A cost-effectiveness analysis of remote monitoring after pacemaker implantation for bradycardia in Japan.

BACKGROUND: Although remote monitoring (RM) after pacemaker implantation is common, its cost-effectiveness has not been fully investigated. Therefore, we assessed the cost-effectiveness of RM compared with conventional follow-up (CFU) in Japanese patients with pacemakers. METHODS: A Markov model was constructed to analyze costs and quality-adjusted life years after pacemaker implantation. The target population was Japanese patients implanted with a dual-chamber pacemaker for bradycardia. Transition probabilities (e.g. atrial fibrillation, stroke, and device trouble) were obtained from literature and expert sources. Additionally, stroke risk was determined according to anticoagulation and CHADS2 scores. We used a 10-year horizon with sensitivity analyses for significant variables. RESULTS: Compared to CFU, RM was more effective; however, it was also more expensive. When the range of the Japanese willingness-to-pay threshold was considered to be ¥5,000,000, RM was at least cost-neutral relative to the CFU in all elderly patients with pacemakers for bradycardia. The cost-effectiveness of RM relative to CFU could be higher for patients with high CHADS2 scores, especially in patients with a CHADS2 score ≥ 3. Scenario analyses changing the interval between visits to an in-office evaluation in the CFU also demonstrated the same conclusions. In particular, when the interval between office visits was 1 year for the CFU, the RM could be more cost-effective. CONCLUSIONS: This study demonstrated that RM can be a cost-effective option for Japanese patients, especially those with high CHADS2 scores and long-term intervals between office visits.

Permanent pacemaker implantation in pediatric heart transplant recipients: A systematic review and evidence quality assessment.

Bradyarrhythmias are a common complication following pediatric OHT and may require permanent pacemaker implantation (PPM). The purpose of this study was to investigate the incidence, predictors, and outcomes of children undergoing PPM implantation following OHT. A PRISMA-compliant systematic literature review was performed using the PubMed database and the Cochrane Library (end-of-search date: January 27, 2019). The Newcastle-Ottawa scale and the Joanna Briggs Institute tool were used to assess the quality of cohort studies and case reports, respectively. We analyzed data from a total of 11 studies recruiting 7198 pediatric patients who underwent heart transplant. PPM implantation was performed in 1.9% (n = 137/7,198; 95% CI: 1.6-2.2) of the patients. Most patients underwent dual-chamber pacing (46%, 95% CI: 32.6-59.7). Male-to-female ratio was 1.3:1. Mean patient age at the time of OHT was 10.1 ± 6.3. Overall, biatrial anastomosis was used in 62.2% (95% CI: 52.8-70.6) of the patients. The bicaval technique was performed in the remaining 37.8% (95% CI: 29.4-47.1). Sinus node dysfunction was the most frequent indication for PPM implantation (54.4%; 95% CI: 42.6-65.7) followed by AV block (45.6%; 95% CI: 34.3-57.3). The median time interval between OHT and PPM implantation ranged from 17 days to 12.5 years. All-cause mortality was 27.9% (95% CI: 18.6-39.6) during a median follow-up of 5 years. PPM implantation is rarely required after pediatric OHT. The most common indication for pacing is sinus node dysfunction, and patients undergoing biatrial anastomosis may be more likely to require PPM.

Suffer the Infants: A Severe Case of Pertussis in Oregon, 2012.

Pertussis remains a public health concern in Oregon, especially among young infants. The disease can be severe in this age group and is associated with a high inpatient cost. This report describes an Oregon infant who was hospitalized with pertussis for 90 days, required extracorporeal oxygenation for 43 days, suffered complications including stroke, and had hospital charges totaling $1.5 million. Pertussis morbidity among young infants argues for vaccination of women during each pregnancy and of infants beginning promptly at two months of age.

Dual-chamber pacemakers for treating symptomatic bradycardia due to sick sinus syndrome without atrioventricular block: a systematic review and economic evaluation.

BACKGROUND: Bradycardia [resting heart rate below 60 beats per minute (b.p.m.)] can be caused by conditions affecting the natural pacemakers of the heart, such as sick sinus syndrome (SSS) and atrioventricular (AV) blocks. People suffering from bradycardia may present with palpitations, exercise intolerance and fainting. The only effective treatment for patients suffering from symptomatic bradycardia is implantation of a permanent pacemaker. OBJECTIVE: To appraise the clinical effectiveness and cost-effectiveness of dual-chamber pacemakers compared with single-chamber atrial pacemakers for treating symptomatic bradycardia in people with SSS and no evidence of AV block. DATA SOURCES: All databases (MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, Health Technology Assessment database, NHS Economic Evaluations Database) were searched from inception to June 2014. METHODS: A systematic review of the clinical and economic literature was carried out in accordance with the general principles published by the Centre for Reviews and Dissemination. Randomised controlled trials (RCTs) evaluating dual-chamber and single-chamber atrial pacemakers and economic evaluations were included. Pairwise meta-analysis was carried out. A de novo economic model was developed. RESULTS: Of 493 references, six RCTs were included in the review. The results were predominantly influenced by the largest trial DANPACE. Dual-chamber pacing was associated with a statistically significant reduction in reoperation [odds ratio (OR) 0.48, 95% confidence interval (CI) 0.36 to 0.63] compared with single-chamber atrial pacing. The difference is primarily because of the development of AV block requiring upgrade to a dual-chamber device. The risk of paroxysmal atrial fibrillation was also reduced with dual-chamber pacing compared with single-chamber atrial pacing (OR 0.75, 95% CI 0.59 to 0.96). No statistically significant difference was found between the pacing modes for mortality, heart failure, stroke, chronic atrial fibrillation or quality of life. However, the risk of developing heart failure may vary with age and device. The de novo economic model shows that dual-chamber pacemakers are more expensive and more effective than single-chamber atrial devices, resulting in a base-case incremental cost-effectiveness ratio (ICER) of £6506. The ICER remains below £20,000 in probabilistic sensitivity analysis, structural sensitivity analysis and most scenario analyses and one-way sensitivity analyses. The risk of heart failure may have an impact on the decision to use dual-chamber or single-chamber atrial pacemakers. Results from an analysis based on age (> 75 years or ≤ 75 years) and risk of heart failure indicate that dual-chamber pacemakers dominate single-chamber atrial pacemakers (i.e. are less expensive and more effective) in older patients, whereas dual-chamber pacemakers are dominated by (i.e. more expensive and less effective) single-chamber atrial pacemakers in younger patients. However, these results are based on a subgroup analysis and should be treated with caution. CONCLUSIONS: In patients with SSS without evidence of impaired AV conduction, dual-chamber pacemakers appear to be cost-effective compared with single-chamber atrial pacemakers. The risk of developing a complete AV block and the lack of tools to identify patients at high risk of developing the condition argue for the implantation of a dual-chamber pacemaker programmed to minimise unnecessary ventricular pacing. However, considerations have to be made around the risk of developing heart failure, which may depend on age and device. STUDY REGISTRATION: This study is registered as PROSPERO CRD42013006708. FUNDING: The National Institute for Health Research Health Technology Assessment programme.

Clinical and genetic predictors of major cardiac events in patients with Anderson-Fabry Disease.

BACKGROUND: Anderson-Fabry Disease (AFD) is an X linked lysosomal storage disorder caused by mutations in the α-galactosidase A gene. Some mutations are associated with prominent and, in many cases, exclusive cardiac involvement. The primary aims of this study were to determine the incidence of major cardiac events in AFD and to identify clinical and genetic predictors of adverse outcomes. METHODS AND RESULTS: We studied 207 patients with AFD (47% male, mean age 44 years, mean follow-up 7.1 years). Fifty-eight (28%) individuals carried mutations that have been previously associated with a cardiac predominant phenotype. Twenty-one (10%) developed severe heart failure (New York Heart Association functional class (NYHA) ≥3), 13 (6%) developed atrial fibrillation (AF), 13 (6%) received devices for the treatment of bradycardia; there were a total of 7 (3%) cardiac deaths. The incidence of the primary endpoint (a composite of new onset AF, NYHA ≥ 3 symptoms, device insertion for bradycardia and cardiac death) was 2.64 per 100 person-years (CI 1.78 to 3.77). Age (HR 1.04, CI 1.01 to 1.08, p=0.004), Mainz Severity Score Index score (HR 1.05, CI 1.01 to 1.09, p=0.012) and QRS duration (HR 1.03, CI 1.00 to 1.05, p=0.020) were significant independent predictors of the primary endpoint. The presence of a cardiac genetic variant did not predict the primary end point. CONCLUSIONS: AFD is associated with a high burden of cardiac morbidity and mortality. Adverse cardiac outcomes are associated with age, global disease severity and advanced cardiac disease but not the presence of cardiac genetic variants.

ECG in neonate mice with spinal muscular atrophy allows assessment of drug efficacy.

Molecular technologies have produced diverse arrays of animal models for studying genetic diseases and potential therapeutics. Many have neonatal phenotypes. Spinal muscular atrophy (SMA) is a neuromuscular disorder primarily affecting children, and is of great interest in translational medicine. The most widely used SMA mouse models require all phenotyping to be performed in neonates since they do not survive much past weaning. Pre-clinical studies in neonate mice can be hindered by toxicity and a lack of quality phenotyping assays, since many assays are invalid in pups or require subjective scoring with poor inter-rater variability. We find, however, that passive electrocardiography (ECG) recording in conscious 11-day old SMA mice provides sensitive outcome measures, detecting large differences in heart rate, cardiac conduction, and autonomic control resulting from disease. We find significant drug benefits upon treatment with G418, an aminoglycoside targeting the underlying protein deficiency, even in the absence of overt effects on growth and survival. These findings provide several quantitative physiological biomarkers for SMA preclinical studies, and will be of utility to diverse disease models featuring neonatal cardiac arrhythmias.

A woman who lost weight at the cost of her heartbeat.

With increasing prevalence of obesity worldwide, the number of patients undergoing bariatric surgery is also rising. Although the incidence of adverse outcomes associated with bariatric surgery has reduced, the physiological compensatory changes occurring after weight loss can lead to some unavoidable outcomes. One such condition is sinus bradycardia. The pathophysiology behind this is well studied but there is little awareness about this outcome. Sinus bradycardia in this clinical setting is generally asymptomatic and does not require any treatment. Extensive cardiac workup and unnecessary treatment can be avoided by increasing awareness among healthcare providers.

Assessment of adverse events and predictors of neurological recovery after therapeutic hypothermia.

BACKGROUND: Therapeutic hypothermia improves neurological recovery after witnessed cardiac arrest from ventricular fibrillation or tachycardia. Its application is expanding despite associated adverse events. OBJECTIVE: To assess the occurrence of adverse events and predictors of good versus poor neurological recovery after therapeutic hypothermia. METHODS: A single-center, retrospective review of medical records of 91 patients who received therapeutic hypothermia for ≥6 hours. Adverse events included laboratory abnormalities, shivering, acute kidney injury, or infection. Cerebral performance categories (CPC) scores delineated good (CPC of 1-3) or poor (CPC of 4 or 5) neurological outcomes. Groups were compared and parameters evaluated for effect on neurological recovery using backward logistic regression analysis. RESULTS: Therapeutic hypothermia was used for several indications, and 42 patients (46.2%) had good neurological recovery. Demographic parameters were similar between groups. Common adverse events were hypoglycemia (98.9%), shivering (84.6%), bradycardia (58.2%), electrolyte abnormalities (26.4%-91.2%), acute kidney injury (52.8%), infection (48.4%), and coagulopathy (40.7%). Characteristics independently associated with neurological recovery included faster return of spontaneous circulation (ROSC), quicker initiation of cooling, and the occurrence of infections. Pulseless electrical activity, faster achievement of goal cooling temperature, seizure, and the administration of insulin or epinephrine were inversely related to neurological recovery. CONCLUSIONS: Adverse events of therapeutic hypothermia were numerous and frequent, necessitating monitoring. Neurological recovery is primarily driven by the type of arrest, the rapidity of ROSC, the time needed to provide and achieve therapeutic hypothermia, the development of seizures or infection, and the use of insulin or epinephrine.

Same-day bidirectional endoscopy with nonanesthesiologist administration of propofol: safety and cost-effectiveness compared with separated exams.

BACKGROUND AND AIM: The safety and cost-effectiveness of a combination of esophagogastroduodenoscopy (EGD) and colonoscopy [or bidirectional endoscopy (BDE)] versus alternative-day EGD and colonoscopy when using nonanesthesiologist administration of propofol have never been evaluated. PATIENTS AND METHODS: This was a single-center prospective registry of consecutive American Society of Anaesthesiology class I-III outpatients undergoing EGD, colonoscopy, and BDE. Propofol was the sole sedative used. Adverse events, recovery time, and procedure-related costs were analyzed. RESULTS: Among the 1500 study participants (51.5% women), EGD, colonoscopy, and BDE were carried out on 449, 702, and 349 patients, respectively. All patients were discharged directly from the endoscopy unit. No sex differences were found with respect to age (mean 54.4, range 18-96 years), BMI, or procedure type. Propofol doses for BDE were 25.9% less than when EGD and colonoscopy were performed separately (P<0.001). Adverse events, including transient O2 saturation less than 90%, systolic blood pressure less than 90 mmHg, and bradycardia (<50 bpm), appeared in 10.7% of single EGD and 8.6% of EGD within BDE; for colonoscopies, the figures were 8.6 and 9.5%, respectively (P=NS). Recovery time to discharge after BDE was 47.9% shorter than when EGD and colonoscopy were performed separately (P<0.001). The cost of same-day BDE was 28.1% lower than that of EGD and colonoscopy performed as separated procedures (P<0.001). CONCLUSION: Same-day BDE with nonanesthesiologist administration of propofol resulted in reductions in propofol doses, recovery time, and procedure-related costs as compared with carrying out EGD and colonoscopy separately, without an increase in adverse events.

Management of arrhythmias in the perioperative setting.

Perioperative arrhythmias are a common complication of surgery, with incidence ranging from 4% to 20% for noncardiothoracic procedures, depending on the type of surgery performed. The immediate postoperative period is a dynamic time and is associated with many conditions conducive to the development of postoperative arrhythmias. The presence of postoperative atrial fibrillation is associated with increased morbidity, ICU stay, length of hospitalization, and hospital costs. The associated burdens are expected to rise in the future, given that the population undergoing cardiac surgery is getting older and sicker. Thousands of patients undergo major surgery each year and a major complication of these procedures is the occurrence of perioperative arrhythmia. It is imperative for clinicians to be up-to-date on current management of these arrhythmias.

A retrospective review to evaluate the safety of right heart catheterization via the internal jugular vein in the assessment of pulmonary hypertension.

BACKGROUND: Right heart catheterization (RHC) is important in the evaluation of pulmonary hypertension, but is not without risk. HYPOTHESIS: We wished to assess the safety, efficacy, and tolerability of RHC performed via the internal jugular vein (IJV) at our tertiary cardiothoracic center. METHODS: A retrospective review of the medical records for all patients undergoing RHC via the IJV between January 1, 2007 and July 31, 2009 was performed. We do not routinely use ultrasound guidance or stop anticoagulation. Operators with a median experience of 450 procedures performed the RHCs. RESULTS: Right heart catheterization was performed on 349 patients with a median age of 66 years (range, 17-89), median mean pulmonary artery pressure of 30 mm Hg (range, 8-69), and a median internationalized normal ratio of 2.5. Of 349 patients, we were unable to obtain intravenous access in only 1 patient; 342 (98%) patients tolerated RHC with local anesthetic alone; and 6 patients required additional sedation with benzodiazepines. The median time for the procedure was 15 minutes. Complications occurred in 6 patients (1.7%) and included carotid puncture (n = 3), sinus bradycardia below 45 beats/min, which responded promptly to atropine and intravenous fluid (n = 2), and complete heart block without hemodynamic compromise (n = 1). There were no pneumothoraxes, pulmonary hemorrhage, or deaths related to the procedure. CONCLUSION: Right heart catheterization via the IJV is quick, safe, and well tolerated. It is not associated with an increased risk of pneumothorax or other complications when performed by experienced operators.

Shoulder arthroscopy positioning: lateral decubitus versus beach chair.

Since the introduction of the beach chair position for shoulder arthroscopy, orthopaedic surgeons have debated whether the beach chair or lateral decubitus is superior. Most surgeons use the same patient position to perform all of their arthroscopic shoulder procedures, regardless of the pathology. Each position has its advantages and disadvantages. The evidence regarding the efficiency, efficacy, and risks of the lateral decubitus and the beach chair positions for shoulder arthroscopy does not show one position to be superior. This review presents a comparison of these positions with regard to setup, surgical visualization, access, and patient risk.

[Blood transfusion incident analysis by ALARM method]. / Analyse d'un incident transfusionnel par la méthode ALARM.

The hospital risk management department is firstly involved in the methodological analysis of grade zero transfusion incidents. The system is based on a subsequent analysis process in compliance with the ongoing requirements of the Haute Autorité de santé (HAS) for a reactive approach to risk, allowing to identify failures and start the appropriate preventive and corrective measures. The use of the association of litigation and risk management method makes easier the grade zero analysis and brings to light the team or institutional, organizational, temporal, individual factors representative of undesirable effects. Two main factors come out again from this analysis, the absence of the identification bracelet coupled with a disrespect of transfusion procedures in force. The whole institution must be concerned by these improvement actions. Health teams should overcome difficulties to be totally involved in such a process. Human factors' recognition, establishment of clear and effective communication between individuals and information sharing should provide optimum quality care services which are safe and free of unnecessary risks.

The effectiveness and cost-effectiveness of dual-chamber pacemakers compared with single-chamber pacemakers for bradycardia due to atrioventricular block or sick sinus syndrome: systematic review and economic evaluation.

OBJECTIVES: To estimate the effectiveness and cost-effectiveness of dual-chamber pacemakers versus single-chamber atrial or single-chamber ventricular pacemakers in the treatment of bradycardia due to sick sinus syndrome (SSS) or atrioventricular block (AVB). DATA SOURCES: Electronic databases and relevant Internet sites. Contact with device manufacturers and experts in the field. REVIEW METHODS: A systematic review was carried out of randomised controlled trials (RCTs). The quality of selected studies was appraised using standard frameworks. Meta-analyses, using random effects models, were carried out where appropriate. Limited exploration of heterogeneity was possible. Critical appraisal of economic evaluations was carried out using two frameworks. A decision-analytic model was developed using a Markov approach, to estimate the cost-effectiveness of dual-chamber versus ventricular or atrial pacing over 5 and 10 years as cost per quality-adjusted life-year (QALY). Uncertainty was explored using one-way and probabilistic sensitivity analyses. RESULTS: The searches retrieved a systematic review of effectiveness and cost-effectiveness published in 2002, four parallel group RCTs and 28 cross-over trials. Dual-chamber pacing was associated with lower rates of atrial fibrillation, particularly in SSS, than ventricular pacing, and prevents pacemaker syndrome. Higher rates of atrial fibrillation were seen with dual-chamber pacing than with atrial pacing. Complications occurred more frequently in dual-chamber pacemaker insertion. The cost of a dual-chamber system, over 5 years, including cost of complications and subsequent clinical events in the population, was estimated to be around 7400 pounds. The overall cost difference between single and dual systems is not large over this period: around 700 pounds more for dual-chamber devices. The cost-effectiveness of dual-chamber compared with ventricular pacing was estimated to be around 8500 pounds per QALY in AVB and 9500 pounds in SSS over 5 years, and around 5500 pounds per QALY in both populations over 10 years. Under more conservative assumptions, the cost-effectiveness of dual-chamber pacing is around 30,000 pounds per QALY. The probabilistic sensitivity analysis showed that, under the base-case assumptions, dual-chamber pacing is likely to be considered cost-effective at levels of willingness to pay that are generally considered acceptable by policy makers. In contrast, atrial pacing may be cost-effective compared with dual-chamber pacing. CONCLUSIONS: Dual-chamber pacing results in small but potentially important benefits in populations with SSS and/or AVB compared with ventricular pacemakers. Pacemaker syndrome is a crucial factor in determining cost-effectiveness; however, difficulties in standardising diagnosis and measurement of severity make it difficult to quantify. Dual-chamber pacing is in common usage in the UK. Recipients are more likely to be younger. Insufficient evidence is currently available to inform policy on specific groups who may benefit most from pacing with dual-chamber devices. Further important research is underway. Outstanding research priorities include the economic evaluation of UKPACE studies of the classification, diagnosis and utility associated with pacemaker syndrome and evidence on the effectiveness of pacemakers in children.

Crisis management during anaesthesia: bradycardia.

BACKGROUND: Bradycardia in association with anaesthesia may have many potential causes and associated conditions, some rare and/or obscure. A prompt appropriate response is important as some homeostatic mechanisms may be impaired under anaesthesia. OBJECTIVES: To examine the role of a previously described core algorithm "COVER ABCD-A SWIFT CHECK", supplemented by a specific sub-algorithm for bradycardia, in the management of bradycardia occurring in association with anaesthesia. METHODS: The potential performance of this structured approach for each of the relevant incidents among the first 4000 reported to the Australian Incident Monitoring Study (AIMS) was compared with the actual management as reported by the anaesthetists involved. RESULTS: From the first 4000 incidents reported to AIMS, 265 reports which described bradycardia during anaesthesia were extracted and studied. Bradycardia was associated with hypotension in 51% of cases, cardiac arrest in 25% of cases and hypertension in one case. In 22% of reports apparent desaturation or an abnormality of ventilation was described. Bradycardia was caused by drug events (28%), airway related events (16%), autonomic reflexes (14%), and regional anaesthesia (9%). Airway and drug events caused 75% of cases involving children. It was considered that, correctly applied, the core algorithm COVER would have diagnosed 53 cases (20%) and led to corrective management in 45 (85%) of these; this included an important subset of airway and ventilation problems. Completion of COVER ABCD-A SWIFT CHECK followed by the specific sub-algorithm for bradycardia would have resulted in diagnosis and appropriate management in all but two cases. It would have led to earlier recognition of the problem and/or better management in 11 cases (4%) when compared with the actual management described in the reports. CONCLUSION: Steps should be taken to manage bradycardia whilst associated conditions are managed concurrently. Analysis of cardiac rhythm should not be pursued to the exclusion of supportive therapy. The use of a structured approach in the management of bradycardia associated with anaesthesia is likely to improve management in the small percentage of cases in which the diagnosis of the cause may be missed or delayed.

[Epidural vs. intradural anesthesia in ambulatory surgery]. / Anestesia epidural frente a anestesia intradural en cirugía ambulatoria.

Spinal anesthesia is the technique of choice for many outpatient procedures. With appropriate screening and preparation, it can provide excellent surgical conditions and highly satisfactory anesthesia for the patient, while remaining cost-effective. Intradural anesthesia has advantages over epidural anesthesia: technical simplicity, rapid onset, efficacy and depth of blockade. Its use has been controversial, however, for many years due to the potential risk of headache after puncture of the dura mater. Epidural anesthesia causes fewer hemodynamic changes and provides greater dose flexibility and local anesthetic concentration, with less risk of headache after accidental puncture of the dura mater. The drawbacks are that it takes longer to perform and onset of blockade comes later. Both techniques are valid alternatives to general anesthesia in outpatient surgery. The choice of one over the other will depend on patient characteristics, availability of a presurgical area, and the anesthesiologist's skill.

Brady-tachycardia syndrome after radiotherapy for lung cancer. Assessment by computed tomography and carbon-11 methionine positron emission tomography.

A 74-year-old male who had received radiotherapy (total 54 Gy) for right lung cancer 7 months earlier developed a symptomatic brady-tachycardia syndrome requiring the implantation of a permanent pacemaker. Chest CT showed a pulmonary tumor of 2-cm diameter in the right lower lobe with direct extension into the surrounding tissue, suggesting the possibility of cardiac invasion. Carbon-11 methionine positron emission tomography (PET) indicated the absence of visible invasion of the heart with lung cancer. The bradytachycardia syndrome, therefore, was considered to be associated with sinus node injury due to radiation. Carbon-11 methionine PET metabolic imaging might play an important role in evaluating noninvasively the cause of the arrhythmia in this patient.

Assessment of cardiac autonomic nervous activities during heliox exposure at 24 atm abs.

BACKGROUND: This experiment was designed to examine the involvement of the autonomic nervous system in the production of hyperbaric bradycardia. METHODS: Four male divers were exposed to a He-O2 (heliox) environment at 24 atmosphere absolute (atm abs) for 7 d. The heart rate (HR) and respiratory rate were recorded at rest in the morning (0700 h) and at night (2230 h) on 1 d during a 5-d predive control, 2 d during a 7-d saturation dive at 24 atm abs, 2 d during decompression, and on 1 d during a 4-d postdive period. Cardiac sympathetic and parasympathetic activities were estimated by using a spectral analysis of the variability of R-R intervals. RESULTS: The morning HR did not fluctuate throughout the experimental days. The night time HR decreased (p < 0.05) by 11.8% on the first day at 24 atm abs compared with that of the predive control. The bradycardia diminished gradually and returned to the predive level with continued exposure at 24 atm abs. The high-frequency power of the cardiac variability, an index of cardiac parasympathetic activity, increased (p < 0.05) only in the first night at 24 atm abs, whereas the low-frequency power and a ratio of low- to high-frequency power, an index of cardiac sympathetic activity, were unchanged. CONCLUSIONS: The present results suggest that an increased parasympathetic activity rather than a decrease in the sympathetic activity is responsible for the bradycardia on exposure to heliox dry saturation dive at 24 atm abs. The mechanism of the gradual disappearance of the bradycardia is unknown, but perhaps it may be related to the development of cardiovascular deconditioning.