage 1 of 2

Ingrid Solheim is comfortable at rest and short of breath climbing stairs. The pulse feels irregular at the wrist. Chest is clear, no murmur, thyroid smoothly enlarged with a fine tremor of the outstretched hands. This tracing was recorded on arrival.

Tracing 1 of 2 for the quiz “Palpitations for three weeks, worse over the last two days”. — Twelve-lead on arrival, 25 mm/s, 10 mm/mV. Open this tracing in the studio

What is the rhythm?

AMultifocal atrial tachycardia Your answer
BAtrial fibrillation with a rapid ventricular response Your answer
CAtrial flutter with variable block Correct answer Your answer
DSinus tachycardia with frequent atrial extrasystoles Your answer

Which feature on the paper separates it from fibrillation?

AThe QRS complexes are narrow Your answer
BThe ventricular response is irregular Your answer
CA regular atrial waveform continuing through the complexes Correct answer Your answer
DThe ventricular rate is above 120 Your answer

Stage 2 of 2

She is given a rate-limiting dose of a beta blocker and the ventricular rate settles. TSH is unrecordable and free T4 is 38 pmol/L. This tracing was recorded an hour after the first.

Tracing 2 of 2 for the quiz “Palpitations for three weeks, worse over the last two days”. — Twelve-lead one hour later, 25 mm/s, 10 mm/mV. Open this tracing in the studio

Observations

HR: 75
SpO₂ (%): 98
Respiratory rate: 16
Temperature (°C): 37
Systolic BP (mmHg): 124
Diastolic BP (mmHg): 72

Bloods

TSH (m IU/L): <0.01
Free T4 (pmol/L): 38

What is the atrial rate on the second tracing?

AAbout 150 a minute Your answer
BAbout 75 a minute Your answer
CAbout 300 a minute Correct answer Your answer
DAbout 600 a minute Your answer

What happens next?

AAnticoagulate and treat the thyrotoxicosis, with cardioversion deferred Correct answer Your answer
BSynchronised DC cardioversion today under sedation Your answer
CDigoxin alone for long-term rate control Your answer
DFlecainide to restore sinus rhythm chemically Your answer

Diagnosis

Atrial flutter with variable block in thyrotoxicosis

Thyrotoxicosis is a well known trigger for atrial tachyarrythmias. In a patient with new onset atrial fibrillation or flutter, always go through potential causes. Cardioversion without correction of the underlying cause often will fail and long-term sinus rhythm may not be maintained.

Palpitations for three weeks, worse over the last two days

The case

On arrival

Observations

Bloods

Diagnosis

Discussion