The Importance of Maintaining a High Percentage of Biventricular Pacing

History

The patient is a 54-year-old man with a history of a nonischemic dilated cardiomyopathy. He was initially referred for consideration of a third procedure for atrial fibrillation. He had undergone pulmonary vein isolation procedures 1 year and 3 months previously. In addition to pulmonary vein isolation, linear ablation of both the left and right atria had been performed, as well as targeting of complex fractionated atrial electrograms. Despite this, the patient experienced early recurrences of atrial fibrillation and atypical atrial flutter soon after each ablation. In addition, amiodarone, digoxin, and beta blockade were used as adjunctive therapy, yet rate control remained poor. Heart rates during waking hours averaged approximately 110 bpm. Left ventricular systolic function was globally reduced, and the ejection fraction was estimated to be approximately 20%. His symptom was New York Heart Association (NYHA) class II to III dyspnea, yet he had no history of hospital admissions for heart failure, no palpitations, and no presyncopal symptoms.

The patient had failed an antiarrhythmic strategy using a combination of medication and ablation. Furthermore, he was failing a rate control strategy using three different atrioventricular nodal blocking agents. He remained tachycardic and symptomatic, and therefore the following therapeutic options were discussed with him and his family: (1) a third catheter ablation for atrial fibrillation, (2) permanent pacemaker implantation with adjunctive atrioventricular nodal ablation, and (3) open surgical cut-and-sew maze procedure. The patient elected to proceed with atrioventricular nodal ablation and permanent pacemaker implantation.

Current Medications

The patient was taking digoxin 250 mcg daily, furosemide 20 mg daily, losartan 50 mg daily, amiodarone 300 mg daily, metoprolol 100 mg twice daily, spironolactone 25 mg daily, and warfarin to maintain international normalized ratio between 2 and 3.

Current Symptoms

The patient’s predominant symptom was dyspnea on exertion. His exercise tolerance was limited to flat surfaces. In addition, he was frequently becoming dyspneic with simple activities of daily living while working on his farm. He had not had any syncopal episodes and was not aware of any palpitations.

Physical Examination

• BP/HR: 101/67 mm Hg/97 bpm

• Height/weight: 180 cm/105 kg

• Neck veins: No jugular vein distention, no carotid bruits

• Lungs/chest: Clear

• Heart: Rapid irregular heart rate with normal first heart sound (S ₁ ) and second heart sound (S ₂ ), no murmur

• Abdomen: Soft, nontender with no organomegaly

• Extremities: Minimal edema, normal volume pulses

Laboratory Data

• Hemoglobin: 15.1 g/dL

• Mean corpuscular volume: 88 fL

• Platelet count: 351 × 10 ³ /µL

• Sodium: 140 mmol/L

• Potassium: 5.0 mmol/L

• Creatinine: 1.2 × 10 ⁹ /L

• Blood urea nitrogen: 30 mmol/L

Electrocardiogram

Findings

Figure 25-1 shows the electrocardiogram (ECG) obtained before device implantation. The rhythm is atrial fibrillation with a fairly rapid ventricular response. The QRS duration is less than 100 ms, and no evidence of acute ischemia is present.

Figure 25-2 shows the ECG obtained after atrioventricular node ablation and device implantation. The rhythm is atrial fibrillation, with evidence of biventricular pacing. Frequent premature ventricular contractions occurred, with varying degrees of fusion.

Chest Radiograph

Findings

The chest radiograph showed the heart size to be normal. Mild pulmonary venous hypertension was noted ( Figure 25-3 ).