Pacemaker/ICD Puzzle Revealed!

Clinical History A 56-year-old female with non-ischemic dilated cardiomyopathy, an ejection fraction of 25%, congestive heart failure, recurrent atrial fibrillation, pulmonary hypertension, and hyperlipidemia, states that she has periodic palpitations associated with shortness of breath. She denies chest pain, orthopnea, dizziness, and syncope. Device History S/P ICD implantation: ICD: Medtronic D154ATG EnTrust A Lead: Medtronic 5076 CapSure Fix Novus V Lead: Medtronic 6949 Sprint Fidelis Medications Coreg: 6.25 mg bid Digoxin: 0.25 mg qd Lasix: 80 mg bid Lisinopril: 10 mg qd Spironolactone: 25 mg, 1/2 tab qd Warfarin (as directed) Lipitor: 20 mg qd Zyrtec: 10 mg qd Physical Examination On examination, there was no JVD, chest sounds were clear to auscultation, heart sounds were regular with a normal S1, S2 without rubs, murmurs or gallops, and no edema. Device evaluation revealed normal ICD function: No ventricular tachyarrhythmias No atrial fibrillation No change in atrial and ventricular stimulation and sensing thresholds 24-hour Holter revealed this ECG (See Figure 1) Pacemaker/ICD Puzzle Question: Which of the following is demonstrated in the Holter recording shown in Figure 1? A: Ventricular oversensing B: Loss of ventricular capture C: Concealed conduction D: Crosstalk inhibition E: Normal device function (Correct Answer!) Explanation: Normal device function is due to Managed Ventricular Pacing (MVP); MVP is designed to provide functional AAI(R) pacing mode while providing the safety of dual chamber ventricular pacing in the presence of persistent or transient loss of conduction; The key benefit is a reduction in unnecessary RV pacing due to the promotion of AV synchrony; The potential clinical outcomes are a reduction in cumulative percent of RV-pacing, which may result in reduced incidence of AT/AF and slow the progression of heart failure.