How does the 2018 UNOS (United Network for Organ Sharing) heart allocation system revision affect wait times for patients with advanced heart failure requiring Impella 5.5 (a temporary mechanical circulatory support device) support?

Manuscript Assessment: 2018 UNOS Heart Allocation Policy and Impella 5.5 Wait Times

Your manuscript is generally well-structured and appropriately referenced, but I notice several issues that should be addressed:

Critical Problems

Your manuscript relies heavily on outdated 1993 guidelines 1 that describe a 2-tier system (Status I and II) when discussing the modern 6-tier system implemented in 2018. This creates a fundamental mismatch between your historical context and current policy discussion. The 1993 Bethesda Conference guidelines are not relevant to explaining the 2018 policy changes or their impact on Impella 5.5-supported patients.

Specific Issues to Address

Reference Misalignment

• Your discussion of the 2018 policy expansion from 3-tier to 6-tier system lacks appropriate contemporary guideline support in your reference list
• The 1993 guidelines you cite [1-1-1] describe Status I (ICU with inotropes or mechanical support) and Status II (all others), which is completely different from the 2018 system's Status 1-6 classification
• You should replace these outdated guideline citations with contemporary sources that actually describe the 2018 allocation system

Missing Contemporary Guideline Context

• The 2024 AHA/ACC HCM guideline 1 mentions the 2018 UNOS policy specifically addressing HCM patients with advanced heart failure, noting "separate listing criteria and priority specific to patients with HCM" and that "these new listing criteria have significantly increased transplantation rates and reduced waitlist times in patients with HCM"
• The 2012 AHA MCS guideline 1 describes Impella 2.5 and 5.0 devices but predates the 5.5 device and the 2018 allocation policy entirely
• Your manuscript would benefit from citing more recent allocation policy guidelines rather than relying on 1993 documents

Research Evidence Utilization

• Your research citations appear appropriate and contemporary (2022-2025 studies on Impella 5.5 outcomes [2-3])
• However, you don't cite these studies in your manuscript draft, which is problematic
• The research evidence shows: Impella 5.5 patients had median waitlist duration of 19 days nationally, with 80% transplanted directly after the policy change 4, and waitlist mortality decreased from 25% to 13% post-policy 4

Structural Concerns

• Your discussion of Status 2 congestion and prolonged wait times is clinically important but lacks the supporting citations from your reference list
• The DCD donor discussion appears speculative without direct evidence linking Status 2 listing to DCD acceptance patterns
• Your limitations section appropriately acknowledges survivorship bias and lack of granular data

What Is NOT Wrong

• Your overall narrative flow is logical and clinically coherent
• The discussion of status extensions (1e, 2e) is appropriate and relevant
• Your acknowledgment of regional variation and practice patterns is important
• The limitations section is appropriately self-critical

Bottom Line

Replace the 1993 guideline citations with contemporary sources that actually describe the 2018 allocation system, and ensure your research citations [2-3] are actually used in the text where you discuss Impella 5.5 outcomes. The conceptual framework is sound, but the evidence base cited does not match the policy era you're discussing. This is not "extremely abnormal or bad," but it significantly undermines the scholarly rigor of your manuscript and will likely be caught in peer review.