Acute and Cumulative Effects With Whole-Body Vibration Exercises Using 2 Biomechanical Conditions on the Flexibility and Rating of Perceived Exertion in Individuals With Metabolic Syndrome: A Randomized Clinical Trial Pilot Study.

This study evaluated the effects of 6 weeks of whole-body vibration (WBV) exercise on flexibility and the rating of perceived exertion (RPE) in metabolic syndrome (MetS) individuals using 2 biomechanical conditions (fixed frequency [FF] and variable frequency [VF]). Nineteen MetS individuals were randomly allocated in FF-WBV (n = 9, 7 women and 2 men) and VF-WBV (n = 10, 8 women and 2 men) groups. Anterior trunk flexion (ATF) and RPE were determined before and after each session. The acute cumulative exposure effects were analyzed. The FF-WBV group was exposed to 5 Hz on a side alternating vibrating platform (SAVP), exposed to 10 and 50 seconds with the SAVP turned off. The VF-WBV group individuals were intermittently exposed (1 minute WBV exercise/1 minute rest) to 5 to 16 Hz, increased by 1 Hz per session and the peak-to-peak displacement (PPD) were 2.5, 5.0, and 7.5 mm. Regarding to ATF, significant improvements (P < .05) were observed in the in the acute (VF group) and cumulative intervention (FF and VF-WBV groups). The RPE significantly (P < .05) improved only in VF-WBV (cumulative intervention). In conclusion, WBV exercise improved the flexibility and decreased the RPE in MetS individuals. These findings suggest that WBV exercise can be incorporated into physical activities for MetS individuals.

Does Muscular Force of the Upper Body Increase Following Acute, Direct Vibration?

The aim of the current study was to examine the acute effect of direct vibration has on bicep curl force-generating capacity. 11 healthy team and individual sport-trained males performed right and left DB bicep curl at 50% of 1 RM where peak force (PF), mean force (MF), rate of force development (RFD) and electromyography (EMG) were assessed during the concentric phase before and immediately after direct vibration. Using new vibration technology utilizing a pulsing frequency (0-170 Hz) each arm was randomly assigned to receive either 10 min of direct vibration or control (no vibration). Following direct vibration PF increased 6.6±4.5 N (difference pre-post±90 CL; p>0.05) compared to control FP (-1.2±65 N; p>0.05) however, this was not significant. Furthermore, there were no other significant changes (p>0.05) in MP, RFD and EMG between vibration and control arms. This is in agreement with other research that has reported that acute strength changes from vibration elicits negligible changes, however it appears that there are no detrimental effects of using this new vibration device.

The Acute Effect of Direct Vibration on Muscular Power Performance in Master Athletes.

This study examined the acute effect of direct vibration on biceps brachii muscular power in master athletes. 10 healthy male national representative master field-hockey players were randomly assigned to receive 10 min of pulsing sinusoidal vibration or no vibration (control) to the right and left biceps brachii. Pre- and post-testing included lifting 2 repetitions of standing dumbbell (DB) biceps curl at 50% 1 RM (repetition maximum). Mechanical peak power (PP), mean concentric power (MCP) and normalised electromyography (EMG) was assessed during the concentric phase of the biceps curl. Following vibration PP increased 44.3±23.6 W (difference pre-post; p=0.013) compared to control (5.9±9.5 W; p=0.334). Similarly, MCP increased 12.0±4.5 W (p=0.002) compared to control (1.5±0.8 W; p=0.397). However, there was no significant difference in normalised EMG between vibration and control (p>0.05). The increase in PP and MCP did not coincide with an increase in EMG and suggests that other mechanisms may be contributing to changes in muscle performance. Given its ease of use and portability the vibratory device may be considered as an alternative warm-up modality immediately prior to explosive activities.

Does Vibration Warm-up Enhance Kinetic and Temporal Sprint Parameters?

The aim of this study was to investigate the efficacy of vibration warm-up to enhance sprint performance. 12 males involved in representative team sports performed 4 warm-up conditions in a randomised order performed at least 24 h apart; VbX warm-up (VbX-WU); Neural activation warm-up (Neu-WU); Dynamic warm-up (Dyn-WU) and Control (No VbX). Participants completed 5 m sprint at 30 s, 2:30 min and 5 min post warm-up where sprint time, kinetics, and temporal components were recorded. There was no significant (p>0.05) main effect or interaction effect between the split sprint times of 1 m, 2.5 m, and 5 m. There was a condition effect where vertical mean force was significantly higher (p<0.05) in Dyn-WU and Control compared to Neu-WU. No other significant (p>0.05) main and interaction effects in sprint kinetic and temporal parameters existed. Overall, all 4 warm-up conditions produced comparable results for sprint performance, and there was no detrimental effect on short-duration sprint performance using VbX-WU. Therefore, VbX could be useful for adding variety to the training warm-up or be included into the main warm-up routine as a supplementary modality.

Effect of paddle grip on segmental fluid distribution and injuries occurrence in elite slalom paddlers.

AIM: The aim of this current study was to assess the segmental fluid distribution, grip strength and injury occurrence in elite slalom kayakers and canoeists. METHODS: Ninety three world-cup competitors (72 males; 21 females) took part in the study. Impedance analysis assessed segmental fluid asymmetry and a questionnaire evaluated injury occurrence during the three previous years. The effect of paddle grip (loose/fixed hand in kayakers, lower/upper hand in canoeists), morphological dominance (dominant/non-dominant) and discipline (canoe/kayak) was evaluated by repeated measures ANOVA. RESULTS: The findings indicated a significant effect of paddle grip in male canoeists on morphological asymmetry in the upper limbs (arm of lower paddle hand, mean fluid distribution 3.17, s=0.47 litres; arm of upper paddle hand mean fluid distribution 3.08, s=0.45 litres; P<0.001, ωp2=0.32). Significant morphological asymmetry was found also in kayakers but the effect of paddle grip was not substantial. Grip strength was not related to paddle grip. Paddlers with arm morphological asymmetry reported upper limb injury occurrence in 60% of cases, which was 3 times more than in paddlers without arm morphological asymmetry. CONCLUSION: As upper-limb asymmetry was directly associated with paddle grip in male canoeists, canoe paddling may lead to higher bilateral morphological asymmetry and therefore, injury occurrence.

Does acute side-alternating vibration exercise enhance ballistic upper-body power?

The aim of this study was to investigate the effects of acute vibration exercise, at 2 different frequencies, on upper body power output. Muscle activity (EMG) and upper-body peak power was measured in 12 healthy males during ballistic bench press throws at 30% of 1-repetition maximum on a Smith machine. Measures were made prior to, 30 s and 5 min after one of 3 conditions performed for 30 s in a press-up position: side-alternating vibration at 20 Hz, 26 Hz and no vibration. EMG was recorded in the anterior deltoid, triceps brachii and pectoralis major during ballistic bench press throws as well as during application of each condition. While peak power output was higher at 5 min post condition across all conditions, compared to baseline measures (P<0.05), only 20 Hz vibration resulted in a significant increase in peak power output (P<0.05) compared to no vibration. EMG was greater during both vibration conditions, compared to no vibration (P<0.001). However, this difference was not evident during bench press throws when no difference was seen in muscle activity between conditions. These findings suggest that 20 Hz vibration has an ergogenic effect on upper-body power that may be due to peripheral, rather than central, mediated mechanisms.

Acute unilateral leg vibration exercise improves contralateral neuromuscular performance.

OBJECTIVES: To examine the post-exercise cross-transfer effects of acute whole body vibration (WBV). METHODS: Seventeen healthy male volunteers (20.8 ± 1.2 y) performed three unilateral vibration conditions in a randomized order: 1) WBV-50 Hz [high amplitude]; 2) WBV-30 Hz [low amplitude]; and 3) a control no WBV condition (Sham) applied to the dominant leg. Each condition involved maximal voluntary isometric contractions (MVC) followed by three leg press explosive repetitions (40% MVC) with non-dominant and dominant legs; which were conducted prior to and post vibration (immediately; 2 min and 5 min). Surface electromygraphy (sEMG) of the vastus lateralis (VL) and medial gastrocnemius (MG) were measured throughout each condition. RESULTS: A condition x leg x time interaction effect was detected (p=0.001) where 50 Hz-High in the stimulated leg enhanced mean velocity at post-2 min compared to 30 Hz-Low and Sham, remaining elevated at post-5 min. Similarly, 50 Hz-High in the non-stimulated leg increased mean velocity at post-immediately and post-2 min compared to 30 Hz-Low and Sham. There were no changes in sEMG of VL and GM in the stimulated and non-stimulated post-conditions. CONCLUSION: WBV (50 Hz) can augment cross-transfer in neuromuscular performance. WBV could provide an alternate method of unilateral training to promote cross education explosive strength.

Does intermittent pneumatic leg compression enhance muscle recovery after strenuous eccentric exercise?

Intermittent pneumatic compression (IPC) has gained rapid popularity as a post-exercise recovery modality. Despite its widespread use and anecdotal claims for enhancing muscle recovery there is no scientific evidence to support its use. 10 healthy, active males performed a strenuous bout of eccentric exercise (3 sets of 100 repetitions) followed by IPC treatment or control performed immediately after exercise and at 24 and 48 h post-exercise. Muscular performance measurements were taken prior to exercise and 24, 48 and 72 h post-exercise and included single-leg vertical jump (VJ) and peak and average isometric [knee angle 75º] (ISO), concentric (CON) and eccentric (ECC) contractions performed at slow (30° · s⁻¹) and fast (180° · s⁻¹) velocities. Plasma creatine kinase (CK) samples were taken at pre- and post-exercise 24, 48 and 72 h. Strenuous eccentric exercise resulted in a significant decrease in peak ISO, peak and average CON (30° · s⁻¹) at 24 h compared to pre-exercise for both IPC and control, however VJ performance remained unchanged. There were no significant differences between conditions (IPC and control) or condition-time interactions for any of the contraction types (ISO, CON, ECC) or velocities (CON, ECC 30° · s⁻¹ and 180° · s⁻¹). However, CK was significantly elevated at 24 h compared to pre-exercise in both conditions (IPC and control). IPC did not attenuate muscle force loss following a bout of strenuous eccentric exercise in comparison to a control. While IPC has been used in the clinical setting to treat pathologic conditions, the parameters used to treat muscle damage following strenuous exercise in healthy participants are likely to be very different than those used to treat pathologic conditions.

Is vibration exercise a useful addition to a weight management program?

Vibration exercise (VbX) has received a lot of attention as an exercise modality, which evokes muscular work and elevates metabolic rate that could be a potential method for weight reduction. Popular press has purported that VbX is quick and convenient, and 10 min of VbX is equivalent to 1 h of traditional exercise, where it has been marketed as the new weight-loss and body toning workout. However, research studies have shown that muscle activation occurs but the energy demand in response to VbX is quite low, where exhaustive VbX reported a metabolic demand of 23 mL/kg/min compared with 44 mL/kg/min from an exhaustive cycle test. Different vibration frequencies with varying amplitudes and loads have been tested, but only small increases in metabolic rate have been reported. Based on these findings, it has been indirectly calculated that a VbX session of 26 Hz for three continuous minutes would only incur a loss of ≈ 10.7 g fat/h. Following a 24-week program of VbX, no observed differences were found in body composition, and following 12 months of VbX, the time to reach peak V ˙O2 was significantly higher in conventional exercise compared with VbX. However, one study has reported that percentage body fat decreased by 3.2% after 8 months after VbX in comparison with resistance and control groups that performed no aerobic conditioning. The evidence to date suggests that VbX can increase whole and local oxygen uptake; however, with additional load, high vibration frequency, and/or amplitude, it cannot match the demands of conventional aerobic exercise. Therefore, caution is required when VbX programs are solely used for the purpose of reducing body fat without considering dietary and aerobic conditioning guidelines.

Vibration exercise: the potential benefits.

The aim of this review was to examine the physiological effects of vibration exercise (VbX), including the cardiovascular indices and to elucidate its potential use for those with compromised health. VbX has long been acknowledged as a potential modality in sport, exercise, and health sectors. Muscle force and power have been shown to increase after VbX for athletes, the aged and those with diseases, where neural factors are thought to be the main contributor. Further, similarities to the tonic vibration reflex have been used to propose that the muscle spindle plays a role in activating the muscle which could benefit those with compromised health. There is strong evidence that acute VbX can enhance upper and lower-body muscle power, and there is some indication that longer-term VbX can augment muscle power of upper and lower body extremities, although this is less convincing. It is not conclusive whether VbX increases force attributes. This has been fraught by the type and parameters used for various muscle contractions, and the different sample populations that have varied in chronological age, experience and training status. VbX provides an insufficient stimulus to enhance cardiovascular indices, where VbX cannot increase heart rate to the same extent as conventional aerobic exercise. But when conventional aerobic exercise is not possible, for example, in aged, cardiovascular compromised persons, VbX could be implemented at an early stage because it could provide a safe induction of a slight elevation of cardiovascular function indices while providing neural and myogenic benefits. In conclusion, VbX is a safe modality to increase physiological responses of reflex and muscle activity, and muscle function, for athletes, the aged and compromised health. However, further research should focus on the optimum dose relationship of frequency, amplitude and duration for the various populations.

Comparing muscle temperature during static and dynamic squatting with and without whole-body vibration.

The aim of this study was to investigate the influence of shallow dynamic squatting (DS) versus static squatting (SS) with or without concurrent side-to-side alternating whole-body vibration (WBV) on vastus lateralis temperature and cardiovascular stress as indicated by heart rate (HR). Ten participants (five men, five women) participated in four interventions [DS with WBV (DS+), DS without WBV (DS-), SS with WBV (SS+), SS without WBV (SS-)] 48 h apart, in a randomized order. The interventions were preceded by a approximately 20-min rest period, consisted of 10 mins with or without WBV (26 or 0 Hz) with SS (40 degrees of knee flexion) or DS (55 degrees of knee flexion, at a cadence of 50 bpm) where SS+ and DS- were metabolically matched. Muscle (T(m)), core (T(c)), skin temperature (T(sk)), HR and VO(2) were recorded during each intervention. For T(m), there was a time (P<0.01) and WBV (P<0.01) effect but no squat effect was evident, and there was time xWBV interaction effect (P<0.01). In all four interventions, the work load was too low to cause cardiovascular stress. Instead normal, moderate physiological effects of exercise on autonomic control were observed as indicated by HR; there were no significant increases in T(sk) or T(c). There appears to be no benefit in performing an unloaded, shallow DS+ at a tempo of 50 bpm as T(m,) HR, VO(2) are likely to be increased by the same amount and rate without WBV. However, combining SS with WBV could be advantageous to rapidly increasing soft tissue temperature prior to performing rehabilitation exercises when dynamic exercise cannot be performed.

The effects of acute whole body vibration as a recovery modality following high-intensity interval training in well-trained, middle-aged runners.

The main purpose of the present study was to examine the effects of acute whole body vibration (WBV) on recovery following a 3 km time trial (3 km TT) and high-intensity interval training (HIIT) (8 x 400 m). Post-HIIT measures included 3 km time-trial performance, exercise metabolism and markers of muscle damage (creatine kinase, CK) and inflammation (c-reactive protein, CRP). A second purpose was to determine the effects of a 3 km TT and HIIT on performance and metabolism the following day. Nine well-trained, middle-aged, male runners [(mean +/- SD) age 45 +/- 6 years, body mass 75 +/- 7 kg, VO2peak 58 +/- 5 ml kg(-1 )min(-1)] performed a constant pace run at 60 and 80% velocity at VO2peak (v VO2peak) followed by a 3-km TT and a 8 x 400-m HIIT session on two occasions. Following one occasion, the athletes performed 2 x 15 min of low frequency (12 Hz) WBV, whilst the other occasion was a non-WBV control. Twenty-four hours after each HIIT session (day 2) participants performed the constant pace run (60 and 80% v VO2peak) and 3 km TT again. There was a significant decrease in 3 km TT performance (~10 s) 24 h after the HIIT session (P < 0.05); however, there were no differences between conditions (control vs. vibration, P > 0.05). Creatine kinase was significantly elevated on day 2, though there were no differences between conditions (P > 0.05). VO2peak and blood lactate were lower on day 2 (P < 0.05), again with no differences between conditions (P > 0.05). These results show no benefit of WBV on running performance recovery following a HIIT session. However, we have shown that there may be acute alterations in metabolism 24 h following such a running session in well-trained, middle-aged runners.

The rate of muscle temperature increase during acute whole-body vibration exercise.

This study compared the rate of muscle temperature (Tm) increase during acute whole-body vibration (WBV), to that of stationary cycling and passive warm-up. Additionally we wanted to determine if the purported increase in counter-movement jump and peak power cycling from acute WBV could be explained by changes in muscle temperature. Eight active participants volunteered for the study, which involved a rest period of 30 min to collect baseline measures of muscle, core, skin temperature, heart rate (HR), and thermal leg sensation (TLS), which was followed by three vertical jumps and 5 s maximal cycle performance test. A second rest period of 40 min was enforced followed by the intervention and performance tests. The change in Tm elicited during cycling was matched in the hot bath and WBV interventions. Therefore cycling was performed first, proceeded by, in a random order of hot bath and acute WBV. The rate of Tm was significantly greater (P < 0.001) during acute WBV (0.30 degree C min(-1)) compared to cycle (0.15 degree C min(-1)) and hot bath (0.09 degree C min(-1)) however there was no difference between the cycle and hot bath, and the metabolic rate was the same in cycling and WBV (19 mL kg(-1) min(-1)). All three interventions showed a significant (P < 0.001) increase in countermovement jump peak power and height. For the 5 s maximal cycle test (MIC) there were no significant differences in peak power between the three interventions. In conclusion, acute WBV elevates Tm more quickly than traditional forms of cycling and passive warm-up. Given that all three warm-up methods yielded the same increase in peak power output, we propose that the main effect is caused by the increase in Tm.

The acute effect of vibration exercise on concentric muscular characteristics.

This study was designed to compare the acute effect of vibration exercise with a concentric-only activity (arm cranking) on concentric-only muscle action using an upper body isoinertial exercise. Twelve healthy, physically active men, 30.0y+/-6.1 (mean+/-S.D.); height 1.81m+/-0.06; and weight 83.4kg+/-9.7, performed four maximal prone bench pull (PBP) efforts before and after a 5-min period of three different interventions: (1) acute vibration exercise (VBX); (2) arm cranking (AC); and (3) control (no exercise) (NVBX). Electromyography (EMG) activity was assessed from the middle trapezius muscle during PBP. Acute VBX was induced with an electric-powered dumbbell (DB) (frequency 26Hz, amplitude 3mm), with 30-s exposures at five different shoulder positions. NVXB was performed with the participants holding the DB with the machine turned off, and AC was performed at 25W. There was a significant (intervention x pre-post) interaction such that acute VBX and AC enhanced peak power by 4.8% (p<0.001) and 3.0% (p<0.001), respectively, compared to NVBX (-2.7%). However, there was no effect of any treatments on EMG activity compared to the control. In conclusion, acute VBX provides an acute ergogenic effect which potentiates concentric-only muscle performance, though not to a significantly greater extent than concentric (arm cranking) exercise.

Acute whole body vibration training increases vertical jump and flexibility performance in elite female field hockey players.

OBJECTIVE: To quantify the acute effect of whole body vibration (WBV) training on arm countermovement vertical jump (ACMVJ), grip strength, and flexibility performance. METHODS: Eighteen female elite field hockey players each completed three interventions of WBV, control, and cycling in a balanced random manner. WBV was performed on a Galileo machine (26 Hz) with six different exercises being performed. For the control, the same six exercises were performed at 0 Hz, whilst cycling was performed at 50 W. Each intervention was 5 min in duration with ACMVJ, grip strength, and flexibility measurements being conducted pre and post intervention. RESULTS: There was a positive interaction effect (intervention x pre-post) of enhanced ACMVJ (p<0.001) and flexibility (p<0.05) parameters following WBV; however no changes were observed after the control and cycling interventions. There was no interaction effect for grip strength following the three interventions. CONCLUSIONS: Acute WBV causes neural potentiation of the stretch reflex loop as shown by the improved ACMVJ and flexibility performance. Additionally, muscle groups less proportionally exposed to vibration do not exhibit physiological changes that potentiate muscular performance.

The assessment of an intermittent high intensity running test.

AIM: In multiple sprint sports the ability to perform repeated short duration bouts of maximal intensity exercise appears to be sport specific than the ability to perform prolonged continuous exercise or produce a single bout of exercise. However, previous studies have not verified a field test method with an appropriate intermittent anaerobic exercise pattern. The purpose of this study was to establish the reliability and validity of the Intermittent Anaerobic Running Test (IAnRT) primarily developed for soccer players. METHODS: Twenty-nine trained male adolescent soccer players performed two separate 20 m sprints and the IAnRT on an indoor running track in each of two testing sessions separated by one recovery day. The IAnRT consisted of 10 20-m sprints with 20-s recovery periods between the sprints. RESULTS: The mean running speed (Vm) and the speed at the beginning and the end of the IAnRT (V1+2, V9+10) confirmed good reliability. The relative mean speed index was the preferred indicator for assessing the ability to maintain short duration running performance during the intermittent exercise mode. Using confirmatory factor analysis the running performance of IAnRT was best explained by one general factor and one subfactor which consequently joined the general one from the 6th sprint (P=0.03, Bentler's d=0.99, RMSR=0.03). CONCLUSION: The IAnRT provided reliable and valid performance indices, which reflect the maximal anaerobic running power and capacity for repeated running sprints.

Do changing patterns of heat and humidity influence thermoregulation and endurance performance?

The purpose of this project was to determine whether changing patterns of temperature and humidity, as expected in the morning versus afternoon, had a differential effect on thermoregulation and endurance performance. Eight male distance runners each participated in two heat pattern tests consisting of two hours treadmill running at 70%-maximum oxygen consumption. The mean heat load for each test was identical (22.2 degrees C wet bulb temperature) but either dry bulb temperature increased (24 to 27.5 degrees C) or decreased (27.5 to 24 degrees C) over the course of the two hour heat stress test. Whole body sweat rate was 10.7% higher (p<0.05) and there was greater plasma volume loss (2.7 versus 1.6%, p<0.05) in the cooling versus warming pattern test. Mean skin and body temperature changed in a significantly different (p<0.05) manner between the two patterns and closely followed ambient dry bulb temperature change. The thermoregulatory variables of heart rate and rectal temperature were not affected and performance did not differ between pattern tests. Ratings of perceived exertion (RPE) and oxygen consumption were also not significantly different between cooling and warming test. In summary, although some minor differences were noted, thermal homeostasis was maintained equally well during either warming or cooling for wet bulb temperatures between 24 and 27 degrees C. The mean heat load is therefore more important than changing patterns of temperature and humidity in determining an individual's physiological response to exercise in a warm environment.

A gastroesophageal electrode for atrial and ventricular pacing.

Temporary transvenous cardiac pacing requires technical expertise and access to fluoroscopy. We have developed a gastroesophageal electrode capable of atrial and ventricular pacing. The flexible polythene gastroesophageal electrode is passed into the stomach under light sedation. Five ring electrodes, now positioned in the lower esophagus, are used for atrial pacing. A point source (cathode) on the distal tip of the electrode, now positioned in the gastric fundus, is used for ventricular pacing. Two configurations of atrial and ventricular pacing were compared: unipolar and bipolar. During unipolar ventricular pacing the indifferent electrode (anode) was a high impedance chest pad. For bipolar ventricular pacing the indifferent electrode was a ring electrodes placed 2 cm proximal to the tip. Unipolar atrial pacing was performed with 1 of 5 proximal ring electrodes acting as cathode ("cathodic") or as anode ("anodic") in conjunction with a chest pad. Bipolar atrial pacing was performed using combinations of 2 of 5 ring electrodes. Atrial capture was obtained in all 55 subjects attempted. When all electrode combinations were compared, atrial capture was significantly more frequent using the bipolar approach (153/210 bipolar, 65/210 unipolar; t = 7.37, P < 0.001). For unipolar atrial pacing, cathodic stimulation (from esophagus) was more successful than anodic stimulation (cathodic 62/105, anodic 20/105; t = 5.81, P < 0.001). In 43 subjects attempted unipolar ventricular pacing resulted in a higher frequency of capture than the bipolar approach (unipolar 41/43 (95.3%), bipolar 19/43 (44.2%); P < 0.001). In conclusion, atrial pacing was optimal using pairs of ring electrodes ("bipolar") while ventricular pacing was optimal using the distal electrode tip (cathode) in conjunction with a chest pad electrode ("unipolar"). This gastroesophageal electrode may be useful in the emergency management of acute bradyarrhythmias and for elective electrophysiological studies.

Ventricular pacing with a novel gastroesophageal electrode: a comparison with external pacing.

Temporary endocardial pacing is a technically demanding invasive procedure requiring sterile precautions and access to fluoroscopy. External (transcutaneous) pacing requires high current for capture and is poorly tolerated in the conscious patient. An esothoracic pacing system has been developed capable of reliable ventricular capture. The flexible gastroesophageal electrode is passed into the stomach. The distal 6 cm is angled to 90 degrees with an internal pulley system, positioning the tip of the gastroesophageal electrode in the fundus of the stomach. Ventricular pacing is performed with a spherical electrode (cathode) mounted on the gastroesophageal electrode tip in conjunction with a chest pad (anode) positioned medial to the cardiac apex. Of 91 subjects in which esothoracic pacing was attempted, 86 (94.5%) demonstrated successful ventricular capture at the maximum pulse duration used (40 msec). Threshold current for ventricular capture ranged from 22.5 +/- 8.1 mA at a pulse duration of 40 msec to 29.9 +/- 8.6 mA at a pulse duration of 10 msec. Esothoracic pacing was compared with external pacing in a subgroup (n = 30) of patients. Ventricular capture with the gastroesophageal electrode was more common when compared with the external approach (27 [90%] of 30 vs 13 [43.3%] of 30, p < 0.001). In those subjects in whom ventricular capture was obtained with both methods, threshold current for capture was significantly lower with the esothoracic approach. This gastroesophageal electrode may be useful in the emergency management of acute bradyarrhythmias.

An esophageal and gastric approach to ventricular pacing.

Using a unipolar esothoracic pacing system (where current passes from a point source positioned in the distal esophagus to a chest wall pad) and pulse duration of 50 msec, satisfactory 1:1 ventricular capture was obtained in 57 (86%) of 66 patients, with a mean threshold current of 27.7 mA at an optimal depth of 40.3 cm from the lower lip. When the unipolar esothoracic and bipolar transesophageal ventricular pacing systems were compared, the bipolar system was associated with a lower success rate and higher threshold current. When unipolar esothoracic pacing and gastrothoracic pacing (where current passes from a point source positioned in the stomach to a chest wall pad) were compared in 23 patients with bradyarrhythmia, ventricular capture was achieved using gastrothoracic pacing in 22 patients (96%) and esothoracic pacing in 21 (91%): gastrothoracic pacing required less current (16.0 mA +/- SD 7.2 vs 25.8 mA +/- SD 8.6). Optimal ventricular capture occurred using a unipolar gastrothoracic pacing electrode inserted to an average depth of 44.3 cm together with a high impedance chest pad (250 omega) placed in the fourth interspace at the left sternal edge, with 50-msec current pulses and a mean threshold of 16.0 mA. Thus, using a gastroesophageal electrode system, ventricular pacing can be achieved successfully, and the availability of such a system could play a major role in resuscitation of patients from severe bradyarrhythmias.