Advanced heart failure is characterized by the clinical signs and symptoms of congestion, low cardiac output, and progressive organ dysfunction with an annualized mortality rate of 80% to 90% despite optimal medical and electrical therapies.1 Cardiac transplantation remains the gold standard treatment for stage D heart failure, but the worldwide donor shortage has resulted in highly selective criteria and long waiting times for a suitable organ. The option of mechanically assisted circulation as a viable treatment alternative for this population has gained gradual acceptance over the past decade. The original mechanical blood pumps were designed to replicate the human heart, resulting in large, pulsatile devices with a normal adult stroke volume. The conceptual model of assisted circulation has evolved to smaller, less complex continuous flow pumps. The Interagency Registry for Mechanically Assisted Circulation (INTERMACS) has documented the growth of the field with detailed clinical information on > 15,000 individual patients treated with mechanical circulatory support (MCS) in the United States.2
INDICATIONS FOR MECHANICAL CIRCULATORY SUPPORT
Patients considered for treatment with MCS have severely depressed left ventricular (LV) systolic function, New York Heart Association (NYHA) functional class III or IV limitations, systemic hypotension, frequent heart failure hospitalizations, and intolerance to standard heart failure therapy secondary to hypotension or worsening renal function. Objective evidence of functional limitations includes a peak oxygen consumption of ≤ 14 mL/kg/min or a 6-minute walk distance < 300 m. Hemodynamic assessment typically demonstrates elevated left-sided cardiac filling pressures and a cardiac index < 2 L/min/m2.
Standard contraindications to MCS therapy include ongoing systemic infection, irreversible end-organ dysfunction, severe untreated carotid artery disease, recent stroke, inability to take anticoagulation or antiplatelet therapy, a mechanical aortic valve without plans for replacement or exclusion from the circulation, and a life expectancy related to another disease process of < 2 years. Medical noncompliance, ongoing substance abuse, and inadequate social support are also important predictors of adverse outcomes and typically exclude patients from this complex therapy. Advanced age, medical frailty, and malnutrition are considered to be relative contraindications.
The growing number of devices and population heterogeneity necessitate matching patient characteristics with device capability and anticipated support duration. Assisted circulation descriptors are LV assist device (LVAD), right ventricular (RV) assist device, biventricular assist device, and total artificial heart (TAH). The most common ventricular assist device (VAD) implant indications are bridge to transplantation (BTT) in patients listed for transplantation at high priority who are failing optimal medical therapies or as permanent cardiac replacement in patients ineligible for transplant (destination therapy [DT]). The latter group have NYHA class IIIb or IV functional limitations on maximally tolerated medical therapy, an LV ejection fraction < 25%, and a peak oxygen consumption of < 14 mL/kg/min. In less stable patients, treatment with continuous infusion of inotropic medications for at least 14 days or need for acute circulatory support for at least 7 days are also indications for durable LVAD therapy.
Short-Term Mechanical Circulatory Support
Short-term MCS is indicated in instances of acute heart failure or cardiogenic shock when the degree of reversibility is unclear or suitability for durable MCS cannot be completely determined at the time of implantation.3 Most acute circulatory support strategies are used for days to weeks, so attempts to wean the device and/or transition to durable circulatory support should begin at the time of short-term device placement.
Indications for Acute Circulatory Support
The most common indication for short-term MCS ...