Case presentation
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 cardiomyopathy, 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. 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. 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.
Grupper et al. 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. In-hospital 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. 17.2 A ), a stab incision is made with an eleven blade from the epicardial surface into the LV cavity (see Fig. 17.2 B). The tip of a Foley catheter treaded over the coring knife is inserted into the LV cavity (see Fig. 17.2 C), 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. 17.2 D). 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. 17.2 E). 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 ).
