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Pulmonary Pressure Assessment with the Total Artificial Heart

Joyce, David, L.*; Redfield, Margaret, M.; Kushwaha, Sudhir, S.; Behfar, Atta†,‡; Borlaug, Barry, A.; Daly, Richard, C.*; Sandhu, Gurpreet, S.†,‡; Joyce, Lyle, D.*

doi: 10.1097/MAT.0000000000000632
Case Reports
Conference Article

Reversal of pulmonary hypertension has been observed in patients during a bridge to transplant with a left ventricular assist device. Total artificial heart (TAH) implant prevents subsequent right heart catheterization. Consequently, controversy exists over whether the prosthetic right ventricle improves or exacerbates pulmonary hypertension. A pulmonary artery (PA) pressure monitor was placed in two patients undergoing TAH implant, as a bridge to transplant. One patient had pulmonary hypertension at implant; the other had normal pulmonary pressures. Daily measurements were taken of systolic, diastolic, and mean PA pressures throughout support. Patient 1 received successful transplant after TAH support of 91 days. Systolic/diastolic (mean) PA pressures steadily decreased from 55/39 (28) mm Hg at implant to 29/18 (7) mm Hg currently. Patient 2 received support for 101 days before death due to abdominal ischemic complications. Pulmonary arterial pressures stayed consistent throughout this period, from 26/17 (20) mm Hg at implant to 23/13 (17) mm Hg at the time of death. These findings suggest that an implantable PA pressure monitor may be useful in optimizing hemodynamics and planning appropriate timing of transplant with TAH support.

From the *Department of Cardiovascular Surgery, Mayo Clinic, Rochester, Minnesota

Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota

Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota.

Submitted for consideration September 2016; accepted for publication in revised form June 2017.

Disclosure: The authors have no conflicts of interest to report.

Mayo Clinic does not endorse specific products or services discussed in this article.

Presented as a podium presentation at the ASAIO 62nd Annual Conference; June 15–18, 2016; San Francisco, CA.

Correspondence: David L. Joyce, Division of Cardiovascular Surgery Medical College of Wisconsin 9200 W Wisconsin Ave Milwaukee, WI 53226

Cardiac transplant is contraindicated in the clinical setting of pulmonary hypertension because of the inability of the donor right ventricle (RV) to accommodate the increased afterload. Traditionally, pulmonary vascular resistance of more than 2.5 Wood units or a transpulmonary gradient of more than 12 mm Hg has been associated with worsening outcomes after heart transplant.1,2 Implant of a left ventricular assist device has been shown to reverse pulmonary hypertension in many patients, allowing for transplant listing after hemodynamic criteria are met on subsequent right heart catheterization.3 The impact of mechanical unloading is unknown with a total artificial heart (TAH) on pulmonary vascular resistance. Shah et al.4 recently published a small series of patients who received successful bridge to transplant with a TAH and improvement in pulmonary arterial (PA) pressures, transpulmonary gradient, and pulmonary vascular resistance in posttransplant heart catheterization. However, presence of two mechanical valves in the prosthetic RV of the TAH precludes ongoing measurement of pulmonary hemodynamics during the bridging period. We hypothesized that placement of an implantable PA catheter would both aid in TAH management during the bridging period and give insight on how rapidly pulmonary pressures can normalize after implant. We selected two patients for monitoring with a heart failure device (CardioMEMS; St. Jude Medical, Inc) before TAH implant.

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Case 1

A preoperative right heart catheterization showed significant increase in PA pressures of a 59-year-old man. On preimplant day 2, the patient was taken to the catheter laboratory for implant of a heart sensor (cardioMEMS) in the medial subsegmental branch of the left PA. The sensor was calibrated to PA catheter pressure recordings. After optimization for 2 days in the coronary care unit, the patient was taken to the operating room for implant of a TAH (SynCardia Systems, Inc., Tucson, AZ; Figure 1). The operation was performed through a median sternotomy with a cardiopulmonary bypass. Pressure recordings were performed daily postoperatively, showing an immediate drop in systolic, mean, and diastolic PA pressures. After support for 91 days, a donor organ became available and the patient underwent successful cardiac transplant. The postoperative recovery period was uneventful, with no clinically significant RV failure or other adverse events. Ongoing monitoring of PA pressures demonstrated normal hemodynamics out to 10 months posttransplant (Figure 2).

Figure 1

Figure 1

Figure 2

Figure 2

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Case 2

A 61-year-old man with end-stage dilated cardiomyopathy refractory to medical therapy presented with New York Heart Association (NYHA) class IV symptoms with hepatic congestion and hepatorenal syndrome. Preoperative right heart catheterization showed normal PA pressures in the clinical setting of severely increased right atrial pressure and RV failure. On the basis of these findings, the patient underwent heart sensor implant in the posteromedial branch of the left pulmonary artery, followed by TAH implant 5 days later.

In the immediate postoperative period, acute kidney injury developed, requiring dialysis. At the first hemodialysis attempt, the patient had substantial hypotension. These pressures were treated with albumin and norepinephrine, with subsequent removal of 2 L of fluid. An increase was seen in the levels of transaminases when a persistently elevated right atrial pressure prompted concern of inferior vena cava compression. Transthoracic echocardiography on postoperative day 2 showed a moderately dilated inferior vena cava (23 mm) with no inspiratory collapse. Nevertheless, concern continued about mechanical obstruction. By postoperative day 6, the concern of hepatic congestion driving increased liver function tests prompted a review of the PA pressure tracings from the heart sensor device. The pressures were substantially increased, from baseline (20/17 mm Hg) to 53/40 mm Hg, confirming substantial volume overload despite ongoing hemodialysis. Consequently, the patient was taken to the operating room for evaluation of pump position and possible tamponade.

At the time of reoperation, the pericardial space appeared to be free of any significant fluid or blood clots. Examination of the pump position did not reveal any mechanical source of obstruction to the inferior vena cava. Nevertheless, the right atrium appeared to be significantly enlarged. This clinical picture correlated closely with the hemodynamic data obtained from the PA pressure tracings. Given the challenges in achieving adequate volume removal with dialysis, a strategy was carried out to remove blood directly from the right atrial appendage, followed by slow retransfusion from the cell-saver device. This removal resulted in reduction of both right atrium pressure and PA tracings on the heart sensor device, with subsequent normalization of liver function tests. Although the patient ultimately had infectious complications that led to termination of support before transplant, the ability to correlate PA pressures with other markers of volume status had an important role in the patient’s postoperative treatment.

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These two cases demonstrate the feasibility of placing a heart monitor before implant of a TAH. Given the relatively small number of TAH implants annually, it is unlikely that a large series comparing this technique with traditional management strategies can be achieved. Nevertheless, the advantages derived from direct pressure monitoring for these two patients support the consideration of a combined implant strategy in selected patients.

One of the primary benefits of the implant of a heart monitor device derives from the enhanced volume management achieved through direct measurement of PA pressures. In the CHAMPION trial, this approach reduced heart failure admissions by 37% for patients with NYHA class III symptoms.5 Importantly, the heart sensor device was free from device or system complications in 98.6% of trial participants, suggestive of a highly favorable safety profile.5 Nevertheless, it should be noted that heart transplant recipients were not studied in the CHAMPION trial. Certainly, these patients are at increased risk for bloodstream infections, particularly in the clinical setting of bridging with a mechanical circulatory support device. For this reason, the low but real risks of subsequent infection of the device should be balanced against the advantages in treating these patients as described in this series.

Despite removal of native ventricles and implant of prosthetic replacements in the clinical setting of a TAH, volume management continues to be challenging for these patients. A recent review of 40 outpatient TAH recipients, supported with a portable driver (Freedom; SynCardia Systems, Inc.), reported 88 readmissions with the following symptoms at presentation: abdominal discomfort (12.5%), shortness of breath (11%), and fatigue (10%).6 In our experience, patients with biventricular failure typically present with some degree of renal insufficiency, which can make volume removal problematic even when the patient is receiving hemodialysis. The second case in the present series highlights these challenges; the patient ultimately required reoperation with volume removal directly from the right atrium to improve his filling pressures. One could make the case that direct measurement of the patient’s right atrial pressure in conjunction with the overall clinical picture could have resulted in the same decision making for this particular patient, given that a decrease in central venous pressure was observed after the intervention. However, in many instances, these types of volume management challenges occur much later during the bridge-to-transplant period when direct intravascular pressure measurements are not as easily obtained.

Each pump and each driver have intrinsic mechanical characteristics that to date have not been quantifiable after the TAH is implanted. The CardioMEMS heart sensor device may be helpful, particularly with a portable driver (such as Freedom [SynCardia]) because pump characteristics will be quantifiable directly from the device.

In our series of 10 patients who received successful bridge to transplant with a TAH before our CardioMEMS experience (unpublished data), two patients (20%) required posttransplant support of an RV assist device for residual pulmonary hypertension. Although the pathologic changes associated with advanced pulmonary hypertension are well described,7 the Heath-Edwards grading stage at which reversibility of this condition can occur has not been established for the time after mechanical unloading. With this uncertainty, direct measurement of PA pressures carries a considerable advantage in determining the optimal timing of cardiac transplant. Right heart catheterization represents an essential tool for the bridge-to-decision population, described as a central part of the diagnostic armamentarium in various studies.8–10 Therefore, it seems reasonable that patients who receive a TAH implant amid elevated PA pressures should benefit from direct monitoring in the same manner.

In summary, we believe that the advantages derived from improved volume management and monitoring of pulmonary hypertension, combined with the procedural safety of heart sensor implant before TAH, support consideration of merging these technologies for selected patients.

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bridge to transplant; pulmonary artery pressure monitor; pulmonary hypertension; total artificial heart

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