Refuting misconceptions in medical physiology.

BACKGROUND: In medical physiology, educators and students face a serious challenge termed misconceptions. Misconceptions are incorrect ideas that do not match current scientific views. Accordingly, they have shown to hamper teaching and learning of physiological concepts. Conceptual Change Theory forms the basis of new teaching and learning practices that may alleviate misconceptions and facilitate critical thinking skills that are essential in becoming knowledgeable, self-regulated health professionals. In this study, we examined if such an intervention named refutation texts, could enhance medical students' cognition and metacognition. METHODS: First-year medical students (N = 161) performed a pre-test and post-test on cardiovascular physiology concepts, including a self-perceived confidence rating. In between, students read either a standard text with an explanation of the correct answer, or a refutation text which additionally refuted related misconceptions. RESULTS: In both groups, average performance scores (refutation: + 22.5%, standard: + 22.8%) and overall confidence ratings (refutation: Δ0.42 out of 5, standard: Δ0.35 out of 5) increased significantly (all p < .001), but a significant effect of the specific refutation element was not found. Initially incorrect answers were corrected less frequently in cases of high confidence (35.8%) than low confidence (61.4%). CONCLUSIONS: Our results showed that refutation texts significantly increased students' knowledge, however, the refutation element did not have a significant additional effect. Furthermore, high confidence in incorrect answers negatively affected the likelihood of correction. These findings provide implications for teaching practices on concept learning, by showing that educators should take into account the key role of metacognition, and the nature of misconceptions.

Autologous Mesenchymal Stem Cells Show More Benefit on Systolic Function Compared to Bone Marrow Mononuclear Cells in a Porcine Model of Chronic Myocardial Infarction.

Cardiac cell therapy is a strategy to treat patients with chronic myocardial infarction (MI). No consensus exists regarding the optimal cell type. First, a comparison between autologous bone marrow-derived mononuclear cells (BMMNC) and mesenchymal stem cells (MSC) on therapeutic efficacy after MI was performed. Next, the effect of repetitive, NOGA-guided transendocardial injection was determined via a crossover design. Nineteen pigs were allocated in three groups: (1) placebo (at 4 and 8 weeks), (2) MSC (followed by placebo at 8 weeks), or (3) BMMNC (followed by MSC at 8 weeks) delivery including a priming strategy to enhance MSC effect. At 4 weeks, ejection fraction (EF) was significantly improved after MSC injection and not by BMMNC injection. After 8 weeks, no difference was observed in EF between cell-treated groups demonstrating the positive systolic effect of MSC. This study showed that MSC rather than BMMNC injection improves systolic function in chronic MI.

Mild hypothermia induces incomplete left ventricular relaxation despite spontaneous bradycardia in pigs.

AIM: Mild hypothermia (MH) decreases left ventricular (LV) end-diastolic capacitance. We sought to clarify whether this results from incomplete relaxation. METHODS: Ten anaesthetized pigs were cooled from normothermia (NT, 38 °C) to MH (33 °C). LV end-diastolic pressure (LVPed), volume (LVVed) and pressure-volume relationships (EDPVRs) were determined during stepwise right atrial pacing. LV capacitance (i.e. LVVed at LVPed of 10 mmHg, LV VPed10) was derived from the EDPVR. Pacing-induced changes of diastolic indices (LVPed, LVVed and LV VPed10) were analysed as a function of (i) heart rate and (ii) the ratio between diastolic time interval (t-dia) and LV isovolumic relaxation constant τ, which was calculated using a logistic fit (τL ) and monoexponential fit with zero asymptote (τZ ) and nonzero asymptote (τNZ ). RESULTS: Mild hypothermia decreased heart rate (85 ± 4 to 68 ± 3 bpm), increased τL (22 ± 1 to 57 ± 4 ms), τZ (26 ± 2 to 56 ± 5 ms) and τNZ (41 ± 1 to 96 ± 5 ms), decreased t-dia/τ ratios, and shifted the EDPVR leftwards compared to NT (all P < 0.05). During NT, pacing at ≥140 bpm shifted the EDPVR progressively leftwards. During MH, relationships between diastolic indices and heart rate were shifted towards lower heart rates compared to NT. However, relationships between diastolic indices and t-dia/τ during NT and MH were superimposable. CONCLUSION: We conclude that the loss of LV end-diastolic capacitance during MH can be explained at least in part by slowed LV relaxation. MH thereby is an example of incomplete LV relaxation at a spontaneous low heart rate. Caution may be advised, when heart rate is increased in patients treated with MH.

RP105 deficiency aggravates cardiac dysfunction after myocardial infarction in mice.

BACKGROUND: Toll-like receptor-4 (TLR4), a receptor of the innate immune system, is suggested to have detrimental effects on cardiac function after myocardial infarction (MI). RP105 (CD180) is a TLR4 homolog lacking the intracellular signaling domain that competitively inhibits TLR4-signaling. Thus, we hypothesized that RP105 deficiency, by amplifying TLR4 signaling, would lead to aggravated cardiac dysfunction after MI. METHODS AND RESULTS: First, whole blood from RP105-/- and wild-type (WT) male C57Bl/6N mice was stimulated with LPS, which induced a strong inflammatory TNFα response in RP105-/- mice. Then, baseline heart function was assessed by left ventricular pressure-volume relationships which were not different between RP105-/- and WT mice. Permanent ligation of the left anterior descending coronary artery was performed to induce MI. Infarct sizes were analyzed by (immuno)histology and did not differ. Fifteen days post MI heart function was assessed and RP105-/- mice had significantly higher heart rate (+21%, P<0.01), end systolic volume index (+57%, P<0.05), end systolic pressure (+22%, P<0.05) and lower relaxation time constant tau (-12%, P<0.05), and a tendency for increased end diastolic volume index (+42%, P<0.06), compared to WT mice. In the area adjacent to the infarct zone, compared to the healthy myocardium, levels of RP105, TLR4 and the endogenous TLR4 ligand fibronectin-EDA were increased as well as the number of macrophages, however this was not different between both groups. CONCLUSION: Deficiency of the endogenous TLR4 inhibitor RP105 leads to an enhanced inflammatory status and more pronounced cardiac dilatation after induction of MI, underscoring the role of the TLR4 pathway in post-infarction remodeling.

Xenon is not superior to isoflurane on cardiovascular function during experimental acute pulmonary hypertension.

BACKGROUND: Acute right ventricular afterload increase is a known perioperative challenge for the anaesthetic regime especially for patients with a compromised right ventricle. The accused negative inotropic action of volatile anaesthetics, with the exception of xenon, might be crucial for the adaptation of the right ventricle. METHODS: Reversible pulmonary hypertension (mean pressure 40 mmHg) was induced by an infusion of the stable thromboxane A(2) analog U46619 in a porcine model (n = 35). The effects of 70 vol% xenon and 0.9 vol% isoflurane on biventricular function were studied by conductance catheter technique. Inflammation and myocardial injury was quantified using serum probes [tumour necrosis factor α (TNFα), interleukin 6 (IL-6), troponin] and myocardial tissue [B natriuretic peptide (BNP), TNFα, activated caspase 3] by enzyme-linked immunosorbance assays and reverse-transcription polymerase chain reaction. RESULTS: After wash in of xenon global haemodynamic parameters remained stable whereas isoflurane caused a systemic vasodilation. This led to a significant decrease in mean arterial pressure in the isoflurane group whereas cardiac output remained stable. Both substances did not alter the biventricular contractility nor did they induce changes in preload for both ventricles. Xenon led to an additional increase in right ventricular afterload, whereas isoflurane reduced pulmonary vascular resistance. No effects on systemic inflammatory response and myocardial injury were found, whereas higher apoptosis rate and expression of BNP and IL-6 was determined in the right ventricle. CONCLUSIONS: These results do not support the idea that xenon is more beneficial than isoflurane in right ventricular failure during pulmonary hypertension. Isoflurane did not compromise systolic ventricular function during acute PHT it only led to vasodilation in contrast to xenon.

The induction of mild hypothermia improves systolic function of the resuscitated porcine heart at no further sympathetic activation.

AIM: Mild hypothermia (MH) after cardiac arrest attenuates hypoxic brain injury and improves survival. As MH increases contractility in normal hearts, we hypothesized that MH improves cardiovascular function after cardiac arrest. METHODS: In 16 anaesthetized pigs (64 ± 2 kg), ventricular fibrillation was induced electrically for 5 min. At 10 min after resuscitation and return of spontaneous circulation (ROSC), pigs were assigned to normothermia (NT, 38°C, n = 8) or MH (33°C, n = 8, intravascular cooling). RESULTS: At ROSC 6 h vs. baseline, heart rate (HR) was unchanged in NT, but decreased in MH. Cardiac output (CO, l min(-1)) decreased in MH (3.5 ± 0.2 vs. 5.5 ± 0.4, P < 0.05) more than in NT (4.8 ± 0.4 vs. 5.7 ± 0.4, P = ns). Mixed venous oxygen saturation decreased in NT (56 ± 2 vs. 66 ± 3%, P < 0.05), but remained constant in MH (64 ± 2 vs. 65 ± 2%) due to a 35% decrease of whole body oxygen consumption. Left ventricular (LV) dP/dt(max) (mmHg s(-1)) decreased in NT (1163 ± 97 vs. 1665 ± 134, P < 0.05), but was preserved in MH (1602 ± 102 vs. 1603 ± 96), whereas LV relaxation was profoundly slowed during MH. Pressure-volume analysis confirmed improved LV systolic function during MH, but also demonstrated decreased LV end-diastolic distensibility, which was further potentiated by right atrial pacing at baseline HR. MH did not increase plasma catecholamine levels. Spectral analysis of heart rate variability revealed reduced sympathetic activation during MH. CONCLUSION: The induction of MH after cardiac resuscitation improves systolic myocardial function without further sympathetic activation. A reduced metabolism during MH outweighs a decreased CO and thereby acts favourably on systemic oxygen supply/demand balance.

Novel approaches to treat experimental pulmonary arterial hypertension: a review.

BACKGROUND: Pulmonary arterial hypertension (PAH) is a life-threatening disease characterized by an increase in pulmonary artery pressure leading to right ventricular (RV) hypertrophy, RV failure, and ultimately death. Current treatments can improve symptoms and reduce severity of the hemodynamic disorder but gradual deterioration in their condition often necessitates a lung transplant. METHODS AND RESULTS: In experimental models of PAH, particularly the model of monocrotaline-induced pulmonary hypertension, efficacious treatment options tested so far include a spectrum of pharmacologic agents with actions such as anti-mitogenic, proendothelial function, proangiogenic, antiinflammatory and antioxidative. Emerging trends in PAH treatment are gene and cell therapy and their combination, like (progenitor) cells enriched with eNOS or VEGF gene. More animal data should be collected to investigate optimal cell type, in vitro cell transduction, route of administration, and number of cells to inject. Several recently discovered and experimentally tested interventions bear potential for therapeutic purposes in humans or have been shown already to be effective in PAH patients leading to improved life expectation and better quality of life. CONCLUSION: Since many patients remain symptomatic despite therapy, we should encourage research in animal models of PAH and implement promising treatments in homogeneous groups of PAH patients.

Cardiac function during mild hypothermia in pigs: increased inotropy at the expense of diastolic dysfunction.

AIM: The induction of mild hypothermia (MH; 33 degrees C) has become the guideline therapy to attenuate hypoxic brain injury after out-of-hospital cardiopulmonary resuscitation. While MH exerts a positive inotropic effect in vitro, MH reduces cardiac output in vivo and is thus discussed critically when severe cardiac dysfunction is present in patients. We thus assessed the effect of MH on the function of the normal heart in an in vivo model closely mimicking the clinical setting. METHODS: Ten anaesthetized, female human-sized pigs were acutely catheterized for measurement of pressure-volume loops (conductance catheter), cardiac output (Swan-Ganz catheter) and for vena cava inferior occlusion. Controlled MH (from 37 to 33 degrees C) was induced by a vena cava inferior cooling catheter. RESULTS: With MH, heart rate (HR) and whole body oxygen consumption decreased, while lactate levels remained normal. Cardiac output, left ventricular (LV) volumes, peak systolic and end-diastolic pressure and dP/dt(max) did not change significantly. Changes in dP/dt(min) and the time constant of isovolumetric relaxation demonstrated impaired active relaxation. In addition, MH prolonged the systolic and shortened the diastolic time interval. Pressure-volume analysis revealed increased end-systolic and end-diastolic stiffness, indicating positive inotropy and reduced end-diastolic distensibility. Positive inotropy was preserved during pacing, while LV end-diastolic pressure increased and diastolic filling was substantially impaired due to delayed LV relaxation. CONCLUSION: MH negatively affects diastolic function, which, however, is compensated for by decreased spontaneous HR. Positive inotropy and a decrease in whole body oxygen consumption warrant further studies addressing the potential benefit of MH on the acutely failing heart.

Xenon and isoflurane improved biventricular function during right ventricular ischemia and reperfusion.

BACKGROUND: Although anesthetics have some cardioprotective properties, these benefits are often counterbalanced by their negative inotropic effects. Xenon, on the other hand, does not influence myocardial contractility. Thus, xenon may be a superior treatment for the maintenance of global hemodynamics, especially during right ventricular ischemia, which is generally characterized by a high acute complication rate. METHODS: The effects of 70 vol% xenon and 0.9 vol% isoflurane on biventricular function were assessed in a porcine model (n=36) using the conductance catheter technique, and the expression of the type B natriuretic peptide (BNP) gene was measured. The animals underwent 90 min of right ventricular ischemia followed by 120 min of reperfusion. A barbiturate-anesthetized group was included as a control. RESULTS: Cardiac output was compromised in unprotected animals during ischemia by 33+/-18% and during reperfusion by 53+/-17%. This was mainly due to impaired contractility in the left ventricle (LV) and increased stiffness. Isoflurane attenuated the increase in stiffness and resulted in a higher preload. In contrast, xenon increased the right ventricular afterload, which was compensated by an increase in contractility. Its effects on diastolic function were less pronounced. Upregulation of BNP mRNA expression was impeded in the remote area of the LV by both isoflurane and xenon. CONCLUSIONS: Xenon and isoflurane demonstrated equipotent effects in preventing the hemodynamic compromise that is induced by right ventricular ischemia and reperfusion, although they acted through somewhat differential inotropic and vasodilatory effects.

Single-beat estimation of the left ventricular end-systolic pressure-volume relationship in patients with heart failure.

AIM: The end-systolic pressure-volume relationship (ESPVR) constructed from multiple pressure-volume (PV) loops acquired during load intervention is an established method to asses left ventricular (LV) contractility. We tested the accuracy of simplified single-beat (SB) ESPVR estimation in patients with severe heart failure. METHODS: Nineteen heart failure patients (NYHA III-IV) scheduled for surgical ventricular restoration and/or restrictive mitral annuloplasty and 12 patients with normal LV function scheduled for coronary artery bypass grafting were included. PV signals were obtained before and after cardiac surgery by pressure-conductance catheters and gradual pre-load reductions by vena cava occlusion (VCO). The SB method was applied to the first beat of the VCO run. Accuracy was quantified by the root-mean-square-error (RMSE) between ESPVR(SB) and gold-standard ESPVR(VCO). In addition, we compared slopes (E(ES)) and intercepts (end-systolic volume at multiple pressure levels (70-100 mmHg: ESV(70)-ESV(100)) of ESPVR(SB) vs. ESPVR(VCO) by Bland-Altman analyses. RESULTS: RMSE was 1.7 + or - 1.0 mmHg and was not significantly different between groups and not dependent on end-diastolic volume, indicating equal, high accuracy over a wide volume range. SB-predicted E(ES) had a bias of -0.39 mmHg mL(-1) and limits of agreement (LoA) -2.0 to +1.2 mmHg mL(-1). SB-predicted ESVs at each pressure level showed small bias (range: -10.8 to +9.4 mL) and narrow LoA. Two-way anova indicated that differences between groups were not dependent on the method. CONCLUSION: Our findings, obtained in hearts spanning a wide range of sizes and conditions, support the use of the SB method. This method ultimately facilitates less invasive ESPVR estimation, particularly when coupled with emerging noninvasive techniques to measure LV pressures and volumes.

Anti-ischemic effects of inotropic agents in experimental right ventricular infarction.

BACKGROUND: Right ventricular (RV) function is an important determinant of survival after myocardial infarction. The efficacy of reperfusion therapy might be increased by the cardioprotective action of inotropic agents, which are used for symptomatic therapy in situations with compromised hemodynamics. Therefore, we used a porcine model of RV ischemia and reperfusion (IR) injury to study the influence of milrinone, levosimendan and dobutamine on the extent and degree of myocardial injury. METHODS: IR injury was induced by temporary ligation of the distal right coronary artery for 90 min, followed by 120 min of reperfusion. Treatment was initiated 30 min after coronary artery occlusion. A bolus of milrinone (n=12; 50 microg/kg) and levosimendan (n=10; 24 microg/kg) was applied in different groups, followed by continuous infusion of the drugs at 0.5 and 0.2 microg/kg/min, respectively. The effects on myocardial injury and inflammation were compared with a control (n=12) and a dobutamine group (n=10), where treatment was started with an infusion of 5 microg/kg/min. RESULTS: Milrinone and levosimendan reduced the resulting infarct size with respect to the area at risk (41.7+/-10.2%, 45.7+/-8.1%) when compared with the control group (58.3+/-6.1%). In contrast, dobutamine had no effect (55.8+/-7.7%). All drugs reduced the number of neutrophils infiltrating into the different myocardial regions and the circulating levels of interleukin-6. Increased levels of tumor necrosis factor alpha during reperfusion were only abated by milrinone and levosimendan. CONCLUSIONS: Cardioprotective properties of milrinone and levosimendan were demonstrated for the first time in a clinically relevant model of RV infarction.

Left ventricular mechanical dyssynchrony is load independent at rest and during endotoxaemia in a porcine model.

AIM: In diseased or injured states, the left ventricle displays higher degrees of mechanical dyssynchrony. We aimed at assessing mechanical dyssynchrony ranges in health related to variation in load as well as during acute endotoxin-induced ventricular injury. METHODS: In 16 juvenile anaesthetized pigs, a five-segment conductance catheter was placed in the left ventricle as well as a balloon-tipped catheter in the inferior vena cava. Mechanical dyssynchrony during systole, including dyssynchrony time in per cent during systole and internal flow fraction during systole, were measured at rest and during controlled pre-load reduction sequences, as well as during 3 h of endotoxin infusion (0.25 microg kg(-)1 h(-1)). RESULTS: Systolic dyssynchrony and internal flow fraction did not change during the course of acute beat-to-beat pre-load alteration. Endotoxin-produced acute pulmonary hypertension by left ventricular dyssynchrony measures was not changed during the early peak of pulmonary hypertension. Endotoxin ventricular injury led to progressive increases in systolic mechanical segmental dyssynchrony (7.9 +/- 1.2-13.0 +/- 1.3%) and ventricular systolic internal flow fraction (7.1 +/- 2.4-16.6 +/- 2.8%), respectively for baseline and then at hour 3. There was no localization of dyssynchrony changes to segment or region in the ventricular long axis during endotoxin infusion. CONCLUSION: These results suggest that systolic mechanical dyssynchrony measures may be load independent in health and during acute global ventricular injury by endotoxin. More study is needed to validate ranges in health and disease for parameters of mechanical dyssynchrony.

Establishment of a porcine right ventricular infarction model for cardioprotective actions of xenon and isoflurane.

BACKGROUND: Right ventricular (RV) function is an important determinant of post-operative outcome. Consequences of RV infarction might be limited by pre-conditioning with volatile anesthetic drugs. Therefore, we used a porcine model of RV ischemia and reperfusion (IR) injury to study the influence of isoflurane and xenon on the extent and degree of myocardial injury. METHODS: IR injury was induced by a 90-min ligation of the distal right coronary artery and 120-min reperfusion in thiopental anesthetized pigs. A control group (n=12) was compared with two groups, which received either 0.55 minimum alveolar concentration (MAC) isoflurane (n=10) or xenon (n=12) starting 60 min before ischemia. Myocardial injury was described by three criteria: the infarct size related to area at risk (IS/AAR), the infiltration of neutrophils as determined by myeloperoxidase (MPO) activity, and the plasma levels of tumor necrosis factor alpha (TNFalpha), interleukin 6 (IL-6), myoglobin and troponin-T (TnT). RESULTS: IS/AAR was reduced from 58.3+/-6.2% in the control group to 41.8+/-7.8% after isoflurane and 42.7+/-8.5% after xenon pre-treatment, which equals an absolute reduction of 16.5% [95% confidence interval (CI): 10.9-22.1] and 15.5% (95% CI: 10.1-20.9). The maximum increase of TnT could be observed within the xenon group. Both treatment groups were characterized by lower MPO activity, in the infarct and periinfarct region and lower plasma concentrations of TNFalpha and IL-6. CONCLUSIONS: It could be demonstrated for the first time in a model of RV infarction that the continuous application of isoflurane or xenon before, during and after ischemia reduced the extent (size) and severity (inflammation) of myocardial injury.

Acute effects of alcohol septal ablation on systolic and diastolic left ventricular function in patients with hypertrophic obstructive cardiomyopathy.

OBJECTIVE: Hypertrophic obstructive cardiomyopathy (HOCM) often leads to heart failure, severe symptoms and death. Percutaneous transluminal septal myocardial ablation (PTSMA) by alcohol injection efficiently reduces left ventricular (LV) outflow tract pressure gradient and improves symptoms. We determined acute changes in haemodynamics and systolic and diastolic LV function after PTSMA. METHODS: In 17 consecutive patients with symptomatic HOCM referred for PTSMA, the target vessel was determined by myocardial contrast transthoracic echocardiography. An over-the-wire balloon was inflated in the target vessel and multiple 0.5-ml alcohol injections were performed. LV systolic and diastolic function was assessed by online pressure-volume loops obtained by conductance catheter at baseline and acutely after the procedure. RESULTS: In all patients except two, a single septal branch was treated using a total of 2.0 (0.5) ml ethanol per patient. The rest and post-extrasystolic gradient were significantly decreased after PTSMA (79 (38) to 14 (16) mm Hg and 130 (50) to 34 (33) mm Hg, respectively, both p<0.001). Ejection fraction decreased (78% (9%) to 67% (13%), p<0.001). Cardiac output, heart rate and stroke work were unchanged, but systolic and diastolic volume increased. End-systolic and end-diastolic pressure significantly decreased (166 (27) to 129 (26) mm Hg, p<0.001 and 25 (6) to 21 (7) mm Hg, p = 0.049, respectively). Significant rightward shift (p<0.001) and decreased slope (p = 0.041) of the end-systolic pressure-volume relation indicated reduced contractility, whereas diastolic stiffness, -dP/dt(MIN), and tau were significantly improved after the procedure. CONCLUSIONS: PTSMA acutely reduced systolic function but promptly improved diastolic function with maintained cardiac output and stroke work. Improved diastolic function and increased end-diastolic volume compensated for the systolic loss and resulted in maintained haemodynamics.

Left ventricular function in the post-infarct failing mouse heart by magnetic resonance imaging and conductance catheter: a comparative analysis.

AIM: Murine myocardial infarction (MI) models are increasingly used in heart failure studies. Magnetic resonance imaging (MRI) and pressure-volume loops by conductance catheter (CC) enable physiological phenotyping. We performed a comparative analysis of MRI vs. CC to assess left ventricular (LV) function in the failing mouse heart. METHODS: MI was created by LAD ligation. MRI (day 14) and CC (day 15) were used to determine LV end-diastolic volume (EDV), end-systolic volume (ESV) and ejection fraction (EF). RESULTS: Pooled data yielded moderate-to-strong linear correlations: EDV: R = 0.61; ESV: R = 0.72; EF: R = 0.81. We analysed three groups, no MI (sham, n = 10), small MI (<30% of LV, n = 14) and large MI (>30%, n = 20). Volumes and EF were consistently lower by CC than by MRI, but group differences were evident for both techniques. Receiver-operating characteristic analysis indicated good sensitivity and specificity for both techniques, with superior results for MRI. CONCLUSIONS: CC and MRI are highly valuable for evaluation of LV volume and function. MRI is recommended for longitudinal studies, accurate absolute volumes and anatomical information. Unique features of CC are its online signal with high temporal resolution, and advanced analysis of LV function and energetics.

Systolic and diastolic ventricular function in the normal and extra-embryonic venous clipped chicken embryo of stage 24: a pressure-volume loop assessment.

OBJECTIVES: Fluid mechanical forces affect cardiac development. In the chicken embryo, permanent obstruction of the right lateral vitelline vein by clipping reduces the mechanical load on the embryonic myocardium, which has been shown to induce a spectrum of outflow tract anomalies. Insight into the effects of this intervention on the mechanical function of the developing myocardium could contribute to a better understanding of the relationship between hemodynamics and cardiac morphogenesis. We aimed to explore the effects of clipping on intrinsic systolic and diastolic ventricular function at stage 24 in the chicken embryo METHODS: Cardiac pressure-volume relationships enable load-independent quantification of intrinsic ventricular systolic and diastolic properties. We determined ventricular function by pressure-volume loop analysis of in-ovo stage-24 chicken embryos (n = 15) 2 days after venous obstruction at 2.5 days of incubation (stage 17, venous clipped embryos). Control embryos (n = 15) were used for comparison. RESULTS: End-systolic volume was significantly higher in clipped embryos (0.36 +/- 0.02 microL vs. 0.29 +/- 0.02 microL, P = 0.002). End-systolic and end-diastolic pressure were also increased compared with control animals (2.93 +/- 0.07 mmHg vs. 2.70 +/- 0.08 mmHg, P = 0.036 and 1.15 +/- 0.06 mmHg vs. 0.82 +/- 0.05 mmHg, P < 0.001, respectively). No significant differences were demonstrated for other baseline hemodynamic parameters. Analysis of pressure-volume relationships showed a significantly lower end-systolic elastance in the clipped embryos (slope of end-systolic pressure-volume relationship: 2.91 +/- 0.24 mmHg/microL vs. 7.53 +/- 0.66 mmHg/microL, P < 0.005) indicating reduced contractility. Diastolic stiffness was significantly increased in the clipped embryos (slope of end-diastolic pressure-volume relationship: 1.54 +/- 0.21 vs. 0.60 +/- 0.08, P < 0.005), indicating reduced compliance. CONCLUSION: Venous obstruction apparently interferes with normal myocardial development, resulting in impaired intrinsic systolic and diastolic ventricular function. These changes in ventricular function may precede morphological derangements observed in later developmental stages.

Preservation of left ventricular function and attenuation of remodeling after transplantation of human epicardium-derived cells into the infarcted mouse heart.

BACKGROUND: Proper development of compact myocardium, coronary vessels, and Purkinje fibers depends on the presence of epicardium-derived cells (EPDCs) in embryonic myocardium. We hypothesized that adult human EPDCs might partly reactivate their embryonic program when transplanted into ischemic myocardium and improve cardiac performance after myocardial infarction. METHODS AND RESULTS: EPDCs were isolated from human adult atrial tissue. Myocardial infarction was created in immunodeficient mice, followed by intramyocardial injection of 4x10(5) enhanced green fluorescent protein-labeled EPDCs (2-week survival, n=22; 6-week survival, n=15) or culture medium (n=24 and n=18, respectively). Left ventricular function was assessed with a 9.4T animal MRI unit. Ejection fraction was similar between groups on day 2 but was significantly higher in the EPDC-injected group at 2 weeks (short term), as well as after long-term survival at 6 weeks. End-systolic and end-diastolic volumes were significantly smaller in the EPDC-injected group than in the medium-injected group at all ages evaluated. At 2 weeks, vascularization was significantly increased in the EPDC-treated group, as was wall thickness, a development that might be explained by augmented DNA-damage repair activity in the infarcted area. Immunohistochemical analysis showed massive engraftment of injected EPDCs at 2 weeks, with expression of alpha-smooth muscle actin, von Willebrand factor, sarcoplasmic reticulum Ca2+-ATPase, and voltage-gated sodium channel (alpha-subunit; SCN5a). EPDCs were negative for cardiomyocyte markers. At 6-weeks survival, wall thickness was still increased, but only a few EPDCs could be detected. CONCLUSIONS: After transplantation into ischemic myocardium, adult human EPDCs preserve cardiac function and attenuate ventricular remodeling. Autologous human EPDCs are promising candidates for clinical application in infarcted hearts.