History
The patient was a 76-year-old man with heart failure, left bundle branch block (LBBB), and paroxysmal atrial fibrillation.
Comments
The patient with symptomatic heart failure (New York Health Association [NYHA] III) was referred for cardiac resynchronization therapy defibrillator (CRT-D) implantation. He had a dilated cardiomyopathy with left ventricular disfunction (ejection fraction <35% documented by echocardiography) and prolonged QRS duration (>120 ms) with LBBB morphology. He was on optimal medical therapy for heart failure, including angiotensin-converting enzyme (ACE) inhibitors and beta blockers. In addition, the patient was on oral anticoagulation therapy with warfarin because of recurrent episodes of atrial fibrillation. A coronary angiography was performed and ruled out an ischemic cause of the cardiomyopathy.
On May 5, 2010, he was implanted with a CRT-D device; the left ventricular lead was positioned into the midlateral vein through the coronary sinus. The best left ventricular capture threshold was 1.5 V at 0.4 ms with left ventricular tip to left ventricular ring vector polarity. No phrenic nerve stimulation was observed, and no complications occurred during and soon after the procedure.
The CRT-D was programmed with left ventricular tip to left ventricular ring polarity, and an algorithm to measure the left ventricular threshold and adapt left ventricular output was activated (LV Capture Management, Medtronic, Minneapolis, Minn.).
A CareLink monitor (Medtronic) for remote monitoring was given to the patient because he lived alone, far from the clinic, and was not able to attend all of the scheduled follow-up visits.
Current Medications
The patient was taking warfarin, optimal medical therapy for heart failure.
Current Symptoms
Exacerbation of cardiac heart failure symptoms with worsening of NHYA class (II to III).
Electrocardiogram
The CareLink monitor transmission for July 3, 2010 was as follows:
• CareLink alert for burden atrial fibrillation (>6 hours) and for increased left ventricular pacing threshold
• Left ventricular pacing threshold 4.0 V at 0.4 ms (+1.75 V compared to that on June 25, 2010)
• Percent V pacing 99.1%
• Leadless electrogram (ECG) shows a changed axis compared to May 2012, 2010 recording
• Left ventricular lead is still pacing (but probably moved back a little)
Findings
Two months after the CRT device implant (July 3, 2010), an automatic CareLink transmission was generated by two different alerts (burden atrial fibrillation longer than 6 hours and increased left ventricular pacing threshold [+1.75 V vs. that on June 25, 2010]) (Figures 24-1 and 24-2). The patient had a history of paroxysmal atrial fibrillation and was already on anticoagulant therapy, so the single atrial fibrillation event was not unexpected. On the leadless ECG transmitted (three electrograms plus high-resolution digital leadless ECG and Active Can-superior vena cava (SVC) Coil [Medtronic] corresponding to lead DI surface ECG), a variation of paced QRS was noted in contrast to the transmission on May 12, 2010 (Figure 24-3, black arrows). The patient was contacted by telephone. He was completely asymptomatic but unable to reach the medical center for clinical follow-up.
The CareLink monitor transmission for October 9, 2010 was as follows:
