Troponin from skeletal muscle

J Am Coll Cardiol, doi:10.1016/j.jacc.2011.08.026 (Published online 28 September 2011)

Diseased Skeletal Muscle

A Noncardiac Source of Increased Circulating Concentrations of Cardiac Troponin T

Allan S. Jaffe, MD*,,*, Vlad C. Vasile, MD, PhD*,, Margherita Milone, MD, PhD, Amy K. Saenger, PhD*, Kalen N. Olson, PhD and Fred S. Apple, PhD

Dr. Allan S. Jaffe, Cardiovascular Division, Gonda 5, Mayo Clinic and Medical School, 200 First Street SW, Rochester, Minnesota 55905 (Email: Jaffe.Allan@Mayo.edu).

Objectives: The purpose of this study was to determine whether there is immunoreactive cardiac troponin T (cTnT) expression in diseased skeletal muscle that might cause possible false-positive increases in cTnT.

Background: Cardiac troponin (I or T) is the biomarker of choice for the diagnosis of cardiac injury. Recently, we were presented with a case that challenged the specificity of cTnT.
Methods: Patients with myopathies seen in the Neuromuscular Clinic at the Mayo Clinic were screened for increases in cTnT. If present, an assay for cTnI was performed. If normal, skeletal biopsy tissue was obtained for Western blot analysis using the capture and detection antibodies from both the fourth-generation and high-sensitivity cTnT assays. Results were compared with findings in normal cardiac tissue.

Results: Sixteen patients had increases in cTnT but not cTnI. All had a myopathy by clinical evaluation, clinical testing, and biopsy. Four residual biopsy samples were obtained. All 3 antibodies used in the cTnT (M11.7, M7) and high-sensitivity cTnT (5D8, M7) assays were immunoreactive with a 37- to 39-kDa protein in all 4 diseased skeletal muscle biopsy specimens and in cardiac tissue. A second immunoreactive isoform (34 to 36 kDa) was also found in 1 patient. None of the noncardiac control tissues expressed immunoreactive protein.

Conclusions: These results document that there are forms in diseased skeletal muscle that could cause increases in circulating levels of cTnT. These increases could reflect re-expressed isoforms. Clinicians need to be aware of the possibility that noncardiac increases in cTnT may occur and lead to a possible false-positive diagnosis of cardiac injury when skeletal muscle pathology is present.

Echo, Fetal echo: Predicting need for balloon atrial septostomy in d-TGA

J Am Soc Echocardiogr. 2011 Apr;24(4):425-30. Epub 2011 Feb 15.

Fetal predictors of urgent balloon atrial septostomy in neonates with complete transposition.

Punn R, Silverman NH.

Source

Stanford University, Lucile Packard Children's Hospital, Palo Alto, California, USA.

Abstract

BACKGROUND:

In complete transposition of the great vessels, a restrictive patent foramen ovale leads to inadequate circulatory mixing and severe cyanosis. Urgent balloon atrialseptostomy (BAS) improves mixing and bridges neonates to surgery. Several studies have determined risk factors in utero for poor postnatal outcomes in complete transposition of the great vessels, particularly a restrictive patent foramen ovale and ductus arteriosus. In addition to these risk factors, we studied two new features, a hypermobile septum and reverse diastolic patent ductus arteriosus shunt, to determine which patients will require an urgent BAS.

METHODS:

We reviewed all 26 fetuses from 2001 to 2010 with complete transposition of the great vessels and closely examined the patent foramen ovale and septum primum for hypermobility, restriction, flat appearance, or redundancy. We defined hypermobility as a septum primum flap that oscillates between both atria. We also examined the ductus size and shunting pattern to evaluate whether these features contributed to urgent BAS.

RESULTS:

In total, 14 of 26 fetuses required urgent BAS with improved cyanosis. Nine fetuses had an urgent BAS and a hypermobile septum, and 12 fetuses had no urgent BAS or hypermobile septum. Eight fetuses had an urgent BAS and a reverse diastolic patent ductus arteriosus, and 11 fetuses had no urgent BAS or reverse diastolic patent ductus arteriosus. A hypermobile septum and reverse diastolic patent ductus arteriosus had a significant association with urgent BAS (P < .01, sensitivity = 0.64 and 0.57, specificity = 1.0 and 0.92, positive predictive value = 1.0 and 0.89, negative predictive value = 0.71 and 0.65). No fetus had a restrictive patent foramen ovale/ductus arteriosus.

CONCLUSION:

A hypermobile septum and reverse diastolic patent ductus arteriosus are new prenatal findings to help predict the need for an urgent BAS postnatally in patients with complete transposition of the great vessels.