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Michiel Morshuis, Jochen Boergermann, Jan Gummert, Andreas Koster, A modified technique for implantation of the HeartWare™ left ventricular assist device when using bivalirudin anticoagulation in patients with acute heparin-induced thrombocytopenia, Interactive CardioVascular and Thoracic Surgery, Volume 17, Issue 2, August 2013, Pages 225–226, https://doi.org/10.1093/icvts/ivt187
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Abstract
In patients with acute heparin-induced thrombocytopenia (HIT) needing urgent cardiac surgery, bivalirudin is recommended as a first-line strategy for intraoperative anticoagulation. However, due to the unique elimination process of bivalirudin, careful adjustment of the perfusion and surgical strategy is mandatory as blood stasis in the circuit or prolonged interruption of areas or compartments containing blood from the systemic circulation may result in thrombus formation. We report here a modified surgical strategy for the implantation of the HeartWare™ left ventricular assist device, which avoids prolonged disconnection of the blood-filled device from the systemic blood flow, so that bivalirudin can be safely used as anticoagulant.
INTRODUCTION
Heparin-induced thrombocytopenia (HIT) is an immune-mediated disease, which may lead to massive platelet and thrombin activation with subsequent thromboembolism (TE) [1]. The incidence of HIT in patients undergoing ventricular assist device (VAD) implantation is described to be ∼10%, and the outcome is detrimental [2, 3]. However, early recognition of the disease and consequent use of alternative anticoagulation protocols appear to improve outcomes [3].
In patients with acute HIT needing cardiac surgery, bivalirudin is recommended as first-line strategy for intraoperative anticoagulation [1]. Bivalirudin has a short elimination half-life of 25 min and is mainly cleared via enzymatic cleavage by thrombin [1]. This has implications for surgery with cardiopulmonary bypass (CPB), as any region of stasis of blood in the system/patient, or areas of blood being disconnected from the systemic blood flow, which maintains bivalirudin concentrations, may lead to a critical decrease in the regional bivalirudin concentrations and causes thrombus formation. Therefore, when bivalirudin is used as anticoagulant during cardiac surgery, careful adjustment of the perfusion and surgical technique is mandatory [4]. We report here on a modified implantation technique for the HeartWare™ left VAD allowing the use of bivalirudin as anticoagulant.
The standard implantation technique
The driveline exit is prepared, and the driveline tunnelled and connected to the controller system. The sewing ring is attached to the epicardial surface of the left ventricular apex. After fixation of the ring with pledgeted sutures, a cruciform incision into the myocardium within the centre of the ring is performed, and the ventriculotomy is completed by insertion of the left ventricle punch. The inflow cannula is inserted into the ring and secured by tightening integrated screws. The ventricle is loaded and the device de-aired antegradely. The outflow graft is clamped, and an end-to-side anastomosis to the aorta is performed. Thereafter, the partial aortic cross-clamp is released and the device may be started [5].
However, using this technique, from the beginning of the de-airing of the device until removal of the partial aortic cross-clamp and start of the system, the blood within the device is disconnected from the systemic circulation. In case bivalirudin is used as anticoagulant, this may lead to a critical decrease in the bivalirudin concentration and thus cause thrombus formation within the system and consecutive arterial TE. Therefore, we recommend a modified implantation strategy, similar to the off-pump technique performed via left mini-thoracotomy and mini-sternotomy [6], when using bivalirudin anticoagulation.
The modified implantation strategy
The driveline exit is prepared, and the driveline tunnelled and connected to the controller system.
The sewing ring is attached to the epicardial surface of the left ventricular apex. Thereafter, the end-to-side anastomosis of the outflow graft to the aorta is performed. Having done this, the partial aortic cross-clamp is removed, the device de-aired retrogradely through the outflow graft, the ventriculotomy performed on the fibrillated heart by using the punch, the ventricle loaded and de-aired and the de-aired inflow cannula inserted into the ring. The heart is defibrillated and the system slowly started while the fixation screws are tightened.
Using this approach, the time of disconnection of the blood in the device from the systemic circulation is reduced to a minimum (60–90 s), so that any thrombus formation is unlikely to happen.
We have successfully employed this strategy with standard open CPB systems and cardiotomy suction using the standard bivalirudin dosing for CPB (1 mg bolus for the patient, 50 mg into the CPB, continuous infusion of 2.5 mg/kg/h bivalirudin during CPB) [7].
In patients bridged to left ventricular assist device implantation by implantation of a completely closed fem–fem arterio/venous extracorporeal membrane-like extracorporeal life support system (Cardiohelp, Maquet, Wayne, NJ, USA), we have performed this strategy using a lower dose of bivalirudin (0.5 mg bolus for the patient followed by a continuous infusion of 0.5 mg/kg/h during surgery) while replacing cardiotomy suction by the use of a cell saver [8].
Viewing our favourable experience employing the extracorporeal life support system with the reduced bivalirudin dose, we recommend the preferable use of this strategy when no concomitant open heart surgery is necessary.
Conflict of interest: none declared.
