Posterolateral Myocardial Infarction Research Articles

ANOTHER BRICK IN THE WALL: A STRANGE CASE OF A BIG HUG

Abstract Background Left ventricular pseudoaneurysm (LVP) is a rare complication of myocardial infarction MI (less than 0,1% of all patients with MI) and develops when cardiac rupture is contained by adherent pericardium or scar tissue, thus contains no endocardium or myocardium, unlike a true left ventricular aneurysm (LVA). Clinical Case A 41–year–old man without remote cardiac history was admitted to the Emergency Department with chest pain that had started 7 days before after a referred ‘big hug’ from a friend. Results of the physical examination were unremarkable. Electrocardiogram: T waves negative in the inferior and lateral leads. Blood exams: normal troponins, C–reactive protein and D–dimer values. Chest computed tomography: no sign of pulmonary embolism. Transthoracic echocardiography (TE): ejection fraction 45%, voluminous aneurismal chamber communicating with the infero–posterior wall of the LV, stratified thrombus and mild mitral valve regurgitation. Coronary angiography: three vessel coronary artery disease. The last diagnosis was established by cardiac magnetic resonance imaging (MRI) which revealed a voluminous pseudoaneurysm of the inferior wall (56 mm x 50 mm with a 51 mm neck) and transmural late gadolinium enhancement (LGE) of the wall adjacent to the pseudoaneurysm with fibroadipose replacement and calcific metaplasia. The patient was transferred to the Cardiac Surgery Department. Intraoperatively the LVP was resected and the defect of the LV was repaired with a patch in bovine pericardium. In addition, coronary artery bypass grafting and mitral valve repair were performed. Discussion LVP develops when pericardium, in combination with thrombus and inflammation, surrounds a cardiac rupture. Inferior and posterolateral myocardial infarction (MI), due to occlusion of the Circumflex artery, are responsible for 82% of the LVP. LVP can be also found in the apical region due to anterior MI. In conclusion symptoms, signs, electrocardiographic abnormalities and radiographic findings seen in patients with LVP can be indistinguishable from those in patients with coronary disease alone. TE is the first non–invasive method for early diagnosis of LVA, but MRI is the gold standard for differential diagnosis between true aneurysm vs pseudoaneurysm. LGE of the pericardium is a new specific marker of pseudoaneurysm as opposed to true aneurysm.

Distribution of evoked delayed potential and delayed potential in a patient with subendocardial inferior infarction and transmural postero-lateral infarction: A case report

A 47-year-old man with transmural posterolateral myocardial infarction (MI) and subendocardial inferior MI underwent catheter ablation for monomorphic ventricular tachycardia (VT). Right ventricular extra stimulation could unmask evoked delayed potentials in the subendocardial infarction area without delayed potentials in the sinus rhythm. Extra stimulation mapping for VT is useful for hidden VT substrates, particularly in the subendocardial infarction area.

Abstract 12949: Mitral Valve Geometry and Remodeling in a Three Month Swine Model of Post-Infarction Heart Failure

Introduction: Mitral regurgitation (MR) following myocardial infarction (MI) is a known risk factor for increased hospitalizations and mortality. The longitudinal mitral valve remodeling in chronic ischemic MR (IMR) is not fully understood and a reproducible, large animal model is therefore needed. In this study, we establish a swine model of chronic IMR and investigate the consequent changes in mitral valve geometry. Methods: Yorkshire swine (n=7) were induced with an MI via targeted angiographic ethanol injection of the left circumflex coronary artery, and were followed to 3 months. Mitral valve geometry and MR grade were investigated at baseline, immediately after MI, and 3 months post MI ( Fig. A ). Epicardial echocardiography was performed under mini left thoracotomy for direct placement onto the left atrium, such that the entire left heart was imaged. Results: 3 months following MI, ejection fraction (EF) decreased compared to baseline (47.3 ± 8.4 vs 55.3 ± 6.5%, p=.03). Both effective regurgitant orifice area (EROA) and regurgitant volume (RV) increased compared to baseline (EROA: 12 ± .14 vs .01 ± .01cm 2 ; p=.001; RV: 18.7 ± 21.3 vs .14 ± .38ml; p=.001). Both tenting height (TH) and tenting area (TA) also increased compared to baseline (TH: 11.7 ± 2.8 vs 6.8 ± 0.7mm; p=.01; TA: 190 ± 66 vs 95 ± 16mm 2 ; p=.04), indicating tethering of the mitral valve. No differences were found in coaptation length (5.7 ± 1.4 vs 5.8 ± 0.8mm; p=.99) and anterior excursion angle (37.9 ± 10.5 vs 25.3 ± 11.9°; p=0.27). Posterior excursion angle decreased at 3 months following MI (25 ± 11.3 vs 39.6 ± 8.0°; p=.02), indicating restriction of the posterior leaflet ( Fig. B1-7 ) Conclusion: In this paired analysis of mitral valve and ventricular remodeling after posterolateral MI, consistent increase in EROA and RV were observed. This model mimics a clinically relevant situation, providing a platform for studying the effects of IMR correction on ventricular remodeling.

Left atrial geometry in an ovine ischemic mitral regurgitation model: implications for transcatheter mitral valve replacement devices with a left atrial anchoring mechanism

BackgroundTranscatheter mitral valve replacement (TMVR) is a challenging, but promising minimally invasive treatment option for patients with mitral valve disease. Depending on the anchoring mechanism, complications such as mitral leaflet or chordal disruption, aortic valve disruption or left ventricular outflow tract obstruction may occur. Supra-annular devices only anchor at the left atrial (LA) level with a low risk of these complications. For development of transcatheter valves based on LA anchoring, animal feasibility studies are required. In this study we sought to describe LA systolic and diastolic geometry in an ovine ischemic mitral regurgitation (IMR) model using magnetic resonance imaging (MRI) and echocardiography in order to facilitate future research focusing on TMVR device development for (I)MR with LA anchoring mechanisms.MethodsA group of 10 adult male Dorsett sheep underwent a left lateral thoracotomy. Posterolateral myocardial infarction was created by ligation of the left circumflex coronary artery, the obtuse marginal and diagonal branches. MRI and echocardiography were performed at baseline and 8 weeks after myocardial infarction (MI).ResultsSix animals survived to 8 weeks follow-up. All animals had grade 2 + or higher IMR 8 weeks post-MI. All LA geometric parameters did not change significantly 8 weeks post-MI compared to baseline. Diastolic and systolic interpapillary muscle distance increased significantly 8 weeks post-MI.ConclusionsSystolic and diastolic LA geometry do not change significantly in the presence of grade 2 + or higher IMR 8 weeks post-MI. These findings help facilitate future tailored TMVR device development with LA anchoring mechanisms.

Image-Guided Targeted Mitral Valve Tethering with Chordal Encircling Snares as a Preclinical Model of Secondary Mitral Regurgitation.

Development of transcatheter mitral valve interventions has ushered a significant need for large animal models of secondary mitral regurgitation. Though currently used heart failure models that chronically develop secondary mitral regurgitation are viable, the severity is lower than patients, the incubation time is long, and mortality is high. We sought to develop a swine model of acute secondary mitral regurgitation that uses image-guided placement of snares around the mitral chordae. Twenty-seven adult swine (n = 27) were assigned to secondary mitral regurgitation induced by valve tethering with image-guided chordal encircling snares (group 1, n = 7, tether MR (tMR)); secondary mitral regurgitation by percutaneous posterolateral myocardial infarction causing ventricular dysfunction and regurgitation (group 2, n = 6, functional MR (fMR)); and control animals (group 3, n = 14). Regurgitant fraction in tMR was 42.1 ± 14.2%, in fMR was 22 ± 9.6%, and in controls was 5.3 ± 3.8%. Mitral tenting height was 9.6 ± 1.3mm in tMR, 10.1 ± 1.5mm in fMR, and 5.8 ± 1.2mm in controls. Chordal encircling tethers reproducibly induce clinically relevant levels of secondary mitral regurgitation, providing a new animal model for use in translational research.

Alterations in Intracardiac Flow Patterns Affect Mitral Leaflets Dynamics in a Model of Ischemic Mitral Regurgitation.

This study was to evaluate the effects of ischemic mitral regurgitation (IMR) on vortex formation and leaflet dynamics using an established porcine infarct model of IMR. Using direct coronary ligation, five animals were subjected to a posterolateral myocardial infarction (MI) followed by an MRI at 12-weeks post MI. MR imaging consisted of 4D time-resolved left ventricular (LV) flow, full coverage 2D LV cine, and high resolution 2D cine of mitral valve dynamics. Five additional naïve animals underwent identical imaging protocols to serve as controls. Image analysis was performed to obtain mitral transvalvular flows as well as LV volumes throughout the cardiac cycle. In addition, anterior to posterior mid-leaflet tip distances were measured throughout the cardiac cycle for determination of temporal leaflet dynamics. It was found IMR caused asymmetric vortex ring formation with the anterior vortex having a lower vorticity relative to its posterior counterpart. In contrast, normal ventricles create symmetric and tightly curled vortices in the basal chamber just underneath the mitral leaflets which conserve kinetic energy and aid in effective ejection. IMR animals were also evaluated for leaflet separation and were found to have a greater leaflet opening and achieved peak vorticity and peak leaflet opening later than control animals. In conclusion, this study shows the effects that altered vortex formation, due to IMR, can have on ventricular filling and leaflet dynamics. These findings have important implications for understanding blood flow through the dilated heart and how ring annuloplasty and volume reduction interventions may influence mitral valve dynamics.

Comparative Results of Emergency Carotid Endarterectomy and Emergency Carotid Angioplasty With Stenting in the Acute Period of Ischemic Stroke. Multicenter Study Results

AIM OF STUDY Study of hospital results of emergency carotid endarterectomy (CEE) and carotid angioplasty with stenting (CAS) in the acute period of acute cerebrovascular accident (ACVA). MATERIAL AND METHODS From January 2008 to August 2020, the study included 615 patients with hemodynamically significant stenosis of the internal carotid arteries (ICA), operated on in the acute period of ischemic stroke (within 3 days from the onset of stroke). Depending on the type of revascularization implemented, all patients were divided into 2 groups: group 1 — CAS (n=312); 2nd group — CEE (n=357). Inclusion criteria were as follows: 1. Mild neurological disorders: NIHSS score 3–8; Modified Rankin Scale score 2 of less; Barthel Scale > 61; 2. Indications for CEE / CAS according to the current national recommendations; 3. Ischemic focus in the brain not more than 2.5 cm in diameter. Exclusion criteria: 1. Presence of con-traindications to CEE / CAS. Carotid angioplasty with stenting was performed according to the standard technique; in all cases, distal embolism protection systems were used. Carot-id endarterectomy was performed according to the classical and eversion techniques. When the retrograde pressure in the ICA was less than 60% of the systemic pressure, a temporary shunt (TS) was installed. In the postoperative period, all patients underwent multispiral computed tomography (MSCT) of the brain. In the absence of negative dynam-ics in the neurological status, MSCT was performed on the 7th day after the operation, if available, it was performed urgently. The checkpoints were the development of such unfa-vorable cardiovascular events as death, myocardial infarction (MI), stroke / transient is-chemic attack (TIA), “mute” stroke, “mute” hemorrhagic transformations, combined end-point (death + all strokes / TIA + MI). Strokes were mute if diagnosed according to MSCT, without symptoms. RESULTS In 69% of diabetic patients with anterior myocardial infarction and in 63% of patients with posterolateral MI 12 months after PCI, signs of LV inferiority were revealed in the form of an increase in the indices of end-diastolic and systolic volumes of the LV and low ejection fraction (≤45%). In patients without diabetes, these figures were 18% and 31%, respectively. High concentrations of NT-proBNP on the first day of myocardial infarction after PCI were of the greatest value in the diagnosis and prognosis of LV UR after 12 months. RESULTS When analyzing hospital complications, significant differences in the frequency of lethal outcome were not obtained (group 1: n=6 (1.92%); group 2: n=8 (2.24%); p=0.98; OR=0.85; 95% CI 0.29–2.49); MI (group 1: n=5 (1.6%); group 2: n=5 (1.4%); p=0.91; OR=1.14; 95% CI 0.32–3.99 ); ACVA (ischemic type) / TIA (group 1: n=5 (1.6%); group 2: n=6 (1.7%); p=0.82; OR=0.95; 95% CI 0.28–3.15), as well as “mute” ACVA (group 1: n=7 (2.2%); group 2: n=15 (4.2%); p=0.23; OR=0.52; 95% CI 0.21–1.3). However, the vast majority of hemorrhagic transformations (group 1: n=2 (0.64%); group 2: n=13 (3.6%); p=0.018; OR=0.17; 95% CI 0.03–0.76) and all “mute” hemorrhagic transformations (group 1: n=0; group 2: n=26 (7.3%); p=0.001; OR=0.02; 95% CI 0.001–0.33) were observed only in the CEE group, which was reflected in the maximum values of the combined end point: group 1: n=22 (7.05%); group 2: n=73 (20.4%); p<0.0001; OR=0.29; 95% CI 0.17–0.48). Thus, in the CEE group, every 5th patient had a complication. CONCLUSION Carotid angioplasty with stenting is the safest method of revascularization for patients in the acute period of ACVA. This is largely due to the reduction in the risk of reperfusion syndrome and the prevention of embolism due to the use of modern protection systems. Carotid endarterectomy can be performed with comparable efficiency only when a tempo-rary shunt is placed in the internal carotid arteries in the absence of unstable atheroscle-rotic plaque.

Predictive Value of N-Terminal Prohormone of Brain Natriuretic Peptide in Long-Term Remodeling of the Left Ventricle in Diabetic Patients of Young and Middle Age With Acute Coronary Syndrome After Percutaneous Coronary Intervention

Abstract. Recently, quantitative analysis of the level of the N-terminal prohormone of the brain naturetic peptide (NT-proBNP) has been widely used to diagnose heart failure (HF). A statistically significant correlation was found between the serum NT-proBNP concentration and HF stage. It was found that in patients with high cardiovascular risk, NT-proBNP has the highest predictive value in relation to mortality. In young and middle-aged patients with diabetes mellitus (DM) with myocardial infarction (MI) and stents of an infarct-associated artery, the frequency of unfavorable remodeling (UR) of the left ventricle (LV) in the long-term prognosis was studied. The frequency of atherosclerotic lesions of the coronary arteries (CA) in patients with diabetes in acute coronary syndrome (ACS) was determined, the results of echocardiographic parameters were presented in the follow-up dynamics, the value of serum NT-proBNP in predicting LV UR 12 months after myocardial infarction (MI) was determined.Aim of study. To assess the diagnostic capabilities of NT-proBNP in the long-term prediction of the development of LV infarction in patients with MI with diabetes in young and middle age after percutaneous coronary intervention (PCI).Design. Prospective controlled non-randomized trial. The patients were examined twice: on the first day of ACS after PCI with stenting of infarct-associated coronary artery and 12 months after AMI. The study included 191 patients with ACS with / without ST-segment elevation, who were divided into two groups. The main group included 76 patients with ACS with diabetes mellitus, the comparison group included 115 patients with ACS without diabetes mellitus. Patients in both groups were comparable in age, gender, comorbidity, and complications of AMI. The duration of diabetes was, on average, 6 years (from one to 12 years).Material and methods. All patients underwent electrocardiography, echocardiography, tests for the content of troponin I, NT-proBNP, glycosylated hemoglobin, lipids, determined the level of creatinine in the blood and the glomerular filtration rate according to the Modification of diet in renal disease (MDRD). All patients were examined twice: on the first day of ACS after PCI with stenting of infarct-associated coronary artery and 12 months later.Results. In 69% of diabetic patients with anterior myocardial infarction and in 63% of patients with posterolateral MI 12 months after PCI, signs of LV inferiority were revealed in the form of an increase in the indices of end-diastolic and systolic volumes of the LV and low ejection fraction (≤45%). In patients without diabetes, these figures were 18% and 31%, respectively. High concentrations of NT-proBNP on the first day of myocardial infarction after PCI were of the greatest value in the diagnosis and prognosis of LV UR after 12 months.Conclusion. The NT-proBNP level of more than 776 pg/ml on the first day after PCI is an indicator of an unfavorable long-term prognosis in patients with young and middle-aged diabetes in terms of the development of LV systolic dysfunction.

Abstract 16801: Papillary Muscle Tip Approximation in Repair of Ischemic Mitral Regurgitation in a Chronic Swine Model

Introduction: Mitral valve (MV) repair with undersized annuloplasty (UMA) for ischemic mitral regurgitation (IMR) is being abandoned in favor of valve replacement (MVR) following CTSN trial results. However, in patients with durable repair, survival and left ventricular function (LVF) were significantly better than MVR. Achieving a durable repair with UMA is challenging as it draws leaflets away from papillary muscle (PM) insertions, causing unphysiological tethering and unicuspid configuration that fails (FigA-B). Hypothesis: Drawing PM tips together with an approximating stitch (PMT-A) can relieve leaflet tethering and enable better repair (FigC). A chronic swine model of IMR was used to compare effects of isolated PMT-A, UMA and PMT-A+UMA on MV and LV at 3 months post surgery. Methods: Twenty-five farm swine underwent catheterization and occlusion of left circumflex artery, resulting in postero-lateral myocardial infarction (MI). Two months after MI, IMR severity of >2+ was confirmed on echo, and animals underwent one of the 3 repairs: PMT-A (n=6), UMA (n=8), PMT-A+UMA (n=11). Echo was performed postoperatively and repeated with MRI at 3 months (FigD). MV kinematics, coaptation geometry, and LVF were assessed. Results: IMR was eliminated after all repairs and did not recur through the study. Annulus continued to grow after PMT-A, but not in UMA or PMT-A+UMA group (FigE1) without increasing severity of IMR. Compared to prerepair, tenting depth was significantly reduced only in PMT-A and PMT-A+UMA groups (FigE2). Both leaflet excursion angles (diastolic minus systolic angles) increased after PMT-A, but not in other groups (FigE3-4). LV size and LVF was similar between groups, confirming that PMT-A did not perturb diastolic filling. Conclusions: In this model of IMR, PMT-A improved leaflet mobility, compared to isolated UMA or PMT-A+UMA. PMT-A is a simple technique that can potentially improve durability of MV repair by restoring valvular kinematics.

Injectable Shear-Thinning Hydrogels Prevent Ischemic Mitral Regurgitation and Normalize Ventricular Flow Dynamics

Injectable hydrogels are known to attenuate left-ventricular (LV) remodeling following myocardial infarction (MI), dependent on material mechanical properties. The effect of hydrogel injection on ischemic mitral regurgitation (IMR) resultant from LV remodeling remains relatively unexplored. This study uses multiple imaging methods to evaluate the efficacy of injectable hydrogels with tunable modulus to prevent post-MI development of IMR. Posterolateral MI was induced in 20 sheep with subsequent epicardial injection of saline (control (MI); n = 7), soft hydrogel (guest-host crosslinking, modulus <1 kPa, n = 7), or stiff hydrogel (dual-crosslinking, modulus = 41.4 ± 4.3 kPa, n = 6) within the infarct region and 8-week follow-up. IMR and valve geometry were assessed by echocardiography. LV geometry (long-axis dimension, posterior chordae length) and ventricular flow dynamics were assessed by magnetic resonance imaging. IMR developed in MI controls at 8 weeks and was attenuated with hydrogel treatment (IMR grade for MI: 1.86 ± 0.69; guest-host crosslinking: 1.29 ± 1.11; dual-crosslinking: 0.50 ± 0.55, P = 0.02 vs MI). Tethering of the posterior leaflet increased in MI controls, but not with stiff hydrogel treatment. Across cohorts, IMR was correlated with changes in the long-axis dimension (Spearman R = 0.77) and posterior chordae length (Spearman R = 0.64). Intraventricular flow dynamics were highly disturbed in MI controls, but stiff hydrogel treatment normalized flow patterns and reduced the prevalence of large (≥2+ MR, >5 mL) regurgitant volumes. Injectable hydrogels attenuated subvalvular remodeling and leaflet tethering, preventing IMR development and normalizing LV flow dynamics. Hydrogels with a supraphysiological modulus yielded best outcomes.

Effects of hydrogel injection on borderzone contractility post-myocardial infarction.

Injectable hydrogels are a potential therapy for mitigating adverse left ventricular (LV) remodeling after myocardial infarction (MI). Previous studies using magnetic resonance imaging (MRI) have shown that hydrogel treatment improves systolic strain in the borderzone (BZ) region surrounding the infarct. However, the corresponding contractile properties of the BZ myocardium are still unknown. The goal of the current study was to quantify the in vivo contractile properties of the BZ myocardium post-MI in an ovine model treated with an injectable hydrogel. Contractile properties were determined 8 weeks following posterolateral MI by minimizing the difference between in vivo strains and volume calculated from MRI and finite element model predicted strains and volume. This was accomplished by using a combination of MRI, catheterization, finite element modeling, and numerical optimization. Results show contractility in the BZ of animals treated with hydrogel injection was significantly higher than untreated controls. End-systolic (ES) fiber stress was also greatly reduced in the BZ of treated animals. The passive stiffness of the treated infarct region was found to be greater than the untreated control. Additionally, the wall thickness in the infarct and BZ regions was found to be significantly higher in the treated animals. Treatment with hydrogel injection significantly improved BZ function and reduced LV remodeling, via altered MI properties. These changes are linked to a reduction in the ES fiber stress in the BZ myocardium surrounding the infarct. The current results imply that injectable hydrogels could be a viable therapy for maintaining LV function post-MI.

Moderate Ischemic Mitral Regurgitation After Posterolateral Myocardial Infarction in Sheep Alters Left Ventricular Shear but Not Normal Strain in the Infarct and Infarct Borderzone

Chronic ischemic mitral regurgitation (CIMR) is associated with poor outcome. Left ventricular (LV) strain after posterolateral myocardial infarction (MI) may drive LV remodeling. Although moderate CIMR hasbeen previously shown to affect LV remodeling, the effect of CIMR on LV strain after posterolateral MI remains unknown. We tested the hypothesis that moderate CIMR alters LV strain after posterolateral MI. Posterolateral MI was created in 10 sheep. Cardiac magnetic resonance imaging with tags was performed 2 weeks before and 2, 8, and 16 weeks after MI. The left and right ventricular volumes were measured, and regurgitant volume indexed to body surface area (regurgitant volume index) was calculated as the difference between left ventricle and right ventricle stroke volumes divided by body surface area. Three-dimensional strain was calculated. Circumferential strain (Ecc) and longitudinal strain (Ell) were reduced in the infarct proper, MI borderzone, and remote myocardium 16 weeks after MI.In addition, radial circumferential (Erc) and radial longitudinal (Erl) shear strains were reduced in remote myocardium but increased in the infarct and borderzone 16weeks after MI. Of all strain components, however, only Erc was affected by regurgitant volume index (p=0.0005). There was no statistically significant effect of regurgitant volume index on Ecc, Ell, Erl, or circumferential longitudinal shear strain (Ecl). Moderate CIMR alters radial circumferential shear strain after posterolateral MI in sheep. Further studies are needed to determine the effect of shear strain on myocyte hypertrophy and the effect of mitral repair on myocardial strain.

Temporal Changes in Infarct Material Properties: An In Vivo Assessment Using Magnetic Resonance Imaging and Finite Element Simulations

Infarct expansion initiates and sustains adverse left ventricular (LV) remodeling after myocardial infarction (MI) and is influenced by temporal changes in infarct material properties. Data from exvivo biaxial extension testing support this hypothesis; however, infarct material properties have never been measured invivo. The goal of the current study was to serially quantify the invivo material properties and fiber orientation of infarcted myocardium over a 12-week period in a porcine model ofMI. A combination of magnetic resonance imaging (MRI), catheterization, finite element modeling, and numeric optimization was used to analyze posterolateral MI. Specifically, properties were determined by minimizing the difference between invivo strains and volume calculated from MRI and strains and volume predicted by finite element modeling. In 1 week after MI, the infarct region was found to be approximately 20 times stiffer than normal diastolic myocardium. Over the course of 12 weeks, the infarct region became progressively less stiff as the LV dilated andejection fraction decreased. The infarct thinned by nearly half during the remodeling period, and infarct fiberangles became more circumferentially oriented. The results reported here are consistent with previously described exvivo biaxial extension studiesof infarct material properties and the circumferential change of collagen orientation in posterolateral infarcts. The current study represents a significant advance in that the method used allows for the serial assessment of an individual infarct invivo over time and avoids the inherent limitations related to the testing of excised tissues.

Estimating passive mechanical properties in a myocardial infarction using MRI and finite element simulations.

Myocardial infarction (MI) triggers a series of maladaptive events that lead to structural and functional changes in the left ventricle. It is crucial to better understand the progression of adverse remodeling, in order to develop effective treatment. In addition, being able to assess changes in vivo would be a powerful tool in the clinic. The goal of the current study is to quantify the in vivo material properties of infarcted and remote myocardium 1week after MI, as well as the orientation of collagen fibers in the infarct. This will be accomplished by using a combination of magnetic resonance imaging (MRI), catheterization, finite element modeling, and numerical optimization to analyze a porcine model ([Formula: see text]) of posterolateral myocardial infarction. Specifically, properties will be determined by minimizing the difference between in vivo strains and volume calculated from MRI and finite element model predicted strains and volume. The results indicate that the infarct region is stiffer than the remote region and that the infarct collagen fibers become more circumferentially oriented 1week post-MI. These findings are consistent with previous studies, which employed ex vivo techniques. The proposed methodology will ultimately provide a means of predicting remote and infarct mechanical properties in vivo at any time point post-MI.

Posterior Papillary Muscle Anchoring Affects Remote Myofiber Stress and Pump Function: Finite Element Analysis

The role of posterior papillary muscle anchoring (PPMA) in the management of chronic ischemic mitral regurgitation (CIMR) is controversial. We studied the effect of anchoring pointdirection and relocation displacement on left ventricular (LV) regional myofiber stress and pump function. Previously described finite element models of sheep 16 weeks after posterolateral myocardial infarction (MI) were used. True-sized mitral annuloplasty (MA) ring insertion plus different PPM anchoring techniques were simulated. Anchoring points tested included both commissures and the central anterior mitral annulus; relocation displacement varied from 10% to 40% of baseline diastolic distance from the PPM to the anchor points on the annulus. For each reconstruction scenario, myofiber stress in the MI, border zone, and remote myocardium as well as pump function were calculated. PPMA caused reductions in myofiber stress at end-diastole and end-systole in all regions of the left ventricle that were proportional to the relocation displacement. Although stress reduction was greatest in the MI region, it also occurred in the remote region. The maximum 40% displacement caused a slight reduction in LV pump function. However, with the correction of regurgitation by MA plus PPMA, there was an overall increase in forward stroke volume. Finally, anchoring point direction had no effect on myofiber stress or pump function. PPMA reduces remote myofiber stress, which is proportional to the absolute distance of relocation and independent of anchoring point. Aggressive use of PPMA techniques to reduce remote myofiber stress may accelerate reverse LV remodeling without impairing LV function.

Directed Epicardial Assistance in Ischemic Cardiomyopathy: Flow and Function Using Cardiac Magnetic Resonance Imaging

Heart failure after myocardial infarction (MI) is a result of increased myocardial workload, adverse left ventricular (LV) geometric remodeling, and less efficient LV fluid movement. In this study we utilize cardiac magnetic resonance imaging to evaluate ventricular function and flow after placement of a novel directed epicardial assist device. Five swine underwent posterolateral MI and were allowed to remodel for 12 weeks. An inflatable bladder was positioned centrally within the infarct and secured with mesh. The device was connected to an external gas exchange pump, which inflated and deflated in synchrony with the cardiac cycle. Animals then underwent cardiac magnetic resonance imaging during active epicardial assistance and with no assistance. Active epicardial assistance of the infarct showed immediate improvement in LV function and intraventricular flow. Ejection fraction significantly improved from 26.0% ± 4.9% to 37.3% ± 4.5% (p < 0.01). End-systolic volume (85.5 ± 12.7 mL versus 70.1 ± 11.9 mL, p < 0.01) and stroke volume (28.5 ± 4.4 mL versus 39.9 ± 3.1 mL, p = 0.03) were also improved with assistance. End-diastolic volume and regurgitant fraction did not change with treatment. Regional LV flow improved both qualitatively and quantitatively during assistance. Unassisted infarct regional flow showed highly discoordinate blood movement with very slow egress from the posterolateral wall. Large areas of stagnant flow were also identified. With assistance, posterolateral wall blood velocities improved significantly during both systole (26.4% ± 3.2% versus 12.6% ± 1.2% maximum velocity; p < 0.001) and diastole (54.3% ± 9.3% versus 24.2% ± 2.5% maximum velocity; p < 0.01). Directed epicardial assistance can improve LV function and flow in ischemic cardiomyopathy. This novel device may provide a valuable alternative to currently available heart failure therapies.

Acute myocardial infarction after prednisolone administration for the treatment of anaphylaxis caused by a wasp sting : online article - case report

Wasp stings have been demonstrated to cause a wide spectrum of allergic reactions from localised reactions to anaphylaxis. Acute coronary syndromes have been described as potential complications of anaphylactic reactions or some of the drugs used for the treatment of anaphylaxis. We know of only a few cases reported of acute myocardial infarction (MI) following corticosteroid administration or anaphylaxis in subjects with normal coronary arteries. If it exists, underlying subclinical coronary atherosclerosis may become clinically evident. A 20 year-old male with anaphylaxis due to a wasp sting, complicated by acute ST-elevation MI after intravenous methyl prednisolone administration, is the subject of this report. He was admitted to our emergency service for dizziness, blurred vision, presyncope and mild respiratory distress 10 minutes after the wasp had stung him on the nape of the neck. Six to seven minutes after administration of prednisolone, the patient complained of typical chest pains. A high posterolateral MI with mild mitral regurgitation were seen on examination. He was treated conservatively with aspirin and heparine. Coronary angiography and intravascular ultrasound imaging, performed 10 days later, showed no evidence of obstructive coronary artery disease. Although reduced coronary perfusion, local histamine release-induced coronary vasospasm or severe hypoxia have been suggested, the pathophysiology remains unclear. Acute STEMI may be a rare but clinically important complication of a wasp sting, anaphylaxis or the corticosteroid used for its treatment, even in young adults with normal coronary arteries. Therefore, physicians should be aware of such serious complications in order to diagnose them early.

Invited Commentary

Invited Commentary

Left Ventricular Myocardial Contractility Is Depressed in the Borderzone After Posterolateral Myocardial Infarction

Contractility in the borderzone (BZ) after anteroapical myocardial infarction (MI) is depressed. We tested the hypothesis that BZ contractility is also decreased after posterolateral MI. Five sheep underwent posterolateral MI. Magnetic resonance imaging (MRI) was performed 2 weeks before and 16 weeks after MI, and left ventricular (LV) volume and regional strain were measured. Finite element (FE) models were constructed, and the systolic material parameter, Tmax, was calculated in the BZ and remote myocardium by minimizing the difference between experimentally measured and calculated LV strain and volume. Sheep were sacrificed 17 weeks after MI, and myocardial muscle fibers were taken from the BZ and remote myocardium. Fibers were chemically demembranated, and isometric developed force, Fmax, was measured at supramaximal [Ca(2+)]. Routine light microscopy was also performed. There was no difference in Tmax in the remote myocardium before and 16 weeks after MI. However, there was a large decrease (63.3%, p = 0.005) in Tmax in the BZ when compared with the remote myocardium 16 weeks after MI. In addition, there was a significant reduction of BZ Fmax for all samples (18.9%, p = 0.0067). Myocyte cross-sectional area increased by 61% (p = 0.021) in the BZ, but there was no increase in fibrosis. Contractility in the BZ is significantly depressed relative to the remote myocardium after posterolateral MI. The reduction in contractility is due at least in part to a decrease in contractile protein function.

Comprehensive Annular and Subvalvular Repair of Chronic Ischemic Mitral Regurgitation Improves Long-Term Results With the Least Ventricular Remodeling

Undersized ring annuloplasty for ischemic mitral regurgitation (MR) is associated with variable results and >30% MR recurrence. We tested whether subvalvular repair by severing second-order mitral chordae can improve annuloplasty by reducing papillary muscle tethering. Posterolateral myocardial infarction known to produce chronic remodeling and MR was created in 28 sheep. At 3 months, sheep were randomized to sham surgery versus isolated undersized annuloplasty versus isolated bileaflet chordal cutting versus the combined therapy (n=7 each). At baseline, chronic myocardial infarction (3 months), and euthanasia (6.6 months), we measured left ventricular (LV) volumes and ejection fraction, wall motion score index, MR regurgitation fraction and vena contracta, mitral annulus area, and posterior leaflet restriction angle (posterior leaflet to mitral annulus area) by 2-dimensional and 3-dimensional echocardiography. All groups were comparable at baseline and chronic myocardial infarction, with mild to moderate MR (MR vena contracta, 4.6±0.1 mm; MR regurgitation fraction, 24.2±2.9%) and mitral annulus dilatation (P<0.01). At euthanasia, MR progressed to moderate to severe in controls but decreased to trace with ring plus chordal cutting versus trace to mild with chordal cutting alone versus mild to moderate with ring alone (MR vena contracta, 5.9±1.1 mm in controls, 0.5±0.08 with both, 1.0±0.3 with chordal cutting alone, 2.0±0.4 with ring alone; P<0.01). In addition, LV end-systolic volume increased by 108% in controls versus 28% with ring plus chordal cutting, less than with each intervention alone (P<0.01). In multivariate analysis, LV end-systolic volume and mitral annulus area most strongly predicted MR (r(2)=0.82, P<0.01). Comprehensive annular and subvalvular repair improves long-term reduction of both chronic ischemic MR and LV remodeling without decreasing global or segmental LV function at follow-up.