{'fraction_non_alphanumeric': 0.024165707710011506, 'fraction_numerical': 0.017548906789413118, 'mean_word_length': 5.5852272727272725, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Response by Truby and Topkara to Letter Regarding Article, "Impact of Bridge to Transplantation With Continuous-Flow Left Ventricular Assist Devices on Posttransplantation Mortality: A Propensity-Matched Analysis of the United Network of Organ Sharing Database".

Circulation. 2019;140:e942–e943. DOI: 10.1161/CIRCULATIONAHA.119.044323 e942 Lauren K. Truby, MD Veli K. Topkara, MD In Response: We appreciate the excellent commentary by Pal et al on our recent article in Circulation describing the increased risk of early posttransplantation mortality associated with bridge to transplantation (BTT) with contemporary left ventricular assist devices (LVADs).1 The authors raise several important points that we wish to address. As the authors referred to in their letter, several studies from the United Network of Organ Sharing and International Society for Heart and Lung Transplantation Registry have previously failed to demonstrate increased posttransplantation mortality in LVAD-supported patients. However, it is important to recognize differences in sample size, variables examined, statistical approach, and change in practice across these studies. In the study by Weiss et al,2 only 2% of patients were bridged with contemporary LVADs, making it challenging to extrapolate findings in the current era. In the study by Nativi et al,3 many variables that could have an impact on posttransplantation outcomes, such as United Network of Organ Sharing status at transplantation, blood type, United Network of Organ Sharing region, and time on waitlist, were not included in the multivariable model. Our analysis included the largest number of contemporary patients with LVADs analyzed from United Network of Organ Sharing to date and used propensity matching to ensure a balance of risk factors that could influence LVAD use and posttransplantation mortality. Furthermore, our analysis suggests that patients stay on LVAD support much longer until cardiac transplantation, and these patients have a higher risk of posttransplantation mortality. Older studies involve patients who are bridged to transplantation after a shorter course on LVAD and may not reflect current practice. In fact, the 2019 International Society for Heart and Lung Transplantation Registry Report suggests that use of a ventricular assist device before transplantation is associated with increased 1-year posttransplantation mortality (HR, 1.1 [CI, 1.01–1.22], P=0.03), confirming our findings.4 Another excellent point raised by the authors is the clinical distinction between patients who require BTT LVAD after medical optimization has failed versus those who never required an LVAD before cardiac transplantation. Although we agree with the comment, a large proportion of patients receive BTT LVADs as an Interagency Registry for Mechanically Assisted Circulatory Support Profile 3-7, indicating clinical stability on medical therapy.5 Conversely, patients with an Interagency Registry for Mechanically Assisted Circulatory Support Profile 1-2 can go onto cardiac transplantation on multiple high-dose inotropes with or without temporary mechanical circulatory support and do not always require a durable device implant for bridging. Therefore, there is significant overlap in clinical scenarios, and clinical decision making is far more complex with regard to bridging strategies at the level of the individual patient. © 2019 American Heart Association, Inc. RESPONSE TO LETTER TO THE EDITOR