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Heart Rate Changes (heart + rate_change)
Selected AbstractsHeart Rate Changes and ECG Abnormalities During Epileptic Seizures: Prevalence and Definition of an Objective Clinical SignEPILEPSIA, Issue 8 2002Maeike Zijlmans Summary: ,Purpose: To determine the prevalence of heart rate changes and ECG abnormalities during epileptic seizures and to determine the timing of heart rate changes compared to the first electrographic and clinical signs. To assess the risk factors for the occurrence of ECG abnormalities. Methods: We analyzed retrospectively 281 seizures in 81 patients with intractable epilepsy who had prolonged video-EEG and two-channel ECG. The nature and timing of heart rate changes compared to the electrographic and clinical seizure onset was determined. The ictal period (including one minute preictally and three minutes postictally) was analyzed for cardiac arrhythmias, conduction and repolarization abnormalities. Risk factors for cardiac abnormalities were investigated using parametric and non-parametric statistics. Results: There was an increase in heart rate of at least 10 beats/minute in 73% of seizures (93% of patients) and this occurred most often around seizure onset. In 23% of seizures (49% of patients) the rate increase preceded both the electrographic and the clinical onset. ECG abnormalities were found in 26% of seizures (44% of patients). One patient had an asystole for 30 seconds. Long seizure duration increased the occurrence of ECG abnormalities. No other risk factor was found. Conclusions: Heart rate changes occur frequently and occur around the time or even before the earliest electrographic or clinical change. The change can clarify the timing of seizure onset and the specific rate pattern may be useful for seizure diagnosis and for automatic seizure detection. ECG abnormalities occur often and repeatedly in several seizures of the same patient. [source] QT Interval Variability and Adaptation to Heart Rate Changes in Patients with Long QT SyndromePACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1 2009JAN N, MEC M.D. Background: Increased QT variability (QTV) has been reported in conditions associated with ventricular arrhythmias. Data on QTV in patients with congenital long QT syndrome (LQTS) are limited. Methods: Ambulatory electrocardiogram recordings were analyzed in 23 genotyped LQTS patients and in 16 healthy subjects (C). Short-term QTV was compared between C and LQTS. The dependence of QT duration on heart rate was evaluated with three different linear models, based either on the RR interval preceding the QT interval (RR0), the RR interval preceding RR0 (RR -1), or the average RR interval in the 60-second period before QT interval (mRR). Results: Short-term QTV was significantly higher in LQTS than in C subjects (14.94 ± 9.33 vs 7.31 ± 1.29 ms; P < 0.001). It was also higher in the non-LQT1 than in LQT1 patients (23.00 ± 9.05 vs 8.74 ± 1.56 ms; P < 0.001) and correlated positively with QTc in LQTS (r = 0.623, P < 0.002). In the C subjects, the linear model based on mRR predicted QT duration significantly better than models based on RR0 and RR -1. It also provided better fit than any nonlinear model based on RR0. This was also true for LQT1 patients. For non-LQT1 patients, all models provided poor prediction of QT interval. Conclusions: QTV is elevated in LQTS patients and is correlated with QTc in LQTS. Significant differences with respect to QTV exist among different genotypes. QT interval duration is strongly affected by noninstantaneous heart rate in both C and LQT1 subjects. These findings could improve formulas for QT interval correction and provide insight on cellular mechanisms of QT adaptation. [source] Heart Rate Changes and ECG Abnormalities During Epileptic Seizures: Prevalence and Definition of an Objective Clinical SignEPILEPSIA, Issue 8 2002Maeike Zijlmans Summary: ,Purpose: To determine the prevalence of heart rate changes and ECG abnormalities during epileptic seizures and to determine the timing of heart rate changes compared to the first electrographic and clinical signs. To assess the risk factors for the occurrence of ECG abnormalities. Methods: We analyzed retrospectively 281 seizures in 81 patients with intractable epilepsy who had prolonged video-EEG and two-channel ECG. The nature and timing of heart rate changes compared to the electrographic and clinical seizure onset was determined. The ictal period (including one minute preictally and three minutes postictally) was analyzed for cardiac arrhythmias, conduction and repolarization abnormalities. Risk factors for cardiac abnormalities were investigated using parametric and non-parametric statistics. Results: There was an increase in heart rate of at least 10 beats/minute in 73% of seizures (93% of patients) and this occurred most often around seizure onset. In 23% of seizures (49% of patients) the rate increase preceded both the electrographic and the clinical onset. ECG abnormalities were found in 26% of seizures (44% of patients). One patient had an asystole for 30 seconds. Long seizure duration increased the occurrence of ECG abnormalities. No other risk factor was found. Conclusions: Heart rate changes occur frequently and occur around the time or even before the earliest electrographic or clinical change. The change can clarify the timing of seizure onset and the specific rate pattern may be useful for seizure diagnosis and for automatic seizure detection. ECG abnormalities occur often and repeatedly in several seizures of the same patient. [source] Fully Autonomous Preload-Sensitive Control of Implantable Rotary Blood PumpsARTIFICIAL ORGANS, Issue 9 2010Andreas Arndt Abstract A pulsatility-based control algorithm with a self-adapting pulsatility reference value is proposed for an implantable rotary blood pump and is to be tested in computer simulations. The only input signal is the pressure difference across the pump, which is deduced from measurements of the pump's magnetic bearing. A pulsatility index (PI) is calculated as the mean absolute deviation from the mean pressure difference. As a second characteristic, the gradient of the PI with respect to the pump speed is derived. This pulsatility gradient (GPI) is used as the controlled variable to adjust the operating point of the pump when physiological variables such as the systemic arterial pressure, left ventricular contractility, or heart rate change. Depending on the selected mode of operation, the controller is either a linear controller or an extremum-seeking controller. A supervisory mechanism monitors the state of the system and projects the system into the region of convergence when necessary. The controller of the GPI continuously adjusts the reference value for PI. An underlying robust linear controller regulates the PI to the reference value in order to take into account changes in pulmonary venous return. As a means of reacting to sudden changes in the venous return, a suction detection mechanism was included. The control system is robustly stable within a wide range of physiological variables. All the clinician needs to do is to select between the two operating modes. No other adjustments are required. The algorithm showed promising results which encourage further testing in vitro and in vivo. [source] Infants' Attention to Patterned Stimuli: Developmental Change From 3 to 12 Months of AgeCHILD DEVELOPMENT, Issue 3 2006Mary L. Courage To examine the development of look duration as a function of age and stimulus type, 14- to 52-week-old infants were shown static and dynamic versions of faces, Sesame Street material, and achromatic patterns for 20 s of accumulated looking. Heart rate was recorded during looking and parsed into stimulus orienting, sustained attention, and attention termination phases. Infants' peak look durations indicated that prior to 26 weeks there was a linear decrease with age for all stimuli. Older infants' look durations continued to decline for patterns but increased for Sesame Street and faces. Measures of heart rate change during sustained attention and the proportion of time spent in each phase of attention confirmed infants' greater engagement with the more complex stimuli. [source] Heart Rate Response to Intravenous Catheter PlacementACADEMIC EMERGENCY MEDICINE, Issue 9 2003Joel M. Bartfield MD Abstract Objective: To investigate the relationship between change in heart rate and pain and anxiety caused by intravenous catheter (IV) placement. Methods: An observational study was performed in a university-based tertiary care emergency department. Patients who required IV placement as part of their management were considered as possible subjects. Heart rates were recorded at the following times: baseline, tourniquet placement, and IV placement. Immediately after IV placement, subjects recorded pain and anxiety scores using 100-mm visual analog scales. Percentage change in heart rate (compared with baseline) was calculated at time of tourniquet placement (anxiety) and IV placement (pain). Simple linear regression analyses were performed comparing pain scores with percent change in heart rate at the time of IV and tourniquet placement. Significance was defined as p < 0.05. Results: Ninety subjects were enrolled. Subjects had a mean age of 48 years, and 54% were women. There was a normal distribution of heart rate changes, with greater than 80% of all subjects having a 10% or less change in heart rates. The results of the analysis of pain scores versus percentage change in heart rate at IV placement yielded a Pearson correlation coefficient of 0.13 (p = 0.2). The results of the analysis of anxiety scores versus percentage change in heart rate at tourniquet placement yielded a Pearson correlation coefficient of 0.014 (p = 0.9). Conclusions: Changes in heart rate do not correlate with pain and anxiety associated with IV placement. [source] Heart Rate Changes and ECG Abnormalities During Epileptic Seizures: Prevalence and Definition of an Objective Clinical SignEPILEPSIA, Issue 8 2002Maeike Zijlmans Summary: ,Purpose: To determine the prevalence of heart rate changes and ECG abnormalities during epileptic seizures and to determine the timing of heart rate changes compared to the first electrographic and clinical signs. To assess the risk factors for the occurrence of ECG abnormalities. Methods: We analyzed retrospectively 281 seizures in 81 patients with intractable epilepsy who had prolonged video-EEG and two-channel ECG. The nature and timing of heart rate changes compared to the electrographic and clinical seizure onset was determined. The ictal period (including one minute preictally and three minutes postictally) was analyzed for cardiac arrhythmias, conduction and repolarization abnormalities. Risk factors for cardiac abnormalities were investigated using parametric and non-parametric statistics. Results: There was an increase in heart rate of at least 10 beats/minute in 73% of seizures (93% of patients) and this occurred most often around seizure onset. In 23% of seizures (49% of patients) the rate increase preceded both the electrographic and the clinical onset. ECG abnormalities were found in 26% of seizures (44% of patients). One patient had an asystole for 30 seconds. Long seizure duration increased the occurrence of ECG abnormalities. No other risk factor was found. Conclusions: Heart rate changes occur frequently and occur around the time or even before the earliest electrographic or clinical change. The change can clarify the timing of seizure onset and the specific rate pattern may be useful for seizure diagnosis and for automatic seizure detection. ECG abnormalities occur often and repeatedly in several seizures of the same patient. [source] Hypertonic Saline Treatment of Severe Hyperkalemia in Nonnephrectomized DogsACADEMIC EMERGENCY MEDICINE, Issue 9 2000Justin L. Kaplan MD Abstract. Objectives: To determine whether a hypertonic saline bolus improves cardiac conduction or plasma potassium levels more than normal saline infusion within 15 minutes of treatment for severe hyperkalemia. Previously with this model, 8.4% sodium chloride (NaCl) and 8.4% sodium bicarbonate (NaHCO3) lowered plasma potassium equally effectively. Methods: This was a crossover study using ten conditioned dogs (14-20 kg) that received, in random order, each of three intravenous (IV) treatments in separate experiments at least one week apart: 1) 2 mmol/kg of 8.4% NaCl over 5 minutes (bolus); 2) 2 mmol/kg of 0.9% NaCl over one hour (infusion); or 3) no treatment (control). Using isoflurane anesthesia and ventilation (pCO2= 35-40 torr), 2 mmol/kg/hr of IV potassium chloride (KCl) was infused until conduction delays (both absent p-waves and ,20% decrease in ventricular rate in ,5 minutes) were sustained for 15 minutes. The KCl was then decreased to 1 mmol/kg/hr (maintenance) for 2 hours and 45 minutes. Treatment (0 minutes) began after 45 minutes of maintenance KCl. Results: From 0 to 15 minutes, mean heart rate increased 29.6 (95% CI = 12.2 to 46; p < 0.005) beats/min more with bolus than infusion and 23.4 (95% CI = 2.6 to 43.5; p < 0.03) beats/min more with bolus than control. No clinically or statistically significant difference was seen in heart rate changes from 0 to 30 minutes. Decreases in potassium from 0 to 15 minutes were similar with bolus, infusion, and control. Conclusions: In this model, 8.4% NaCl bolus reversed cardiac conduction abnormalities within the first 15 minutes after treatment, more rapidly than did the 0.9% NaCl infusion or control. This reversal occurred despite similar reductions in potassium levels. [source] Treatment of Vasodepressor Carotid Sinus Syndrome with Midodrine: A Randomized, Controlled Pilot StudyJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 1 2005Allan Moore MRCPI Objectives: To evaluate the efficacy of treatment of the vasodepressor form of carotid sinus hypersensitivity (carotid sinus syndrome (CSS)) with midodrine. Design: A prospective, double-blind, randomized, controlled trial of crossover design. Setting: A dedicated outpatient facility with access to tilt-table, digital arterial photoplethysmography, and 24-hour ambulatory blood pressure (BP) monitoring equipment. Participants: Ten older adults (4 male, 6 female, mean age 75, range 66,86 years) with a history of unexplained syncope who displayed an asymptomatic decrease in systolic BP (SBP) of more than 50 mmHg or a symptomatic decrease of more than 30 mmHg within 30 seconds of carotid sinus massage (CSM). Measurements: Symptom reproduction and BP and heart rate changes were evaluated after CSM in supine and semierect positions on the right and then left sides. These measurements were performed on the final day of placebo and active-treatment phases. Ambulatory 24-hour BP monitoring took place on the penultimate and final days of each treatment phase. Results: Eight patients were symptomatic after their initial CSM. The mean±standard deviation SBP decrease after initial CSM was 54±22 mmHg. Initial mean 24-hour ambulatory BP was 127/70±7/5 mmHg. Eight patients reported symptoms after CSM at the end of the placebo phase. The mean SBP decrease at the end of the placebo phase was 49±12 mmHg. The mean 24-hour ambulatory BP was 127/69±9/7 mmHg. One patient reported symptoms after CSM at the end of the active-treatment phase. The mean SBP decrease at the end of the active-treatment phase was 36±9 mmHg. The mean 24-hour ambulatory BP at the end of the treatment phase was 133/75±7/6 mmHg. The differences in symptom reporting and mean SBP decrease after CSM were both significant (P<.01 and P=.03, respectively). Conclusion: The results of this pilot study suggest that treatment of vasodepressor CSS with midodrine significantly reduced the rate of symptom reporting and attenuated SBP decreases after CSM but increased mean 24-hour ambulatory BP. [source] Effectiveness of maternity support belts in reducing low back pain during pregnancy: a reviewJOURNAL OF CLINICAL NURSING, Issue 11 2009Simone SM Ho Aims., This article aims to review the literature published to date on the types, current use, the biomechanical effects and adverse effects of maternity support belts for low back pain during pregnancy, to identify future research directions. Background., Lumbar/pelvic support belts are frequently recommended for the prevention and treatment of low back pain during pregnancy. Design., Systematic review. Methods., MEDLINE, CINAHL, the Cochrane Library and patents databases were electronically searched. Results., Maternity support belts belong to one of the four main types of maternity support garments, which are widely commercially-available. Current research showed limited evidence in support of the commercial maternity products regarding the effectiveness in the prevention and/or treatment of low back pain during pregnancy, other than that from the manufacturers. However, potential stabilisation effect of maternity support belt was demonstrated in some studies. Adverse effects reported include increased pain, fetal heart rate changes, skin irritation and discomfort. Conclusions., There is insufficient scientific evidence to conclude that wearing maternity support belts reduces pregnancy-related low back pain and/or pelvic girdle pain. Future research directions in the area of biomechanics and physiology are recommended. Relevance to clinical practice., This review provides comprehensive understanding of the effectiveness of maternity support belts for the relief of low back pain during pregnancy which will facilitate healthcare professionals in providing evidence-based advice to their patients. [source] Blood pressure and heart rate changes during intubationANAESTHESIA, Issue 1 2007A. Ahmed-Nusrath No abstract is available for this article. [source] Correction for QT/RR Hysteresis in the Assessment of Drug-Induced QTc Changes,Cardiac Safety of GadobutrolANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 3 2009M.D., Marek Malik Ph.D. Background: The so-called thorough QT/QTc (TQT) studies required for every new pharmaceutical compound are negative if upper single-sided 95% confidence interval (CI) of placebo and baseline corrected QTc prolongation is <10 ms. This tight requirement has many methodological implications. If the investigated drug has a fast action and ECGs cannot be obtained at stable heart rates, QT/RR hysteresis correction is needed. Methods: This was used in a TQT study of gadobutrol. The TQT study was a randomized double-blind five-times crossover study of three doses of gadobutrol (0.1, 0.3, and 0.5 mmol/kg) that was placebo and positive effect controlled (moxifloxacin 400 mg). The study enrolled 50 healthy subjects with data of all periods. QT/RR hysteresis was assessed from prestudy exercise test ECGs. Among others, comparisons were made between population heart rate correction without hysteresis considerations and combined population heart rate and hysteresis correction. Results: The highest heart rate increase (placebo and baseline controlled) of 13.1 beats per minute (90% CI 9.9,16.4) occurred 1 minute after the administration of the highest dose of gadobutrol. Without hysteresis consideration, the highest ,,QTc were 9.91 ms (90% CI 8.01,11.81) while with hysteresis correction, these values were 7.62 ms (90% CI 6.37,8.87), thus turning a marginally positive TQT study into a negative finding. Conclusion: Hence, omitting hysteresis correction from episodes of fast heart rate changes may lead to incorrect conclusions. Despite substantial rate acceleration, accurate hysteresis correction confirms that gadobutrol does not have any effects on cardiac repolarization that would be within the limits of regulatory relevance. [source] Magnitude of Error Introduced by Application of Heart Rate Correction Formulas to the Canine QT IntervalANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 4 2006Andrew King B.V.M.S. Background: Accurate detection of drug-induced QT interval changes is often confounded by concurrent heart rate changes. Application of heart rate correction formulas has been the traditional approach to account for heart rate,induced QT interval changes, and thereby identify the direct effect of the test article on cardiac repolarization. Despite numerous recent studies identifying the imprecision of these formulas they continue to be applied. Methods: Using a chronic atrioventricular dissociated His-paced canine model, heart rate correction methods were evaluated for their ability to generate a corrected QT interval independent of original heart rate. Additionally, His bundle pacing at a heart rate of 60 beats/min allowed calculation of the magnitude of error introduced by application of heart rate correction formulas. Results: Of the fixed parameter heart rate correction formulas, only Van de Water was able to predict corrected QT values independent of the original heart rate. The magnitude of error discovered by application of heart rate correction formulas varied, but in many cases was very large. Bazett's formula was associated with a mean overcorrection of 67.9 ms; Fridericia's 28.7 ms. Van de Water was the best fixed parameter formula with a mean error of 10.8 ms. As expected, group and individual corrections derived from linear regression of the HR-QT data offered improvement over the traditional formulas. Both were able to predict QTc values independent of the heart rate. However, errors of the magnitude of 10 and 6 ms, respectively, were still introduced. Conclusion: Van de Water and linear regression correction methods were superior to others in this study, but all methods generated QTc errors equal to or much greater than the magnitude of interest for drug safety evaluation. [source] Extended Visual Fixation and Distractibility in Children from Six to Twenty-Four Months of AgeCHILD DEVELOPMENT, Issue 4 2001John E. Richards Distractibility during extended visual fixations in children 6 months to 2 years of age was examined. A children's Sesame Street movie (Follow That Bird) was presented to children (N=40) for a minimum of 20 min while fixation was videotaped and heart rate was recorded. Distractors (computer-generated patterns or another Sesame Street movie) were presented on an adjacent television screen. Consistent with prior research with older preschool-age children, the latency to turn toward the distractor was a function of the length of the look occurring before distractor onset. For the period immediately before distractor onset, children had a greater sustained lowered heart rate for the trials on which they continued looking at the center television monitor than for the trials on which they looked toward the distractor. This pattern of distractibility suggests attention increases over the course of a look toward the television, and that heart rate changes reflect this increase in attention. [source] | ||||||||||