Author + information
- aDepartment of Medicine, Duke University School of Medicine, Durham, North Carolina
- bDuke Clinical Research Institute, Duke University School of Medicine, Durham, North Carolina
- ↵∗Reprint requests and correspondence:
Dr. Adam D. DeVore, Duke Clinical Research Institute, 2400 Pratt Street, NP-7047B, Durham, North Carolina 27705.
Contemporary growth in the use of left ventricular assist devices (LVADs) to support patients with advanced heart failure is remarkable. In the United States alone, more than 2,400 LVADs were implanted in adults in 2014 compared with 459 in 2008 (1). Although perioperative survival is comparable to that for routine cardiac surgical procedures, 50% of LVAD patients have died within 4 years of implantation (1). Long-term management of LVAD patients remains enigmatic and program specific, lacks a robust evidence base, and could reasonably be postulated to contribute importantly to the observed morbidity and mortality. The most recent guideline on outpatient LVAD management cites only 3 of 69 (4.3%) recommendations as being Level of Evidence A (2) compared with 22% high-level recommendations in the most recent American College of Cardiology/American Heart Association heart failure guideline (3). Questions pertaining to common clinical conundrums such as the most appropriate dose of antiplatelet agents, the best strategy for the management of right-sided heart failure, and the optimal treatment for refractory mucosal bleeding remain eminence based. There is an urgent need to develop evidence that guides patient and device management for normal LVAD physiology and complications for this increasingly common and expensive medical intervention.
LVAD speed is the one parameter that can be adjusted to change the level of support provided by contemporary LVADs. Current technology for the 2 commercially available devices allows providers to select a single constant speed, ignoring the obvious changes in physiological demand that occur during daily life. Most providers determine optimal speed using echocardiographic guidance with the patient recumbent and at rest, selecting a speed that minimizes patient symptoms without excessively unloading the left ventricle. Alternatively, a ramp study may be utilized in which final settings are determined by careful study of the impact of graduated increases in device speed on patient symptoms, vital signs, ventricular geometry, and valve function (4).
In this issue of JACC: Heart Failure, Uriel et al. (5) extend their previous work on the noninvasive ramp study and describe an approach to determining optimal LVAD speed by integrating hemodynamic and echocardiographic parameters. The authors performed ramp studies with simultaneous right-sided heart catheterization and echocardiography in 35 stable outpatients thought to be well supported on their LVAD based on their reported medical history, physical examination, and laboratory test results (Figure 1). The goal was to define the LVAD speed associated with the most desirable hemodynamic and echocardiographic parameters: central venous pressure <12 mm Hg, pulmonary capillary wedge pressure <18 mm Hg, intermittent aortic valve opening, and minimized mitral regurgitation.
There was a striking discordance between clinical assessment of optimal hemodynamics and those found in the laboratory, with fewer than 50% of this cohort meeting the hemodynamic goals at baseline. After guided speed adjustment, the proportion of patients with desirable hemodynamic profiles increased from 43% to 56%, with nearly one-third of the patients requiring an important speed change as a result of the ramp test. An increase in LVAD speed resulted in patient-specific increases in cardiac output and reductions in pulmonary capillary wedge pressure without an acute change in the central venous pressure.
Although this study provides important new knowledge that may allow better patient and device management, important limitations must be acknowledged, the most obvious being the lack of clear linkage between speed optimization and outcomes. There are almost no clinical trial data that confirm a clear relationship between hemodynamics and outcomes in non–device-treated heart failure patients, which raises the possibility that this approach may not favorably impact symptoms, functional capacity, quality of life, or LVAD-related morbidity. In addition, broad application of invasive ramp studies in LVAD patients has inherent risk that must be weighed against the value of the information provided. The ventricular assist device community needs to be certain that there is tangible patient benefit beyond a modest hemodynamic benefit and more photogenic hearts. Finally, the durability of these hemodynamic changes and the potential that ramp testing should be repeated with some frequency must be addressed.
The number of patients in the United States eligible for advanced heart failure therapies is estimated to be between 250,000 and 300,000 (6), and the number of patients living in the community with LVAD support continues to grow. The establishment of an evidence base for the long-term management of patients with LVADs is essential. We continue to operate in silos of care that rely heavily on INTERMACS (Interagency Registry for Mechanically Assisted Circulatory Support) (7) to describe trends in LVAD use; however, INTERMACS may not be well suited for much of the heavy lifting required to improve VAD outcomes. Creation of an LVAD research network structured similarly to the National Institutes of Health–funded Heart Failure Research Network and the Cardiac Surgery Network would facilitate the development of foundational knowledge. These networks consist of high-volume centers committed to clinical trials with a well-defined infrastructure that allows rapid implementation and execution of small studies. With proper design, INTERMACS could be used as the data repository and analytical center for such a network and would promote synergies and broad application of successful interventions.
This past weekend, many of us may have worked diligently to assemble a piece of furniture, repair a car engine, or fix a computer glitch. Few would attempt such a feat without detailed instruction, sage counsel, proper tools, and an instruction manual. These tools, based on experience and experimentation, ensure success for “do-it-yourselfers.” We should not have a lower expectation for medical devices.
↵∗ Editorials published in JACC: Heart Failure reflect the views of the authors and do not necessarily represent the views of JACC: Heart Failure or the American College of Cardiology.
Dr. DeVore has received research funding from Amgen, the American Heart Association, Maquet, Novartis, and Thoratec. Dr. Rogers has reported that he has no relationships relevant to the contents of this paper to disclose.
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- ↵Interagency Registry for Mechanically Assisted Circulatory Support. INTERMACS website. Available at: https://www.uab.edu/medicine/intermacs/. Accessed November 10, 2015.