The Allied Health Professional Perspective on Safe and Effective Setup for Cardiac Resynchronization Therapy Device Implantation

The management of heart failure has evolved over the last 10 years, giving health care providers an array of treatment modalities that range from drugs to devices. Device therapy, specifically cardiac resynchronization therapy (CRT), is utilized to provide pacing to both ventricles in an effort to synchronize contractions. Research shows the benefits of CRT included long-term improvements in functional capacity, quality of life and exercise tolerance. Evidence also exists of reduction in neuro-hormonal levels, which drives the decline in myocardial condition and reverse cardiac remodeling. Patient Assessment A detailed review of the patient medical history and current clinical status is necessary to anticipate and effectively respond to peri-operative patient management issues. Current approved devices are indicated for patients with QRS duration ≥ 120 ms (InSync/InSync ICD ≥ 130 ms), left ventricular ejection fraction (LVEF) ≤ 35%, New York Heart Association (NYHA) functional Class III or IV, medically refractory chronic heart failure despite optimal pharmacologic therapy and an ICD indication (CONTAK CD and InSync ICD only). These patients may have a reduced cardiac output and compromised organ and tissue perfusion. It is essential to have a thorough knowledge of the etiology of the patient's heart failure (ischemic, non-ischemic, idiopathic, viral) and prior cardiac procedures (revascularization, angioplasty, stent placement). Knowledge of past revascularizations is useful before performing arterial angiograms for illumination of the coronary sinus (CS) during the Levo phase. Renal function should be evaluated prior to the procedure. CS angiograms are usually necessary for the delineation of coronary venous anatomy, necessitating use of a radiopaque contrast media. Patients with severe renal insufficiency may require special consideration to prevent adverse effects from the use of contrast. Patient hydration prior to and during the procedure should be carefully monitored. In some instances, intravenous inotropic agents may be given to augment cardiac output and increase tissue and organ perfusion. Allergies should be noted to ensure that medication such as antibiotics and/or contrast is properly administered to prevent any adverse reactions. A pre-procedure echocardiogram (echo) report should be obtained to define LVEF, left ventricular hypertrophy, and chamber or mitral valve ring dilation/remodeling that can impact the ease of CS cannulation. In particular, a right atrial dimension greater than 40 mm with dilated cardiomyopathy would suggest advanced cardiac remodeling. There is mounting evidence that cardiac remodeling impacts the size, location and course of the CS immediately distal to the ostium. Recent heart catheterization films showing contrast reflux during the Levo stage of left coronary angiograms can also be helpful in determining the size, location and angle of the CS and existence of collateral veins branching off the CS. Implanting physicians may request the film for viewing prior to implant. Pulmonary function studies should be conducted and reviewed to ascertain the patient risk for respiratory difficulty during this possibly prolonged procedure. Routine pre-operative laboratory analyses include complete blood count, coagulation studies (prothrombin time, INR and platelet count) and serum chemistries (basic metabolic panel, magnesium, brain natriuretic peptide, and creatinine). Patient and Equipment Set-Up Monitoring and surgical preparation. Electrocardiogram (ECG) and pulse oximetry monitoring should be set up similar to a standard pacemaker and/or implantable cardioverter defibrillator (ICD) implant with one special consideration: use of a multiple-lead ECG monitor is recommended since it is instrumental in determining the loss of capture in right and left ventricles during biventricular threshold testing.¹ Should use of a multiple-lead monitor be prohibited due to space or sterility considerations, leads I and III should be viewable simultaneously on a monitor in the room. A multiple-lead monitor with continuous printing capability is valuable for ascertaining and documenting paced morphologies for reference during the case or for chronic follow-up. Figure 1 shows the method of interpreting morphologies in leads I and III to discern LV and RV pacing using tied output devices. Foley catheter insertion is recommended due to procedure length and the need for accurate fluid status management. Surgical preparation should extend from the chin to the axilla, and to just above the umbilicus. This anticipates a pericardiocentesis in the event of cardiac tamponade, and placement of a subcutaneous array lead which may be necessary due to elevated defibrillation thresholds (DFTs). Sterile preparation of the groin is also marking recommended since some physicians use femoral vein access to mark the CS when cannulation attempts are unsuccessful from above. When CS cannulation is difficult from a superior access, a left coronary arteriogram can also be performed with special attention to continuous cine/fluoroscopy until the CS is visible in the Levo phase. The femoral artery may also be utilized for the insertion of an intra-aortic balloon pump in the event of cardiac decompensation during the implant procedure. Finally, left antecubital peripheral IV access can clarify the issue of subclavian patency with contrast injection. Anesthesia. We rely on our anesthesiologist to evaluate each patient for the appropriateness of anesthesia. Conscious sedation without the use of paralytic agents is often utilized at these institutions. Recovery from general anesthesia may be difficult due to the patient s cardiovascular disease, multiple co-morbidities and prolonged procedure time. Experience in these centers has shown that paralytic agents administered can mask the presence of diaphragmatic or phrenic nerve stimulation. This outcome is exceedingly frustrating as it usually requires revision of the left ventricular (LV) lead position!

Manifold and Flush Set-up

The three-port manifold with disposable bag used in cardiac catheterization labs is are advantageous in these cases for several reasons: 1) it eliminates contrast on the field and on physician gloves, 2) it allows the monitoring of CS pressure if desired, 3) it is a proven system in prevention of air emboli (thought it is something to be avoided, injection of air into the venous system is not as critical as it would be in the arterial system). The setup is shown in Figure 2. Add a two-foot connect to the port between the manifold and the rotating valve on the guide catheter to provide a closure. A simple three-way stopcock in lieu of the manifold set-up is a viable alternative. LV Lead Implant Procedure Venous access. Lead implant begins, as in conventional pacemaker and ICD implants, with subclavian or cephalic vein access based on of physician preference. Access (predominantly subclavian vein punctures in these centers, will require placement of three introducer sheaths. Equipment will vary based on individual physician preferences. CS guide catheters for Guidant EASYTRAK and Medtronic Attain leads require a 9 French peel-away introducer with a hemostasis valve and sidearm (Pressure Products, Bard or Medtronic). This provides access for the guide catheter and allows for guide catheter exchanges. The sidearm port provides easy access for administration of IV medication and the option to periodically flush the introducer (not as critical as providing a good flush for the guide catheter).

Guidewires

With over-the-wire lead (OTW) technology, coronary wires have taken on a whole new dimension. Transfer of guidewire technology from interventional cardiology to electrophysiology (EP) procedures introduces the need for nurse/technician skills in handling 180 cm (typical) and exchange-length (300 cm) guidewires and wire peripheral devices. Wire characteristics and their utility in cannulating the CS and the LV lead are outlined in Table 1. Guidewires are available in a wide range of models from different manufacturers. Check that wires are indicated for use in the CS for placement of a LV pacing lead. Also check with industry personnel to determine which wires are best suited for a particular lead. Guidewire peripheral devices such as Touhy-Borst hemostasis valves, wire introducers, steering handles, or torque devices, (to accommodate 0.014˝ to 0.035˝ wires) and 6 French balloon catheters (Swan-Ganz) should be available for every implant. Leads and guide catheters. Lead and wire flushing recommendations and procedures are dependent on the manufacturer. In general, flushing the wire hoops with heparinized saline will help prevent formation to blood clots. When not flushed properly, guide catheters and open-lumen leads can be difficult to handle. Attach the rotating hemostasis valve to the guide catheter to prevent blood loss and provide flush to minimize clots after introduction of the LV pacing lead. Figure 3 shows leads offered by Guidant and Medtronic. Guidant and Medtronic also have a variety of guiding catheters to accommodate specific patient anatomy (Figure 4). The two systems differ in that Guidant offers a steel braided guide catheter designed to slip over the lead terminal pin upon removal, whereas the Medtronic sheaths are designed to be removed using a slitting tool. The two systems require different techniques, so it is imperative that specific training be conducted prior to the implant. Venography and lead position. CS placement of the guide catheter may be verified using different techniques. Fluoroscopic views in right and left anterior oblique positions are critical to differentiating between RA, RV, right ventricular outflow tract (RVOT) or CS placement of the catheter. Sensed signals using a diagnostic EP catheter can augment fluoroscopic views in ascertaining position in the CS. In the CS, intra-cardiac electrograms (EGMs) will display atrial and ventricular depolarizations in the same channel. This recording is done using either a pacing system analyzer or EP monitoring system. Stable positioning of the catheter within the CS is important, as the lead will need the support of the guide catheter in order to traverse valves and to negotiate otherwise tortuous coronary venous anatomy. CS cannulation is required for LV lead implantation (without resorting to an epicardial screw-in lead) and is often the most difficult part of the procedure. Several techniques that can be utilized or combined to mark and cannulate the CS are as follows: 1) injection of contrast puffs through the guiding catheter, 2) probing for the CS ostium with a 0.035˝ guidewire within the guiding catheter, 3) use of transesophogeal echocardiography to visualize the CS, 4) marking of the CS through femoral vein access, and 5) use of a decapolar or deflectable EP catheter (commonly favored by electrophysiologists). CS angiograms are beneficial for optimal placement of the LV lead. Fluoroscopy quality should be equivalent to that available in a catheterization lab. Magnification options of 5, 7, and 9 inches are typical. Images in LAO and RAO are stored and utilized as roadmaps for identification of vein location and direction for CS lead positioning. Figure 5 shows examples of one patient s venous anatomy in three projections. Lead position will depend on the patient s venous anatomy. Current LV pacing leads from Guidant and Medtronic are endovascular leads that access branches off the CS. Ordinarily, CS branches will be present in some combination of the posterior, lateral and anterior free walls of the left ventricle.² Studies have shown the greatest hemodynamic benefit when pacing the left lateral or postero-lateral walls.³ These regions are most often reached via a left posterior or left lateral vein (Figure 6). As in conventional pacemaker and ICD implantation, maximum output pacing during lead testing is vital to test for extracardiac pacing (diaphragmatic or phrenic nerve stimulation). LV pacing, perhaps due to its proximity to the phrenic nerve, can exhibit extracardiac stimulation. Always check for phrenic nerve stimulation with high output pacing. An LV threshold less than 2.0 V at 0.5 ms is desirable but higher thresholds are accepted. Ensure that there is an adequate voltage or pulse width safety margin with no extracardiac stimulation at the higher output. PSA and device-based testing. Prior to removal of the guide catheter and introducer sheaths, LV pacing leads are tested using the PSA in both LV-alone and biventricular pacing configurations. Currently available LV leads come in bipolar and unipolar configurations so the PSA pacing cables must be attached to create the desired pacing configurations. When attached to current approved CRT devices, unipolar pacing leads are configured for LV-cathode (-) and RV-anode (+) pacing and sensing. When using a bipolar LV configuration, LV and RV act as separate bipolar leads. The staff and physician should be familiar with these configurations in order to properly attach the alligator clips to the appropriate conductors for testing. When not contraindicated, the programmed pacing mode most commonly will be DDD below the patient s sinus rate. Therapy relies on the patient receiving 100% ventricular pacing, so give consideration to parameters that can withhold pacing (i.e., ventricular pacing output, maximum tracking rate, AV delay, mode switch). Complications Possible peri-operative complications include: Perforation/CS dissection. Depending on the degree of dissection and the baseline patient condition, physicians may decide to proceed or abort the procedure. Following tissue staining or minor dissection, pulse pressure should be closely monitored during the remainder of the case and post-operatively. Although rare, dissection leading to cardiac tamponade is reason to abort the procedure. Pericardiocentesis kits should be on hand in the event of tamponade. Pneumothorax/hemothorax. The risk of pneumothorax/hemothorax is most likely during subclavian vein access attempts. The use of three introducers during CRT implant may increase the likelihood of these operative complications. Alternate surgical approaches may be considered for the patient who is medically or physically predisposed to this outcome or for those who may be severely compromised by this outcome. Infection. Strict sterile and aseptic techniques should be utilized to minimize the risk of infection. CRT system implants take longer than traditional dual-chamber pacemakers and ICDs, there is an increased handling of sheaths, wires and leads, all of which increase the risk of nosocomial infections. Sterile preparation and procedural technique as described previously in this article has been standardized in our institutions. Acute renal toxicity/failure. Intravenous inotropic medications and fluids may be administered during the case to support optimal renal perfusion. The use of non-ionic, low osmolality contrast media and proper hydration is highly recommended to reduce risk of acute nephrotoxicity. Acute exacerbation of HF. Excess fluid, anesthesia, and defibrillations can lead to acute pulmonary edema and cardiac decompensation. Careful monitoring of peri- and post-operative fluids will minimize the risk of adverse sequelae. Death. Patients indicated for CRT defibrillators are in need of these devices because of increased risk of ventricular dysrhythmias. Attempted CS cannulation may induce atrial and ventricular dysrhythmias. External defibrillation may be necessary. Repeat episodes and shocks can lead to shock-refractory VF and/or pulseless electrical activity. Complication statistics can be obtained from the MIRACLE and CONTAK CD trial reports.

Conclusion

Investigational biventricular implants and subsequent implantation of FDA-approved CONTAK CD/CONTAK CD 2/EASYTRAK and InSync ICD/Attain devices have allowed for the development of successful physician techniques. Accrued experience in setting up, assisting and monitoring these cases has also allowed nurses and technicians to progress up a parallel learning curve. Early procedures took as long as 6-8 hours. At this juncture, typical implant times range from one and a half hours to three hours. Fluoroscopy times have declined, thus exposing the patient and staff to lower amounts of harmful radiation. Equipment costs have also declined due to a higher success rate with current lead delivery systems. Accumulated experiences at these two centers has shown that the keys to successful implants are: 1) knowing the patient and preparing for all possible complications; 2) employing a blend of the best surgical practices from the interventional EP and cardiology fields; 3) discussing the plan for anesthesia and monitoring; and dealing with potential complications; and 4) allowing each physician to utilize his/her own implant techniques. Based on experience and positive outcomes, each institution should develop its own standard of practice that best delivers the therapy in a safe and effective manner.

Acknowledgments. The authors wish to acknowledge Andre Go and Mindi Newman of Guidant Corporation in St. Paul, Minnesota, for their assistance with this article. The photographs and fluoroscopy are provided courtesy of Guidant Corporation, Medtronic Corporation, Dr. Imran Niazi, MD, and St. Luke s Medical Center.