Matthew S Hanna

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BACKGROUND Aerobic fitness (VO(2)max) is a key component of youth fitness testing. Criterion-referenced (CR) assessments are used in FITNESSGRAM(®) to assess health risk. PURPOSE The purpose of this study was to develop and cross-validate regression models to estimate VO(2)max from Progressive Aerobic Cardiovascular Endurance Run (PACER) 20-m shuttle run(More)
BACKGROUND The shortest excitable gap during reentry may determine responses to pacing and antiarrhythmic drugs. The resetting response has been used clinically to assess the excitable gap, but it cannot directly indicate the shortest excitable gap. METHODS AND RESULTS We studied resetting in the in vitro canine atrial tricuspid ring using an adjustable(More)
We investigated the basis for the alterations in the intracellular potassium and sodium activity occurring in subendocardial Purkinje fibers surviving in 24-hour infarcts by examining ion activities in these Purkinje fibers removed from infarcting hearts at earlier times. Specifically, we examined intracellular potassium activity, sodium activity, and pH at(More)
The excitable gap of a reentrant circuit has both temporal (time during the cycle length that the circuit is excitable) and spatial (length of the circuit that is excitable at a given time) properties. We determined the temporal and spatial properties of the excitable gap in reentrant circuits caused by nonuniform anisotropy. Myocardial infarction was(More)
We hypothesized that drugs with rapid recovery kinetics from use-dependent sodium channel block could promote oscillatory termination of reentry by enhancing interval-dependent conduction. Mechanisms of termination were related to properties of the reentrant circuit. Nine adjustable reentrant preparations were used in which the canine atrial tricuspid ring(More)
BACKGROUND Resetting has been used to characterize reentrant circuits causing clinical tachycardias. METHODS AND RESULTS To determine the mechanisms of resetting, sustained ventricular tachycardia was induced in dogs with 4-day-old myocardial infarctions by programmed stimulation. Premature stimulation was accomplished from multiple regions within(More)
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