CASE 13—2016 Minimally Invasive Left Ventricular Assist Device Insertion Without Cardiopulmonary Bypass

Author’s Accepted Manuscript Minimally Invasive Left Ventricular Assist Device Insertion Without Cardiopulmonary Bypass Sebastian Bienia, Andrew Feider, Rima Griauzde, Kamal D. Patel, Mohammed M. Minhaj www.elsevier.com/locate/buildenv

PII: DOI: Reference:

S1053-0770(15)01064-2 http://dx.doi.org/10.1053/j.jvca.2015.12.029 YJCAN3526

To appear in: Journal of Cardiothoracic and Vascular Anesthesia Received date: 17 December 2015 Cite this article as: Sebastian Bienia, Andrew Feider, Rima Griauzde, Kamal D. Patel and Mohammed M. Minhaj, Minimally Invasive Left Ventricular Assist Device Insertion Without Cardiopulmonary Bypass, Journal of Cardiothoracic and Vascular Anesthesia, http://dx.doi.org/10.1053/j.jvca.2015.12.029 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Minimally Invasive Left Ventricular Assist Device Insertion Without Cardiopulmonary Bypass Sebastian Bienia, M.D. Resident McGaw Medical Center of Northwestern University 251 East Huron Street, F5-711 Chicago, IL 60611 Phone: 312-695-0061 Fax: 312-695-9013 Email: [email protected] Andrew Feider, M.D. Assistant Professor of Anesthesiology Northwestern University Feinberg School of Medicine 251 East Huron Street, F5-711 Chicago, IL 60611 Phone: 312-695-0061 Fax: 312-695-9013 Email: [email protected] Rima Griauzde, M.D. Instructor Department of Anesthesiology Northwestern University Feinberg School of Medicine 251 East Huron Street, F5-711 Chicago, IL 60611 Phone: 312-695-0061 Fax: 312-695-9013 Email: [email protected] Kamal D. Patel, M.D. Associate Clinical Professor Cardiothoracic Anesthesiology David Geffen School of Medicine at UCLA 757 Westwood Plaza, Suite 3325 Los Angeles, CA 90095 Phone: 310-267-8693 Fax: 310-267-3899 Email: kdpatel @mednet.ucla.edu 1 Mohammed M. Minhaj, M.D., M.B.A. Associate Professor University of Chicago Medical Center 5841 S. Maryland Ave., MC 4028 Chicago, IL 60637 Phone: 773-702-5511 Fax: 773-834-0063 Email: mminhaj @dacc.uchicago.edu Corresponding Author: Rima Griauzde, M.D. Department of Anesthesiology

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Northwestern University Feinberg School of Medicine 251 East Huron Street, F5-711 Chicago, IL 60611 Phone: 312-695-0061 Fax: 312-695-9013 Email: [email protected] 2

INTRODUCTION

Left ventricular assist device (LVAD) implantation for end-stage heart failure has conventionally been performed via a median sternotomy with the aid of cardiopulmonary bypass (CPB)1,2. Advances in LVAD design have led to changes in operative techniques, including using minimally invasive incisions and omitting the use of CPB. These approaches mitigate the risks of extracorporeal support and median sternotomy. The shift to a minimally invasive, off-pump approach for LVAD implantation necessitates new perioperative management considerations, including the use of real-time transesophageal echocardiography (TEE) guidance. The authors present the perioperative anesthetic considerations for surgical implantation of a HeartWare ventricular assist device (HVAD) (HeartWare International, Inc, Framingham, Mass) via a mini-hemisternotomy and minileft anterior thoracotomy without the use of CPB and highlight the key concepts.

CASE PRESENTATION

A 65-year-old male weighing 84 kg with a body-mass-index of 37 presented from a referring hospital for consideration of advanced heart failure therapies. His past medical history included New York Heart Association Class III, stage D, chronic systolic heart failure secondary to non-ischemic cardiomyopathy, paroxysmal atrial fibrillation, remote 2   

cerebral vascular accident, and chronic renal insufficiency. Cardiac resynchronization therapy (Medtronic CRT-D) had been instituted four years ago. One month prior to admission, he had been admitted to an intensive care setting and treated pharmacologically for acute-on-chronic decompensated heart failure and acute-onchronic kidney injury, with a preoperative creatinine of 1.9 mg/dL. Recent cardiac workup was significant for left ventricular dilation (end diastolic dimension 7.6 cm), a severely reduced left ventricular ejection fraction (LVEF) of 10%, and mild coronary artery disease. There was no evidence of pulmonary hypertension. In order to qualify for IA status on the United Network for Organ Sharing cardiac transplant list (UNOS) and decrease overall waiting time, he underwent pulmonary artery catheterization and was started on intravenous dobutamine (1 mcg/kg/min) and dopamine (1 mcg/kg/min). The cardiology and cardiac surgery teams felt that the patient would continue to clinically decline and likely would not survive until a heart became available. LVAD implantation was thus planned as a bridge to cardiac transplantation. The operative plan included insertion of an HVAD through a mini-left anterior thoracotomy and mini-upper hemisternotomy without the aid of CPB. This technique was chosen instead of traditional median sternotomy to decrease complications associated with a redo sternotomy when the patient would eventually undergo heart transplantation. Furthermore, avoiding CPB in appropriate patients would potentially avoid exposure to the systemic inflammatory response, coagulopathy, and transfusion requirements.

After obtaining informed consent for surgery and anesthesia, the patient was transported to the operating room and standard non-invasive monitors and external defibrillator pads

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were placed. The patient’s automated internal cardiac defibrillator was interrogated and the underlying rhythm was noted to be sinus rhythm. The tachycardia detection function was de-activated and the pacemaker settings changed to DDD at 70 beats/min (bpm). Preoperative inotropic support was continued during the peri-induction period. After cannulation of the left radial artery, general anesthesia was induced with 10 mg of midazolam, 250 mcg of fentanyl, and 100 mg of rocuronium. Mask ventilation and endotracheal intubation with a single-lumen endotracheal tube proceeded uneventfully and general anesthesia was maintained with inhaled isoflurane (0.4%-1.0%), fentanyl, midazolam, and rocuronium. A 5 g aminocaproic acid bolus was given and an infusion of 1 g/hr was continued intraoperatively because full dose heparin (400 U/kg) was to be given.

A large bore central venous introducer sheath was inserted into the right internal jugular vein through which a continuous cardiac output pulmonary artery catheter was inserted. Finally, a TEE probe was placed atraumatically. Initial echocardiographic examination revealed a severely dilated and globally hypokinetic left ventricle with no evidence of thrombus. The LVEF was estimated to be approximately 10%. The right ventricular size and function were normal. The right atrium was noted to be normal. The left atrium was severely dilated, but without evidence of atrial appendage thrombus. There was no evidence of inter-atrial shunting by color Doppler or saline bubble contrast study. The aortic valve was tri-leaflet and opened well, with trace aortic insufficiency and no stenosis. The mitral valve appeared normal in structure, with mild regurgitation and no stenosis. The tricuspid valve appeared normal in structure, with mild insufficiency and no

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stenosis. The pulmonic valve was not well visualized. The great vessels appeared normal in size. Protruding atheromas (less than 5 mm) were noted in the aortic arch and descending aorta.

The surgical team cannulated the right femoral artery for central arterial blood pressure monitoring. Under echocardiographic guidance, a wire was percutaneously advanced into the right atrium via the right femoral vein in the event that emergent CPB was required. Initial incision was made via the left sixth intercostal space and dissection was carried down to expose the apex of the left ventricle. The surgeon directly palpated the left ventricular apex and the indentation was identified using TEE in the four chamber (zero degree) mid-esophageal view along with the two chamber (90 degree) mid-esophageal view using the x-plane function. The optimal position was then marked and a spinal needle was passed through the identified location and aligned parallel to the ventricular septum, with the tip directed toward the opening of the mitral valve (Figure 1). Over the next fifteen minutes, the sewing ring of the HVAD was then secured to the left ventricular apex without untoward hemodynamic effects (Figure 2).

Subsequently, the upper hemi-sternotomy was performed via the third intercostal space, allowing for visualization of the ascending aorta. A tunneling device was used to create a tract and channel the driveline from the thoracotomy incision to an exit site between the umbilicus and left anterior superior iliac crest (Figure 3). The patient was then systemically anticoagulated with full dose heparin (400 U/kg), with a resultant activated clotting time (ACT) of 578 seconds prior to device implantation. Because the procedure

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was to be performed without CPB, technically an ACT of 250 seconds would potentially be appropriate. Yet in critically ill patients, with unstable hemodynamics, we use full dose heparin with an ACT goal of 480 seconds for safety purposes. The ACT was monitored every thirty minutes, until heparin reversal.

Temporary epicardial ventricular pacing wires were placed and the patient was rapidly paced (180 bpm) with a consequent mean arterial pressure between 20-40 mmHg. During ventricular pacing, a linear incision was made within the sewing ring and the coring device placed through the incision and deployed. Coring of the left ventricular apex lasted about one minute. Rapid pacing was then discontinued and the surgeon occluded the ventriculotomy site while the patient’s blood pressure was given time to recover with the assistance of titrated boluses of intravenous norepinephrine. Rapid pacing was then reinstituted and the inflow cannula was inserted into the left ventricle and the sewing ring secured over the cannula. The graft was subsequently de-aired and tunneled under the pericardium toward the hemisternotomy incision (Figure 3). Intravenous epinephrine (2 mcg/min) and milrinone (0.25 mcg/kg/min) were started prior to creation of the outflow graft anastomosis to assist with right ventricular function. A milrinone bolus was not given to avoid profound hypotension. Aortotomy was made using a side-biting aortic clamp placed on the ascending aorta and an end-to-end anastomosis was created between the outflow graft and ascending aorta over the course of fifteen minutes. Prior to completion of the anastomosis, clamps on the outflow graft were removed and the device and graft were allowed to de-air. Once connected, the device was activated and speed gradually increased to 2600 revolutions per minute (RPM) with an adequate waveform

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and flow (Figure 4). Oxygen saturation and systemic and pulmonary arterial pressures remained stable throughout this process. Echocardiography confirmed that the inflow cannula was well seated, with the opening directed towards the mitral valve (midesophageal views of the left ventricle at 0, 90, and 140 degrees) and the outflow cannula was well seated in the ascending aorta (upper esophageal view of ascending aorta at 0 and 90 degrees) with minimal excursion of air bubbles (mid-esophageal view of distal arch at 0 and 90 degrees). Flow velocities through the outflow cannula were measured at 2.2 m/sec. LVAD flows were adjusted to maintain a left ventricle that appeared well decompressed, with the ventricular septum in a midline position, and with the aortic valve opening approximately every three cardiac cycles. There was no evidence of right heart distention or dysfunction, worsening aortic or tricuspid regurgitation, intra-atrial shunting, or aortic dissection.

With adequate hemostasis and hemodynamics, heparin was reversed with protamine (0.5 mg/100 U heparin) and the ACT returned to the baseline level. Surgical closure proceeded without complication (Figure 5). In total, the patient received approximately two liters of crystalloid fluid and three units of fresh frozen plasma intraoperatively. No other blood products were transfused. He maintained adequate urine output (greater than 1 mL/kg/hr) through the course of the operation and was transported to the cardiothoracic intensive care unit intubated, in stable condition, on low dose infusions of milrinone, norepinephrine, and epinephrine. The patient was extubated four hours after surgery. The patient’s postoperative course progressed uneventfully, with no further blood product transfusions required. Laboratory tests, including renal function studies, remained stable.

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He was weaned entirely from inotropic support on postoperative day seven and ultimately was discharged from the hospital on postoperative day ten. DISCUSSION

The introduction of the HVAD represents the third-generation of implantable LVADs. Indications for placement of an LVAD include use as bridge-to-myocardial recovery, transplantation, or as destination therapy. To date, studies have demonstrated that the HVAD is non-inferior to currently available devices in terms of survival 3. The HVAD is a smaller, bearing-less, continuous-flow, centrifugal pump with an integrated inflow cannula that is implanted directly into the left ventricular apex. The miniaturized design and integration of the inflow cannula with the pump allow it to be positioned within the pericardium, avoiding the need for a device pocket in the abdomen as required in secondgeneration LVADs such as the HeartMate II (Thoractec Corporation, Pleasanton, CA, USA). The outflow graft is typically anastomosed to the ascending aorta but other sites such as left subclavian, or descending aorta have been described 4,5. The implantation of LVADs, including the HVAD, has generally been performed via a median sternotomy with the aid of CPB. An alternative approach has been described for devices such as the Jarvik 2000 Heart (Jarvik Heart, New York, NY), which involves a full left lateral thoracotomy at the sixth intercostal space for left ventricular pump implantation and outflow graft anastomosis to the descending thoracic aorta 6. Of note, the thoracotomy approach necessitates lung isolation via a double-lumen endotracheal tube or bronchial blocker to facilitate surgical exposure and reduce lung trauma in anticoagulated patients. The thoracotomy approach has been performed both on-pump and off-pump 7.

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The smaller size and device configuration of the HVAD lends itself to being placed via minimally invasive incisions in place of a median sternotomy or full thoracotomy. Several case reports and small case series with highly experienced cardiac teams have outlined implantation via minimally invasive off-pump approaches 8-14. In general, two small incisions are required: one mini-left anterior thoracotomy and one upper T-inverted mini-sternotomy, for exposure of the left ventricular apex and the great vessels, respectively. Given the direct exposure of the left ventricular apex, lung isolation is not required. Greater reliance is placed on TEE guidance in planning and placement of the HVAD in this method as the surgeon and anesthesiologist are unable to rely on direct visualization of the heart in the field. Off-pump LVAD implantation also requires a form of temporary cardiac decompression during the ventriculotomy to prevent hemorrhage as well as entrainment of air into the left ventricle and coronary circulation, which could cause ischemia and cardiac failure. Methods include rapid ventricular pacing, inducing ventricular fibrillation, and/or injecting high-dose adenosine to induce temporary asystole. The authors are accustomed with rapid ventricular pacing using temporary epicardial leads placed by the surgeon in the field. Practically speaking, rapid ventricular pacing is preferred on account of its simplicity. End-stage heart failure patients who are pacemaker dependent require continued pacing intraoperatively in asynchronous mode, therefore, precluding use of adenosine to induce temporary asystole. Inducing ventricular fibrillation would ultimately require defibrillation, which may be difficult via external defibrillator pads in patients who are prone to lethal arrhythmias. Variations of the offpump minimally invasive techniques have been explored successfully in cases such as

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explanation of an HVAD after myocardial recovery and explantation and exchange of HVAD for pump thrombosis or cable damage 5,15-17.

The approach to the anesthetic management of an off-pump minimally invasive HVAD implantation should be individually tailored to each patient. In our Institution, the preferred method includes combining a short-acting benzodiazepine and opioid with a volatile agent and an intermediate duration non-depolarizing muscle relaxant such as rocuronium. During induction, substitution for a hemodynamically stable agent such as etomidate lowers the total dose of benzodiazepine and may facilitate earlier extubation. In addition to standard and invasive monitors, external defibrillator pads should be placed in the pre-induction period as the heart will not be accessible for internal defibrillator paddles in case the need for emergent defibrillation arises. Warming measures should be instituted, including forced air warming devices, increased ambient temperatures, and fluid warmers to ensure normothermia intraoperatively. A perfusion team should be on stand-by with a primed CPB circuit prior to induction in the event of hemodynamic collapse. Invasive arterial blood pressure catheters should be placed, ideally both peripherally as well as centrally via the femoral artery. The femoral artery catheter may be converted to an intraaortic balloon pump or an arterial cannula for CPB if either is needed. Large bore intravenous access should be obtained due to the potential need for rapid volume or blood product transfusion. We recommend placement of pulmonary artery catheter for monitoring pulmonary artery pressures, continuous cardiac output, and mixed venous oxygen saturation for intraoperative and postoperative monitoring.

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Once induction is complete and the monitors have been placed, a pre-incision TEE evaluation should be performed. As with the standard perioperative TEE exam, the preincision exam should carefully evaluate the right heart function, the integrity of the aorta, presence and severity of tricuspid regurgitation, mitral stenosis, aortic insufficiency, intracardiac shunts, and atrial, ventricular, or apical thrombus formation 18,19. If moderate to severe right-sided cardiac dysfunction is present, it may be more prudent to implant the LVAD on-pump to avoid the increased risk of right ventricular failure with pump initiation. The aortic root should be assessed for abnormalities in size, integrity, and atheromatous disease. If the aorta is diseased, then a separate site for outflow graft anastomosis may be necessary. The presence of intracardiac thrombus would require CPB and open visual inspection and clot removal so as to prevent pump thrombosis and cerebral embolization. In general, the following cardiac lesions that would require correction in a conventional surgical approach before LVAD implantation: intracardiac shunts, severe tricuspid regurgitation, mitral stenosis, and aortic insufficiency. Uncorrected tricuspid regurgitation could lead to chronic right heart failure and poor flow through the pulmonary system. Mitral stenosis could lead to poor left ventricular filling and decreased LVAD flows. An intracardiac shunt would need to be corrected in order to prevent right-to-left shunting of blood, which is more likely to occur after LVAD therapy is initiated and the left ventricular is unloaded. In the case of moderate or severe aortic insufficiency, initiation of the LVAD would lead to inadequate forward systemic flow, with most of the LVAD outflow moving retrograde into the left ventricle. In this case, the aortic valve would need intervention by either replacement or closure technique.

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Peripheral bypass cannulas should be placed with TEE guidance and confirmation of position in the event circulatory support is needed. Central cannulation can be considered if exposure permits it. Subsequently, the incisions for the left ventricular apex and ascending aorta cannulation sites should proceed. Placement of the integrated pump and inflow cannula begins with exposure of the left ventricular apex via a mini-anterior thoracotomy. This dissection typically is done at an intercostal space between the fourth and sixth rib spaces. Since this is an anterior approach and not a left lateral thoracotomy, it does not require lung isolation to facilitate exposure of the left ventricle. Given the reduced exposure of the left ventricle, however, identifying the appropriate space for the thoracotomy incision is important. Utilization of a sterile ultrasound probe can aid in locating the ideal space for left ventricle apex exposure. Once the left ventricle is exposed, the site for inflow cannula placement is chosen using a combination of direct palpation and/or spinal needle placement under real-time TEE guidance 14. The midesophageal four chamber and two chamber views are the most helpful for identifying proper location and orientation of the spinal needle as well as the inflow cannula after placement is completed. The inflow cannula should ultimately be directed axially toward the mitral valve opening, parallel to the interventricular septum, to optimize flow and reduce the chance of obstruction. With the apical site established, the HVAD sewing ring is secured over the left ventricular apex site. As the sewing ring is attached, it is important to be vigilant for arrhythmias or hemodynamic compromise. Arrhythmias or low blood pressure caused by surgical manipulation usually improve with cessation of compression, yet many patients may require the additional support of vasopressors, inotropes, or anti-arrhythmics during this period.

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Once the HVAD ring is secured, a form of reversible ventricular decompression is needed for the left ventricle coring and subsequent inflow cannula-pump implantation. The goal is to curtail blood loss, air entrainment, and enhance surgical visualization. The authors use temporary epicardial leads to artificially institute rapid ventricular pacing at 180 bpm. Prior to rapid ventricular pacing, the patient should be placed in Trendelenburg position to mitigate air entrainment. Heparin should be given prior to pacing to achieve an ACT of approximately 400 seconds in case the need for emergent CPB arises. Reduced doses of heparin, approximately 5000 U, have been described and considered for pump implantation, which may result in less blood loss 10. Once both the anesthesia and surgical team are both prepared, mechanical ventilation should be temporarily discontinued, and rapid ventricular pacing should commence. Given the hemodynamic compromise that comes with rapid ventricular pacing, this technique should be executed in a timely manner. Rapid ventricular pacing may need to be staged in runs in order to reduce prolonged end-organ hypoperfusion. Systemic hypotension should be treated with titrated boluses of vasopressors and inotropes after rapid ventricular pacing. Providers should be prepared for prompt cardiac defibrillation in the absence of the return of a stable, perfusing cardiac rhythm. Given the risk of profound bleeding, the anesthesia team should be prepared to rapidly resuscitate with fluids and blood products. If a perfusing cardiac rhythm is unobtainable or hemorrhage or hypotension is ongoing, CPB should be promptly initiated and HVAD implantation completed on CPB. Once the left ventricular cavity is cored and open, the surgeon should visually and manually inspect for excessive chordae tendinae and thrombus that may obstruct inflow. Using TEE, the inflow cannula should be positioned parallel to the interventricular septum and directed

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toward the mitral valve. The inflow cannula-pump is then secured in place by the HVAD ring. The left ventricular cavity should then be examined for air and allowed to passively de-air via the inflow cannula-pump outflow graft. The outflow graft is then clamped and tunneled under the sternum toward the hemisternotomy incision site. The act of tunneling the graft under the sternum may lead to significant hypotension secondary to decreased venous return and/or arrhythmias. Once the outflow graft is tunneled, it is anastomosed to the ascending aorta by means of a side-biting clamp and is de-aired with the assistance of a small-bore needle prior to initiation of HVAD flow.

At this point, TEE should be used to interrogate the aorta for any sign of hematoma or dissection. The aortic clamp is thereafter removed and the HVAD speed should be gently increased to the desired RPM. The mid-esophageal ascending aortic long-axis view is helpful for visualizing the HVAD outflow graft and assessing the amount of air extruding from the pump upon initiation of flow. Furthermore, the mid-esophageal four chamber view should be monitored to asses for proper left ventricular unloading and neutral septal position, confirmation of proper inflow cannula position, worsening valvulopathies, unmasked intracardiac shunts, and right heart dysfunction 19. If signs of right heart dysfunction appear, such as interventricular septum bowing toward the left ventricle, then measures to augment right heart function should be instituted. These may include adjusting the HVAD speed, starting inotropes (epinephrine or milrinone), and/or selective pulmonary vasodilators such as nitric oxide. If the right heart cannot accommodate the change in loading conditions, CPB may need to be instituted for a more staged process for starting HVAD support. Once the HVAD is determined to be functioning well with

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continuing hemodynamic stability, the incision sites can be closed with brief post-closure TEE evaluation to confirm proper cannula positioning. The patient can be then transported while intubated and sedated to the cardiothoracic intensive care unit. Once the patient demonstrates adequate hemostasis and a favorable hemodynamic profile, they may be considered for an expedited extubation process.

The off-pump minimally invasive approach for HVAD implantation offers many potential advantages including avoidance of full sternotomy, less right heart dysfunction, decreased blood product transfusion, earlier extubation, and possibly decreased overall morbidity and mortality. The avoidance of a full sternotomy may mitigate the risk of adhesion formation and its associated morbidity during future redo-sternotomies 20,21. This approach is highly advantageous in patients listed for cardiac transplantation, who will eventually require a median sternotomy. Furthermore, the reduced degree of mediastinal dissection and lack of CPB may lead to less postoperative bleeding and transfusion requirements. Reducing transfusion of packed red blood cells has many potential beneficial effects in patients listed for heart transplantation, including a decreased likelihood of allosensitization 22,23. The ability to avoid transfusion entirely would also allow consideration for HVAD implantation in patients whose religious preferences preclude the use of blood transfusion.

Postoperatively, the preservation of the rib cage anatomy could potentially allow for earlier tracheal extubation and reduce ventilator-related complications. A quicker transition from positive pressure ventilation to negative pressure ventilation would further

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unload the right ventricle and augment forward flow to the HVAD. Furthermore, miniature incisions preserve the integrity of the pericardium, except at the apex site, thereby theoretically diminishing the potential insult of pericardiotomy on right ventricle function. The right ventricle is also protected from the potential ischemic insult that may result from CPB, aortic cross-clamping, and inadequate myocardial protection. Additionally, an off-pump technique may reduce the detrimental physiologic effects of the CPB-induced systemic inflammatory response syndrome and vasoplegia. This inflammatory response is associated with the release of thromboxane A2, which is known to increase pulmonary vascular resistance, and may consequently impede right-sided cardiac output.

More research aimed at quantifying the clinical risks and benefits of this surgical technique is clearly warranted. However, initial attempts to perform HVAD implantation off-pump via minimally invasive incisions have anecdotally been quite successful at our Institution. There are many unique anesthetic considerations associated with this procedure and like other off-pump cardiac techniques, it demands a high level of vigilance and communication with our surgical colleagues.

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Expert Commentary

Komal D. Patel, M.D., David Geffen School of Medicine at UCLA, Los Angeles, CA

The gold standard for treatment of advanced heart failure is heart transplantation. However, due to limited availability of donor organs, mechanical circulatory support using a left ventricular assist device (LVAD) has become an effective strategy to bridge these patients to transplantation24. Advances in LVAD pump technology over the past decade have allowed constant improvements in outcomes and long-term durability after implantation25. Circulatory support using the centrifugal continuous flow HeartWare ventricular assist device (HVAD; HeartWare International, Inc., Framingham, MA) has become an established and effective strategy to bridge patients to heart transplantation26. HVADs have been implanted through sternotomy since 2007. However, the need for cardiac surgeries in this population, often requiring repeated sternotomies, leads to significant patient morbidity. The smaller pump design and intra-pericardial placement of the HVAD has allowed for the development of alternative and less invasive implantation techniques27-29. This case report describes one of such alternative technique, an off-pump placement of an HVAD via a mini-hemi sternotomy and mini-left anterior thoracotomy.

The surgical approach for HVAD placement has traditionally been a mid-line sternotomy using cardiopulmonary bypass (CPB). Although this approach has been successful, it may increase the risk of post-operative bleeding, infection30, renal dysfunction, and may also be associated with increased risk of complications from redo sternotomy.

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Furthermore, opening the pericardium in patients undergoing LVAD implant may be associated with increased risk of right ventricular (RV) dilation from alteration of the RV pressure-volume relationship31. Less invasive surgical approaches were developed to protect cardiac structures from multiple re-entries, to preserve heart geometry, and to reduce inflammatory response associated with CPB. Thoracotomy approach allows for exposure of the exact area of apex required for cannulation without the need for cardiac displacement, which is necessary from a midline sternotomy approach. Cardiac manipulation is often poorly tolerated in severe heart failure patients and may by itself lead to the necessity of the use of the CPB. Strueber et al recently described their clinical experience in implanting HVAD with minimally invasive off-pump thoracotomy approach14. They did not have any perioperative deaths or RV failure events. The mean intensive care unit stay was 1.5 days. Transfusion of 1 to 3 units of packed red blood cells were required in 16 patients, whereas 10 patients maintained a stable hematocrit of at least 30% and did not require transfusion. Survival through 90 days was 100%, and survival through 180 days was 87%.

Thorough multidisciplinary preoperative evaluation is paramount in selecting appropriate patients who can benefit from minimally invasive off-pump HVAD insertion. This approach requires mini-left anterior thoracotomy for exposure of left ventricular (LV) apex to insert the inflow cannula and upper hemi-sternotomy for exposure of ascending aorta to insert the outflow cannula. Although mini-left anterior thoracotomy is routinely used for other procedures like trans-apical aortic valve replacement, it could be challenging in patients with prior cardiac or thoracic surgeries, thoracic anomalies, or

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structural heart disease. Preoperative chest computed tomography (CT) can help identify anatomic risks associated with the left anterior thoracotomy and anatomic positioning of the ascending aorta. Direct access of the LV apex could be technically more challenging through small thoracotomy incisions and may result in improper placement of the inflow cannula. Use of intra-operative transthoracic echocardiography to locate the LV apex before performing the thoracotomy can assist the surgeon in identifying the ideal position for the incision. In patients with severe chronic obstructive lung disease, preoperative pulmonary function testing can be useful to evaluate their capacity for post-operative pulmonary recovery from a thoracotomy. Preoperative angiography is necessary to rule out ascending aortic pathology, like severe calcification, dissection, or aneurysm at the site of outflow graft anastomosis. All patients considered for thoracotomy approach should also undergo preoperative echocardiography to assess chamber size, presence of significant valvular abnormality, and RV size and function assessment32. Echocardiography provides critical information to determine the need for concomitant surgical procedures such as aortic or tricuspid valve repair or patent foramen ovale closure at the time of HVAD implantation. Patients with more than mild aortic regurgitation, previous mechanical valve replacement, more than moderate tricuspid regurgitation, and/or significant mitral stenosis are preferably approached through a standard on-pump sternotomy incision. Preoperative functional RV assessment is vital to determine a patient’s risk of developing postoperative RV failure. Presence of LV thrombus on preoperative echocardiography should warrant an on-pump HVAD approach to be able to clearly visualize the LV apex and remove the clot which otherwise could lead to pump thrombosis or systemic embolization. As these authors have

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described, intraoperative transesophageal echocardiography (TEE) is essential in guiding optimal position of the inflow cannula parallel to the inter-ventricular septum (IVS) and towards the mitral valve opening as the surgeon does not have direct visualization of the heart through a small thoracotomy incision. TEE is also needed to monitor for the RV function, adequate deairing of the LV, and to guide optimal LV decompression without displacement of IVS on initiation of HVAD.

Understanding details about how the minimally invasive HVAD insertion procedure is performed and complications associated with it is crucial in formulating an anesthetic plan. Anesthetic management should be tailored to the individual patient and to the Institutional preferences. General anesthesia is required due to complexity and duration of the procedure as well as the need for prolonged TEE monitoring. Lung isolation with a double lumen tube is not needed due to direct access of the LV apex with anterior thoracotomy. Poor underlying cardiac reserve requires judicious use of a balanced anesthetic technique with induction agents, benzodiazepines, opioids, volatile agents, and neuromuscular blocking agents. Preinduction arterial line guides titration of anesthetic agents to achieve hemodynamic stability during induction of anesthesia. Periods of cardiac decompression, either with rapid ventricular pacing (RVP) or adenosine necessitates careful monitoring of intra-arterial pressure. Intra-arterial pressure monitoring is also crucial during LV apex manipulation while placing the inflow cannula as these patients are prone to develop lethal arrhythmias. For the same reason, external defibrillator pads should be applied and connected to a functioning defibrillator. Central venous access should be obtained for potential use of inotropic agents or vasopressors as

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well as for blood product transfusion, if needed. Use of a pulmonary artery catheter should be dictated by individual patient’s comorbidities. A perfusionist and primed CPB machine should be on standby and access to the femoral vessels should be prepped and draped in the need of emergency conversion to on-pump procedure. Strueber et al reported conversion to on-pump surgery in 1 out of their 26 patients14. They used systemic anticoagulation with low dose heparin ACT of 200-250 seconds) for their offpump approach. This Commentator disagrees with the authors regarding the use of full dose of heparin and achieving an ACT of 578 seconds for their case. This would increase the risk of perioperative bleeding.

One of the critical parts during off-pump HVAD insertion is achieving ventricular decompression while coring the LV apex and inserting the inflow cannula to prevent blood loss and to prevent entrainment of air into the LV. The authors in this case report used RVP, which has been described in the past during off-pump insertion of the Jarvik LVAD33 and during trans apical aortic valve replacement procedures. RVP should be used for short periods of time to avoid end organ hypoperfusion. External defibrillation might be needed if the patient does not recover to a stable rhythm after RVP. Other techniques used for ventricular decompression include administration of intravenous boluses of adenosine34. Adenosine induces asystole and renders the LV immobile, making it less technically challenging for the surgeon to place the inflow cannula. It further reduces blood loss by reducing both the volume of blood ejected from the heart during HVAD implant and increasing time between heartbeats. An additional benefit of this method is adenosine-mediated pulmonary vasodilation, which may reduce pulmonary

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pressure and protect RV function35. Adenosine’s extremely short half-life minimizes the duration and potential deleterious hemodynamic effects of asystole induction. TEE plays an important role in diagnosing any air entrainment during inflow cannula insertion and ensures complete deairing of the device. If bleeding or hypotension continues following inflow cannula insertion, emergent conversion to CPB might be needed.

Although feasibility and safety of off-pump thoracotomy approach have been described in case reports and case series12,36, large outcome studies are lacking. A recent study by Sileshi et al compared outcomes of HVAD placement with off-pump thoracotomy approach (18 patients) to that of on-pump sternotomy approach (33 patients)34. They found a statistically significant reduction in days on inotropes and a trend toward reduced intra-operative blood product administration in off-pump thoracotomy approach. There was no difference in intensive care unit length of stay, total length of stay, post-operative blood product administration and total time on mechanical ventilation between the two groups. Limitations of this study include a small sample size and the fact that it was performed at one Institution by one surgeon, and therefore generalizability may be limited and affected by surgeon experience and Institutional practice. A large multicenter, randomized, controlled trial comparing minimally invasive off-pump thoracotomy approach to standard on-pump sternotomy approach is needed to compare the risks and benefits of these surgical techniques.

In summary, minimally invasive off-pump HVAD placement is a feasible emerging alternative to placement by midline sternotomy. This less invasive approach offers the

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potential of improving outcomes in high-risk surgical patients requiring repeated cardiac surgeries. The successful implantation requires robust collaboration between the surgeon and anesthesiologist. Proficiency in advanced TEE and familiarity with the procedure and complications associated with it are critical.

Expert Commentary

Mohammed Minhaj, M.D., M.B.A., University of Chicago, Chicago, IL

I would like to thank Dr. Bienia and his colleagues for presenting an interesting case of a patient receiving a HeartWare ventricular assist device (HVAD) (HeartWare International, Inc, Framingham, Mass) via a minimally invasive approach while avoiding cardiopulmonary bypass (CPB).

A recent study from the Nationwide Inpatient Sample demonstrated that there has been a marked increase in the implantation of left ventricular assist devices (LVAD) between 2005-2011.37 These authors also reported were a dramatic reduction in in-hospital mortality associated with the use of continuous flow devices beginning in 2008.37 While the costs associated with the care of these patients did increase over the 2005-11 time period, they have held steady since 2008, again coinciding with the introduction of continuous flow devices.37 The cost-effectiveness of LVAD therapy has been well studied, and while there is increased life expectancy when these are implanted for either bridge to transplant or destination therapy, there continues to be debate as to whether LVAD therapy offers economic value.38,39 Despite the debate over ‘value’, the HVAD 23   

has been shown to be more cost-effective than the previous generation continuous flow HeartMate II (HM II; Thoratec, Pleasanton, CA).40 Given the continued imbalance between patients in heart failure needing transplant and the availability of viable organs, it is likely that implantation of LVADs will only increase and anesthesiologists will need to maintain familiarity with device specifics and the critical role intraoperative management has in successful outcomes.

As the authors have described, the design of the HVAD provides the potential for implantation without creation of a pocket and also for a surgical approach without the use of CPB. The utility of TEE to affect surgical management has been well documented in previous studies.41,42 In the case the authors present, the consultant cardiac anesthesiologist played a vital role in guiding decision making through the use of intraoperative transesophageal echocardiography (TEE), reinforcing several papers published outlining the importance of TEE for VAD placement.43,44,19

In performing an intraoperative TEE for a patient receiving an LVAD, there are several anatomical and pathophysiological findings that need to be assessed. The pre-surgical exam needs to evaluate for intracardiac shunts (e.g. patent foramen ovale {PFO}), valvular pathology, thrombus, and assess right ventricular function (Table 1).

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Intracardiac Shunt

Most commonly PFOs, intracardiac shunts pose a significant risk to the patient after LVAD implantation. The newly implanted device may suction blood across the defect, creating a right-to-left shunt and significant hypoxemia. Because of high bi-atrial pressures often seen preoperatively, a PFO may be difficult to appreciate via color flow Doppler or a bubble study.43 Therefore, these can manifest with hypoxemia after initiation of LVAD therapy when the right-to-left shunt commences, and thus need to be ruled out in the immediate post-procedure TEE as well. In either situation, surgical correction is indicated.

Mitral Valve Assessment

Patients with left heart failure often present with some degree of functional mitral regurgitation (MR). When the MR is related primarily to left ventricular failure (as opposed to leaflet pathology), this can improve after initiation of LVAD therapy. More concerning in the pre-surgical period is the presence of mitral stenosis. Though rare in developed countries, significant mitral stenosis can impair LVAD filling and result in low cardiac output. Mitral stenosis at the time of LVAD insertion is an indication for surgical intervention. While evaluating the mitral valve, interrogation of the left atrial appendage for thrombus is also indicated, especially in the setting of mitral stenosis or ‘smoke’ in the left atrium, signifying low-flow hemodynamic states.

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Aortic Valve/Aorta Assessment

Aortic stenosis is not critical in patients receiving a HeartMate device because flow through the native valve is not necessary for cardiac output. However, aortic insufficiency (AI) is potentially serious after initiation of LVAD support. This is because AI results in a ‘closed-loop’ where blood is ejected through the LVAD outflow cannula, some of which traverses the incompetent aortic valve, then enters the LVAD again but never reaches the systemic circulation. AI can be difficult to assess in the preoperative period given increased left ventricular end diastolic pressure and reduced aortic diastolic pressure resulting in reduced transvalvular gradients. Pressure half-time of the regurgitant jet in the deep transgastric view may be used to assess the degree of AI. Moderate to severe AI needs to be surgically corrected at the time of LVAD placement. Options include surgical closure, repair, or replacement with a bioprosthetic valve. A recent paper suggested that mortality was higher in patients who underwent valve closure versus repair/replacement, though a cause for this was not identified.45 A bioprosthetic valve is preferred to reduce the risk of thrombosis.19

Many patients with long-term LVAD support may develop either aortic stenosis or aortic insufficiency. Considering the long-term consequences of AI in destination therapy VADs, identification of risk factors for the development of AI at the time of VAD placement is prudent.46,47

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Complete evaluation of the ascending aorta is also important for the procedure. Potential LVAD outflow cannula sites need to be assessed for potential atheromas or plaques as well as dilation in the setting of aortic aneurysm. Epiaortic assessment may be necessary if adequate visualization of the ascending aorta by conventional TEE is not possible or suboptimal.

Tricuspid Valve/Right Ventricle Assessment

In patients with biventricular failure or even isolated left ventricular failure, functional tricuspid regurgitation (TR) is common. There is debate about the best intervention for TR in these cases. Our surgeons are relatively aggressive in pursuing suture annuloplasty of the tricuspid valve making the argument that this promotes adequate filling of the left heart, the LVAD, and ultimately maintains adequate systemic cardiac output. Others argue that functional TR may improve as the LVAD begins to offload the left ventricle (LV) and thus improve right ventricle (RV) performance.43 Identifying the degree of TR as well as the etiology of the TR can help guide decision-making, as leaflet pathology is more likely to require surgical intervention while functional TR might improve with LVAD therapy. 43

A complete evaluation of the RV function is imperative as well. RV function is often reduced in these patients. Often times, this can improve with LVAD therapy and offloading of the LV, but LVAD therapy can also worsen RV performance by increasing preload to an RV that has significantly reduced function. There exist several methods of

27   

evaluating RV function; the fractional area change is commonly used to predict the need for RVAD support in patients receiving an LVAD.43 A fractional area change of less than 20% and/or a dilated RV with increased RV preload/afterload are two predictors for RV failure requiring RVAD support. Even in cases with moderately reduced RV function, decisions regarding the necessity of or benefit from pharmacological interventions (e.g. inotropes and/or pulmonary vasodilators) can be made based upon TEE evaluation.

Left Ventricle Assessment

Evaluation of the left ventricle includes evaluating for regional wall abnormalities as well as identifying potential aneurysms/pseudoaneurysms and thrombi in the LV. Thrombus in the LV (or left atrial appendage) could compromise LVAD function in addition to being a risk for stroke or other ischemic end-organ injury.

As can be appreciated in reviewing these potential pre-existing states, all of them would necessitate a different surgical plan requiring the use of CPB. Thus, a thorough presurgical TEE by an experienced echocardiographer is imperative for this procedure’s success. Likewise, in the immediate post-surgical period, TEE is invaluable in assessing LVAD function and following up on the aforementioned abnormalities (if present). A comprehensive TEE is required to assess LVAD and RV function, assess valvular function (especially if there was a surgical intervention), and assess in de-airing of the LV. Table 2 outlines key portions of the post-surgical, intra-operative TEE.

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LVAD Assessment

The most obvious TEE assessment is that of the LVAD inflow/outflow cannulae. The inflow cannula is best visualized in mid-esophageal two and four chamber views, but can also be seen in the mid-esophageal long axis view. The cannula needs to be directed towards the mitral valve and not be in contact with any walls of the LV. Doppler assessment of the inflow cannula needs to be performed. With the HeartWare LVAD, flow should be phasic and slightly pulsatile with low-velocity profiles. The peak velocity should be < 2.0 m/s.19 Improperly aligned inflow cannulas can result in cannula obstruction, as can thrombus or hypovolemia.

The outflow cannula is best visualized in the mid-esophageal long-axis view of the ascending aorta. On Doppler examination, a low-velocity flow is appreciated. Velocities can be greatly affected by the insertion angle of the outflow cannula into the aorta.44,19 Acceleration of Doppler velocities in the proximal graft versus those measured more distally suggest graft distortion. Thrombus can also result in outflow cannula obstruction.19

The LV is often decompressed after LVAD initiation but marked hypovolemia needs to be avoided as it can result in inflow cannula obstruction. The septum should remain in a neutral position. A septum deviated to the right suggests inadequate reduction of LV pressures which may benefit from increasing LVAD flows (if they are not already maximized) or more seriously may suggest cannula obstruction.19 A septum deviated to

29   

the left may suggest hypovolemia, RV dysfunction, or excessive LV unloading. In addition to volume assessment and septum position, TEE is also an important adjunct in evaluating for air in the LV and can be useful in guiding de-airing techniques.44

Aortic Valve/Aorta Assessment

The aortic valve needs to be evaluated for either new onset AI that can occur with higher velocities in the ascending aorta from the outflow cannula or to assess the quality of a repair/replacement (if performed). Trace-mild AI may not necessitate surgical intervention but moderate-severe AI will.44 Risk factors for the development of long-term AI can also be identified and factored in to the decision for further surgical intervention.46 Decisions regarding further surgical intervention are also often based on whether the device is being placed as a bridge to transplant, short-term support, or destination therapy. If destination therapy is the indication, then surgical correction is more warranted. The aortic valve may or may not open depending on the degree of native LV ejection, LVAD flows, etc. In patients with HeartWare devices, closed aortic valves have been associated with blood stasis and thrombosis. LVAD flows should be adjusted to allow intermittent aortic valve opening.19 Aortic dissection is also a potential complication with outflow cannula placement and the ascending aorta needs to be carefully evaluated to rule this out.19

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Right Ventricular Function

As discussed above, the RV is susceptible to further declines in performance after initiation of LVAD support, especially if there was severely reduced RV function preoperatively. In these cases, decisions to pursue further pharmacological intervention (inotropes, pulmonary vasodilators), gauge the effects of these agents, or recommend additional surgical intervention (right ventricular mechanical support) can be supported with TEE evaluation,coupled with direct visualization of the RV in the field. In minimally invasive approaches, RV visualization may not be as complete as it is in median sternotomy, making TEE evaluation even more important for evaluation of RV performance. If TR was present in the pre-surgical TEE assessment of the severity of the TR post-procedure (particularly if annuloplasty/replacement was performed) should be documented.

The interatrial septum should also be re-evaluated, as a PFO that was undetectable previously may manifest after initiation of LVAD support and changing cardiac chamber pressures. Any additional surgical procedures undertaken at the time of LVAD placement (e.g. mitral repair) need to have a follow-up TEE evaluation in the operating room to assess the quality of the repair.

Long-term, patients with LVADs often return to the operating room for related or unrelated reasons. Tamponade has been described as a relatively common occurrence in these patients and bedside TEE can be useful in evaluating for this diagnosis. As

31   

described above, many patients may develop aortic valve abnormalities (insufficiency or stenosis) over time and subsequent TEE’s need to always evaluate for these conditions. More seriously, in the setting of pump arrest, TEE can quickly identify retrograde flow in an LVAD or exclude hypovolemia, acute RV failure, and guide appropriate therapeutic decision making whether it is additional mechanical support, device replacement, or addressing the underlying etiology (e.g. hypovolemia).44

Overall, Dr. Biena and his colleagues have presented an interesting case that allowed their patient to receive LVAD support while preserving a ‘virgin’ sternum to facilitate eventual heart transplantation. Their case highlights the advantages that the next generation mechanical circulatory assist devices can provide (e.g. size) that permits less invasive surgical approaches and avoidance of CPB. In these cases, it is vital for anesthesiologists to perform comprehensive TEE examinations to ensure that additional surgical interventions requiring a different approach are not required, evaluate for potential complications associated with LVAD placement, evaluate for additional RV support (if necessary), and ensure proper anatomical positioning and function of the LVAD.

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Figure Legends

Figure 1. Transesophageal echocardiography showing a mid-esophageal four chamber view. A spinal needle is visualized in good position within the left ventricle.

Figure 2. The HeartWare sewing ring is attached to left ventricular apex via left anterior thoracotomy incision.

Figure 3. Anterior left thoracotomy incision with sewing ring attached and upper hemi-sternotomy with tunneled outflow graft.

Figure 4. HVAD device has been attached to sewing ring in the left ventricular apex.

Figure 5. Anterior lateral thoracotomy and mini-sternotomy incisions after skin closure.

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Imran Hamid U, Digney R, Soo L, et al: Incidence and outcome of re-entry injury in redo cardiac surgery: benefits of preoperative planning. Eur J Cardiothorac Surg 47:819-823, 2015

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Shah N, Agarwal V, Patel N, et al: National trends in utilization, mortality, complications and cost of care after left ventricular device implantation from 2005 to 2011. Ann Thorac Surg Published November 14th, 2015

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Neyt M, Van den Bruel A, Smit Y, et al: The cost-utility of left ventricular assist devices for end-stage heart failure patients ineligible for cardiac transplantation: a systematic review and critical appraisal of economic evaluations. Ann Cardiothorac Surg 3:439-449, 2014

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42.

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43.

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Robertson JO, Naftel DC, Myers SL, et al: Concomitant aortic valve procedures in patients undergoing implantation of continuous-flow left ventricular assist devices: An INTERMACS database analysis. J Heart Lung Transplant 34:797805, 2015

46.

Deo SV, Sharma V, Cho YH, et al: De novo aortic insufficiency during long-term support on a left ventricular assist device: a systematic review and meta-analysis. ASAIO J 60:183-188, 2014

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Table 1: Pre-surgical findings that may necessitate additional surgical intervention at time of LVAD implantation. Intracardiac Shunts Mitral valve stenosis Aortic stenosis/insufficiency Aortic aneurysm/atheromas Tricuspid Regurgitation Severe Right Ventricular Failure Left Ventricle Thrombi Left Ventricle Aneurysm/Pseudoaneurysm

 

40   

Table 2: Key Components of the Post-Surgical TEE. LVAD Assessment (Inflow/Outflow Cannula Position/Velocities) Left Ventricle Volume/Septum Position/Air Aortic Insufficiency Aortic Dissection Right Ventricle Function

Figure 1 

 

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Figure 2

42   

Figure 3

   

Figure 4

 

43   

Figure 5

 

44