Outcomes of coronary artery bypass surgery using modified del Nido cardioplegia in patients with poor ventricular function.

BACKGROUND: del Nido cardioplegia (DN) has been shown to be safe in adult patients undergoing isolated coronary artery bypass grafting with normal left ventricular ejection fraction. We sought to determine whether it was also safe in adult patients with diminished left ventricular function. METHODS: All patients with preoperative left ventricular ejection fraction ≤ 40% undergoing isolated coronary artery bypass grafting between 1/1/2019 and 7/10/2022 were retrospectively analyzed. Off-pump and beating heart cases were excluded. Patients were divided by surgeon preference between conventional cardioplegia (CCP) and DN. Baseline and intraoperative characteristics and short-term postoperative outcomes were compared. RESULTS: Six surgeons performed 829 isolated coronary artery bypass operations during the study. Two-hundred seventy-two met study criteria. Three surgeons used exclusively CCP for the duration of the study, two used exclusively DN and one switched from CCP to DN mid-way through. Group totals were: CCP n = 181 and DN n = 91. There were no significant differences in baseline characteristics including mean left ventricular ejection fraction (CCP 32.5 ± 7.4% vs. DN 33.4 ± 7.29%, p = 0.939). Other than a significant decrease in bypass time for DN (113.20 ± 37.2 vs. 122.43 ± 34.3 min, p = 0.043) there were no intergroup differences in urgency, number of grafts, ischemic time or incidence of blood transfusion. Postoperative outcomes between CCP and DN were similar including incidence of atrial fibrillation (12.2% vs. 8.8%, p = 0.403), intensive care length of stay (3.7 ± 2.3 vs. 4.3 ± 3.7 days, p = 0.886), total length of stay (5.7 ± 3.7 vs. 6.3 ± 4.4 days, p = 0.922) and 30-day mortality (3.85% vs. 1.10%, p = 0.205). CONCLUSION: Compared to conventional cardioplegia, del Nido cardioplegia provides equivalent short-term outcomes in patients with low left ventricular ejection fraction undergoing isolated coronary artery bypass grafting.

InsP3R-RyR channel crosstalk augments sarcoplasmic reticulum Ca2+ release and arrhythmogenic activity in post-MI pig cardiomyocytes.

Ca2+ transients (CaT) underlying cardiomyocyte (CM) contraction require efficient Ca2+ coupling between sarcolemmal Ca2+ channels and sarcoplasmic reticulum (SR) ryanodine receptor Ca2+ channels (RyR) for their generation; reduced coupling in disease contributes to diminished CaT and arrhythmogenic Ca2+ events. SR Ca2+ release also occurs via inositol 1,4,5-trisphosphate receptors (InsP3R) in CM. While this pathway contributes negligeably to Ca2+ handling in healthy CM, rodent studies support a role in altered Ca2+ dynamics and arrhythmogenic Ca2+ release involving InsP3R crosstalk with RyRs in disease. Whether this mechanism persists in larger mammals with lower T-tubular density and coupling of RyRs is not fully resolved. We have recently shown an arrhythmogenic action of InsP3-induced Ca2+ release (IICR) in end stage human heart failure (HF), often associated with underlying ischemic heart disease (IHD). How IICR contributes to early stages of disease is however not determined but highly relevant. To access this stage, we chose a porcine model of IHD, which shows substantial remodelling of the area adjacent to the infarct. In cells from this region, IICR preferentially augmented Ca2+ release from non-coupled RyR clusters that otherwise showed delayed activation during the CaT. IICR in turn synchronised Ca2+ release during the CaT but also induced arrhythmogenic delayed afterdepolarizations and action potentials. Nanoscale imaging identified co-clustering of InsP3Rs and RyRs, thereby allowing Ca2+-mediated channel crosstalk. Mathematical modelling supported and further delineated this mechanism of enhanced InsP3R-RyRs coupling in MI. Our findings highlight the role of InsP3R-RyR channel crosstalk in Ca2+ release and arrhythmia during post-MI remodelling.

IP3R activity increases propensity of RyR-mediated sparks by elevating dyadic [Ca2＋].

Calcium (Ca2＋) plays a critical role in the excitation contraction coupling (ECC) process that mediates the contraction of cardiomyocytes during each heartbeat. While ryanodine receptors (RyRs) are the primary Ca2＋ channels responsible for generating the cell-wide Ca2＋ transients during ECC, Ca2＋ release, via inositol 1,4,5-trisphosphate (IP3) receptors (IP3Rs) are also reported in cardiomyocytes to elicit ECC-modulating effects. Recent studies suggest that the localization of IP3Rs at dyads grant their ability to modify the occurrence of Ca2＋ sparks (elementary Ca2＋ release events that constitute cell wide Ca2＋ releases associated with ECC) which may underlie their modulatory influence on ECC. Here, we aim to uncover the mechanism by which dyad-localized IP3Rs influence Ca2＋ spark dynamics. To this end, we developed a mathematical model of the dyad that incorporates the behaviour of IP3Rs, in addition to RyRs, to reveal the impact of their activity on local Ca2＋ handling and consequent Ca2＋ spark occurrence and its properties. Consistent with published experimental data, our model predicts that the propensity for Ca2＋ spark formation increases in the presence of IP3R activity. Our simulations support the hypothesis that IP3Rs elevate Ca2＋ in the dyad, sensitizing proximal RyRs towards activation and hence Ca2＋ spark formation. The stochasticity of IP3R gating is an important aspect of this mechanism. However, dyadic IP3R activity lowers the Ca2＋ available in the junctional sarcoplasmic reticulum (JSR) for release, thus resulting in Ca2＋ sparks with similar durations but lower amplitudes.

Current status of perioperative temporary mechanical circulatory support during cardiac surgery.

OBJECTIVES: We sought to determine utilization and outcomes of perioperative temporary mechanical circulatory support (tMCS) in the current practice of cardiac surgery. BACKGROUND: tMCS is an evolving adjunct to cardiac surgery not fully characterized in contemporary practice. METHODS: Using the nationwide inpatient sample we retrospectively analyzed hospital discharge data between January 1, 2016 and December 31, 2019. ICD-10-CM procedure codes were used to identify and divide patient hospitalizations into those who had preoperative tMCS (pre-tMCS) versus tMCS instituted the day of surgery or afterwards (sd/post-tMCS). RESULTS: In all, 1,383,520 hospitalizations met inclusion criteria. 86,445 (6.25%) had tMCS. tMCS was utilized in 8.74% of coronary artery bypass grafting (CABG), 2.58% of isolated valve, and 9.71% of valve/CABG; operations. 29,325 (33.9%) had pre-tMCS while 57,120 (66.1%) had sd/post-tMCS. The use of tMCS was associated with greater inpatient mortality (15.66% vs. 1.53%, p < .001), longer length of stay (LOS) (14.4 vs. 8.5 days, p < .001), and higher mean inflation-adjusted costs ($93,040 ± 1038 vs. $51,358 ± 296, p < .001) compared to no use. Inpatient mortality (5.98% vs. 20.63%, p < .001), LOS (13.87 vs. 14.68, p < .001), and cost ($82,621 ± 1152 SEM vs. $98,381 ± 1242) were all significantly lower with pre-tMCS compared to sd/post tMCS. When analyzed separately, mortality was higher with later utilization of tMCS (5.98% pre, 17.1% sd, and 49.05% postsurgical date insertion, p < .001). CONCLUSIONS: Perioperative tMCS is utilized in 6.25% of modern cardiac surgery, with two-thirds of cases instituted on the day of surgery or afterwards. The use of tMCS is associated with significantly higher mortality, longer LOS, and higher costs. Among patients undergoing tMCS, earlier utilization is associated with better outcomes.

The Cell Physiome: What Do We Need in a Computational Physiology Framework for Predicting Single-Cell Biology?

Modern biology and biomedicine are undergoing a big data explosion, needing advanced computational algorithms to extract mechanistic insights on the physiological state of living cells. We present the motivation for the Cell Physiome Project: a framework and approach for creating, sharing, and using biophysics-based computational models of single-cell physiology. Using examples in calcium signaling, bioenergetics, and endosomal trafficking, we highlight the need for spatially detailed, biophysics-based computational models to uncover new mechanisms underlying cell biology. We review progress and challenges to date toward creating cell physiome models. We then introduce bond graphs as an efficient way to create cell physiome models that integrate chemical, mechanical, electromagnetic, and thermal processes while maintaining mass and energy balance. Bond graphs enhance modularization and reusability of computational models of cells at scale. We conclude with a look forward at steps that will help fully realize this exciting new field of mechanistic biomedical data science.

Combined coronary artery bypass graft and liver/kidney transplantation in a liver failure patient with acute on chronic kidney failure and antiphospholipid syndrome.

Coexisting coronary artery disease (CAD), end-stage liver disease (ESLD), renal failure, and hypercoagulable state poses a formidable clinical challenge. Here, we discuss the first known case of a patient with antiphospholipid syndrome (APLS), ESLD complicated by hepatorenal syndrome (HRS), and severe CAD who successfully underwent combined coronary artery bypass grafting (CABG) and simultaneous liver/kidney (SLK) transplant.

The effect of recipient BMI on waitlist and post-transplant outcomes after the 2018 heart transplant allocation policy change.

OBJECTIVE: The effects of recipient body mass index (BMI) on waitlist strategies, waitlist outcomes, and post-transplant outcomes among adult patients listed for heart transplantation under the updated 2018 allocation system have not been well characterized. METHODS: The United Network of Organ Sharing data set between October 2015 and March 2021 was analyzed, and patients were grouped based on recipient BMI and whether listing occurred in the old (pre-October 2018) or new allocation system. RESULTS: Listing strategies differed by BMI group, but trends of increased use of temporary mechanical support and decreased use of durable support remained among all BMI groups, except those with BMI > 35 kg/m2 . Waitlist outcomes improved among all BMI cohorts in the new allocation system, including among patients with BMI 30-34.9 and >35 kg/m2 , although patients with higher BMIs continued to have longer waitlist times. Post-transplant outcomes in the new allocation system are worse for patients with BMI > 30 kg/m2  (hazard ratio: 1.47; confidence interval: 1.19-1.82; p < .001). CONCLUSIONS: The 2018 change to the heart transplant allocation system was associated with similar changes in the use of mechanical support for listing strategy across BMI ranges, except in the most obese, and improved waitlist outcomes across all BMI ranges. Post-transplant outcomes in the new allocation system are worse for patients with BMI > 30 kg/m2  compared to patients with BMI < 30 kg/m2 . These findings have important clinical implications for our understanding of the ongoing influence of BMI on waitlist courses and post-transplant outcomes among patients listed for heart transplantation.

Hemorrhagic pericardial effusion resulting in constriction in hereditary hemorrhagic telangiectasia.

BACKGROUND: We report the first ante-mortem diagnosis of hemorrhagic pericardial effusion in hereditary hemorrhagic telangiectasia resulting in constriction; the case also demonstrates the unusual but well-described complication of right-sided heart failure requiring extracorporeal membrane oxygenation (ECMO) support after pericardiectomy. CASE PRESENTATION: A previously healthy 48 year old man with a strong family history of Osler-Weber-Rendu disease presented to our institution with signs and symptoms of advance heart failure. His workup demonstrated a thickened pericardium and constrictive physiology. He was brought to the operating room where old clot and inflamed tissue were appreciated in the pericardial space and he underwent complete pericardiectomy under cardiopulmonary bypass. Separation from bypass, hampered by the development of right ventricular dysfunction and profound vasoplegia, required significant pressor and inotropic support. The right heart dysfunction and vasoplegia worsened in the early postoperative period requiring a week of ECMO after which his right ventricle recovered and he was successfully de-cannulated. CONCLUSION: Given the poor outcome of severe postoperative right ventricular failure after pericardiectomy, with high central venous pressure, a low gradient between central venous and pulmonary artery pressures and high vasopressor requirements, ECMO should be instituted promptly.

The heart transplant allocation change attenuates but does not eliminate blood group O waitlist outcome disadvantage.

BACKGROUND: Patients with blood group O have historically been disadvantaged in the United Network for Organ Sharing (UNOS) heart transplant allocation system. We sought to determine whether the new UNOS allocation system implemented in 2018 had an impact on waitlist and post-transplant outcomes among blood groups. METHODS: Using the UNOS database we included all adult patients listed and transplanted with first-time single-organ heart transplant between 10/17/15 and 10/1/21. For post-transplant outcomes, we separately evaluated all adult patients transplanted with the same time-frame. We used exclusion criteria and censoring to limit biases from changing clinical practices around the allocation change (10/18/2018), and from unequal or inadequate follow-up. We compared clinical characteristics and outcomes before and after the allocation change among each blood group. Fine-Gray and Cox regression models were used to estimate the effect of the new allocation system on competing waitlist outcomes- transplantation, death-or-removal from waitlist- and post-transplant survival, respectively. RESULTS: Of the 21,565 patients listed for transplantation 14,000 met criteria for waitlist analysis (7,035 in the old system vs. 6,965 in the new), and 7,657 met criteria for post-transplant analysis (3,519 in the old system vs. 4,138 in the new). Among each blood group, new allocation change was associated with higher transplantation rates lower waitlist days and lower waitlist mortality (except Group AB). However, despite improvements, Group O was still associated with worse waitlist outcomes for each metric compared to non-O Groups. The new allocation system did not have a significant impact on post-transplant survival among any blood groups. CONCLUSION: Changes in heart transplant allocation have attenuated but not eliminated blood group O disadvantage in access to donor hearts.

Impact of transplant center volume on donor heart offer utilization rates in the United States.

BACKGROUND: We tested the hypothesis that transplant centers (TCs) with higher volumes have higher donor heart (DH) offer utilization rates. METHODS: Using the Annual Data reports of the US Organ Procurement and Transplantation Network and the Scientific Registry of Transplant Recipients (SRTR) we reviewed all adult heart transplant offers between July 1, 2016 and June 29, 2019. Unadjusted donor offer utilization rates and observed to expected (O/E) DH utilization ratios adjusted using the SRTR model were calculated for each TC for all DH offers and for the following sub-categories: DH with left ventricular ejection fraction <60%, DH >40 years, DH >500 miles from TC, "hard-to-place hearts" (defined as those offered to >50 TCs) and DH designated as increased infectious risk. Univariable linear regression was used to identify a relationship between average yearly center volume and DH utilization. RESULTS: During the study 118,841 total offers were made to 107 TCs and 8300 transplants were performed. The unadjusted utilization rate was not associated with TC volume for all donor offers (p = .517). However, among all subcategories other than DH >40 years, the unadjusted DH utilization rate was associated with TC volume (p < .05). In addition, using the adjusted SRTR O/E ratio, there was a significant impact of TC volume on utilization rate for all donor offers (for an increase TC volume of 10 transplants/year coefficient = 0.095, 95% confidence interval: 0.037-0.151, p = .001). This relationship persisted with an identifiable change for each of the subcategories (p ≤ .001). CONCLUSIONS: TC volume is significantly correlated to DH offer utilization rate.

Impact of heart transplant allocation change on competing waitlist outcomes among listing strategies.

In 2018, the United Network for Organ Sharing (UNOS) adopted a 6-tier system for heart allocation which shifted patterns in listing strategies. The effects of the change on waitlist survival and transplantation rates have yet to be substantiated by analysis of competing outcomes among various listing strategies. This study included all adult patients listed for first-time heart transplantation in UNOS between 10/17/15 and 6/12/20. Clinical characteristics were compared before and after allocation change among various listing strategies: no support, inotropes, intra-aortic balloon pump, durable left ventricular assist device (LVAD), temporary VAD, and extracorporeal membrane oxygenation. Fine-Gray proportional subhazard models were used to estimate the effect of allocation change on competing waitlist outcomes-transplantation, death, or removal from waitlist-among each strategy. During the study period, there were 17 422 patients listed for heart transplantation. Among each listing strategy, clinical characteristics were similar before and after allocation change. Subhazard models demonstrated reduced risk for waitlist mortality (p < .001) among each strategy except temporary VAD and increased transplantation rates (p < .001) among each strategy except for durable LVAD. These results validate the association of the new allocation system on waitlist outcomes across listing strategies.

Incidence and predictors of postoperative ischemic stroke after coronary artery bypass grafting.

BACKGROUND: Data on the incidence and outcomes of ischemic stroke in patients undergoing coronary artery bypass grafting (CABG) in the current era are limited. The goal of this study was to examine contemporary trends, predictors, and outcomes of ischemic stroke following CABG in a large nationally representative database over a 12-year-period. METHODS: The National Inpatient Sample was used to identify all adult (≥18 years) patients who underwent CABG between 2004 and 2015. The incidence and predictors of post-CABG ischemic stroke were assessed and in-hospital outcomes of patients with and without post-CABG stroke were compared. RESULTS: Out of 2 569 597 CABG operations, ischemic stroke occurred in 47 279 (1.8%) patients, with a rising incidence from 2004 (1.2%) to 2015 (2.3%) (P < .001). Patient risk profiles increased over time in both cohorts, with higher Charlson comorbidity scores observed amongst stroke patients. Stroke was independently associated with higher rates of in-hospital mortality (3-fold), longer lengths of hospital stay (~6 more days), and higher total hospitalisation cost (~$80 000 more). Age ≥60 years and female sex (OR 1.33, 95% CI 1.31-1.36) were the strongest predictors of stroke (both P < .001). Further, on-pump CABG was not an independent predictor of stroke (P = .784). CONCLUSION: In this nationally representative study we have shown that the rates of postoperative stroke complications following CABG have increased over time to commensurate with a parallel increase in overall baseline patient risks. Given the adverse impact of stroke on in-hospital morbidity and mortality after CABG, further studies are warranted to systematically delineate factors contributing to this striking trend.

Total artificial heart: surgical technique in the patient with normal cardiac anatomy.

Heart failure is a complex, growing problem with significant morbidity and mortality. Though heart transplantation remains the gold standard treatment for end-stage heart failure, there remains a national shortage of donor hearts. Mechanical circulatory support has provided an additional option for clinicians to support patients for the purposes of bridging patients to transplantation or to be used for destination therapy purposes. Despite generally favorable outcomes with univentricular support, in a subset of patients with biventricular heart failure, an isolated left ventricular assist device is not sufficient. Right ventricular failure has a negative impact on patient survival if not identified and treated promptly. The Total Artificial Heart (TAH) is the only Food and Drug Administration (FDA) approved artificial heart used for bridging patients to transplantation. Outcomes in patients who undergo implantation of the TAH at experienced centers have been good and reproducible.

A New Paradigm in Mechanical Circulatory Support: 100-Patient Experience.

BACKGROUND: Acutely decompensated heart failure presents a complicated challenge. Established temporary support measures have significant adverse effects. A minimally invasive temporary left ventricular assist device (LVAD), the Impella 5.0 (Abiomed, Danvers, MA), has been developed to support these patients. METHODS: Patients with acutely decompensated heart failure in whom medical management had failed and who required additional support using an Impella 5.0 device were evaluated from January 2014 to September 2018 at a single center in a retrospective manner using a prospectively maintained database. Patients were treated with the device as a bridge to recovery (BTR; n = 30), bridge to durable device (BTDD; n = 23), or bridge to transplantation (BTT; n = 47). All devices were placed using an axillary artery approach. Demographic features and outcomes were evaluated for each group and compared. RESULTS: A total of 100 patients underwent insertion of an axillary Impella 5.0 LVAD. Patients had an average age of 56.7 ± 13.2 years, were predominantly male (84%), and had a severely depressed left ventricular ejection fraction (average 16%), and most had an Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) profile 1 (57%) or 2 (33%) score. When divided into groups, there was no difference in age or INTERMACS score, but a statistical difference was noted in baseline left ventricular ejection fraction (20%, 14%, 15%) and creatinine level (1.0, 2.0, 1.6), in the BTR, BTDD, or BTT group, respectively (all P < .05). Survival was 64% overall, and it was 50%, 48%, and 81% for BTR, BTDD, and BTT, respectively (P = .007). Survival improved during this experience and was 90% overall in the most recent 30 patients. CONCLUSIONS: Use of this minimally invasive LVAD system is an attractive strategy to support patients with acute decompensated heart failure to recovery, durable LVAD, or heart transplantation.

Mechanical circulatory support for cardiac amyloidosis.

BACKGROUND: Cardiac amyloidosis, typically from abnormal deposition of AL or ATTR amyloid protein, can result in heart failure requiring transplantation (HTx). The role of mechanical circulatory support (MCS) is not well-established. The purpose of this study was to present our experience with MCS in patients with cardiac amyloidosis. METHODS: Consecutive patients with cardiac amyloidosis who received MCS at Cedars-Sinai Medical Center between 2010 and 2018 were reviewed. Clinical characteristics and outcomes were compared to a control group of MCS patients without amyloid matched 2:1 for age and INTERMACS Profile. RESULTS: 11 amyloid patients underwent durable MCS, two with paracorporeal biventricular assist devices and 9 with total artificial hearts. No patients received isolated left ventricular assist device support. By 1 year, 9 (82%) of patients in the MCS-Amyloid group had been transplanted and 2 (18%) had died. In the MCS-No Amyloid group, by 1 year, 8 (36%) of patients had been transplanted, 10 (46%) had died, and 4 (18%) were still living with MCS. CONCLUSIONS: Over a 9-year period, patients with amyloid cardiomyopathy who required MCS at our institution all received durable biventricular MCS. For carefully selected patients, this approach is feasible with acceptable outcomes as bridge to transplantation.

Combined Heart and Kidney Transplantation: Clinical Experience in 100 Consecutive Patients.

Background Combined heart and kidney transplantation ( HKT x) is performed in patients with severe heart failure and advanced renal insufficiency. We analyzed the long-term survival after HKT x, the influence of age and dialysis status, the rates of cardiac rejection, and the influence of sensitization. Methods and Results From June 1992 to December 2016, we performed 100 HKT x procedures. We compared older (≥60 years, n=53) with younger (<60 years, n=47) recipients, and recipients on preoperative dialysis (n=49) and not on dialysis (n=51). We analyzed actuarial freedom from any cardiac rejection, acute cellular rejection, and antibody-mediated rejection, and survival rates by sensitized status with panel-reactive antibody levels <10%, 10% to 50%, and >50%, and compared these survival rates with those from the United Network for Organ Sharing database. There was no difference in 15-year survival between the 2 age groups (35±12.4% and 49±17.3%, ≥60 versus <60 years; P=0.45). There was no difference in 15-year survival between the dialysis and nondialysis groups (44±13.4% and 37±15.2%, P=0.95). Actuarial freedom from any cardiac rejection ( acute cellular rejection >0 or antibody-mediated rejection >0) was 92±2.8% and 84±3.8%, acute cellular rejection (≥2R/3A) 98±1.5% and 94±2.5%, and antibody-mediated rejection (≥1) 96±2.1% and 93±2.6% at 30 days and 1 year after HKT x. There was no difference in the 5-year survival among recipients by sensitization status with panel-reactive antibody levels <10%, 10% to 50%, and >50% (82±5.9%, 83±10.8%, and 92±8.0%; P=0.55). There was no difference in 15-year survival after HKT x between the United Network for Organ Sharing database and our center (38±3.2% and 40±10.1%, respectively; P=0.45). Conclusions HKT x is safe to perform in patients 60 years and older or younger than 60 years and with or without dialysis dependence, with excellent outcomes. The degree of panel-reactive antibody sensitization did not appear to affect survival after HKT x.

Extracorporeal Membrane Oxygenation Appropriateness: An Interdisciplinary Consensus-Based Approach.

We describe a quality improvement initiative aimed at achieving interdisciplinary consensus about the appropriate delivery of extracorporeal membrane oxygenation (ECMO). Interdisciplinary rounds were implemented for all patients on ECMO and addressed whether care was consistent with a patient's minimally acceptable outcome, maximally acceptable burden, and relative likelihood of achieving either. The rounding process was associated with decreased days on venoarterial ECMO, from a median of 6 days in 2014 (first quartile [Q1]-third quartile [Q3], 3-10) to 5 days in 2015 (Q1-Q3, 2.5-8) and in 2016 (Q1-Q3, 1-8). Our statistical methods do not allow us to conclude that this change was due to our intervention, and it is possible that the observed decreases would have occurred whether or not the rounding process was implemented.

Predicted heart mass is the optimal metric for size match in heart transplantation.

BACKGROUND: Donor-recipient size match is traditionally assessed by body weight. We assessed the ability of 5 size match metrics-predicted heart mass (PHM), weight, height, body mass index (BMI) and body surface area (BSA)-to predict 1-year mortality after heart transplant and to assess the effect of size match on donor heart turn down for size. METHODS: The study cohort comprised 19,168 adult heart transplant recipients in the United Network for Organ Sharing registry between 2007 and 2016. Each size match metric was divided into 7 equally sized groups using the donor-recipient ratio for each metric. Single and multivariable Cox proportional hazard models for mortality 1 year after transplant were constructed. RESULTS: Recipients in the severely (donor-recipient PHM ratio 0.54-0.86) undersized group for PHM experienced increased mortality, with a hazard ratio of 1.34 (95% confidence interval, 1.13-1.59; p < 0.001). There was no increased risk of death at 1 year if donors were undersized for weight, height, BMI, or BSA. We found that 32% of heart offers turned down for donor size would be acceptable using a PHM threshold of 0.86 or greater and that 14% of offers accepted (most of which are female donor to male recipient) were below this threshold. CONCLUSIONS: PHM is the optimal donor-recipient size match metric for prediction of mortality after heart transplant. Many offers turned down for donor size were above the threshold for adequacy of size match by PHM identified, and thus, the use of PHM could improve donor heart utilization and post-transplant survival.