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Biomedical subjects

J B Shea

Publications and source records attributed to J B Shea.

8 recordsLinked to original sources
PubMed1993

Alterations of heart rate and of heart rate variability after radiofrequency catheter ablation of supraventricular tachycardia. Delineation of parasympathetic pathways in the human heart.

BACKGROUND: Persistent inappropriate sinus tachycardia has been reported as a complication after radiofrequency (RF) ablation of the fast atrioventricular (AV) nodal pathway. The purpose of this study was to evaluate the prevalence of this complication and its mechanism using heart rate variability analysis. METHODS AND RESULTS: Time and frequency domain analysis of heart rate was performed in the electrophysiology laboratory immediately before and immediately after RF ablation in 64 patients with supraventricular tachycardia. Ablation targets in these 64 patients included the fast AV nodal pathway (n = 3), the slow AV nodal pathway (n = 14), a posteroseptal accessory pathway (n = 23), and a left lateral accessory pathway (n = 24). A control group of 21 patients undergoing diagnostic study but not ablation underwent identical analysis immediately before and at the conclusion of their procedure. Patients undergoing ablation also had time and frequency domain analysis performed on ambulatory 24-hour Holter tapes recorded before ablation and at 1 day, 1 month, and 6 months after ablation. Compared with preablation values, time domain analysis immediately after ablation revealed a significant increase in mean heart rate and significant reductions in heart rate variability expressed as SD, MSSD, and PNN50 in patients undergoing AV nodal modification or posteroseptal accessory pathway ablation. Frequency domain analysis revealed marked attenuation of high frequency (0.15 to 0.40 Hz) components, indicating parasympathetic denervation. These acute changes were not seen after ablation of left lateral accessory pathways or after diagnostic study without ablation. Time and frequency domain analysis of 24-hour ambulatory Holter monitors performed serially after ablation revealed resolution of abnormalities of heart rate and of heart rate variability 1 to 6 months after ablation, with reappearance of the high frequency parasympathetic component suggestive of reinnervation. CONCLUSIONS: RF ablation in the anterior, mid, and posterior regions of the low interatrial septum may disrupt preganglionic or postganglionic parasympathetic fibers located in these regions that are destined to innervate the sinus node. Such fibers become more scarce along the left AV groove with increasing distance from the posteroseptal space. Parasympathetic denervation may be one mechanism for persistent inappropriate sinus tachycardia after RF ablation.

Adult↗
PubMed1991

When forgetting benefits motor retention.

Recent research (Lee & Weeks, 1987; Weeks, Lee, & Elliott, 1987) investigating the processes responsible for the contextual interference phenomenon has used a modified short-term motor retention paradigm to support the reconstruction explanation (Lee & Magill, 1985; Magill, 1989; Magill & Hall, 1990). The present experiment was an extension of these experiments in which forgetting of an acquisition task was induced through performance of either a similar or dissimilar distractor task during the intertrial interval. The effects of an extra practice trial with the acquisition task as well as no activity during the intertrial interval were also investigated. In addition, forgetting of the acquisition task was assessed prior to a reconstruction trial, which immediately preceded a 2-min filled retention interval. Both similar and dissimilar distractor tasks caused equivalent amounts of forgetting of the acquisition task prior to the reconstruction trial. However, retention of the acquisition task was significantly improved if its reconstruction occurred following forgetting due to interference from performance of a similar distractor task. These findings suggest forgetting and subsequent reconstruction alone are not sufficient for improved retention. These processes must occur in the context of a similar task for improved retention.

Analysis of Variance↗
PubMed1984

Motor control.

The acquisition of motor skills involves learning, memory, and transfer as well as attention. The aspects of motor control most relevant for everyday practice are the conditions of practice, the knowledge of results, and the assessment of athletes to identify talented performers. The optimal conditions for practice and methods for developing a test battery for use in a sports tryout are discussed.

Attention↗
PubMed1978

Effects of relative frequency of knowledge of results on retention of a motor skill.

The effects of relative frequency of knowledge of results on the retention of a motor skill was studied. Adams' theory (1971) contends that the perceptual trace of a criterion position gains on increment of strenth each time the feedback stimuli associated with the criterion position are experienced and that it is the strength of the perceptual trace that determines retention. Schmidt's theory (1975), however, suggests that the recognition schema is updated only on trials on which the feedback stimuli associated with the criterion position are experienced in conjunction with knowledge of results and that it is the precision of the recognition schema that determines retention. Two experiments were conducted. The results provided evidence contrary to Adams' theory. Schmidt's theory, however, was only partially supported.

Humans↗