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Biomedical subjects

R G Charles

Publications and source records attributed to R G Charles.

At least 19 recordsLinked to original sources
PubMed2002

Long-term survival after permanent pacemaker implantation: analysis of predictors for increased mortality.

AIMS: To determine long-term time-related survival and evaluate risk factors for increased mortality in patients following their first permanent pacemaker implantation. METHODS AND RESULTS: Analysis of patient records from implant to follow-up. Patient-specific time-lines were constructed to date of last review or death. Observed survival was estimated by event-free analysis using the Kaplan-Meier method. Expected survival was derived from age- and gender-matched cohorts. Risk factors for mortality were sought using the multivariate Cox proportional hazards method and risk ratios estimated. Eight hundred and thirty-three patients underwent implantation of their first permanent pacemaker from April 1992 to January 1994, and were locally followed up. Survival data were available for 803 (96.4%) patients (median age, 77.3 years [5th to 95th centile range: 53.5 to 89 5 years]) and follow-up was complete in 94.8%. At implant. dual-chamber systems were implanted in 443 (55.1%). single-chamber ventricular systems in 321 (40.0%), and single-chamber-atrial systems in 39 (4.9%). Observed survival after implantation was significantly worse than expected (P<0.001). Independent predictors of increased mortality were: age at implant (risk ratio [RR] 1.06: 95% confidence interval [CI] 1.01 to 1.12). VVI pacing mode (RR 1.64; 95% CI 1.34 to 1.93), cardiomyopathy (RR 5.86; 95% CI 4.86 to 6.86), male gender (RR 1.27; 95% CI 1.22 to 1 32) and valvular heart disease (RR 2.01: 95% CI 1.98 to 2.04). CONCLUSIONS: At the end of follow-up, mortality was much higher than expected. In this typical pacemaker population. age at implant and VVI pacing mode were independently associated with increased mortality with accompanying heart disease having the greatest individual impact.

Aged↗
PubMed2000

Prospective randomized trials on pacing mode: what have we learned?

Retrospective studies and observational clinical data on pacemaker mode selection indicate that physiologic pacing is associated with better clinical outcomes and reduced mortality when compared with single-chamber ventricular pacing. Methodologic flaws in such studies, especially in respect of selection bias, have cast doubt upon the validity of the results and have mandated the performance of randomized, prospective studies of pacemaker-mode prescription. Evidence available to date suggests that atrial-based pacing may confer improved quality of life and a reduction in the incidence of chronic atrial fibrillation and thromboembolic events in sinus node disease. Physiologic pacing modes have, to date, not demonstrated benefit with congestive heart failure or patient longevity. The results of ongoing, large prospective trials of mode prescription in patients with AV block and sinus node disease are needed before any change from current guidelines can be recommended.

Aged↗
PubMed1998

Single chamber atrial pacing: an underused and cost-effective pacing modality in sinus node disease.

OBJECTIVE: To determine the safety and cost effectiveness of single chamber atrial pacing in patients with sinus node disease. DESIGN: Retrospective follow up study. SETTING: Tertiary referral centre. PATIENTS: 81 patients with single chamber atrial pacemakers implanted between 1992 and 1996. MAIN OUTCOME MEASURES: The development of high grade atrioventricular block resulting in a further pacemaker procedure. The cost savings of changing our current pacing practice to conform with British Pacing and Electrophysiology Group guidelines. RESULTS: During the follow up period, four patients (5.8%) required a further procedure to upgrade their atrial pacemaker to a dual chamber system owing to the development of high grade atrioventricular block. In 1995 and 1996, 343 pacemakers were implanted in patients with sinus node disease; 19 (5.5%) received single chamber atrial pacemakers and 271 (79%) dual chamber pacemakers. If the current pacing practice was changed so that all patients received single chamber atrial pacemakers, with revision for symptomatic atrioventricular block, savings in excess of 206,000 Pounds would have been made in the two year period. CONCLUSIONS: Atrial pacing in patients with sinus node disease is underused. The need for patients to undergo further procedures owing to the development of atrioventricular block is small and significant cost savings could be made by changing pacemaker practice.

Adult↗
PubMed1997

The impact of a dedicated "syncope and falls" clinic on pacing practice in northeastern England.

This study examined whether the increased demand for pacemaker implants for carotid sinus syndrome (CSS) at the Regional Pacing Service in northeastern England was related to the establishment of a dedicated "syncope and falls" clinic or to the publication of NASPE and BPEG guidelines for pacing symptomatic bradycardia. To this end, pacemaker rates for various indications at this institution were compared with those of a comparable region (Liverpool), as well as with BPEG's national pacemaker database. Findings indicate a distinct impact of the Newcastle syncope and falls clinic on recognition and pacemaker treatment of CSS.

Accidental Falls↗
PubMed1996

Trends in pacemaker mode prescription 1984-1994: a single centre study of 3710 patients.

OBJECTIVE: To evaluate trends in pacemaker mode prescription from 1984 to 1994 with particular reference to the changes in pacemaker mode prescription for patients aged 80 years and older at implant. DESIGN: Prospective evaluation of indications for pacing and pacemaker mode prescription in all patients undergoing new pacemaker implantation from 1992 to 1994. Comparison with retrospectively obtained data for patients paced from 1984 to 1991. SETTING: Tertiary referral cardiothoracic centre. PATIENTS: Group 1: 2622 patients paced at one centre and entered into the national pacing database from 1984 to 1991. Group 2: 1088 consecutive patients paced from 1992 to 1994. RESULTS: Use of atrial (AAI) and dual chamber (DDD) pacemakers increased progressively in patients of all ages from 1984 to 1994. There was an increase in the proportion of patients aged 80 years and older from 25.4% (group 1) to 40.5% (group 2). Patients of all ages in group 2 were more likely to receive DDD units for atrioventricular block (odds ratio (95% confidence interval) (CI) 9.0 (7.0 to 11.5)) and AAI or DDD units for sinus node disease (odds ratio (95% CI) 11.0 (7.7 to 15.8)) than those in group 1. Elderly patients (age > or = 80 at implant) with atrioventricular block or sinus node disease and a suitable atrial rhythm were less likely to receive DDD or AAI pacemakers than younger patients in both groups. CONCLUSIONS: Use of atrial and dual chamber pacing modes has increased substantially in patients of all ages over the last decade. Although elderly patients represent an increasing proportion of the paced population, they remain less likely to receive atrial or dual chamber pacemakers than younger patients.

Age Factors↗
PubMed1995

Early complications of permanent pacemaker implantation: no difference between dual and single chamber systems.

OBJECTIVE: To evaluate the incidence of intraoperative and early postoperative complications (up to two months after implant) of endocardial permanent pacemaker insertion in all patients under-going a first implant at a referral centre. METHODS: Prospective evaluation of all endocardial pacemaker implantation procedures performed from April 1992 to January 1994 carried out by completion of standard audit form at implant. Patients' demographic data, medical history, details of pacemaker hardware used, and any complications were noted. Follow up information was also collected prospectively onto standard forms at pacemaker outpatient clinic. SETTING: United Kingdom tertiary referral cardiothoracic centre. PATIENTS: 1088 consecutive patients underwent implantation of their first endocardial permanent pacemaker from April 1992 to January 1994. Implant and follow up data were available for 1059 (97.3%) patients at analysis. The median (range) age was 77 years (16-99); 51.2 % were male. RESULTS: Dual chamber units were implanted in 54.1% of patients, single chamber atrial in 5.2%, and ventricular in 40.7%. A temporary pacing lead was present at implant in 22.9% of patients. Most (93.6%) implants were performed via the subclavian vein. Immediate complications were rare: eight (0.8%) patients developed pneumothorax requiring medical treatment and 11 (1.0%) an insignificant pneumothorax. There was no significant difference in the pneumothorax rate for dual chamber (DDD) compared with single chamber systems. Arterial puncture without sequelae was documented in 2.7% of attempts at subclavian vein cannulation. A total of 35 patients (3.3%) required reoperation; the reoperation rate for dual chamber (3.5%) was similar to that for single chamber (3.1%) systems. Electrode displacement (n = 15, 1.4%) was the most common reason for reoperation. Atrial lead displacement (n = 10, 1.6% of atrial leads) was significantly more common than ventricular lead displacement (n = 5, 0.5% of ventricular leads, P = 0.047). There was no difference in electrode displacement rates for dual (1.6%) compared with single (1.2%) chamber systems. Pacemaker pocket infection led to reoperation in 10 patients (six dual, four single chamber, P = not significant) and was significantly more common in patients who had a temporary pacing lead in place at implant (2.9%) than in those who did not (0.4%, P = 0.0014). Five patients (0.5%) required reoperation for generator erosion (two dual, three single chamber, P = not significant). and a further five for drainage of haematoma or a serous fluid collection (three dual, two single chamber, P = not significant). Complications that did not require reoperation were also rare. Undersensing occurred in 10 patients (0.9%). Atrial undersensing (n = 8) was significantly more common than ventricular undersensing (n = 2, P = 0.017). All patients were successfully treated by reprogramming of sensitivity. Superficial wound infection was treated successfully with antibiotics in nine patients (six dual, three single chamber, P = not significant). Three patients with DDD generators developed sustained atrial fibrillation: two required reprogramming to VVI mode and one required cardioversion. CONCLUSIONS: Permanent pacing in a large tertiary referral centre with experienced operators carries a low risk. Infection rates are low, < 1% overall but significantly higher in patients who undergo temporary pacing before implantation. Lead displacement and undersensing are more likely to occur with atrial than ventricular leads. The overall complication rate for dual chamber pacing, however, is no higher than for single chamber pacing.

Adolescent↗
PubMed1994

Stability of the DDD pacing mode in patients 80 years of age and older.

We reviewed the records of 119 consecutive patients aged 80 years or older (mean age 84 +/- 3.7 years) in whom a dual chamber pacemaker was implanted between 1984 and 1991. Follow-up data was available up to February 1993. Immediate postimplantation complications were rare. Nine patients were lost to follow-up, all within 6 months of implantation. An additional seven patients died within 6 months of implantation. Long-term follow up for at least 6 months from implantation was available for 103 of the 119 patients (87%). Of these 89 (86%) remained in functioning DDD mode for a mean of 22 +/- 15 months from implantation. Nine patients were reprogrammed to VVI mode, six due to atrial fibrillation and three due to failure of atrial sensing or pacing. One patient was programmed DVI for failure of atrial sensing; 94 of 112 patients (84%) whose status was definitely known in February 1993 remained in functioning DDD mode until death or last follow-up. Cumulative survival in DDD mode was 78% at 30 months. We conclude that DDD pacing is stable in the great majority of patients in their ninth and tenth decades who present with rhythms amenable to dual chamber pacing and who have no history of sustained atrial fibrillation.

Aged↗
PubMed1993

Accelerometer-based adaptive-rate pacing: a multicenter study. European EXCEL Study Group.

UNLABELLED: A new adaptive rate pacemaker, using an accelerometer to detect body motion as an indicator of metabolic demand, was evaluated in 13 centers located in five countries. During the study, 55 patients with a broad range of indications were implanted with the EXCEL VR single chamber pacemaker. One month evaluations were completed on a subgroup of 37 patients. The pacemaker response was optimized before discharge using a simple walking test. An "exercise test" recording feature in the programmer eliminated the need for ECG monitoring. At nominal settings, the mean (+/- SD) pacing rate increased 29 +/- 9 ppm while walking slowly and 44 +/- 11 ppm (n = 33) during a brisk walk. This information was used to optimize the parameter settings. Without further changes to the programmed settings the patients were subsequently tested 2-4 weeks postimplant with a symptom-limited treadmill test using the chronotropic assessment exercise protocol (CAEP). Mean pacing rate increased from 74.5 +/- 2.5 ppm (n = 24) at rest to 118.6 +/- 12.2 ppm (n = 21) at 3 mph/6% grade to 143.5 +/- 3.5 ppm (n = 2) at 3.8 mph/8% grade. CONCLUSION: The individual responses were proportional to the physical exertion imposed on the patients. Pacing rates were considered to be appropriate using the chronotropic response zone as a criterion for appropriate rate modulation. A simple walking test utilizing the exercise test facility, results in appropriate optimization of the pulse generator to the individual patient.

Acceleration↗
PubMed1992

Comparative evaluation of rate modulation in new generation evoked QT and activity sensing pacemakers.

Two new generation rate adaptive pacemakers, the Rhythmyx (Vitatron) using the evoked QT interval and the Legend (Medtronic) using vibration as indicators of metabolic demand, were compared for rate adaptive characteristics during different forms of exercise. While both showed improvements over previous generation pacemakers, they still show deficiencies in some aspects of rate modulation. Rhythmyx was slow to respond to changes in metabolic need and showed an "over-shoot" with increasing pacing rate on cessation of exercise. Legend was quick to adapt rate at beginning and end of exercise but showed a plateaus of rate modulation during the period of slowly increasing workload. Legend also showed only modest rate adaptation to changes in treadmill gradient and to bicycle ergometer exercise. Further developments in pacemaker technology are required if physiological rate adaptation to exercise is required.

Aged↗
PubMed1992

Growth, body composition, and plasma androgen concentration of male broiler chickens subjected to different regimens of photoperiod and light intensity.

Day-old male Hubbard broilers (960) were assigned to one of four treatments (two pens of 120 birds per treatment) to evaluate the effects of high (150 lx) versus low (5 lx) light intensity and constant 23 h light (L):1 h dark (D) versus increasing (6L:18D increasing 4 h/wk to 23L:1D) photoperiod in a 2 x 2 factorial arrangement of treatments. Birds were raised to 8 wk on a typical commercial four-diet program. Low-intensity birds were heavier than high-intensity birds from 2 to 8 wk (3.25% heavier at 8 wk). Birds raised under constant photoperiod were heavier than birds raised under increasing photoperiod from 2 to 5 wk and at 7 wk of age (1.71% heavier at 7 wk). High-intensity bird carcasses had lower percentage body fat, weight of fat, and higher percentage body protein at 8 wk compared with low-intensity bird carcasses (7.77, 10.76, and 1.77%, respectively). High-intensity birds had smaller abdominal fat pads (weight and percentage of body weight) at 8 wk compared with low-intensity birds (15.46 and 12.17%, respectively). Photoperiod did not affect body composition. Birds treated with increasing photoperiod had larger testes (weight and percentage of body weight) at 8 wk compared with birds under the constant photoperiod (29.36 and 30.51%, respectively). Birds treated under increasing photoperiod had higher plasma androgen concentrations at 7 wk compared with birds under constant photoperiod (testosterone, .270 versus .188 ng/mL; androstenedione, .632 versus .494 ng/mL).(ABSTRACT TRUNCATED AT 250 WORDS)

Androgens↗
PubMed1992

Effect of feed allowance during rearing and breeding on female broiler breeders. 2. Ovarian morphology and production.

The influence of feed allowance during rearing (4 to 18 wk) and breeding (18 to 62 wk) on ovarian morphology and egg production was examined. During rearing, beginning at 4 wk of age, 400 Indian River pullets that had been full-fed from 1 day of age either continued to be full-fed (F, n = 200) or were feed restricted (R, n = 200), following commercial practice. At 18 wk of age, 100 birds (within +15% of the mean BW) in each of F and R rearing groups were further assigned to be full-fed (n = 50) or feed restricted (n = 50) during breeding. Thus, based on feed allowance during rearing and breeding, four treatment groups were formed (FF, FR, RF, and RR). Feed restriction during rearing significantly delayed oviduct development and age at sexual maturity (age at first egg). Compared with feed restriction during both rearing and breeding (RR), ad libitum feeding beginning at 18 wk of age (RF) significantly increased the weight of the ovary and the number of large follicles at sexual maturity but did not significantly affect the age at sexual maturity. Feed restriction during rearing, breeding, or both significantly reduced the incidence of erratic ovipositions, defective eggs, and multiple ovulations. The incidence of erratic ovipositions was positively correlated (r = .692, P less than or equal to .001) with the laying of soft-shelled and shell-less eggs and negatively correlated (r = -.508, P less than or equal to .001) with the production of settable eggs to 62 wk of age. Compared with ad libitum feeding, controlled feeding during breeding significantly improved both settable and total egg production. Among the four feeding regimens, Treatment RR resulted in the highest fertility and hatchability.

Aging↗
PubMed1988

Beta-blockade by sotalol in early myocardial infarction decreases ventricular arrhythmias without increasing left ventricular volume.

Although early beta-blockade in acute myocardial infarction (AMI) may have potential benefits owing to an anti-arrhythmic effect and limitation of infarct size, the haemodynamic effects are not well characterised. Accordingly, we studied the effects of intravenous beta-blockade by sotalol in AMI, commencing a mean of 6 hours after the onset of chest pain, with particular reference to systemic haemodynamic changes and left ventricular (LV) volumes. Thirty patients were randomised to a control group or to sotalol therapy starting with 40 mg and increasing to 120 mg, followed by the maximal dose tolerated every 6 hours for 72 hours. Sotalol reduced heart rate and mean blood pressure without elevating pulmonary wedge pressure or increasing enzymatic infarct size. Sotalol also decreased the incidence of ventricular tachycardia (P less than 0.001). An important new finding was that there was no increase in the LV volume measured by radionuclide techniques. Therefore intravenous sotalol safely achieved its beneficial effects without causing LV dilatation.

Adult↗