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).