As an established therapy for end-stage heart failure, LVAD is being increasingly implemented as DT in older patients.
Our systematic review of seven single-center institutional studies (657 patients) demonstrates that age, aortic valve closure, implant as DT, and duration of implant were important factors associated with the production of de novo AI. Continuous flow devices were more prone to develop AI rather than pulsatile devices.
The important relationship between age and AI has been demonstrated since the Framingham Study.15,16 The LVAD physiology, especially with continuous flow, hastens the age-related degeneration of the valve. The relative inelasticity of the aged aorta, increased sheer stress, and high diastolic luminal pressures adversely affect the valve leaflets as well as the support mechanism. AI is associated with increased medial disruption and degeneration,17 which would naturally lead to poor valve support and progressive AI. Both position and angle of the outflow graft and native aorta are important in determining hemodynamic alterations in the ascending aorta.18,19 Commissural fusion of the aortic valve occurs in patients supported on a Cf-LVAD.20 Martina et al.21 demonstrated that AI was present in all patients with commissural fusion and 67% patients without this abnormality. Importantly, development of this pathology was not related to the age of the patient or the duration of LVAD support.21 This demonstrates the importance of maintaining a pulsatile circuit with at least partial valve opening with each systole.
Our pooled analysis demonstrates that continuous-flow physiology is an important factor in the development of AI. This is highlighted by two important findings: 1) patients who had relatively closed aortic valves were more prone to develop AI and 2) AI was more often seen in patients with Cf-LVAD compared to pulsatile pumps. Partial support was associated with lower amount of commissural pathology.21 Thus, while we are increasingly using Cf-LVADs for their easier implant abilities and improved engineering, we need to take a close look at optimal device settings. Maintaining adequate cardiac output with some native ventricular ejection should be our goal. The Jarvik device does transiently reduce speed to promote valve opening. Reports regarding the long-term clinical benefit of this unique setting are still awaited.
A pooled analysis of three studies failed to demonstrate any difference in long-term survival in both cohorts. While that may be true, a significant number of AI-positive patients (24%) underwent transplantation as a bailout procedure. Only one study in this analysis consisted of patients with a large DT cohort, while other studies predominantly contained a BTT population.8 With a 70% survival on Cf-LVAD therapy at the end of 2 years, the number of LVAD supported with progressive AI is going to increase.22 A multi-institutional prospective study is needed to help us to define the incidence, risk factors, and clinical importance of condition.
A large multi-institutional prospective study will help improve our understanding of this clinical condition and guide us regarding the appropriate use of concomitant aortic valve repair during LVAD implant.
We have conducted a meta-analysis of observational data. All included articles are from single-center institutional data; some variation in patient selection, operative technique and, most importantly, LVAD settings are bound to be present. To account for some bias, we have adopted a random effects model and conducted a meta-regression in the presence of high heterogeneity. Publication bias was not assessed due to the small number of studies included in the meta-analysis.
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congestive heart failure; left ventricular assist device; aortic insufficiency