Contractions In Children Research Articles

Evaluation of Premature Ventricular Contractions in Children with Structurally Normal Hearts: A Single-Center Study

Evaluation of Premature Ventricular Contractions in Children with Structurally Normal Hearts: A Single-Center Study

Premature ventricular contractions in children and young adults: natural history and clinical implications.

Premature ventricular contractions in children and young adults: natural history and clinical implications.

Efficacy of Propafenone for Treating Idiopathic Premature Ventricular Contractions in Children

Efficacy of Propafenone for Treating Idiopathic Premature Ventricular Contractions in Children

Efficacy of Radiofrequency Catheter Ablation versus Antiarrhythmic Drugs in Treating High Burden Premature Ventricular Contractions in Children with Structurally Normal Heart

Abstract Background Scarce literature on whether antiarrhythmic drugs (AADs) or radiofrequency catheter ablation (RFCA) is more efficacious when treating idiopathic high burden premature ventricular contractions (PVCs) in children with many questions remain unanswered in this age group. Objectives To compare the efficacy of RFCA versus AADs on high burden idiopathic PVCs in children. Methods A total of 60 eligible child ≤18 years with High burden PVCs (≥10% of total beats per day) that were treated by either AADs (group A) or RFCA (group B). Both Baseline and followup clinical symptoms were collected, Physical examination, repeat standard ECG, standard or 12-lead Holter recording, and echocardiography were performed. Results Among RFCA (n = 30) and AADs (n = 30) groups, treatment success was 80.0% and 20.0% respectively, while AADs medications cessation was 73.3% and 26.7% respectively, the differences were statistically significant. Conclusion RFCA appears to be more efficacious than AADs in PVC reduction and consequently AADs medications cessation postablation. Performing RFCA in children with classical mapping and navigation was a safe and highly effective therapeutic option. Abbreviations AADs: antiarrhythmic drugs; BBB: bundle branch block; CCB: calcium channel blocker; ECG: electrocardiogram; LVEDD: left ventricular end-diastolic dimension; LVEF: left ventricular ejection fraction; LVESD: left ventricular end-systolic dimension; LVOT: left ventricular outflow tract; NSVT: non sustained ventricular tachycardia; PVC: premature ventricular contraction; RFCA: radiofrequency catheter ablation; RV: right ventricular/ventricle; RVOT: right ventricular outflow tract

Isometric force complexity may not fully originate from the nervous system

In humans and animals, spatial and temporal information from the nervous system are translated into muscle force enabling movements of body segments. To gain deeper understanding of this translation of information into movements, we investigated the motor control dynamics of isometric contractions in children, adolescents, young adults and older adults. Twelve children, thirteen adolescents, fourteen young adults, and fifteen older adults completed two minutes of submaximal isometric plantar- and dorsiflexion. Simultaneously, sensorimotor cortex EEG, tibialis anterior and soleus EMG and plantar- and dorsiflexion force was recorded. Surrogate analysis suggested that all signals were from a deterministic origin. Multiscale entropy analysis revealed an inverted U-shape relationship between age and complexity for the force but not for the EEG and EMG signals. This suggests that temporal information in from the nervous system is modulated by the musculoskeletal system during the transmission into force. The entropic half-life analyses indicated that this modulation increases the time scale of the temporal dependency in the force signal compared to the neural signals. Together this indicates that the information embedded in produced force does not exclusively reflect the information embedded in the underlying neural signal.

Clinical utility of colonic low-amplitude propagating contractions in children with functional constipation.

Colonic high-amplitude propagating contractions (HAPC) are generally accepted as a marker of neuromuscular integrity. Little is known about low-amplitude propagating contractions (LAPCs); we evaluated their clinical utility in children. Retrospective review of children with functional constipation undergoing low-resolution colon manometry (CM) recording HAPCs and LAPCs (physiologic or bisacodyl-induced) in three groups: constipation, antegrade colonic enemas (ACE), and ileostomy. Outcome (therapy response) was compared to LAPCs in all patients and within groups. We evaluated LAPCs as potentially representing failed HAPCs. A total of 445 patients were included (median age 9.0 years, 54% female), 73 had LAPCs. We found no association between LAPCs and outcome (all patients, p=0.121), corroborated by logistic regression and excluding HAPCs. We found an association between physiologic LAPCs and outcome that disappears when excluding HAPCs or controlling with logistic regression. We found no association between outcome and bisacodyl-induced LAPCs or LAPC propagation. We found an association between LAPCs and outcome only in the constipation group that cancels with logistic regression and excluding HAPCs (p=0.026, 0.062, and 0.243, respectively). We found a higher proportion of patients with LAPCs amongst those with absent or abnormally propagated (absent or partially propagated) HAPCs compared to those with fully propagated HAPCs (p=0.001 and 0.004, respectively) suggesting LAPCs may represent failed HAPCs. LAPCs do not seem to have added clinical significance in pediatric functional constipation; CM interpretation could rely primarily on the presence of HAPCs. LAPCs may represent failed HAPCs. Larger studies are needed to further validate these findings.

Effectiveness of beta-blockers in the treatment of idiopathic premature ventricular contractions in children

Aim. To evaluate the effectiveness of beta-blockers (BB) in the treatment of idiopathic premature ventricular contractions (PVCs) in children.Material and methods. BBs were prescribed to 27 children with idiopathic PVCs. In 3 (11,1%) patients, side effects (hypotension, bronchial obstruction) was revealed at the beginning of therapy. A total of 24 children were included in the further study (15 boys (62,5%), 9 girls (37,5%). The mean age was 8,3±5,4 years. Data from anamnesis, electrocardiography (ECG), 24-hour ECG monitoring, and echocardiography were analyzed.Results. The 24-hour PVC rate was 33,2±17,7 thousand/day or 26,6±13,2%. In 14 (58,3%) children, we recorded paired PVCs, in 3 (12,5%) — multiform, in 10 (41,7%) — runs of non-sustained VT. There were complaints in 7 (29,2%) children. The follow-up period lasted 369,8±119,1 days. Propranolol was received by 17 (70,8%) patients, metoprolol — by 7 (29,2%). The therapy was effective in 11 (45,8%) patients, while ineffective in 13 (54,2%), among which 5 (20,8%) had an increase in the number of PVCs. The effectiveness of BBs was higher in children under the age of 1 year (p=0,043). Propranolol showed greater efficacy than metoprolol (p=0,047). Less efficiency was observed in female patients and those with pathological heart rate turbulence parameters (p=0,04).Conclusion. The effectiveness of BBs in children with idiopathic PVCs is 45,8%, higher in children aged <1 year and declines with age, decreasing in adolescents to 25%. The use of BBs is limited by non-cardiac side effects in 11,1% of children. Propranolol is more effective than metoprolol.

Efficacy of radiofrequency catheter ablation for premature ventricular contractions in children.

This study evaluated the efficacy and safety of transcatheter radiofrequency ablation (RFCA) in treating ventricular premature contractions (PVCs) in children, summarized the countermeasures during intraoperative ventricular fibrillation (VF), and improved the safety of ventricular premature treatment. A retrospective analysis was conducted on 75 children with PVCs who received RFCA in the Second Affiliated Hospital of Wenzhou Medical University from January 2010 to April 2019. Data including age, sex, body weight, ejection fraction, left ventricular end diastolic diameter, burden and number of PVCs/24h, origin of PVCs, and its complications were collected. Paired t test was used to compare changes in cardiac function before and after surgery. Among the 75 cases treated with RFCA, 68 were successfully ablated, giving a success rate of 90.67%. After ablation, the left ventricular ejection fraction (LVEF) of the children was 69.13 ± 3.81%, which was significantly higher than that before surgery (69.13 ± 3.81% vs. 66.21 ± 3.22%, P= 0.012). One of the patients experienced VF during the operation, with no other complications. The initial locus of origin was the anterior septum of the right ventricular outflow tract, but VF occurred during the ablation process. Mean follow-up time was 39 ± 33 months, with two recurrent cases (2.94%). Performing RFCA in children is safe and effective, with a low recurrence rate and few complications. VF is not an indication to cease surgery; the key to eliminating complications is repositioning the catheter and finding a more accurate origin point.

Premature Ventricular Contraction in Children

The article presents updated data on the problem of premature ventricular contractions in children based on the clinical guidelines of the Russian Society of Cardiology and the Union of Pediatricians of Russia for the diagnosis, treatment and management of pediatric patients with premature ventricular contraction. The issues of diagnosis and treatment based on the principles of evidence-based medicine as well as important aspects of prevention of exacerbations and follow-up have been clarified in detail. The criteria for assessing the quality of care for patients with premature ventricular contractions have been presented.CONFLICT OF INTEREST. Not declared.

Radiofrequency catheter ablation of premature ventricular contractions in children under CARTO3 system: a retrospective study from one single center

Objective: To evaluate the clinical effect and summarize the experience of radiofrequency catheter ablation (RFCA) for children suffered from premature ventricular contractions (PVCs). Methods: This retrospective study was conducted by descriptive analysis. A total of 108 cases with frequent PVCs from Shanghai Children's Medical Center were treated with RFCA under the guidance of CARTO3 system from January 2011 to December 2016. The immediate success rate of the procedure, the recurrence rate and the perioperative complications were summarized. The constituent ratio of different PVCs origins, the trend of overall procedure time and success rate in recent years were analyzed. Statistical analyses were performed using F test. Results: Immediate success of RFCA was achieved in 104 cases (96.3%, 104/108) and 4 cases (3.7%, 4/108) failed. The PVCs recurred during follow-up of over 6 months in 5 cases (4.8%, 5/104) . There were no severe complications related to the procedure. The sites of PVCs origin, in 52 cases originated from right ventricular outflow track (48.2%, 52/108) , 17 cases originated from left ventricular outflow track (15.7%, 17/108) and 26 cases originated from tricuspid annulus (24.1%, 26/108) . Among the three predilection sites of PVCs, the operation time was (141±46) min for right ventricular outflow track, (155±50) min for left ventricular outflow track, and (166±57) min for tricuspid annulus. However, the difference was not statistically significant (F=1.79, P=0.17) . X-ray exposure time was (14±8) minutes for right ventricular outflow track ablation, (32±14) minutes for left ventricular outflow track ablation and (16±8) minutes for tricuspid annulus ablation respectively. The exposure time for the ablation on left ventricle was significantly longer than the other two sites (F=5.12, P=0.018) . Conclusion: RFCA is safe and effective for PVCs in children with high success rate and low recurrence and complication rates.

Segmental colonic dilation is associated with premature termination of high-amplitude propagating contractions in children with intractable functional constipation.

Colonic dilation is common in children with intractable functional constipation (FC). Our aim was to describe the association between segmental colonic dilation and colonic dysmotility in children with FC. We performed a retrospective study on 30 children with intractable FC (according to the Rome III criteria) who had undergone colonic manometry and contrast enema within a 12-month time period. Colonic diameter was measured at 5cm intervals from the anal verge up to the splenic flexure. Moreover, the distance between the lateral margins of the pedicles of vertebra L2 was measured to provide a ratio (colonic diameter or length/distance between the lateral margins; "standardized colon size" [SCS]). All manometry recordings were visually inspected for the presence of high-amplitude propagating contractions (HAPCs); a parameter for colonic motility integrity. The intracolonic location of the manometry catheter sensors was assessed using an abdominal X-ray. Colonic segments with HAPCs had a significantly smaller median diameter than colonic segments without HAPCs (4.08cm vs 5.48cm, P<.001; SCS 1.14 vs 1.66, P=.001). Children with prematurely terminating HAPCs had significantly larger SCS ratios for colonic diameter than children with fully propagating HAPCs (P=.008). SCS ratios for the length of the rectosigmoid and the descending colon and the SCS ratio for sigmoid colon diameter were significantly larger in children with FC compared to a previously described normative population (P<.0001, P<.0001 and P=.0007 respectively). Segmental colonic dilation was associated with prematurely terminating HAPCs and may be a useful indicator of colonic dysmotility.

Geometry-Related Right Ventricular Systolic Function Assessed by Longitudinal and Radial Right Ventricular Contractions.

The aim of our study was to evaluate the geometry-related right ventricular (RV) systolic function under normal hemodynamics by assessing the longitudinal and the radial RV contractions in children. We examined 953 healthy children. We measured tricuspid annular plane systolic excursion (TAPSE), RV anterior wall displacement from the interventricular septum (RVWD), and RV to left ventricular diameter ratio (RV/LV ratio) using M-mode echocardiography. The z-values were calculated as geometrical parameters of the TAPSE (z-TAPSE), the RVWD (z-RVWD), and the RV/LV ratio (z-RV/LV). The RV stroke volume (RVSV) was measured using Doppler echocardiography and standardized using the z-value (z-RVSV). The z-TAPSE was no or weakly negatively correlated with both the z-RVWD (r=-0.18, P<0.0001) and the z-RV/LV (r=-0.12, P<0.0001). In contrast, the z-RV/LV correlated positively with the z-RVWD (r=0.61, P<0.0001). The z-RVSV correlated only with the z-TAPSE (r=0.30, P<0.0001). Although the radial RV motion increases with the progression of RV dilatation, the RVSV is not associated with radial RV motion. In contrast, the RVSV relates to the longitudinal RV motion independently of the radial RV motion under the normal physiological condition. We presume that the RV contraction patterns change related to the RV geometry under various hemodynamic conditions.

Insights into the Mechanisms of Neuromuscular Fatigue in Boys and Men.

The aim of the present study was to investigate the role of central and peripheral factors in neuromuscular fatigue induced by repeated maximal contractions in children and adults. Eleven boys (9.9 ± 1.2 yr) and 12 men (23.9 ± 3.5 yr) completed a fatigue protocol consisting in a repetition of 5-s maximal isometric voluntary contractions (MVC) of the knee extensors separated by 5-s passive recovery periods until the generated torque reached 60% of its initial value. Single magnetic stimulations were delivered to the femoral nerve every five MVC to follow the course of voluntary activation level and the amplitude of the potentiated twitch torque (Qtw(pot)) and vastus lateralis and rectus femoris concomitant M-waves (Mmax). Torque reached 60% of initial value after 49.5 ± 16.8 and 34.0 ± 19.6 repetitions in boys and men, respectively (P < 0.05). Furthermore, men showed significantly higher knee extensor MVC decline than boys between 50% and 90% of total repetitions (P < 0.05). Voluntary activation remained unchanged in men, whereas it decreased significantly in boys (P < 0.05). In contrast, whereas Qtw(pot) remained unchanged in boys, Qtw(pot) decreased progressively up to 60% of total repetitions in men (P < 0.001). Finally, Mmax remained unchanged for vastus lateralis and rectus femoris muscles in both groups. Children experienced no apparent peripheral fatigue and higher central fatigue than adults. The greater fatigue resistance in children could be related to a strategy of the CNS aimed at limiting the recruitment of motor units to prevent any extensive peripheral fatigue.

Transcutaneous Electrical Nerve Stimulation Increases Rectal Activity in Children.

Neurostimulation is increasingly used in treating bladder and bowel dysfunction, but its effect on rectal motility is obscure. The aim of the study was to evaluate the acute effect of transcutaneous electrical nerve stimulation (TENS) on rectal motility in children with overactive bladder (OAB). In this double-blind placebo-controlled study in 20 children with OAB (mean age 8.6 ± 1.8 years; 7 girls), 48-hour urodynamic monitoring including rectal manometry was performed. After 24-hours of baseline investigation without stimulation the children were randomised to either active TENS (n = 10) or placebo (n = 10). Surface electrodes were placed over the sacral bone. The exterior of active and placebo stimulators was identical. Starting in the morning, the children received either continuous TENS stimulation or placebo until bedtime. Rectal contractions were de&filig;ned as pressure runs exceeding 5 cm H2O and lasting ≥3 minutes. At baseline there was no significant difference in proportion of time with rectal contractions in the 2 groups (TENS group median 31% [range 12%-66%] vs placebo group median 31% [range 10%-66%]; P = 0.75); however, on the day of stimulation there was more time with rectal contractions in the group receiving TENS (median 51% [range 25%-78%]) compared with placebo (median 32% [range 4%-68%]; P = 0.02). Also, there was an increase in time with rectal contractions in the TENS group (P = 0.007) but not in the placebo group (P = 0.39). The night after the TENS was disabled, rectal activity in both groups returned to baseline level. TENS acutely increases time with rectal contractions in children undergoing urodynamic investigation. The effect disappears when the stimulator is turned off.

Premature ventricular contraction-induced cardiomyopathy in children.

Adults with high premature ventricular contraction burden can develop left ventricular dilation, dysfunction, and strain, consistent with a cardiomyopathy, which is reversible with radiofrequency ablation of the premature ventricular contractions. Evidence in children with similar ectopy burden is limited. We performed a single-centre retrospective review to examine the prevalence of premature ventricular contraction-induced cardiomyopathy, natural history of ventricular ectopy, and progression to ventricular tachycardia in children with frequent premature ventricular contractions. Children aged between 6 months and 18 years, with premature ventricular contractions comprising at least 20% of rhythm on 24-hour Holter monitor, were included in our study. Those with significant structural heart disease, ventricular tachycardia greater than 1% of rhythm at the time of premature ventricular contraction diagnosis, or family history of cardiomyopathy - except tachycardia-induced - were excluded. Cardiomyopathy was defined by echocardiographic assessment. A total of 36 children met the study criteria; seven patients (19.4%, 95% CI 6.2-32.6%) met the criteria for cardiomyopathy, mostly at initial presentation. Ectopy decreased to <10% of beats without intervention in 16.7% (95% CI 4.3-29.1%) of the patients. No patient progressed to having ventricular tachycardia as more than 1% of beats on follow-up Holter. Radiofrequency ablation was performed in three patients without cardiomyopathy. Our study demonstrates a higher prevalence of cardiomyopathy among children with high premature ventricular contraction burden than that previously shown. Ectopy tended to persist throughout follow-up. These trends suggest the need for a multi-centre study on frequent premature ventricular contractions in children. In the interim, regular follow-up with imaging to evaluate for cardiomyopathy is warranted.

Clinical characteristics and risk factors evaluation of premature atrial contractions in children

Objective To investigate clinical characteristics and risk factors for premature atrial contractions in children, which will provide effective reference for diagnosis and evaluation of premature atrial contractions. Methods Through history collection, physical examination, echocardiogram and electrocardiogram examination, 212 children were enrolled, who were diagnosed as premature atrial contractions without organic heart diseases.All clinical data of these children were analyzed.One hundred and sixty-nine children received dynamic electrocardiogram and treadmill exercise test. Results (1) Age distribution: 28-day to 1-year old children with the rate of 10.8%(23/212 cases), 1 to 3-year old with 9.4%(20/212 cases), 4 to 6-year old with 28.8%(61/212 cases), 7 to 10-year old with 21.2%(45/212 cases) and ≥11-year old with 29.8%(63/212 cases). There were 101 boys and 111 girls, with the ratio of 1.0:1.1.(2) There were 139 children(65.6%) without any symptoms, and 73 children(34.4%) with some symptoms, which mainly included sighing, oppression in chest, weakness, breath holding, palpitation, dizzy and pale complexion.The occurrence of sighing was higher to 83.6%(61/73 cases). (3) There were 85 children(61.2%) without symptoms who were found to have premature atrial contractions by routine physical examination, and there were 54 children(38.8%) who were found to have premature atrial contractions during visiting doctors because of other diseases such as infectious diseases.Usually, there were some incentive factors, such as infection(36/54 cases), exercise(15/54 cases), mental stress(11/54 cases) and fatigue(7/54 cases), among which infection was the most common one.(4) Between healthy children and those with premature atrial contractions, there was no statistic difference in basic heart rate, blood pressure, left ventricular end systolic dimension(LVDs), left ventricular end diastolic dimension(LVDd), ejection fraction, shortening fraction, and left atrial diameter(all P>0.05). (5)Number distribution of dynamic electrocardiogram per 24 hours: 20 000 with 13.7%(29/212 cases). (6) Exercise test of 169 children: during and after exercise, there were 135 children(79.8%) with decreased or disappeared premature contractions.There were 34 children(20.2%) with increased and pleomorphism premature contractions during exercise, and junctional escape rhythm, pairing premature contractions or ST-T changes.(7) Relation between frequency of premature contraction and treadmill exercise test: positive rates of exercise test were 20.2%(17/84 cases), 20.3%(13/64 cases) and 19.0%(4/21 cases) of children with 20 000/24 hours respectively.There was no statistic significance among groups(χ2=0.017, P=0.991). (8) Relation between apex time with exercise test: there was some relationship between premature contractions and sympathetic activity.Positive rate of daytime type(102 children) and nighttime type(67 children) were 28.4%(29/102 cases)and 7.5%(5/67 cases)respectively.There was statistic significance between the 2 types (χ2=0.001, P=0.001). Conclusions Children with premature atrial contractions have marked clinical characteristics in age distribution, and most children have no obvious symptoms.Infection is the most common incentive fact.It is necessary to finish dynamic electrocardiogram to investigate the distribution of premature contractions, and to finish exercise test to evaluate the risk degree of exercise for children with premature atrial contractions. Key words: Premature atrial contraction; Characteristics; Exercise test; Child

819 Effect of Colon Transection on Spontaneous High-Amplitude-Propagating Contractions in Children

819 Effect of Colon Transection on Spontaneous High-Amplitude-Propagating Contractions in Children

Internal anal sphincter relaxation associated with bisacodyl‐induced colonic high amplitude propagating contractions in children with constipation: a colo‐anal reflex?

Describe the association of internal anal sphincter (IAS) relaxation with colonic high- amplitude peristaltic contractions (HAPCs). Retrospective review of colon manometry tracings of children with constipation to determine the IAS relaxation characteristics associated with HAPC's (HAPC-IASR) events and compare them to the those seen during the performance of the anorectal manometry (ARMRAIR) events. A total of 70 HAPC- IASRs were observed in 15 patients, 65 after bisacodyl, two during fasting and three after a meal. In 64% of events, the IAS relaxation started when the HAPC reached left colon and in 36% as proximal as the hepatic flexure. High- amplitude peristaltic contraction propagation seems to be important in HAPC-IASR characteristics; those propagating distal to sigmoid colon demonstrated larger and longer IAS relaxation as well as lower residual pressure, but equivalent resting pressure compared with HAPC's ending proximal to sigmoid colon. Although IAS resting pressure was comparable for ARM-RAIRs and HAPC-IASRs, the duration and magnitude of anal relaxation was higher, and the anal residual pressure was lower in HAPC-IASRs. We demonstrated that IAS relaxation in constipated children is associated with HAPCs migrating in the proximal and distal colon; in most cases, starting when peristalsis is migrating through left colon and in an important proportion while migrating proximally. We also demonstrated that HAPC-IASRs are different from ARM-RAIRs suggesting a neurally mediated reflex. Finally, the IAS relaxation characteristics are highly dependent on the degree of propagation of HAPCs, which could have important implications in the understanding of defecation disorders.

Distention of the colon is associated with initiation of propagated contractions in children

The presence of high-amplitude propagating contractions (HAPCs) has been identified as a marker of colonic neuromuscular integrity. The physiologic mechanisms of HAPCs initiation have yet to be determined. Distention secondary to colonic filling has been hypothesized as physiologic initiator. The aim of this study was to study the effect of intraluminal balloon distention in the colon of children with defecatory disorders. Colonic manometry was performed with a polyethylene balloon situated at the proximal end of the catheter, which was placed in the most proximal colonic segment reached during colonoscopy. A stepwise pressure controlled distention of the balloon was performed using barostat computer (10-50 mmHg). Propagated contractions were defined as those that migrated over at least three recording sites. They were divided into HAPCs, amplitude >60 mmHg and low-amplitude propagating contractions (LAPCs), amplitude <60 mmHg. Children with spontaneous HAPCs or HAPCs after bisacodyl provocation were considered to have normal motility. Twenty children completed the study. Among the 14 children with normal colonic motility, balloon distention elicited HAPCs in four and LAPCs in 10 children. No HAPC were elicited in six children with abnormal motility and LAPCs were seen in four of them. The balloon-induced propagated contractions had similar characteristics as those occurring spontaneously and after bisacodyl provocation but the pressure needed to elicit them and their amplitude was inconsistent. These findings suggest that intraluminal distention can trigger propagated contractions in children. This mechanism of action for induction of propagated contractions is not as consistent as the motor response found in response to bisacodyl administration.

Force variability during isometric biceps contraction in children with secondary dystonia due to cerebral palsy

Children with secondary dystonia due to cerebral palsy (CP) often exhibit excess variability in their movements. To investigate the relationship between excess variability and single-joint control in these children, we compared their force variations during single-joint isometric tasks to age-matched controls. Subjects performed isometric biceps contractions at six target force levels scaled to their maximum voluntary contraction. Similar studies in healthy adults have shown that movement variability exhibits characteristics of signal-dependent noise (SDN). We look for the first time at whether variability in single-joint force contractions in healthy children and children with CP exhibit similar characteristics of SDN. Results showed that compared to controls, patients exhibited increased variability (standard deviation about the mean), increased force error bias (difference between the mean and target), and increased dependence of force error bias on target force level. Signal-dependence of the noise was significant only in healthy subjects due to the higher overall variability in the patients. A control experiment using filtered visual feedback confirmed that overcorrection for perceived error was not the cause of the observed variability. These results contribute to a better understanding of movement variability in childhood dystonia and have potential use in therapeutic interventions designed to increase force production reliability.