Aortic Leaflet Perforation During Radiofrequency Ablation

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73537/1/j.1540-8159.1991.tb02732.x.pd

Changes in corticospinal drive to spinal motoneurones following tablet-based practice of manual dexterity

The use of touch screens, which require a high level of manual dexterity, has exploded since the development of smartphone and tablet technology. Manual dexterity relies on effective corticospinal control of finger muscles, and we therefore hypothesized that corticospinal drive to finger muscles can be optimized by tablet‐based motor practice. To investigate this, sixteen able‐bodied females practiced a tablet‐based game (3 × 10 min) with their nondominant hand requiring incrementally fast and precise pinching movements involving the thumb and index fingers. The study was designed as a semirandomized crossover study where the participants attended one practice‐ and one control session. Before and after each session electrophysiological recordings were obtained during three blocks of 50 precision pinch movements in a standardized setup resembling the practiced task. Data recorded during movements included electroencephalographic (EEG) activity from primary motor cortex and electromyographic (EMG) activity from first dorsal interosseous (FDI) and abductor pollicis brevis (APB) muscles. Changes in the corticospinal drive were evaluated from coupling in the frequency domain (coherence) between EEG–EMG and EMG–EMG activity. Following motor practice performance improved significantly and a significant increase in EEG‐EMG(APB) and EMG(APB)‐EMG(FDI) coherence in the beta band (15–30 Hz) was observed. No changes were observed after the control session. Our results show that tablet‐based motor practice is associated with changes in the common corticospinal drive to spinal motoneurons involved in manual dexterity. Tablet‐based motor practice may be a motivating training tool for stroke patients who struggle with loss of dexterity

Genetic variation and exercise-induced muscle damage: implications for athletic performance, injury and ageing.

Prolonged unaccustomed exercise involving muscle lengthening (eccentric) actions can result in ultrastructural muscle disruption, impaired excitation-contraction coupling, inflammation and muscle protein degradation. This process is associated with delayed onset muscle soreness and is referred to as exercise-induced muscle damage. Although a certain amount of muscle damage may be necessary for adaptation to occur, excessive damage or inadequate recovery from exercise-induced muscle damage can increase injury risk, particularly in older individuals, who experience more damage and require longer to recover from muscle damaging exercise than younger adults. Furthermore, it is apparent that inter-individual variation exists in the response to exercise-induced muscle damage, and there is evidence that genetic variability may play a key role. Although this area of research is in its infancy, certain gene variations, or polymorphisms have been associated with exercise-induced muscle damage (i.e. individuals with certain genotypes experience greater muscle damage, and require longer recovery, following strenuous exercise). These polymorphisms include ACTN3 (R577X, rs1815739), TNF (-308 G>A, rs1800629), IL6 (-174 G>C, rs1800795), and IGF2 (ApaI, 17200 G>A, rs680). Knowing how someone is likely to respond to a particular type of exercise could help coaches/practitioners individualise the exercise training of their athletes/patients, thus maximising recovery and adaptation, while reducing overload-associated injury risk. The purpose of this review is to provide a critical analysis of the literature concerning gene polymorphisms associated with exercise-induced muscle damage, both in young and older individuals, and to highlight the potential mechanisms underpinning these associations, thus providing a better understanding of exercise-induced muscle damage

The economic burden of unrecognized vasodepressor syncope

The objective of this study was to describe the cost of prior diagnostic evaluation in patients referred for evaluation of syncope whose history was typical of vasodepressor syncope. Thirty consecutive patients who were referred for evaluation of syncope of undetermined origin and whose history was highly suggestive of vasodepressor syncope participated in this study. These 30 patients represented 19% of 158 patients referred for evaluation of syncope during the period of enrollment. All patients had positive results of an upright-tilt test, confirming the diagnosis of vasodepressor syncope. At the time of evaluation, the type and results of all diagnostic tests that had been performed prior to referral were recorded for each patient. The cost of diagnostic testing was then determined based on the 1991 cost of these tests at the University of Michigan Medical Center.A mean of 4 +/- 2 major diagnostic tests were performed before referral to the University of Michigan Medical Center. The mean and median costs of diagnostic testing per patient prior to referral were $3,763 +/- 3,820 and$2,678 (range: 0 to $16,606) respectively. Six patients underwent no major diagnostic tests prior to referral and, therefore, the cost of major diagnostic testing was zero in these patients. In the remaining patients, the mean and median costs of diagnostic testing per patient were$4,704 +/- 3,713 and $3,777 (range:$1,025 to $16,606) respectively. The results of this study demonstrate that a diagnosis of vasodepressor syncope can be established clinically in approximately 20$16,000 of unnecessary diagnostic testing. A greater awareness of the clinical features of vasodepressor syncope may, therefore, result in significant economic savings.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31087/1/0000764.pd

Determinants of impedance during radiofrequency catheter ablation in humans

Radiofrequency catheter ablation has become the treatment of choice for selected patients with paroxysmal supraventricular tachycardia due to atrioventricular node reentry or the Wolff-Parkinson-White syndrome. 1-3 Despite encouraging results described in several series, the optimal energy delivery strategy has not been defined. Lesion formation occurs during radiofrequency ablation as the result of resistive heating at the electrode-tissue interface.4 The magnitude of heat generation is proportional to power density at the point of contact.5 Electrosurgical units currently being used for radiofrequency ablation have a low source impedance and therefore approximate constant voltage sources. With such a device, one preselects a given output voltage. Applied power is proportional to the square of this output voltage and is inversely proportional to the load impedance imposed by the ablation catheter, patient and indifferent electrode. Thus, the effectiveness of any given energy application may be influenced by the impedance of the system. This study characterizes impedance during radiofrequency catheter ablation in humans, and defines the relation between clinical and ablation parameters, and measured impedance.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30105/1/0000477.pd

Residential Segregation and the Assimilation Process: the Case of Asian Americans in 1980.

The effects of acculturation and socioeconomic status on the residential segregation of Asian Americans are examined with data from the 1980 Census. Comparisons are made with blacks, Hispanics, and European ethnic groups. The data are used initially to describe the overall extent of Asian segregation, and the level and pattern of residential segregation between Asians and groups of similar social and economic backgrounds. Segregation is analyzed further within an assimilation framework which, in part, is based on ecological theory. The principal hypotheses are that greater acculturation or socioeconomic status should lead to lower levels of residential segregation from the majority population. The hypotheses are tested using three different units of analysis: the neighborhood, the metropolitan area, and pairs of racial or ethnic groups. Asian Americans are moderately to highly segregated from the non-Hispanic white population. As social and economic status increases, there is some decline in segregation of Asians from whites with similar social or economic backgrounds. However, segregation persists at a moderate level even for Asians and whites in the highest socioeconomic categories. When the neighborhood is the unit of analysis, it is found that as socioeconomic status increases, the probability of Asian contact with whites also increases. When pairs of groups are the units of analysis, differences in socioeconomic status between Asian groups and the English are found to be directly related to segregation levels. Comparing metropolitan areas reveals that acculturation is the only significant predictor of Asian residential segregation. In contrast, socioeconomic status influences segregation for blacks, Hispanics, and Europeans, and in most instances it has a stronger influence than acculturation. These results suggest that Asian American may be adhering to a structural pluralistic form of assimilation. The sources of data are Summary Tape File 3A and the five percent sample version of the Public-Use Microdata Samples from the Census of Population and Housing for 1980. Data are assembled for the 38 metropolitan areas in the contiguous United States containing the largest Asian American populations. Residential segregation is measured with the index of dissimilarity and the P('*) index, which assesses potential interracial contact.Ph.D.DemographyUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/160984/1/8612563.pd