Experimental modelling of cardiac pressure overload hypertrophy: Modified technique for precise, reproducible, safe and easy aortic arch banding-debanding in mice.
ABSTRACT: Pressure overload left ventricular hypertrophy is a known precursor of heart failure with ominous prognosis. The development of experimental models that reproduce this phenomenon is instrumental for the advancement in our understanding of its pathophysiology. The gold standard of these models is the controlled constriction of the mid aortic arch in mice according to Rockman's technique (RT). We developed a modified technique that allows individualized and fully controlled constriction of the aorta, improves efficiency and generates a reproducible stenosis that is technically easy to perform and release. An algorithm calculates, based on the echocardiographic arch diameter, the intended perimeter at the constriction, and a suture is prepared with two knots separated accordingly. The aorta is encircled twice with the suture and the loop is closed with a microclip under both knots. We performed controlled aortic constriction with Rockman's and the double loop-clip (DLC) techniques in mice. DLC proved superiority in efficiency (mortality and invalid experiments) and more homogeneity of the results (transcoarctational gradients, LV mass, cardiomyocyte hypertrophy, gene expression) than RT. DLC technique optimizes animal use and generates a consistent and customized aortic constriction with homogeneous LV pressure overload morphofunctional, structural, and molecular features.
Project description:We are developing a transapical-to-aorta double lumen cannula (TAA DLC) for a less-invasive/more dependable neonatal left ventricular assist device.The 18-Fr TAA DLC prototypes were bench tested and evaluated for 6 hours in neonate lambs (n = 6, 7.7-10 kg). The cardiac apex was exposed through a left anterolateral thoracotomy through the sixth intercostal space. The TAA DLC was inserted through a mattress stitch on apex, passing LV-aortic valve, into the ascending aorta with insertion/deployment guided by pressure waveform. The DLC was connected to blood pump. Cardiac output and aortic root blood flow were measured with perivascular flow sensors. Activated clotting time was maintained at 180-250 seconds.The DLC pumped up to 1.8 L/min flow against 63 mm Hg drainage pressure and 145 mm Hg infusion pressure in bench testing. In all lambs, the DLC was inserted/deployed properly within 1 minute on the first attempt. Pumping flow was maintained at 1.2-1.3 L/min. Systolic arterial pressure decreased and diastolic arterial pressure/mean arterial pressure increased, indicating decreased afterload and increased perfusion pressure. Left ventricular end-diastolic pressure decreased from 13 ± 1 mm Hg to 6 ± 2 mm Hg, indicating decreased preload. Aortic root backward flow was 2.4% ± 0.6% without DLC and 3.5% ± 0.8% of cardiac output with DLC, indicating no significant DLC-induced aortic valve regurgitation. After 6 hours, free hemoglobin was <5 mg/dL with hemoglobin/platelets unchanged. No significant thrombus was found in pumps/DLCs. No trauma was found in LV, aortic valve, and aorta.Our TAA DLC-based neonate left ventricular assist device efficiently unloaded the LV in lambs.
Project description:We sought to define age-related geometric changes of the aortic arch and determine their relationship to central aortic stiffness and left ventricular (LV) remodeling.The proximal aorta has been shown to thicken, enlarge in diameter, and lengthen with aging in humans. However, no systematic study has described age-related longitudinal and transversal remodeling of the aortic arch and their relationship with LV mass and remodeling.We studied 100 subjects (55 women, 45 men, average age 46 ± 16 years) free of overt cardiovascular disease using magnetic resonance imaging to determine aortic arch geometry (length, diameters, height, width, and curvature), aortic arch function (local aortic distensibility and arch pulse wave velocity [PWV]), and LV volumes and mass. Radial tonometry was used to calculate central blood pressure.Aortic diameters and arch length increased significantly with age. The ascending aorta length increased most, with age leading to aortic arch widening and decreased curvature. These geometric changes of the aortic arch were significantly related to decreased ascending aortic distensibility, increased aortic arch PWV (p < 0.001), and increased central blood pressures (p < 0.001). Increased ascending aortic diameter, lengthening, and decreased curvature of the aortic arch (unfolding) were all significantly associated with increased LV mass and concentric remodeling independently of age, sex, body size, and central blood pressure (p < 0.01).Age-related unfolding of the aortic arch is related to increased proximal aortic stiffness in individuals without cardiovascular disease and associated with increased LV mass and mass-to-volume ratio independent of age, body size, central pressure, and cardiovascular risk factors.
Project description:Activation of AMP-activated protein kinase (AMPK)-?2 protects the heart against pressure overload-induced heart failure in mice. Although metformin is a known activator of AMPK, it is unclear whether its cardioprotection acts independently of an AMPK?2-dependent pathway. Because the role of AMPK?1 stimulation on remodeling of failing hearts is poorly defined, we first studied the effects of disruption of both the AMPK?1 and AMPK?2 genes on the response to transverse aortic constriction-induced left ventricular (LV) hypertrophy and dysfunction in mice. AMPK?2 gene knockout significantly exacerbated the degree of transverse aortic constriction-induced LV hypertrophy and dysfunction, whereas AMPK?1 gene knockout had no effect on the degree of transverse aortic constriction-induced LV hypertrophy and dysfunction. Administration of metformin was equally effective in attenuating transverse aortic constriction-induced LV remodeling in both wild-type and AMPK?2 knockout mice, as evidenced by reduced LV and lung weights, a preserved LV ejection fraction, and reduced phosphorylation of mammalian target of rapamycin (p-mTOR(Ser2448)) and its downstream target p-p70S6K(Thr389). These data support the notion that activation of AMPK?1 plays a negligible role in protecting the heart against the adverse effects of chronic pressure overload, and that metformin protects against adverse remodeling through a pathway that seems independent of AMPK?2.
Project description:The use of histone deacetylase (HDAC) inhibitor is a novel therapeutic strategy for cardiovascular disease. Studies have shown that many HDAC inhibitors have the ability to reduce the aortic remodeling in various animal models. We hypothesized that the HDAC inhibitor, MGCD0103 (MGCD), attenuates aortic remodeling in rats under pressure overload-induced by transverse aortic constriction (TAC). The aortic ring tension analysis was conducted using the thoracic aorta. Sections of the aorta were visualized after hematoxylin and eosin, trichrome, and Verhoeff-van Gieson staining, and immunohistochemistry. The expression of genes related to aortic remodeling (?SMA, Mmp2, and Mmp9) and angiotensin receptors (Agtr1 and Agtr2) was determined by quantitative real-time polymerase chain reaction. There was a significant decrease in relaxation of the aorta when treated with MGCD. Fibrosis of the aortic wall and expression of angiotensin receptors increased in TAC rats, which was attenuated by MGCD. These results indicate that MGCD, an HDAC inhibitor, attenuates aortic remodeling in rats with TAC-induced pressure overload rats and may serve as a potential therapeutic target of antiaortic remodeling in pressure overload-induced hypertension-related diseases.
Project description:BACKGROUND:Acute Stanford type A aortic dissection is often fatal, with a high mortality rate and requiring emergency intervention. Salvage surgery aims to keep the patient alive by addressing severe aortic regurgitation, tamponade, primary tear, and organ malperfusion and, if possible, prevent the late dissection-related complications in the proximal and downstream aorta. Unfortunately, no optimal standard treatment or technique to treat this disease exists. Total arch replacement with frozen elephant trunk technique plays an important role in treating acute type A aortic dissection. We aim to describe a modified elephant trunk technique and report its short-term outcomes. METHODS:From February 2018 to August 2019, 16 patients diagnosed with acute Stanford type A aortic dissection underwent surgery with the modified frozen elephant trunk technique at Xiamen Heart Center (male/female: 9/7; average age: 56.1?±?7.6?years). All perioperative variables were recorded and analyzed. We measured the diameters of the ascending aorta, aortic arch, and descending aorta on the bifurcation of the pulmonary and abdominal aortas and compared the diameters at admission, before discharge, and 3?months after discharge. RESULTS:Fifteen patients (93.8%) had hypertension. The primary tears were located in the lesser curvature of the aortic arch and ascending aorta in 5 (31.3%) and 9 patients (56.3%), respectively, and no entry was found in 2 patients (12.5%). The dissection extended to the iliac artery and distal descending aorta in 14 (87.6%) and 2 patients (12.5%), respectively. The duration of cardiopulmonary bypass (CPB), cross-clamping, and antegrade cerebral perfusion were 215.8?±?40.5, 140.8?±?32.3, and 55.1?± 15.2?min, respectively. Aortic valve repair was performed in 15 patients (93.8%). Bentall procedure was performed in one patient (6.3%). Another patient received coronary artery repair (6.3%). The diameters at all levels were greater on discharge than those on admission, except the aortic arch. After 3?months, the true lumen diameter distal to the frozen elephant trunk increased, indicating false lumen thrombosis and/or aortic remodeling. CONCLUSIONS:The modified frozen elephant trunk technique for acute Stanford type A aortic dissection is safe and feasible and could be used for organ malperfusion. Short-term outcomes are encouraging, but long-term outcomes require further investigation.
Project description:BACKGROUND:AXL is a receptor tyrosine kinase that has been related to kidney and vascular disorders. Heart failure patients with reduced ejection fraction have higher AXL in serum than controls. No information about Axl expression with HF progression is available. METHODS:Thoracic transverse aortic constriction (TAC) was successfully performed on male Wistar rats (n = 25) with different constriction levels. Controls underwent sham surgery (n = 12). Echocardiography measurements were performed 4-8 weeks after surgery. Collagen deposition was measured with picrosirius red staining. Axl mRNA levels in left ventricle (LV), left kidney (LK) and ascending aorta (aAo) and the LV expression of cardiac remodeling and fibrogenic factors were quantified with real-time PCR. AXL LV protein levels were quantified with western blot and localization was analyzed by immunohistochemistry. Soluble AXL levels in plasma were assayed with ELISA. RESULTS:Successful TAC rats were classified into LV hypertrophy (LVH) or heart failure (HF), modeling the progressive cardiac changes after pressure overload. Collagen deposition was increased only in the HF group. LV Axl mRNA levels were higher in LVH and HF than in Sham rats, and correlated with LVHi, and hypertrophic and fibrogenic mediators. However, no association was found with LV systolic function. AXL was expressed in LV myocytes and other cell types. Concentration of circulating sAXL in plasma was increased in the LVH group compared to Sham and HF rats. Axl mRNA levels were similar in all groups in the LK and aAo. CONCLUSIONS:Axl expression pattern suggests a role in the early progression of LV remodeling in HF but not in the later systolic dysfunction. The higher levels of circulating AXL found in HF patients most probably shed from the heart.
Project description:We report successful total debranching thoracic endovascular aortic repair using the elephant trunk insertion technique without hypothermic circulatory arrest for a 56-year-old man who developed aortic arch dissection and ascending aortic aneurysm. In the first step, an elephant trunk graft was inserted into the ascending aorta under cardiopulmonary bypass, and a branched prosthetic graft was attached to the ascending aorta. The left common carotid artery and brachiocephalic artery were sequentially anastomosed to the branched graft. The second step was thoracic endovascular aortic repair covering the elephant trunk to the distal arch. Postprocedure digital subtraction angiography showed no endoleaks or false lumen.
Project description:<h4>Background</h4>Left ventricular (LV) and right ventricular (RV) function have an important impact on symptom occurrence, disease progression and exercise tolerance in pressure overload-induced heart failure, but particularly RV functional changes are not well described in the relevant aortic banding mouse model. Therefore, we quantified time-dependent alterations in the ventricular morphology and function in two models of hypertrophy and heart failure and we studied the relationship between RV and LV function during the transition from hypertrophy to heart failure.<h4>Methods</h4>MRI was used to quantify RV and LV function and morphology in healthy (n?=?4) and sham operated (n?=?3) C57BL/6 mice, and animals with a mild (n?=?5) and a severe aortic constriction (n?=?10).<h4>Results</h4>Mice subjected to a mild constriction showed increased LV mass (P<0.01) and depressed LV ejection fraction (EF) (P<0.05) as compared to controls, but had similar RVEF (P>0.05). Animals with a severe constriction progressively developed LV hypertrophy (P<0.001), depressed LVEF (P<0.001), followed by a declining RVEF (P<0.001) and the development of pulmonary remodeling, as compared to controls during a 10-week follow-up. Myocardial strain, as a measure for local cardiac function, decreased in mice with a severe constriction compared to controls (P<0.05).<h4>Conclusions</h4>Relevant changes in mouse RV and LV function following an aortic constriction could be quantified using MRI. The well-controlled models described here open opportunities to assess the added value of new MRI techniques for the diagnosis of heart failure and to study the impact of new therapeutic strategies on disease progression and symptom occurrence.
Project description:Small animal models of afterload stress have contributed much to our present understanding of the progression from hypertension to heart failure. High-sensitivity methods for phenotyping cardiac function in vivo, particular in the setting of compensated cardiac hypertrophy, may add new information regarding alterations in cardiac performance that can occur even during the earliest stages of exposure to pressure overload. We have developed an echocardiographic analytical method, based on speckle-tracking-based strain analyses, and used this tool to rapidly phenotype cardiac changes resulting from afterload stress in a small animal model. Adult mice were subjected to ascending aortic constriction, with and without subsequent reversal of the pressure gradient. In this model of compensated hypertrophic cardiac remodeling, conventional echocardiographic measurements did not detect changes in left ventricular (LV) function at the early time points examined. Strain analyses, however, revealed a decrement in basal longitudinal myofiber shortening that was induced by aortic constriction and improved following relief of the pressure gradient. Furthermore, we observed that pressure overload resulted in LV segmental dyssynchrony that was attenuated with return of the afterload to baseline levels. Herein, we describe the use of echocardiographic strain analyses for cardiac phenotyping in a mouse model of pressure overload. This method provides evidence of dyssynchrony and regional myocardial dysfunction that occurs early with compensatory hypertrophy, and improves following relief of aortic constriction. Importantly, these findings illustrate the utility of a rapid, non-invasive method for characterizing early cardiac dysfunction, not detectable by conventional echocardiography, following afterload stress.
Project description:Animal models of pressure overload are valuable for understanding hypertensive heart disease. We characterised a surgical model of pressure overload-induced hypertrophy in C57BL/6J mice produced by suprarenal aortic constriction (SAC). Compared to sham controls, at one week post-SAC systolic blood pressure was significantly elevated and left ventricular (LV) hypertrophy was evident by a 50% increase in the LV weight-to-tibia length ratio due to cardiomyocyte hypertrophy. As a result, LV end-diastolic wall thickness-to-chamber radius (h/R) ratio increased, consistent with the development of concentric hypertrophy. LV wall thickening was not sufficient to normalise LV wall stress, which also increased, resulting in LV systolic dysfunction with reductions in ejection fraction and fractional shortening, but no evidence of heart failure. Pathological LV remodelling was evident by the re-expression of fetal genes and coronary artery perivascular fibrosis, with ischaemia indicated by enhanced cardiomyocyte Hif1a expression. The expression of stem cell factor receptor, c-Kit, was low basally in cardiomyocytes and did not change following the development of robust hypertrophy, suggesting there is no role for cardiomyocyte c-Kit signalling in pathological LV remodelling following pressure overload.