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arxiv: 1907.07669 · v1 · pith:PLVRJ6AJnew · submitted 2019-07-16 · 📊 stat.AP

Sequential Pattern mining of Longitudinal Adverse Events After Left Ventricular Assist Device Implant

Pith reviewed 2026-05-24 20:17 UTC · model grok-4.3

classification 📊 stat.AP
keywords LVADadverse eventssequential pattern mininghierarchical clusteringMarkov modelingINTERMACSheart failuredevice complications
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The pith

Seven groups of ordered adverse event chains follow LVAD implantation in registry data.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper converts records of 58,575 adverse events from 13,192 LVAD patients into chronological sequences per patient. It then applies hierarchical clustering to group patients with similar sequences and Markov modeling to extract the most probable ordered chains within each group. The result is seven distinct trajectories, each dominated by a recurring type and order of events such as recurrent bleeding or neurological dysfunction leading to death. A reader would care if these ordered patterns reflect real clinical interdependence rather than isolated events, because that would open routes to earlier prediction and targeted prevention after device implant.

Core claim

The mined results indicate the existence of seven groups of sequential chains of AEs, characterized by common types of AEs that occurred in a unique order. The groups were identified as: GRP1: Recurrent bleeding, GRP2: Trajectory of device malfunction & explant, GRP3: Infection, GRP4: Trajectories to transplant, GRP5: Cardiac arrhythmia, GRP6: Trajectory of neurological dysfunction & death, and GRP7: Trajectory of respiratory failure, renal dysfunction & death. These patterns of sequential post-LVAD AEs disclose potential interdependence between AEs and may aid prediction, and prevention, of subsequent AEs in future studies.

What carries the argument

The three-step procedure of converting each patient's adverse events into a single chronological sequence, grouping similar sequences by hierarchical clustering, and extracting temporal chains within each cluster via Markov modeling.

If this is right

  • The seven groups each follow a unique recurring order of adverse events.
  • The chains indicate potential interdependence among events after LVAD implant.
  • The identified patterns could support future efforts to predict later events from earlier ones.
  • The patterns could support future efforts to prevent later events from earlier ones.
  • Each group links to distinct clinical outcomes such as transplant, explant, or death.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Clinicians could monitor for the first event in a known chain to trigger earlier interventions aimed at blocking progression.
  • Risk models for LVAD patients might improve by incorporating event order rather than counting events independently.
  • The same sequencing-plus-clustering approach could be tested on other implanted devices or on non-device heart-failure cohorts to check whether similar ordered chains appear.
  • Validation would require checking whether patients assigned to one group show measurably higher rates of the predicted later events than patients in other groups.

Load-bearing premise

Converting recorded adverse events into patient sequences and then clustering plus Markov modeling will surface real clinical interrelations rather than artifacts of recording practices or algorithm choices.

What would settle it

Re-running the identical three-step procedure on the same INTERMACS data but with a different linkage method in clustering or a different order threshold in the Markov step produces groupings whose chains do not match the seven reported trajectories.

Figures

Figures reproduced from arXiv: 1907.07669 by Faezeh Movahedi, James F. Antaki, Laura Seese, Lisa Lohmueller, Manreet Kanwar, Rema Padman, Robert L. Kormos, Srinivas Murali, Yiye Zhang.

Figure 1
Figure 1. Figure 1: Illustration of HeartMate 3 LVAD from Thoratec [PITH_FULL_IMAGE:figures/full_fig_p001_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: General work-flow: 1. Data preprocessing:Forming patients’ sequences. 2. Hierarchical clustering:cluster patients into [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Color code for 15 types of AEs and final outcomes [PITH_FULL_IMAGE:figures/full_fig_p003_3.png] view at source ↗
Figure 5
Figure 5. Figure 5: The proportions of various types of AE in all the 13,192 [PITH_FULL_IMAGE:figures/full_fig_p004_5.png] view at source ↗
Figure 3
Figure 3. Figure 3: in which the proportions of each category of AE was [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗
Figure 6
Figure 6. Figure 6: length of AE sequences from 1 to 15. (Length of 16-32, [PITH_FULL_IMAGE:figures/full_fig_p005_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: The dissimilarity scores distribution of all the sequences [PITH_FULL_IMAGE:figures/full_fig_p005_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: First step of step-wise cluster evaluation: evaluation of the two-cluster solution [PITH_FULL_IMAGE:figures/full_fig_p006_8.png] view at source ↗
Figure 9
Figure 9. Figure 9: Regression tree showing groups formed at each step [PITH_FULL_IMAGE:figures/full_fig_p007_9.png] view at source ↗
Figure 10
Figure 10. Figure 10: MM of GRP1: Recurrent bleeding (n= 862 patients) [PITH_FULL_IMAGE:figures/full_fig_p008_10.png] view at source ↗
Figure 11
Figure 11. Figure 11: MM of GRP2: Trajectory of device malfunction & [PITH_FULL_IMAGE:figures/full_fig_p008_11.png] view at source ↗
Figure 12
Figure 12. Figure 12: MM of GRP3: Infection (n= 3,438 patients) [PITH_FULL_IMAGE:figures/full_fig_p009_12.png] view at source ↗
Figure 13
Figure 13. Figure 13: MM of GRP4: Trajectories to transplant (n= 3,302 [PITH_FULL_IMAGE:figures/full_fig_p009_13.png] view at source ↗
Figure 14
Figure 14. Figure 14: MM of GRP5: Cardiac arrhythmia (n= 1,275 patients) [PITH_FULL_IMAGE:figures/full_fig_p009_14.png] view at source ↗
Figure 15
Figure 15. Figure 15: MM of GRP6: Trajectory of neurological dysfunction [PITH_FULL_IMAGE:figures/full_fig_p010_15.png] view at source ↗
Figure 16
Figure 16. Figure 16: MM of GRP7: Trajectory of respiratory failure & [PITH_FULL_IMAGE:figures/full_fig_p010_16.png] view at source ↗
read the original abstract

Left ventricular assist devices (LVADs) are an increasingly common therapy for patients with advanced heart failure. However, implantation of the LVAD increases the risk of stroke, infection, bleeding, and other serious adverse events (AEs). Most post-LVAD AEs studies have focused on individual AEs in isolation, neglecting the possible interrelation, or causality between AEs. This study is the first to conduct an exploratory analysis to discover common sequential chains of AEs following LVAD implantation that are correlated with important clinical outcomes. This analysis was derived from 58,575 recorded AEs for 13,192 patients in International Registry for Mechanical Circulatory Support (INTERMACS) who received a continuousflow LVAD between 2006 and 2015. The pattern mining procedure involved three main steps: (1) creating a bank of AE sequences by converting the AEs for each patient into a single, chronologically sequenced record, (2) grouping patients with similar AE sequences using hierarchical clustering, and (3) extracting temporal chains of AEs for each group of patients using Markov modeling. The mined results indicate the existence of seven groups of sequential chains of AEs, characterized by common types of AEs that occurred in a unique order. The groups were identified as: GRP1: Recurrent bleeding, GRP2: Trajectory of device malfunction & explant, GRP3: Infection, GRP4: Trajectories to transplant, GRP5: Cardiac arrhythmia, GRP6: Trajectory of neurological dysfunction & death, and GRP7: Trajectory of respiratory failure, renal dysfunction & death. These patterns of sequential post-LVAD AEs disclose potential interdependence between AEs and may aid prediction, and prevention, of subsequent AEs in future studies.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

1 major / 1 minor

Summary. The manuscript presents an exploratory analysis of sequential patterns in adverse events (AEs) after LVAD implantation, using 58,575 AEs from 13,192 patients in the INTERMACS registry (2006-2015). It applies a three-step pipeline: (1) converting per-patient AEs into chronological sequences, (2) hierarchical clustering to group patients with similar sequences, and (3) Markov modeling to extract temporal chains within each cluster. The central claim is that this yields seven distinct groups with unique AE orders (recurrent bleeding; device malfunction & explant; infection; trajectories to transplant; cardiac arrhythmia; neurological dysfunction & death; respiratory failure, renal dysfunction & death) that disclose AE interdependencies and may aid prediction.

Significance. If the seven groups prove robust, the work would offer a data-driven view of AE interdependence beyond isolated-event studies, leveraging a large registry sample to generate clinically relevant hypotheses. The approach is novel in this domain, but the lack of reported validation means the claimed patterns cannot yet be distinguished from artifacts of follow-up length, coding conventions, or clustering choices.

major comments (1)
  1. [Abstract (three-step procedure)] Abstract, description of the three-step procedure: no cluster-quality metrics, linkage/distance sensitivity tests, permutation-based null distributions, or stability checks on the number of clusters are described. This is load-bearing for the central claim, as the seven groups and their 'unique order' Markov chains could reflect the most frequent event multisets, variable follow-up lengths, or arbitrary cluster count rather than genuine temporal interdependence.
minor comments (1)
  1. [Abstract] Abstract: the total sample size (13,192 patients) and AE count (58,575) appear only after the first sentence; moving these figures earlier would improve readability.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the constructive feedback on our exploratory analysis of sequential adverse event patterns following LVAD implantation. We address the concern regarding validation of the clustering step below.

read point-by-point responses
  1. Referee: Abstract, description of the three-step procedure: no cluster-quality metrics, linkage/distance sensitivity tests, permutation-based null distributions, or stability checks on the number of clusters are described. This is load-bearing for the central claim, as the seven groups and their 'unique order' Markov chains could reflect the most frequent event multisets, variable follow-up lengths, or arbitrary cluster count rather than genuine temporal interdependence.

    Authors: We agree that the abstract does not describe these validation elements. The manuscript is explicitly exploratory and selected seven clusters based on the dendrogram combined with clinical interpretability and association with outcomes; however, the referee is correct that additional quantitative checks are needed to rule out artifacts from follow-up duration, event frequency, or arbitrary k. In the revised manuscript we will add: (i) silhouette scores and other cluster-quality metrics, (ii) sensitivity analyses across linkage methods and distance measures, (iii) bootstrap stability assessment of the seven-cluster solution, and (iv) permutation-based null distributions that preserve marginal AE frequencies and censoring patterns to test whether the observed groupings and Markov chains are stronger than expected by chance. These results will be reported in the Methods and Results sections and the abstract will be updated to note the validation steps performed. revision: yes

Circularity Check

0 steps flagged

No circularity: unsupervised sequence mining on external registry

full rationale

The paper applies a standard three-step unsupervised pipeline (sequence construction from INTERMACS registry, hierarchical clustering, per-cluster Markov modeling) to discover seven AE groups. No equations, fitted parameters, or self-citations are shown that reduce the output groups or their temporal orders to quantities defined inside the same model. The derivation is self-contained against the external data source and does not invoke uniqueness theorems or ansatzes from prior author work.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

The central claim rests on the completeness and chronological accuracy of the INTERMACS adverse-event records and on the validity of the chosen clustering-plus-Markov pipeline for revealing predictive rather than spurious sequences.

free parameters (1)
  • number of clusters
    The procedure groups patients into seven clusters; the choice of seven is presented as the result of the analysis but functions as a modeling decision that shapes the reported groups.
axioms (1)
  • domain assumption Adverse events in the INTERMACS registry are recorded with sufficient completeness and accurate timestamps to support chronological sequencing.
    Step (1) of the procedure converts each patient's AEs into a single chronologically sequenced record; any systematic under-recording or timestamp error would propagate into the clusters.

pith-pipeline@v0.9.0 · 5895 in / 1290 out tokens · 16555 ms · 2026-05-24T20:17:40.706654+00:00 · methodology

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Reference graph

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