CINE-MR Imaging of the Normal and Infarcted Rat Heart Using an 11.7 T Vertical Bore MR System

Tyler, Damian J.; Lygate, Craig A.; Schneider, Jürgen; Cassidy, P J; Neubauer, Stefan; Clarke, Kieran

doi:10.1080/10976640500451903

Cited by 29 publications

(41 citation statements)

References 22 publications

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“…It is routinely used in the clinic for the diagnosis and prognosis of heart disease (26), but is not widely available for measurement of cardiac function in rodents. High field strengths are required to obtain sufficient signal-to-noise ratio from the rodent heart, which is several hundred times smaller than the human heart, plus gating strategies are required to compensate for high cardiac and respiratory rates (21)(22)(23)). Yet, cine-MRI produces a wider range of measurements than standard echocardiographic techniques (24,27,28), and fewer geometric assumptions are required, as a contiguous stack of short-axis images can be used to cover the entire length of the left ventricle (15,20).…”

Section: Introductionmentioning

confidence: 99%

Cine‐MRI versus two‐dimensional echocardiography to measure in vivo left ventricular function in rat heart

et al. 2008

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Two-dimensional echocardiography is the most commonly used non-invasive method for measuring in vivo cardiac function in experimental animals. In humans, measurements of cardiac function made using cine-MRI compare favourably with those made using echocardiography. However, no rigorous comparison has been made in small animals. Here, standard short-axis two-dimensional (2D) echocardiography (2D-echo) and cine-MRI measurements were made in the same rats, both control and after chronic myocardial infarction. Correlations between the two techniques were found for end diastolic area, stroke area and ejection fraction, but cine-MRI measurements of ejection fraction were 12+/-6% higher than those made using 2D-echo, because of the 1.8-fold higher temporal resolution of the MRI technique (4.6 ms vs 8.3 ms). Repeated measurements on the same group of rats over several days showed that the cine-MRI technique was more reproducible than 2D-echo, in that 2D-echo would require five times more animals to find a statistically significant difference. In summary, caution should be exercised when comparing functional results acquired using short-axis 2D-echo vs cine-MRI. The accuracy of cine-MRI allows identification of alterations in heart function that may be missed when using 2D-echo.

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Section: Introductionmentioning

confidence: 99%

Cine‐MRI versus two‐dimensional echocardiography to measure in vivo left ventricular function in rat heart

et al. 2008

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“…Left ventricular mass was calculated as myocardial area times slice thickness times myocardial specific gravity (1.05). 26 …”

Section: Magnetic Resonance Imaging Measurements Of Cardiac Functionmentioning

confidence: 99%

Role of Pyruvate Dehydrogenase Inhibition in the Development of Hypertrophy in the Hyperthyroid Rat Heart

et al. 2011

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Background-Hyperthyroidism increases heart rate, contractility, cardiac output, and metabolic rate. It is also accompanied by alterations in the regulation of cardiac substrate use. Specifically, hyperthyroidism increases the ex vivo activity of pyruvate dehydrogenase kinase, thereby inhibiting glucose oxidation via pyruvate dehydrogenase. Cardiac hypertrophy is another effect of hyperthyroidism, with an increase in the abundance of mitochondria. Although the hypertrophy is initially beneficial, it can eventually lead to heart failure. The aim of this study was to use hyperpolarized magnetic resonance spectroscopy to investigate the rate and regulation of in vivo pyruvate dehydrogenase flux in the hyperthyroid heart and to establish whether modulation of flux through pyruvate dehydrogenase would alter cardiac hypertrophy. Methods and Results-Hyperthyroidism was induced in 18 male Wistar rats with 7 daily intraperitoneal injections of freshly prepared triiodothyronine (0.2 mg ⅐ kg Ϫ1 ⅐ d Ϫ1 ). In vivo pyruvate dehydrogenase flux, assessed with hyperpolarized magnetic resonance spectroscopy, was reduced by 59% in hyperthyroid animals (0.0022Ϯ0.0002 versus 0.0055Ϯ0.0005 second Ϫ1 ; Pϭ0.0003), and this reduction was completely reversed by both short-and long-term delivery of dichloroacetic acid, a pyruvate dehydrogenase kinase inhibitor. Hyperpolarized [2-13 C]pyruvate was also used to evaluate Krebs cycle metabolism and demonstrated a unique marker of anaplerosis, the level of which was significantly increased in the hyperthyroid heart. Cine magnetic resonance imaging showed that long-term dichloroacetic acid treatment significantly reduced the hypertrophy observed in hyperthyroid animals (100Ϯ20 versus 200Ϯ30 mg; Pϭ0.04) despite no change in the increase observed in cardiac output.Conclusions-This work has demonstrated that inhibition of glucose oxidation in the hyperthyroid heart in vivo is mediated by pyruvate dehydrogenase kinase. Relieving this inhibition can increase the metabolic flexibility of the hyperthyroid heart and reduce the level of hypertrophy that develops while maintaining the increased cardiac output required to meet the higher systemic metabolic demand. (Circulation. 2011;123:2552-2561.)Key Words: hyperthyroidism Ⅲ magnetic resonance spectroscopy Ⅲ pyruvate dehydrogenase complex T hyroid hormones regulate many aspects of growth, development, and energy metabolism, and are critical for normal cell function in multiple organs. [1][2][3] The heart is particularly sensitive to the action of thyroid hormones, with thyroid dysfunction having detrimental effects on the cardiovascular system. Minimal alterations in circulating thyroid hormone concentrations significantly alter many cardiac parameters. For instance, an increase in circulating thyroid hormone markedly increases heart rate, contractility, and cardiac output. 4 -7 Furthermore, hyperthyroid patients often develop hypertrophy, tachycardia, palpitations, fatigue, and atrial arrhythmias. 8 Clinical Perspective on p 2561Hyperthyroidism is acc...

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“…Mice were anesthetized with 2% (vol/vol) isofluorane in O 2 and were positioned supine in a purpose-built cradle. Cine MR imaging was carried out using an 11.7-T MR system with a 40-mm birdcage coil (Rapid Biomedical) as described (34) and summarized in SI Materials and Methods. T* 2 .…”

Section: Methodsmentioning

confidence: 99%

Cardiac ferroportin regulates cellular iron homeostasis and is important for cardiac function

Lakhal‐Littleton

Wolna

Carr

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Iron is essential to the cell. Both iron deficiency and overload impinge negatively on cardiac health. Thus, effective iron homeostasis is important for cardiac function. Ferroportin (FPN), the only known mammalian iron-exporting protein, plays an essential role in iron homeostasis at the systemic level. It increases systemic iron availability by releasing iron from the cells of the duodenum, spleen, and liver, the sites of iron absorption, recycling, and storage respectively. However, FPN is also found in tissues with no known role in systemic iron handling, such as the heart, where its function remains unknown. To explore this function, we generated mice with a cardiomyocyte-specific deletion of Fpn. We show that these animals have severely impaired cardiac function, with a median survival of 22 wk, despite otherwise unaltered systemic iron status. We then compared their phenotype with that of ubiquitous hepcidin knockouts, a recognized model of the iron-loading disease hemochromatosis. The phenotype of the hepcidin knockouts was far milder, with normal survival up to 12 mo, despite far greater iron loading in the hearts. Histological examination demonstrated that, although cardiac iron accumulates within the cardiomyocytes of Fpn knockouts, it accumulates predominantly in other cell types in the hepcidin knockouts. We conclude, first, that cardiomyocyte FPN is essential for intracellular iron homeostasis and, second, that the site of deposition of iron within the heart determines the severity with which it affects cardiac function. Both findings have significant implications for the assessment and treatment of cardiac complications of iron dysregulation.

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CINE-MR Imaging of the Normal and Infarcted Rat Heart Using an 11.7 T Vertical Bore MR System

Cited by 29 publications

References 22 publications

Cine‐MRI versus two‐dimensional echocardiography to measure in vivo left ventricular function in rat heart

Cine‐MRI versus two‐dimensional echocardiography to measure in vivo left ventricular function in rat heart

Role of Pyruvate Dehydrogenase Inhibition in the Development of Hypertrophy in the Hyperthyroid Rat Heart

Cardiac ferroportin regulates cellular iron homeostasis and is important for cardiac function

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