Current practices in the management of temporary mechanical circulatory support: A survey of CICU directors in North America.

INTRODUCTION: Despite the growing use of temporary mechanical circulatory support (tMCS), little data exists to inform management and weaning of these devices. METHODS: We performed an online survey among cardiac intensive care unit directors in North America to examine current practices in the management of patients treated with intraaortic balloon pump and Impella. RESULTS: We received responses from 84% of surveyed centers (n=37). Our survey focused on three key aspects of daily management: 1. Hemodynamic monitoring; 2. Hemocompatibility; and 3. Weaning and removal. We found substantial variability surrounding all three areas of care. CONCLUSION: Our findings highlight the need for consensus around practices associated with improved outcomes in patients treated with tMCS.

Modes of Death in Patients with Cardiogenic Shock in the Cardiac Intensive Care Unit: A Report from the Critical Care Cardiology Trials Network.

BACKGROUND: There are limited data on how patients with cardiogenic shock (CS) die. METHODS: The Critical Care Cardiology Trials Network is a research network of cardiac intensive care units coordinated by the Thrombolysis In Myocardial Infarction (TIMI) Study Group (Boston, MA). Using standardized definitions, site investigators classified direct modes of in-hospital death for CS admissions (October 2021 to September 2022). Mutually exclusive categories included 4 modes of cardiovascular death and 4 modes of noncardiovascular death. Subgroups defined by CS type, preceding cardiac arrest (CA), use of temporary mechanical circulatory support (tMCS), and transition to comfort measures were evaluated. RESULTS: Among 1068 CS cases, 337 (31.6%) died during the index hospitalization. Overall, the mode of death was cardiovascular in 82.2%. Persistent CS was the dominant specific mode of death (66.5%), followed by arrhythmia (12.8%), anoxic brain injury (6.2%), and respiratory failure (4.5%). Patients with preceding CA were more likely to die from anoxic brain injury (17.1% vs 0.9%; P < .001) or arrhythmia (21.6% vs 8.4%; P < .001). Patients managed with tMCS were more likely to die from persistent shock (P < .01), both cardiogenic (73.5% vs 62.0%) and noncardiogenic (6.1% vs 2.9%). CONCLUSIONS: Most deaths in CS are related to direct cardiovascular causes, particularly persistent CS. However, there is important heterogeneity across subgroups defined by preceding CA and the use of tMCS.

Computational prediction of protein subdomain stability in MYBPC3 enables clinical risk stratification in hypertrophic cardiomyopathy and enhances variant interpretation.

PURPOSE: Variants in MYBPC3 causing loss of function are the most common cause of hypertrophic cardiomyopathy (HCM). However, a substantial number of patients carry missense variants of uncertain significance (VUS) in MYBPC3. We hypothesize that a structural-based algorithm, STRUM, which estimates the effect of missense variants on protein folding, will identify a subgroup of HCM patients with a MYBPC3 VUS associated with increased clinical risk. METHODS: Among 7,963 patients in the multicenter Sarcomeric Human Cardiomyopathy Registry (SHaRe), 120 unique missense VUS in MYBPC3 were identified. Variants were evaluated for their effect on subdomain folding and a stratified time-to-event analysis for an overall composite endpoint (first occurrence of ventricular arrhythmia, heart failure, all-cause mortality, atrial fibrillation, and stroke) was performed for patients with HCM and a MYBPC3 missense VUS. RESULTS: We demonstrated that patients carrying a MYBPC3 VUS predicted to cause subdomain misfolding (STRUM+, ΔΔG ≤ -1.2 kcal/mol) exhibited a higher rate of adverse events compared with those with a STRUM- VUS (hazard ratio = 2.29, P = 0.0282). In silico saturation mutagenesis of MYBPC3 identified 4,943/23,427 (21%) missense variants that were predicted to cause subdomain misfolding. CONCLUSION: STRUM identifies patients with HCM and a MYBPC3 VUS who may be at higher clinical risk and provides supportive evidence for pathogenicity.

Imbalance of Hsp70 family variants fosters tau accumulation.

Dysfunctional tau accumulation is a major contributing factor in tauopathies, and the heat-shock protein 70 (Hsp70) seems to play an important role in this accumulation. Several reports suggest that Hsp70 proteins can cause tau degradation to be accelerated or slowed, but how these opposing activities are controlled is unclear. Here we demonstrate that highly homologous variants in the Hsp70 family can have opposing effects on tau clearance kinetics. When overexpressed in a tetracycline (Tet)-based protein chase model, constitutive heat shock cognate 70 (Hsc70) and inducible Hsp72 slowed or accelerated tau clearance, respectively. Tau synergized with Hsc70, but not Hsp72, to promote microtubule assembly at nearly twice the rate of either Hsp70 homologue in reconstituted, ATP-regenerating Xenopus extracts supplemented with rhodamine-labeled tubulin and human recombinant Hsp72 and Hsc70. Nuclear magnetic resonance spectroscopy with human recombinant protein revealed that Hsp72 had greater affinity for tau than Hsc70 (I/I0 ratio difference of 0.3), but Hsc70 was 30 times more abundant than Hsp72 in human and mouse brain tissue. This indicates that the predominant Hsp70 variant in the brain is Hsc70, suggesting that the brain environment primarily supports slower tau clearance. Despite its capacity to clear tau, Hsp72 was not induced in the Alzheimer's disease brain, suggesting a mechanism for age-associated onset of the disease. Through the use of chimeras that blended the domains of Hsp72 and Hsc70, we determined that the reason for these differences between Hsc70 and Hsp72 with regard to tau clearance kinetics lies within their C-terminal domains, which are essential for their interactions with substrates and cochaperones. Hsp72 but not Hsc70 in the presence of tau was able to recruit the cochaperone ubiquitin ligase CHIP, which is known to facilitate the ubiquitination of tau, describing a possible mechanism of how the C-termini of these homologous Hsp70 variants can differentially regulate tau triage. Thus, efforts to promote Hsp72 expression and inhibit Hsc70 could be therapeutically relevant for tauopathies.

Identification of key hinge residues important for nucleotide-dependent allostery in E. coli Hsp70/DnaK.

DnaK is a molecular chaperone that has important roles in protein folding. The hydrolysis of ATP is essential to this activity, and the effects of nucleotides on the structure and function of DnaK have been extensively studied. However, the key residues that govern the conformational motions that define the apo, ATP-bound, and ADP-bound states are not entirely clear. Here, we used molecular dynamics simulations, mutagenesis, and enzymatic assays to explore the molecular basis of this process. Simulations of DnaK's nucleotide-binding domain (NBD) in the apo, ATP-bound, and ADP/Pi-bound states suggested that each state has a distinct conformation, consistent with available biochemical and structural information. The simulations further suggested that large shearing motions between subdomains I-A and II-A dominated the conversion between these conformations. We found that several evolutionally conserved residues, especially G228 and G229, appeared to function as a hinge for these motions, because they predominantly populated two distinct states depending on whether ATP or ADP/Pi was bound. Consistent with the importance of these "hinge" residues, alanine point mutations caused DnaK to have reduced chaperone activities in vitro and in vivo. Together, these results clarify how sub-domain motions communicate allostery in DnaK.

Post-intensive cardiac care outpatient long-term outreach clinic (PICCOLO clinic): Defining health care needs and outcomes among coronary care unit survivors.

Objective: Patients who survive critical illness endure complex physical and mental health conditions, referred to as post-intensive care syndrome (PICS). The University of Michigan's post-intensive cardiac care outpatient long-term outreach (PICCOLO) clinic is designed for patients recently admitted to the coronary care unit (CCU). The long-term goal of this clinic is to understand post-CCU patients' needs and design targeted interventions to reduce their morbidity and mortality post-discharge. As a first step toward this goal, we aimed to define the post-discharge needs of CCU survivors. Design setting particpants: We retrospectively reviewed case-mix data (including rates of depression, PTSD, disability, and cognitive abnormalities) and health outcomes for patients referred to the PICCOLO clinic from July 1, 2018, through June 30, 2021 at Michigan Medicine. Results: Of the 134 referred patients meeting inclusion criteria, 74 (55 %) patients were seen in the PICCOLO clinic within 30 days of discharge. Patients seen in the clinic frequently screened positive for depression (PHQ-2 score ≥3, 21.4 %) and cognitive impairment (MOCA <26, 38.8 %). Further, patients also reported high rates of physical difficulty (mean WHODAS 2.0 score 28.4 %, consistent with moderate physical difficulty). Consistent with medical intensive care unit (ICU) patients, CCU survivors experience PICS. Conclusion: This work highlights the feasibility of an outpatient care model and the need to leverage information gathered from this care model to develop treatment strategies and pathways to address symptoms of PICS in CCU survivors, including depression, cognitive impairment, and physical disability.

Continuum of Preshock to Classic Cardiogenic Shock in the Critical Care Cardiology Trials Network Registry.

BACKGROUND: The prognostic implications of phenotypes along the preshock to cardiogenic shock (CS) continuum remain uncertain. OBJECTIVES: This study sought to better characterize pre- or early shock and normotensive CS phenotypes and examine outcomes compared to those with conventional CS. METHODS: The CCCTN (Critical Care Cardiology Trials Network) is a registry of contemporary cardiac intensive care units. Consecutive admissions (N = 28,703 across 47 sites) meeting specific criteria based on hemodynamic variables, perfusion parameters, and investigator-reported CS were classified into 1 of 4 groups or none: isolated low cardiac output (CO), heart failure with isolated hypotension, normotensive CS, or SCAI (Society of Cardiovascular Angiography and Intervention) stage C CS. Outcomes of interest were in-hospital mortality and incidence of subsequent hypoperfusion among pre- and early shock states. RESULTS: A total of 2,498 admissions were assigned to the 4 groups with the following distribution: 4.8% isolated low CO, 4.4% isolated hypotension, 12.1% normotensive CS, and 78.7% SCAI stage C CS. Overall in-hospital mortality was 21.3% (95% CI: 19.7%-23.0%), with a gradient across phenotypes (isolated low CO 3.6% [95% CI: 1.0%-9.0%]; isolated hypotension 11.0% [95% CI: 6.9%-16.6%]; normotensive CS 17.0% [95% CI 13.0%-21.8%]; SCAI stage C CS 24.0% [95% CI: 22.1%-26.0%]; global P < 0.001). Among those with an isolated low CO and isolated hypotension on admission, 47 (42.3%) and 56 (30.9%) subsequently developed hypoperfusion. CONCLUSIONS: In a large contemporary registry of cardiac critical illness, there exists a gradient of mortality for phenotypes along the preshock to CS continuum with risk for subsequent worsening of preshock states. These data may inform refinement of CS definitions and severity staging.

Epidemiology of cardiogenic shock using the Shock Academic Research Consortium (SHARC) consensus definitions.

AIMS: The Shock Academic Research Consortium (SHARC) recently proposed pragmatic consensus definitions to standardize classification of cardiogenic shock (CS) in registries and clinical trials. We aimed to describe contemporary CS epidemiology using the SHARC definitions in a cardiac intensive care unit (CICU) population. METHODS AND RESULTS: The Critical Care Cardiology Trials Network (CCCTN) is a multinational research network of advanced CICUs coordinated by the TIMI Study Group (Boston, MA). Cardiogenic shock was defined as a cardiac disorder resulting in SBP < 90 mmHg for ≥30 min [or the need for vasopressors, inotropes, or mechanical circulatory support (MCS) to maintain SBP ≥ 90 mmHg] with evidence of hypoperfusion. Primary aetiologic categories included acute myocardial infarction-related CS (AMI-CS), heart failure-related CS (HF-CS), and non-myocardial (secondary) CS. Post-cardiotomy CS was not included. Heart failure-related CS was further subcategorized as de novo vs. acute-on-chronic HF-CS. Patients with both cardiogenic and non-cardiogenic components of shock were classified separately as mixed CS. Of 8974 patients meeting shock criteria (2017-23), 65% had isolated CS and 17% had mixed shock. Among patients with CS (n = 5869), 27% had AMI-CS (65% STEMI), 59% HF-CS (72% acute-on-chronic, 28% de novo), and 14% secondary CS. Patients with AMI-CS and de novo HF-CS were most likely to have had concomitant cardiac arrest (P < 0.001). Patients with AMI-CS and mixed CS were most likely to present in more severe shock stages (SCAI D or E; P < 0.001). Temporary MCS use was highest in AMI-CS (59%). In-hospital mortality was highest in mixed CS (48%), followed by AMI-CS (41%), similar in de novo HF-CS (31%) and secondary CS (31%), and lowest in acute-on-chronic HF-CS (25%; P < 0.001). CONCLUSION: SHARC consensus definitions for CS classification can be pragmatically applied in contemporary registries and reveal discrete subpopulations of CS with distinct phenotypes and outcomes that may be relevant to clinical practice and future research.

The E3 ubiquitin ligase CHIP and the molecular chaperone Hsc70 form a dynamic, tethered complex.

The E3 ubiquitin ligase CHIP (C-terminus of Hsc70 Interacting Protein, a 70 kDa homodimer) binds to the molecular chaperone Hsc70 (a 70 kDa monomer), and this complex is important in both the ubiquitination of Hsc70 and the turnover of Hsc70-bound clients. Here we used NMR spectroscopy, biolayer interferometry, and fluorescence polarization to characterize the Hsc70-CHIP interaction. We found that CHIP binds tightly to two molecules of Hsc70 forming a 210 kDa complex, with a Kd of approximately 60 nM, and that the IEEVD motif at the C-terminus of Hsc70 (residues 642-646) is both necessary and sufficient for binding. Moreover, the same motif is required for CHIP-mediated ubiquitination of Hsc70 in vitro, highlighting its functional importance. Relaxation-based NMR experiments on the Hsc70-CHIP complex determined that the two partners move independently in solution, similar to "beads on a string". These results suggest that a dynamic C-terminal region of Hsc70 provides for flexibility between CHIP and the chaperone, allowing the ligase to "search" a large space and engage in productive interactions with a wide range of clients. In support of this suggestion, we find that deleting residues 623-641 of the C-terminal region, while retaining the IEEVD motif, caused a significant decrease in the efficiency of Hsc70 ubiquitination by CHIP.

An Unbiased Screen Identified the Hsp70-BAG3 Complex as a Regulator of Myosin-Binding Protein C3.

Variants in the gene myosin-binding protein C3 (MYBPC3) account for approximately 50% of familial hypertrophic cardiomyopathy (HCM), leading to reduced levels of myosin-binding protein C3 (MyBP-C), the protein product made by gene MYBPC3. Elucidation of the pathways that regulate MyBP-C protein homeostasis could uncover new therapeutic strategies. Toward this goal, we screened a library of 2,426 bioactive compounds and identified JG98, an allosteric modulator of heat shock protein 70 that inhibits interaction with Bcl-2-associated athanogene (BAG) domain co-chaperones. JG98 reduces MyBP-C protein levels. Furthermore, genetic reduction of BAG3 phenocopies treatment with JG-98 by reducing MYBP-C protein levels.. Thus, an unbiased compound screen identified the heat shock protein 70-BAG3 complex as a regulator of MyBP-C stability.

Prognostic significance of haemodynamic parameters in patients with cardiogenic shock.

AIMS: Invasive haemodynamic assessment with a pulmonary artery catheter is often used to guide the management of patients with cardiogenic shock (CS) and may provide important prognostic information. We aimed to assess prognostic associations and relationships to end-organ dysfunction of presenting haemodynamic parameters in CS. METHODS AND RESULTS: The Critical Care Cardiology Trials Network is an investigator-initiated multicenter registry of cardiac intensive care units (CICUs) in North America coordinated by the TIMI Study Group. Patients with CS (2018-2022) who underwent invasive haemodynamic assessment within 24 h of CICU admission were included. Associations of haemodynamic parameters with in-hospital mortality were assessed using logistic regression, and associations with presenting serum lactate were assessed using least squares means regression. Sensitivity analyses were performed excluding patients on temporary mechanical circulatory support and adjusted for vasoactive-inotropic score. Among the 3603 admissions with CS, 1473 had haemodynamic data collected within 24 h of CICU admission. The median cardiac index was 1.9 (25th-75th percentile, 1.6-2.4) L/min/m2 and mean arterial pressure (MAP) was 74 (66-86) mmHg. Parameters associated with mortality included low MAP, low systolic blood pressure, low systemic vascular resistance, elevated right atrial pressure (RAP), elevated RAP/pulmonary capillary wedge pressure ratio, and low pulmonary artery pulsatility index. These associations were generally consistent when controlling for the intensity of background pharmacologic and mechanical haemodynamic support. These parameters were also associated with higher presenting serum lactate. CONCLUSION: In a contemporary CS population, presenting haemodynamic parameters reflecting decreased systemic arterial tone and right ventricular dysfunction are associated with adverse outcomes and systemic hypoperfusion.

Translation of New and Emerging Therapies for Genetic Cardiomyopathies.

The primary etiology of a diverse range of cardiomyopathies is now understood to be genetic, creating a new paradigm for targeting treatments on the basis of the underlying molecular cause. This review provides a genetic and etiologic context for the traditional clinical classifications of cardiomyopathy, including molecular subtypes that may exhibit differential responses to existing or emerging treatments. The authors describe several emerging cardiomyopathy treatments, including gene therapy, direct targeting of myofilament function, protein quality control, metabolism, and others. The authors discuss advantages and disadvantages of these approaches and indicate areas of high potential for short- and longer term efficacy.

Impact of a pharmacist in an interdisciplinary post-cardiac intensive care unit clinic.

BACKGROUND: The complex needs of cardiac patients shortly after discharge from a cardiac intensive care unit (CICU) provides a unique opportunity for a pharmacist to help optimize medication management and guideline-directed medical therapy (GDMT). OBJECTIVE: This study describes the impact of a pharmacist in a multidisciplinary post-CICU clinic. METHODS: We performed a retrospective cohort study of patients ≥18 years of age who completed a visit in the University of Michigan Post Intensive Cardiac Care Outpatient Long-Term Outreach (PICCOLO) Clinic from July 2018 to May 2020. RESULTS: One hundred and six CICU survivors were referred. Of these 12 chose to follow-up with long term care providers. A total of 70 of the remaining 94 (74%) completed a visit. The median age was 65 (54-72) years, 71.4% were male, and 85.7% were Caucasian. The median number of pharmacist interventions at each visit was 4 (3-5), all patients had at least 1 intervention. Interventions included medication dose adjustment (n = 46); GDMT optimization (n = 42); medication change (n = 18); medication addition (n = 23) and cessation (n = 21); lab monitoring (n = 97); refill assistance (n = 16); pillbox provision (n = 8); and medication cost assistance (n = 8). CONCLUSIONS: Pharmacist led interventions in a post CICU clinic resulted in medication changes to optimize therapy, increased laboratory monitoring, medication cost savings for patients, and interventions to facilitate GDMT adherence.

Mutagenesis reveals the complex relationships between ATPase rate and the chaperone activities of Escherichia coli heat shock protein 70 (Hsp70/DnaK).

The Escherichia coli 70-kDa heat shock protein, DnaK, is a molecular chaperone that engages in a variety of cellular activities, including the folding of proteins. During this process, DnaK binds its substrates in coordination with a catalytic ATPase cycle. Both the ATPase and protein folding activities of DnaK are stimulated by its co-chaperones, DnaJ and GrpE. However, it is not yet clear how changes in the stimulated ATPase rate of DnaK impact the folding process. In this study, we performed mutagenesis throughout the nucleotide-binding domain of DnaK to generate a collection of mutants in which the stimulated ATPase rates varied from 0.7 to 13.6 pmol/microg/min(-1). We found that this range was largely established by differences in the ability of the mutants to be stimulated by one or both of the co-chaperones. Next, we explored how changes in ATPase rate might impact refolding of denatured luciferase in vitro and found that the two activities were poorly correlated. Unexpectedly, we found several mutants that refold luciferase normally in the absence of significant ATP turnover, presumably by increasing the flexibility of DnaK. Finally, we tested whether DnaK mutants could complement growth of DeltadnaK E. coli cells under heat shock and found that the ability to refold luciferase was more predictive of in vivo activity than ATPase rate. This study provides insights into how flexibility and co-chaperone interactions affect DnaK-mediated ATP turnover and protein folding.

Spatial and Functional Distribution of MYBPC3 Pathogenic Variants and Clinical Outcomes in Patients With Hypertrophic Cardiomyopathy.

BACKGROUND: Pathogenic variants in MYBPC3, encoding cardiac MyBP-C (myosin binding protein C), are the most common cause of familial hypertrophic cardiomyopathy. A large number of unique MYBPC3 variants and relatively small genotyped hypertrophic cardiomyopathy cohorts have precluded detailed genotype-phenotype correlations. METHODS: Patients with hypertrophic cardiomyopathy and MYBPC3 variants were identified from the Sarcomeric Human Cardiomyopathy Registry. Variant types and locations were analyzed, morphological severity was assessed, and time-event analysis was performed (composite clinical outcome of sudden death, class III/IV heart failure, left ventricular assist device/transplant, atrial fibrillation). For selected missense variants falling in enriched domains, myofilament localization and degradation rates were measured in vitro. RESULTS: Among 4756 genotyped patients with hypertrophic cardiomyopathy in Sarcomeric Human Cardiomyopathy Registry, 1316 patients were identified with adjudicated pathogenic truncating (N=234 unique variants, 1047 patients) or nontruncating (N=22 unique variants, 191 patients) variants in MYBPC3. Truncating variants were evenly dispersed throughout the gene, and hypertrophy severity and outcomes were not associated with variant location (grouped by 5'-3' quartiles or by founder variant subgroup). Nontruncating pathogenic variants clustered in the C3, C6, and C10 domains (18 of 22, 82%, P<0.001 versus Genome Aggregation Database common variants) and were associated with similar hypertrophy severity and adverse event rates as observed with truncating variants. MyBP-C with variants in the C3, C6, and C10 domains was expressed in rat ventricular myocytes. C10 mutant MyBP-C failed to incorporate into myofilaments and degradation rates were accelerated by ≈90%, while C3 and C6 mutant MyBP-C incorporated normally with degradation rate similar to wild-type. CONCLUSIONS: Truncating variants account for 91% of MYBPC3 pathogenic variants and cause similar clinical severity and outcomes regardless of location, consistent with locus-independent loss-of-function. Nontruncating MYBPC3 pathogenic variants are regionally clustered, and a subset also cause loss of function through failure of myofilament incorporation and rapid degradation. Cardiac morphology and clinical outcomes are similar in patients with truncating versus nontruncating variants.

Analysis of the interaction of BCL9 with beta-catenin and development of fluorescence polarization and surface plasmon resonance binding assays for this interaction.

The transcriptional activator beta-catenin is the primary mediator of the canonical Wnt signaling pathway and is frequently upregulated in many types of human cancer. Recent studies have suggested that the interaction of beta-catenin and its cofactor, B-cell lymphoma 9 (BCL9), is crucial for its transcriptional activity. Targeting this interaction using small molecules will improve our understanding of the beta-catenin/Wnt signaling pathway and may lead to the development of a new class of anticancer drugs. In this study, we developed a fluorescence polarization (FP)-based BCL9 binding assay. Using our initial FP assay, we performed extensive mutational analysis on four critical hydrophobic residues in the BCL9 peptide and determined the precise region in BCL9 responsible for binding to beta-catenin. These results led to further optimization of our FP assay, making it amenable for high-throughput screening (HTS). We also developed and validated a complementary surface plasmon resonance (SPR)-based binding assay and showed that our synthetic BCL9-based peptides are capable of fully inhibiting the binding of beta-catenin to wild-type BCL9 protein. Our studies provide not only further insight into the interaction between BCL9 and beta-catenin but also quantitative and reliable biochemical binding assays for the discovery of potent and specific small-molecule inhibitors of this interaction.

Utilization of Cardiac Rehabilitation Among Cardiac Intensive Care Unit Survivors.

Cardiac rehabilitation (CR) is associated with decreased mortality and rehospitalization rates for patients with a variety of cardiac conditions. Although CR referral rates for STEMI patients have improved, rates for heart failure have remained low. Many of these patients are admitted to the cardiac intensive care unit (CICU). However, it is unknown how often CICU survivors qualify for cardiac rehabilitation, how often they are referred, and why eligible patients are not referred. This is a retrospective single-center study of 417 consecutive patients admitted to CICU for >48 hours from March 30, 2016 to March 30, 2017. We excluded patients with in-hospital mortality or those discharged AMA, to hospice or transferred. Chart abstraction was used to determine CR indications based on known American College of Cardiology/American Heart Association guidelines. If CR was indicated, medical records through September 2017 were reviewed to determine both referral and participation rates. In the absence of a referral, medical records were reviewed for potential barriers. A total of 296 CICU survivors were identified upon discharge with 185 (63%) having guideline-directed indications for CR referral. The most common indications were heart failure with reduced ejection fraction (HFrEF, 38%), cardiothoracic surgery (26%), and STEMI (23%). Upon discharge, only 30% of patients were referred to CR. The referral rate increased by 33% to 63% by 18 months postdischarge. CR referrals were most frequently placed following STEMI (91%), NSTEMI (80%), and postpercutaneous coronary intervention (80%). Only 35% of HFrEF discharges were referred to CR. Of patients not referred to CR, no explanation for a lack of referral was documented 87% of the time. In conclusion, nearly 2 of 3 patients discharged from the CICU had CR indications, most commonly HFrEF. CR referrals are frequently not placed and reason for nonreferral is rarely documented. CICU admission may provide a defined event to prompt referral.