The usefulness of the total artificial heart (TAH-t, SynCardia, Tucson, AZ) in patients with advanced heart failure is limited to a select group of patients with severe biventricular heart failure. The technology for the TAH-t was developed in the 1960s, and in 1969, the TAH-t was first implanted in a human by Denton A. Cooley at the Texas Heart Institute (Houston, TX). The TAH-t consists of two artificial polyurethane ventricles and four flexible polyurethane diaphragms that separate a blood and air chamber. The diaphragms allow the artificial ventricle to fill and then eject blood when compressed by air from the external console. Two 27 and 25 mm Medtronic-Hall tilting disc valves are mounted in the inflow and outflow ports of each ventricle, respectively.1 Each artificial ventricle fills with compressed air via a 7-foot pneumatic driveline that connects to the external console. During implantation, ventricular tissue is resected away, and the artificial ventricles are sewn directly onto the atria and great vessels. After placement, the presence of mechanical valves ensures unidirectional flow; however, this limits pulmonary artery (PA) catheterization and measurement of pulmonary hemodynamics.
Outcomes after heart transplantation are worse for patients who have elevated pulmonary pressures and pulmonary vascular resistance (PVR) before transplantation.2 However, it remains unknown whether TAH-t implantation in patients with biventricular failure (and elevated PVR) would normalize PA pressures to allow for safe heart transplantation. Currently, we are unable to directly measure these pressures by using invasive techniques. The CardioMEMS Heart Failure (HF) System (St. Jude Medical, Little Canada, MN), approved by the Food and Drug Administration (FDA), utilizes a small pressure sensor implanted percutaneously in the PA that can be interrogated remotely3 and provides real-time pulmonary pressure readings without the need for right heart catheterization. Previously, there are few reports of use of CardioMEMS device in patients with left ventricular assist devices.4 Here, we describe the use of the CardioMEMS device in a patient with a TAH-t to monitor PA pressures, which supported successful listing of the patient for heart transplantation. Of note, our patient has been discussed in detail in a separate context in the current journal.5
A 20 year old Caucasian man with a history of asthma was admitted with acute decompensated heart failure and dilated cardiomyopathy. An echocardiogram showed a severely reduced left ventricular ejection fraction, biventricular restrictive filling, and an apical thrombus in the left ventricle. Invasive hemodynamics demonstrated a mean right atrial pressure of 15 mm Hg, right ventricular systolic pressure of 66 mm Hg, PA pressure (systolic/diastolic/mean) of 68/36/50 mm Hg, pulmonary capillary wedge pressure of 33 mm Hg with a cardiac index of 1.18 L/min/m2, and PVR of 7.4 Woods units. On angiography, the patient’s coronary arteries were nonobstructed. Cardiac magnetic resonance imaging demonstrated a laminated apical thrombus with subendocardial hyperenhancement of the left ventricular apex, lateral and septal walls, consistent with fibrosis. An endomyocardial biopsy confirmed severe eosinophilic infiltration, necrosis, and endomyocardial fibrosis. After a normal lung biopsy and initiation of intravenous inotropic support, the patient was evaluated for heart transplantation. Because of severe left and right ventricular endomyocardial fibrosis, support with a left ventricular assist device or a biventricular assist device (Bi-VAD) was not feasible. In addition, pulmonary vasodilators and phosphodiestrase-5 inhibitors failed to improve pulmonary hemodynamics, and the patient’s severely elevated PVR precluded transplant listing (IA) listing for heart transplantation. Given the limited options, the decision was made to proceed with TAH-t implantation (SynCardia) as a bridge to decision, pending improvement in pulmonary hemodynamics. A CardioMEMS sensor was successfully implanted in the left lower PA preoperatively (Figure 1). A week later, TAH-t implantation was carried out. Postoperative course was complicated with pre-renal azotemia because of fall in natriuretic hormone levels, necessitating the short-term intravenous infusion of nesiritide.6 PA pressures were monitored daily, and hemodynamics demonstrated gradual improvement (Table 1). On postoperative day 3, the pulmonary pressures near normalized, a trend that persisted throughout the remainder of the hospitalization (Figure 2). Four weeks after TAH-t implantation and 8 weeks since admission, the patient was discharged home and successfully listed for heart transplantation during outpatient follow-up.
For patients who have biventricular heart failure with restrictive physiology, the therapeutic options are limited, and treatment can be challenging. Because of the small ventricular cavity size, the implantation of a durable continuous-flow ventricular assist device is not possible. Ideally, urgent listing for heart transplantation is warranted. However, in patients who have elevated PVR, cardiac transplantation may not be feasible because of the risk of right ventricular failure after transplantation and poor survival observed in heart transplant recipients with irreversible pulmonary hypertension.7
In a prospective clinical study by Copeland et al.,8 the TAH-t was compared with optimal medical therapy with intra-aortic balloon pump therapy in patients with biventricular failure. Patients who were supported with a TAH-t had a significantly higher survival-to-transplantation rate than the control group (79% vs. 46%, p < 0.001), leading to the FDA approval for the TAH-t.8 Although current TAH technology does not allow for the direct measurement of PA pressures, indirect methods using right-sided filling pressure modulation have been suggested, though with limited hemodynamic correlation.9 Invasive heart catheterization remains technically unfeasible in these patients. The CardioMEMS HF sensor is currently the only FDA-approved system for PA pressure–guided HF therapy. This system has been successfully used to monitor pulmonary artery pressure and volume status in advanced HF patients, reduce re-hospitalization, and improve quality of life.3 The CardioMEMS Heart Sensor Allows Monitoring of Pressures to Improve Outcomes in New York Heart Association Functional Class III Heart Failure Patients (CHAMPION) trial demonstrated a 37% reduction in HF hospitalizations and improvement in quality of life in New York Heart Association Class III HF with reduced ejection fraction patients with the CardioMEMS System compared with standard therapy at 6 months.3 , 10 Follow up analysis also demonstrated a 58% reduction in all-cause 30-day readmissions.11,12,13 To our knowledge, the concomitant use of CardioMEMS and TAH-t has not been previously reported. With the CardioMEMS device, we were able to detect the significant improvement in PA pressures, which supported successful listing for heart transplantation. We believe the primary driver of severe pulmonary hypertension in our case was left heart failure. With improvement in left ventricular filling pressures, intrapulmonary pressures were expected to improve. The PA sensor confirmed this hypothesis. This is a novel use of the CardioMEMS sensor and may represent a potential application in the future in appropriate patients. Unfortunately, this is a single patient experience from our institute, which remains a limitation, however; we did not find a similar case or case series in literature.
Finally, our case study demonstrated that the CardioMEMS device can be used to monitor PA pressure in a TAH-t patient without technical interference between the two devices. In addition, the use of the CardioMEMS device in this population appears to be safe and can provide accurate pulmonary hemodynamic data to guide patient management and support transplantation listing. Further studies are needed to delineate the exact role of the CardioMEMS device in the current environment of mechanical circulatory support technology.
We thank the staff at Texas Heart Institute for their superb patient care.
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