Cardiovascular

Transcatheter aortic valve replacement: New hope for patients with aortic stenosis

If you care for patients with cardiac valve problems, perhaps you’ve heard of a new procedure to treat aortic stenosis (AS). In this condition, the aortic valve narrows and fails to open completely during systole, impeding blood flow from the left ventricle to the arteries. A progressive disease, AS typically occurs after age 70. (See All about aortic stenosis by clicking the PDF icon above.)

Once the patient experiences signs and symptoms and shows measurable functional decline, survival is poor. Up to 50% of patients with significant comorbidities die within 1 year. Traditional treatment options include surgical valve replacement, balloon valvuloplasty, and medical management. However, many elderly AS patients have multiple comorbidities and are considered inoperable or extremely high-risk surgical candidates.

But a procedure called trans­catheter aortic valve replacement (TAVR) recently has emerged as a less invasive option for some of these patients. Available commercially in the United States as well as in clinical trials, TAVR may be an option for patients unable to tolerate the sternotomy, aortotomy, and cardiopulmonary bypass of traditional surgical valve replacement. The Food and Drug Administration (FDA) recently approved the Edwards Lifesciences SAPIEN® aortic bioprosthetic valve system for use in TAVR. (See SAPIEN valve and CoreValve by clicking the PDF icon above.) The SAPIEN system is the only device approved for patients who aren’t eligible for surgery using the transfemoral (TF) or retrograde approach. According to current label recommendations, the SAPIEN valve is restricted to patients deemed inoperable by a board-certified cardio­thoracic surgeon.

Other treatment options are available in the clinical trials of PARTNER II and CoreValve studies. Both studies are investigating alternative approaches to the TF route, as most TAVR candidates have poor femoral access. These approaches include the transapical (TA) approach with the SAPIEN valve and the subclavian arterial approach with the CoreValve® by Medtronic.

Evaluation

Once diagnostic testing is completed, the patient meets with a cardiologist and a cardiothoracic surgeon to determine treatment options. For clinical guidelines on patient eligibility for commercial TAVR, see Criteria for TAVR by clicking the PDF icon above. However, depending on available treatment options (including investigational options), guidelines may vary.

TAVR procedure

Commercial TAVR with the SAPIEN valve has been approved for the TF approach, which requires a minimal femoral/iliac arterial lumen size of 7 mm to accommodate the delivery system (which uses 22F or 24F catheters). The medical team must determine the degree of femoral calcification and tortuosity. The procedure is done with general anesthesia in a hybrid catheterization laboratory (one that can serve as both a cath lab and an operating room). The medical team includes an interventional cardiologist, a cardiothoracic surgeon, an echocardiography technician, a perfusionist, a respiratory therapist, and an anesthesiologist. Central line access, including an arterial line for blood pressure monitoring, is obtained through femoral and jugular sites. Temporary pacing wires are inserted for demand-pacing of the right ventricle during valvuloplasty and transcatheter valve deployment.


Before valve placement, balloon valvuloplasty is done to dilate the native aortic valve. The trans­catheter valve is inserted into a femoral artery, then passed through the aorta (including the descending aorta, aortic arch, and ascending aortic arch) and into the native aortic valve location. Once valve placement has been determined with transesophageal echocardiography (TEE) and fluoroscopy, the right ventricle is paced rapidly (180 to 200 beats/minute) while the trans­catheter device is deployed. Rapid pacing decreases cardiac output, which lowers the risk of valve displacement into the aorta. Aortic pressures, ejection fraction, and paravalvular leakage are assessed before the procedural catheters and sheaths are removed.

Transapical TAVR approach

The TA approach remains investigational for the SAPIEN system. TA-TAVR is done in a hybrid operating-room suite using general anesthesia. A central line is placed, arterial access is obtained, and pacing wires are inserted. A mini­thoracotomy is performed at the fifth or sixth intercostal space to expose the left ventricle. Purse-string sutures are placed in the left apex, followed by echocardiography-guided placement of guide­wires and catheter-sheath delivery devices. Then balloon valvuloplasty is performed, and the stent device is inserted directly through the apex. Once TEE and fluoroscopy confirm placement, the device is deployed.

Before the catheters are removed, the surgical team evaluates valve function. Then the delivery system is removed, purse-string sutures are tied down, a chest tube is inserted, and the incision is closed.

CoreValve procedure

The Medtronic CoreValve can be placed using the TF or transaortic approach. In patients with inadequate femoral access, the transaortic approach has been done via the subclavian artery in operating-room settings. The surgeon exposes the subclavian/axillary artery and punctures the artery using a purse-string suture. The transcatheter device is passed through the subclavian artery into the aortic arch and then the ascending aorta, just below the brachiocephalic artery. Although initially done with general anesthesia, this procedure now involves local anesthesia along with a mild systemic analgesic when possible.

Postoperative nursing considerations

Patients who undergo TAVR are admitted to the intensive care unit (ICU) overnight for close vital-sign monitoring, possibly with ventilatory weaning and access-site monitoring. Monitor for bleeding at the groin site in a patient who’s had the TF approach; monitor for bleeding at chest sites in one who’s had the TA or transaortic approach.

Once stable, patients are extubated before or soon after leaving the procedure room. Those who’ve had the TF procedure may be transferred to a stepdown unit the next day if their condition allows. Monitor for hematomas at insertion sites. Once they’ve been transferred to a telemetry unit, patients are ambulatory and should stay on that unit. Promote ambulation as soon as possible.

Complications

Stay alert for postprocedural arrhythmias, such as varying degrees of heart block and ventricular arrhythmias. Severe arrhythmias may warrant pacemaker or defibrillator implantation. Monitor for signs and symptoms of stroke (such as altered mental status, slurred speech, and vision changes), which may result from embolization of calcific material during valvuloplasty before valve implantation. Treatment for suspected stroke must begin immediately. Other potential complications include incisional bleeding, myocardial infarction, paravalvular or transvalvular leakage, heart failure, infection, and death.

Patients who’ve undergone TA-TAVR typically have longer ICU and hospital stays. Because they’ve had minithoracotomies, they require chest tubes postoperatively. Be sure to provide effective pain management. Evaluate breath sounds and pulse oximetry for indications of pneumothorax or hemothorax, atelectasis, and effusions. To help detect stroke, compare neurologic exam findings with baseline results. Watch for indications of incisional bleeding by monitoring hematocrit, hemoglobin, and vital signs. Monitor renal function by assessing fluid intake and output and serum creatinine levels. To check for decreased peripheral perfusion of the legs, assess pulses, color, and temperature of all extremities.

Discharge teaching

Before discharge, the patient undergoes echocardiography to measure pressure gradients and check for a paravalvular or transvalvular leak. Caution patients who’ve had TF-TAVR to avoid lifting 10 lb or more for at least 5 to 7 days. Instruct them to keep follow-up cardiologist appointments, and advise them they’ll need to undergo echocardiography about 1 month after the procedure. Teach them about prescribed medications, which typically include aspirin and clopidogrel; the latter is recommended for up to 6 months when used solely to prevent complications of valve replacement.

Provide information about the risk of subacute bacterial endocarditis. Instruct patients to avoid elective dentistry for 3 months after the procedure, and teach them about the need for prophylactic antibiotics (as recommended by current guidelines of the American Heart Association).

Additional postdischarge needs depend on the patient’s postoperative response. Some patients may need to continue physical therapy at home after discharge or may require a short stay in a rehabilitation facility.

Toward the future

Researchers continue to seek alternative TAVR routes in patients with poor femoral arterial access. TAVR continues to be evaluated in clinical trials and registries. Researchers are investigating whether it can be used in patients who’ve undergone previous aortic valve replacement, possibly creating a valve-in-valve TAVR. For now, finding the most appropriate procedure for each patient with AS entails extensive testing and collaboration among clinical team members.

Selected references

Bates ER. Treatment options in severe aortic stenosis. Circulation. 2011 Jul 19;124(3):355-9. DOI:10.1161/CIRCULATIONAHA.110.974204.

Cleveland Clinic. Heart Valve Disease: Percutaneous Interventions. 2012. http://my.clevelandclinic.org/heart/percutaneous/percutaneousvalve.aspx. Accessed March 21, 2012.

Cockburn J, Trivedi U, Hildick-Smith D. Transaortic transcatheter aortic valve implantation within a previous bioprosthetic aortic valve replacement. Catheter Cardiovasc Interv. 2011 Sep 1;78(3): 479-84. doi:10.1002/
ccd.23044.

Dworakowski R, Wendler O. The transapical route for TAVR. Card Interv Today. 2011 Sep-Oct;62-5.

Gerckens U, Mueller R, Iversen S, et al. Trans-aortic implantation of the Medtronic CoreValve prosthesis. Successful implantation through an alternative access route. J Am Coll Cardiol. 2010 Mar 9;55(10A):A217.E2055. doi:10.1016/S0735-1097(10)62056-6.

Leipsic J, Wood D, Manders D, et al. The evolving role of MDCT in transcatheter aortic valve replacement: a radiologist’s perspective. AJR Am J Roentgenol. 2009 Sep;193(3): W214-9. www.ajronline.org/content/193/3/W214.full?sid=b8efed4c-1114-461d-953b-f11416534715. Accessed March 21, 2012.

Leon MB, Smith CR, Mack M, et al; PARTNER Trial Investigators. Transcatheter aortic-valve implantation for aortic stenosis in patients who cannot undergo surgery. N Engl J Med. 2010 Oct 21;363(17):1597-607.

McRae ME, Rodger M, Bailey BA. Transcatheter and transapical aortic valve replacement. Crit Care Nurse. 2009;29(1):22-36. doi:10.4037/ccn2009553.

Petronio AS, DeCarlo M., Bedogni F, et al. Safety and efficacy of the subclavian approach for transcatheter aortic valve implantation with the CoreValve revalving system. Circ Cardiovasc Interv. 2010 Aug;3(4):359-66. DOIi:10
.1161/CIRCINTERVENTIONS.109.930453.

Svensson LG, Dewey T, Kapadia S, et al. United States feasibility study of transcatheter insertion of a stented aortic valve by the left ventricular apex. Ann Thorac Surg. 2008 Jul;86(1):46-54.

Tommaso CL, Bolman RM 3rd, Feldman T, et al. SCAI/AATS/ACCF/STS Multisociety Expert Consensus Statement: Operator & institutional requirements for transcatheter valve repair and replacement; Part 1 TAVR. J Am Coll Cardiol. 2012 Mar 1.

Visit www.AmericanNurseToday.com for a complete list of references.

Maria L. Held is a clinical nurse specialist at The Cleveland Clinic in Cleveland, Ohio.

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