End-stage heart failure

Heart failure (HF) is defined as insufficient cardiac output to meet the metabolic requirements of the tissues at normal cardiac-filling pressures. Cardiogenic shock is defined as sustained hypotension and tissue hypoperfusion. HF can be systolic (impaired contractility with impaired ejection fraction) or diastolic (decreased relaxation and compliance). Activation of the compensatory neurohormone system (renin-angiotensin-aldosterone system and release of natriuretic peptides, angiotensin II, norepinephrine, and endothelin) results in fluid retention, peripheral vasoconstriction, downregulation of β-adrenergic receptors, and ventricular remodeling. Eventually, left ventricular (LV) failure leads to pulmonary hypertension and right ventricular (RV) failure.

Echocardiography is used to assess ventricular function, to identify structural and functional cardiac abnormalities, and to guide therapy. The American Heart Association classification defines four stages of HF: A through D. Stage D is end-stage HF, (Figure 143-1). Coronary artery disease is the most common cause of both systolic and diastolic failure. Other causes include dilated nonischemic, restrictive, hypertrophic, and stress-induced cardiomyopathy. The most common cause of death is ventricular arrhythmia.

Patients with coronary artery disease or valvular heart disease should have medical therapy optimized and, depending on the anatomy, revascularization performed or valves repaired or replaced as appropriate. In patients with an ejection fraction of less than 30%, placement of an implantable cardioverter defibrillator (ICD), pacemaker resynchronization therapy, or both is recommended. Routine anticoagulation is not recommended. Surgical treatment options include placement of an intra-aortic balloon pump, ventricular assist device (VAD), or total artificial heart (TAH) or orthotopic heart transplantation.

Clinical indications for the use of a mechanical device before multisystem organ failure occurs include myocardial infarction, failed percutaneous coronary intervention, acute viral myocarditis, peripartum cardiomyopathy, cardiac contusion, postcardiotomy shock, chronic cardiomyopathy with acute decompensation, and intractable ventricular arrhythmias. Early intervention improves survival.

Ventricular assist devices

VADs to support the left, right, or both ventricles are either pulsatile or nonpulsatile pumps, located paracorporeally or intracorporeally, and are used as a bridge to recovery (short-term), a-bridge to transplantation, or destination therapy. The first-generation VADs use pulsatile pumps with valves that displace a given volume of blood with every beat. One pulsatile pump is still marketed in the United States, a paracorporeal VAD (pVAD; Thoratec, Pleasanton, CA) for short-term to intermediate-term use in patients who require bridge to transplantation or bridge to recovery (Figure 143-2). Approximately 10% of patients recover sufficient function to be weaned completely from mechanical support. Compared with previous devices, the pVAD allows for greater patient mobility (a portable device is available for patients who leave the hospital) and longer-term use (weeks to months and, in a few cases, years); its use is associated with lower rates of morbidity. Short-term anticoagulation is provided with heparin, whereas long-term anticoagulation requires warfarin and sometimes aspirin.

Second-generation VADs are smaller, intracorporeal, nonpulsatile, axial-flow pumps without valves. Third-generation VADs are bearingless and use a combination of magnetically and hydrodynamically suspended impellers. Currently available in the United States are the Heartmate II (Thoratec), a second-generation device approved by the U.S. Food and Drug Administration (FDA) for bridge to transplantation in 2008 and for destination therapy for patients who are not candidates for heart transplantation in 2010 (Figure 143-3), and the HeartWare ventricular assist system (Framingham, MA), a third-generation device approved in 2012 by the FDA as a bridge to transplantation (Figure 143-4).

Left VADs (LVADs) drain blood from the LV through an inflow cannula to the pump and return blood via an outflow cannula into the proximal aorta. The Randomized Evaluation of Mechanical Assistance for the Treatment of Congestive Heart Failure (REMATCH) trial demonstrated that patients did better when they had a device implanted sooner rather than later (before they developed organ dysfunction, i.e., kidney failure). Long-term survival is approximately 80% at 1 year and more than 50% at 2 years after device implantation.

Total artificial heart

SynCardia (Tucson, AZ) produces two TAHs, each consisting of two independent pulsatile devices (ventricles) that, once the native ventricles are excised, are anastomosed to the native atria with the outflow cannulas inserted into the ascending aorta and pulmonary outflow tract, respectively. The FDA approved the 75-mL TAH (Figure 143-5) as a bridge to transplant in 2004 and designated two humanitarian use device labels for the 50-mL TAH in 2013—destination therapy and pediatric bridge to transplant.

The preparation of these patients is similar to that required for other patients having cardiac surgical procedures involving cardiopulmonary bypass (CPB). However, patients who are receiving VADs, a TAH, or heart transplants are at greater risk for experiencing hemorrhage and are at risk for developing systolic dysfunction, ventricular arrhythmias, and sudden death prior to CPB.

A thorough preoperative evaluation should include an extensive review of the patient’s cardiac, pulmonary, renal, and metabolic history; a comprehensive examination of the patient; and a complete assessment of all laboratory results and imaging studies. All previously implanted devices such as pacemakers and ICDs should be interrogated. Packed red blood cells (cytomegalovirus free), fresh frozen plasma, and platelets must be available in the blood bank because these patients will have received anticoagulant therapy, have chronic anemia, and are at high risk of developing perioperative bleeding.

Considerations for patients for heart transplantation

Patients with end-stage heart disease are carefully screened for possible heart transplantation. They must be adherent with treatment, not abuse substances (including alcohol), have an adequate support system, be free of cancer, and have a body mass index of less than 38. Severe irreversible pulmonary hypertension is an absolute contraindication to heart transplantation (pulmonary vascular resistance > 6 Wood units or > 480 Dynes·sec⁻¹·cm⁻⁵).

When the United Network for Organ Sharing is notified that a patient has been declared brain dead and the organs are available for transplantation, they identify potential recipients by matching the donor heart with potential recipients, based on the severity of the recipient’s disease, through HLA typing, ABO blood group compatibility, and body size. Once the best candidate is found, the transplant center is notified, and, if the transplant team and patient agree, the candidate is posted for transplantation.

These cases are always performed on an emergency basis. Donor-heart ischemic time should optimally be kept at less than 4 hours. Sterile technique is imperative because the patient will be immunosuppressed and at high risk of developing infection. Immunosuppression protocols vary. Commonly, 500 mg of methylprednisolone is administered after induction and again after release of the aortic cross-clamp. Other immunosuppressant drugs may be utilized depending on the preferences of the institution’s transplant service.

The surgical technique involves four major anastomoses: left and right atria and the end-to-end aortic and pulmonary anastomoses. The bicaval technique is used in some cases instead of the right atria anastomosis. Because the donor heart is denervated, only direct-acting β-adrenergic agents will increase heart rate.

RV failure is the most common cause for failure to wean from CPB after heart transplantation. Preventing hypoxia and hypercarbia are essential, and the use of pulmonary vasodilators (prostaglandin E1, nitric oxide, milrinone) and inotropes (epinephrine, dobutamine, milrinone) to support the RV may be necessary. Norepinephrine and vasopressin may be needed to support systemic vascular resistance. In the early postoperative period, patients are at risk for developing hyperacute and acute rejection, pulmonary and systemic hypertension, cardiac arrhythmias, respiratory failure, renal failure, and infection.

Allograft coronary artery disease is the major limiting factor to long-term survival following heart transplantation. This is diffuse disease that involves the vessels circumferentially. Cyclosporine and corticosteroids are the mainstays of long-term immunosuppression and may cause nephrotoxicity, hypertension, and malignant neoplastic disease. The survival rates for transplantation approach 90% for the first year and 75% at the seventh year.