**4. Selected subpopulations**

essentially equal between groups, especially in the absence of LVAD-related complications. Graft rejection also appears to be similar in patients who are bridged with LVADs compared

Currently, the European Society of Cardiology guidelines for treatment of end stage heart failure include the use of left ventricular assist devices as a Class IB recommendation in patient's refractory to medical therapy while waiting for a heart transplant. In addition, the American Heart Association has also issued a guidance document describing the use of mechanical circulatory support in the setting of bridge to transplant as a Class IB recommendation [12]. There is data to suggest that patients bridged to heart transplant with LVAD have higher posttransplant mortality compared to those without LVADs. However, much of this data stems from old risk calculations based on outcomes after implantation of pulsatile flow LVADs. As identified above, complication rates improved markedly as these devices have largely given

The current indications for heart transplantation include hemodynamically compromised patients with New York Heart Association class III-IV, as well as patients with stage D heart failure who are in refractory cardiogenic shock and dependent on intravenous inotropic support to maintain adequate organ perfusion. Further indications include severe angina that limits routine activity and is not amenable to revascularization, and recurrent symptomatic ventricular arrhythmias refractory to all other therapeutic modalities. Once listed, the current United Network for Organ Sharing (UNOS) organ-allocation system gives its highest transplant priority status (Status 1A) to those hospitalized patients who dependent on either inotropic medical therapy, or mechanical circulatory support such as LVAD support. UNOS designates an intermediate priority status (Status 1B) to those patients who are receiving inotropic or mechanical support at home. Patients who have infectious, bleeding, or thromboembolic complications while on VAD support may be advanced to 1A status until the time of transplantation; there is an additional discretionary option where patients with LVAD support may be advanced to Status 1A based on the decision of their transplant team and lasting for 1 month before downgrade back to 1B. Most other patients are given standard priority on

In order to assist with optimal patient selection for placement of an LVAD, the INTERMACS registry has developed seven clinical profiles to identify patients. (1) Level 1 includes patients who are in critical cardiogenic shock requiring mechanical support. (2) Level 2 includes patients who are declining despite inotropic support. (3) Level 3 includes patients who are stable on inotropic support. (4) Level 4 includes patients with resting symptoms. (5) Level 5 includes patients who are intolerant to exertion. (6) Level 6 includes patients who are able to engage in limited exertion. (7) Level 7 includes patients who have advanced NYHA III heart failure. In the early years of LVAD implementation, the first two profiles (Level 1 and 2) comprised 60–80% of the LVAD candidates who were considered to be candidates for bridge to transplant. More recently, a shift has occurred in response to improved patient selection and risk stratification such that that the majority of patients implanted are now INTERMACS 3 and 4 profiles. Currently, 80% of patients who are being implanted with LVAD fall within

way to continuous flow VADs with a more acceptable side-effect profile.

to those without LVADs.

50 Heart Transplantation

**3.2. General indications**

the waitlist (Status 2).

INTERMACS Levels 2–4 [13].

In addition to the patient indications listed above, there are a number of unique subpopulations with a need for heart transplantation that would potentially benefit from LVAD as a bridging therapy. For one, mechanical circulatory support is an acceptable bridge to transplantation in pediatric patients suffering from heart failure due to structural defects. The feasibility of mechanical support as a bridge to transplantation in this subgroup has been demonstrated in single- and multi-institutional [19] case reports. For example, a small retrospective case series in 2017 of five patients who underwent VAD placement for congenital heart defects with single ventricle physiology (mean age 12), had a 60% success rate in cardiac transplantation without long-standing end organ dysfunction [20]. The factors which play into the use of mechanical support in this population are the anatomy of the initial pathology and subsequent repairs, as well as pediatric patient size, which may predispose toward the use of smaller pumps over others. This relative safety of VAD support in pediatric patients has been confirmed in retrospective review of pediatric outcomes in the United Network for Organ Sharing database [21]. In general, it is agreed that pediatric patients should be analyzed on a case-by-case basis; although the rate of postoperative complications is high, the initiation of mechanical circulatory support can allow for resolution of end-organ dysfunction and allow for aggressive pre-transplant rehabilitation.

candidates supported with contemporary continuous-flow LVADs have favorable waiting list outcomes. However, outcomes worsen significantly once a serious LVAD-related complication occurs. In the current era, the annual rate of readmission for LVAD patients is 65% with most occurring in the first 6 months post-implant. The causes for readmission are multifactorial, are commonly due to gastrointestinal bleeding, cardiac causes, infections, and thrombo-

Heart Transplantation in the Era of the Left Ventricular Assist Devices

http://dx.doi.org/10.5772/intechopen.76935

53

Hasin et al. reported the findings of a single-institution analysis of readmissions due to complication after the implantation of ventricular assist devices over 2 years. The major primary causes in the first 6 months were bleeding (30%, primarily gastrointestinal), cardiac (30%, with

**Figure 2.** Complications rates, pulsatile versus two eras of continuous flow (extrapolated from INTERMACS Annual

reports: Kirklin et. al., 2011, 2012, 2013, and 2014).

sis (**Figure 2**).

With improved management of congenital disease, more pediatric patients are surviving into adulthood prior to transplantation; this represents a growing patient subpopulation in whom LVAD support may confer a benefit. The American Heart Association opinion paper on LVAD in adult congenital disease highlights the challenges of supporting these patients; the typical history of many prior surgical and nonsurgical interventions, as well as the complex anatomy and physiology of these patients poses a challenge in LVAD implementation. Additionally, the use of the LVAD in this population is hampered by a lack of multi-institutional data regarding selection criteria and surgical technique. It is reinforced that the ultimate goal for these patients is cardiac transplant, an intervention after which most appropriately-selected adults with congenital heart disease will have survival rivaling that of recipients [22].

One unique group that greatly benefits from LVAD placement are those individuals who do not initially meet transplant criteria. In this group, entitled, "bridge to candidacy", the LVAD may provide an opportunity to alleviate relative contraindications to transplantation, such as active smoking, poor social support, undiagnosed tumors, obesity, and advanced lung disease, whereas they would otherwise automatically exclude patients from transplantation. Several months of LVAD support can be enough time for this group to rehabilitate and become eligible for a transplant in the future. For example, one study showed the utility of LVAD implantation in patients with a body mass index (BMI) greater than 30 during the process of losing weight loss in order to become a candidate for eventual transplant [23]. Recently, laparoscopic sleeve gastrectomy has been highlighted as an option for patients who want to have cardiac transplantation after LVAD implant [24].

Additionally, patients with secondary pulmonary hypertension that is prohibitive of transplant have been shown to benefit from LVAD placement. Very high pulmonary vascular resistances fall over the course of months as the left ventricle is unloaded, allowing for future transplant candidacy.
