P J Weston

University of Liverpool, Liverpool, ENG, United Kingdom

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Publications (21)158.18 Total impact

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    ABSTRACT: Nocturnal hypoglycaemia (NH) remains a problem in type 1 diabetes and spontaneous asymptomatic NH may be a risk factor for sudden death ('Dead in Bed' syndrome). To explore whether any predictive relationship exists between the average or time-specific glycaemia and the occurrence of NH. Twenty-five healthy patients with type 1 diabetes underwent two separate overnight periods of continuous glucose monitoring (CGM) using a MMT-7002 Medtronic MiniMed System. There was a 6-week interval before the second monitoring period. CGM glucose levels recorded between 23:00 and 08:00 h defined the nocturnal period and recorded glucose monitoring levels <3.5 mmol/l for at least 10 min during this time-defined NH. A CGM recording at 23:00 h and 08:00 h were taken as the bedtime and fasting glucose levels, respectively. The mean +/- SD age was 37 +/- 7 years and duration of diabetes 13 +/- 7 years; 16 (64%) were on long-acting analogue insulin. Forty-nine CGM data sets were recorded. Fourteen episodes of NH occurred in 12 patients (Group 1), 13 patients (Group 2) had no NH. Group 1 (NH) had a lower mean bedtime glucose recorded compared with Group 2 (7.7 +/- 4.3 vs. 11.4 +/- 4.0 mmol/l, P = 0.0035). Fasting glucose level was also lower in Group 1 following the occurrence of NH (P = 0.014). There was no difference in the type of insulin used between the two groups. Our data show that in normal day to day settings, NH is common and that the bedtime glucose level is a significant predictive factor.
    QJM: monthly journal of the Association of Physicians 08/2009; 102(9):603-7. · 2.36 Impact Factor
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    ABSTRACT: Sudden nocturnal death in type 1 diabetes ('dead in bed' syndrome) is thought to be due to ECG QT prolongation with subsequent ventricular tachyarrhythmia in response to nocturnal hypoglycaemia. We investigated this theoretical mechanism using continuous ECG and continuous glucose monitoring in a group of patients with type 1 diabetes. Twenty-five patients with type 1 diabetes (age 20-50 years) underwent two separate 24 h ECG and continuous glucose monitoring periods. Patients were fully ambulant and carried out normal daily activities. There were 13 episodes (26% of recordings) of nocturnal hypoglycaemia, eight of <2.2 mmol/l and five of 2.2-3.4 mmol/l. Corrected QT interval (QTc) was longer during nocturnal hypoglycaemia compared with normoglycaemic control periods (445 +/- 40 vs 415 +/- 23 ms; p = 0.037). Cardiac rate and rhythm disturbances (excluding sinus tachycardia) were seen in eight of the 13 nocturnal hypoglycaemia episodes (62%). These were sinus bradycardia (<40 beats/min; three episodes), ventricular ectopics (three episodes), atrial ectopics (one) and P wave abnormalities (one). This study demonstrates QTc prolongation and cardiac rate/rhythm disturbances in response to episodes of nocturnal hypoglycaemia in ambulant patients with type 1 diabetes. This may support an arrhythmic basis for the 'dead in bed' syndrome.
    Diabetologia 10/2008; 52(1):42-5. · 6.49 Impact Factor
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    ABSTRACT: Increased prevalence of hypertension and cardiovascular mortality have been reported in hypopituitary patients who had been appropriately replaced with conventional pituitary hormones except GH. Growth hormone replacement (GHR) results in improvement of surrogate markers of cardiovascular function. Data on effects of GHR on blood pressure (BP) in adult growth hormone deficiency (AGHD), however, remain contradictory. There are as yet no reports on BP circadian rhythms in untreated or treated AGHD. Therefore, in a 12-month follow-up study, we evaluated the effects of GHR on ambulatory blood pressure (ABP) in AGHD patients. A prospective, open treatment design study to determine the effects of GHR on ABP and heart rate in AGHD patients. GH was commenced at a daily dose of 0.5 IU, and titrated up by increments of 0.25 IU at 4-weekly intervals to achieve and maintain IGF-I standard deviation score (IGF-I SD) between the median and upper end of the age-related reference range. Twenty-two, post-pituitary surgery, severe AGHD patients (11 men), defined as peak GH response < 9 mU/l to provocative testing were recruited. The mean age +/- SEM was 48.8 +/- 2.5 years. Twenty-one patients required additional pituitary replacement hormones following pituitary surgery and were on optimal doses at recruitment. Twenty-four-hour ABP and heart rate (HR), body mass index (BMI), waist hip ratio (WHR) and total body water (TBW) were measured before and after 12 months on GHR. Cosinor analysis was used to analyse BP and HR circadian rhythm parameter estimates. Target IGF-I SD was achieved within 3 months of commencement of GHR in all patients (-3.5 +/- 0.4 at baseline vs. 0.8 +/- 0.2 at 3 months, P < 0.001) and remained within range at 12 months (1.1 +/- 0.2, P < 0.001 compared to baseline). A significant increase in TBW (45.8 +/- 1.2 vs. 47.8 +/- 1.5 kg, P < 0.05) but no significant change in BMI (30.7 +/- 2.2 vs. 31.8 +/- 2.7, P = NS) or WHR (0.95 +/- 0.02 vs. 0.93 +/- 0.02, P = NS) was observed after 12 months on GHR. The 24-h mean systolic ABP (SBP; 126.2 +/- 2.8 vs. 120.1 +/- 2.7 mmHg, P < 0.001) and diastolic ABP (DBP; 78.2 +/- 1.6 vs. 71.4 +/- 1.8 mmHg, P < 0.001) significantly decreased following GHR with a parallel increase in 24-h mean HR (69.6 +/- 2.5 vs. 73.8 +/- 2.5 beats/min; P < 0.001). A significant nocturnal decrease in SBP and DBP was observed both before (SBP; daytime, 129.1 +/- 2.8 vs. night time, 115.9 +/- 3.0 mmHg, P < 0.001 and DBP; daytime, 80.7 +/- 1.6 vs. night time, 69.2 +/- 1.8 mmHg, P < 0.001) and following GHR (SBP; daytime, 122.8 +/- 2.6 vs. night time, 110.0 +/- 3.6 mmHg, P < 0.001 and DBP; daytime, 73.9 +/- 1.8 vs. night time, 62.0 +/- 2.3 mmHg, P < 0.001). Individual and population-mean cosinor analysis demonstrated significant circadian rhythms for SBP, DBP and HR before and after 12 months on GHR (P < 0.001), suggesting that SBP, DBP and HR circadian rhythms were not altered by GHR. There was, however, a significant reduction in SBP (124.2 +/- 2.8 vs. 118.4 +/- 2.8 mmHg, P < 0.001) and DBP (77.0 +/- 1.6 vs. 70.2 +/- 1.8 mmHg, P < 0.001) MESOR with an increase in HR MESOR (68.9 +/- 2.5 vs. 72.2 +/- 2.4 beats/min, P < 0.01) following GHR. Systolic and diastolic BP and HR circadian rhythms are preserved in AGHD following 12 months of GHR. However, there is a significant decrease in 24-h mean SBP and DBP and increase in 24-h mean HR after 12 months on GHR. We postulate that this decrease in 24-h mean SBP and DBP may result in a reduction of cardiovascular morbidity and mortality and may explain the beneficial effects of GHR on cardiovascular system previously reported in AGHD patients.
    Clinical Endocrinology 04/2002; 56(4):431-7. · 3.40 Impact Factor
  • Growth Hormone & IGF Research 06/2001; 11. · 2.26 Impact Factor
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    ABSTRACT: To document the prescribed usage of beta blockers in patients with and without diabetes mellitus discharged from hospital following a first myocardial infarction. All patients with diabetes and a group of patients matched for age and sex without diabetes, admitted with a documented first myocardial infarction during the period 1995-1999 at the Royal Liverpool University Hospital, Liverpool, UK were audited. Data were available on 201 patients with diabetes and 199 patients without diabetes. No significant differences existed between the diabetic and non-diabetic groups for age and sex. Twenty-three per cent of patients with diabetes were prescribed a beta blocker compared to 52% of non-diabetic patients (P < 0.01). Patients with diabetes had a higher frequency of perceived contraindications than patients without diabetes (36 vs. 27%, P < 0.001). Thirty-five per cent of patients with diabetes and 18% of non-diabetic patients had no contraindication to the use of beta blocker but were not prescribed one (P < 0.001). Although beta blockers can provide useful benefits in patients with diabetes following a myocardial infarction, this study suggests that a significant proportion of patients with diabetes and without a contraindication to treatment are still not receiving beta blockers after myocardial infarction.
    Diabetic Medicine 02/2001; 18(2):159-61. · 3.24 Impact Factor
  • P J Weston, G V Gill
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    ABSTRACT: Sudden nocturnal death in young persons with Type 1 diabetes mellitus has been recently described, and is known as the 'dead in bed' syndrome. Its aetiology is unknown, and we have therefore explored the details of all papers recording the syndrome, to formulate a hypothesis of causation. Literature review of 'dead in bed' reports as well as of nocturnal hypoglycaemia, and autonomic dysfunction in relation to baroreceptor-cardiac reflex sensitivity. Clinical reports of 'dead in bed' cases strongly suggest that nocturnal hypoglycaemia is a likely precipitant, but that the death is sudden and probably arrhythmic. Ventricular dysrhythmias may occur in the context of early autonomic neuropathy, with relative sympathetic overactivity, in young Type 1 diabetic persons. We conclude that the 'dead in bed' syndrome probably occurs in Type 1 diabetic persons with early autonomic neuropathy, resulting in relative sympathetic overactivity. In such persons, risks of ventricular dysrhythmias will be compounded by nocturnal hypoglycaemia, which may be associated with an increase in the electrocardiographic Q-T interval, and Q-T dispersion. This could lead to the observed sudden death in undisturbed beds. Further research in this area is urgently needed, in particular into the possible protective use of drugs that modulate the autonomic nervous system.
    Diabetic Medicine 09/1999; 16(8):626-31. · 3.24 Impact Factor
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    ABSTRACT: To examine the relationship between age, blood pressure and cardiac baroreceptor sensitivity derived from spectral analysis, the Valsalva manoeuvre and impulse response function. We studied 70 healthy normotensive volunteers who were free from disease and not taking medication with cardiovascular or autonomic effects. We measured beat-to-beat arterial blood pressure and used standard surface electrocardiography to record pulse interval under standardized conditions with subjects resting supine as well as during three Valsalva manoeuvres. We performed single, multiple and stepwise regression of patient characteristics against cardiac baroreceptor sensitivity results. There is a non-linear decline in cardiac baroreceptor sensitivity with advancing age, increasing systolic blood pressure and heart rate values (except for the Valsalva-derived result), but little further decline after the fourth decade. Only age significantly influenced values derived using the Valsalva manoeuvre and impulse response analysis. Using spectral analysis, age, systolic and diastolic blood pressure and heart rate influenced cardiac baroreceptor sensitivity, age contributing to 50% of the variability. Age also influenced the relationship between pulse interval and blood pressure, possibly indicating more non-baroreceptor-mediated changes with advancing age. Although age is the dominant factor influencing cardiac baroreceptor sensitivity in this normotensive population, there is little change in mean values after 40 years of age. The differences in the relationship between pulse interval and blood pressure with advancing age have implications for the calculation of cardiac baroreceptor sensitivity using spectral analysis.
    Age and Ageing 08/1999; 28(4):347-53. · 3.82 Impact Factor
  • Diabetes Obesity and Metabolism 06/1999; 1(3):151-8. · 5.18 Impact Factor
  • Diabetes Obesity and Metabolism 04/1999; 1(3):151 - 158. · 5.18 Impact Factor
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    ABSTRACT: (1) Autonomic dysfunction is a well recognised complication of diabetes mellitus and early detection may allow therapeutic manoeuvres to reduce the associated mortality and morbidity. We sought to identify early cardiovascular autonomic neuropathy using spectral analysis of heart rate and systolic blood pressure variability. (2) Thirty patients with Type 1 (insulin-dependent) diabetes mellitus (DM) and 30 matched control subjects were studied. In addition to standard tests of autonomic function, heart rate and systolic blood pressure variability were assessed using power spectral analysis. From the frequency domain analysis of systolic blood pressure and R-R interval, the overall gain of baroreflex mechanisms was assessed. (3) Standard tests of autonomic function were normal in both groups. Total spectral power of R-R interval was reduced in the Type 1 DM group for low-frequency (473 +/- 63 vs. 747 +/- 78 ms2, mean +/- S.E.M., P = 0.002) and high-frequency bands (125 +/- 13 vs. 459+/-90 ms2, P < 0.0001). Systolic blood pressure low-frequency power was increased in the diabetic group (9.3 +/- 1.2 vs. 6.6+/-0.7 mmHg2, P < 0.05). The low frequency/high frequency ratio for heart rate variability was significantly higher in the Type 1 DM patients (4.6+/-0.5 vs. 2.9+/-0.5, P = 0.002), implying a relative sympathetic predominance. When absolute powers were expressed in normalised units, these differences persisted. There were significant reductions in baroreceptor-cardiac reflex sensitivity in Type 1 DM patients compared to controls while supine (9.7+/-0.7 vs. 18.5 +/- 1.7 ms/mmHg, P < 0.0001) and standing (2.9+/-0.9 vs. 7.18+/-1.9 ms/mmHg, P < 0.001). (4) Spectral analysis of cardiovascular variability detects autonomic dysfunction more frequently in Type 1 DM patients than conventional tests, and is suggestive of an abnormality of parasympathetic function. The abnormality of baroreceptor-cardiac reflex sensitivity could be explained by this impairment of parasympathetic function and this may predispose to the development of hypertension and increase the risk of sudden cardiac death. Using spectral analysis methods may allow detection of early diabetic cardiac autonomic neuropathy and allow therapeutic intervention to slow the progression.
    Diabetes Research and Clinical Practice 01/1999; 42(3):141-8. · 2.74 Impact Factor
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    ABSTRACT: Autonomic neuropathy is a common complication of diabetes mellitus and is associated with significant morbidity and possibly an increase in mortality. Despite this, however, autonomic dysfunction is not usually sought in the routine assessment of diabetic patients. We report the development and testing of a small, portable and reliable device that allows the routine testing of cardiac autonomic function in the outpatient setting with minimal inconvenience to the patient. This should facilitate the accurate assessment both of patients with symptoms suggestive of autonomic dysfunction and of autonomic function in research.
    Diabetic Medicine 09/1998; 15(8):700-4. · 3.24 Impact Factor
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    ABSTRACT: Baroreceptor sensitivity (BRS) is increasingly used as a prognostic indicator in cardiovascular disease. Traditionally it has been measured using invasive techniques with pharmacological manipulation of blood pressure (BP). With the advent of newer methods to measure pulse interval and beat-to-beat changes in BP it is now possible, using sophisticated mathematical modelling techniques, to calculate cardiac BRS non-invasively. However, there are virtually no data on the reproducibility of these newer techniques and what factors may affect the repeatability of these measurements. We studied 39 subjects, aged 22-82 years, with a supine systolic BP range 97-160 mmHg and a diastolic BP range 57-94 mmHg on two occasions between 1 week and 6 months apart. Cardiac BRS was measured by power spectral analysis using Fast Fourier Transformation (FFT), sequence analysis (using up, down and combined sequences) and from phase IV of the Valsalva manoeuvre. There was no significant difference between visits for any of the methods for measuring cardiac BRS. Mean BRS values were similar for FFT (16.7 +/- 11.2 ms/mmHg) and sequence analysis (15.8 +/- 11.4 ms/mmHg); however, results using phase IV of the Valsalva manoeuvre were significantly lower (8.1 +/- 2.9 ms/mmHg, p < 0.0001). The coefficient of variation for the five measures of cardiac BRS varied from 16.8% for Valsalva-derived values to 26.1% for 'down' sequence analysis. However, in ten subjects BRS could not be calculated from the Valsalva manoeuvre. None of the independent variables tested (including age, BP levels and time between testing) significantly influenced the degree of repeatability. In summary, there appears to be little difference between these non-invasive methods in their degree of reproducibility. These techniques would seem suitable for longitudinal studies of changes in cardiac BRS and overcome many of the problems associated with the invasive pharmacological methods.
    Clinical Autonomic Research 12/1997; 7(6):279-84. · 1.48 Impact Factor
  • P J Weston, G V Gill
    The Lancet 11/1997; 350(9083):1032-3. · 39.21 Impact Factor
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    ABSTRACT: To study the possible association or QT dispersion and mean QTc intervals, as measured from standard 12 lead electrocardiograms, with baroreceptor-cardiac reflex sensitivity (BRS) in insulin dependent diabetic patients. Comparative study of non-invasive assessment of BRS, QT interval, and QT dispersion. Large teaching hospital. 31 young asymptomatic, normotensive, insulin dependent diabetic patients, aged 20-55 years with normal clinical autonomic function. QT intervals and QT dispersion were measured by a single observer blinded to other data about the patients. BRS was measured after activating the baroreflex with a Valsalva manoeuvre, and the rate in change of R-R interval to increasing systolic pressure during phase 4 was measured; in addition sequence analysis of resting systolic blood pressure and heart rate was performed during standing. The alpha coefficient--an index of the overall gain of the baroreflex mechanisms--was estimated from spectral analysis data of systolic blood pressure and pulse interval variability. Mean (SD) QTc interval was 406 (23) ms, QT dispersion was 44 (13) ms. There was no association between QT dispersion and any measurement of BRS. There was a negative correlation between mean QTc intervals and sequence analysis BRS (r = -0.355, P = 0.049), but no association with Valsalva BRS. The alpha coefficient, showed a significant negative correlation with mean QTc (r = -0.42, P = 0.008). Abnormal BRS may be reflected in the heart by global prolongation of ventricular repolarisation, but not by dispersion of ventricular repolarisation. This may, in part, explain the increase in sudden cardiac death seen in IDDM patients.
    Heart (British Cardiac Society) 08/1997; 78(1):56-60. · 5.01 Impact Factor
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    ABSTRACT: Sudden death at night is known to occur in young patients with insulin-dependent (Type 1) diabetes mellitus (IDDM) but the aetiology is uncertain. A cardiac arrhythmia has been postulated, but there has been little evidence to support this. We present the case of a 31-year-old man with IDDM of 17 years duration, who died suddenly while asleep. Over preceding months, he had had strict glycaemic control (HbA1 8.9%), normal 24 h blood pressure (mean 131 +/- 2.1/76 +/- 2.2 mmHg), no evidence of microangiopathy or endothelial dysfunction and normal standard clinical tests of autonomic function. An electrocardiogram was similarly unremarkable, with a QTc interval of 0.414 s, and an echocardiogram had demonstrated normal left ventricular mass index (96.4 g m-2). However, there was no nocturnal dip in heart rate (daytime 74 +/- 2.7, and nocturnal 68 +/- 1.6 beats min-1), and he had grossly impaired baroreflex sensitivity during Phase 4 of the valsalva manoeuvre (0.5 ms mmHg-1), with power spectral analysis studies suggesting an abnormality of parasympathetic function. The coroner's autopsy demonstrated no structural abnormalities. We hypothesize that abnormal baroreflex sensitivity could either predict a risk of or account for some of the unexplained deaths in IDDM, in that relative overactivity of the sympathetic nervous system could cause ventricular arrhythmias.
    Diabetic Medicine 02/1997; 14(1):82-5. · 3.24 Impact Factor
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    ABSTRACT: Autonomic dysfunction in insulin-dependent diabetic (IDDM) patients has been associated with abnormalities of left ventricular function and an increased risk of sudden death. A group of 30 patients with IDDM and 30 age, sex and blood pressure matched control subjects underwent traditional tests of autonomic function. In addition, baroreceptor-cardiac reflex sensitivity (BRS) was assessed using time domain (sequence) analysis of systolic blood pressure and pulse interval data recorded non-invasively using the Finapres beat-to-beat blood pressure recording system. 'Up BRS' sequences-increases in systolic blood pressure associated with lengthening of R-R interval, and 'down BRS' sequences-decreases in systolic blood pressure associated with shortening of R-R interval were identified and BRS calculated from the regression of systolic blood pressure on R-R interval for all sequences. We also assessed heart rate variability using power spectral analysis and, after expressing components of the spectrum in normalised units, assessed sympathovagal balance from the ratio of low to high frequency powers. IDDM subjects underwent 2-D echocardiography to assess left ventricular mass index. Standard tests of autonomic function revealed no differences between IDDM patients and control subjects, but dramatic reductions in baroreceptor-cardiac reflex sensitivity were detected in IDDM patients. 'Up BRS' when supine was 11.2 +/- 1.5 ms/mmHg (mean +/- SEM) compared with 20.4 +/- 1.95 in control subjects (p < 0.003) and when standing was 4.1 +/- 1.9 vs 7.6 +/- 2.7 ms/mmHg (p < 0.001). Down BRS when supine was 11.5 +/- 1.2 vs 22 +/- 2.6 (p < 0.001) and standing was 4.4 +/- 1.9 vs 7.3 +/- 2.5 ms/mmHg (p < 0.003). There were significant relations between impairment of the baroreflex and duration of diabetes (p < 0.001) and poor glycaemic control (p < 0.001). From a fast Fourier transformation of supine heart rate data and using a band width of 0.05-0.15 Hz as low-frequency and 0.2-0.35 Hz as high frequency total spectral power of R-R interval variability was significantly reduced in the IDDM group for both low-frequency (473 +/- 62.8 vs 746.6 +/- 77.6 ms2 p = 0.002) and high frequency bands 125.2 +/- 12.9 vs 459.3 +/- 89.8 ms2 p < 0.0001. When the absolute powers were expressed in normalised units the ratio of low frequency to high frequency power (a measure of sympathovagal balance) was significantly increased in the IDDM group (2.9 +/- 0.53 vs 4.6 +/- 0.55, p < 0.002 supine: 3.8 +/- 0.49 vs 6.6 +/- 0.55, p < 0.001 standing). Thus, time domain analysis of baroreceptor-cardiac reflex sensitivity detects autonomic dysfunction more frequently in IDDM patients than conventional tests. Impaired BRS is associated with an increased left ventricular mass index and this abnormality may have a role in the increased incidence of sudden death seen in young IDDM patients.
    Diabetologia 11/1996; 39(11):1385-91. · 6.49 Impact Factor
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    ABSTRACT: 1. Autonomic neuropathy is a common complication of diabetes mellitus and is a major risk factor for sudden death. 2. A group of 30 patients with insulin-dependent diabetes mellitus and 30 age-, sex- and blood pressure-matched control subjects underwent traditional tests of autonomic function. Resting supine R-R interval and systolic blood pressure variability were assessed using spectral analysis methods. In addition, we assessed the baroreceptor-cardiac reflex from the linear relation of the change in R-R interval to the increasing systolic blood pressure measured non-invasively with the Finapres monitor during phase 4 of the Valsalva manoeuvre and from resting heart rate and systolic blood pressure power spectra. 3. Whereas standard tests of autonomic function revealed no differences between patients with insulin-dependent diabetes mellitus and control subjects, there was a significant reduction in power spectral density of heart rate variability around the high-frequency region (125.2 +/- 112.9 versus 459.3 +/- 189.8 ms2, mean +/- SD). Furthermore, reductions in baroreflex sensitivity calculated from the Valsalva manoeuvre were detected in diabetics compared with controls (3.3 +/- 1.6 versus 9.5 +/- 2.5 ms/mmHg, mean +/- SD, P < 0.00001). There were significant relations between impairment of the baroreflex and duration of diabetes (P < 0.001) and poor diabetic control (P < 0.05). 4. In summary, autonomic dysfunction occurs much more frequently in diabetic patients than conventional tests would suggest. Abnormal baroreceptor-cardiac reflex sensitivity in patients with insulin-dependent diabetes mellitus may in part be explained by abnormal parasympathetic function. This unrecognized abnormality may have a role in the increased incidence of sudden death seen in young diabetic subjects.
    Clinical Science 08/1996; 91(1):59-64. · 4.86 Impact Factor
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    ABSTRACT: This study investigated interobserver (two observers) and intrasubject (two measurements) reproducibility of QT dispersion from abnormal electrocardiograms in patients with previous myocardial infarction, and compared a user-interactive with an automatic measurement system. Standard 12-lead electrocardiograms, recorded at 25 mm.s-1, were randomly chosen from 70 patients following myocardial infarction. These were scanned into a personal computer, and specially designed software skeletonized and joined each image. The images were then available for user-interactive (mouse and computer screen), or automatic measurements using a specially designed algorithm. For all methods reproducibility of the RR interval was excellent (mean absolute errors 3-4 ms, relative errors 0.3-0.5%). Reproducibility of the mean QT interval was good; intrasubject error was 6 ms (relative error 1.4%), interobserver error was 7 ms (1.8%), and observers' vs automatic measurement errors were 10 and 11 ms (2.5, 2.8%). However QTc dispersion measurements had large errors for all methods; intrasubject error was 12 ms (17.3%), interobserver error was 15 ms (22.1%), and observers' vs automatic measurement were errors 30 and 28 ms (35.4, 31.9%). QT dispersion measurements rely on the most difficult to measure QT intervals, resulting in a problem of reproducibility. Any automatic system must not only recognize common T wave morphologies, but also these more difficult T waves, if it is to be useful for measuring QT dispersion. The poor reproducibility of QT dispersion limits its role as a useful clinical tool, particularly as a predictor of events.
    European Heart Journal 08/1996; 17(7):1035-9. · 14.72 Impact Factor
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    ABSTRACT: The aim of this study was to evaluate the reproducibility of the circadian blood pressure (BP) change in normal healthy volunteers. The subjects were 32 healthy, young, normotensive volunteers who underwent 24 h ambulatory BP monitoring on two occasions, at least 4 weeks apart. Data were analysed using standard definitions of day and night (i.e. 07.00-22.00 for daytime and 22.00-07.00 for night time), event diaries to identify individual's day and night time and a time independent method (cusum analysis). Intraindividual variations of BP were assessed using the coefficient of variation (CV). The mean 24 h BP was very reproducible with a CV of 4.7%. Using the fixed definition of day and night, mean night time systolic blood pressure (SBP) was significantly reduced on the second visit compared to the first (P < 0.001). Using fixed times for day and night, day-night difference was poorly reproducible, with a CV of 52% for SBP and 59% for diastolic blood pressure (DBP), however this improved using diary based day-night to 40/41% and cusum analysis to 24.6/28.1%. We recommend that circadian BP changes are studied using individual definitions of day and night or time independent methods such as cusum analysis.
    Journal of Human Hypertension 03/1996; 10(3):163-6. · 2.82 Impact Factor
  • The Lancet 01/1994; 343(8890):151–154. · 39.21 Impact Factor

Publication Stats

449 Citations
158.18 Total Impact Points

Institutions

  • 2008–2009
    • University of Liverpool
      • Department of Clinical Sciences
      Liverpool, ENG, United Kingdom
  • 1999–2008
    • Royal Liverpool and Broadgreen University Hospitals NHS Trust
      • Department of Diabetes and Endocrinology
      Liverpool, England, United Kingdom
    • Aintree University Hospital NHS Foundation Trust
      Liverpool, England, United Kingdom
  • 1997
    • University of Leicester
      Leiscester, England, United Kingdom