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Case Reports

The HeartMate 6 and CardioMEMS for Fixed Pulmonary Hypertension

Angleitner, Philipp*; Schlöglhofer, Thomas*; Wiedemann, Dominik*; Riebandt, Julia*; Strassl, Andreas; Mascherbauer, Julia; Kainz, Matthias§; Laufer, Günther*; Zuckermann, Andreas*; Zimpfer, Daniel*

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doi: 10.1097/MAT.0000000000001480
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Abstract

Implantation of two Abbott HeartMate 3 ventricular assist devices (VADs) in a total artificial heart (TAH) configuration has been described as a viable option for the treatment of end-stage heart failure (“The HeartMate 6”).1 At our center, a young patient (male, age 35 years, Interagency Registry for Mechanically Assisted Circulatory Support profile 4) presented with a diagnosis of apical hypertrophic cardiomyopathy (Yamaguchi syndrome) with extensive left-ventricular endocardial calcification (Figure 1A). Right-heart catheterization revealed severe fixed pulmonary hypertension (FPH) (systolic pulmonary artery pressure [sPAP], 102 mm Hg; diastolic PAP [dPAP], 59 mm Hg; mean PAP [mPAP], 77 mm Hg; transpulmonary gradient, 28 mm Hg; pulmonary vascular resistance: 5.4 Wood units). Given the severe left-ventricular endocardial calcification combined with FPH, our patient had an indication for TAH implantation as a bridge to candidacy (BTC) for heart transplantation (HTX).2

F1
Figure 1.:
Intraoperative images at the time of total artificial heart (TAH) implantation show extensive left-ventricular endocardial calcification (A), right-sided and left-sided HeartMate 3 sewing rings (B), and the TAH in its final configuration (C).

Technique

To continuously measure PAP values after elective TAH implantation, an Abbott CardioMEMS pressure sensor was implanted into the pulmonary arterial tree in standard technique.3 Percutaneous femoral venous access was obtained to catheterize the left-sided pulmonary artery. A dorsal lower-lobe branch with a diameter of approximately 8 mm was localized to place the sensor’s body and distal loop (Figure 2A and B). Peak sPAP values of 110 mm Hg and mPAP values of 83 mm Hg were confirmed (Figure 3A).

F2
Figure 2.:
Chest radiograph, frontal (A) and lateral view (B), showing the Abbott CardioMEMS sensor localized in a dorsal lower-lobe branch of the left-sided pulmonary artery (arrows).
F3
Figure 3.:
Pulmonary artery pressure (PAP) dynamics as monitored by the Abbott CardioMEMS pressure sensor before total artificial heart (TAH) implantation (A), postoperatively (B), and after heart transplantation (HTX) (C).

Two weeks later, we proceeded with TAH implantation. A standard median sternotomy was performed. After administration of heparin, the ascending aorta was cannulated for cardio-pulmonary bypass (CPB). Venous drainage was obtained via bi-caval cannulation. Total CPB was established and the aorta was cross-clamped. During the procedure, carbon dioxide was insufflated into the operative field to reduce the risk of air embolus formation. The ascending aorta and pulmonary artery were disconnected. Both ventricles were excised at the level of the atrioventricular valves. Extensive endocardial calcification of the left ventricle was confirmed intraoperatively (Figure 1A). The mitral and tricuspid valve leaflets were resected, preserving the mitral and tricuspid annulus to facilitate implantation of HeartMate 3 sewing rings. Attention was paid to the dimensions of both atria to anticipate potential interactions with HeartMate 3 inflow cannulas. Careful inspection revealed no thrombi or residual endocardial trabeculae. The left atrial auricle was amputated and the coronary sinus was suture closed.

Two Abbott HeartMate 3 VADs were set up according to standard instructions for use. Two cuffs were created by attaching HeartMate 3 sewing rings to the remaining tissue of the left and right atrium (Figure 1B). Both suture lines were reinforced using felt rings. Then, the right-sided VAD was connected to the right atrial cuff and the outflow graft was anastomosed to the pulmonary arterial. Next, the left-sided VAD was inserted into the left atrial cuff and the outflow graft was anastomosed to the aorta in end-to-end technique (Figure 1C). Both drivelines were tunneled through the left and right lower abdominal wall. For the de-airing procedure, the right-sided VAD was started first. Then, the left-sided VAD was started and de-aired via a vent in the ascending aorta before removing the aortic cross-clamp. Weaning from CPB was commenced upon reaching hemodynamic equilibrium between both VADs (left-sided VAD: 5.8 L/min, 6400 revolutions per minute [RPM]; right-sided VAD: 5.3 L/min, 5800 RPM). Great care was taken to avoid over-pumping of the pulmonary arterial circulation to minimize the risk of pulmonary edema. Protamine was administered and point-of-care coagulation management was initiated. Meticulous hemostasis was sought to reduce the risk of postoperative bleeding.4

Following a period of stabilization during the first 24 hours after surgery, hypocoagulation was commenced according to institutional protocol. On the first postoperative day (POD), unfractionated heparin (UFH) was started to reach target activated partial thromboplastin time (aPTT) values between 45 and 50 seconds. On POD 2, the UFH rate was increased to reach aPTT values between 50 and 60 seconds, and between 70 and 75 seconds after POD 3. Additionally, antiplatelet therapy was started on POD 2 (aspirin 100 mg/day). During the later postoperative hospital stay, anticoagulation was switched to low-molecular weight heparin, aiming at peak anti-Xa activity values between 0.2 and 0.4 IU/ml. Before discharge, warfarin was initiated to reach international normalized ratio values between 2.5 and 3.5.5

Following TAH implantation, PAP values gradually improved (sPAP 51 mm Hg; mPAP, 47 mm Hg; Figure 3B). Notably, the effect of the HeartMate 3 artificial pulse is clearly visualized in the 10 s PAP snapshot recording in Figure 3B. The rotor speed is varied every 2 seconds from the user-set speed by a 0.15 s decrease (2000 RPM) followed by a 0.20 s increase (4000 RPM), resulting in changes in blood flow and PAP.6 Standard evaluation for HTX listing was commenced, including contrast-enhanced computed tomography of the chest (Figure 4). The patient was listed 55 days after TAH implantation and underwent orthotopic HTX after 61 days of uneventful TAH support. Orthotopic HTX was performed in a standard fashion. The patient was extubated on POD 2 and discharged on POD 36. Importantly, PAP values remained stable on near-physiologic levels following HTX (sPAP 40 mm Hg; mPAP, 27 mm Hg; Figure 3C).

F4
Figure 4.:
Three-dimensional computed tomography reconstruction (cinematic volume rendering technique) shows anatomic relations between the total artificial heart (TAH) and the chest.

Comment

FPH is a common finding in HTX candidates that can be reversed after left-ventricular assist device (LVAD) implantation by continuous left-ventricular unloading.7 However, certain anatomic situations (e.g., severe left-ventricular calcification or hypertrophic cardiomyopathy) mandate implantation of a TAH. Whenever a TAH implantation is indicated, assessment of PAP by right-heart catheterization becomes technically impossible.

In the presented patient, a CardioMEMS pressure sensor was utilized to continuously evaluate PAP dynamics after TAH implantation and demonstrate a sustained reduction of PAP values to make the patient eligible for HTX (Figure 3B). The sensor might as well be utilized to detect pulmonary overflow and pulmonary congestion at an early stage in outpatient VAD and TAH recipients, potentially reducing the risks of readmission and mortality.8

Importantly, our patient did not develop any peri-procedural or long-term complications after implantation of the CardioMEMS sensor, a finding that is in line with a previously reported complication rate of approximately 1% in the CHAMPION trial.3 Moreover, we did not detect interferences between the CardioMEMS sensor and TAH electronics during the time of TAH support. After HTX, the sensor remains in situ and might be utilized to guide clinical management if necessary.

To conclude, we present a successful BTC strategy in a patient presenting with Yamaguchi syndrome and FPH. Prospective studies of larger cohorts are necessary to evaluate outcomes after implantation of the Abbott HeartMate 6 and CardioMEMS pressure sensor.

References

1. Daneshmand MA, Bishawi M, Milano CA, Schroder JN: The HeartMate 6. ASAIO J 66: e46–e49, 2020.
2. Potapov EV, Antonides C, Crespo-Leiro MG, et al.: 2019 EACTS Expert Consensus on long-term mechanical circulatory support. Eur J Cardiothorac Surg 56: 230–270, 2019.
3. Abraham WT, Stevenson LW, Bourge RC, Lindenfeld JA, Bauman JG, Adamson PB; CHAMPION Trial Study Group: Sustained efficacy of pulmonary artery pressure to guide adjustment of chronic heart failure therapy: complete follow-up results from the CHAMPION randomised trial. Lancet 387: 453–461, 2016.
4. Angleitner P, Simon P, Kaider A, et al.: Impact of bleeding revision on outcomes after left ventricular assist device implantation. Ann Thorac Surg 108: 517–523, 2019.
5. Sandner SE, Riebandt J, Haberl T, et al.: Low-molecular-weight heparin for anti-coagulation after left ventricular assist device implantation. J Heart Lung Transplant 33: 88–93, 2014.
6. Bourque K, Cotter C, Dague C, et al.: Design rationale and preclinical evaluation of the HeartMate 3 left ventricular assist system for hemocompatibility. ASAIO J 62: 375–383, 2016.
7. Zimpfer D, Zrunek P, Roethy W, et al.: Left ventricular assist devices decrease fixed pulmonary hypertension in cardiac transplant candidates. J Thorac Cardiovasc Surg 133: 689–695, 2007.
8. Veenis JF, Manintveld OC, Constantinescu AA, et al.: Design and rationale of haemodynamic guidance with CardioMEMS in patients with a left ventricular assist device: The HEMO-VAD pilot study. ESC Heart Fail 6: 194–201, 2019.
Keywords:

HeartMate 6; CardioMEMS; fixed pulmonary hypertension; total artificial heart

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