Left Ventricular Assist Device Insertion

Over the past several years, there has been a dramatic shift from the use of large pulsatile left ventricular assist devices (LVADs) to the use of smaller continuous-flow devices for the provision of mechanical circulatory support in patients with heart failure. ^[1] However, the fundamental issues related to surgical implantation remain the same. That is, most devices use the apex of the left ventricle (LV) as the inflow site to the pump, which subsequently gives off an outflow graft to the aorta, thus bypassing the ailing LV.

This article describes some of the issues related to implantation of LVADs. Although many types of devices are currently available, they do not differ significantly with regard to general implantation technique. Accordingly, this article focuses on the device currently dominant in the United States, the Thoratec HeartMate II. Other devices approved by the US Food and Drug Administration (FDA) include the Jarvik 2000 (Jarvik Heart, New York, NY) and the HeartWare Ventricular Assist System ^[2] (HeartWare, Framingham, MA).

Mechanical circulatory support can be used to salvage the cardiogenic shock patient and as a bridge to transplant therapy (BTT); it can also be permanent or be used for destination therapy (DT). In addition, patients who have durable LVADs implanted to determine their eligibility for transplant fall into a gray zone.

The Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) follows all FDA-approved durable pump implants and has created a system for defining patient profiles. The algorithm for the patient with acute cardiogenic shock often involves insertion of nondurable pumps (INTERMACS Profile #1). This article remains focused on BTT, DT, and eligibility for transplant.

Most patients with LVADs are in progressive decline (INTERMACS Profile #2; inotrope-dependent with continuing deterioration) or are stable but inotrope-dependent (INTERMACS Profile #3). In addition, the INTERMACS Profile #4 group consists of patients with recurrent advanced heart failure (which is distinguished from refractory decompensation).

In general, most patients receiving durable LVADs have stage D and class IV heart failure. The evidence for routine use of LVADs to treat class III heart failure is still controversial. Most BTT patients have met institutional requirements for heart transplant. The authors use a similar workup for BTT and DT patients, including multidisciplinary assessment of comorbid conditions, behavior, and psychosocial characteristics.

Classic indications for DT versus BTT include, but are not limited to, the following:

• Age
• Diabetes
• Pulmonary hypertension
• Renal dysfunction
• Recent malignancy

Although most patients listed for transplant are at some level candidates for mechanical circulatory support, there are several compelling factors that might argue for going straight to transplant, including multiple reoperations, congenital heart anomalies, restrictive heart disease with small ventricles, and other surgical issues (eg, previous pericardiectomy). These are all relative contraindications.

Extreme body mass indices (BMIs)—that is, being extremely underweight or extremely overweight—are also considered contraindications to LVAD implantation. Prior observational reports have suggested that morbidly obese patients have higher rates of driveline infections after LVADs. This was confirmed in a large study of the HeartMate II database; however, BMI did not influence short- and long-term survival. ^[3]

The most important contraindication for LVAD therapy is a right ventricle (RV) that is unable to support LVAD flows. Although it is not unusual (<10% of cases) to require temporary RV assist device (RVAD) support at the time of LVAD support, if one has a high suspicion of RV failure (based, for example, on severe dysfunction with a low right ventricular stroke work index and high right atrial pressures), the best options are biventricular assist devices, total artificial heart replacement, and transplant.

The emergence of DT has a created a different set of issues. Many DT patients are older and have end-organ dysfunction, and implants are seen as the last option or even a heroic measure. The ability of these patients to survive and thrive after LVAD must be seriously and rigorously evaluated by a multidisciplinary team.

Although the cumulative effect of advances in technology (with the smaller pumps) and overall improvements on the management of these patients has been positive, LVAD therapy is still associated with significant morbidity and mortality. The operative mortality for these patients ranges from 10-30%, with some preoperative assessments suggesting that it may be even higher.

According to a 2014 study that assessed 139 consecutive LVAD implantations as a bridge to transplantation at a single institution, both HeartMate II and the HeartWare Ventricular Assist System were associated with excellent early postoperative outcomes and good midterm survival. ^[4]

Ammirati et al, in Milan, assessed outcomes in older (>55 years) patients with advanced heart failure who were treated either (a) with a continuous-flow LVAD (CF-LVAD) with a BTT or bridge-to-candidacy (BTC) indication or (b) with heart transplant. ^[5]  Early and midterm outcomes were better for CF-LVAD with BTT indication than for heart transplant in these patients. At 2-year follow-up, outcomes were similar for CF-LVAD with BTT or BTC indications and for heart transplant. The authors noted that these results require confirmation in larger, more varied populations and with longer follow-up periods.