Venkat Ramesh Iyer

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Heart failure is accompanied by a loss of the orderly disposition of transverse (T)-tubules and a decrease of their associations with the junctional sarcoplasmic reticulum (jSR). Junctophilin-2 (JP2) is a structural protein responsible for jSR/T-tubule docking. Animal models of cardiac stresses demonstrate that down-regulation of JP2 contributes to T-tubule(More)
It is known that cardiac myocytes contain three categories of calcium release units (CRUs) all bearing arrays of RyR2: peripheral couplings, constituted of an association of the junctional SR (jSR) with the plasmalemma; dyads, associations between jSR and T tubules; internal extended junctional jSR (EjSR)/corbular jSR that is not associated with(More)
BACKGROUND A human genetic variant (Ser96Ala) in the sarcoplasmic reticulum (SR) histidine-rich Ca(2+)-binding (HRC) protein has been linked to ventricular arrhythmia and sudden death in dilated cardiomyopathy. However, the precise mechanisms affecting SR function and leading to arrhythmias remain elusive. METHODS AND RESULTS We generated transgenic mice(More)
Exchanges of matrix contents are essential to the maintenance of mitochondria. Cardiac mitochondrial exchange matrix content in two ways: by direct contact with neighboring mitochondria and over longer distances. The latter mode is supported by thin tubular protrusions, called nanotunnels, that contact other mitochondria at relatively long distances. Here,(More)
In the outpatient setting, children who present with syncope routinely undergo electrocardiograms (ECG). Because of concerns for hypertrophic cardiomyopathy, children with syncope meeting ECG criteria for left ventricular hypertrophy (LVH) will frequently undergo an echocardiogram. Our objectives were to determine whether Davignon criteria for ECG waves(More)
BACKGROUND Cardiovascular conditions rank sixth in causes of death in 1- to 19-year-olds. Our study is the first analysis of the cardiovascular death data set from the National Center for the Review and Prevention of Child Deaths, which provides the only systematic collection of cardiovascular deaths in children. METHODS We developed an analytical data(More)
BACKGROUND The only systematic collection of cardiovascular (CV) deaths in children resides in the database derived from the Case Reporting System of the National Center for the Review and Prevention of Child Deaths (NCRPCD). We describe the process used to develop an analytical data set to inform our understanding of CV deaths in children from this(More)
In cardiac muscle, calmodulin (CaM) regulates the activity of several membrane proteins involved in Ca2+ homeostasis (CaV1.2; RyR2, SERCA2, PMCA). Three engineered amino acid substitutions in the CaM binding site of the cardiac ryanodine receptor (RyR2) in mice (Ryr2 ADA/ADA ) strongly affect cardiac function, with impaired CaM inhibition of RyR2, reduced(More)
BACKGROUND Exercise stress testing has shown diagnostic utility in adult patients with long-QT syndrome (LQTS); however, the QT interval adaptation in response to exercise in pediatric patients with LQTS has received little attention. METHODS AND RESULTS One-hundred fifty-eight patients were divided into 3 groups: Those with LQTS type 1 (LQT1) or LQTS(More)