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McKirnan MD, Ichikawa Y, Zhang Z, Zemljic-Harpf AE, Fan S, Barupal DK, Patel HH, Hammond HK, Roth DM. Metabolomic analysis of serum and myocardium in compensated heart failure after myocardial infarction. Life Sci 2019; 221:212-223. [PMID: 30731143 DOI: 10.1016/j.lfs.2019.01.040] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 01/18/2019] [Accepted: 01/25/2019] [Indexed: 01/06/2023]
Abstract
AIMS To determine the metabolic adaptations to compensated heart failure using a reproducible model of myocardial infarction and an unbiased metabolic screen. To address the limitations in sample availability and model variability observed in preclinical and clinical metabolic investigations of heart failure. MAIN METHODS Metabolomic analysis was performed on serum and myocardial tissue from rabbits after myocardial infarction (MI) was induced by cryo-injury of the left ventricular free wall. Rabbits followed for 12 weeks after MI exhibited left ventricular dilation and depressed systolic function as determined by echocardiography. Serum and tissue from the viable left ventricular free wall, interventricular septum and right ventricle were analyzed using a gas chromatography time of flight mass spectrometry-based untargeted metabolomics assay for primary metabolites. KEY FINDINGS Unique results included: a two- three-fold increase in taurine levels in all three ventricular regions of MI rabbits and similarly, the three regions had increased inosine levels compared to sham controls. Reduced myocardial levels of myo-inositol in the myocardium of MI animals point to altered phospholipid metabolism and membrane receptor function in heart failure. Metabolite profiles also provide evidence for responses to oxidative stress and an impairment in TCA cycle energy production in the failing heart. SIGNIFICANCE Our results revealed metabolic changes during compensated cardiac dysfunction and suggest potential targets for altering the progression of heart failure.
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Affiliation(s)
- M Dan McKirnan
- Department of Anesthesiology, University of California, the Veterans Affairs San Diego Healthcare System, La Jolla, San Diego, CA, United States of America; Department of Medicine, University of California, the Veterans Affairs San Diego Healthcare System, La Jolla, San Diego, CA, United States of America
| | - Yasuhiro Ichikawa
- Department of Anesthesiology, University of California, the Veterans Affairs San Diego Healthcare System, La Jolla, San Diego, CA, United States of America
| | - Zheng Zhang
- Department of Anesthesiology, University of California, the Veterans Affairs San Diego Healthcare System, La Jolla, San Diego, CA, United States of America
| | - Alice E Zemljic-Harpf
- Department of Anesthesiology, University of California, the Veterans Affairs San Diego Healthcare System, La Jolla, San Diego, CA, United States of America
| | - Sili Fan
- UC Davis Genome Center, University of California, Davis, CA, United States of America
| | - Dinesh Kumar Barupal
- UC Davis Genome Center, University of California, Davis, CA, United States of America
| | - Hemal H Patel
- Department of Anesthesiology, University of California, the Veterans Affairs San Diego Healthcare System, La Jolla, San Diego, CA, United States of America
| | - H Kirk Hammond
- Department of Medicine, University of California, the Veterans Affairs San Diego Healthcare System, La Jolla, San Diego, CA, United States of America
| | - David M Roth
- Department of Anesthesiology, University of California, the Veterans Affairs San Diego Healthcare System, La Jolla, San Diego, CA, United States of America.
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Feng Y, Hemmeryckx B, Frederix L, Lox M, Wu J, Heggermont W, Lu HR, Gallacher D, Oyen R, Lijnen HR, Ni Y. Monitoring reperfused myocardial infarction with delayed left ventricular systolic dysfunction in rabbits by longitudinal imaging. Quant Imaging Med Surg 2018; 8:754-769. [PMID: 30306056 DOI: 10.21037/qims.2018.09.05] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Background An experimental imaging platform for longitudinal monitoring and evaluation of cardiac morphology-function changes has been long desired. We sought to establish such a platform by using a rabbit model of reperfused myocardial infarction (MI) that develops chronic left ventricle systolic dysfunction (LVSD) within 7 weeks. Methods Fifty-five New Zeeland white (NZW) rabbits received sham-operated or 60-min left circumflex coronary artery (LCx) ligation followed by reperfusion. Cardiac magnetic resonance imaging (cMRI), transthoracic echocardiography (echo), and blood samples were collected at baseline, in acute (48 hours or 1 week) and chronic (7 weeks) stage subsequent to MI for in vivo assessment of infarct size, cardiac morphology, LV function, and myocardial enzymes. Seven weeks post MI, animals were sacrificed and heart tissues were processed for histopathological staining. Results The success rate of surgical operation was 87.27%. The animal mortality rates were 12.7% and 3.6% both in acute and chronic stage separately. Serum levels of the myocardial enzyme cardiac Troponin T (cTnT) were significantly increased in MI rabbits as compared with sham animals after 4 hours of operation (P<0.05). According to cardiac morphology and function changes, 4 groups could be distinguished: sham rabbits (n=12), and MI rabbits with no (MI_NO_LVSD; n=10), moderate (MI_M_LVSD; n=9) and severe (MI_S_LVSD; n=15) LVSD. No significant differences in cardiac function or wall thickening between sham and MI_NO_LVSD rabbits were observed at both stages using both cMRI and echo methods. cMRI data showed that MI_M_LVSD rabbits exhibited a reduction of ejection fraction (EF) and an increase in end-systolic volume (ESV) at the acute phase, while at the chronic stage these parameters did not change further. Moreover, in MI_S_LVSD animals, these observations were more striking at the acute stage followed by a further decline in EF and increase in ESV at the chronic stage. Lateral wall thickening determined by cMRI was significantly decreased in MI_M_LVSD versus MI_NO_LVSD animals at both stages (P<0.05). As for MI_S_LVSD versus MI_M_LVSD rabbits, the thickening of anterior, inferior and lateral walls was significantly more decreased at both stages (P<0.05). Echo confirmed the findings of cMRI. Furthermore, these in vivo outcomes including those from vivid cine cMRI could be supported by exactly matched ex vivo histomorphological evidences. Conclusions Our findings indicate that chronic LVSD developed over time after surgery-induced MI in rabbits can be longitudinally evaluated using non-invasive imaging techniques and confirmed by the entire-heart-slice histomorphology. This experimental LVSD platform in rabbits may interest researchers in the field of experimental cardiology and help strengthen drug development and translational research for the management of cardiovascular diseases.
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Affiliation(s)
- Yuanbo Feng
- Radiology, Department of Imaging and Pathology, KU Leuven, Leuven, Belgium
| | - Bianca Hemmeryckx
- Center for Molecular and Vascular Biology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium
| | - Liesbeth Frederix
- Center for Molecular and Vascular Biology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium
| | - Marleen Lox
- Center for Molecular and Vascular Biology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium
| | - Jun Wu
- Ultrasound Diagnostic department, the second affiliated hospital of Dalian Medical University, Dalian 116000, China
| | - Ward Heggermont
- Center for Molecular and Vascular Biology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium
| | - Hua Rong Lu
- Translational Sciences, Safety Pharmacology Research, Janssen Research & Development, Janssen Pharmaceutical NV, Beerse, Belgium
| | - David Gallacher
- Translational Sciences, Safety Pharmacology Research, Janssen Research & Development, Janssen Pharmaceutical NV, Beerse, Belgium
| | - Raymond Oyen
- Radiology, Department of Imaging and Pathology, KU Leuven, Leuven, Belgium
| | - H Roger Lijnen
- Center for Molecular and Vascular Biology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium
| | - Yicheng Ni
- Radiology, Department of Imaging and Pathology, KU Leuven, Leuven, Belgium
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Ramos SR, Pieles G, Hui W, Ishii R, Slorach C, Friedberg MK. Comprehensive echocardiographic assessment of biventricular function in the rabbit, animal model in cardiovascular research: feasibility and normal values. Int J Cardiovasc Imaging 2017; 34:367-375. [PMID: 28840383 DOI: 10.1007/s10554-017-1238-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/13/2017] [Accepted: 08/21/2017] [Indexed: 11/26/2022]
Abstract
Quantification of cardiac structure and function is central in cardiovascular research. Rabbits are valuable research models of cardiovascular human disease; however, there is little normal data available. The aim of this study was to investigate feasibility and provide normal values for comprehensive echocardiographic assessment of biventricular function in rabbits. New Zealand white rabbits underwent trans-thoracic echocardiography using a general electric (GE) Vivid 7/E9 system with a 10 MHz transducer, under light sedation, to evaluate biventricular function and dimensions. Images for two-dimensional, M-mode, tissue Doppler imaging (TDI) and speckle-tracking strain echocardiography were acquired and analysed. 55 male rabbits (sized matched with a newborn human baby) were studied, mean weight was 2.9 ± 0.23 kg. Adequate images were obtained in 90% for the left ventricle (LV) and 80% for the right ventricle (RV). Two-dimensional speckle-tracking strain was feasible in 60%. Average heart rate was 248 ± 36 beats per minute; LV ejection faction 72 ± 8.0; RV fractional area change 45.9 ± 9.0%; RV myocardial performance index 0.39 ± 0.35; tricuspid annular planar systolic excursion 0.60 ± 0.24 cm. LV TDI parameters were S' 8.6 ± 3.1 cm/s; E' 12.0 ± 4.46 cm/s. RV TDI parameters were S' 10.49 ± 3.18; E' 14.95 ± 4.64 cm/s. LV and RV global peak systolic longitudinal strain were -17 ± 5 and -22 ± 8%, respectively. Comprehensive investigation of biventricular dimensions and function by echocardiography is feasible in the rabbit. Apical views and strain imaging have lower feasibility. Normal values of LV and RV functional parameters are with comparable values to human children. Animal cardiovascular research is key to develop new goals in clinical practice.
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Affiliation(s)
- Sara Roldan Ramos
- The Labatt Family Heart Center, Hospital for Sick Children and University of Toronto, 555 University Avenue, Toronto, ON, M5G 1X8, Canada.
- Department of Congenital Cardiac Surgery and Paediatric Cardiology, Bristol Heart Institute and Bristol Royal Hospital for Children, Upper Maudlin Street, Bristol, UK.
| | - Guido Pieles
- The Labatt Family Heart Center, Hospital for Sick Children and University of Toronto, 555 University Avenue, Toronto, ON, M5G 1X8, Canada
- Department of Congenital Cardiac Surgery and Paediatric Cardiology, Bristol Heart Institute and Bristol Royal Hospital for Children, Upper Maudlin Street, Bristol, UK
| | - Wei Hui
- The Labatt Family Heart Center, Hospital for Sick Children and University of Toronto, 555 University Avenue, Toronto, ON, M5G 1X8, Canada
| | - Ryo Ishii
- The Labatt Family Heart Center, Hospital for Sick Children and University of Toronto, 555 University Avenue, Toronto, ON, M5G 1X8, Canada
| | - Cameron Slorach
- The Labatt Family Heart Center, Hospital for Sick Children and University of Toronto, 555 University Avenue, Toronto, ON, M5G 1X8, Canada
| | - Mark K Friedberg
- The Labatt Family Heart Center, Hospital for Sick Children and University of Toronto, 555 University Avenue, Toronto, ON, M5G 1X8, Canada.
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Implantation of a Poly-L-Lactide GCSF-Functionalized Scaffold in a Model of Chronic Myocardial Infarction. J Cardiovasc Transl Res 2017; 10:47-65. [PMID: 28116550 PMCID: PMC5323505 DOI: 10.1007/s12265-016-9718-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 11/03/2016] [Indexed: 12/17/2022]
Abstract
A previously developed poly-l-lactide scaffold releasing granulocyte colony-stimulating factor (PLLA/GCSF) was tested in a rabbit chronic model of myocardial infarction (MI) as a ventricular patch. Control groups were constituted by healthy, chronic MI and nonfunctionalized PLLA scaffold. PLLA-based electrospun scaffold efficiently integrated into a chronic infarcted myocardium. Functionalization of the biopolymer with GCSF led to increased fibroblast-like vimentin-positive cellular colonization and reduced inflammatory cell infiltration within the micrometric fiber mesh in comparison to nonfunctionalized scaffold; PLLA/GCSF polymer induced an angiogenetic process with a statistically significant increase in the number of neovessels compared to the nonfunctionalized scaffold; PLLA/GCSF implanted at the infarcted zone induced a reorganization of the ECM architecture leading to connective tissue deposition and scar remodeling. These findings were coupled with a reduction in end-systolic and end-diastolic volumes, indicating a preventive effect of the scaffold on ventricular dilation, and an improvement in cardiac performance.
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Takatori O, Usui S, Okajima M, Kaneko S, Ootsuji H, Takashima SI, Kobayashi D, Murai H, Furusho H, Takamura M. Sodium 4-Phenylbutyrate Attenuates Myocardial Reperfusion Injury by Reducing the Unfolded Protein Response. J Cardiovasc Pharmacol Ther 2016; 22:283-292. [PMID: 27909014 DOI: 10.1177/1074248416679308] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
BACKGROUND The unfolded protein response (UPR) plays a pivotal role in ischemia-reperfusion (I/R) injury in various organs such as heart, brain, and liver. Sodium 4-phenylbutyrate (PBA) reportedly acts as a chemical chaperone that reduces UPR. In the present study, we evaluated the effect of PBA on reducing the UPR and protecting against myocardial I/R injury in mice. METHODS Male C57BL/6 mice were subjected to 30-minute myocardial I/R, and were treated with phosphate-buffered saline (as a vehicle) or PBA. RESULTS At 4 hours after reperfusion, mice treated with PBA had reduced serum cardiac troponin I levels and numbers of apoptotic cells in left ventricles (LVs) in myocardial I/R. Infarct size had also reduced in mice treated with PBA at 48 hours after reperfusion. At 2 hours after reperfusion, UPR markers, including eukaryotic initiation of the factor 2α-subunit, activating transcription factor-6, inositol-requiring enzyme-1, glucose-regulated protein 78, CCAAT/enhancer-binding protein (C/EBP) homologous protein, and caspase-12, were significantly increased in mice treated with vehicle compared to sham-operated mice. Administration of PBA significantly reduced the I/R-induced increases of these markers. Cardiac function and dimensions were assessed at 21 days after I/R. Sodium 4-phenylbutyrate dedicated to the improvement of cardiac parameters deterioration including LV end-diastolic diameter and LV fractional shortening. Consistently, PBA reduced messenger RNA expression levels of cardiac remodeling markers such as collagen type 1α1, brain natriuretic peptide, and α skeletal muscle actin in LV at 21 days after I/R. CONCLUSION Unfolded protein response mediates myocardial I/R injury. Administration of PBA reduces the UPR, apoptosis, infarct size, and preserved cardiac function. Hence, PBA may be a therapeutic option to attenuate myocardial I/R injury in clinical practice.
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Affiliation(s)
- Osamu Takatori
- 1 Department of Disease Control and Homeostasis, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan
| | - Soichiro Usui
- 1 Department of Disease Control and Homeostasis, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan
| | - Masaki Okajima
- 1 Department of Disease Control and Homeostasis, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan
| | - Shuichi Kaneko
- 1 Department of Disease Control and Homeostasis, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan
| | - Hiroshi Ootsuji
- 1 Department of Disease Control and Homeostasis, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan
| | - Shin-Ichiro Takashima
- 1 Department of Disease Control and Homeostasis, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan
| | - Daisuke Kobayashi
- 1 Department of Disease Control and Homeostasis, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan
| | - Hisayoshi Murai
- 1 Department of Disease Control and Homeostasis, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan
| | - Hiroshi Furusho
- 1 Department of Disease Control and Homeostasis, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan
| | - Masayuki Takamura
- 1 Department of Disease Control and Homeostasis, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan
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Liu L, Mu Y, Han W, Wang C. Association of hypercholesterolemia and cardiac function evaluated by speckle tracking echocardiography in a rabbit model. Lipids Health Dis 2014; 13:128. [PMID: 25106812 PMCID: PMC4245723 DOI: 10.1186/1476-511x-13-128] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2014] [Accepted: 08/01/2014] [Indexed: 11/10/2022] Open
Abstract
Background Although hypercholesterolemia is a major risk factor for coronary artery disease (CAD), only limited data are available regarding its direct effect on myocardial function apart from CAD. The aim of this study was to evaluate LV systolic function using speckle-tracking echocardiography and investigate the relationship between hypercholesterolemia and myocardial function. Methods Twenty-eight rabbits were randomly divided into three groups: 8 were fed normal chow for 3 months (group 1) and the remaining 20 were fed an atherogenic diet for 2 (group 2) or 3 months (group 3). Global systolic radial, circumferential and longitudinal peak strain were calculated. Serum total cholesterol (TC), low density lipoprotein cholesterol (LDL-C) and myocardial cholesterol levels were measured. Results Global systolic longitudinal strain were both decreased in the group 2 and 3 (P < 0.001), whereas radial strain were increased (P < 0.001) compared with group 1. Global circumferential strain in the group 3 was significantly reduced (P < 0.001). Serum and myocardial cholesterol concentration markedly increased in the group 2 and group 3 (P < 0.001). There was a significant inverse correlation between longitudinal strain and serum TC, LDL-C as well as myocardial cholesterol levels (r = - 0.723, r = - 0.794, r = - 0.700, P both < 0.001). A significant negative correlation was also noted between circumferential strain and serum TC, LDL-C as well as myocardial cholesterol levels (r = - 0.518, P = 0.007; r = - 0.691, P < 0.001; r = - 0.659, P < 0.001). A significant positive correlation was found between radial strain and serum TC, LDL-C as well as myocardial cholesterol levels (r = 0.432, P = 0.028; r = 0.602, P = 0.001; r = 0.469, P = 0.016). Conclusion Although LV morphology and ejection fractions were not different among the three groups, elevated concentration of cholesterol, especially in serum LDL-C, was significantly associated with LV systolic dysfunction. The findings also indicate that reductions in longitudinal was the first appeared, followed by circumferential, and was compensated for by increasing radial strain.
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Affiliation(s)
| | - Yuming Mu
- Department of Echocardiography, Center of Medical Ultrasound, First Affiliated Hospital of Xinjiang Medical University, No, 137, Li Yu Shan South Road, Urumqi 830011, China.
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Braunersreuther V, Montecucco F, Pelli G, Galan K, Proudfoot AE, Belin A, Vuilleumier N, Burger F, Lenglet S, Caffa I, Soncini D, Nencioni A, Vallée JP, Mach F. Treatment with the CC chemokine-binding protein Evasin-4 improves post-infarction myocardial injury and survival in mice. Thromb Haemost 2013; 110:807-25. [PMID: 23925450 DOI: 10.1160/th13-04-0297] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Accepted: 07/03/2013] [Indexed: 12/16/2022]
Abstract
Chemokines trigger leukocyte trafficking and are implicated in cardiovascular disease pathophysiology. Chemokine-binding proteins, called "Evasins" have been shown to inhibit both CC and CXC chemokine-mediated bioactivities. Here, we investigated whether treatment with Evasin-3 (CXC chemokine inhibitor) and Evasin-4 (CC chemokine inhibitor) could influence post-infarction myocardial injury and remodelling. C57Bl/6 mice were submitted in vivo to left coronary artery permanent ligature and followed up for different times (up to 21 days). After coronary occlusion, three intraperitoneal injections of 10 μg Evasin-3, 1 μg Evasin-4 or equal volume of vehicle (PBS) were performed at 5 minutes, 24 hours (h) and 48 h after ischaemia onset. Both anti-chemokine treatments were associated with the beneficial reduction in infarct size as compared to controls. This effect was accompanied by a decrease in post-infarction myocardial leukocyte infiltration, reactive oxygen species release, and circulating levels of CXCL1 and CCL2. Treatment with Evasin-4 induced a more potent effect, abrogating the inflammation already at one day after ischaemia onset. At days 1 and 21 after ischaemia onset, both anti-chemokine treatments failed to significantly improve cardiac function, remodelling and scar formation. At 21-day follow-up, mouse survival was exclusively improved by Evasin-4 treatment when compared to control vehicle. In conclusion, we showed that the selective inhibition of CC chemokines (i.e. CCL5) with Evasin-4 reduced cardiac injury/inflammation and improved survival. Despite the inhibition of CXC chemokine bioactivities, Evasin-3 did not affect mouse survival. Therefore, early inhibition of CC chemokines might represent a promising therapeutic approach to reduce the development of post-infarction heart failure in mice.
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Affiliation(s)
- Vincent Braunersreuther
- Fabrizio Montecucco, MD, PhD, Cardiology Division, Department of Medicine, Geneva University Hospital, Foundation for Medical Researches, 64 Avenue Roseraie, 1211 Geneva, Switzerland, Tel.: +41 223827238, Fax: +41 223827245, E-mail:
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How similar are the mice to men? Between-species comparison of left ventricular mechanics using strain imaging. PLoS One 2012; 7:e40061. [PMID: 22768220 PMCID: PMC3386935 DOI: 10.1371/journal.pone.0040061] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Accepted: 05/31/2012] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND While mammalian heart size maintains constant proportion to whole body size, scaling of left ventricular (LV) function parameters shows a more complex scaling pattern. We used 2-D speckle tracking strain imaging to determine whether LV myocardial strains and strain rates scale to heart size. METHODS We studied 18 mice, 15 rats, 6 rabbits, 12 dogs and 20 human volunteers by 2-D echocardiography. Relationship between longitudinal or circumferential strains/strain rates (S(Long)/SR(Long), S(Circ)/SR(Circ)), and LV end-diastolic volume (EDV) or mass were assessed by the allometric (power-law) equation Y = kM(β). RESULTS Mean LV mass in individual species varied from 0.038 to 134 g, LV EDV varied from 0.015 to 102 ml, while RR interval varied from 81 to 1090 ms. While S(Long) increased with increasing LV EDV or mass (β values 0.047±0.006 and 0.051±0.005, p<0.0001 vs. 0 for both) S(Circ) was unchanged (p = NS for both LV EDV or mass). Systolic and diastolic SR(Long) and SR(Circ) showed inverse correlations to LV EDV or mass (p<0.0001 vs. 0 for all comparisons). The ratio between S(Long) and S(Circ) increased with increasing values of LV EDV or mass (β values 0.039±0.010 and 0.040±0.011, p>0.0003 for both). CONCLUSIONS While S(Circ) is unchanged, S(Long) increases with increasing heart size, indicating that large mammals rely more on long axis contribution to systolic function. SR(Long) and SR(Circ), both diastolic and systolic, show an expected decrease with increasing heart size.
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