Pectoral Mass Research Articles

Heart Failure Severity Stratification Beyond INTERMACS Profiles: A Step Toward Optimal Left Ventricular Assist Device Timing.

The purpose of this analysis is to determine whether pectoralis muscle measures quantified on pre left ventricular assist device (LVAD) computerized tomography (CT) scans can identify subgroups of patients with differential disease severity within each Interagency Registry for Mechanical Circulatory Support (INTERMACS) profile. Patients with chest CTs performed ≤3 months before LVAD implantation at University of Minnesota (n = 143) and Houston Methodist Hospital (n = 133) were identified from the larger LVAD cohorts (University of Minnesota n = 353, Houston Methodist =278). Unilateral Pectoralis muscle mass indexed to body surface area and pectoralis muscle attenuation were measured on preoperative chest CT scans. Patients within each INTERMACS profile were separated into HIGH and LOW PEC muscle groups. Kaplan-Meier and multivariable cox regression analyses were performed to compare mortality among INTERMACS profiles by HIGH and LOW PEC muscle groups. INTERMACS 3 and 4 patients in the HIGH PEC groups had the highest survival on LVAD support (1 year survival 85% vs. 68%, log rank P = 0.0001). Being in this group was associated with a 60% reduction in the hazards rate (HR) of death after LVAD (adjusted HR 0.40, 95% confidence interval 0.25-0.62). Additionally, renal function deterioration in the year before LVAD was associated with lower INTERMACS profiles and lower measured pectoralis muscle tissue attenuation at the time of LVAD implantation. INTERMACS 3 and 4 patients with the highest pectoralis muscle measures had the best survival after LVAD. The association between renal function deterioration and sarcopenia suggests these muscle changes are progressive. Computerized tomography quantification of sarcopenia may help identify optimal LVAD implantation timing.

Snow buntings preparing for migration increase muscle fiber size and myonuclear domain in parallel with a major gain in fat mass

In long‐distance migrants, preparation for migration is typically associated with increases in fat and body mass, and with an enlargement of pectoralis muscle mass that likely improves flight performance. Although changes in muscle mass or size have been well described in migratory birds, potential changes in muscle ultrastructure during this transition still deserves scrutiny. Using outdoor captive snow buntings (Plectrophenax nivalis n = 15) measured during their transition into a spring migratory phenotype as a model system, we studied changes in pectoralis muscle ultrastructure and predicted that muscle fiber diameter could increase in parallel with the gain in body mass. We also expected that larger fibers could either recruit satellite cells to support cellular maintenance and protein turnover, increase myonuclear domain (cytoplasm per nuclei) with a potential increase in protein turnover load per myonucleus, or existing myonuclei could undergo endoreduplication. Buntings increased body mass by 46% within a month, largely due to a > 6‐fold increase in body fat. However, this increase in body mass was also associated with a 36% increase in muscle fiber diameter. Both pectoralis muscle mass (r2 = 0.57–0.77) and fiber diameter (r2 = 0.32) correlated with total body mass, without any change in the number of nuclei per fiber. Consequently, variation in myonuclear domain (i.e. the amount of cytoplasm per nucleus), was also positively associated with body mass (r2 = 0.51). Therefore, buntings preparing for migration may experience an increase in muscle contraction force due to larger muscle fibers, but this is also coupled with increases in myonuclear domain, which may force these cells to increase protein production to safeguard satellite cells.

Perioperative Pectoralis Muscle Mass and Attenuation Estimated by Computed Tomography are Not Predictors for Mortality after Heart Transplantation

Purpose End-stage heart failure (HF) is often associated with malnutrition and sarcopenia, both of them are related to adverse HF outcomes. Skeletal muscle mass and attenuation are predictors of mortality after continuous flow left ventricular devices (LVAD) implantation. Our purpose was to assess the prognostic impact of skeletal muscle mass on patients undergoing heart transplantation (HT). Methods Retrospective study of a single-center HT population, between 2009 and 2019. Patients > 18 years-old with a computed chest scan in the previous 6 months before HT were included. Multiorgan transplants were excluded. Unilateral pectoralis muscle mass indexed (PMMi) to body surface area and attenuation (by mean Hounsfield units [PHUm]) were measured in each patient. HT patients were classifiedin tertiles according to PMMi and PHUm and characteristics of patients were compared by Chi-square, t-student and Kruskall-Wallis. Multivariate Cox regression analyses were performed to assess the impact of preoperative PMMi and PHUm on survival after HT. Results 132 patients were included, mean age 58.9, 16.7% female, median follow-up 3.67 years (interquartile range 1.7-5.9 years). 41.7% of patients underwent urgent HT (1.5% INTERMACS 1 situation, 15.2% INTERMACS 2 and 28% INTERMACS 3). Both PMMi and PHUm were lower in females and for lowest weight recipients. Urgent HT frequency was similar between tertiles of PMMi, but recipients in the higher tertile of PHUm were more frequently transplanted in an urgent status (38.2% vs 21.8% in the lowest tertile, p= 0.029). 26 patients (19.7%) died during follow-up, 12 (9.1% of total cohort) during HT admission. In the Cox regression analyses, neither PMMi (HR 1.034, 95% CI 0.891-1.2, p= 0.659) nor PHUm (HR 1.02, 95% CI 0.992-1.050, p=0.160) were associated with an increased mortality. Only the needed of mechanical circulatory support and hemofiltration after HT were associated with a higher risk of death. Conclusion Among this single-center HT recipients population, neither lower PMMi nor lower PHUm were associated with worse outcomes after HT.

Trends in Body Mass Index before and after Left Ventricular Assist Device and Association with Pectoralis Muscle Measures: Evidence for Progressive Sarcopenia Prior to LVAD Implantation

PurposeTo test the hypothesis that advanced heart failure patients lose weight prior to LVAD, gain weight after LVAD, and that weight loss prior to LVAD is associated with lower pectroralis muscle measures (PMM) quantified on pre operative chest CT scans.MethodsThe larger cohort for the BMI trend analysis included patients with first-time LVAD implantation at a single center (n=505). The following PMMs were quantified in patients with chest CTs performed within 3 months prior to LVAD implantation (n=194): pectoralis muscle mass indexed to height in meters squared (PMI) and mean Hounsfield units (PHUm). BMI trends before and after LVAD were computed and plotted using Locally Estimated Scatterplot Smoothing (LOESS). BMI prior to LVAD was then regressed longitudinally. The association between BMI trend and PMMs were assessed by including fixed effects for time, PMMs, and their interactions.ResultsBMI plots are displayed (Figure). For the entire cohort, BMI decreased prior to LVAD, continued to decrease further after LVAD, and then steadily increased. Across PMM tertiles, the same pattern was observed. At 100 days prior to LVAD, both PMMs were significantly associated with BMI (p <0.05). The trend of BMI prior to LVAD was signficantly associated with PHUm (p<0.05), with a more severe decline in BMI being associated with lower tissue attenuation (PHUm).ConclusionThe trend in BMI across the larger cohort before and after LVAD suggests that LVAD recipients are largely sarcopenic at the time of LVAD. The correlation between more rapid weight loss and lower PMMs supports this hypothesis. As muscle wasting is progressive, and lower PMMs are assoiciated with increased post-LVAD mortality, there may be a role in utilizing PMMs to determining optimal implantation timing. To test the hypothesis that advanced heart failure patients lose weight prior to LVAD, gain weight after LVAD, and that weight loss prior to LVAD is associated with lower pectroralis muscle measures (PMM) quantified on pre operative chest CT scans. The larger cohort for the BMI trend analysis included patients with first-time LVAD implantation at a single center (n=505). The following PMMs were quantified in patients with chest CTs performed within 3 months prior to LVAD implantation (n=194): pectoralis muscle mass indexed to height in meters squared (PMI) and mean Hounsfield units (PHUm). BMI trends before and after LVAD were computed and plotted using Locally Estimated Scatterplot Smoothing (LOESS). BMI prior to LVAD was then regressed longitudinally. The association between BMI trend and PMMs were assessed by including fixed effects for time, PMMs, and their interactions. BMI plots are displayed (Figure). For the entire cohort, BMI decreased prior to LVAD, continued to decrease further after LVAD, and then steadily increased. Across PMM tertiles, the same pattern was observed. At 100 days prior to LVAD, both PMMs were significantly associated with BMI (p <0.05). The trend of BMI prior to LVAD was signficantly associated with PHUm (p<0.05), with a more severe decline in BMI being associated with lower tissue attenuation (PHUm). The trend in BMI across the larger cohort before and after LVAD suggests that LVAD recipients are largely sarcopenic at the time of LVAD. The correlation between more rapid weight loss and lower PMMs supports this hypothesis. As muscle wasting is progressive, and lower PMMs are assoiciated with increased post-LVAD mortality, there may be a role in utilizing PMMs to determining optimal implantation timing.

Structural plasticity of the avian pectoralis: a case for geometry and the forgotten organelle.

The avian pectoralis muscle demonstrates incredible plasticity. This muscle is the sole thermogenic organ of small passerine birds, and many temperate small passerines increase pectoralis mass in winter, potentially to increase heat production. Similarly, this organ can double in size prior to migration in migratory birds. In this Commentary, following the August Krogh principle, I argue that the avian pectoralis is the perfect tissue to reveal general features of muscle physiology. For example, in both mammals and birds, skeletal muscle fiber diameter is generally accepted to be within 10-100 µm. This size constraint is assumed to include reaction-diffusion limitations, coupled with metabolic cost savings associated with fiber geometry. However, avian muscle fiber structure has been largely ignored in this field, and the extensive remodeling of the avian pectoralis provides a system with which to investigate this. In addition, fiber diameter has been linked to whole-animal metabolic rates, although this has only been addressed in a handful of bird studies, some of which demonstrate previously unreported levels of plasticity and flexibility. Similarly, myonuclei, which are responsible for protein turnover within the fiber, have been forgotten in the avian literature. The few studies that have addressed myonuclear domain (MND) changes in avian muscle have found rates of change not previously seen in mammals. Both fiber diameter and MND have strong implications for aging rates; most aging mammals demonstrate muscular atrophy (a decrease in fiber diameter) and changes in MND. As I discuss here, these features are likely to differ in birds.

Respiratory strength and pectoralis muscle mass as measures of sarcopenia: Relation to outcomes in resected non–small cell lung cancer

ObjectivesPhysical biomarkers to stratify patients with lung cancer into subtypes predictive of outcome beyond tumor-related characteristics are underexplored. This study was designed to investigate the clinical utility of preoperative sarcopenia based on respiratory strength and pectoralis muscle mass to predict the risk of death. MethodsThis retrospective study included 346 consecutive patients undergoing curative-intent resection of non–small cell lung cancer from 2009 to 2013. Respiratory strength and muscle mass were assessed by peak expiratory flow rate and pectoralis muscle index (pectoralis muscle area/body mass index) using preoperative spirometry and chest axial images, respectively. Sarcopenia cutoff points were defined by gender-specific medians of peak expiratory flow rates and pectoralis muscle indices. Survival was compared between patients with sarcopenia and patients without. ResultsSarcopenia was present in 98 patients (28.3%) and was significantly associated with advancing age (P < .001). Patients with sarcopenia exhibited worse 5-year overall survival compared with patients without sarcopenia (69.9% vs 87.2%, P < .001). Multivariate analysis revealed that sarcopenia was an independent adverse prognostic factor (hazard ratio, 1.88; 95% confidence interval, 1.09-3.24; P = .023) after adjustment for gender, age, smoking status, coronary heart disease, diffusing capacity for carbon monoxide, neutrophil-to-lymphocyte ratio, albumin, histologic type, and pathologic stage. ConclusionsPreoperative sarcopenia as identified by the criteria of low respiratory strength and reduced pectoralis muscle mass is significantly associated with poor overall survival. This may help to develop more individualized management strategies and optimize longitudinal care for patients.

McCulloch’s algorithm inspired cuckoo search optimizer based mammographic image segmentation

Multi-level thresholding for mammogram image segmentation leads to much better sub-sections of the intensity span, and hence very useful in breast cancer detection. In order to segment the mammogram image efficiently, in this paper, three popular nature inspired algorithms namely Harmony Search Algorithm (HSA), Electro-magnetism Optimization (EMO) and McCulloch’s Algorithm inspired Cuckoo Search Optimization algorithm (MACSO) are studied in detail; and are employed for desired cost function maximization for two well-known multi-level thresholding methods like Otsu and Kapur efficiently. The proposed approach is applied to all the 322 test images of database presented by Mammographic Image Analysis Society (MIAS), to detect pectoral muscle, breast and suspicious mass efficiently. Performance of EMO, MACSO and HSA were analysed using measures like best fitness, MSE, PSNR, SSIM and TIME. From the experimental results, it is concluded that MACSO with Otsu was found to be robust for segmentation of mammogram images accurately.

Pulmonary Actinomycosis Presenting as Indurated Pectoral Mass

Pulmonary Actinomycosis Presenting as Indurated Pectoral Mass

Prognostic significance of low pectoralis muscle mass on preoperative chest computed tomography in localized non-small cell lung cancer after curative-intent surgery

ObjectivesThe impact of sarcopenia on the outcome in patients following resection of non-small cell lung cancer is yet to be fully determined. This study aimed to evaluate the clinical utility of a computed tomography-based pectoralis muscle assessment, which reflects sarcopenia, to predict the risk of postoperative outcomes. Materials and methodsThis retrospective study included 347 consecutive patients undergoing curative-intent resection of non-small cell lung cancer from 2009 to 2013. The pectoralis muscle index (pectoralis muscle area/body mass index) was assessed at the level of the fourth thoracic vertebra on chest axial images. The primary outcomes were compared between the lowest gender-specific quintile (sarcopenia) and the other quintiles according to the index. The prognostic significance of low pectoralis muscle index was calculated by the Cox proportional hazards regression model. A propensity score matching analysis was performed to adjust the differences in clinical characteristics. ResultsSixty-nine patients were identified with sarcopenia according to the lowest gender-specific quintile of pectoralis muscle index. Patients with sarcopenia exhibited worse 5-year overall survival rate compared with patients without sarcopenia (64.2 % vs. 86.7 %, P < 0.001). Even in stage I non-small cell lung cancer, the rate of 5-year overall survival in the sarcopenia group was lower than that in the non-sarcopenia group (74.2 % vs. 92.4 %, P = 0.001). Multivariate analysis revealed that low pectoralis muscle index was independently associated with adverse overall survival (hazard ratio: 2.09, 95 % confidence interval: 1.20–3.62, P = 0.009). After propensity score matching, the prognostic impact of sarcopenia based on low pectoralis muscle index was also robust for overall survival (hazard ratio: 3.23, 95 % confidence interval: 1.38–7.60, P = 0.007). ConclusionsLow pectoralis muscle index was significantly associated with poor long-term outcomes in patients with localized non-small cell lung cancer after curative surgery. This may help assist preoperative risk stratification and longitudinal management after surgery.

Pectoralis muscle wasting during chemotherapy.

e24069 Background: Chemotherapy is often followed by muscle mass loss which has been associated with frailty. We explored factors associated with change in pectoralis muscle mass after chemotherapy. We hypothesized greater muscle loss with time would be associated with poorer overall survival. Methods: We identified individuals with breast cancer (N = 221), sarcoma (N = 115), and lymphoma (N = 216) who received chemotherapy at the University of Minnesota MHealth Fairview and had CT scans before and after chemotherapy. Right pectoralis muscle area was measured using CORESLICER and indexed to body surface (right pectoralis muscle area [cm2] / body surface [m2]). We calculated quartiles of the indexed pectoralis measure. We restricted our analyses to participants who received a follow-up CT within two years after starting chemotherapy. In a multivariate linear regression, we explored associations of sex, age, BMI, ever-smoking, time since start of chemotherapy, indexed baseline muscle area, stage, type of diagnosis, and cumulative anthracycline dose with relative (%) change in muscle area. In a Cox regression we tested the association of relative muscle change with overall mortality. We used cubic splines to test for nonlinear effects. Results: Of 477 participants (66% female; mean age 61.3 (10.1) years), 366 received anthracyclines, 61 Trastuzumab, and 60 both. The average loss in right pectoral muscle area was -10% for women and -12% for men. We detected nonlinear effects of indexed baseline muscle area, P = 0.03. In a model using quartiles of indexed baseline muscle area, significant predictors of muscle loss included sex (women vs. men, -9.0%, 95% confidence interval (CI) -14.2- -3.7%, P = 0.0008), larger indexed baseline muscle area (quartiles 2, 3, 4 compared with quartile 1, change range -7 - -24%, 95% CI range, -2 - -30%, P-range &lt; 0.0001 – 0.006), smoking (ever vs. never, -4.1%, 95% CI -7.6 - -0.7%, P = 0.02), and diagnosis (sarcoma vs breast cancer, -5.7%, 95% CI -11.1 - -0.3%, P = 0.04). There was no significant association between muscle change and overall survival (median follow-up time 4.1). Conclusions: Being female, larger baseline muscle mass (per m2 body surface), ever-smoking, and a sarcoma diagnosis were associated with greater relative muscle loss after chemotherapy. More data is needed to understand the course of sarcopenia in terms of recovery and survivorship. [Table: see text]

Muscle mass loss after neoadjuvant chemotherapy in breast cancer: estimation on breast magnetic resonance imaging using pectoralis muscle area.

The loss of skeletal muscle mass is widely considered a predictor of poor survival and toxicity in breast cancer patients. The aim of this study is to evaluate if there is pectoralis muscle area (PMA) variation, reflecting loss of skeletal muscle mass, on consecutive MRI examinations after neoadjuvant chemotherapy. The retrospective study protocol was approved by our institutional review board. A total of n = 110 consecutive patients (mean age 56 ± 11years) who were treated with neoadjuvant chemotherapy (NAC) for histologically proven primary breast cancer between January 2017 and January 2019 and in whom tumor response was checked with standard breast MRI were included. Two radiologists calculated the pectoralis muscle cross-sectional area before and after NAC. Time between the MRI examinations, before starting NAC and after completing NAC, was 166.8 ± 50days. PMA calculated pre-NAC (8.14cm2) was larger than PMA calculated post-NAC (7.03cm2) (p < 0.001). According to the Response Evaluation Criteria in Solid Tumors (RECIST) criteria, there were no significant differences between responders (complete or partial response) and non-responders (p = 0.362). The multivariate regression analysis did not show any significant relationships between ΔPMA and age, time between MRI exams, estrogen and progesterone receptor status, human epidermal growth factor receptor status (HER-2), Ki-67 expression, lymph node status, RECIST criteria, histological type, average lesion size, molecular categories, and grade. Inter-reader (k = 0.72) and intra-reader agreement (0.69 and 0.71) in PMA assessment were good. Pectoralis muscle mass varies in breast cancer patients undergoing NAC and this difference can be estimated directly on standard breast MRI. • Pectoralis muscle area variation reflects loss of skeletal muscle mass. • Pectoralis muscle area on MRI is reduced after NAC. • Pectoralis muscle mass loss seems independent from other variables.

Pre-Operative Pectoralis Muscle Quantity and Attenuation by Computed Tomography are Predictive of Recurrent Gastrointestinal Bleeding on Left Ventricular Assist Device Support: A Multicenter Analysis

Pectoralis muscle mass and tissue attenuation obtained on preoperative CT scans are powerful predictors of mortality after LVAD implantation. Gastrointestinal (GI) bleeding remains a common problem on mechanical support. It is unknown whether these skeletal muscle measures, which correlate with frailty and tissue quality, are associated with the development of recurrent GI bleeding. We performed a retrospective, multi-centered study which included patients with chest CTs performed ≤ 3 months prior to LVAD implantation at the University of Minnesota (n=143) and Houston Methodist Hospital (n=133). Unilateral pectoralis muscle mass indexed to body surface area (PMI) and attenuation (approximated by mean Hounsfield units; PHUm) were measured on preoperative chest CT scans. GIB events were captured for the first two years of LVAD support. Negative binomial regression analyses were performed to determine the association between pectoralis muscle measures and number of GIB events on LVAD support. The mean age of the study cohort was 59 + /- 13 years, 43 % were bridge to transplant and 62 % had ischemic cardiomyopathy. Thirty-two patients had at last one GI bleed while on LVAD support over 2 years. Both pectoralis muscle mass and tissue attenuation were associated with the incidence rate of GI bleeding on LVAD support. Each 5 unit increase in PHUm was associated with reduction in the incidence rate of GIB (adjusted 18 % reduction, 95 % CI 6-28 %, p = 0.005). Each unit increase in PMI was associated with a reduction in the incidence of GIB (adjusted 19 % reduction, 95 % CI 3- 34 %, p = 0.029). The final models were adjusted for age, sex, INTERMACS profile, BTT status, creatinine and albumin. Preoperative pectoralis muscle size and attenuation were associated with the development of recurrent GI bleeding after LVAD implantation in this multicenter cohort. This one time, internal assessment of patient substrate appears to predict not only mortality after LVAD, but morbidity as well.

External Validation of the Minnesota Pectoralis Muscle Risk Score to Predict Mortality after Ventricular Assist Device Implantation

We previously developed a post LVAD mortality prediction model using multicenter data incorporating pectoralis muscle mass and tissue attenuation obtained on preoperative CT scans. The purpose of this analysis was to evaluate the performance of this model in a prospective cohort including the most contemporary LVADs. Since 2016, all patients who underwent first time LVAD implantation at the University of Minnesota had chest CTs performed prior to surgery (n=82). None of the patients included in the Minnesota Pectoralis Muscle Risk Score (MPRS) development cohort were included in this analysis. Unilateral pectoralis muscle mass indexed to body surface area (PMI) and attenuation (approximated by mean Hounsfield units; PHUm) were measured from pre-operative CT scans. MPRSs were calculated on all patients using the following variables: PHUm, PMI, African American race, creatinine, total bilirubin, body mass index, bridge to transplant status and presence or absence of contrast. Cox regression analysis was performed to test the association between the MPRS and post LVAD mortality. Receiver-operating characteristic (ROC) curves were then generated to test model discrimination at 30 and 90 days post LVAD implantation. The prospective cohort included 62% HeartMate 3, 17% HVAD, and 20% HeartMate 2 devices. Each two point increase in MPRS was associated with a 2.6 fold increase in the mortality after LVAD (HR 2.6, 95% CI 1.3-5.4, p=0.01). The area under the curve for the MPRS was 0.73 at 30 days and 0.72 at 90 days. The Pectoralis Muscle Risk Score had favorable discrimination in this contemporary prospective cohort, which was largely comprised of patients receiving HeartMate 3 devices. These skeletal muscle measures, which are associated with heart failure stage and frailty, continue to add important information to pre-operative risk assessment.

An Early Assessment of the Association between Pectoralis Muscle Measures and Frailty

The association between pectoralis muscle measurements and objective frailty assessments in the heart failure population has not been previously reported. The study cohort included patients who had first-time CF-LVAD implants at the University of Minnesota between 2017-2018 who had 1) chest CTs and 2) frailty assessments performed in the 3 months prior to LVAD (n=27). Unilateral pectoralis muscle mass indexed to height in meters squared and attenuation (approximated by mean Hounsfield units) were measured on preoperative chest CT scans ​using Slice-O-Matic software. Frailty was assessed with a 6 point Clinical Frailty Scale. Multivariable linear regression was performed to assess the association between pectoralis muscle measures and frailty scores. After multivariate adjustment, each frailty score increase (more frail) was associated with an adjusted decrease of 3.9 in the mean pectoralis muscle hounsfield units (95% CI= -7.4 to -0.41, p=0.03). A statistically significant association between pectoralis muscle mass index and frailty scores was not detected (-0.61 95% CI = -1.4 to 0.2; p =0.15). Multivariable models were adjusted for age, sex, and INTERMACS profile. In this small sample of patients with simultaneous frailty and pectoralis muscle measurements, a significant association was detected between tissue attenuation and frailty. Further data will be needed to confirm this finding and to determine the degree that frailty can be reversed with LVAD support.

Seasonal variation in body composition in an Afrotropical passerine bird: increases in pectoral muscle mass are, unexpectedly, associated with lower thermogenic capacity.

Phenotypic flexibility in avian metabolic rates and body composition have been well-studied in high-latitude species, which typically increase basal metabolic rate (BMR) and summit metabolism (Msum) when acclimatized to winter conditions. Patterns of seasonal metabolic acclimatization are more variable in lower-latitude birds that experience milder winters, with fewer studies investigating adjustments in avian organ and muscle masses in the context of metabolic flexibility in these regions. We quantified seasonal variation (summer vs winter) in the masses of organs and muscles frequently associated with changes in BMR (gizzard, intestines and liver) and Msum (heart and pectoral muscles), in white-browed sparrow-weavers (Plocepasser mahali). We also measured pectoral muscle thickness using a portable ultrasound system to determine whether we could non-lethally estimate muscle size. A concurrent study measured seasonal changes in BMR and Msum in the same population of sparrow-weavers, but different individuals. There was no seasonal variation in the dry masses of the gizzard, intestines or liver of sparrow-weavers, and during the same period, BMR did not vary seasonally. We found significantly higher heart (~ 18% higher) and pectoral muscle (~ 9% higher) dry mass during winter, although ultrasound measurements did not detect seasonal changes in pectoral muscle size. Despite winter increases in pectoral muscle mass, Msum was ~ 26% lower in winter compared to summer. To the best of our knowledge, this is the first study to report an increase in avian pectoral muscle mass but a concomitant decrease in thermogenic capacity.

A Novel Model Incorporating Pectoralis Muscle Measures to Predict Mortality After Ventricular Assist Device Implantation

BackgroundWe have previously demonstrated that pectoralis muscle mass and tissue attenuation obtained on preoperative CT scans were powerful predictors of mortality after left ventricular assist device implantation. In this analysis, we confirm our findings in a separate left ventricular assist device implantation cohort, and we present a novel, user-friendly mortality-prediction model incorporating these measures. Methods and ResultsPatients with chest CTs performed ≤ 3 months prior to left ventricular assist device implantation at University of Minnesota (n = 143) and Houston Methodist Hospital (n = 133) were identified. Unilateral pectoralis muscle mass indexed to body surface area (PMI) and attenuation (approximated by mean Hounsfield units) (PHUm) were measured on preoperative chest CT scans. To develop a prediction model incorporating pectoralis muscle measures, we implemented a cross-validated model-selection approach using Cox proportional hazards regression models. The final model included PHUm, PMI, African American race, creatinine, total bilirubin, body mass index, bridge to transplant, and presence or absence of contrast. Receiver-operating characteristic curves for 30-, 90- and 365-day survival were generated. The area under the curve for the model at 30, 90 and 365 days was 0.78, 0.76 and 0.76, respectively. ConclusionsThe Minnesota Pectoralis Risk Score had favorable discrimination in this multicenter dataset. These skeletal-muscle measures appear to add important information to preoperative risk assessment.

The dive performance of immature king penguins following their annual molt suggests physiological constraints.

Like all birds, penguins undergo periodic molt, during which they replace old feathers. However, unlike other birds, penguins replace their entire plumage within a short period while fasting ashore. During molt, king penguins (Aptenodytes patagonicus) lose half of their initial body mass, most importantly their insulating subcutaneous fat and half of their pectoral muscle mass. The latter might challenge their capacity to generate and sustain a sufficient mechanical power output to swim to distant food sources and propel themselves to great depth for successful prey capture. To investigate the effects of the annual molt fast on their dive/foraging performance, we studied various dive/foraging parameters and peripheral temperature patterns in immature king penguins across two molt cycles, after birds had spent their first and second year at sea, using implanted data-loggers. We found that the dive/foraging performance of immature king penguins was significantly reduced during post-molt foraging trips. Dive and bottom duration for a given depth were shorter during post-molt and post-dive surface interval duration was longer, reducing overall dive efficiency and underwater foraging time. We attribute this decline to the severe physiological changes that birds undergo during their annual molt. Peripheral temperature patterns differed greatly between pre- and post-molt trips, indicating the loss of the insulating subcutaneous fat layer during molt. Peripheral perfusion, as inferred from peripheral temperature, was restricted to short periods at night during pre-molt but occurred throughout extended periods during post-molt, reflecting the need to rapidly deposit an insulating fat layer during the latter period.

Diet-related Physiological Plasticity of Mourning Doves: A Metabolomic Approach (P09-002-19)

ObjectivesAs birds are a natural model of diabetes, the objective of this study was to test the hypothesis that feeding adult mourning doves, Zenaida macroura, a high fat diet (60% calories from fat; HF) or refined carbohydrate diet (white bread: WB) for four weeks results in diabetes-like pathologies including hyperglycemia and altered metabolic profiles. MethodsSeparate cohorts of doves were captured for each feeding trial and were acclimated for one week to their respective study diets; cohort 1: WB (n = 6) vs nutritionally-balanced seeds (n = 6), and cohort 2: HF (n = 4) vs control (n = 6). The WB study mimicked natural feeding options for wild birds whereas the HF study used experimental diets. Four weeks later, birds were euthanized with an overdose of sodium pentobarbital and we collected cardiac blood, liver, kidney (HF study only), and pectoralis muscle for metabolomic analyses and biochemical assays. ResultsPathway analysis of metabolic concentrations revealed only two pathways that were significantly altered (p < 0.05) and concurrently highly impacted (scale: 0-1; > 0.60) by the HF diet consumption: ubiquinone and other terpenoid-quinone biosynthesis (plasma and pectoralis muscle) and alanine, aspartate, and glutamate metabolism (plasma and kidney; p < 0.05). Only three low impact pathways were significantly affected by the WB diet consumption: glutathione metabolism and histidine metabolism (liver), and glyoxylate and dicarboxylate metabolism (pectoralis muscle; p < 0.05). Further, consumption neither of the HF nor of the WB diet altered plasma uric acid, insulin, pectoralis muscle, liver triglycerides, or body mass (only measured in HF study) significantly, but liver glycogen concentrations were 2.12-fold higher in WB than control doves (p < 0.015). Lastly, blood glucose concentrations did not differ between WB or HF birds and control birds. ConclusionsContrary to our hypothesis, consumption of a WB or HF diet for four weeks did not induce symptoms of diabetes in doves. Further elucidating the apparent avian resistance to diet-induced metabolic complications may help develop novel therapeutic agents for mammalian diabetes. Funding SourcesASU School of Life Sciences/Office of Knowledge Enterprise Development - Research Investment Initiative, a summer research fellowship from the American Physiology Society, and the Center of Evolution and Medicine Graduate Fellow Award.

Evolutionary design of a flexible, seasonally migratory, avian phenotype: why trade gizzard mass against pectoral muscle mass?

Migratory birds undergo impressive body remodelling over the course of an annual cycle. Prior to long-distance flights, red knots ( Calidris canutus islandica) reduce gizzard mass while increasing body mass and pectoral muscle mass. Although body mass and pectoral muscle mass are functionally linked via their joint effects on flight performance, gizzard and pectoral muscle mass are thought to be independently regulated. Current hypotheses for observed negative within-individual covariation between gizzard and pectoral muscle mass in free-living knots are based on a common factor (e.g. migration) simultaneously affecting both traits, and/or protein limitation forcing allocation decisions. We used diet manipulations to generate within-individual variation in gizzard mass and test for independence between gizzard and pectoral muscle mass within individuals outside the period of migration and under conditions of high protein availability. Contrary to our prediction, we observed a negative within-individual covariation between gizzard and pectoral muscle mass. We discuss this result as a potential outcome of an evolved mechanism underlying body remodelling associated with migration. Although our proposed mechanism requires empirical testing, this study echoes earlier calls for greater integration of studies of function and mechanism, and in particular, the need for more explicit consideration of the evolution of mechanisms underlying phenotypic design.

Heart Failure Severity Stratification beyond INTERMACS Profiles: A Step towards Identification of Optimal LVAD Implantation Timing

Purpose As skeletal muscle mass and quality decrease with heart failure progression, we hypothesized that pectoralis muscle mass and tissue attenuation measured on pre-left ventricular assist device (LVAD) CT scans would add meaningful heart failure severity stratification beyond INTERMACS profile alone. Methods Patients with chest CTs performed ≤ 3 months prior to LVAD implantation at University of Minnesota (n=143) and Houston Methodist Hospital (n=133) were identified from the larger cohorts (University of Minnesota n=353, Houston Methodist =278). Unilateral Pectoralis muscle mass indexed to body surface area and pectoralis muscle attenuation (approximated by mean Hounsfield units; PHUm) was measured on pre-operative chest CT scans. Patients within each INTERMACS profile were separated into HIGH and LOW pectoralis muscle measure groups (HIGH = upper two pectoralis muscle tertiles, LOW = lowest pectoralis muscle tertiles, repeated for both PMI and PHUm). Kaplan Meier survival analyses were performed to compare mortality among INTERMACS profiles by HIGH and LOW pectoralis muscle measure groups. Results INTERMACS 3 and 4 patients in the HIGH PHUm groups had the highest survival on LVAD support (2-year survival 80%, 95% CI 70 - 87%, p =0.0002). When the analysis was repeated for PMI, INTERMACS 3 and 4 patients in the HIGH PMI groups had the highest survival on LVAD support (2-year survival 80%, 95% CI 70 - 87%, p = 0.004). Conclusion INTERMACS 3 and 4 patients with the highest pectoralis muscle measures had the best survival on mechanical support. As skeletal muscle wasting is accelerated with advanced heart failure, these measures may help identify patients in whom watchful waiting is not safe. Further data will be required to confirm this hypothesis.