Home About us Contact
|
Home About us Contact | ||
|
|
||
Pacemaker Function (pacemaker + function)
Selected AbstractsSinus Pacemaker Function after Cardioversion of Chronic Atrial Fibrillation: Is Sinus Node Remodeling Related with Recurrence?JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 7 2001EMMANUEL G. MANIOS M.D. Sinus Node Remodeling and Atrial Fibrillation. Introduction: The objective of this study was to investigate the temporal changes in sinus node function in postcardioversion chronic atrial fibrillation (AF) patients and their possible relation with the recurrence rates of AF. Methods and Results: In 37 chronic AF patients, internally cardioverted to sinus rhythm, corrected sinus node recovery time (CSNRT), and the pattern of corrected return cycle lengths were assessed 5 to 20 minutes and 24 hours after conversion. The last 20 consecutive patients also were evaluated after autonomic blockade. Twenty subjects with normal atrial structure and no history of AF served as the control group. Patients were followed-up for 1 month for recurrence, and the density of supraventricular ectopic beats per hour was obtained during the first 24 hours after conversion. Fifteen patients (40.5%) relapsed during follow-up. CSNRT values at 600 msec (371 ± 182 msec) and 500 ms (445 ± 338 msec) were significantly higher than those of control subjects (278 ± 157 msec, P = 0.050, and 279 ± 130 msec, P = 0.037, respectively). Significant temporal changes in CSNRT also were observed during the first 24 hours after conversion (600 msec: 308 ± 120 msec, P = 0.034; 500 msec: 340 ± 208 msec, P = 0.017). No significant interaction and temporal effects were observed with regard to corrected return cycle length pattern. Similar data regarding CSNRT and corrected return cycle length pattern were obtained after autonomic blockade. Patients with abnormal CSNRT after cardioversion had higher recurrence rates (50%) than those with normal function (37%; P = NS). Patients who relapsed had a higher density of supraventricular ectopic beats per hour (159 ± 120) compared with those who did not (35 ± 37; P = 0.001). Conclusion: Depressed sinus node function is observed after conversion of chronic AF. Recovery from this abnormality and its independence from autonomic function suggest that AF remodels the sinus node. Our data do not support a causative role of sinus node function in AF recurrence, but they do indicate such a role for the density of atrial ectopic beats. [source] The Effectiveness of Transtelephonic Monitoring of Pacemaker Function in Pediatric PatientsPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 6 2007SCOTT A. FOX M.B.B.S. Background:To determine the sensitivity and specificity, rate of compliance, and predictors of failure of telephone transmission of pacemaker function in a pediatric population. Methods:A total of 2,638 pacemaker transmission records were reviewed retrospectively. Standard calculations of sensitivity, specificity, and positive and negative predictive values were performed. Longitudinal data analysis was used to detect factors influencing the effectiveness of transtelephonic monitoring. The proportion of missed transmissions was calculated, thus enabling assessment of compliance. Logistic regression was performed to determine predictors of poor compliance. Results:Telephone transmission of pacemaker function, as a diagnostic tool, had a sensitivity of 94.8%, specificity of 99.2%, positive predictive value of 82.1%, and negative predictive value of 99.9%. Longitudinal analysis failed to show any significant predictors of transmission failure. Compliance with a prescribed transmission reached 84.5% in our patient population. Logistic regression analysis failed to identify any predictors of noncompliance. Conclusion:Values for sensitivity and specificity indicate that telephone transmission is a useful diagnostic tool for assessing pacemaker function at a distance. Negative predictive value is 99.9%, indicating that normal telephone transmissions are very reassuring of normal pacemaker function. Telephone transmission is equally successful in all age groups, genders, distances from a tertiary referral center, underlying diagnoses, pacing modes, and pacemaker models. Compliance with telephone transmission follow-up was higher in our population than in previous studies. [source] Differences in sino-atrial and atrio-ventricular function with age and sex attributable to the Scn5a+/, mutation in a murine cardiac modelACTA PHYSIOLOGICA, Issue 1 2010K. Jeevaratnam Abstract Aim:, To investigate the interacting effects of age and sex on electrocardiographic (ECG) features of Scn5a+/, mice modelling Brugada syndrome. Methods:, Recordings were performed on anaesthetized wild-type (WT) and Scn5a+/, mice and differences attributable to these risk factors statistically stratified. Results:,Scn5a+/, exerted sex-dependent effects upon sino-atrial function that only became apparent with age. RR intervals were greater in old male than in old female Scn5a+/,. Atrio-ventricular (AV) conduction was slower in young female mice, whether WT and Scn5a+/,, than the corresponding young male WT and Scn5a+/,. However, PR intervals lengthened with age in male but not in female Scn5a+/, giving the greatest PR intervals in old male Scn5a+/, compared with either old male WT or young male Scn5a+/, mice. In contrast, PR intervals were similar in old female Scn5a+/, and in old female WT. QTc was prolonged in Scn5a+/, compared with WT, and female Scn5a+/, compared with female WT. Age-dependent alterations in durations of ventricular repolarization relative to WT affected male but not female Scn5a+/,. Thus, T-wave durations were greater in old male Scn5a+/, compared with old male WT, but indistinguishable between old female Scn5a+/, and old female WT. Finally, analysis for combined interactions of genotype, age and sex demonstrated no effects on P wave and QRS durations and QTc intervals. Conclusion:, We demonstrate for the first time that age, sex and genotype exert both independent and interacting ECG effects. The latter suggest alterations in cardiac pacemaker function, atrio-ventricular conduction and ventricular repolarization greatest in ageing male Scn5a+/,. [source] The relationship between melatonin and cortisol rhythms: clinical implications of melatonin therapyDRUG DEVELOPMENT RESEARCH, Issue 3 2005N. Zisapel Abstract Disturbances in circadian rhythm have been linked to chronic diseases such as insomnia, hypertension, diabetes, and depression. Here we review recent studies on the age-related changes in cortisol and melatonin rhythms and then present descriptive statistics on our preliminary findings on the rectification of the cortisol rhythms by melatonin therapy in elderly patients with insomnia. In adults, the melatonin onset typically occurs during low cortisol secretion. Administration of exogenous melatonin around dusk will shift the phase of the human circadian clock to earlier hours (advance phase shift) leading to phase advances in circadian rhythms (e.g., sleep, endogenous melatonin, cortisol). With aging, the production of melatonin declines and is shifted to later hours while the production of cortisol increases and its peak occurs earlier in the night. In a randomized placebo-controlled crossover study with 8 patients with insomnia aged 55 years and older, a group characterized by low and delayed melatonin production, administration of prolonged-release melatonin in the evening was able to rectify the early onset cortisol production. This delay in nocturnal cortisol onset may explain in part the improvement in sleep quality in elderly patients with insomnia, in schizophrenics, and in depressed patients. Support of circadian pacemaker function by melatonin may provide a new strategy in the treatment of disorders related to impairments in the internal temporal order. The clinical benefit from a decrease in cortisol during the early part of the night may lie beyond the improvement of sleep into a better control of blood pressure, metabolism, and mood. Drug Dev. Res. 65:119,125, 2005. © 2005 Wiley-Liss, Inc. [source] A Prospective Pediatric Clinical Trial of Digital Music Players: Do They Interfere with Pacemakers?JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2009CHRISTINE C. CHIU M.Sc. Background: There has been recent concern in the media about iPodÔ interference with pacemakers. We systematically tested two types of digital music players (DMP) on pacemaker or ICD function in children. Methods/Results: Patients were monitored by a 6-lead ECG and programmer telemetry. The pacemaker was tested in bipolar and unipolar sensing at normal and maximal sensitivities. The order of DMP tested was randomized. Each DMP was placed on top of the pacemaker pocket, put into "play" mode three times (5 seconds each), with and without programmer wand placed one cm adjacent to DMP. Pacemaker interference was defined as: pacing inhibition, inappropriate pacing, oversensing, or detection of high-rate episodes associated with the use of DMP. Of the 67 patients (mean age 12 ± 5 years), 62 had pacemakers and five had ICDs; 39 endocardial and 28 epicardial systems. Patients were tested with SansaÔ (67), iPodÔ 30 GB (51), and other DMPs (43). There was no evidence of interference with pacemaker function by any DMP under any of the study conditions (each performed in triplicate). Reproducible programmer telemetry interference was shown in 11 cases (Medtronic 6/47, St. Jude Medical 5/18, Guidant 0/2) related to use of iPodÔ (6), SansaÔ (1), or others (4). None of these were associated with any evidence of pacemaker malfunction. Conclusion: Interference with pacemaker function could not be shown with iPodÔ or MP3 players. No additional precaution beyond standard is necessary for patients with pacemakers when they are using these players. [source] Alcohol Consumption and the Body's Biological ClockALCOHOLISM, Issue 8 2005Rainer Spanagel This review summarizes new findings on the bidirectional interactions between alcohol and the clock genes, underlying the generation of circadian rhythmicity. At the behavioral level, both adult and perinatal ethanol treatments alter the free-running period and light response of the circadian clock in rodents; genetic ethanol preference in alcohol-preferring rat lines is also associated with alterations in circadian pacemaker function. At the neuronal level, it has been shown that ethanol consumption alters the circadian expression patterns of period (per) genes in various brain regions, including the suprachiasmatic nucleus. Notably, circadian functions of ,-endorphin,containing neurons that participate in the control of alcohol reinforcement become disturbed after chronic alcohol intake. In turn, per2 gene activity regulates alcohol intake through its effects on the glutamatergic system through glutamate reuptake mechanisms and thereby may affect a variety of physiological processes that are governed by our internal clock. In summary, a new pathologic chain has been identified that contributes to the negative health consequences of chronic alcohol intake. Thus, chronic alcohol intake alters the expression of per genes, and, as a consequence, a variety of neurochemical and neuroendocrine functions become disturbed. Further steps in this pathologic chain are alterations in physiological and immune functions that are under circadian control, and, as a final consequence, addictive behavior might be triggered or sustained by this cascade. [source] The Effectiveness of Transtelephonic Monitoring of Pacemaker Function in Pediatric PatientsPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 6 2007SCOTT A. FOX M.B.B.S. Background:To determine the sensitivity and specificity, rate of compliance, and predictors of failure of telephone transmission of pacemaker function in a pediatric population. Methods:A total of 2,638 pacemaker transmission records were reviewed retrospectively. Standard calculations of sensitivity, specificity, and positive and negative predictive values were performed. Longitudinal data analysis was used to detect factors influencing the effectiveness of transtelephonic monitoring. The proportion of missed transmissions was calculated, thus enabling assessment of compliance. Logistic regression was performed to determine predictors of poor compliance. Results:Telephone transmission of pacemaker function, as a diagnostic tool, had a sensitivity of 94.8%, specificity of 99.2%, positive predictive value of 82.1%, and negative predictive value of 99.9%. Longitudinal analysis failed to show any significant predictors of transmission failure. Compliance with a prescribed transmission reached 84.5% in our patient population. Logistic regression analysis failed to identify any predictors of noncompliance. Conclusion:Values for sensitivity and specificity indicate that telephone transmission is a useful diagnostic tool for assessing pacemaker function at a distance. Negative predictive value is 99.9%, indicating that normal telephone transmissions are very reassuring of normal pacemaker function. Telephone transmission is equally successful in all age groups, genders, distances from a tertiary referral center, underlying diagnoses, pacing modes, and pacemaker models. Compliance with telephone transmission follow-up was higher in our population than in previous studies. [source] Induction Ovens and Electromagnetic Interference:PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 7p1 2003What is the Risk for Patients with Implanted Pacemakers? Electromagnetic fields may interfere with normal pacemaker function. Despite the introduction of modern pacemakers and bipolar lead systems, electromagnetic interference (EMI) still remains to be a concern during daily lives when patients are exposed to cellular phones, electronic security systems, and several household appliances. The aim of this study was to evaluate potential EMI risk of induction ovens, which are increasingly used in private households. The study included 40 consecutive patients (22 men, 18 women; age73 ± 11 years) with implanted DDD, VVI, VDD, and AAI pacemaker systems. The pacemakers were programmed to unipolar sensing and pacing. Sensitivity remained unchanged, if the measured sensing threshold was more than twice the programmed value; otherwise, it was set at half of the measured sensing threshold. Patients were placed in a sitting position at the closest possible distance of about 20 cm between two cooking pots and pacemaker bending the upper part of the body slightly over the induction oven. The energy was increased stepwise to the maximum. One pot was removed and placed again at the highest oven level. Potential interference was monitored continuously. The study showed no incidence of pacemaker malfunction during the entire test while the patients with intrinsic cardiac rhythms were exposed to the induction oven at varying energy strengths. Likewise, there was no external interference when the patients were paced at heart rates of 10,15 beats/min above their heart rates. The programmed parameters remained unchanged after the study. In conclusion, this study shows no EMI risk of an induction oven in patients with bipolar or right-sided unipolar pacemakers. (PACE 2003; 26[Pt. I]:1494,1497) [source] A Cosmetic Approach for Pectoral Pacemaker Implantation in Young GirlsPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 9 2000ERIC ROSENTHAL Pectoral placement of pacemaker generators, combined with use of a redundant intravascular lead portion, reduces the need for endocardial lead advancement during growth in children. While the use of small generators and submuscular pockets has contributed to cosmetic acceptability, the conventional subclavicular incision may occasionally form a keloid scar that is unacceptable in young girls. A modified implantation technique was used in five girls (age 2.6,13.3 years) during implantation of VDD (n = 2), VVIR (n = 2), and DDDR (n = 1) pacemakers. A 5-cm incision was made in the axilla along the line of the pec-toralis major and dissection was continued below the muscle to create a pocket for the generator. Subclavian vein puncture was performed from the axillary incision and beneath the pectoralis major muscle using standard or extra long needles with a needle guard. Peel away sheaths were used for lead positioning. The generator was placed in the submuscular pocket and the wound closed with absorbable sutures. At follow-up, pacemaker function was excellent and neither the scars nor pacemakers were visible from the front. In conclusion, the axillary incision with direct subclavian vein puncture from below the pectoralis major muscle offers the advantages of pectoral pacemaker implantation through a single cosmetic incision. [source] Preliminary Results with the Simultaneous Use of Implantable Cardioverter Defibrillators and Permanent Biventricular Pacemakers: Implications for Device Interaction and DevelopmentPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 3 2000S. WALKER We report our preliminary experience with the combined use of implantable cardioverter defibrillutors (ICD) and biventricular pacemakers in six patients with heart failure and malignant ventricular arrhythmia. Two patients underwent ICD implantation for malignant ventricular arrhythmia after previous biventricular pacemaker implantation. One patient underwent biventricular pacemaker insertion for NYHA Class III heart failure after previous ICD implantation. Two patients underwent single device implantation. In the sixth patient, a combined implantation failed due to an inability to obtain a satisfactory left ventricular pacemaker lead position. The potential for device interaction was explored during implantation. In two patients a potentially serious interaction was discovered. Subsequent alterations in device configuration and programming prevented these interactions with long-term use. No complication of combined device use has been demonstrated during a mean follow-up of 2 months (range 1-4 months). Satisfactory ICD and pacemaker function has also been demonstrated. We conclude that combined device implantation may be feasible with currently available pacing technology and that further prospective studies are required in this area. [source] Engineering physiologically controlled pacemaker cells with lentiviral HCN4 gene transferTHE JOURNAL OF GENE MEDICINE, Issue 5 2008Gerard J. J. Boink Abstract Background Research on biological pacemakers for the heart has so far mainly focused on short-term gene and cell therapies. To develop a clinically relevant biological pacemaker, long-term function and incorporation of autonomic modulation are crucial. Lentiviral vectors can mediate long-term gene expression, while isoform 4 of the Hyperpolarization-activated Cyclic Nucleotide-gated channel (encoded by HCN4) contributes to pacemaker function and responds maximally to cAMP, the second messenger in autonomic modulation. Material and Methods Action potential (AP) properties and pacemaker current (If) were studied in single neonatal rat ventricular myocytes that overexpressed HCN4 after lentiviral gene transduction. Autonomic responsiveness and cycle length stability were studied using extracellular electrograms of confluent cultured monolayers. Results Perforated patch-clamp experiments demonstrated that HCN4-transduced single cardiac myocytes exhibited a 10-fold higher If than non-transduced single myocytes, along with slow diastolic depolarization, comparable to pacemaker cells of the sinoatrial node, the dominant native pacemaker. HCN4-transduced monolayers exhibited a 47% increase in beating rate, compared to controls. Upon addition of DBcAMP, HCN4-transduced monolayers had beating rates which were 54% faster than baseline and significantly more regular than controls. Conclusions Lentiviral vectors efficiently transduce cardiac myocytes and mediate functional gene expression. Because HCN4-transduced myocytes demonstrate an increase in spontaneous beating rate and responsiveness to autonomic modulation, this approach may be useful to create a biological pacemaker. Copyright © 2008 John Wiley & Sons, Ltd. [source] | |||||||||||||