As the prevalence of heart failure

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1 ID:4465 R E V I E W P A P E R Managing the Post-Left Ventricular Assist Device Patient The implantation of ventricular assist devices allows the opportunity for patients with intractable heart failure to have improved quality and quantity of life. The devices may be implanted after failed attempts to wean from bypass, as a bridge to transplantation, or as destination therapy. Key issues following the implantation of assist devices include the prevention of right ventricular failure, appropriate pharmacologic management, prevention and management of infection, and detection and treatment of device dysfunction. (CHF. 2006;12:41 45) 2006 CHF, Inc. As the prevalence of heart failure continues to increase, the need for long-term methods of support for patients with end-stage illness is paramount. Once thought of as only experimental in major academic centers, it is now not uncommon for patients to be supported with ventricular assist devices (VADs) in the outpatient setting. The impact of device therapy will likely continue to increase and permeate significant amounts of community practice. The evolving understanding of the physiology of devices, combined with strategies to mitigate the more frequent complications of the devices, will help guide appropriate use of this technology. Devices are placed for several broad indications, including bridge to recovery following failed attempts to wean from cardiopulmonary bypass, bridge to transplantation in patients not able to be supported pharmacologically, and destination therapy. Following the findings of the Randomized Evaluation of Mechanical Assistance for the Treatment of Congestive Heart Failure (REMATCH) trial, 1 many centers across the United States sought approval as destination therapy centers. This event began a new era in mechanical circulatory support where, for the first time, there was a Food and Drug Administration-approved cardiac assist device intended for patients who were not candidates for transplantation. Patients selected for implantation under this indication will now have only two end points: death and device failure requiring reimplantation. With increasing utilization of this technology, we must carefully consider and confront many of the issues that have long plagued patients on left ventricular assist devices (LVADs) (Table I). The most common and pressing of these issues shall serve as the focus of this article, including prevention and management of right heart failure, pharmacologic management of the post- LVAD patient, management of devicerelated infection, and detection and management of device dysfunction. Right Heart Failure Right heart failure has been generally defined as the need for a right VAD, or prolonged inotropic therapy, to support the right heart function for longer than 14 days. Appropriate patient selection and preoperative preparation may be the key to achieving success with VADs. 2 4 The use of VADs for destination therapy should not be considered as a bail-out procedure but, rather, should be restricted to elective implantation following appropriate assessment of comorbidities and risk and a period of medical optimization. 5 7 This may involve ensuring adequate preoperative dental hygiene to prevent postoperative infection, pharmacologic optimization of right heart function, and additional diuresis. Anecdotal reports detail the preoperative use of intraaortic balloon pumps to allow the right heart a period of optimization before LVAD. It is thought that lowering the left ventricular end-diastolic pressure and augmenting the right coronary artery perfusion may allow right heart rehabilitation before increased workload following LVAD implantation. Right ventricular failure is a key cause of morbidity and mortality, including multi-organ failure, with the use of Charles T. Klodell, MD; 1 Edward D. Staples, MD; 1 Juan M. Aranda, Jr., MD; 2 Richard S. Schofield, MD; 2 James A. Hill, MD; 2 Daniel F. Pauly, MD, PhD; 2 Thomas M. Beaver, MD 1 From the Departments of Surgery 1 and Medicine, 2 University of Florida, Gainesville, FL Address for correspondence: Charles T. Klodell, MD, Thoracic and Cardiovascular Surgery, PO Box , Gainesville, FL klodell@surgery.ufl.edu Manuscript received July 11, 2005; accepted July 27, 2005 managing the post-lvad patient january. february

2 Table I. Issues Involved With the Care of the Post-LVAD Patient Prevent/treat right heart dysfunction Bleeding Infection Mechanical LVAD dysfunction Arrhythmias Hypertension Axial flow issues Anticoagulation Prepare community/emergency services Close follow-up with LVAD coordinator LVAD=left ventricular assist device Table II. Possible Causes of Altered LVAD Flow LOW LVAD FLOW Right ventricular dysfunction Bleeding Cardiac tamponade Inflow valve obstruction Volume shifts from venous pooling Overdiuresis HIGH LVAD FLOW Sepsis Intracardiac shunting Inflow valve regurgitation Outflow valve regurgitation Native aortic valve regurgitation LVAD=left ventricular assist device Table III. Factors Predictive of Right Heart Failure Following LVAD Right ventricular end-diastolic dimension >8.5 cm, volumes >200 cc Pulmonary artery pressure (PAP) >60 mm Hg Right atrial pressure (RAP) >20 mm Hg RAP >PCWP RVSWI* <5 LVAD=left ventricular assist device; PCWP=pulmonary capillary wedge pressure; *right ventricular stroke work index (RVSWI) stroke volume index (mean PAP RAP) VADs. 8 Most patients selected for destination therapy require support of the left ventricle alone, but many patients with left heart failure have coexisting right heart failure. Patients who require biventricular support have been reported to have significantly higher pre-vad creatinine and total bilirubin levels than LVAD patients, as well as a greater need for mechanical ventilation. 9 Successful management of LVAD implantation is essentially management of right heart function. Right heart failure can occur quickly and is difficult to manage once it becomes severe. The right heart preload can be modulated in several ways. Fluid therapy must be managed judiciously to avoid right heart volume overload. It is essential to avoid high LVAD flows in the early postoperative period, since mechanical factors that may lead to right ventricular failure can be influenced by the modes in which the LVAD is allowed to operate. As previously stated, many patients arrive in the operating room for placement of the LVAD with significant biventricular failure. Once the LVAD is activated, and the left-sided failure is mechanically resolved, the right heart function must tolerate the additional volume load from the pump. The right heart is responsible for generating the preload to fill the device adequately. It is for this reason that many centers have elected to operate the VADs at a fixed rate to generate a VAD output of 2.2 L/min/m 2. While in automatic, or full/empty mode, the VAD might have an output of nearly 10 L, which would significantly challenge the ailing right ventricle. It is through careful device management and reigning in of the flow that the right heart may be allowed a period of rehabilitation before the expectation of handling these massively increased flows compared with the preoperative left ventricular function. An additional issue, which has been observed with the evolving axial flow technology, is complete decompression of the left ventricle leading to right heart failure. In axial flow technology, the draining of the left ventricle is continuous, which may lead to a shifting of the interventricular septum and subsequent deformation of the right ventricle. It is thought that this deformation may be a mechanical disadvantage to the right ventricle and precipitate right heart failure. Early postoperative consideration of ultrafiltration may assist in fluid removal in cases where diuretic infusions prove ineffective in controlling the right heart preload. Right heart contractility may be enhanced with inotropic infusions. Milrinone and dobutamine infusions are frequently utilized when weaning from cardiopulmonary bypass and continued for several days. Immediate postoperative strategies to reduce pulmonary resistance include the use of vasodilators such as nitroglycerin, sodium nitroprusside, nesiritide, and sildenafil. 10 Pharmacologic modulation of pulmonary resistance is essential, especially with the administration of protamine and blood products known to increase pulmonary vascular resistance. Careful observance of trends in the hemodynamic profile is critical since decreased LVAD flow may mean hypovolemia with a downward trend in the right atrial pressure or impending right heart failure and poor LVAD filling with a rising right atrial pressure. Clinical conditions that may cause dramatic changes in LVAD flow are summarized in Table II. Right ventricular failure is often a key factor leading to renal dysfunction following VAD implantation. Right atrial pressures in excess of 20 mm Hg lead to changes in glomerular filtration from cortical to medullary nephrons, with secondary reduction in urinary output and resistance to diuretic therapy. Several factors have been recognized that have an 80% predictive value for accurately identifying patients that will suffer right heart failure following LVAD. These factors include the right ventricular size, significant pulmonary hypertension, elevated right atrial pressure, and low right ventricular stroke work index 8 (Table III). Pharmacologic Management of the Post-LVAD Patient Pharmacotherapy for the post-lvad patient follows the traditional heart failure philosophy. Beta blockade is utilized almost universally, with carvedilol as the most common agent. Angiotensin-converting enzyme inhibitors, or angiotensin receptor blockers, 42 managing the post-lvad patient january. february 2006

3 are also ubiquitous. Aspirin therapy is commonly utilized in all patients on HeartMate (Thoratec Corporation, Pleasanton, CA) LVADs. This combination of drugs is particularly important for the preservation of right heart function, but also helps mitigate the deleterious effect of systemic hypertension on long-term VAD wear. The Food and Drug Administrationapproved device for destination therapy is the HeartMate XVE LVAD which employs porcine valves for both inflow and outflow conduits. The inflow valve is particularly susceptible to structural deterioration if exposed to persistently high afterload, making this perhaps the most crucial factor in long-term device durability. As in patients with heart failure who do not have LVADs, the treatment of arrhythmias should be rapid and aggressive. Failure to rapidly treat and restore sinus rhythm may result in right heart distension and failure, which can be very difficult to treat. Traditional pharmacotherapy is utilized, including diltiazem, amiodarone, and lidocaine, as indicated. Although uncommon, cardioversion can be performed on patients on LVAD support. With the XVE device, it is recommended that the LVAD system controller be disconnected from the device briefly during the time of cardioversion. Infection Like all other patients with implanted foreign bodies, LVAD patients are susceptible to infection. Infection can be one of the most common morbidities encountered in patients supported with mechanical devices. 11 This may involve only superficial infection of the percutaneous driveline or deep infection of the pump and pump pocket. The most severe form of infection can involve the internal pump components, as an endocarditis of the pumping chamber or inflow/outflow valves. This endo- VADitis is particularly worrisome in that it can cause an embolic stroke. Suspected infection of the VAD pocket or internal components of the VAD are surgical urgencies and should Percentage of pumps 100% 80% 60% 40% 20% 0% Days from implantation Figure 1. Improved left ventricular assist device durability. HeartMate pumps (XVE left ventricular assist system and VE/SNAP) freedom from any major device failure, p< Source: Thoratec Device Tracking Registry and Complaint Database, March 31, 2005; Thoratec Corporation, Pleasanton, CA be formally evaluated by the implanting center if feasible. Pocket infections typically require surgical drainage and may necessitate pump exchange. Infection involving the internal pump components will similarly require exchange of the pump or pump component. Patients presenting with purulent drainage around the percutaneous driveline exit site must be differentiated into two groups. The group that has driveline exudate as a presenting sign of pocket infection should be dealt with as outlined above. The other group consists of patients who have infection only at the driveline exit site. This can usually be corrected with local wound care and systemic antibiotic therapy. Although no consensus has been developed, anecdotal reports of successful treatment of driveline infection with topical materials such as calcium alginate dressings, silver-impregnated dressings (Silverlon, Willowbrook, IL), and vacuum-assisted closure therapy have all reported success. Although infectious complications can be frustrating to encounter and treat, it is equally reassuring that neither pocket infection nor driveline infection has been shown to decrease survival in patients with LVADs. 11 Device Dysfunction LVAD failure and malfunction are inevitable consequences of establishing VE/SNAP (n=1556) XVE (n=1330) LVADs as a long-term therapy for endstage heart failure patients. Significant improvements in device durability continue to evolve as additional long-term experiences with LVADs are gained. Additions such as a strain relief on the outflow graft and the addition of optimal filling software have reduced malfunctions by more than 50%. 12 The Achilles heel of long-term support with the HeartMate XVE device remains inflow valve dysfunction (Figures 1 and 2). It is important to utilize clinical strategies to prolong pump life. This includes the use of the fixed rate mode of pump operation at the lowest tolerated rate when the patient is inactive. Excellent control of systemic hypertension is also of paramount importance in reducing the intracavitary pump pressure and secondary stress on the inflow valve. Unfortunately, even with the best strategies to prolong pump life, it will ultimately become necessary to diagnose and manage pump dysfunction, including inflow valve insufficiency and bearing failure. Subsequent catheterand echocardiography-based investigation of the device will better elucidate the etiology of the dysfunction. 13 Inflow Valve Insufficiency Signs of inflow valve insufficiency include increasing LVAD rate and managing the post-lvad patient january. february

4 Percentage of pumps months 18 months 24 months Figure 2. Improved inflow valve durability. HeartMate pumps (XVE and VE) free of inflow malfunctions, p< (logrank). Source: Thoratec Device Tracking Registry and Complaint Database, March 31, 2005; Thoratec Corporation, Pleasanton, CA LVAD patient with signs/symptoms of inflow valve dysfunction Echocardiography-/ catheter-based interrogation of LVAD confirms inflow valve dysfunction Thermodilution cardiac output 50%<LVAD flow No Thermodilution cardiac output within 20% LVAD flow No Management based on patient symptoms and close follow-up XVE VE Figure 3. Management algorithm of the left ventricular assist device (LVAD) patient Yes Yes Urgent transplantation or inflow valve replacement Medical management (reduce afterload) output, while the measured right ventricular output via thermodilution remains much less. The symptoms depend on the function of the native left ventricle and the degree of synchrony between the VAD and the ventricle. Initial investigations will include laboratory data, echocardiography, and cardiac catheterization. The differential diagnosis must include the development of native aortic valve insufficiency, as well as insufficiency of the VAD outflow valve. The management of inflow valve insufficiency depends on the patient s condition. Initial intervention includes operating the device in fixed mode, with maximally tolerated afterload reduction. Much like native mitral valve regurgitation, the patient must be monitored for signs of left atrial hypertension and systemic hypoperfusion. If the difference between the right heart thermodilution cardiac output and the LVAD output is large (approaching 50% or greater), then inflow valve replacement and/or pump exchange must be considered. In patients with less than a 50% difference between the two outputs, medical management can be considered based on patient condition (Figure 3). Bearing Wear The wearing of parts is the inevitable consequence of metal surface contact. Efforts in the development of future long-term VADs have been directed at significantly reducing the opportunity for bearing wear. The implanting center should periodically see the patient for follow-up and submit the filter cartridges for composition analysis. Analysis of the proportion of various metal particles in the filter allows for assessments of bearing wear and residual pump life. For the practitioner outside of the implanting center, the signs of impending pump failure will be relatively obvious. Particular attention should be paid to the sound of the pump. A change of the pitch or quality of the pump function may be the first sign of bearing wear. 44 managing the post-lvad patient january. february 2006

5 Conclusion As the impact of device therapy continues to increase and permeate the medical community, it is imperative that we disseminate the knowledge we have gained from the assist device clinical trials. It is through the spread of best practices and improved understanding of the issues surrounding long-term mechanical support that advances in the field can be secured. Significant clinical progress is being made in the prevention and management of right heart failure, pharmacologic management of the post-lvad patient, management of device-related infection, and detection and management of device dysfunction. These are some of the most pressing issues that confront our patients daily lives when supported with a device. The understanding and management of such issues will lead to improved quality and quantity of life for our patients. REFERENCES 1 Rose EA, Gelijns AC, Moskowitz AJ, et al. Long-term mechanical left ventricular assistance for end-stage heart failure. N Engl J Med. 2001;345: Stevenson LW, Rose EA. Left ventricular assist devices: bridges to transplantation, recovery, and destination for whom? Circulation. 2003;108: Miller LW. Patient selection for the use of ventricular assist devices as a bridge to transplantation. Ann Thorac Surg. 2003;75(6 suppl):66s 71S. 4 Aaronson KD, Patel H, Pagani FD. Patient selection for left ventricular assist device therapy. Ann Thorac Surg. 2003;75(6 suppl):29s 35S. 5 Mehta SM, Boehmer JP, Pae WE Jr, et al. Bridging to transplant. Equal extended survival for patients undergoing LVAD support when compared with long-term medical management. ASAIO J. 1996;42:M406 M Mielniczuk L, Mussivand T, Davies R, et al. Patient selection for left ventricular assist devices. Artif Organs. 2004;28: Williams M, Casher J, Joshi N, et al. Insertion of a left ventricular assist device in patients without thorough transplant evaluations: a worthwhile risk? J Thorac Cardiovasc Surg. 2003;126: Ochiai Y, McCarthy PM, Smedira NG, et al. Predictors of severe right ventricular failure after implantable left ventricular assist device insertion: analysis of 245 patients. Circulation. 2002;106(12 suppl 1):I198 I Farrar DJ, Hill JD, Pennington DG, et al. Preoperative and postoperative comparison of patients with univentricular and biventricular support with the thoratec ventricular assist device as a bridge to cardiac transplanatation. J Thorac Cardiovasc Surg. 1997;113: Trachte AL, Lobato EB, Urdaneta F, et al. Oral sildenafil reduces pulmonary hypertension after cardiac surgery. Ann Thorac Surg. 2005;79: [discussion ]. 11 Holman WL, Park SJ, Long JW, et al. Infection in permanent circulatory support: experience from the REMATCH trial. J Heart Lung Transplant. 2004;23: Dembitsky WP, Tector AJ, Park S, et al. Left ventricular assist device performance with long-term circulatory support: lessons from the REMATCH trial. Ann Thorac Surg. 2004;78: [discussion ]. 13 Horton SC, Khodaverdian R, Powers A, et al. Left ventricular assist device malfunction: a systematic approach to diagnosis. J Am Coll Cardiol. 2004;43: managing the post-lvad patient january. february

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