The purpose of this study was to noninvasively extract information about the size and muscle fiber density of muscular units through the inverse analysis of surface electromyograms. Surface motor unit action potentials (MUAPs) were recorded with a multi-channel electrode array arranged along the circumference direction of the biceps brachii. The depth and intensity of equivalent current dipoles were estimated through the inverse analysis of surface MUAPs. The simulation of inverse analysis of surface potentials generated by the muscular unit models showed that the relationship between the depth and the intensity depends on the muscular unit size and muscle fiber density.
In the simulation, we systematically varied the model parameters including distance from the skin, radius, and fiber density and used the inverse analysis to estimate the depth and intensity of current dipoles. And, our method to estimate the radius and fiber density of muscular units using estimated depth and intensity is demonstrated. Mean values (± SD) estimated from the surface MUAPs were 3.0±1.8mm for depth and 13.8±32.0nAm for intensity. The estimated distance ranged from slightly less than 1 mm to slightly more than 2 mm. The estimated radius ranged from 1.8 to 4.6 mm and fiber density from 0.7 to 5.4 fibers/mm².

We have developed a method for estimating the depth and intensity of muscular unit represented as equivalent current dipoles by the inverse analysis of surface electromyograms (EMGs) . In this study, the validity of the locations of current dipoles estimated through the inverse analysis was verified by animal experiments. Surface motor unit action potentials (MUAPs) were recorded from the gastrocnemius muscle activated by electrical stimulation at the ventral root of lumbar spinal cord (L4 or L5) of rats. After recording the surface MUAPs for the inverse analysis and glycogen depletion of active muscle fibers by repeated electrical stimulation, periodic acid-Schiff (PAS) staining was used to determine the position of muscle fibers belonging to an active single motor unit. In the results of the inverse analysis, the values of ‘goodness of fit’ between measured and calculated MUAP were 71%, 79% and 85%. Estimated depths of current dipoles ranged from 1.8 mm to 5.9 mm. The locations estimated through the inverse analysis were more medial and shallower than the actual distribution of active muscle fibers determined by PAS staining. These errors were probably caused by the effects of the boundary in the model, the relationship between the measurement area and the location of an active motor unit, and the artifacts such as deformation of the muscle during dissection and freezing.

Objective : The ascending aortic cannulation (Ao-C) is the routine procedure for cardiopulmonary bypass (CPB) in our hospital. However, for patients with diseased ascending aorta, such as severely calcified aorta, dissected or aneurysmal aorta, we used brachiocephalic artery (BCA) cannulation. The effectiveness and simplicity of BCA cannulation was evaluated. Methods : For patients with diseased ascending aorta, BCA was cannulated when the diameter of BCA is larger than 10 mm and is free from calcification, since January 2013. There were 62 patients who underwent aortic valve replacement (AVR) for aortic valve stenosis and BCA cannulation was applied for 11 patients. Standard Ao-C was used for remaining 51 patients. There were 44 patients with dissected or aneurysmal ascending aorta and BCA cannulation was applied for 7 patients, axillary artery perfusion was used for 15 patients and standard Ao-C was used for 22 patients. Consciousness level at the time of awaking from general anesthesia and any complication related with BCA cannulation was evaluated for the effectiveness. Simplicity was evaluated by the time required to establish CPB after skin incision. Results : In AVR patients, there was 1 patient with delayed consciousness level recovery with BCA cannulation and this patient was found to have cerebral infarction by CT. Intraoperative aortic dissection, probably due to BCA cannulation was observed in 1 patient, very old fragile and long period steroid user. In diseased ascending aorta patients, no patient suffered neurological accident nor any complication due to cannulation. In AVR patients, the time required to establish CPB after skin incision was 51+/-9 min in BCA cannulation and 47+/-10 min in Ao-C patients (p=0.34). In diseased ascending aorta patients, the time required to establish CPB after skin incision was 49+/-49 min in BCA cannulation and 51+/-16 min (p=0.82). Conclusion : BCA cannulation is a very simple and safe technique to establish CPB for patients with diseased ascending aorta. However great care should be taken, and BCA cannulation should be avoided for the long term steroid users or patients with connective tissue disease.

Angles of the shoulder joint are usually defined in each of the sagittal, coronal, and horizontal planes passing through the center of the shoulder joint. One of the problems with this method is the difficulty of describing some positions of the shoulder joint such as the anterolaterally elevated position. In 2005, the International Society of Biomechanics proposed a recommendation on definitions of joint coordinate systems including the shoulder based on Euler/Cardan angles, which have often been used for the purpose of research on shoulder joint movement in daily activities. With this definition, however, it still remains impossible to define the angle of axial rotation in the hanging down position. Also, Codman's paradox, the phenomenon where the rotation angle of the shoulder changes after motions without axial rotation of the arm, remains unsolved. To solve these problems, a new method to define the angle of shoulder axial rotation, the non-singular method, has been proposed. This review describes the history and the problems of the methods used to define shoulder angles, and presents this new method of definition.

The purpose of this study is to examine the validity of muscle fatigue evaluation using maximum voluntary torque (MVT), and to identify the dependence of individual's tolerance for fatigue on the capacity to exert MVT. In 14 young male subjects (10 regular exercisers and 4 sedentary), MVT was measured during isometric knee extension, and voluntary activation (VA), which reflects motor unit activation, was evaluated using the twitch interpolation technique. In addition, the maximum endurance time (ET) was measured, and behavior of the mean power frequency (MPF) and the average rectified value (ARV) of surface EMGs from the vastus lateralis muscle were analyzed during constant force isometric contractions of 60% MVT (short-duration fatigue task; SDF task) and 20% MVT (long-duration fatigue task; LDF task) . Correlations were examined among these five variables.
The results were as follows:
1) Subjects were divided into a high voluntary activation group (HVA group) and a low voluntary activation group (LVA group) . Four sedentary subjects were included in the latter group.
2) MVT was significantly larger in the HVA group than in the LVA group (p<0.01) . A significant positive correlation (r=0.72) was found between MVT and VA (p<0.01) .
3) A significant negative correlation (r=-0.71) was found between MVT and endurance time (ET) for the LDF task (p<0.01) . The ET was significantly longer in the LVA group than in the HVA group (p<0.01) .
4) The MPF of voluntary EMG decreased consistently, as ARV increased during isometric contraction in both tasks (p<0.01), indicating the development of fatigue in the muscle. The final change of MPF relative to the initial value was significantly greater in the SDF task than in the LDF task (p<0.05) .
5) A significant correlation (r=-0.83) was seen between the relative change in MPF and ARV in the SDF task (p<0.01) .
6) For the SDF task, the final change of MPF and ARV relative to the initial value was significantly greater in the LVA group than in the HVA group (p<0.05) .
These results indicate that tolerance for local muscle fatigue usually evaluated as maximum endurance time, may depend on individual differences in VA, the VA, in turn, depending on adapta-tion to exercise, and that there appears to exist a corresponding adaptative strategy of the neuromuscular system during fatiguing contractions. Usefulness of our procedure using the twitch interpolation technique in evaluating muscle fatigue was also suggested.

We studied the mechanism for slowing surface electromyography (EMG) during fatiguing contraction using superimposed M-wave analysis. Seven healthy male subjects exerted 60% maximum voluntary contraction of isometric abductions in the left first dorsal interosseous muscle (FDI) until exhaustion. Simultaneously with voluntary contractions, the ulnar nerve was electrically stimulated at supramaximal intensity, and volitional EMG and superimposed M-waves were obtained. We examined the behavior of muscle fiber conduction velocity (MFCV) and median frequency (MDF) for both EMG, with the following results:
1) MFCV calculated from volitional EMG of FDI was about 6 m/s during 60% MVC.
2) The waveform of voluntary EMG detected from FDI slowed in all subjects during fatiguing contraction at 60% MVC, indicating fatigue had developed in the muscle.
3) As fatigue progressed, the waveform of the superimposed M-wave tended to decrease in amplitude and increase in duration.
4) As fatigue progressed, MDF and MFCV in volitional EMG decreased significantly (p<0.04) . The rate of change was larger in MDF than in MFCV (p<0.01) .
5) As fatigue progressed, MDF and MFCV in the superimposed M-wave decreased significantly (p<0.01) . The rate of change was larger in NIDF than in MFCV (p<0.05) .
These results suggested that MFCV and other peripheral factors affected the slowing of volitional EMG. Elongation of the depolarization zone in muscle fiber is proposed as a peripheral factor.

The purpose of this study was to examine the effects of short-term immobilization on the maximum voluntary contraction (MVC) force. The first dorsal interosseus (FDI) of 10 healthy male adults was immobilized for 1 week using casting tape. Atrophy of the muscle was estimated from a cross sectional view of magnetic resonance images (MRI) . To clarify the factors of a peripheral neuromuscular system contributing to the change in the MVC force, twitch force at rest was measured. The contribution of central factors was estimated from a voluntary activation (VA) index, which was obtained by the twitch interpolation method.
The MRI showed no significant changes in the cross sectional area. The MVC force declined after immobilization (p<0.01), and recovered after 1 week from the termination of immobilization (p<0.01) . Both the twitch force at rest and the VA at MVC declined after immobilization (p<0.01), and recovered after 1 week (p<0.05) .
The results indicate that the temporary decline of the MVC force was not accompanied by atrophy of the muscle. Furthermore the decline of the MVC was caused both by the deterioration of peripheral and central functions in the neuromuscular system. Possible factors in the peripheral and central neuromuscular systems affected by the immobilization were discussed.

We evaluated motor unit (MU) fatigue in the first dorsal interosseous muscle (FDI) using the collision principle. Eight healthy men exerted 70% (short-duration fatigue task: SDF task) and 30% (long-duration fatigue task: LDF task) maximum voluntary contraction of isometric abductions in the left FDI until exhausted. Before and after voluntary contractions, the ulnar nerve was stimulated at the wrist and elbow with supramaximal intensity, and a pair of M-waves was obtained. Fatiguerelated changes were studied in mean power frequency (MPF), averaged rectified value (ARV) calculated from surface EMG, and motor nerve conduction velocity (MCV) and distribution of motor nerve conduction velocity (DMCV) calculated from M-waves. The MPF of voluntary EMG decreased, whereas ARV increased significantly during SDF and LDF tasks, indicating fatigue had developed in the FDI. Endurance was significantly shorter in the SDF task than in the LDF task (p<0.01), whereas differences between tasks were not seen in MPF and ARV changes. Tasks did not affect MCV, but lower components in DMCV increased for both tasks. Increased lower components were larger in the LDF task than in the SDF task. The shift in DMCV indicated that fatigued MUs stopped activity and enduring MUs, which had lower axon conduction velocity, were activated selectively. These results suggest that the collision principle is applicable in evaluating motor unit fatigability.

Background : Post-operative fluid management after cardiac valvular surgery is very important. In our institute, carperitide 0.0125 γ was started during surgery and oral furosemide 20-40 mg/day and spironolactone 25 mg/day were started at post-operative day (POD) 1 as the standard therapy. Tolvaptan, vasopressin V2 receptor antagonist, was started when fluid retention such as pleural effusion occurred. With this strategy, the frequency of pleural drainage was more than 40%. Therefore we changed our standard therapy in February 2018. In this new standard therapy, carperitide (0.0125 γ) was started and maintained until oral intake became possible and tolvaptan 7.5 mg was started with furosemide 20 mg and spironolactone 25 mg as oral medicine usually at POD 1. In this study, whether tolvaptan prevents pleural effusion or not after cardiac surgery was examined. Subjects and Methods : Sixty-four patients were operated during February 2017 and December 2018 were included in this study. Thirty-two patients operated in the period until January 2018 served as control group and were compared with 32 patients for whom tolvaptan was started on POD 1 (tolvaptan group). Results : There was no significant difference between two groups for background, operative procedure, operation time, cardiopulmonary bypass time, aortic cross clamp time and fluid balance during procedure. Tolvaptan was given to all patients in the tolvaptan group and in 22% of patients in the control group. Oral furosemide dose (tolvaptan group 21±5 mg/day, control group 31±20 mg/day, p＝0.0112), and the frequency of patients with intravenous furosemide administration (tolvaptan group 9%, control group 44%, p＝0.0038) were significantly less in tolvaptan group. In the tolvaptan group, intravenous furosemide administrated only once in all patients, whereas the frequency of intravenous furosemide administration was 1-32 times, average 6.6 times in control group. Tolvaptan was stopped within 1 week because of too much urination in two patients and the elevation of liver enzyme in two patients without any adverse effects. Post-operative urination volume until POD 5 did not differ. In both groups, body weight increased at POD 1 and 2 and returned to pre-operative weight at POD 3. Pleural effusion was significantly less in the tolvaptan group at POD 3 (tolvaptan group : none 66%, small amount 22%, moderate amount 3%, drain tube inserted 9%, control group : none 16%, small amount 34%, moderate amount 13%, drain tube inserted 38%, p＝0.0003), at POD 7 (tolvaptan group : none 72%, small amount 28%, vs., control group : none 47%, small amount 19%, moderate amount 22%, drain tube inserted 13%, p＝0.0041) and at discharge (tolvaptan group : none 94%, small amount 6%, vs., control group : none 69%, small amount 22%, moderate amount 9%, p＝0.0301). The frequency of pleural drainage was also less in the tolvaptan group (tolvaptan group 9.4%, control group 44%, p＝0.0038). Conclusion : After cardiac valvular surgery, tolvaptan started at POD 1 is very effective to reduce the frequency of pleural effusion and pleural drainage, and careful checking for too much urination and the elevation of liver enzymes is mandatory.

Purpose : Easy and safe implantability, good post-operative valve function and good long-term durability are required for any bioprosthetic valve implanted in aortic position. The Carpentier Edwards Perimount Magna valve (Magna) was introduced in 2009 and the St. Jude Medical Trifecta valve (Trifecta) was introduced in 2012 to our institution. In this study, we compared implantability, early post-operative valve function and structural valve deterioration (SVD) between these two valves. Patients and Methods : Between January 2009 and December 2019, Magna or Trifecta were electively implanted for 254 patients (Magna 151 patients and Trifecta 103 patients) and these patients were included in this study. Implantability was evaluated by occurrence of intraoperative valve dysfunction. Early post-operative valve function was evaluated by mean pressure gradient (m-PG) and indexed aortic valve area (AVAI) by ultrasonography performed 10 days after surgery. The relationship between indexed bioprosthetic valve orifice area calculated from internal diameter (GOAI) and AVAI was evaluated. If there was a significant relationship between GOAI and AVAI, maximum body surface area (BSA) to obtain AVAI≥0.85 cm2/m2 was estimated from 99% reliable interval of regression line. Results : Age, gender, and BSA did not differ between the two groups. There was no intraoperative valve dysfunction in Magna ; however we experienced one patient with severe aortic regurgitation due to stent distortion by the aortic wall during surgery with the 25 mm Trifecta valve. For this patient, Trifecta was replaced with Magna intra-operatively. In the 19 mm valve, AVAI was significantly larger (1.12±0.27 cm2/m2 vs. 0.88±0.21 cm2/m2, p<0.001) and m-PG was significantly lower (8.7±2.7 mmHg vs. 17.2±6.3 mmHg, p<0.001) in Trifecta. The frequency of AVAI<0.85 cm2/m2 (24% vs. 49%, p=0.036) and the frequency of m-PG≥20 mmHg (0% vs. 26%, p=0.006) were significantly less in Trifecta. There was significant relationship between GOAI and AVAI in both valves. Maximum BSA to obtain AVAI ≥0.85 cm2/m2 was estimated as 1.35 m2 in Magna and 1.50 m2 in Trifecta. In the 21 mm valve, AVAI was significantly larger (1.14±0.23 cm2/m2 vs. 0.92±0.22 cm2/m2, p<0.001) and m-PG was significantly lower (7.8±3.2 mmHg vs. 14.6±4.7 mmHg, p<0.001) in Trifecta. The frequency of AVAI<0.85 cm2/m2 was significantly less in Trifecta (11% vs. 42%, p=0.002) ; however, the frequency of m-PG≥20 mmHg did not differ significantly. There was a significant relationship between GOAI and AVAI in Magna and Trifecta. Maximum BSA to obtain AVAI ≥0.85 cm2/m2 was estimated as 1.49 m2 in Magna and 1.70 m2 in Trifecta. In the 23 and 25 mm valves, AVAI was significantly larger and m-PG was significantly lower in Trifecta. However neither the frequency of AVAI<0.85 cm2/m2 nor m-PG≥20 mmHg differed between the two valves. There was one early (27 months after surgery) SVD due to leaflet tear in Trifecta and two SVDs due to leaflet calcification more than 10 years after surgery in Magna. Conclusion : For Trifecta implantation, valve size selection seemed to be important and larger valves should be avoided with narrow ST junctions. Selection of 19 and 21 mm Magna valves should be limited for the patient with a BSA less than 1.35 and 1.49 m2 respectively. In Trifecta, early SVD might occur and careful follow-up is necessary.