Interventional Techniques for Device Implantation

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23 Interventional Techniques for Device Implantation

Initially, device implantation was the province of surgeons, and thus implant problems were solved with surgical techniques, such as tunneling of a new lead for a patient with an occluded subclavian vein. As devices became smaller and almost exclusively transvenous, implantation moved to the province of the cardiologist and then subsequently to the electrophysiologist (EP). Until recently, the mechanics of transvenous device implantation were generally straightforward, adopting surgical solutions and applying an electrophysiology skill set and tools. Over the last several years, however, with the marked increase in device upgrades and cardiac resynchronization therapy (CRT), the complexity of device implantation has increased greatly, becoming similar to an interventional procedure rather than the traditional device implant. Lacking interventional training, EP physicians have struggled to solve difficult implant problems with their electrophysiology skill set and tools. As a result, even now, the CRT implant failure rate remains at least 7.5% in experienced hands.¹

Interventional versus Electrophysiologic Approach

It is preferable to learn a new skill set better suited to the procedure than to continue with familiar methods. How would the current implant procedure change if device implantation was assumed by an interventional cardiology skill set rather than electrophysiology?

Consider the occluded subclavian vein. With expanded indications for implantable cardioverter-defibrillators (ICDs),² CRT,^3,⁴ and increased survival of patients with cardiovascular disease,⁵ the implanting physician encounters a higher percentage of patients who have preexisting leads in whom subclavian vein obstruction or occlusion can be as high as 45%.⁶ Application of an interventional approach to the occluded vessel offers the implanting physician less invasive solutions, such as venoplasty versus lead extraction or tunneling.⁷^–¹⁰

Left ventricular (LV) lead placement for CRT requires the successful completion of multiple steps, many originating in the interventional arena. Learning to implant an LV lead by application of an existing electrophysiology (EP) skill set and tools can be a long, painful, and humiliating process. Once learned, the EP approach has limited success, even in experienced hands. Because an interventional approach is better suited to the procedure, learning to implant an LV lead is usually faster, less painful, and more satisfying despite the requirement to first learn a new skill set and tools. Subsequently, application of the interventional approach can increase implant success from 88% to 92% with the EP approach to 98% with the interventional approach.¹¹ This chapter takes the position that it is better to learn a new, unfamiliar skill set than to continue with the familiar that may not be best suited to the procedure (Box 23-1).

Box 23-1
Interventional Mind-Set Approach to Problems Encountered During Device Implantation

1 Good work cannot be done if you are in an uncomfortable position; you owe it to your patients to insist that the room be set up properly.

2 It is important to be alert to new tools that can make difficult cases easier.

3 Contrast is essential to success.

4 Risk of contrast nephropathy is patient specific.

5 Contrast can be used safely in most patients if pretreated for contrast nephropathy.

6 There is (or should be) a preshaped catheter to locate every vascular structure.

7 If the first catheter does not work, try another shape or create a shape.

8 Catheter manipulation requires both hands on the catheter.

9 The assistant should inject contrast so the operator can focus on catheter control.

10 Catheters must not be bent before they enter the patient because every bend in a catheter reduces control.

11 Almost “all” vascular occlusions can be crossed one way or another.

12 Almost “all” vascular occlusions can be dilated with a balloon.

13 All surgical procedures can be done better with wires, catheters, and balloons.

14 Extra-support wires are essential for advancing catheters through difficult anatomy; the stiffer the better.

15 Guide support is essential for successful balloon dilation.

Morbidity and Mortality

Does the application of an interventional skill set specific to device implantation really reduce morbidity and mortality? Many examples show this may be the case, but the best example is sending a patient for an epicardial lead because the implanting physician does not use guide support or perform venoplasty. Even in the most experienced hands, mortality is doubled (4.8% surgical vs. 2.5% transvenous; P = 0.46), and acute renal injury and infection are quintupled (26.2% vs. 4.9%: P = .0004; and11.9% vs. 2.4%; P = .03, respectively).¹² In practice, results may be worse. Surgical LV lead mortality from the REPLACE registry¹³ was greater than 8%. There were four deaths from among the 48 patients (11% of 434 attempted LV lead placements) who went for an epicardial lead following a failed transvenous approach. The 8% mortality assumes all 48 patients went to surgery, although it is not unusual for patients either to decline a surgical lead or to be rejected as too risky; thus the mortality may be even higher. Interventional techniques safely increase implant success, reducing the need for surgical epicardial leads.

Device Implantation–Specific Interventional Skill Set

Application of an interventional skill set specific to device implantation can improve patient satisfaction (one incision not two), reduce complications (avoid extraction or surgery), reduce implant time, and reduce overall mortality. With the assumption that the above is true, physicians implanting devices need to have or develop these skills to provide the best possible patient care. EP training programs should include opportunities to observe and learn device-specific interventional techniques as part of the curriculum. Opportunities for education in interventional device implantation techniques can be developed by attending educational programs or working with interventional cardiologists or interventional radiologists. Once it becomes clear that the application of an interventional skill set specific to device implantation really does reduce morbidity, professional societies will promote the importance of the “interventional skills specific to device implantation” (knowledge base and technical skills) and support education and training in the area.

We define a skill set as the combination of knowledge base and technical skills. Part of the interventional device implantation skill set involves basic interventional knowledge and technical skills unique to device implantation. A physician with formal interventional training in interventional cardiology or radiology may help provide the knowledge and technical skills necessary for device implantation. Because the terms, tools, and techniques used in the interventional approach to device implantation may be unfamiliar, a glossary box is provided for reference. See also the Interventional Implant Equipment List and manufacturers at the end of Chapter 22 and online.

Glossary and Definition of Terms

LV lead delivery system is defined as the set of catheters used to place an LV lead in a coronary vein. The most effective delivery system consists of three telecopying components: 1, the coronary sinus (CS) access catheter; 2, the delivery guide; and 3, the vein selector.

Coronary sinus (CS) access catheter is defined as a removable catheter designed to cannulate the CS and provide access and support for delivery of a left ventricular (LV) lead to the target vein. Delivery guides are intended to be advanced through a CS access catheter. The lumen size of the CS access catheter determines subsequent implant options. The lumen of a device company CS access catheters is 7 French (7F) or smaller, which restricts the ability to add a CS support wire while working close the CS os, and other advanced techniques. There are no device company delivery guides for 6F leads because they require at least an 8F lumen in the CS. The SafeSheath CSG Worley provides a 9F lumen in the CS, expanding options, including a delivery guide for leads a large as 7F.

Delivery guide is defined as a sliceable catheter designed to fit into the target vein and provide direction and support for advancing the LV lead. Delivery guides are not intended for CS cannulation. In the opinion of the authors, the device company delivery guides have two important limitations: (1) they are too small to deliver the many 6F leads currently available, and (2) by providing several shapes to try and match the venous anatomy, device company delivery guides are intended to locate and cannulate the target vein and deliver the lead. In the authors’ experience, it can be difficult if not impossible to locate, insert a wire, and/or cannulate the target vein without the assistance of a vein selector.

Vein selector is defined as a small (5 French, 5F), soft-tip catheter that telescopes inside a delivery guide to extend beyond the delivery guide and locate the target vein using puffs of contrast, provide direction and support for advancing wires into the vein, then serve as a rail over which to advance the delivery guide. None of the device companies offers vein selectors, relying on their delivery guides to act as both vein selector and delivery guides. In the authors’ experience, there are many situations where the delivery guide alone is not sufficient, and the only way to insert the delivery guide into the vein is to use a vein selector inside the guide.

Extra-support wires. Advancing a balloon, catheter, or sheath over a stiffer wire may be necessary to prevent buckling. We find the .035-inch Amplatz Extra Stiff (Cook) suitable in many cases, but on occasion the .035-inch Amplatz Ultra Stiff (Cook) is required. Currently, the Ultra is only available in the cumbersome length of 260 cm. The Amplatz wires are also available in .032-inch size, which may be required for some sheaths. The Amplatz wires are stiff and do not advance easily through tortuous or narrow venous structures; thus they are inserted via an exchange procedure using a small catheter.

Exchanging of wires to augment support. When a more supportive wire (e.g., Amplatz) is required to advance the guide/sheath, a small catheter (4F-5F) is advanced over the existing wire into the pulmonary artery or inferior vena cava, the existing wire removed, the Amplatz inserted, and the exchange catheter removed. A hydrophilic 4F to 5F catheter will advance where a catheter with a standard surface will not, so it is important to have hydrophilic catheters on hand for exchange. To avoid the need for exchange-length wires, the catheter should be 60 to 70 cm in length, but this length may not be readily available. Thus, we often cut the hub and 30 to 40 cm off a 100- to 130-cm catheter once the less supportive wire is removed.

Focused-force venoplasty. The addition of a stiff wire beside the inflated balloon focuses the force of the balloon against the occlusion. Focused force is used for both focal and diffuse occlusions.

Hydrophilic wires/catheters and balloons. Materials that are intrinsically hydrophilic or have a hydrophilic coating are slippery to the touch when wet and offer much less resistance to passage through vascular structures than standard materials of the same size and configuration. Their disadvantage is that hydrophilic wires/catheters can be difficult to handle and direct.

“Push-pull” technique is used to advance the tip of a delivery guide into the ostium of the target vein. With the tail of the balloon at the tip of the guide, advance the guide (push), holding traction on the balloon as it is deflated (pull).

Knowledge Base

The knowledge base of an implantation-specific interventional skill set includes equipment required for the procedure, the importance of contrast, patients at risk for contrast nephropathy, use of preprocedure hydration for safe use of IV contrast, and the importance of table position for maintaining focus on the procedure. Other areas include open-lumen catheter manipulation (keeping both hands on catheter) and wire exchange, preshaped guiding catheters used to cannulate specific venous structures, and the importance of having the assistant inject contrast while the operator keeps both hands on the catheter. Interventional implanters should know type and size of balloons to use for which veins, how to prevent hemothorax during subclavian venoplasty, which tools to use for crossing a venous obstruction, which implant problems respond to the balloon anchoring technique and which to the snare technique, and how sacrificing a lead, using a wire under the insulation, and snaring can be used to regain venous access.

Technical Skills

Technical skills in an interventional skill set include torque control using both hands on the catheter, catheter manipulation while contrast is injected by the assistant, vein-specific catheter techniques (specific preshaped catheter used a specific way for a specific vein), and techniques to gain and optimize and maintain guide support. Along with deploying balloons to serve as anchors, implanters must know techniques for crossing venous obstruction associated with device leads (wire manipulation veins and venoplasty of stenotic veins) as well as venoplasty of stenotic or occluded cardiac vein structures in patients with and without prior open-heart surgery.

Training

Aggarwal and Darzi ¹⁴ discuss how traditional EP and implanting physicians can become trained in the device implantation–specific interventional skill set. Their editorial “Technical skills training in the 21st century” addresses this issue as it relates to such areas as laparoscopic surgery, bronchoscopy, and colonoscopy. They describe proficiency-based training in which the environment can be modeled to simulate the experiences encountered and to generate feedback about both technical skills and knowledge base. Together, physicians who have adopted the interventional approach, device manufacturers, and professional societies can create a program to help the traditional EP physician develop the knowledge base and skill set specific to device implantation.

Prevention of Contrast Nephropathy

Use of Contrast Material

The interventional mind-set approaches implant problems with the following attitude about contrast:

1 Contrast is essential.

2 Safety of contrast is patient specific.

3 Safe use of contrast requires advanced patient preparation.

4 Most patients with a history of heart failure can be hydrated safely.

5 Renal failure is more difficult to treat than volume overload.

When considering the use of contrast for LV lead placement, keep in mind that a successful implant not only improves symptoms, but also reduces morbidity and mortality.¹⁵ Although uncommon in most situations,^16,¹⁷ contrast nephropathy can be an important complication of CRT associated with increased morbidity and mortality and extended hospital stay.¹⁸ Patients with congestive heart failure and preexisting renal insufficiency are at increased risk for contrast nephropathy,¹⁹ but ultimately, CRT improves renal function by improving cardiac function.²⁰ In fact, patients with moderate renal insufficiency may derive the greatest benefit from successful CRT.²¹

Recognizing the importance of contrast to a successful procedure, the interventional mind is proactive, always looking for ways to reduce risk,²² whereas the EP mind-set focuses on reducing the use of contrast. Despite every effort to limit its use, the volume of contrast frequently exceeds expectation. Further, the nephrotoxicity of even a small volume of contrast (10-30 mL) in the unprepared patient can be significant, whereas nephropathy can be reduced or eliminated if preventive steps are taken before the implant. Thus, it is important for implanting physicians to adopt the interventional mind-set and take a proactive approach to contrast nephropathy rather than simply trying to limit its use.

After exposure to contrast, the kidneys concentrate contrast in the urinary space within the renal tubules, releasing nitric oxide from endothelial cells, triggering a transient vasodilation, followed by more prolonged vasoconstriction, and causing tubular cell damage, extravasation into the peritubular space, and constriction of the lattice-like peritubular blood vessels in the outer medulla. Sustained vasoconstriction can last for hours to days, resulting in ischemic injury to the outer medulla, particularly in those with chronic kidney disease and diabetes mellitus ²³ (Box 23-2).

Contrast-induced nephropathy (CIN) is typically defined as a 25% or greater increase in baseline serum creatinine, or a 0.5-mg/dL increase without another identifiable cause. CIN occurs 24 to 48 hours after exposure, with serum creatinine peaking at 3 to 5 days, returning to normal within 2 weeks, although usually by 7 to 10 days. The approach to the prevention includes (1) hydration to dilute and flush contrast from the kidney, (2) selection of less nephrotoxic contrast agent, (3) drugs to protect the kidney and prevent vasoconstriction, and (4) hemofiltration or hemodialysis.

A bedside risk score stratifies patients into low (0-7 points), medium (8-14), and high-risk (≥15). The score is calculated as follows: age 80 or older (2 points), female (1.5), diabetes (3), urgent (PCI) (2.5), emergent PCI (3.5), congestive heart failure (4.5), serum creatinine of 1.3 to 1.9 mg/dL (5) or 2 mg/dL or greater (10), and pre-PCI use of intra-aortic balloon pump (13). Based on the score, high-risk patients can be identified for early administration of more aggressive and intensive prophylaxis.^24,²⁵

Withdrawal of Nephrotoxic Drugs

Common nephrotoxic drugs include nonsteroidal anti-inflammatory drugs (NSAIDs), metformin, diuretics (e.g., furosemide), angiotensin-converting enzyme (ACE) inhibitors, aminoglycosides, sulfonamides and penicillin, amphotericin, cyclosporin A, vancomycin, and cisplatin. These agents should be withdrawn before contrast media administration in all patients at risk. Metformin is the most important because it can produce intramedullar metabolic acidosis, which promotes nephropathy. Almost all patients can tolerate suspension of diuretics on the day of the implant procedure.

Periprocedural Hydration

Hydration to dilute and flush contrast from the kidney is the most important step in the prevention of CIN. Hydration has two parts: (1) the fluid used: half-normal saline, normal saline, or bicarbonate, and (2) the protocol: (a) “overnight” (12 hours before and 12 hours after) or (b) “bolus” (3 mL/kg 1 hour before and 1-1.5 mL/kg 4-6 hours after procedure).

Hydration Fluids

Hypotonic Saline

A 0.45 normal saline (NS) solution (in 5% glucose) should not be used; it is less effective than isotonic saline. In a study of 1383 patients, CIN was 2.0% with 0.45 NS versus 0.7% with isotonic saline.²⁶

Isotonic Saline

Multiple clinical trials confirm that NS definitively reduces CIN. For example, Solomon et al.²⁷ reported that with saline hydration, “There is little risk of clinically important nephrotoxicity attributable to contrast material (122 ± 90 mL) for patients (220) with diabetes and normal renal function or for nondiabetic patients with preexisting renal insufficiency. The risk for those with both diabetes and preexisting renal insufficiency is about 9%, which is lower than previously reported.” None of their patients required dialysis.

Sodium Bicarbonate

A 2004 study suggested that sodium bicarbonate was superior to saline hydration,²⁸ although the hydration protocols were not the same. Subsequently, five published randomized clinical trials and three meta-analyses have provided conflicting results.²⁹^–³¹ Interpreting the data requires recognizing that in three of the six published studies (and several abstracts), the hydration protocol for saline and bicarbonate were not the same; thus the difference seen may reflect the effect of the infusion protocol rather than the infused solution. Only three published studies used the same infusion protocol.³²^–³⁴ The smaller studies found bicarbonate superior to saline,^33,³⁴ whereas the larger study found no difference.³²

Hydration Protocol

There is no direct comparison of overnight versus bolus infusion. However, analysis of the bicarbonate versus saline trials suggests bolus hydration is superior to overnight hydration, particularly in patients with congestive heart failure (CHF). When overnight saline was compared to bolus bicarbonate, saline was reduced for CHF patients in two studies ^35,³⁶ (not defined by Merten et al.²⁸). In the bicarbonate arm, the loading dose (3 mL/kg/hr for 1 hour) was not adjusted, but the infusion (1 mL/kg/hr during and 6 hours after procedure) was reduced to 0.5 mL/kg in one trial.³² Bicarbonate was superior to saline in the two studies where bicarbonate was not reduced, but equal to saline when the bicarbonate infusion was reduced for CHF.

These results suggest that reducing the dose of overnight saline results in less effective hydration than bolus hydration, provided it is not adjusted for CHF. For a 70-kg person, the volume of the unadjusted bolus infusion protocol is 620 mL, whereas the overnight infusion protocol (reduced for CHF) is 840 mL; thus the bolus protocol is superior to overnight hydration, particularly in patients with CHF. Our recommendation therefore is to avoid overnight hydration and use acute hydration (3 mL/kg) starting 1 hour before the procedure, then either 1 mL/kg during and 6 hours after the procedure or 1.5 mL/kg for 4 hours. Another advantage of bolus hydration is that it can be started shortly before the procedure.

Volume of Contrast Media

Although studies show that the risk of CIN is dose dependent, there does not appear to be a threshold value below which CIN does not occur. Patients with preexisting renal dysfunction and diabetes appear to be at highest risk for CIN. Retrospective studies of cardiac catheterization suggest a lower risk of CIN for contrast loads less than 100 mL for interventional procedures.

Choice of Contrast Agent

Types of Iodinated Contrast Agents

All contrast agents consist of a benzoic acid molecule with three atoms of iodine replacing hydrogen atoms on the benzene ring. Classification is based on (1) the charge on the iodinate molecule (ionic vs. nonionic), (2) osmolarity, and (3) molecular structure (monomer vs. dimer). The osmolality of the contrast agents is a measure of the number of particles in solution. The original contrast agents were ionic monomers and very hypertonic (osmolality of metrizoate = 2100), whereas newer contrast agents were nonionic and less hypertonic (osmolality of iopamidol = 796). Thus, ionic metrizoate was called “high osmolar,” referring to its osmolality; the terms high osmolar and ionic were used interchangeably. Currently, the term “high osmolar,” referring to the high osmolality of ionic agents, has no meaning because the osmolality of ionic agents such as ioxaglate (580) are the same or lower than for nonionic agents. More important (and confusing), the term “low osmolar” now refers to an agent with osmolality higher than 290. At present, the higher the osmolality, the more “low osmolar” is the agent, which is the opposite of the original description. By modern convention, iodixanol (osmolality of 290) is “iso-osmolar” and all agents greater than 290 are “low osmolar,” regardless of whether they are ionic or nonionic. The higher the osmolality, the more “low osmolar” it becomes. For example, ionic ioxaglate (osmolality of 580) is “low osmolar” compared to nonionic iodixanol (290). If one used the previous nomenclature, ioxaglate would be both “high osmolar” (because it is ionic) and “low osmolar” because it has a higher osmolality than iodixanol. Do not use the term “high osmolar” in relation to contrast.

The osmolality of nonionic agents follows: iodixanol 290, ioxilan 695, iopromide 774, iopamidol 796, and iohexol 884 mOsm/kg. Iodixanol is iso-osmotic, and all the rest are “low osmolar.”

Comparison of Contrast Agent Nephrotoxicity

Ionic vs. Nonionic

One randomized prospective evaluation of ionic diatrizoate (measured osmolality = 1500) vs. nonionic iopamidol (osmolality 796) found no difference in the incidence of nephrotoxicity.³⁷ However the subsequent RECOVER study compared ionic, “low-osmolar” ioxaglate (osmolality 580) to nonionic, iso-osmolar iodixanol (osmolality 290) in patients with renal insufficiency undergoing coronary angiography with or without PCI.³⁸ In addition to ionic versus nonionic, a second variable was “low osmolar” (580) versus iso-osmolar (291). The incidence of nephropathy was significantly lower with iso-osmolar nonionic iodixanol (7.9%) than with “low osmolar” ionic ioxaglate (17.0%) (P = .021). Unfortunately, some patients received hydration with 0.45 NS (ineffective; see earlier), and thus the difference may be caused by inadequate hydration. Further, the findings may also reflect the difference in osmolality.

Low-Osmolar Nonionic vs. Iso-Osmolar Nonionic

The NEPHRIC Study compared low-osmolar iohexol (osmolality = 884) with an iso-osmolar iodixanol (osmolality 290) and found nephropathy less likely to develop in high-risk patients with iso-osmolar iodixanol.³⁹ Because NEPHRIC was small and hydration not uniform, and because several subsequent studies were flawed and produced conflicting results, the CARE trial was conducted to settle the issue. The Cardiac Angiography in Renally Impaired Patients study was a prospective, multicenter, randomized, double-blind comparison of the “low osmolar” nonionic iopamidol (osmolality 796) to the iso-osmolar nonionic iodixanol (osmolality 290) in high-risk patients.⁴⁰ CIN, defined by multiple endpoints, was not statistically different in high-risk patients, with or without diabetes mellitus. All patients received prophylactic volume expansion with isotonic sodium bicarbonate solution, administered at 3 mL/kg/hr for 1 hour before angiography, and at 1 mL/kg/hr during and for 6 hours after angiography. Prophylactic N-acetylcysteine regimen of 1200 mg twice daily administered on the day before and on the day of the study procedure was used in some centers. The authors concluded that any true difference between the agents was small and unlikely to be clinically significant. Thus, if bolus hydration is used, either nonionic iso-osmolar iodixanol or nonionic low-osmolar iopamidol can be used. The conflicting results of NEPHRIC and CARE may reflect the approach to hydration.

In summary, adequate hydration with saline or bicarbonate (3 mL/kg load, then 1 mL/kg for 6 hours) apparently reduces the difference (if any) among the different agents. When hydration is suboptimal, the nonionic agents, particularly those with an osmolality close to isotonic (iodixanol osmolality = 290) may be superior.

Gadolinium

Although they may be less nephrotoxic than iodinated contrast agents, gadolinium-based contrast agents should never be used because of their association with nephrogenic systemic fibrosis, a relatively recently recognized,⁴¹ rapidly progressive fibrosing disorder of skin and internal organs. Nephrogenic systemic fibrosis is seen in patients with kidney disease (estimated glomerular filtration rate <30) who receive gadolinium-containing contrast agents.⁴²

Carbon Dioxide

For more than five decades, gaseous CO₂ has been recognized by interventionalists as an alternative to iodinated contrast for diagnostic as well as interventional procedures.^43,⁴⁴ Winters et al.⁴⁵ recently described their favorable experience with gaseous CO₂ venography rather than iodinated dye in patients undergoing pacemaker or ICD lead revisions.

Drugs to Prevent Renal Failure

Iloprost

A prostacyclin analogue, iloprost works “presumably as a renal vasodilator and cellular protective agent downstream in the prostaglandin cascade to prevent contrast-induced acute kidney injury.”⁵⁰ In a randomized, double-blind, placebo-controlled study of 208 patients with a serum creatinine of 1.4 mg/dL or greater, Spargias et al.⁵¹ reported CIN in 22% of controls and 8% of the iloprost group (1 ng/kg/min). All patients were hydrated with saline. Although dose-dependent hypotension and platelet inhibition are the principal side effects of iloprost, the incidence of hypotension and bleeding was not significantly different between groups.

Hemofiltration and Hemodialysis

In patients with a creatinine greater than 2 mg/dL, hemofiltration (4 hours before and continued for 24 hours after the procedure) compared to isotonic saline prevented the deterioration of renal function, decreased the need for renal replacement therapy, and improved in-hospital and long-term outcomes.⁵² Similarly, in patients with a creatinine more than 3.5 mg/dL, hemodialysis (a single, 4-hour treatment initiated immediately after procedure) reduced length of stay and the need for renal replacement therapy at hospital discharge.⁵³

Treatments to Avoid

Fenoldopam (systemic IV administration), dopamine, calcium channel blockers, atrial natriuretic peptide, and l-arginine are not effective, whereas furosemide, mannitol, and endothelin receptor antagonists are potentially detrimental.⁵⁴

We have successfully adopted the following reasonable approach. Because patients with CHF are at increased risk and the serum creatinine levels of patients with New York Heart Association (NYHA) Class III or IV CHF can vary from day to day, we pretreat all patients undergoing a CRT implant, as follows:

1 Withdraw nephrotoxic drugs.

2 Bolus hydration with either isotonic saline or bicarbonate, 3 mL/kg/hr for 1 hour before, then 1 mL/kg/hr (consider 0.5 mL/kg/hr for recent CHF decompensation) during, and for 6 hours (or 1.5 mg/kg/hr for 4 hours) after the procedure. Because the total volume of intravenous (IV) hydration is lower with bolus hydration and the results possibly better, we no longer recommend overnight hydration, particularly for those with CHF.

3 Consider iloprost (±)

4 Use either iso-osmolar iodixanol or iopamidol.

5 Consider hemofiltration and hemodialysis in extremely high-risk patients (see Brown risk score earlier).

Additional Concerns

No data suggest that shellfish allergies predict increased risk of adverse reactions to contrast. It is currently thought that shellfish allergy is related to tropomyosin, and patients with seafood allergies do not have an increased risk of iodine allergy.

A variety of regimens are used to prevent allergic reactions to iodine. Specific regimens will vary from center to center. Preprocedure medications include diphenhydramine (Benadryl), a histamine receptor blocker, and steroids beginning 12 hours before the procedure. Typically, prednisone or methylprednisolone is administered 12 hours and immediately before the procedure.

Preimplant Hydration

Preimplant hydration is discussed earlier.

Conclusion

Implanting physicians who are not accustomed to preimplant hydration are extremely concerned that CRT patients will suffer CHF decompensation. Thus they avoid hydration, increasing the risk of nephrotoxicity that can occur even when small volumes of contrast are used. Our experience with routine hydration for device implantation does not support the level of concern frequently expressed. Further, many CRT patients are hydrated for their interventional procedures (e.g., cardiac catheterization and PCI) without acute decompensation. Finally, there is the risk/benefit ratio of hydration to prevent CIN versus the possibility of exacerbating CHF. Contrast nephropathy results in an increased length of stay, higher morbidity, and both short-term and long-term mortality. Contrast nephrotoxicity is reduced if not eliminated by hydration. With the new, acute bolus approach to hydration, the total volume of IV hydration is lower, and the patient is under observation during the daytime hours. CHF may or may not develop as a result of hydration and can be treated if it does; thus hydration should be employed (Box 23-3).

Box 23-3
steps to prevent contrast nephropathy

1 Hold diuretics on the day of the procedure.

2 Preimplant hydration to prevent contrast nephropathy: NaCl vs. NaHCO₃ (probably no advantage of one over the other)

Recommendations:

a 3 mg/kg for 1 hour before procedure

b 1 mg/kg during and for 6 hours after procedure, 0.5 mL/kg if recent CHF exacerbation

3 Contrast agents: in general, contrast agents with osmolality closer to isotonic (≈290) seem to be superior to agents with high osmolality (>500) in patients with diabetes mellitus and chronic renal failure. However, isotonic iodixanol and iopamidol (osmolality = 796), seem to be equivalent.

Preparations for Implantation

Room Setup and Table Position

The equipment required for the procedure needs to be on hand in the room, including the appropriate implant table (Fig. 23-1). The table and the assistant need to be in the appropriate position (Fig. 23-2). If the monitor is not in a comfortable position, mount a flat-screen monitor on an IV setup pole.

Figure 23-1 Implant table designed for cardiac resynchronization therapy.

A, Skewed view; B, side view. The table is designed to be in the T-bone position for dealing with subclavian obstructions and during left ventricular lead implantation. The legs are set back to allow the image intensifier rotate under the table when imaging in the right anterior oblique projection. In addition, there is space between the legs of the implant table and the base of the patient table for the fluoroscopy pedals.

(Courtesy Oscor, Palm Harbor, Fla.)

Figure 23-2 Importance of table position while working with long wires and catheters.

A, Implant equipment table is in its usual position behind the operator. Wires and catheters are bent 90 degrees as they exit the pocket, making them prone to fall off the table. The 90-degree bend makes open-lumen catheters prone to kink, resulting in collapse of the lumen, destroying the function of the catheter. The 90-degree bend also cuts torque control of the catheter by 50%, making it more difficult to cannulate the coronary sinus or target veins. Wire exchanges are difficult to perform. B, Table is perpendicular to the patient table. The catheters and wires fall naturally on the table. The operator and assistant are not distracted from the procedure by trying to keep the wires from falling off the table and becoming contaminated. Open-lumen catheters are less likely to kink, and torque control is optimal. Wire exchanges are easily performed by pinning the wire to the table and sliding the catheter back to the hand pinning the wire.

Catheter Manipulation and Contrast Injection

Electrophysiology physicians are used to working with electrode catheters that have almost infinite torque control and do not kink or twist as do open-lumen catheters. As a result, keeping the catheter straight before it enters the body and applying torque with both hands to distribute the force are not as essential as with open-lumen catheters. In addition, we become accustomed to working alone with our EP catheter, so when contrast needs to be injected, it is not the EP mind-set to do it alone. To work effectively with open-lumen catheters and inject contrast, the approach needs to change from an EP to interventional simply because the interventional approach to catheter manipulation and contrast injection is the way the tools were designed to be used (Fig. 23-3)

Figure 23-3 How to torque an open lumen catheter and inject contrast.

A, Operator is attempting to control the catheter and inject contrast simultaneously. B, Operator has both hands on the catheter. The assistant can inject contrast on request of the operator. Interventional principles dictate that both hands must be on the catheter for effective catheter manipulation. Using both hands spreads the torque over a larger area, reducing the chance the lumen will collapse, destroying the catheter. The addition of the Y adapter with hemostatic valve and rotating hub makes it much easier to hold the catheter in position and insert a wire when needed without loss of catheter position. When the operator attempts to inject contrast and manipulate the catheter, two events sabotage the result: the operator must redirect focus from the tip of the catheter to the syringe, and catheter position is compromised because the plunger hand no longer is in control of the catheter.

Balloon Basics

Type of Catheter for Balloon Mounting

Balloon catheters are either “over the wire” (OTW) or rapid exchange (Fig. 23-4). The terms rapid exchange and monorail are synonymous. OTW coronary balloons are about 150 cm and thus require a 300-cm wire, which is very difficult to handle. We always use a rapid-exchange coronary balloon that requires a standard-length wire. Peripheral balloons are 40 to 60 cm; thus an OTW peripheral balloon uses a standard-length wire, which makes rapid-exchange models unnecessary. When balloons are made specifically for coronary venoplasty, they will be short enough to be OTW and still use standard-length wires.