scholarly journals Evolution of scar structure, mechanics, and ventricular function after myocardial infarction in the rat

2010 ◽  
Vol 298 (1) ◽  
pp. H221-H228 ◽  
Author(s):  
Gregory M. Fomovsky ◽  
Jeffrey W. Holmes
Keyword(s):  
Myocardial Infarction ◽  
Mechanical Properties ◽  
Ventricular Function ◽  
Heart Function ◽  
Systolic Pressure ◽  
Left Ventricular ◽  
Collagen Content ◽  
Lv Function ◽  
Large Animal ◽  
Large Animal Models

The mechanical properties of the healing scar are an important determinant of heart function following myocardial infarction. Yet the relationship between scar structure, scar mechanics, and ventricular function remains poorly understood, in part because no published study has tracked all of these factors simultaneously in any animal model. We therefore studied the temporal evolution of scar structure, scar mechanics, and left ventricular (LV) function in large anterior myocardial infarcts in rats. At 1, 2, 3, and 6 wk after left anterior descending coronary ligation, we examined LV function using sonomicrometry, infarct mechanical properties using biaxial mechanical testing, infarct structure using polarized light microscopy, and scar collagen content and cross-linking using biochemical assays. Healing infarcts in the rat were structurally and mechanically isotropic at all time points. Collagen content increased with time and was the primary determinant of scar mechanical properties. The presence of healing infarcts influenced systolic LV function through a rightward shift of the end-systolic pressure-volume relationship (ESPVR) that depended on infarct size, infarct collagen content, and LV dilation. We conclude that in sharp contrast to previous reports in large animal models, healing infarcts are structurally and mechanically isotropic in the standard rat model of myocardial infarction. On the basis of the regional strain patterns we observed in healing rat infarcts in this study and in healing pig infarcts in previous studies, we hypothesize that the local pattern of stretching determines collagen alignment in healing myocardial infarct scars.

Evolution of Scar Mechanical Properties During Myocardial Infarct Healing in Rat

2007 ◽  
Author(s):  
Gregory M. Fomovsky ◽  
Jeffrey W. Holmes
Keyword(s):  
Myocardial Infarction ◽  
Mechanical Properties ◽  
Rat Model ◽  
Important Determinant ◽  
Myocardial Infarct ◽  
Left Ventricular ◽  
Lv Function ◽  
Large Animal ◽  
Lv Dysfunction ◽  
Infarct Healing

The mechanics of healing myocardial infarcts are an important determinant of post-infarction left ventricular (LV) function and remodeling. Large animal infarct models are well studied; healing infarct scars have been shown to be mechanically and structurally anisotropic [1], and this anisotropy may help preserve LV function during some stages of healing [2]. At the same time, it has been suggested that the rat model of myocardial infarction is more similar to humans in the range of infarct sizes and observed LV dysfunction [3]. However, in the rat model, infarct mechanics and their effect on the overall LV function have not been described so far.

Abstract 562: Improvement In Left Ventricular Function Due To A Reduction Of Myocardial Fibrosis Following Myocardial Infarction Using A Purpose Designed Novel Anti Fibrotic Drug FT-011

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Maros Elsik ◽  
Yuan Zhang ◽  
Bing Wang ◽  
Andrew Kompa ◽  
Richard Gilbert ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Angiotensin Ii ◽  
Ventricular Function ◽  
Collagen Synthesis ◽  
Heart Function ◽  
Systolic Function ◽  
Weight Ratio ◽  
Left Ventricular ◽  
Lv Function ◽  
Post Surgery

Introduction: Following myocardial infarction (MI), pathological deposition of excess collagen adversely effects cardiac function. We evaluated the role of a novel anti-fibrotic drug FT-011 (Fibrotech, Australia) in preventing fibrosis and preserving ventricular function. Methods : To first test for anti-fibrotic effects, isolated rat neonatal cardiac fibroblasts were stimulated with angiotensin II (AII)(0.1 μmol/L) or TGF-ß(10ng/ml) and treated with FT-011 (30–200 μmol/L) alone or in combination with the angiotensin II antagonist irbesartan (Irb)(10 −5 -10 −7 mmol/l). Effects on collagen synthesis were assessed by 3 H-proline incorporation. Subsequently, ten week old Sprague Dawley rats underwent LAD artery ligation to induce MI (or sham procedure), then treatment for 4 weeks with FT-011(200 mg/kg/d) or vehicle, starting 1 week post surgery. Left ventricular (LV) function was assessed by echocardiography (day 2 and 35 post-surgery) and cardiac catheterization (day 35). Total collagen (TC) deposition (by picrosirius red staining) and collagen subtypes I and III (C-I, C-III, by immunohistochemistry) were assessed. Results: A dose dependent reduction of collagen synthesis with FT-011 in response to both AII or TGF-ß stimulation (p<0.01), and a further reduction with FT-011±Irb was observed in vitro. In vivo, MIs were of comparable size. Treatment with FT-011 significantly reduced TC, C-I and C-III (p<0.05) in the myocardium, resulting in improved LV systolic function, normalization of diastolic function parameters (Table ) and improvement in heart failure with a reduction in lung/body weight ratio with FT-011 (p<0.05). Table: 35 day data [mean (SEM)]. Conclusion: Post MI treatment with FT-011 improved heart function by reducing pathological remodeling of the ventricle. This appears to be occurring at least in part via a direct anti-fibrotic effect of the drug.

Myocardial T2* Is Not Affected by the Structural Effects of Myocardial Fibrosis, Ageing or Impaired Left Ventricular Function.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 1675-1675
Author(s):  
Paul Kirk ◽  
Dudley J. Pennell
Keyword(s):  
Myocardial Infarction ◽  
Iron Overload ◽  
Left Ventricular Function ◽  
Ventricular Function ◽  
Age Distribution ◽  
Left Ventricular ◽  
Lv Function ◽  
Chronic Myocardial Infarction ◽  
Myocardial Iron ◽  
The Mean

Abstract Background The myocardial T2* technique has been validated as a reproducible non-invasive measurement of myocardial iron load and is now widely used for measurement of myocardial iron in iron overload diseases such as thalassaemia. The reduction in myocardial T2* seen in iron overload conditions is substantially greater than is seen in any other clinical circumstance, but there has been no direct comparison of myocardial T2* in normals and other conditions such as increasing age, myocardial infarction or impairment in left ventricular function. We aimed therefore to compare the findings in patients affected by these conditions with normals. Method A total of 38 patients in total were scanned using the myocardial T2* technique. Fifteen patients had normal hearts, 18 had impaired LV function and 6 had chronic myocardial infarction affecting the anteroseptal wall, where myocardial T2* measurements are normally made. Results The mean myocardial T2* in normals was 36.0 +/− 6.4 ms, yielding a lower limit of normal of 23ms. In patients with impaired LV function, the mean myocardial T2* was 39.0 +/− 11.7ms (p= 0.37 vs normals). In patients with anteroseptal myocardial infarction, the mean myocardial T2* was 34.7ms +/− 3.9ms (p= 0.64 vs normals). The frequency distribution of the myocardial T2* values are shown in figure 1. These approximate to normal, and are very similar in distribution. In addition, the age distribution of myocardial T2* in the 15 normals is shown in figure 2. There was no significant relation between myocardial T2* and age (r2 = 0.066, p=0.82). Conclusion There is no significant reduction in myocardial T2* associated with fibrosis from chronic myocardial infarction, impairment of left ventricular function, or increasing age. This suggests that structural changes associated with remodelling, infarction and fibrosis, and ageing do not have significant effects on the absolute measure of myocardial T2*, and in particular do not cause a reduction below 20ms as is seen in myocardial overload conditions. Thus these date suggest that myocardial T2* is robust to these structural alterations, and that myocardial iron overload can be ascertained from reduced myocardial T2* values, in a similar manner to that which can be achieved in normals. Figure 1 Figure 1. Figure 2 Figure 2.

scholarly journals Comparative Analysis of Methods to Induce Myocardial Infarction in a Closed-Chest Rabbit Model

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Marc-Antoine Isorni ◽  
Amaury Casanova ◽  
Julie Piquet ◽  
Valérie Bellamy ◽  
Charly Pignon ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Animal Models ◽  
Rabbit Model ◽  
Left Ventricular ◽  
Balloon Occlusion ◽  
Gelatin Sponge ◽  
Large Animal ◽  
Alcohol Injection ◽  
Closed Chest ◽  
Large Animal Models

Objective.To develop a rabbit model of closed-chest catheter-induced myocardial infarction.Background.Limitations of rodent and large animal models justify the search for clinically relevant alternatives.Methods.Microcatheterization of the heart was performed in 47 anesthetized 3-4 kg New Zealand rabbits to test five techniques of myocardial ischemia: free coils (n=4), interlocking coils (n=4), thrombogenic gelatin sponge (n=4), balloon occlusion (n=4), and alcohol injection (n=8). In order to limit ventricular fibrillation, an antiarrhythmic protocol was implemented, with beta-blockers/amiodarone before and xylocaine infusion during the procedure. Clinical, angiographic, and echographic data were gathered. End points included demonstration of vessel occlusion (TIMI flow grades 0 and 1 on the angiogram), impairment of left ventricular function at 2 weeks after procedure (by echocardiography), and pathologically confirmed myocardial infarction.Results.The best arterial access was determined to be through the right carotid artery. The internal mammary guiding catheter 4-Fr was selected as the optimal device for selective intracoronary injection. Free coils deployed prematurely and tended to prolapse into the aorta. Interlocking coils did not deploy completely and failed to provide reliable results. Gelatin sponge was difficult to handle, adhered to the catheter, and could not be clearly visualized by fluoroscopy. Balloon occlusion yielded inconsistent results. Alcohol injection was the most efficient and reproducible method for inducing myocardial infarction (4 out of 6 animals), the extent of which could be fine-tuned by using a coaxial balloon catheter as a microcatheter (0.52 mm) to achieve a superselective injection of 0.2 mL of alcohol. This approach resulted in a 20% decrease in LVEF and infarcted myocardium was confirmed histologically.Conclusions.By following a stepwise approach, a minimally invasive, effective, and reproducible rabbit model of catheter-induced myocardial infarction has been developed which addresses the limitations of rodent experiments while avoiding the logistical and cost issues associated with large animal models.

Impact of exercise training on ventricular properties in a canine model of congestive heart failure

1997 ◽  
Vol 272 (3) ◽  
pp. H1382-H1390 ◽  
Author(s):  
K. Todaka ◽  
J. Wang ◽  
G. H. Yi ◽  
M. Knecht ◽  
R. Stennett ◽  
...  
Keyword(s):  
Heart Failure ◽  
Exercise Training ◽  
Heart Function ◽  
Systolic Pressure ◽  
Cardiac Pacing ◽  
Left Ventricular ◽  
Lv Function ◽  
Myocardial Stiffness

Exercise training improves functional class in patients with chronic heart failure (CHF) via effects on the periphery with no previously documented effect on intrinsic left ventricular (LV) properties. However, because methods used to evaluate in vivo LV function are limited, it is possible that some effects of exercise training on the failing heart have thus far eluded detection. Twelve dogs were instrumented for cardiac pacing and hemodynamic recordings. Hearts were paced rapidly for 4 wk. Six of the dogs received daily treadmill exercise (CHF(EX), 4.4 km/h, 2 h/day) concurrent with rapid pacing, while the other dogs remained sedentary (CHFs). Hemodynamic measurements taken in vivo at the end of 4 wk revealed relative preservation of maximum rate of pressure rise (2,540 +/- 440 vs. 1,720 +/- 300 mmHg/s, P < 0.05) and LV end-diastolic pressure (9 +/- 5 vs. 19 +/- 4 mmHg, P < 0.05) in CHF(EX) compared with CHFs. The hearts were then isolated and cross perfused for in vitro measurement of isovolumic pressure-volume relations; these results were compared with those of six normal dogs (N). Systolic function was similarly depressed in both groups of pacing animals [end-systolic elastance (Ees) values of 1.66 +/- 0.47 in CHFs, 1.77 +/- 0.38 in CHF(EX), and 3.05 +/- 0.81 mmHg/ml in N, with no changes in volume axis interceptors of the end-systolic pressure-volume relationship]. The diastolic myocardial stiffness constant, k, was elevated in CHFs and was normalized by exercise training (32 +/- 3 in CHFs, 21 +/- 3 in CHF(EX), 20 +/- 4 in N). Thus daily exercise training preserved in vivo hemodynamics during 4 wk of rapid cardiac pacing and was accompanied by a significant change in diastolic myocardial stiffness in vitro. These findings suggest that changes in heart function may contribute to the overall beneficial hemodynamic effects of exercise training in CHF by a significant effect on diastolic properties.

scholarly journals Reperfused hemorrhagic myocardial infarction in rats

PLoS ONE ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. e0243207
Author(s):  
Anand R. Nair ◽  
Eric A. Johnson ◽  
Hsin-Jung Yang ◽  
Ivan Cokic ◽  
Joseph Francis ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Ventricular Remodeling ◽  
Ex Vivo ◽  
Left Ventricular ◽  
Major Adverse Cardiovascular Events ◽  
Large Animal ◽  
Ischemic Time ◽  
Rat Models ◽  
Large Animal Models ◽  
Gene And Protein Expression

Background Intramyocardial hemorrhage following reperfusion is strongly associated with major adverse cardiovascular events in myocardial infarction (MI) patients; yet the mechanisms contributing to these outcomes are not well understood. Large animal models have been used to investigate intramyocardial hemorrhage, but they are exorbitantly expensive and difficult to use for mechanistic studies. In contrast, rat models are widely used to investigate mechanistic aspects of cardiovascular physiology, but a rat model that consistently recapitulates the characteristics of an hemorrhagic MI does not exist. To bridge this gap, we investigated the physiological conditions of MI that would create intramyocardial hemorrhage in rats so that a reliable model of hemorrhagic MI would become available for basic research. Methods & results Sprague-Dawley rats underwent either a 90-minute (90-min) ischemia and then reperfusion (I/R) (n = 22) or 30-minute (30-min) I/R (n = 18) of the left anterior descending coronary artery. Sham rats (n = 12) were used as controls. 90-min I/R consistently yielded hemorrhagic MI, while 30-min I/R consistently yielded non-hemorrhagic MI. Twenty-four hours post-reperfusion, ex-vivo late-gadolinium-enhancement (LGE) and T2* cardiac MRI performed on excised hearts from 90-min I/R rats revealed colocalization of iron deposits within the scarred tissue; however, in 30-min I/R rats scar was evident on LGE but no evidence of iron was found on T2* CMR. Histological studies verified tissue damage (H&E) detected on LGE and the presence of iron (Perl’s stain) observed on T2*-CMR. At week 4 post-reperfusion, gene and protein expression of proinflammatory markers (TNF-α, IL-1β and MMP-9) were increased in the 90-min I/R group when compared to 30-min I/R groups. Further, transmission electron microscopy performed on 90-min I/R myocardium that were positive for iron on T2* CMR and Perl’s stain showed accumulation of granular iron particles within the phagosomes. Conclusion Ischemic time prior to reperfusion is a critical factor in determining whether a MI is hemorrhagic or non-hemorrhagic in rats. Specifically, a period of 90-min of ischemia prior to reperfusion can produce rat models of hemorrhagic MI, while 30-minutes of ischemia prior to reperfusion can ensure that the MIs are non-hemorrhagic. Hemorrhagic MIs in rats result in marked increase in iron deposition, proinflammatory burden and adverse left—ventricular remodeling compared to rats with non-hemorrhagic MIs.

Abstract 249: Chronic Neuregulin-1β Treatment Mitigates the Progression of Post-myocardial Infarction Heart Failure in the Setting of Type 1 Diabetes Mellitus

2017 ◽  
Vol 121 (suppl_1) ◽  
Author(s):  
Manisha Gupte ◽  
Hind Lal ◽  
Firdos Ahmad ◽  
Lin Zhong ◽  
Douglas B Sawyer ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Heart Failure ◽  
Type 1 Diabetes ◽  
Heart Function ◽  
Diabetic Rats ◽  
Left Ventricular ◽  
Lv Function ◽  
Coronary Artery Ligation ◽  
Artery Ligation

Aim: Neuregulin-1β (NRG-1β), a growth factor critical for cardiac development as well as maintenance of heart function after injury has been shown to significantly improve heart function in preclinical rodent models. Importantly, number of studies are ongoing to test the efficacy of NRG-1β as a treatment for patients with chronic heart failure. However, the efficacy of recombinant NRG-1β in a typ1 diabetic model of heart failure due to myocardial infarction (MI) has not been investigated. The aim of the present study was to determine the efficacy of exogenous NRG-1β to improve residual cardiac function after MI in type1 diabetic rats. Methods and Results: Sprague Dawley rats were induced type 1 diabetes by a single injection of streptozotocin (STZ) (65 mg/kg). Two weeks after induction of type 1 diabetes, rats underwent left coronary artery ligation to induce MI. STZ-diabetic rats were treated with saline or NRG-1β (100 ug/kg) twice a week for 7 weeks, starting two weeks prior to experimental MI. Residual left ventricular (LV) function was significantly greater in the NRG-1β-treated STZ-diabetic MI group compared to the vehicle-treated STZ-diabetic MI group 5 weeks after MI as assessed by high-resolution echocardiography. Furthermore, NRG-1β treatment in STZ-diabetic MI rats reduced myocardial fibrosis and apoptosis as well as decreased gene expression of key oxidant-producing enzymes. Conclusion: This study demonstrates that augmentation of NRG-1β signaling in STZ-diabetic post-MI rats via therapy with exogenous recombinant NRG-1β will alleviate subsequent HF through improvements in residual LV function via protection against adverse remodeling and apoptosis.

Myocardial infarction with and without reperfusion in sheep: early cardiac and neurohumoral changes

2000 ◽  
Vol 98 (6) ◽  
pp. 703-711 ◽  
Author(s):  
Christopher J. CHARLES ◽  
John M. ELLIOTT ◽  
M. Gary NICHOLLS ◽  
Miriam T. RADEMAKER ◽  
Mark RICHARDS
Keyword(s):  
Myocardial Infarction ◽  
Coronary Artery ◽  
Ejection Fraction ◽  
Troponin T ◽  
Coronary Artery Occlusion ◽  
Artery Occlusion ◽  
Left Ventricular ◽  
Lv Function ◽  
Large Animal ◽  
Lv Dysfunction

There are few stable and reproducible large-animal models of chronic heart failure produced by ischaemic damage to the myocardium. Here we characterize a novel method of inducing myocardial damage in closed-chest sheep by catheter delivery of thrombogenic coils, and compare this with a newly described open-artery model of cardiac injury in sheep. Sham controls were compared with animals subjected to (a) 90 min of coronary artery occlusion/reperfusion by PTCA (percutaneous transluminal coronary angioplasty) balloon, and (b) permanent coronary artery occlusion induced by catheter delivery of thrombogenic coils (seven sheep/group). Both balloon occlusion/reperfusion and permanent coil occlusion resulted in well-defined anteroapical infarcts, as documented by ECG changes, significant rises in creatine kinase (both groups P < 0.001) and troponin-T (both groups P < 0.05), and post-mortem examination. Washout of enzymes was much more rapid in the reperfused group (P < 0.01). Infarction resulted in significant reductions in left ventricular (LV) ejection fraction (both groups P < 0.01) and regional wall abnormalities. Ejection fraction 7 days post-coil (21.3±4.2%) was significantly lower (P < 0.01) than that 7 days post-balloon (38.8±4.5%). Coil-induced infarction was associated with acutely reduced arterial pressure (P < 0.05), and increases in heart rate (P < 0.05), atrial pressures (P < 0.05), plasma brain natriuretic peptide levels (P < 0.05) and adrenaline levels (P < 0.05). Rises seen in plasma endothelin levels in sham controls were blunted in the coil group (P < 0.001). Haemodynamic changes were less marked in the balloon group. In conclusion, restriction of coronary artery occlusion to 90 min results in infarction, but less LV dysfunction with reduced early remodelling, compared with permanent occlusion. Acute changes in biochemical markers, haemodynamics, neurohormones and LV function confirm that these are excellent models of open- and closed-artery myocardial infarction leading to asymptomatic LV dysfunction.

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