Mapping Localized Sources in a 66-Year-Old Gentleman with Persistent AFib Despite Prior Ablation and Multiple Anti-Arrhythmic Medications

A 66-year-old gentleman with persistent atrial fibrillation (AF) for over 10 years presents to the clinic for evaluation of highly symptomatic AF causing fatigue, exertional shortness of breath and palpitations. His CHADS2VASc score is 4 and he currently takes warfarin anticoagulation. He failed sotalol in the past and has received multiple cardioversions (6 over 5 years) in attempts to maintain sinus rhythm. He underwent wide area circumferential ablation for pulmonary vein isolation, and a linear left atrial roof ablation 2 years prior to this presentation. However, he continues to have highly symptomatic break though episodes of AF on another anti arrhythmic drug dofetilide.

Figure 1: The 12-lead electrocardiogram in clinic.

Figure 2: FIRM (Focal Impulse and Rotor Modulation) Mapping in AFib.

Pertinent past medical history also includes hypertension, transient ischemic attacks and hepatitis B, as well as prior AF ablation.

Warfarin for target INR 2.0- 3.0, diltiazem SA 360mg once daily, dofetilide 250 mcg twice daily, losartan 100mg once daily, sildenafil 25mg once daily, Vitamin D3 2000 units daily and Calcium carbonate 500mg three times daily.

Physical Exam:
Vital signs: Heart rate 110 beats/min in AF in clinic, BP 145/92 mm hg, RR 18, Afebrile, BMI 30
General: Alert, Comfortable and oriented to time, place and person
Neck: 9 cm JVD
CV: Irregularly irregular, No murmurs noted
Lungs: Clear to auscultation
Abdomen: soft tender without any masses
Extremities: No pedal edema
Neurological exam: No gross neurological deficits

Pertinent Labs and echocardiographic parameters:
TSH: 2.69 (Range 0.49-4.69 mIU/ml)
Serum Creatinine- 1.11 (Range 0.4-1.2 mg/dl)
Echocardiogram: Normal left ventricular size, thickness and function (LVEF 60%). Left atrial enlargement (left atrial diameter 62 mm). No significant valvular abnormalities noted.

After a discussion of treatment alternatives, risks and benefits, the patient was taken to the electrophysiology laboratory for repeat ablation. Under specific IRB approved informed consent, AF was mapped prior to ablation using a new approach (Focal Impulse and Rotor Mapping, FIRM) by inserting a 64 pole basket catheter (Constellation, Boston Scientific, MA) into the right then left atria in turn. FIRM maps reveal the following maps of AF activation:

Activation during AF is color coded from early (red) to late (blue). A rotor is seen in the posteroinferior right atrium (indicated by a red-to-blue spiral wave), while the left atrium shows very disorganized activity. Key: The right atrium is opened at a meridian, with reflection of the lateral and medial tricuspid annuli. The left atrium is opened at its equator, with reflection of the superior and inferior mitral annuli. The pulmonary vein orifices (left atrium) are labeled.

Based on the above information, the step most likely to treat this man’s AF would be:

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