Quadripolar Technology: Case Study and Initial Experience

A diagnosis of heart failure (HF), although treatable, requires lifestyle modification, adherence to medical management, and close follow up with the primary care physician and cardiologist. Today there are approximately five million patients with heart failure in the United States, to which there are 500,000 new cases each year.¹ Even though heart failure patients may receive intense medical management, mortality rates approach 30–50% in some patients over a follow-up period of three to five years.¹

Medical management of HF consists of modulation of the sympathetic nervous system and inhibition of the renin-angiotensin-aldosterone axis. Since publication of the MADIT-I² study in the late 1990s, implantable cardioverter defibrillators (ICDs) have been utilized to decrease the risk of sudden cardiac death in those patients with depressed heart function. Several clinical studies have demonstrated the usefulness of cardiac resynchronization therapy in the setting of refractory HF and presence of intraventricular conduction delay of 120 msec or longer.³ However, the placement of a left ventricular (LV) pacing lead can lead to inadvertent phrenic nerve stimulation (PNS), and in up to 10% patients, may require repositioning of the LV pacing lead.⁴ In this brief case report, we present our initial experience with a quadripolar LV pacing lead.

Case Report

The patient is a 45-year-old male with a history of longstanding hypertension, diabetes mellitus, hyperlipidemia, and peripheral vascular disease. He underwent implantation of a dual chamber permanent pacemaker (Insignia, model 1290, atrial lead model 4086, ventricular lead model 4087, Boston Scientific, Natick, MA) in 2007 for symptomatic complete heart block (CHB); the cardiac workup had included assessment of left ventricular function and performance of coronary angiography. The LVEF as determined by echocardiography was within normal limits. The coronary angiography was unremarkable. The medical regimen had consisted of ACE inhibitors and beta blockers. A follow-up echocardiogram after one year was unremarkable.

The patient was lost to cardiology follow up and presented in late 2011 with NYHA class IV heart failure in spite of being on beta blockers and ACE inhibitors. The patient was admitted to the hospital due to intractable dyspnea at rest and paroxysmal nocturnal dyspnea. On physical examination, he had diffuse crackles with presence of anasarca. Chest x-ray showed severe cardiomegaly with pulmonary vascular congestion, while an echo indicated severely depressed systolic function with an EF less than 20%. Repeat cardiac catheterization was negative for critical coronary artery disease. Despite optimum medical management, the patient’s severity of symptoms persisted and he was requiring dobutamine infusion for circulatory support. He was noted to have recurrent episodes of non-sustained ventricular tachycardia (NSVT) as well. In view of the severity of his HF symptoms, a decision was made to offer the patient an upgrade to a CRT-D. The cardiologists treating the patient felt that the HF might be related to consistent RV pacing or idiopathic/viral cardiomyopathy. The patient then underwent a successful upgrade to a CRT-D (Unify Quadra, model CD3249-40, St. Jude Medical, Sylmar, CA).

During the procedure, the existing permanent pacemaker generator was disconnected from the chronic pacing leads. The RV pacing lead was capped, an ICD lead was implanted and positioned on the septal aspect of the right ventricle. The coronary sinus was cannulated utilizing the coronary sinus sheath, and a quadripolar LV pacing lead (Quartet model 1458Q, St. Jude Medical, Sylmar, CA) was placed in the posterolateral aspect of the left ventricle. Chronic atrial pacing lead was utilized with the new device. The leads were connected to the ICD generator (Figure 1). The baseline EKG and follow-up EKG are shown in Figures 1 and 2. The best LV pacing threshold was between the LV tip and mid 1 electrode (1.5 V at 0.5 msec). The total procedure time for LV lead placement was less than fifteen minutes, and fluoroscopic exposure was 3.5 minutes. Over the next six to twelve hours, the patient had rapid improvement in HF symptoms and was subsequently discharged home on optimal pharmacotherapy for heart failure.

Discussion

A number of clinical studies including the COMPANION study³ have shown the beneficial effects of cardiac resynchronization therapy in patients with refractory HF. The initial experience with CRT has shown that complications relating to coronary sinus (CS) cannulation and delivery of the LV pacing lead to the lateral aspect of the left ventricle include the inability to cannulate the CS, inability to find adequate CS side branch, CS dissection and perforation, phrenic nerve stimulation, frequent lead dislodgements, and high pacing thresholds.4 The advent of bipolar pacing leads for the purpose of left ventricular pacing and concept of electronic repositioning of the LV pacing vector had improved upon the need to perform LV lead repositioning. The availability of dedicated sheaths for CS cannulation such as the RAPIDO advance system (Boston Scientific) and CPS Direct SL2 (St. Jude Medical) has dramatically decreased the procedural time. In addition, most of the LV pacing leads can be delivered over the wire.

The Unify Quadra CRT-D and Quartet LV pacing leads feature first-to-market quadripolar technology. The Quartet left heart pacing lead is built on a platform of QuickFlex µ lead and has good deliverability and stability. The lead has a 4.7 French (Fr) body and 4.0 Fr tip. The insulation is made of chemical polymer that blends polyurethane and silicone. The flexible lead body and narrow ring electrodes provides the necessary maneuverability. The lead can be delivered over the wire or with the support of a stylet and has an IS4 connector. The lead has four pacing electrodes (LV tip designated as Distal I, Mid electrode M2, Mid electrode M3, Proximal electrode 4) and ten pacing configurations (the pacing vectors include pacing between distal, mid and proximal electrodes, and pacing between LV lead electrodes and RV coil), making this CRT system very innovative and enabling it to perform LV pacing at the preferred site without compromising lead stability. There are more options to manage common pacing complications such as phrenic nerve stimulation and high pacing thresholds, resulting in less need for lead repositioning. The early prospective comparison of the Quartet left ventricular pacing lead with conventional bipolar left ventricular pacing leads has shown a decreased need for surgical repositioning of the lead.⁵ The implantation success rates and acute performance of the lead is similar to conventional bipolar pacing leads.⁶

In summary, we believe the Quartet LV pacing lead is a welcome addition to the existing CRT options. It can be implanted with nearly the same success rate as conventional bipolar leads, has a similar acute success rate, and provides more options in the management of complications such as phrenic nerve stimulation and elevated pacing thresholds.

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

References

1. Jessup M, Brozena S. Heart failure. N Engl J Med 2003;348:2007-2018.
2. Moss AJ, Hall WJ, Cannom DS, et al. Improved survival with an implanted defibrillator in patients with coronary disease at high risk for ventricular arrhythmia. N Engl J Med 1996;335:1933-1940.
3. Bristow MR, Saxon LA, Boehmer J, et al. Cardiac-resynchronization therapy with or without an implantable defibrillator in advanced chronic heart failure. N Engl J Med 2004;350:2140-2150.
4. Cazeau S, Leclercq C, Lavergne T, et al. Effects of multisite biventricular pacing in patients with heart failure and intraventricular conduction delay. N Engl J Med 2001;344:873–880.
5. Forleo GB, Della Rocca DG, Papavasileiou LP, et al. Left ventricular pacing with a new quadripolar transvenous lead for CRT: Early results of a prospective comparison with conventional implant outcomes. Heart Rhythm 2011;8:31-37. 
6. Dänschel W, et al. Initial clinical experience with a novel left ventricular quadripolar lead. Oral Session 183/5. Europace 2010;12(suppl 1):i127. Abstract 183/5.