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Left Ventricular Assist Device in Special Population of Patients
17 Left Ventricular Assist Device in Special Population of Patients Yakov L. Elgudin, Soon J. Park
KEY POINTS Case Presentation Introduction Modification in Surgical Technique
Potential Patient Population Summary
CASE PRESENTATION
thy, mostly ischemic or idiopathic, into vibrant individuals. Yet, those with RCM continue to suffer and face exceedingly high mortality. For instance, a young gentleman with familial hypertrophic cardiomyopathy (HCM) was rapidly deteriorating while awaiting heart transplantation. His LV cavity was nearly obliterated by a severely thickened LV, and he was struggling to maintain adequate forward flow by compensating his very small stroke volume with severe tachycardia. His impending demise compelled the application of a continuous-flow LVAD in this uncharted clinical arena. The surgical technique was modified to compensate for small LV cavity, and the LVAD pump speed had to be adjusted carefully under echocardiographic guidance. Application of successful support in this particular patient was very encouraging, and it opened up the possibility of LVAD support for those suffering from advanced HF due to various causes other than dilated cardiomyopathy. Topilsky et al.1 reported the first series on LVAD support and included eight study patients (four HCM and four RCM); outcomes were compared to 75 contemporaneous control patients with either idiopathic or ischemic dilated cardiomyopathy. As expected, baseline parameters associated with LV geometry significantly differed: LVEDD, 52.5 ± 6 mm vs. 68.6 ± 8 mm (P < 0.0001); septal wall thickness, 16 (12, 19) mm vs. 10 (8.5, 11) mm (P = 0.0003); and LV ejection fraction, 21% (20%, 36%) vs. 17% (15%, 22%) (P = 0.0087). Study patients had higher central venous pressure (CVP) (18 [15, 20] mm Hg vs. 12 [9, 15] mm Hg, P = 0.03) and lower pump flow (4.3 [3.8, 4.5] L vs. 5.2 [4.7, 5.5] L, P = 0.001) postoperatively. The operative mortality was comparable (12.5% vs 9.3%, P = 0.8). The actuarial 1-year survival rate was also comparable (87.5% [95% confidence interval, 52.9%–97.8%] vs. 73.2% [95% confidence interval, 60%–85%]), and this compared very favorably to 12.1% (95% confidence interval, 0%–55.2%, P = 0.1) for those historically managed medically. This early experience demonstrated the feasibility of supporting patients with nondilated RCM or HCM in a clinically meaningful manner. Swiecicki et al.2 reported their experience using LVAD to support nine patients with cardiac amyloidosis. All patients had NYHA functional class IV symptoms, and the majority required inotropic and/or intraaortic balloon pump support prior to their LVAD implantation. LVAD implantation resulted in adequate forward blood flow for all patients. Seven out of nine patients were discharged from the hospital. Three patients succumbed to death at 59, 251, and 1111 days following surgery. Four patients were alive with a follow up of 16–24 months.
A 73-year-old retired psychiatrist presents with advanced congestive heart failure (HF) (New York Heart Association [NYHA] class IV). He was healthy until about 3 years ago. On evaluation, he is found to have restrictive cardiomyopathy (RCM) due to senile cardiac amyloidosis. He also develops acute worsening of his chronic renal dysfunction. He is in atrial fibrillation, and his right heart catheterization reveals severe biventricular failure (right atrium [RA], 22 mm Hg; pulmonary artery [PA], 51/28 mm Hg; pulmonary capillary wedge pressure [PCWP], 33 mm Hg; cardiac output [CO], 1.82 L/min). His echocardiogram reveals a very small left ventricular (LV) cavity (LV end-diastolic dimension [LVEDD], 26 mm; LV end-systolic diameter [LVESD], 19 mm), with normal LV ejection fraction (52%). He successfully undergoes HeartMate II left ventricular assist device (LVAD) implantation with improvement in forward blood flow and end-organ function (Fig. 17.1).
INTRODUCTION The field of mechanical cardiac support has made significant advances since early 2000s, and the pumping mechanism of the native heart can now be effectively replaced with an LVAD. Substantial evidence exists that mechanical circulatory pumps can improve quality of life and longevity for those with end-stage dilated cardiomyopathy. However, similar mechanical options have not been widely used for patients with RCM. The existing pioneering experience for use of mechanical circulatory support in RCM will be reviewed and the potential benefits of employing LVAD in patients with failing Fontan circulation are explored. Most patients with advanced HF have a significantly dilated left ventricle (LV) from the process of chronic remodeling. They face a very poor quality of life and exceedingly high mortality. The initial National Institutes of Health project goal of replacing the failing human heart with a total artificial heart (TAH) has proven much more challenging, and utilization of TAH in the clinical setting is rather limited to date. However, the field of LVAD has evolved rapidly over the past few decades. The initial construct of LVAD as a volume displacement pump mimicking the mechanism of the natural heart has now been nearly completely replaced by durable pumps. It is remarkable how these pumps transform the lives of those facing imminent death from advanced dilated cardiomyopa-
203
204
CHAPTER 17 Left Ventricular Assist Device in Special Population of Patients
LAB AG Creatinine,S
2790-ROCUS
Bilirubin, Total
2373-ROCUS
9.5 9 8.5 8 7.5 7 6.5 6
Results
5.5 5 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 7/16/2011 7/23/2011 7/30/2011 8/6/2011 8/13/2011 8/19/2011 8/26/2011 7/9/2011 8/9/2011 8/30/2011 7/5/2011 7/12/2011 7/19/2011 7/26/2011 8/2/2011 8/16/2011 8/23/2011
Date Time
Fig. 17.1 Laboratory indicators of end-organ function before and after left ventricular assist device implantation in the case example.
Grupper et al.3 reported their expanded LVAD experience involving 28 patients with RCM. The underlying etiologies for RCM included amyloidosis (10 patients), HCM (eight patients), sarcoidosis (five patients), chemotherapy/radiation (four patients), and Fabry disease (one patient). Their baseline echocardiography demonstrated a small LV cavity (LVESD, 46.8 ± 12.3 mm; LVEDD, 53.7 ± 11.3 mm), and right ventricular (RV) dysfunction was present in 82% of patients. Their Interagency Registry for Mechanically Assisted Circulatory Support profiles were one in seven patients, 2 in 19 patients, and three in two patients. LVAD was implanted as destination therapy (DT) in 11 and as bridge to transplantation (BTT) in 17 patients. Despite the technical challenges associated with a small LV cavity size and thickened LV wall, LVAD implantation was successful in all patients. RV failure requiring prolonged inotropic support occurred in 11 patients (39%), and the mean duration of support was 17 days. Inhospital mortality was 14%. Ten patients successfully proceeded to heart transplant, with no mortality, and their mean LVAD support duration was 472 (273–671) days. Of the remaining 18 patients who received LVAD as DT, the 1-year survival rate was 64%, and mean survival time was 651 (358–945) days. Neither the underlying etiology of RCM nor the LVAD indication (BTT/DT) influenced the survival outcome. However, those with a very small LV cavity (LVEDD <46 mm) had worse outcomes. The three studies summarized here represent the evolution in expanding the application of LVAD therapy to a group of patients with RCM at Mayo Clinic. There seems to be objective evidence for survival benefit with LVAD implantation as compared to medical management for this group of patients.
MODIFICATION IN SURGICAL TECHNIQUE During LVAD implantation, an inflow cannula inserted into the apex of the LV redirects blood to a pump and an outflow graft attached to the aorta delivers blood from the pump back into circulation. In some
instances, the LV wall can be thick and the LV cavity small, making placement of an inflow cannula challenging. An approach used in our program to address LV geometry challenges in patients with HCM is first to arrest the heart with cardioplegia, which allows more precise execution of the surgery. After the intended location of inflow cannula placement is identified in the LV apex (Fig. 17.2A), a stab incision is made with an eleven blade from the epicardial surface into the LV cavity (see Fig. 17.2B). The tip of a Foley catheter treaded over the coring knife is inserted into the LV cavity (see Fig. 17.2C), and placement of the catheter in the LV cavity on transesophageal echocardiogram (TEE) is confirmed. The balloon of the catheter is inflated with 10 mL of saline solution. The catheter is gently pulled up, providing counter traction, and centered on the knife while the LV apex is cored (see Fig. 17.2D). Caution is exercised to avoid rupturing the balloon whose fragments can be lost in the LV cavity. Inspection of the LV cavity is important to ensure placement. In patients with HCM, excision of excess muscle circumferentially to create a space large enough to accommodate the inflow cannula may be necessary, whereas in patients with cardiac amyloidosis and friable myocardium that can tear easily, needles and sutures are handled carefully while affixing the inflow sewing ring (see Fig. 17.2E). Once the inflow cannula and ring are placed, the remaining implantation steps are completed. The inflow cannula is placed in the proper position running parallel to the septum and pointing toward the mitral valve, and this should be confirmed on TEE (Fig. 17.3).
Left Ventricular Assist Device Pump Speed Management Nearly all patients with advanced HF due to dilated cardiomyopathy have biventricular failure. While the failing LV is the prevailing problem, the RV is adversely affected by increased afterload secondary to pulmonary hypertension. LVAD is effective in reducing LV congestion and substantially reduces secondary pulmonary hypertension. As a result, RV function improves with afterload load reduction in
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Fig. 17.2 (A) Location of inflow cannula placement. (B) Stab incision with an eleven blade. (C) Tip of a Foley catheter treaded over the coring knife. (D) Cored left ventricular apex. (E) Sutured inflow sewing ring.
the pulmonary vasculature. The incidence of RV failure requiring prolonged inotropic support following LVAD implantation is approximately 10%. In patients with RCM, RV failure/dysfunction may be worse than in those with dilated cardiomyopathy since the infiltrative process can also directly affect the RV. Nearly 40% of these patients require prolonged inotropic support during the hospital stay following LVAD implantation. LVAD pump speed is adjusted to reduce LV end-diastolic pressure (LVEDP) in an attempt to minimize secondary pulmonary hypertension for the failing RV. Echocardiography is important in determining the appropriate LVAD pump speed. The position of the interatrial septum should be concave into the left atrium, and the mitral deceleration time should be prolonged to
reflect low LVEDP. The LV cavity may look small, but there should be unobstructed and continuous laminar flow into the inflow cannula. Echocardiographic images of a small LV cavity are a striking contrast to that of dilated cardiomyopathy. LVAD suction events due to inflow cannula obstruction have not been observed despite small LV cavity sizes. If the LVAD pump speed is reduced due to concerns about obstruction, patients are likely in biventricular failure with a low forward flow state (Fig. 17.4). These patients may need to be supported like those with a single ventricle in Fontan circulation. Patients with failing Fontan circulation develop elevated end-diastolic pressure of the systemic ventricle. This results in elevated systemic venous pressure through pulmonary congestion. These patients then suffer from protein losing enteropathy (PLE)
206
CHAPTER 17 Left Ventricular Assist Device in Special Population of Patients
Fig. 17.3 Echocardiographic confirmation of proper left ventricular assist device inflow cannula placement. The inflow cannula runs parallel to the septum and points toward the mitral valve.
and a low cardiac output state. Low filling pressure of the systemic ventricle is critically important for well-functioning Fontan circulation. Similarly, LV filling pressure needs to be kept low in those with severe RV dysfunction. The underlying etiology for RCM may continue to progress, and LVAD may become less effective in providing forward flow. For those with no further therapeutic options, LVAD may provide some meaningful extra time with patients’ loved ones. For others, heart transplant, chemotherapy, and/or autologous stem cell transplant may provide more durable benefit.
POTENTIAL PATIENT POPULATION LVAD technology continues to evolve. It is anticipated that newer LVAD devices will become smaller in size, decrease the incidence of hemolysis, and be more durable. As a result, patient populations who can benefit from LVAD support will likely expand. It seems to make physiologic sense to apply LVAD in those with failing Fontan circulation. Frazier et al.4 have reported one patient who was successfully supported by a ventricular assist device (VAD) for his failing single ventricle, albeit by a volume displacement VAD. Morales et al.5 were the first to report success implanting a HM II LVAD in a 15-year-old patient with failing Fontan circulation and PLE. Lorts et al.6 recently reported the first successful implantation of a third- generation LVAD, HeartMate 3 (HM3), in a 22-year-old patient with failing Fontan circulation who developed profound cardiogenic shock and required a veno-arterial extracorporeal membrane oxygenation support prior to implantation of the HM3 LVAD. This patient was eventually discharged from the hospital and followed for 3 months without incidence of stroke or bleeding. Improvements in LVAD technology, particularly pump size and hemocompatibility, will open new horizons in using VAD technology for the single-ventricle patient who has exhausted staged palliation options. Additionally, to date, LVAD has only been implanted to support a failing systemic ventricle. However, further miniaturization of pumps should allow for VAD implantation into a Fontan circuit itself to improve pulmonary blood flow.
Durham et al.7 applied computer modeling to support systemic VAD support in those with failing Fontan physiology. Their model showed that LVAD support could reduce systemic venous congestion by 35% and increase forward flow by 41% in this population. A clinical trial (The Destination Therapy Evaluation for Failing Fontan Study) VAD was proposed by an investigator but was subsequently withdrawn due to lack of enrollment (ClinicalTrials.gov Identifier NCT01149603). In the United States, the prevalence of HF with preserved ejection fraction (HFpEF), relative to HF with reduced ejection fraction (HFrEF), is increasing at an alarming rate of 1%, and an overwhelming majority of these patients are over age 65 years, such that the number of HFpEF patients currently outnumbers those with HFrEF. This group found that quality of life and life expectancy in patients with HFpEF were worse than in those with HFrEF. Mortality in their sample was 30%–60% at 5 years, with high rates of recurrent hospitalizations for acute decompensated HF.7 Diagnosis of HFpEF remains disputed, and understanding of its pathophysiology is still developing. It is currently understood as a disease of the microvasculature, with endothelial dysfunction and rarefication, yet epicardial coronary artery stenosis is present in over 50% of patients, which contributes to their worsening prognosis.8 In early 2018, Nguyen et al.9 reported that HFpEF is an independent risk factor for increased mortality, postoperative shock, and other adverse outcomes in patients after cardiac surgery. Unfortunately, no pharmacologic therapy, including neurohormonal antagonists, has demonstrated benefit in HFpEF, unlike in those with HFrEF. In the future, those with advanced HFpEF may constitute a large group of patients who could benefit from the use of implantable LVAD. The feasibility and efficacy of LVAD support in those with nondilated LVs have already been evaluated and proven in those with RCM.
SUMMARY LVADs have changed the landscape of HF management for the better. Patients with end-stage dilated cardiomyopathy have an excellent chance of living meaningful lives free of debilitating HF symptoms and recurrent hospitalizations. Durable LVADs have also been successfully employed
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Fig. 17.4 Left ventricular assist device (LVAD) inflow velocity. A patient’s LVAD pump speed was maintained at a lower setting with his small left ventricle cavity. He presented with fatigue and moderate to severe tricuspid regurgitation (TR). His flow velocity in the inflow cannula has a peak with high flow velocity during systole. At higher LVAD pump speed setting, the flow velocity has a blunted shape lower velocity during systole. His TR improved to moderate range.
in patients with RCM and relatively small LVs. However, there are still many patients with nondilated cardiomyopathy, including a vast population of patients with HFpEF, who do not currently have LVAD treatment options. These patients, in addition to a growing number of patients with failing Fontan, have the most need of critical improvements in LVAD pump size and hemocompatibility for expanded treatment options.
REFERENCES 1. Topilsky Y, Pereira NL, Shah DK, Boilson B, Schirger JA, Kushwaha SS, Joyce LD, Park SJ. Left ventricular assist device therapy in patients with restrictive and hypertrophic cardiomyopathy. Circ Heart Fail. 2011;4(3):266–275. https://doi.org/10.1161/ CIRCHEARTFAILURE.110.959288. Epub 2011 Feb 8. PMID: 21303989. Select item 16855265. 2. Swiecicki PL, Edwards BS, Kushwaha SS, Dispenzieri A, Park SJ, Gertz MA. Left ventricular device implantation for advanced cardiac amyloidosis. J Heart Lung Transplant. 2013;32(5):563–568. https://doi. org/10.1016/j.healun.2013.01.987. Epub 2013 Mar 6. PMID: 23474361. Select item 21303989. 3. Grupper A, Park SJ, Pereira NL, Schettle SD, Gerber Y, Topilsky Y, Edwards BS, Daly RC, Stulak JM, Joyce LD, Kushwaha SS. Role of ventricular assist therapy for patients with heart failure and restrictive physiology: improving outcomes for a lethal disease. J Heart Lung Transplant. 2015
Aug;34(8):1042–1049. https://doi.org/10.1016/j.healun.2015.03.012. Epub 2015 Mar 26. PMID:25940074. Select item 23474361. 4. Frazier OH, Gregoric ID, Messner GN. Total circulatory support with an LVAD in an adolescent with a previous Fontan procedure. Tex Heart Inst J. 2005;32(3):402–404. PMID: 16392230. Select item 23804979. 5. Morales DLS, Adachi I, Heinle JS, Fraser CD. A new era: use of an intracorporeal systemic ventricular assist device to support a patient with a failing Fontan circulation. J Thorac Cardiovasc Surg. 2011 Sep 1;142(3). e138–40. 6. Lorts A, Villa C, Riggs KW, Broderick J, Morales DL. First use of HeartMate 3 in a failing Fontan circulation. The Annals of Thoracic Surgery. 2018; https://doi.org/10.1016/ J Thoracsur.2018.04.021. 7. Durham LA III, LA, Dearani JA, Burkhart HM, Joyce LD, Cetta Jr F, Cabalka AK, Phillips SD, Sundareswaran K, Farrar D, Park SJ. Application of computer modeling in systemic VAD support of failing Fontan physiology. World J Pediatr Congenit Heart Surg. 2011 Apr;2(2):243–248. https://doi.org/10.1177/2150135110397386. PMID: 23804979. 8. Roh Jason, Houstis Nicolas, Rosenzweig Anthony. Why don’t we have proven treatment for HFpEF. Circ Res. 2017;120:1243–1245. 9. Lee S, Nguyen MD, Pierre Baudinaud MD, Alain Brusset MD, Florence Nicot MD, et al. Heart failure with preserved ejection fraction as an independent risk factor of mortality after cardiothoracic surgery. J Thorac Cardiovasc Surg. 2018;2:1–6.
KEY POINTS Case Presentation Introduction Modification in Surgical Technique
Potential Patient Population Summary
CASE PRESENTATION
thy, mostly ischemic or idiopathic, into vibrant individuals. Yet, those with RCM continue to suffer and face exceedingly high mortality. For instance, a young gentleman with familial hypertrophic cardiomyopathy (HCM) was rapidly deteriorating while awaiting heart transplantation. His LV cavity was nearly obliterated by a severely thickened LV, and he was struggling to maintain adequate forward flow by compensating his very small stroke volume with severe tachycardia. His impending demise compelled the application of a continuous-flow LVAD in this uncharted clinical arena. The surgical technique was modified to compensate for small LV cavity, and the LVAD pump speed had to be adjusted carefully under echocardiographic guidance. Application of successful support in this particular patient was very encouraging, and it opened up the possibility of LVAD support for those suffering from advanced HF due to various causes other than dilated cardiomyopathy. Topilsky et al.1 reported the first series on LVAD support and included eight study patients (four HCM and four RCM); outcomes were compared to 75 contemporaneous control patients with either idiopathic or ischemic dilated cardiomyopathy. As expected, baseline parameters associated with LV geometry significantly differed: LVEDD, 52.5 ± 6 mm vs. 68.6 ± 8 mm (P < 0.0001); septal wall thickness, 16 (12, 19) mm vs. 10 (8.5, 11) mm (P = 0.0003); and LV ejection fraction, 21% (20%, 36%) vs. 17% (15%, 22%) (P = 0.0087). Study patients had higher central venous pressure (CVP) (18 [15, 20] mm Hg vs. 12 [9, 15] mm Hg, P = 0.03) and lower pump flow (4.3 [3.8, 4.5] L vs. 5.2 [4.7, 5.5] L, P = 0.001) postoperatively. The operative mortality was comparable (12.5% vs 9.3%, P = 0.8). The actuarial 1-year survival rate was also comparable (87.5% [95% confidence interval, 52.9%–97.8%] vs. 73.2% [95% confidence interval, 60%–85%]), and this compared very favorably to 12.1% (95% confidence interval, 0%–55.2%, P = 0.1) for those historically managed medically. This early experience demonstrated the feasibility of supporting patients with nondilated RCM or HCM in a clinically meaningful manner. Swiecicki et al.2 reported their experience using LVAD to support nine patients with cardiac amyloidosis. All patients had NYHA functional class IV symptoms, and the majority required inotropic and/or intraaortic balloon pump support prior to their LVAD implantation. LVAD implantation resulted in adequate forward blood flow for all patients. Seven out of nine patients were discharged from the hospital. Three patients succumbed to death at 59, 251, and 1111 days following surgery. Four patients were alive with a follow up of 16–24 months.
A 73-year-old retired psychiatrist presents with advanced congestive heart failure (HF) (New York Heart Association [NYHA] class IV). He was healthy until about 3 years ago. On evaluation, he is found to have restrictive cardiomyopathy (RCM) due to senile cardiac amyloidosis. He also develops acute worsening of his chronic renal dysfunction. He is in atrial fibrillation, and his right heart catheterization reveals severe biventricular failure (right atrium [RA], 22 mm Hg; pulmonary artery [PA], 51/28 mm Hg; pulmonary capillary wedge pressure [PCWP], 33 mm Hg; cardiac output [CO], 1.82 L/min). His echocardiogram reveals a very small left ventricular (LV) cavity (LV end-diastolic dimension [LVEDD], 26 mm; LV end-systolic diameter [LVESD], 19 mm), with normal LV ejection fraction (52%). He successfully undergoes HeartMate II left ventricular assist device (LVAD) implantation with improvement in forward blood flow and end-organ function (Fig. 17.1).
INTRODUCTION The field of mechanical cardiac support has made significant advances since early 2000s, and the pumping mechanism of the native heart can now be effectively replaced with an LVAD. Substantial evidence exists that mechanical circulatory pumps can improve quality of life and longevity for those with end-stage dilated cardiomyopathy. However, similar mechanical options have not been widely used for patients with RCM. The existing pioneering experience for use of mechanical circulatory support in RCM will be reviewed and the potential benefits of employing LVAD in patients with failing Fontan circulation are explored. Most patients with advanced HF have a significantly dilated left ventricle (LV) from the process of chronic remodeling. They face a very poor quality of life and exceedingly high mortality. The initial National Institutes of Health project goal of replacing the failing human heart with a total artificial heart (TAH) has proven much more challenging, and utilization of TAH in the clinical setting is rather limited to date. However, the field of LVAD has evolved rapidly over the past few decades. The initial construct of LVAD as a volume displacement pump mimicking the mechanism of the natural heart has now been nearly completely replaced by durable pumps. It is remarkable how these pumps transform the lives of those facing imminent death from advanced dilated cardiomyopa-
203
204
CHAPTER 17 Left Ventricular Assist Device in Special Population of Patients
LAB AG Creatinine,S
2790-ROCUS
Bilirubin, Total
2373-ROCUS
9.5 9 8.5 8 7.5 7 6.5 6
Results
5.5 5 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 7/16/2011 7/23/2011 7/30/2011 8/6/2011 8/13/2011 8/19/2011 8/26/2011 7/9/2011 8/9/2011 8/30/2011 7/5/2011 7/12/2011 7/19/2011 7/26/2011 8/2/2011 8/16/2011 8/23/2011
Date Time
Fig. 17.1 Laboratory indicators of end-organ function before and after left ventricular assist device implantation in the case example.
Grupper et al.3 reported their expanded LVAD experience involving 28 patients with RCM. The underlying etiologies for RCM included amyloidosis (10 patients), HCM (eight patients), sarcoidosis (five patients), chemotherapy/radiation (four patients), and Fabry disease (one patient). Their baseline echocardiography demonstrated a small LV cavity (LVESD, 46.8 ± 12.3 mm; LVEDD, 53.7 ± 11.3 mm), and right ventricular (RV) dysfunction was present in 82% of patients. Their Interagency Registry for Mechanically Assisted Circulatory Support profiles were one in seven patients, 2 in 19 patients, and three in two patients. LVAD was implanted as destination therapy (DT) in 11 and as bridge to transplantation (BTT) in 17 patients. Despite the technical challenges associated with a small LV cavity size and thickened LV wall, LVAD implantation was successful in all patients. RV failure requiring prolonged inotropic support occurred in 11 patients (39%), and the mean duration of support was 17 days. Inhospital mortality was 14%. Ten patients successfully proceeded to heart transplant, with no mortality, and their mean LVAD support duration was 472 (273–671) days. Of the remaining 18 patients who received LVAD as DT, the 1-year survival rate was 64%, and mean survival time was 651 (358–945) days. Neither the underlying etiology of RCM nor the LVAD indication (BTT/DT) influenced the survival outcome. However, those with a very small LV cavity (LVEDD <46 mm) had worse outcomes. The three studies summarized here represent the evolution in expanding the application of LVAD therapy to a group of patients with RCM at Mayo Clinic. There seems to be objective evidence for survival benefit with LVAD implantation as compared to medical management for this group of patients.
MODIFICATION IN SURGICAL TECHNIQUE During LVAD implantation, an inflow cannula inserted into the apex of the LV redirects blood to a pump and an outflow graft attached to the aorta delivers blood from the pump back into circulation. In some
instances, the LV wall can be thick and the LV cavity small, making placement of an inflow cannula challenging. An approach used in our program to address LV geometry challenges in patients with HCM is first to arrest the heart with cardioplegia, which allows more precise execution of the surgery. After the intended location of inflow cannula placement is identified in the LV apex (Fig. 17.2A), a stab incision is made with an eleven blade from the epicardial surface into the LV cavity (see Fig. 17.2B). The tip of a Foley catheter treaded over the coring knife is inserted into the LV cavity (see Fig. 17.2C), and placement of the catheter in the LV cavity on transesophageal echocardiogram (TEE) is confirmed. The balloon of the catheter is inflated with 10 mL of saline solution. The catheter is gently pulled up, providing counter traction, and centered on the knife while the LV apex is cored (see Fig. 17.2D). Caution is exercised to avoid rupturing the balloon whose fragments can be lost in the LV cavity. Inspection of the LV cavity is important to ensure placement. In patients with HCM, excision of excess muscle circumferentially to create a space large enough to accommodate the inflow cannula may be necessary, whereas in patients with cardiac amyloidosis and friable myocardium that can tear easily, needles and sutures are handled carefully while affixing the inflow sewing ring (see Fig. 17.2E). Once the inflow cannula and ring are placed, the remaining implantation steps are completed. The inflow cannula is placed in the proper position running parallel to the septum and pointing toward the mitral valve, and this should be confirmed on TEE (Fig. 17.3).
Left Ventricular Assist Device Pump Speed Management Nearly all patients with advanced HF due to dilated cardiomyopathy have biventricular failure. While the failing LV is the prevailing problem, the RV is adversely affected by increased afterload secondary to pulmonary hypertension. LVAD is effective in reducing LV congestion and substantially reduces secondary pulmonary hypertension. As a result, RV function improves with afterload load reduction in
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Fig. 17.2 (A) Location of inflow cannula placement. (B) Stab incision with an eleven blade. (C) Tip of a Foley catheter treaded over the coring knife. (D) Cored left ventricular apex. (E) Sutured inflow sewing ring.
the pulmonary vasculature. The incidence of RV failure requiring prolonged inotropic support following LVAD implantation is approximately 10%. In patients with RCM, RV failure/dysfunction may be worse than in those with dilated cardiomyopathy since the infiltrative process can also directly affect the RV. Nearly 40% of these patients require prolonged inotropic support during the hospital stay following LVAD implantation. LVAD pump speed is adjusted to reduce LV end-diastolic pressure (LVEDP) in an attempt to minimize secondary pulmonary hypertension for the failing RV. Echocardiography is important in determining the appropriate LVAD pump speed. The position of the interatrial septum should be concave into the left atrium, and the mitral deceleration time should be prolonged to
reflect low LVEDP. The LV cavity may look small, but there should be unobstructed and continuous laminar flow into the inflow cannula. Echocardiographic images of a small LV cavity are a striking contrast to that of dilated cardiomyopathy. LVAD suction events due to inflow cannula obstruction have not been observed despite small LV cavity sizes. If the LVAD pump speed is reduced due to concerns about obstruction, patients are likely in biventricular failure with a low forward flow state (Fig. 17.4). These patients may need to be supported like those with a single ventricle in Fontan circulation. Patients with failing Fontan circulation develop elevated end-diastolic pressure of the systemic ventricle. This results in elevated systemic venous pressure through pulmonary congestion. These patients then suffer from protein losing enteropathy (PLE)
206
CHAPTER 17 Left Ventricular Assist Device in Special Population of Patients
Fig. 17.3 Echocardiographic confirmation of proper left ventricular assist device inflow cannula placement. The inflow cannula runs parallel to the septum and points toward the mitral valve.
and a low cardiac output state. Low filling pressure of the systemic ventricle is critically important for well-functioning Fontan circulation. Similarly, LV filling pressure needs to be kept low in those with severe RV dysfunction. The underlying etiology for RCM may continue to progress, and LVAD may become less effective in providing forward flow. For those with no further therapeutic options, LVAD may provide some meaningful extra time with patients’ loved ones. For others, heart transplant, chemotherapy, and/or autologous stem cell transplant may provide more durable benefit.
POTENTIAL PATIENT POPULATION LVAD technology continues to evolve. It is anticipated that newer LVAD devices will become smaller in size, decrease the incidence of hemolysis, and be more durable. As a result, patient populations who can benefit from LVAD support will likely expand. It seems to make physiologic sense to apply LVAD in those with failing Fontan circulation. Frazier et al.4 have reported one patient who was successfully supported by a ventricular assist device (VAD) for his failing single ventricle, albeit by a volume displacement VAD. Morales et al.5 were the first to report success implanting a HM II LVAD in a 15-year-old patient with failing Fontan circulation and PLE. Lorts et al.6 recently reported the first successful implantation of a third- generation LVAD, HeartMate 3 (HM3), in a 22-year-old patient with failing Fontan circulation who developed profound cardiogenic shock and required a veno-arterial extracorporeal membrane oxygenation support prior to implantation of the HM3 LVAD. This patient was eventually discharged from the hospital and followed for 3 months without incidence of stroke or bleeding. Improvements in LVAD technology, particularly pump size and hemocompatibility, will open new horizons in using VAD technology for the single-ventricle patient who has exhausted staged palliation options. Additionally, to date, LVAD has only been implanted to support a failing systemic ventricle. However, further miniaturization of pumps should allow for VAD implantation into a Fontan circuit itself to improve pulmonary blood flow.
Durham et al.7 applied computer modeling to support systemic VAD support in those with failing Fontan physiology. Their model showed that LVAD support could reduce systemic venous congestion by 35% and increase forward flow by 41% in this population. A clinical trial (The Destination Therapy Evaluation for Failing Fontan Study) VAD was proposed by an investigator but was subsequently withdrawn due to lack of enrollment (ClinicalTrials.gov Identifier NCT01149603). In the United States, the prevalence of HF with preserved ejection fraction (HFpEF), relative to HF with reduced ejection fraction (HFrEF), is increasing at an alarming rate of 1%, and an overwhelming majority of these patients are over age 65 years, such that the number of HFpEF patients currently outnumbers those with HFrEF. This group found that quality of life and life expectancy in patients with HFpEF were worse than in those with HFrEF. Mortality in their sample was 30%–60% at 5 years, with high rates of recurrent hospitalizations for acute decompensated HF.7 Diagnosis of HFpEF remains disputed, and understanding of its pathophysiology is still developing. It is currently understood as a disease of the microvasculature, with endothelial dysfunction and rarefication, yet epicardial coronary artery stenosis is present in over 50% of patients, which contributes to their worsening prognosis.8 In early 2018, Nguyen et al.9 reported that HFpEF is an independent risk factor for increased mortality, postoperative shock, and other adverse outcomes in patients after cardiac surgery. Unfortunately, no pharmacologic therapy, including neurohormonal antagonists, has demonstrated benefit in HFpEF, unlike in those with HFrEF. In the future, those with advanced HFpEF may constitute a large group of patients who could benefit from the use of implantable LVAD. The feasibility and efficacy of LVAD support in those with nondilated LVs have already been evaluated and proven in those with RCM.
SUMMARY LVADs have changed the landscape of HF management for the better. Patients with end-stage dilated cardiomyopathy have an excellent chance of living meaningful lives free of debilitating HF symptoms and recurrent hospitalizations. Durable LVADs have also been successfully employed
CHAPTER 17 Left Ventricular Assist Device in Special Population of Patients
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Fig. 17.4 Left ventricular assist device (LVAD) inflow velocity. A patient’s LVAD pump speed was maintained at a lower setting with his small left ventricle cavity. He presented with fatigue and moderate to severe tricuspid regurgitation (TR). His flow velocity in the inflow cannula has a peak with high flow velocity during systole. At higher LVAD pump speed setting, the flow velocity has a blunted shape lower velocity during systole. His TR improved to moderate range.
in patients with RCM and relatively small LVs. However, there are still many patients with nondilated cardiomyopathy, including a vast population of patients with HFpEF, who do not currently have LVAD treatment options. These patients, in addition to a growing number of patients with failing Fontan, have the most need of critical improvements in LVAD pump size and hemocompatibility for expanded treatment options.
REFERENCES 1. Topilsky Y, Pereira NL, Shah DK, Boilson B, Schirger JA, Kushwaha SS, Joyce LD, Park SJ. Left ventricular assist device therapy in patients with restrictive and hypertrophic cardiomyopathy. Circ Heart Fail. 2011;4(3):266–275. https://doi.org/10.1161/ CIRCHEARTFAILURE.110.959288. Epub 2011 Feb 8. PMID: 21303989. Select item 16855265. 2. Swiecicki PL, Edwards BS, Kushwaha SS, Dispenzieri A, Park SJ, Gertz MA. Left ventricular device implantation for advanced cardiac amyloidosis. J Heart Lung Transplant. 2013;32(5):563–568. https://doi. org/10.1016/j.healun.2013.01.987. Epub 2013 Mar 6. PMID: 23474361. Select item 21303989. 3. Grupper A, Park SJ, Pereira NL, Schettle SD, Gerber Y, Topilsky Y, Edwards BS, Daly RC, Stulak JM, Joyce LD, Kushwaha SS. Role of ventricular assist therapy for patients with heart failure and restrictive physiology: improving outcomes for a lethal disease. J Heart Lung Transplant. 2015
Aug;34(8):1042–1049. https://doi.org/10.1016/j.healun.2015.03.012. Epub 2015 Mar 26. PMID:25940074. Select item 23474361. 4. Frazier OH, Gregoric ID, Messner GN. Total circulatory support with an LVAD in an adolescent with a previous Fontan procedure. Tex Heart Inst J. 2005;32(3):402–404. PMID: 16392230. Select item 23804979. 5. Morales DLS, Adachi I, Heinle JS, Fraser CD. A new era: use of an intracorporeal systemic ventricular assist device to support a patient with a failing Fontan circulation. J Thorac Cardiovasc Surg. 2011 Sep 1;142(3). e138–40. 6. Lorts A, Villa C, Riggs KW, Broderick J, Morales DL. First use of HeartMate 3 in a failing Fontan circulation. The Annals of Thoracic Surgery. 2018; https://doi.org/10.1016/ J Thoracsur.2018.04.021. 7. Durham LA III, LA, Dearani JA, Burkhart HM, Joyce LD, Cetta Jr F, Cabalka AK, Phillips SD, Sundareswaran K, Farrar D, Park SJ. Application of computer modeling in systemic VAD support of failing Fontan physiology. World J Pediatr Congenit Heart Surg. 2011 Apr;2(2):243–248. https://doi.org/10.1177/2150135110397386. PMID: 23804979. 8. Roh Jason, Houstis Nicolas, Rosenzweig Anthony. Why don’t we have proven treatment for HFpEF. Circ Res. 2017;120:1243–1245. 9. Lee S, Nguyen MD, Pierre Baudinaud MD, Alain Brusset MD, Florence Nicot MD, et al. Heart failure with preserved ejection fraction as an independent risk factor of mortality after cardiothoracic surgery. J Thorac Cardiovasc Surg. 2018;2:1–6.