43. Recognition of Anodal Stimulation

This 68-year-old man had a history of non-ST elevation myocardial infarction in 2008 and percutaneous coronary intervention with incomplete revascularization to triple-vessel disease. He developed atrial fibrillation and congestive heart failure in 2010. An echocardiogram showed a left ventricular ejection fraction (LVEF) of 19%, left ventricular end-diastolic volume of 146 mL, and left ventricular end-systolic volume of 119 mL. The QRS width was 144 msec. He remained in New York Heart Association (NYHA) class III while on optimal medical therapy for heart failure. He received a cardiac resynchronization therapy (CRT) pacemaker with bipolar right ventricular lead in the right ventricular apex and bipolar left ventricular lead positioned at the posterior branch of the great cardiac vein together with atrioventricular nodal ablation in 2010. On follow-up, anodal stimulation was detected on device interrogation and testing and the anodal stimulation threshold was 2.0 V at 0.4 msec, which was only slightly higher than the left ventricular lead pacing threshold, at 1.5V at 0.4 msec. The left ventricular lead output was set at 3.0 V at 0.4 msec, which was above the anodal stimulation threshold. No V-V delay was set for the patient. At follow-up examination at 6 months, improvement in symptoms with NYHA class II was noted. An echocardiogram showed an increase in LVEF to 25% and reduced left ventricular end-systolic volume of 91 mL.

The patient was taking clopidogrel 75 mg daily, simvastatin 20 mg daily, lisinopril 10 mg daily, carvedilol 12.5 mg twice daily, and aspirin 80 mg daily.

The patient’s heart failure symptom has improved to NYHA class II. He enjoys light exercise mainly in terms of brisk walking and reports no angina.