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INSIDE THIS ISSUE OF JACC

Inside This Issue of JACC

	Non-Invasive Coronary Angiography

Top Non-Invasive Coronary... Non-Invasive Coronary... Delayed Enhancement Magnetic... Left Ventricular Function Molecular and Stem Cell... Molecular and Stem Cell...

	Non-Invasive Coronary Angiography

Top Non-Invasive Coronary... Non-Invasive Coronary... Delayed Enhancement Magnetic... Left Ventricular Function Molecular and Stem Cell... Molecular and Stem Cell...

 
Improving the Utility of Coronary Magnetic Resonance Angiography.  
Two limitations of magnetic resonance imaging to detect coronary stenoses are the time to acquire the images and decreased resolution due to motion during the cardiac cycle. Sakuma and colleagues describe a new coronary magnetic resonance protocol to address these issues, and compare this protocol to conventional coronary angiography. To reduce the time of the study, they performed whole heart scans, rather than focusing first on the left anterior descending artery and then rescanning the right coronary artery (RCA). To address the motion issue, they first determined whether the RCA moved more during diastole or systole, and then gated acquisition to only obtain images during that phase. The time to acquire a scan was reduced to <13 min through this "whole heart" protocol. The sensitivity to identify significant stenoses was 82%, but 14% of patients had to be excluded due to "irregular" breathing patterns. An accompanying editorial points out that this technique is an improvement over previous coronary magnetic resonance angiography protocols, but is not yet ready for widespread adoption. See pages 1946 and 1951. See figure.

	Delayed Enhancement Magnetic Resonance

Top Non-Invasive Coronary... Non-Invasive Coronary... Delayed Enhancement Magnetic... Left Ventricular Function Molecular and Stem Cell... Molecular and Stem Cell...

 
Late Gadolinium Enhancement Predicts Outcomes in Non-Ischemic Cardiomyopathies.  
Late gadolinium enhancement (LGE) on cardiac magnetic resonance accurately measures previously infarcted myocardium, but may occur in patients without coronary atherosclerosis. Typically, LGE spares the subendocardium in non-coronary artery disease patients, suggesting a different pathophysiology. Assomull and colleagues studied more than 100 subjects with idiopathic dilated cardiomyopathies, 35% of whom showed areas of mid-wall LGE. Those with LGE had worse outcomes, with more frequent hospitalizations, higher rates of ventricular arrhythmias, and a trend toward increased mortality. These associations remained predictive after multivariable analysis. An editorial by Kramer analyzes the utility of LGE to stratify risk in patients with ischemic and idiopathic cardiomyopathies, suggesting that LGE appears to accurately identify those in need of more aggressive therapies. See pages 1977 and 1986. See figure.

	Left Ventricular Function

Top Non-Invasive Coronary... Non-Invasive Coronary... Delayed Enhancement Magnetic... Left Ventricular Function Molecular and Stem Cell... Molecular and Stem Cell...

 
Reduced Longitudinal Strain Differentiates Transmural from Subendocaridal Infarctions.   Distinguishing transmural from non-transmural infarctions has important prognostic implications regarding the potential for contractile recovery after revascularization, but it is difficult with standard echocardiography. Chan and colleagues hypothesized that the different fiber orientations in the anatomic layers of the heart could be used to distinguish the type of infarct. Using speckle tracking during dobutamine infusion, longitudinal and radial strain and strain rates were calculated for each wall segment. Preservation of the epicardial layers after subendocardial infarctions resulted in reduced circumferential strain for transmural but not subendocardial infarctions, whereas both types of infarction reduced longitudinal strain, which is mostly generated by the subendocardial fibers. This technique may be useful clinically to judge the likelihood of improvement after revascularization in previously infarcted segments. See page 2026.

	Molecular and Stem Cell Imaging

Top Non-Invasive Coronary... Non-Invasive Coronary... Delayed Enhancement Magnetic... Left Ventricular Function Molecular and Stem Cell... Molecular and Stem Cell...

 
Hybrid PET-CT Can Be Used to Monitor Gene Transfection.  
Although adenoviral transfection of targeted proteins offers great promise, there are still many questions to be answered. Wagner and colleagues describe a novel use of a hybrid positron emission tomography-computed tomography scanner, targeted isotopes, and reporter genes to localize and identify areas of successful gene transfection. This will help to optimize transfection techniques. The use of myocardial perfusion measurements with [¹³N]ammonia will allow more accurate comparison of hemodynamic efficacy, which should allow for better comparisons of techniques. This combined modality imaging should allow for more rapid assessment of gene transfection experiments. See page 2107. See figure.

	Molecular and Stem Cell Imaging

Top Non-Invasive Coronary... Non-Invasive Coronary... Delayed Enhancement Magnetic... Left Ventricular Function Molecular and Stem Cell... Molecular and Stem Cell...

 
MDCT and CMR Demonstrate Cardiac Regeneration From Stem Cells.  
Although the injection of mesenchymal stem cells into recently infarcted myocardium seems to improve left ventricle function, there is considerable controversy as to whether or not this procedure actually generates viable, contracting tissue. Amado and colleagues used multi-detector computed tomography (MDCT) and cardiac magnetic resonance imaging to study a swine model of myocardial infarction after treatment with either mesenchymal stem cells or placebo. MDCT demonstrated increasing thickness of sub-endocardial viable myocardium in the infarct zone in treated animals and a corresponding reduction in infarct scar, whereas no such changes were detected in control animals. Tagged magnetic resonance imaging demonstrated time-dependent recovery of active contractility paralleling new tissue appearance. This non-invasive imaging technique demonstrates an enlarging area of actively contracting myocardial cells and helps provide evidence that treatment with mesenchymal stem cells may benefit post-myocardial infarction patients. See page 2116. See figure.

Related articles in JACC:

Differentiation of Subendocardial and Transmural Infarction Using Two-Dimensional Strain Rate Imaging to Assess Short-Axis and Long-Axis Myocardial Function

Jonathan Chan, Lizelle Hanekom, Chiew Wong, Rodel Leano, Goo-Yeong Cho, and Thomas H. Marwick
JACC 2006 48: 2026-2033. [Abstract] [Full Text]  

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