ABIOMED RVAD and LVAD Implantation

Abstract

1)esl)itr atlcanws i n oi)vrativt, tec*lniic~ues ant1 sltill, ant1 1)artly e\ac.erl)atrtl I)! 1)atients lwing referre(1 ior rartliac surgical procetlures at atlc aricetl stagrs of tlisease, postoperative centricular tl! sfmication is not uncommonly seen. In ul) to 10% of high-risk patients in whom carc1iol)lmonary I n pass is used ~ an intra-aortic halloon pun111 (L4BP) is required for separation from 1)jpass. ' Because an IABP will augment cardiac out1)ut 1)) only 10% to 15%some patients will require more significant ventricular support such as froin left (L\:ADs) antl right ventricular assist tlecices (RVADs). Furthermore. excessiv e doses of inotropes can he avoitled. In 199%. the Food and Drug Administration (FDA) approved the ABIOMED (ABIOMED, Inc, Danvers, MA) BVS 5000 Biventricular Support Sjstem for postcarcliotoiny ventricular dysfunction.' The device was designed to provide pulsatile left weiitriculai-. right ventricular, o r hiventricular support (BVS) with minimal cost antl ininin~al complexity of implantation and operation. ' The system consists of single-use blood pumps that a re actuated b y a pneumatic drive console. Each pump is attached to an intravenous pole a t the liedside. allowing its height relative to the atrium to lie adjusted. This facilitates gravitational control of pump filling. Each blood pump (Fig I) allows unidirectional flow of Hood into two chambers, a filling (atrial) chamber and a pumping (ventricular) chamber. Two tri-leaflet Angioflex (ABIOMED, Inc, Danvers, MA) polyurethane valves a re seamlessly interposed on either side of the ventricular chamber, allowing only for unidirectional flow. Each chamber contains a smooth-surfaced polyurethane hladder. As the ventricular bladder fills, air surrounding it is displaced to the console. The console's electronics sense filling of the pumping chainher and return pressurized air to the outside of the chamber, causing ejection of the blood. The system is modulated to pump at a rate that allows for 70 to 80 mllejection and flows of up to 6 Llmin. During operation, pump filling is determined b y the position of the blood pump relative to the level of the atrium. The pump output can lie manually decreased during weaning, hut otherwise, it is controlled automatically. Since its approval for use. the intlication~ for the device have expanded to include use in selected patients who suffer significant cardiac dysfunction. wlitw recovery is likely such as in postcardiotomy shocli. failed cardiac transplantation, right heart failure a f te r LC placemvntnf' acutts in! oc-artlial infarction with 4 iock . antl viral niyocarclitis. 6 It h a < also 1)een succeisful ly nsetl in treatment of patients with intractable ventricular tachycardiax and rhetuiiiatic pricartlitiz. Even wheii cardiac recovery is tlouhtful, the device may he nsed as a IiritIge-to-transplantation. '.' ' Patients with pstcar t l iotomj failure stJlectetl for BVS should have liatl a technically successful operation hut fail to tolerate separation from carcliol)uliiionar! bypass as evidenced h y a cardiac index Ijelow 8.0 Llminlm', central venom pr lire and left atrial pressure greater than 18 niin Hg, and SVOL (mixed venous oxygen saturation) less than 55% despite hemoglo1)in correction antl significant inotropic support. Patients should also 1)e of a reasonable physiological age and have a body surface area greater than 1.3 in'. Ideally, they should he recognized as candidates quiclily, certainly well within 6 hours of initiation of cardiopulmonary hypass. Whether o r not an IAPB is used, transesophageal echocartliography can lie quite useful in determining the ventricular function and in assessing a patient's need for ventricular assistance. More importantly, assessment for a patent foramen ovale should be performed. This would require closure to prevent right-to-left shunting of desaturated blood with left-sided support. Contraindications to the use of the BVS 5000 may include renal failure, severe liver disease, metastatic cancer, uncontrolled sepsis, interstitial pulmonary hemorrhage with inadequate pulmonary function, severe hemolysis. uncontrollable hemorrhage, and significant central nervous system injury. The device is relatively straightforward to implant and requires minimal I~edside adjustment. Several cannulae a re available for use in insertion of the BVS 5000 device (see 1 in the Surgical Technique (ST) section). All have an attached Dacron (E.I. DuPont de Nemoiirs and Co, Inc, Wilmington, DE) velour sleeve, which is to be positioned at the exit site from the skin in order to improve hemostasis and encourage tissue adherence and ingrowth. There a re two atrial cannulae: a malleable tip 36F antl a right-angled 4ZF cannula with a lighthouse tip. The arterial cannula is a 42F cannula with a 14-mm elastomer-coated Dacron graft distally. Plastic hullet tips a re provided to allow passage of the cannulae out of the pericartlial cavity through subcutaneous tunnels and the skin (see 1 in ST). There a re three options for left atrial cannulation: through the dome of the left atrium hetween the superior vrna cava