Biomedical subjects

R John Irving

Publications and source records attributed to R John Irving.

5 recordsLinked to original sources

PubMed2005

The incidence of implantable cardioverter defibrillator indications in patients admitted to all coronary care units in a single district.

AIMS: Implantable cardioverter defibrillators (ICDs) have been shown to reduce all-cause mortality in groups of patients at high risk of ventricular arrhythmias. The true incidence of ICD indications is unknown but we hypothesize that it far exceeds the number actually implanted. METHODS: In a one month observational audit, we reviewed the clinical records of all 336 patients admitted to coronary care units serving a district with a population of 471,000, to determine the additional screening tests required in myocardial infarction (MI) survivors and the number of additional ICDs which would be implanted for the primary and secondary prevention indications recommended in UK National Institute for Clinical Excellence (NICE) guidance. A further analysis was performed to determine the effect of extending the primary prevention indications to include the selection criteria used in the second multicentre automatic defibrillator trial, MADIT II. RESULTS: Using NICE criteria, we found the incidence of ICD indications to be 98.4/10(6)/year. The addition of patients fulfilling MADIT II selection criteria for primary prevention would have increased this to 453/10(6)/year. CONCLUSION: We conclude that the implementation of national guidance on the use of ICDs for arrhythmias will require the systematic screening of MI survivors, and would identify an incidence of ICD indications at least three times that anticipated by NICE, and eight times as many as were actually implanted in the UK in 2000. If the primary prevention indications were widened to include MADIT II selection criteria, the total would be nearer to 12 times that anticipated, and 47 times the number actually implanted.

Adult↗

PubMed2004

Low birth weight predicts higher blood pressure but not dermal capillary density in two populations.

The association between low birth weight and high blood pressure is well established, but underlying mechanisms remain undefined. Vascular rarefaction, which may elevate peripheral vascular resistance, has been observed in capillaries of young men at risk for hypertension and men who had low birth weight. We looked for evidence that capillary rarefaction explains the association of low birth weight with high blood pressure in two cohorts. Participants in study 1 included 107 healthy boys aged 6 to 16 years recruited at random from a single school. Study 2 included 61 members of a cohort recruited at birth and studied at age 24 years. Measurements included indices of current size, blood pressure by automated sphygmomanometer, and dermal capillary density by video capillaroscopy of dorsal index finger skin after 10 minutes of venous occlusion. Lower birth weight predicted higher systolic blood pressure in both studies: in study 1, 3.57 mm Hg/kg birth weight (after adjustment for current height, 95% confidence interval 0.38 to 6.75, P<0.05); in study 2, 122+/-12 mm Hg in low birth weight (<2 kg) versus 115+/-9 in controls (P<0.05). Dermal capillary density was not associated in either group with birth weight or systolic blood pressure. We have found no evidence in these 2 cohorts that reduced capillary density explains the associations between lower birth weight and higher blood pressure.

Adolescent↗

PubMed2003

Implications of national guidance for implantable cardioverter defibrillation implantation in the United Kingdom.

To determine the number of patients fulfilling recently issued national guidelines on the use of ICDs in patients with arrhythmias, the authors undertook two observational audits of clinical records. The first audit included patients investigated and treated at a tertiary referral cardiothoracic center during a 1-month period, and the second included patients admitted to the three coronary care units serving a circumscribed district population during a second month. Patient records were audited against the recommendations for ICD implantation made by the National Institute for Clinical Excellence to determine if the patient fulfilled the criteria for ICD implantation. The audit was repeated with the same patient records against the MADIT 2 selection criteria. The audit identified underprovision of ICD therapy in the United Kingdom for a variety of reasons. It also demonstrated that the number of patients fulfilling selection criteria defined by the national guidelines for ICD implantation is far in excess of the numbers predicted. The annual incidence of patients fulfilling national criteria is about 150/million, with an additional "prevalence" of at least 41/million. Applying the less restrictive MADIT II criteria to select patients for ICDs as a primary prevention increased the numbers to 504/million ("new incidence") and 311/million ("prevalence") per year, in excess of the predictions by a factor of between 10 and 25.

Defibrillators, Implantable↗

PubMed2002

Contrasting effects of intrauterine growth retardation and premature delivery on adult cortisol secretion and metabolism in man.

OBJECTIVE: Among babies born at term, intrauterine growth retardation (IUGR) predicts adult hypertension and hyperglycaemia. This might be due to elevated circulating glucocorticoids in adulthood, as described in animal models and in several cohorts of men who were low birthweight at term. Recently, we found that premature low birthweight babies also have adult cardiovascular risk factors, irrespective of IUGR. We have now investigated cortisol secretion in this group. DESIGN PATIENTS AND MEASUREMENTS: We studied 29 women and 23 men aged 22-25 years who had been recruited at birth as either normal term (mean birthweight 3.1 kg, gestation 39 weeks), premature appropriate for gestational age (AGA; 1.7 kg, 32 weeks), or premature IUGR (1.7 kg, 35 weeks) babies. Body composition was measured by dual-energy X-ray absorptiometry (DEXA); plasma was obtained at 0900 h after overnight fast; and cortisol metabolites were measured in a 24-h urine sample by gas chromatography/mass spectrometry (GCMS). RESULTS: Cortisol metabolites were different in men and women, so results were analysed separately. Among women, adult body composition did not differ between groups. Plasma cortisol was not different, but total urinary cortisol metabolite excretion was lower in AGA (3.29 +/- 1.91 mg/day, n = 7, P < 0.02) than in either normals (6.77 +/- 4.10, n = 14) or IUGR (9.47 +/- 8.84, n = 8). Relative excretion of cortisol and cortisone metabolites was not different. Statistically significant differences in cortisol parameters between groups were not seen in men. CONCLUSIONS: Premature AGA baby girls have lower cortisol secretion in adulthood but normal plasma cortisol, suggesting impaired metabolic clearance of cortisol. By contrast, premature IUGR babies maintain normal cortisol secretion as adults, suggesting that IUGR, rather than premature delivery, is responsible for programmed activation of the hypothalamic-pituitary-adrenal (HPA) axis. The ability to detect such dramatic differences in a small study suggests that programming has a potent influence on adult cortisol secretion.

Adult↗

PubMed2002

Peripheral vascular structure and function in men with contrasting GH levels.

Both GH deficiency and excess are associated with cardiovascular disease. The mechanisms are unclear, but direct effects of GH in the vessel wall may be important. Previous reports suggest that GH enhances endothelium-dependent vasodilatation and alters large artery structure. Here we report a detailed assessment of large artery and microvascular structure and function in patients with contrasting GH levels. We studied six age-matched healthy control men, five men with acromegaly, and seven men with adult-onset GH deficiency before and at the end of 16 wk of GH replacement therapy. We measured arterial wall thickness by ultrasound of the common carotid artery; arterial stiffness by pulse wave analysis at the radial artery; microvascular structure by measurement of flow during maximal dilatation in the forearm and dermal circulation and counting dermal capillaries using video microscopy; and endothelial function in the forearm during brachial artery infusion of vasodilators (acetylcholine and sodium nitroprusside). Cardiac output was measured by Doppler ultrasound in GH-deficient patients and controls. GH-deficient patients tended to have increased arterial wall thickness and arterial stiffness, compared with controls. GH replacement reduced arterial stiffness (radial augmentation index 0.28 +/- 0.07 to 0.20 +/- 0.12, P = 0.02) and increased the number of dermal capillaries perfused (28.6 +/- 5.0 to 30.9 +/- 6.5 cm(-2), P = 0.03), but a reduction in arterial wall thickness was not statistically significant. With respect to maximum flow in forearm and dermis and endothelial function, GH-deficient patients were not different from controls, and GH therapy had no effect. Moreover, acromegalic patients were not different from controls in any vascular parameters studied. We conclude that the direct vascular effects of GH excess and deficiency in man are of modest magnitude and should not therefore be given the highest priority in considering the risks of cardiovascular events in patients with pituitary disease.

Acromegaly↗