Left Ventricular Lead Placement Outside the Cardiac Veins

Background

Cardiac resynchronization therapy (CRT) has proved a highly effective treatment for many patients suffering from heart failure. The nonresponder rate in many series is, however, still in the 30% range. There are many facets to the issue of “nonresponse.” Clinical conditions vary widely and impact on the clinical utility and outcomes of CRT: QRS width, ejection fraction, cause of ischemic or nonischemic disease, and location of ischemic scars. Thus careful patient selection is critical for CRT response. Correct pacing location for stimulus delivery is equally critical to achieve response. Nonischemic and especially ischemic disease expression will affect how depolarization occurs in the myocardium. Many recent studies have focused on finding the optimal location for delivery of left ventricular (LV) stimuli in relation to right ventricular (RV) stimulation and in finding the optimal timing of impulses. In several studies stimulation at the point of latest LV activation has proved a simple, yet effective principle to achieve good response.

Transvenous lead placement via the coronary sinus limits, by anatomy, and lead placement to available side branches, often do not achieve optimal resynchronization of the ventricular mass. In addition to anatomic venous limitations, vessel obliteration following infarction is common in ischemic patients. Considering the heterogeneity of patients and that LV stimulation at present is often delivered haphazardly, the current responder rate is surprisingly high. LV lead placement is often considered satisfactory if energy is delivered to the lateral aspect of the left ventricle, diaphragmatic stimulation is absent, and thresholds are acceptable. In addition, right atrial (RA) and RV leads are usually not prescriptively placed. There is the potential for better CRT outcomes with the careful prescription of LV pacing location, and this may be best achieved either by surgical epicardial lead placement or LV endocardial lead placement, as both approaches overcome the inherent limitations imposed by coronary sinus (CS) anatomy.

Surgical Epicardial Left Ventricular Lead Placement

Direct or surgical epicardial placement is an attractive lead implantation alternative allowing energy to be delivered to the LV at any location, thereby avoiding the transvenous route limitations ( Case Study 31-1 ). Very importantly, direct epicardial lead placement also allows electrical mapping before placement of the LV lead. A simple principle that seems to be highly efficient for achieving response is to place the LV lead in a position where the longest sensed R-R interval is found. This principle has been highly effective in the reported literature and also in the authors' experience, reducing nonresponders to a small group of patients with multiple and significant infarction scars. It has also been shown that reverse anatomic remodeling occurs at the same rate after either transvenous or direct lead placement.

Case Study 31-1

Recurrent Device-Related Infections

History

This 63-year-old gentleman presented with tenderness, swelling, and redness over his biventricular implantable cardioverter defibrillator (BiV-ICD) pocket. He had a history of type 2 diabetes mellitus, chronic obstructive pulmonary disease, ischemic cardiomyopathy, chronic kidney disease, and ventricular tachycardia. He had previously undergone laser lead extraction for tricuspid valve endocarditis related to a dual-chamber pacemaker. That left-sided device had been extracted, and after an appropriate waiting period while on antibiotic therapy, a new system had been implanted on the right side. It had been over a year since his previous device implantation.

Current Medications

The patient was taking aspirin 81 mg daily, carvedilol 25 mg twice daily, lisinopril 20 mg daily, atorvastatin 80 mg daily, bumetanide 0.5 mg twice daily, dofetilide 0.25 mg twice daily, spironolactone 25 mg daily, vancomycin, cefepime, and insulin.

Physical Examination

• Vital signs: BP 120/73 mm Hg, HR 92 bpm, temperature 98.8° F

• Head/neck: No evidence of jugular venous distention.

• Lungs/chest: Clear to auscultation and percussion bilaterally. 2 × 2 cm area of fluctuance surrounded by erythema over the ICD pocket.

• Heart: Nondisplaced point of maximum impulse (PMI). Regular rate and rhythm. No appreciable murmurs, rubs, or gallops.

• Abdomen: Soft, normoactive bowel sounds.

• Lower extremities: No edema. Warm and well perfused.

Laboratory Data

• White blood cell count: 9.4 × 10 ³ /mm ³

• Hemoglobin: 12.5 g/dL

• Mean corpuscular volume: 85.6 fL

• Platelet count: 152 × 10 ³ /mm ³

• Sodium: 139 mmol/L

• Potassium: 4.1 mmol/L

• Creatinine: 1.5 mg/dL

• Blood urea nitrogen: 25 mg/dL

Imaging

Transesophageal echocardiography (TTE) revealed a left ventricular ejection fraction (LVEF) of 20%-25% and no evidence of vegetations.

Hospital Course

He was referred for repeat lead extraction. At the time of surgical incision, a copious amount of infected fluid was found in the pocket ( Fig. E31-1 ). The entire system was removed, and he completed an appropriate course of antibiotic therapy. The wound culture grew Staphylococcus epidermidis. Venography of the left subclavian system performed at the time of lead extraction revealed severe central venous stenosis that was not amenable to angioplasty or stenting ( Fig. E31-2 ).

Focused Clinical Questions and Discussion Points

• Question: What options are available for patients with recurrent cardiac implantable electronic device (CIED)-related infection? What group of patients is particularly likely to benefit from completely epicardial CIED system implantation?

• Discussion: Every patient with a CIED-related infection should undergo complete removal of the entire system whenever feasible, followed by reimplantation after the infection has been cleared. Reimplantation, when indicated, should occur at a different site (e.g., the contralateral side or the abdomen). In the setting of recurrent CIED-related infections or if a patient is felt to be at particularly high risk for CIED-related infection consideration should be given to implanting a completely epicardial system. Patients with end-stage renal disease (ESRD), in particular, may benefit from completely epicardial systems. These patients are at elevated risk of bloodstream infections that may result in CIED-related infection. Furthermore, they are dependent on the patency of their central venous systems in order to receive hemodialysis, a life-prolonging therapy. Completely epicardial CIED systems may ameliorate these risks in this unique group of patients.

Final Diagnosis

CIED-related pocket infection

Management

He underwent successful implantation of a completely epicardial BiV-ICD system ( Figs. E31-3 and E31-4 ).

References

• 1.

  Sohail MR, Uslan DZ, Khan AH, et al: Management and outcome of permanent pacemaker and implantable cardioverter-defibrillator infections. J Am Coll Cardiol 49(18):1851–1859, 2007.

• 2.

  Chua JD, Wilkoff BL, Lee I, et al: Diagnosis and management of infections involving implantable electrophysiologic cardiac devices. Ann Intern Med 133(8):604–608, 2000.

• 3.

  Asif A, Carrillo R, Garisto JD, et al: Epicardial cardiac rhythm devices for dialysis patients: minimizing the risk of infection and preserving central veins. Semin Dialysis 25(1):88–94, 2012.

Left Ventricular Endocardial Pacing

LV endocardial pacing is another alternative pacing approach to that offered by “conventional” CS or “surgically placed” epicardial pacing, for LV activation in the context of CRT. Its purpose is delivery to the endocardial surface of a pacing stimulus for initiation of myocardial activation. The pacing stimulus initiates an activation wave front from the point at which that activation stimulus is delivered. Such a stimulus may be delivered in unipolar or bipolar mode from pacing devices. There is some evidence that LV endocardial pacing may offer improved functional outcomes for CRT recipients compared with conventional approaches, but that possible advantage needs to be balanced against the procedural challenges and the requirement for long-term anticoagulation to avoid thromboembolic risk. LV endocardial pacing offers the “landscape” of the endocardial surface for pacing and therefore choice of optimal pacing site (however that choice might be made), unlike the restricted CS anatomy.

Pacing systems comprise pacing electrodes mounted on standard pacing leads, self-contained “leadless” pacemakers with integral bipolar pacing electrodes, and “independent” pacing electrodes that are fixed to the endocardial surface but which have physically remote power units to deliver the necessary energy wirelessly to the pacing electrode for the development of potential difference at the pacing electrodes, which then initiate myocardial activation.

The “leadless” pacemakers are currently indicated only for RV pacing. For reasons of size and procedural risk, it is unlikely that such devices will be clinically available for LV endocardial pacing in the immediate future. Furthermore, the delivery tools and procedural approaches for their use in the left ventricle have yet to be developed, and therefore these technologies are not considered further. The focus is on the clinically available “conventional” lead-based approaches to LV endocardial pacing with brief reference to the investigational “independent” pacing electrode technology.

Surgical Epicardial Lead Placement Techniques

Epicardial lead placement has some potential drawbacks that must be solved to make epicardial lead placement more common. Traditional full left-sided thoracotomy, if not adequately modified, can be associated with significant and unnecessary morbidity. Fortunately, several less invasive and, from a morbidity point of view, more attractive approaches are available and will be discussed ( Case Study 31-2 ). One remaining disadvantage with epicardial stimulation difficult to overcome is that endocardial stimulation in several studies has proved more effective than epicardial; this disadvantage also applies to transvenous CS stimulation.