Ventricular Assist Device Implantation

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W8 Ventricular Assist Device Implantation

Robert L. Kormos

image Before Procedure

Indications

• Postcardiotomy failure (left ventricular assist device [LVAD]):

• Elevated left atrial pressure and cardiogenic shock despite inotropic support and intraaortic balloon pump (IABP)

image Left arterial pressure (LAP) >25
image Cardiac index <2 L/min/m2
image Severe left ventricular (LV) dysfunction on echocardiogram
image Intractable ventricular arrhythmias
image Ongoing myocardial ischemia despite revascularization

• Postcardiotomy failure (bilateral ventricular assist device [BiVAD]):

• Evidence of elevated central venous pressure (CVP: 9 > 18 mm Hg) despite pulmonary afterload reduction
• Evidence of severe right ventricular (RV) dysfunction on echocardiogram
• Inability to provide adequate blood flow of filling of LVAD if in place

• Bridge to cardiac transplantation:

• Failure of optimal medical therapy that raises risk of compromised life or end-organ function while awaiting cardiac transplantation:

image Cardiac index <2 L/min/m2
image Mixed venous oxygen saturation <50% on optimal medical therapy
image Ventricular arrhythmias
image Severe symptoms at rest
image Need for multiple inotropic agents
image Non-responsiveness to diuretics, with rising creatinine
image Pulmonary artery hypertension
image Cool and constricted extremities reflective of poor perfusion
image Low blood pressure, resting tachycardia, rales, and/or distended neck veins
image Laboratory evidence of prerenal azotemia or hepatic dysfunction or prolonged coagulation levels
image Requirement for supplemental oxygen

• Bridge to bridge: in conditions of cardiogenic shock where indications for cardiac transplantation are not yet met but are potentially attainable
• LVAD versus BiVAD:

image Biventricular assist devices should be considered for:

• Intractable ventricular tachycardia or fibrillation
• Cardiogenic shock requiring resuscitation with extracorporeal membrane oxygenation (ECMO)
• Cardiogenic shock with presence of multiorgan failure
• Pulmonary edema despite maximal medical therapy
• Chronic RV failure with presentation of ascites, low pulmonary artery pressure, severe hepatic or renal dysfunction, and tricuspid insufficiency
• Severe acute respiratory distress syndrome
• Giant cell myocarditis
• Large anterolateral myocardial infarction with involvement of anterior right ventricle
• RV infarction

• Destination therapy:

image Indicated for those patients who meet above criteria for bridge to transplant LVAD candidacy but are not eligible for transplantation based upon: age, obesity, renal dysfunction that will not tolerate immunosuppressive agents, other added comorbidities that suggest that transplantation risk is unacceptable
image Patients with advanced heart failure (HF) symptoms (class IIIB or IV) who are (must meet one criterion):

• On optimal medical management (OMM) for at least 45 out of 60 days and are failing; or
• In class III or IV for at least 14 days and dependent on IABP for 7 days and/or inotropes for 14 days; or
• Treated with angiotensin-converting enzyme (ACE) inhibitors or beta-blockers for at least 30 days and found to be intolerant
• VO2 max ≤14 mL/kg/min or ≤50% predicted VO2 max with AT, if not contraindicated due to IV

Contraindications

• Postcardiotomy failure:

• Sepsis
• “Stone heart” or lack of any innate cardiac function
• Age >70
• Condition where recovery is not anticipated and patient is not a candidate for cardiac transplantation

• Bridge to transplantation:

• Patient not a candidate for cardiac transplantation
• Sepsis
• End-organ damage not likely to recover
• Severe impairment of neurologic function
• Severe chronic obstructive pulmonary disease (COPD)
• Procoagulation abnormalities with history of venous or arterial thrombosis despite anticoagulation
• Pregnancy
• Inability or refusal to use blood transfusions
• Technical obstacles that pose an inordinately high surgical risk

• Destination therapy:

• Same as for transplantation, other than requirement for cardiac transplantation candidacy
• Lack of social or family support that allows for home discharge
• Inability to comprehend plan for postoperative LVAD training
• Expected need for prolonged biventricular support
• Severe symptomatic peripheral vascular disease
• Intolerance to anticoagulant or antiplatelet therapies or any other peri-/postoperative therapy the investigator will require based upon patient’s health status
• Psychiatric disease, irreversible cognitive dysfunction, or psychosocial issues likely to impair compliance with protocols and LVAD management.

Equipment

• Postcardiotomy:

• IABP
• ABIOMED AB/BVS 5000 (LVAD and BiVAD)
• Tandem Heart
• Thoratec CentriMag (LVAD and BiVAD)
• Thoratec PVAD (LVAD and BiVAD)

• Bridge to transplant:

• Thoratec PVAD (LVAD and BiVAD)
• Heartmate II
• Heartware HVAD
• DuraHeart
• Levacor
• CardioWest Total Artificial Heart

• Destination therapy:

• Heartmate II
• Heartware HVAD

image Procedure

• Intraoperative preparation and evaluation:

• Lines: arterial, venous, Swan-Ganz (continuous cardiac output type for continuous-flow LVADs)
• Preoperative echo assessment:

image For LV for thrombus
image Interatrial septal defect or patent foramen ovale (PFO)
image Aortic insufficiency
image Tricuspid insufficiency
image Right ventricular function

• Hemodynamic control:

image Management and preservation of perfusion pressure for right ventricle and coronary perfusion utilizing α-agonists
image Preoperative thromboelastogram to assess coagulopathy and need for transfusion products
image Cautious volume management

• Cannulation for cardiopulmonary bypass:

image Distal ascending aortic site for inflow
image Standard two-stage venous cannula for drainage for standard LVAD
image Biatrial cannulation for BiVAD or if tricuspid repair or PFO closure required

• Apical LV cannulation achieved for LVAD:

image Apical cannulation achieved according to protocol dictated by each individual VAD brand
image Preperitoneal pocket required for some LVADs; otherwise subcostal tunnel made as needed

• Aortic outflow graft sewn end-to-side for outflow
• RVAD cannulation via right atrial appendage
• RVAD return to pulmonary artery via arterial cannula

• Closure of pericardium preferred
• Adequate chest tube drainage from mediastinum and pleural spaces

image After Procedure

Postprocedure Care

• Hemodynamic and volume control:

• Blood pressure maintenance is critical for RV function.
• Adequate inotropic support is needed for RV.
• Appropriate blood product replacement should be given, guided by thromboelastogram.
• Adequate blood pump flow is determined by adequate cardiac index of at least 2.4 L/min/m2.
• In most cases, decompression of the LV should not be so great as to cause right-to-left interventricular septal shift. Mitral regurgitation should be reduced and aortic valve open occasionally.
• CVP should be maintained between 8 and 12 mm Hg.

• Intensive care unit care:

• Maintain positive pressure ventilation until mental status and pulmonary function allow for extubation.
• Remove chest tubes as soon as possible.
• Begin anticoagulation for the VAD with heparin after 24 hours when bleeding is less than 50 mL/h, and convert to warfarin when taking oral fluids.
• Broad-spectrum antibiotics should be continued for 4 to 5 days.
• Active physiotherapy should be carried out, with emphasis on pulmonary toilet and incentive spirometry.

Complications

• Common:

• Bleeding: mediastinal, wounds, drivelines, gastrointestinal
• RV dysfunction
• Infection: drivelines and exit sites, pulmonary and urinary tract

• Infrequent:

• Neurological events
• Arrhythmias
• Hemolysis
• Psychiatric

• Serious rare complications:

• Device malfunction

image Outcomes and Evidence

Successful clinical evaluation of the Thoratec pVAD led to U.S. Food and Drug Administration (FDA) approval for bridge to transplantation (BTT) indication in 1992. Twenty-four patients (62%) required support with an LVAD alone, and 15 (38%) required BiVAD support. Support to successful outcomes was 70% for BTT and 67% for postcardiotomy recovery.

The HeartMate II (Thoratec Corporation, Pleasanton, California) is a CF rotary pump with axial design that is representative of the second generation of LVAD technology in clinical use in the United States. Successful clinical evaluation of the Thoratec pVAD led to FDA approval for BTT indication in 1992. Of the 133 patients receiving support with the HeartMate II device, the principal outcomes were observed in 100 patients (75%). Median duration of support was 126 days (range 1-600). Survival rate during support was 75% at 6 months and 68% at 12 months. There was significant improvement in distance walked between baseline and 6 months, with over 50% of patients experiencing an improvement in 6-minute walk distance of over 200 meters.

In 1998, the National Heart, Lung and Blood Institute funded the Randomized Evaluation of Mechanical Assistance for the Treatment of Congestive Heart Failure (REMATCH) trial. REMATCH was a pivotal trial designed to assess morbidity, mortality, and functional outcomes in a homogenous cohort of patients with advanced heart failure ineligible for cardiac transplantation. Survival at 1 (52% versus 25%, P = 0.002) and 2 years (23% versus 8%, P = 0.09) was superior (significantly) in the VAD patients compared to those randomized to medical therapy.

Following the original REMATCH publication, Park and colleagues analyzed the outcomes of the trial, based upon the era of enrollment. Despite more high-risk characteristics, patients enrolled in the latter half of the study had a significantly higher 1- and 2-year survival rate than those enrolled early in the experience. A similar improvement in survival outcomes was seen in the postapproval registry, with a 56% 1-year survival rate. Improved outcome with VAD use and experience is a consistent observation, also evident in the CAP cohort versus Primary cohort in the HM IIBTT trial. Demonstration of improved survival outcomes in patients with preimplant risk profiles similar to or worse than those enrolled in the initial randomized trial suggests that refinement of pre- and postoperative management, as well as greater experience with MCS, are important factors in determining survival and functional improvements after VAD implantation.

The HeartMate II DT Pivotal Trial randomized 200 patients with New York Heart Association class IIIb-IV symptoms, ejection fraction (EF) <25%, and a maximal oxygen consumption ≤14 mL/kg/min or treatment with intravenous inotropic agents for at least 14 days or an IABP for 7 days to receive a HeartMate II (n = 134) or a HeartMate XVE (n = 66). There was a greater than fourfold increase in the percentage of HeartMate II patients who successfully reached the primary endpoint (46% versus 11%, P < 0.001). Patients randomized to the HeartMate II had 1- and 2-year survival rates of 68% and 58%, compared with 55% and 24% for the patients who received the HeartMate XVE.

Suggested Reading

Rose EA, Gelijns AC, Moskowitz AJ, et al. Randomized Evaluation of Mechanical Assistance for the Treatment of Congestive Heart Failure (REMATCH) Study Group. Long-term mechanical left ventricular assistance for end-stage heart failure. N Engl J Med. 2001;345:1435-1443.

Slaughter MS, Rogers JG, Milano CA, et al. HeartMate II Investigators. Advanced heart failure treated with continuous-flow left ventricular assist device. N Engl J Med. 2009;361:2241-2251.

Farrar DJ, Hill JD, Gray LAJr, et al. Heterotopic prosthetic ventricles as a bridge to cardiac transplantation. A multicenter study in 29 patients. N Engl J Med. 1988;318:333-340.

Slaughter MS, Tsui SS, El-Banayosy A, et al. Results of a multicenter clinical trial with the Thoratec implantable ventricular assist device. J Thorac Cardiovasc Surg. 2007;133:1573-1580. [Erratum appears in J Thorac Cardiovasc Surg. 2007 Sep;134(3):A34]

Frazier OH, Rose EA, McCarthy P, et al. Improved mortality and rehabilitation of transplant candidates treated with a long-term implantable left ventricular assist system. Ann Surg. 1995;222:327-336.

Miller LW, Pagani FD, Russell SD, et al. Use of a continuous-flow device in patients awaiting heart transplantation. N Engl J Med. 2007;357:885-896.

Pagani FD, Miller LW, Russell SD, et al. Extended mechanical circulatory support with a continuous-flow rotary left ventricular assist device. HeartMate II Investigators. J Am Coll Cardiol. 2009;54:312-321.

Long JW, Healy AH, Rasmusson BY, et al. Improving outcomes with long-term “destination” therapy using left ventricular assist devices. J Thorac Cardiovasc Surg. 2008;135:1353-1360.

Lietz K, Long JW, Kfoury AG, et al. Outcomes of left ventricular assist device implantation as destination therapy in the post-REMATCH era: implications for patient selection. Circulation. 2007;116:497-505.

Kirklin JK, Naftel DC, Kormos RL, et al. Second INTERMACS annual report: More than 1,000 primary left ventricular assist device implants. J Heart Lung Transplant. 2010;29:1-10.

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