Canadian Cardiovascular Society/Canadian Cardiovascular Critical Care Society/Canadian Association of Interventional Cardiology Clinical Practice Update on Optimal Post Cardiac Arrest and Refractory Cardiac Arrest Patient Care.

Survival to hospital discharge among patients with out-of-hospital cardiac arrest (OHCA) is low and important regional differences in treatment practices and survival have been described. Since the 2017 publication of the Canadian Cardiovascular Society's position statement on OHCA care, multiple randomized controlled trials have helped to better define optimal post cardiac arrest care. This working group provides updated guidance on the timing of cardiac catheterization in patients with ST-elevation and without ST-segment elevation, on a revised temperature control strategy targeting normothermia instead of hypothermia, blood pressure, oxygenation, and ventilation parameters, and on the treatment of rhythmic and periodic electroencephalography patterns in patients with a resuscitated OHCA. In addition, prehospital trials have helped craft new expert opinions on antiarrhythmic strategies (amiodarone or lidocaine) and outline the potential role for double sequential defibrillation in patients with refractory cardiac arrest when equipment and training is available. Finally, we advocate for regionalized OHCA care systems with admissions to a hospital capable of integrating their post OHCA care with comprehensive on-site cardiovascular services and provide guidance on the potential role of extracorporeal cardiopulmonary resuscitation in patients with refractory cardiac arrest. We believe that knowledge translation through national harmonization and adoption of contemporary best practices has the potential to improve survival and functional outcomes in the OHCA population.

The management of heart failure cardiogenic shock: an international RAND appropriateness panel.

BACKGROUND: Observational data suggest that the subset of patients with heart failure related CS (HF-CS) now predominate critical care admissions for CS. There are no dedicated HF-CS randomised control trials completed to date which reliably inform clinical practice or clinical guidelines. We sought to identify aspects of HF-CS care where both consensus and uncertainty may exist to guide clinical practice and future clinical trial design, with a specific focus on HF-CS due to acute decompensated chronic HF. METHODS: A 16-person multi-disciplinary panel comprising of international experts was assembled. A modified RAND/University of California, Los Angeles, appropriateness methodology was used. A survey comprising of 34 statements was completed. Participants anonymously rated the appropriateness of each statement on a scale of 1 to 9 (1-3 as inappropriate, 4-6 as uncertain and as 7-9 appropriate). RESULTS: Of the 34 statements, 20 were rated as appropriate and 14 were rated as inappropriate. Uncertainty existed across all three domains: the initial assessment and management of HF-CS; escalation to temporary Mechanical Circulatory Support (tMCS); and weaning from tMCS in HF-CS. Significant disagreement between experts (deemed present when the disagreement index exceeded 1) was only identified when deliberating the utility of thoracic ultrasound in the immediate management of HF-CS. CONCLUSION: This study has highlighted several areas of practice where large-scale prospective registries and clinical trials in the HF-CS population are urgently needed to reliably inform clinical practice and the synthesis of future societal HF-CS guidelines.

Implications of High Sensitivity Troponin Levels After Lung Transplantation.

Trends in high-sensitivity cardiac troponin I (hs-cTnI) after lung transplant (LT) and its clinical value are not well stablished. This study aimed to determine kinetics of hs-cTnI after LT, factors impacting hs-cTnI and clinical outcomes. LT recipients from 2015 to 2017 at Toronto General Hospital were included. Hs-cTnI levels were collected at 0-24 h, 24-48 h and 48-72 h after LT. The primary outcome was invasive mechanical ventilation (IMV) >3 days. 206 patients received a LT (median age 58, 35.4% women; 79.6% double LT). All patients but one fulfilled the criteria for postoperative myocardial infarction (median peak hs-cTnI = 4,820 ng/mL). Peak hs-cTnI correlated with right ventricular dysfunction, >1 red blood cell transfusions, bilateral LT, use of EVLP, kidney function at admission and time on CPB or VA-ECMO. IMV>3 days occurred in 91 (44.2%) patients, and peak hs-cTnI was higher in these patients (3,823 vs. 6,429 ng/mL, p < 0.001 after adjustment). Peak hs-cTnI was higher among patients with had atrial arrhythmias or died during admission. No patients underwent revascularization. In summary, peak hs-TnI is determined by recipient comorbidities and perioperative factors, and not by coronary artery disease. Hs-cTnI captures patients at higher risk for prolonged IMV, atrial arrhythmias and in-hospital death.

Myocarditis and Pericarditis Following mRNA COVID-19 Vaccination: 2024 Status and Management Update.

In 2021, the Canadian Journal of Cardiology published a "Practical Clinical Practice Update" to address emerging concerns about myocarditis and pericarditis following mRNA COVID-19 vaccines.1 Since publication, researchers have underscored the importance of standardizing diagnostic criteria and evaluation of incident cases. In this brief review, we summarize new evidence about the epidemiology and outcomes of patients with mRNA COVID-19 post-vaccine myocarditis and pericarditis. We also provide consensus guidance for evaluation, management, and follow-up. Finally, we identify persistent knowledge gaps that inform the National Active Surveillance Study of Myocarditis and/or Pericarditis following mRNA COVID-19 Vaccination (MYCOVACC) and areas for future research.

Interhospital Variation in Admissions Managed With Critical Care Therapies or Invasive Hemodynamic Monitoring in Tertiary Cardiac Intensive Care Units: An Analysis From the Critical Care Cardiology Trials Network Registry.

BACKGROUND: Wide interhospital variations exist in cardiovascular intensive care unit (CICU) admission practices and the use of critical care restricted therapies (CCRx), but little is known about the differences in patient acuity, CCRx utilization, and the associated outcomes within tertiary centers. METHODS: The Critical Care Cardiology Trials Network is a multicenter registry of tertiary and academic CICUs in the United States and Canada that captured consecutive admissions in 2-month periods between 2017 and 2022. This analysis included 17 843 admissions across 34 sites and compared interhospital tertiles of CCRx (eg, mechanical ventilation, mechanical circulatory support, continuous renal replacement therapy) utilization and its adjusted association with in-hospital survival using logistic regression. The Pratt index was used to quantify patient-related and institutional factors associated with CCRx variability. RESULTS: The median age of the study population was 66 (56-77) years and 37% were female. CCRx was provided to 62.2% (interhospital range of 21.3%-87.1%) of CICU patients. Admissions to CICUs with the highest tertile of CCRx utilization had a greater burden of comorbidities, had more diagnoses of ST-elevation myocardial infarction, cardiac arrest, or cardiogenic shock, and had higher Sequential Organ Failure Assessment scores. The unadjusted in-hospital mortality (median, 12.7%) was 9.6%, 11.1%, and 18.7% in low, intermediate, and high CCRx tertiles, respectively. No clinically meaningful differences in adjusted mortality were observed across tertiles when admissions were stratified by the provision of CCRx. Baseline patient-level variables and institutional differences accounted for 80% and 5.3% of the observed CCRx variability, respectively. CONCLUSIONS: In a large registry of tertiary and academic CICUs, there was a >4-fold interhospital variation in the provision of CCRx that was primarily driven by differences in patient acuity compared with institutional differences. No differences were observed in adjusted mortality between low, intermediate, and high CCRx utilization sites.

Pulmonary Artery Catheter Usage and Impact on Mortality in Patients With Cardiogenic Shock: Results From a Canadian Single-Centre Registry.

BACKGROUND: Hemodynamic assessment for cardiogenic shock (CS) phenotyping in patients has led to renewed interest in the use of pulmonary artery catheters (PACs). METHODS: We included patients admitted with CS from January 2014 to December 2020 and compared clinical outcomes among patients who received PACs and those who did not. The primary outcome was the rate of in-hospital mortality. Secondary outcomes included use of advanced heart failure therapies and coronary intensive care unit (CICU) and hospital lengths of stay. RESULTS: A total of 1043 patients were analysed and 47% received PACs. Patients selected for PAC-guided management were younger and had lower left ventricular function. They also had higher use of vasopressor and inotropes, and 15.2% of them were already supported with temporary mechanical circulatory support (MCS). In-hospital mortality was lower in patients who received PACs (29.3% vs 36.2%; P = 0.02), mainly driven by a reduction in mortality among those in Society for Cardiovascular Angiography and Interventions (SCAI) stages D and E CS. Patients who received PACs were more likely to receive temporary MCS with Impella, durable ventricular assist devices (VADs), or orthotopic heart transplantation (OHT) (P < 0.001 for all analyses). CICU and hospital lengths of stay were longer in patients who used PACs. CONCLUSIONS: Among patients with CS, the use of PACs was associated with lower in-hospital mortality, especially among those in SCAI stages D and E. Patients who received PACs were also more frequently rescued with temporary MCS or received advanced heart failure therapies, such as durable VADs or OHT.

Value of Invasive Hemodynamic Assessments in Patients Supported by Continuous-Flow Left Ventricular Assist Devices.

Left ventricular assist devices (LVADs) are increasingly used in patients with end-stage heart failure (HF). There is a significant risk of HF admissions and hemocompatibility-related adverse events that can be minimized by optimizing the LVAD support. Invasive hemodynamic assessment, which is currently underutilized, allows personalization of care for patients with LVAD, and may decrease the need for recurrent hospitalizations. It also aids in triaging patients with persistent low-flow alarms, evaluating reversal of pulmonary vasculature remodeling, and assessing right ventricular function. In addition, it can assist in determining the precipitant for residual HF symptoms and physical limitation during exercise and is the cornerstone of the assessment of myocardial recovery. This review provides a comprehensive approach to the use of invasive hemodynamic assessments in patients supported with LVADs.

Chronic Ventricular Septal Defect and Retained Bullet After Gunshot: Best Not to Reopen Old Wounds.

Penetrating cardiac trauma from gunshots is usually fatal. We describe the case of a 62-year-old male presenting with ST-segment elevation myocardial infarction. A retained bullet embedded into the left ventricle was identified incidentally along with a ventricular septal defect from a gunshot wound decades prior. The ventricular septal defect and retained bullet were managed conservatively. (Level of Difficulty: Intermediate.).

Improved mortality and haemodynamics with milrinone in cardiogenic shock due to acute decompensated heart failure.

AIMS: Studies in cardiogenic shock (CS) often have a heterogeneous population of patients, including those with acute myocardial infarction and acute decompensated heart failure (ADHF-CS). The therapeutic profile of milrinone may benefit patients with ADHF-CS. We compared the outcomes and haemodynamic trends in ADHF-CS receiving either milrinone or dobutamine. METHODS AND RESULTS: Patients presenting with ADHF-CS (from 2014 to 2020) treated with a single inodilator (milrinone or dobutamine) were included in this study. Clinical characteristics, outcomes, and haemodynamic parameters were collected. The primary endpoint was 30 day mortality, with censoring at the time of transplant or left ventricular assist device implantation. A total of 573 patients were included, of which 366 (63.9%) received milrinone and 207 (36.1%) received dobutamine. Patients receiving milrinone were younger, had better kidney function, and lower lactate at admission. In addition, patients receiving milrinone received mechanical ventilation or vasopressors less frequently, whereas a pulmonary artery catheter was more frequently used. Milrinone use was associated with a lower adjusted risk of 30 day mortality (hazard ratio = 0.52, 95% confidence interval 0.35-0.77). After propensity-matching, the use of milrinone remained associated with a lower mortality (hazard ratio = 0.51, 95% confidence interval 0.27-0.96). These findings were associated with improved pulmonary artery compliance, stroke volume, and right ventricular stroke work index. CONCLUSIONS: The use of milrinone compared with dobutamine in patients with ADHF-CS is associated with lower 30 day mortality and improved haemodynamics. These findings warrant further study in future randomized controlled trials.

Neuroprognostication in the Post Cardiac Arrest Patient: A Canadian Cardiovascular Society Position Statement.

Cardiac arrest (CA) is associated with a low rate of survival with favourable neurologic recovery. The most common mechanism of death after successful resuscitation from CA is withdrawal of life-sustaining measures on the basis of perceived poor neurologic prognosis due to underlying hypoxic-ischemic brain injury. Neuroprognostication is an important component of the care pathway for CA patients admitted to hospital but is complex, challenging, and often guided by limited evidence. Using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system to evaluate the evidence underlying factors or diagnostic modalities available to determine prognosis, recommendations were generated in the following domains: (1) circumstances immediately after CA; (2) focused neurologic exam; (3) myoclonus and seizures; (4) serum biomarkers; (5) neuroimaging; (6) neurophysiologic testing; and (7) multimodal neuroprognostication. This position statement aims to serve as a practical guide to enhance in-hospital care of CA patients and emphasizes the adoption of a systematic, multimodal approach to neuroprognostication. It also highlights evidence gaps.

Vascular Complications With Intra-aortic Balloon Pump (IABP): Experience From a Large Canadian Metropolitan Centre.

Background: Intra-aortic balloon pump (IABP) insertion in critically ill patients has been associated with both vascular and nonvascular complications, which have restricted its use. The primary objective for this study was to determine the frequency and predictors of vascular complication in our centre. Methods: We conducted a retrospective cohort study of consecutive patients treated with an IABP between January 2014 and June 2018. Baseline clinical characteristics, cannulation details, duration of treatment and management, overall mortality, and complications were extracted from electronic and paper medical records. Results: A total of 187 patients required an IABP; of these, 146 were male (78.1%), the average age was 65.2 ± 11.5 years, and body mass index was 26.8 ± 6.2 kg/m2. A majority of the patients had an IABP inserted in either the cardiac catheterization laboratory (54.5%) or an outside hospital (26.7%). The main indications for insertion were acute decompensated heart failure-cardiogenic shock (58.3%), followed by acute myocardial infarction and cardiogenic shock (26.2%). From the documented cannulation site, the right femoral artery was cannulated in 61.6% of patients, with a median size of 7.5 Fr (range: 5 -12 Fr). Mortality for in-hospital, 30-day, and 1-year mortality was calculated at 37.4%, 40.6%, and 41.7%, respectively. Limb ischemia (3.2%), bleeding (1.6%), mesenteric ischemia (0.5%), compartment syndrome (0.5%), and fasciotomy (0.5%), were rare occurrences. No records indicated amputation, aortoiliac dissection, thrombectomy, or infection at the site of insertion. Conclusions: This single-centre retrospective study demonstrated that more than one third of this patient population died secondary to their primary diagnosis. The incidence of vascular complications secondary to IABP insertion remained low, with less than 3% developing an ischemic limb.

Contexte: L'insertion d'un ballon de contrepulsion intra-aortique (BCPIA) chez les patients dont l'état est critique est associée à des complications à la fois vasculaires et non vasculaires, ce qui limite son utilisation. L'objectif principal de cette étude était de déterminer la fréquence des complications vasculaires dans notre centre ainsi que les facteurs prédictifs de ces complications. Méthodologie: Nous avons mené une étude de cohorte rétrospective auprès de patients traités consécutivement par BCPIA entre janvier 2014 et juin 2018. Les caractéristiques cliniques initiales, les détails sur la canulation, la durée du traitement et de la prise en charge, la mortalité globale et les complications ont été extraits des dossiers médicaux électroniques et en format papier. Résultats: Au total, un BCPIA a été nécessaire chez 187 patients; 146 d'entre eux étaient des hommes (78,1 %), l'âge moyen était de 65,2 ± 11,5 ans, et l'indice de masse corporelle moyen était de 26,8 ± 6,2 kg/m2. La majorité des insertions de BCPIA s'étaient déroulées soit dans le laboratoire de cathétérisme (54,5 %) ou dans un hôpital externe (26,7 %). Les principales indications pour lesquelles ces insertions ont été effectuées étaient l'insuffisance cardiaque aiguë décompensée avec choc cardiogénique (58,3 %), suivie de l'infarctus du myocarde aigu avec choc cardiogénique (26,2 %). Selon les sites de canulation documentés, l'artère fémorale droite avait été canulée chez 61,6 % des patients, avec un calibre médian de 7,5 Fr (de 5 à 12 Fr). Les valeurs de mortalité à l'hôpital, à 30 jours et à un an, ont été établies à 37,4 %, 40,6 % et 41,7 %, respectivement. L'ischémie d'un membre (3,2 %), l'hémorragie (1,6 %), l'ischémie mésentérique (0,5 %), le syndrome des loges (0,5 %) et la fasciotomie (0,5 %) ont été constatés dans quelques rares cas. Aucun dossier n'indiquait d'amputation, de dissection aorto-iliaque, de thrombectomie ou d'infection au point d'insertion. Conclusions: Cette étude de cohorte rétrospective unicentrique a permis de démontrer que plus d'un tiers des patients de la population à l'étude sont décédés des suites de leur diagnostic primaire. L'incidence de complications vasculaires secondaires à l'insertion d'un BCPIA est demeurée faible, avec moins de 3 % des patients présentant une ischémie d'un membre.

Patient Outcomes and Characteristics in a Contemporary Quaternary Canadian Cardiac Intensive Care Unit.

Background: The modern-day cardiac intensive care unit (CICU) has evolved to care for patients with acute critical cardiac illness. We describe the current population of cardiac patients in a quaternary CICU. Methods: Consecutive CICU patients admitted to the CICU at the Toronto General Hospital from 2014 to 2020 were studied. Patient demographics, admission diagnosis, critical care resources, complications, in-hospital mortality, and CICU and hospital length of stay were recorded. Results: A total of 8865 consecutive admissions occurred, with a median age of 64.9 years. The most common primary cardiac diagnoses were acute decompensated heart failure (17.8%), non ST-elevation myocardial infarction (16.8%), ST-elevation myocardial infarction (15.5%), and arrhythmias (14.7%). Cardiogenic shock was seen in 13.2%, and out-of-hospital cardiac arrest in 4.1%. A noncardiovascular admission diagnosis accounted for 13.9% of the cases. Over the period studied, rates of admission were higher for cardiogenic shock (P < 0.001 for trend), with a higher use of critical care resources. Additionally, rates of admission were higher in female patients and those who had chronic kidney disease and diabetes. The in-hospital mortality rate of all CICU admissions was 13.2%, and it was highest in those with noncardiac conditions, compared to the rate in those with cardiac diagnoses (29.4% vs 10.6%, P < 0.001). Conclusions: Given the trends of higher acuity of patients with cardiac critical illness, with higher use of critical care resources, education streams for critical care within cardiology, and alternative pathways of care for patients who have lower-acuity cardiac disease remain imperative to manage this evolving population.

Introduction: L'unité de soins intensifs de cardiologie (USIC) d'aujourd'hui a évolué vers des soins aux patients atteints d'une maladie cardiaque aiguë en phase critique. Nous décrivons la population actuelle de patients cardiaques d'une USIC quaternaires. Méthodes: Les patients consécutifs d'USIC admis à l'USIC de l'Hôpital général de Toronto de 2014 à 2020 ont fait l'objet de l'étude. Les données démographiques des patients, le diagnostic à l'admission, les ressources en soins aux patients en phase critique, les complications, la mortalité intrahospitalière, et la durée de séjour à l'hôpital et à l'USIC ont été enregistrés. Résultats: Il y a eu un total de 8 865 admissions consécutives dont les patients avaient un âge médian de 64,9 ans. Les diagnostics principaux les plus fréquents de maladies cardiaques étaient l'insuffisance cardiaque aiguë décompensée (17,8 %), l'infarctus du myocarde sans élévation du segment ST (16,8 %), l'infarctus du myocarde avec élévation du segment ST (15,5 %) et les arythmies (14,7 %). Le choc cardiogénique a été observé chez 13,2 %, et l'arrêt cardiaque hors de l'hôpital, chez 4,1 %. Un diagnostic d'admission de maladie non cardiovasculaire représente 13,9 % des cas. Durant la période étudiée, les taux d'admission en raison d'un choc cardiogénique étaient plus élevés (P < 0,001 pour la tendance), et entraînaient une utilisation plus élevée de ressources en soins aux patients en phase critique. De plus, les taux d'admission étaient plus élevés chez les patientes, et chez ceux qui avaient une insuffisance rénale chronique et un diabète. Le taux de mortalité intrahospitalière de toutes les admissions à l'USIC était de 13,2 %, et il constituait le taux le plus élevé chez ceux qui avaient des maladies non cardiaques comparativement au taux chez ceux qui avaient des diagnostics de maladies cardiaques (29,4 % vs 10,6 %, P < 0,001). Conclusions: Compte tenu des tendances d'accroissement de la gravité de l'état des patients atteints d'une maladie cardiaque en phase critique et de la plus grande utilisation des ressources en soins aux patients en phase critique, des volets de formation en soins aux patients en phase critique en cardiologie et d'autres protocoles de soins des patients qui ont une maladie cardiaque de plus faible gravité demeurent essentiels à la prise en charge de cette population grandissante.

Clonal hematopoiesis confers an increased mortality risk in orthotopic heart transplant recipients.

Novel risk stratification and non-invasive surveillance methods are needed in orthotopic heart transplant (OHT) to reduce morbidity and mortality post-transplant. Clonal hematopoiesis (CH) refers to the acquisition of specific gene mutations in hematopoietic stem cells linked to enhanced inflammation and worse cardiovascular outcomes. The purpose of this study was to investigate the association between CH and OHT. Blood samples were collected from 127 OHT recipients. Error-corrected sequencing was used to detect CH-associated mutations. We evaluated the association between CH and acute cellular rejection, CMV infection, cardiac allograft vasculopathy (CAV), malignancies, and survival. CH mutations were detected in 26 (20.5%) patients, mostly in DNMT3A, ASXL1, and TET2. Patients with CH showed a higher frequency of CAV grade 2 or 3 (0% vs. 18%, p < .001). Moreover, a higher mortality rate was observed in patients with CH (11 [42%] vs. 15 [15%], p = .008) with an adjusted hazard ratio of 2.9 (95% CI, 1.4-6.3; p = .003). CH was not associated with acute cellular rejection, CMV infection or malignancies. The prevalence of CH in OHT recipients is higher than previously reported for the general population of the same age group, with an associated higher prevalence of CAV and mortality.

Clonal haematopoiesis is associated with higher mortality in patients with cardiogenic shock.

AIMS: Cardiogenic shock (CS) with variable systemic inflammation may be responsible for patient heterogeneity and the exceedingly high mortality rate. Cardiovascular events have been associated with clonal haematopoiesis (CH) where specific gene mutations in haematopoietic stem cells lead to clonal expansion and the development of inflammation. This study aims to assess the prevalence of CH and its association with survival in a population of CS patients in a quaternary centre. METHODS AND RESULTS: We compared the frequency of CH mutations among 341 CS patients and 345 ambulatory heart failure (HF) patients matched for age, sex, ejection fraction, and HF aetiology. The association of CH with survival and levels of circulating inflammatory cytokines was analysed. We detected 266 CH mutations in 149 of 686 (22%) patients. CS patients had a higher prevalence of CH-related mutations than HF patients (odds ratio 1.5; 95% confidence interval [CI] 1.0-2.1, p = 0.02) and was associated with decreased survival (30 days: hazard ratio [HR] 2.7; 95% CI 1.3-5.7, p = 0.006; 90 days: HR 2.2; 95% CI 1.3-3.9, p = 0.003; and 3 years: HR 1.7; 95% CI 1.1-2.8, p = 0.01). TET2 or ASXL1 mutations were associated with lower survival in CS patients at all time-points (p ≤ 0.03). CS patients with TET2 mutations had higher circulating levels of SCD40L, interferon-γ, interleukin-4, and tumour necrosis factor-α (p ≤ 0.04), while those with ASXL1 mutations had decreased levels of CCL7 (p = 0.03). CONCLUSIONS: Cardiogenic shock patients have high frequency of CH, notably mutations in TET2 and ASXL1. This was associated with reduced survival and dysregulation of circulating inflammatory cytokines in those CS patients with CH.

Predicted heart mass for size matching in obese heart transplant donors and recipients.

INTRODUCTION: Predicted heart mass (PHM) was neither derived nor evaluated in an obese population. Our objective was to evaluate size mismatch using actual body weight or ideal body weight (IBW)-adjusted PHM on mortality and risk assessment. METHODS: We conducted a retrospective cohort study of adult recipients with BMI ≥30 kg/m2 or recipients of donors with BMI≥30 kg/m2 from the ISHLT registry. We used multivariable Cox proportional hazard models to evaluate 30-day and 1-year mortality. The two models were compared using net reclassification index. RESULTS: 10,817 HT recipients, age 55 (IQR 46-62) years, 23% female, BMI 31 kg/m2 (IQR 28-33) were included. Donors were age 34 (IQR 24-44) years, 31% female, and BMI 31 kg/m2 (IQR 26-34). There was a significant nonlinear association between mortality and actual PHM but not IBW-adjusted PHM. Undersizing using actual PHM was associated with higher 30-day and 1-year mortality (p < .01), not seen with IBW-adjusted PHM. Actual PHM better risk classified .6% (95% CI .3-.8) patients compared to IBW-adjusted PHM. CONCLUSION: Actual PHM can be used for size matching when assessing mortality risk in obese recipients or recipients of obese donors. There is no advantage to re-calculating PHM using IBW to define candidate risk at the time of organ allocation.