Early Experiences with Novel Quadripolar Technology

Michael Cao, MD
Director of the EP Laboratory at LAC/USC Medical Center
University of Southern California
Los Angeles, California

Michael Cao, MD
Director of the EP Laboratory at LAC/USC Medical Center
University of Southern California
Los Angeles, California

Presentation

The patient is an 81-year-old female with a non-ischemic cardiomyopathy and a left ventricular ejection fraction (LVEF) of 9%. She was admitted for CHF exacerbation and was previously treated with beta-blockers, ACE inhibitors, and a diuretic. The ECG showed sinus rhythm with LBBB and a QRS duration of 130 msec. Inpatient CHF therapy included IV diuretic and IV inotrope, but these medications could not be weaned off. Her medical management was severely limited because of hypotension. Because of her small body habitus (height 4’11” and 98 lbs.), she was not considered a ventricular assist device (VAD) candidate, and because of her age, she was not considered eligible for a heart transplant. After much discussion, it was decided that she may benefit from CRT therapy.

She was enrolled in the St. Jude Medical Promote Q clinical trial, which tested the efficacy of a new quadripolar pacing system, for several reasons. This novel CRT system enables much more flexibility in lead placement due to four electrodes on the LV lead, allowing 10 pacing configurations. With more options to electronically reprogram vectors when CRT complications (such as diaphragmatic stimulation or high thresholds) are encountered, less time and fluoroscopy are required in the implant procedure to otherwise physically reposition the lead. Also, certain vectors will allow more pacing opportunities in the basal or mid-ventricle position; compared to patients with basal LV pacing, patients with apical LV pacing are twice as likely to experience HF hospitalization or death.1 The CRT system used in the study consisted of the Promote Quadra CRT-D and Quartet LV Lead; however, the device that is FDA approved is on the new St. Jude Medical platform, Unify Quadra CRT-D. This device platform is smaller, delivers 40J of energy, and provides ATP in the VF zone, along with other features to reduce inappropriate or unnecessary shocks.

The implantation was performed through a subclavian access approach with a subpectoralis pocket. The RA and RV leads were placed in the right atrial appendage and RV apex. A CS venogram was performed and showed a target vein in the lateral distribution. The LV lead was then placed in the lateral vein position. Initially, there was evidence of diaphragmatic stimulation with a standard bipolar pacing configuration of LV tip to LV ring. Afterward, the device was reprogrammed to the non-traditional pacing vectors using the proximal poles (D1-M2 and M2-RV coil; Figure 3). Between the two configurations, D1-M2 was chosen because of a lower threshold (0.75V@0.5ms), and there was no evidence of diaphragmatic stimulation. DFT testing was successfully performed at 25 Joules. Immediately after placement of the quadripolar CRT system, the patient quickly improved. The baseline ECG showed normal sinus rhythm with LBBB (QRS 130 msec) and the paced ECG showed ventricular pacing with QRS duration of 112 msec. Her shortness of breath improved, and she was able to be weaned off the IV inotrope and IV diuretic. Her treatment was transitioned to an oral regimen, at which time she was discharged from the hospital.

Follow-Up

After the patient was discharged from the hospital, she was seen one week post operatively for a wound check. The site appeared to be healing appropriately and without any evidence of infection or hematoma. The patient commented that her shortness of breath had significantly improved; she was now able to walk 2–3 blocks and was able to perform her activities of daily living. The device was interrogated and demonstrated appropriate biventricular pacing, normal device function, and no evidence of diaphragmatic pacing. In subsequent follow-up, she continues to do well (NYHA class III CHF). Her ejection fraction remains depressed, but for an entire year, she has not developed CHF decompensation or required hospitalization. She has not sustained any ICD discharges or had evidence of diaphragmatic pacing.

Conclusion

This case illustrates a realistic dilemma when medical therapy has no additional benefit. Both VAD and transplant therapy have been shown to be helpful in certain patient populations, but it may not be applicable in all heart failure patients. CRT therapy has been shown to be an effective therapy and can improve NYHA symptoms; however, in certain patients, this benefit may be lost because of complications inherent to CRT such as diaphragmatic pacing. Standard, bipolar LV pacing is limited to three different configurations and may not adequately remedy the diaphragmatic pacing. The St. Jude Medical Quartet LV lead has 10 possible different pacing configurations, which can help avoid this issue. In this particular situation, the clinical benefit was significant and demonstrates the continued efficacy of CRT therapy.

Editor’s Note: This article underwent peer review by one or more members of EP Lab Digest’s editorial board.

Reference

  1. Singh JP. HRS 2010, Late-Breaking Clinical Trials, “Left Ventricular Lead Position and Clinical Outcomes: Findings from MADIT-CRT.”