History
A 62-year-old nonsmoking man was referred for upgrade of his dual-chamber pacing system to a cardiac resynchronization therapy (CRT) pacing system. The dual-chamber pacing system had been implanted 4 years earlier. The initial indication for cardiac pacing was complete heart block that developed roughly 8 hours after radiofrequency ablation of the cavotricuspid isthmus for the treatment of symptomatic atrial flutter. The components of this initial pacing system were a St. Jude Medical Victory XL DR 5816, a Medtronic bipolar screw-in atrial lead 5568-53, and a Medtronic bipolar screw-in ventricular lead 4076-58. At the time the initial pacing system was implanted, his left ventricular size and ejection fraction (60%-65%) were normal. On device interrogation he routinely paced more than 99% of the time.
The patient developed fatigue, exercise intolerance, and dyspnea on exertion. After atrial flutter ablation, he was started on flecainide for symptomatic paroxysmal atrial fibrillation. His other pertinent medical history included dyslipidemia and hypertension. His ejection fraction was reassessed. His left ventricular ejection fraction by radionuclide angiogram was 38%. An ischemic cause for his cardiomyopathy was ruled out by elective coronary angiography.
Current Medications
The patient’s daily medications were aspirin 81 mg, cetirizine 10 mg, dutasteride 0.5 mg, enalapril 5 mg, escitalopram 10 mg, flecainide 50 mg, hydrochlorothiazide 25 mg, and simvastatin 80 mg.
Comments
Flecainide is generally avoided in patients with conduction system disease. Flecainide slows conduction that can further widen the QRS complex from baseline, leading for further ventricular dyssynchrony. Flecainide also should be avoided in patients with coronary or structural heart disease because of the increased risk for malignant tachyarrhythmias. Flecainide was discontinued in this patient for these reasons.
Current Symptoms
The patient’s symptoms included fatigue, exercise intolerance, and dyspnea on exertion.
Physical Examination
Laboratory Data
Electrocardiogram
Findings
An electrocardiogram demonstrating atrioventricular sequential dual-chamber pacing at a rate of 60 bpm (Figure 10-1) and QRS duration of 182 ms.
Comments
The morphology of the paced QRS is consistent with a right ventricular apical location. The paced left bundle branch (LBB) morphology suggests right ventricular origin. The predominant positive voltage in lead I is due to right-to-left activation. The apical position is supported by the completely negative morphology in V4 (apical lead) resulting from ventricular activation away from the apex.
Chest Radiograph
Findings
Chest radiography was performed in posteroanterior (Figure 10-2, A) and lateral (Figure 10-2, B) views. The left infraclavicular pacemaker has leads positioned in the right atrial appendage and the right ventricular septum.
Focused Clinical Questions and Discussion Points
Question
What anatomic landmarks are relevant for successful and efficient deployment of a left ventricular lead?
