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Biomedical subjects

Thomas W Wilson

Publications and source records attributed to Thomas W Wilson.

17 recordsLinked to original sources
PubMed2006

Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers in hypertension due to primary aldosteronism: a case for exclusion.

Aldosterone antagonists are the mainstay of therapy in patients with hypertension due to primary aldosteronism. However, in our experience, these patients are sometimes placed on angiotensin-converting enzyme (ACE) inhibitors in accordance with guidelines applying to the general hypertensive population. We believe this practice is inappropriate because of the inability of ACE inhibitors to lower blood pressure in patients with low renin levels. Furthermore, pleiotropic effects of ACE inhibitors are unlikely to provide significant benefits in the absence of blood pressure reduction. Therefore, ACE inhibitors should be discouraged for the majority of patients with primary aldosteronism, even in the face of renal or cardiac disease.

Angiotensin Receptor Antagonists↗
PubMed2006

EDHF-mediated rapid restoration of hypotensive response to acetylcholine after chronic, but not acute, nitric oxide synthase inhibition in rats.

Several in vitro studies have shown that endothelium-dependent vasodilatation is maintained by endothelium-derived hyperpolarizing factor (EDHF) or prostacyclin in vessels isolated from endothelial nitric oxide synthase knockout mice. Since this has not been addressed by in vivo studies, we sought to define the magnitude and the onset time of this compensation by recording blood pressure responses to endothelium-dependent vasodilators in rats treated acutely or chronically with the NOS inhibitor, N(omega)-nitro-L-arginine methyl ester (L-NAME). Groups of male Sprague-Dawley rats were given plain water (control) or L-NAME (0.7 mg/ml) in drinking water for 1 day, 5 days, 3 wks or 6 wks. Dose-dependent hypotensive responses to acetylcholine, bradykinin and sodium nitroprusside were determined in anesthetized rats before and after acute intravenous infusion of either L-NAME or a combination of apamin plus charybdotoxin that would selectively inhibit EDHF. Acute L-NAME treatment increased the mean arterial pressure and inhibited acetylcholine- and bradykinin-induced fall in blood pressure in control but not in chronic L-NAME treated rats. The endothelium-dependent hypotensive responses to acetylcholine and bradykinin were restored in rats treated with L-NAME after a time period of 24 h along with increased sensitivity to sodium nitroprusside and reduced plasma nitrate+nitrite levels. While apamin+charybdotoxin pretreatment inhibited the responses to acetylcholine and bradykinin in both acute and chronic L-NAME treated groups, it was more pronounced in the latter group. In conclusion, chronic inhibition of nitric oxide synthase results in the development of a compensatory hypotensive response to acetylcholine within 24 h and this is mediated by EDHF.

Acetylcholine↗
PubMed2006

Antihypertensive medications and blood sugar: theories and implications.

Increased rates of diabetes have been reported with thiazide diuretics and beta-blockers, but not with angiotensin-converting enzyme inhibitors, angiotensin receptor blockers or calcium channel blockers. These observations are important because significant glycemic effects of drugs may be a source of accelerated cardiovascular risk that is not detectable during restricted clinical trial follow-up periods. The extent to which diabetes is affected by these medications remains unclear, as is the precise mechanism by which diabetes is promoted. However, several plausible theories are presented herein. Although drug-induced diabetes has been a concern for several years, not enough information is available to influence prescribing for the majority of patients. The number one priority should be controlling blood pressure in a timely manner.

Adrenergic beta-Antagonists↗
PubMed2006

Clofibrate acutely reverses saline-induced endothelial dysfunction: role of calcium-activated potassium channels.

BACKGROUND: Endothelium-dependent vascular relaxation is impaired in various disease states including hypertension. METHODS: We investigated whether a single bolus dose of clofibrate could rapidly reverse saline-induced endothelial dysfunction, in vivo, in salt-loaded Sprague-Dawley (S-D) rats. S-D rats, 5 weeks of age, were divided into two groups. One group served as a control (Con) and was given tap water; the other group (Sal) was given normal saline (0.9% NaCl) ad libitum for 3 weeks. RESULTS: Mean arterial pressure (MAP) was significantly higher (138 +/- 2 nu 112 +/- 2 mm Hg, P < .001), whereas the total plasma nitrite/nitrate levels were lower (1.7 +/- 0.3 v 2.8 +/- 0.2 micromol/L, P < .05) in Sal. At this time, endothelial function was assessed in vivo. Sal rats had decreased hypotensive responses to acetylcholine (ACh) but maintained normal responses to sodium nitroprusside. The ACh-induced hypotensive response was significantly inhibited by the nitric oxide synthase inhibitor, N(G)-nitro-l-arginine methyl ester (L-NAME, 100 mg kg(-1) intraperitoneally [ip]) only in Con rats. Clofibrate (Clof, 200 mg kg(-1) ip) did not change blood pressure but increased ACh-induced hypotensive responses only in Sal, an effect that was abolished by subsequent administration of apamin (Apa, 50 microg kg(-1) iv) and charybdotoxin (ChTx, 50 microg kg(-1) iv). Apa+ChTx blocked responses to ACh in Con and Sal, as expected. A single dose of clofibrate (200 mg kg(-1) ip), given subsequently to Apa+ChTx, restored responses to ACh in both the Con and Sal groups, again without affecting baseline MAP. CONCLUSION: Clofibrate has an acute salutary effect on endothelium-dependent vasodilation in saline-treated rats, probably mediated through vascular calcium-activated potassium channels and independent of an antihypertensive effect.

Acetylcholine↗
PubMed2006

Inability to upregulate cytochrome P450 4A and 2C causes salt sensitivity in young Sprague-Dawley rats.

BACKGROUND: Young Sprague-Dawley rats develop high blood pressure (BP) when exposed to a high salt intake, whereas adult ones generally do not. We investigated the role of renal cytochromes P450 4A (CYP 4A) and 2C (CYP 2C) in maintaining normal BP. METHODS: Young (age 5 weeks) and adult (age 53 weeks) Sprague-Dawley rats were given either 20 mmol sodium carbonate (vehicle for clofibrate) or 0.9% saline to drink for 3 weeks. Some young animals received the peroxisome proliferator activated receptor (PPAR)alpha agonist clofibrate (80 mg daily). We measured tail-cuff and intra-arterial BP, weight change, sodium balance, 20-hydroxyeicosatetraenoic acid (20-HETE) excretion (by high-performance liquid chromatography), and renal expression of CYP 4A and CYP 2C (by real-time reverse transcriptase-polymerase chain reaction). RESULTS: Saline-treated adult animals remained normotensive: systolic BP (SBP) 117 +/- 2 mm Hg v 117 +/- 1 mm Hg in control animals. In contrast, young rats given saline developed increased SBP: 134 +/- 2 mm Hg v 115 +/- 2 mm Hg in control animals (P < . 001). Interestingly, clofibrate lowered SBP to 102 +/- 2 mm Hg in saline-treated young rats but had no effect in control animals (114 +/- 2 mm Hg). Adult rats given saline increased renal expression of CYP 4A and 2C and excreted more 20-HETE. However, young rats given saline showed no induction, and even reduced CYP 4A and 2C, decreased urinary 20-HETE excretion, and retained sodium. Clofibrate increased renal CYP and 20-HETE excretion and prevented sodium retention. CONCLUSIONS: The products of renal CYP4A and 2C, including 20-HETE, aid in excreting salt. Animals that are unable to increase renal 20-HETE formation do not excrete sodium and are prone to hypertension.

Aging↗
PubMed2005

Adherence to statins, beta-blockers and angiotensin-converting enzyme inhibitors following a first cardiovascular event: a retrospective cohort study.

BACKGROUND: Population studies of statin adherence are generally restricted to one to two years of follow-up and do not analyze adherence to other drugs. OBJECTIVES: To report long-term adherence rates for statins, angiotensin-converting enzyme (ACE) inhibitors and beta-blockers in patients who recently experienced a first cardiovascular event. METHODS: Linked administrative databases in the province of Saskatchewan were used in this retrospective cohort study. Eligible patients received a new statin prescription within one year of their first cardiovascular event between 1994 and 2001. Adherence to statins, beta-blockers and ACE inhibitors was assessed from the first statin prescription to a subsequent cardiovascular event. RESULTS: Of 1221 eligible patients, the proportion of patients adherent to statin medications dropped to 60.3% at one year and 48.8% at five years. The decline in the proportion of adherent patients was most notable during the first two years (100% to 53.7%). Several factors were associated with statin adherence, including age (P = 0.012), number of physician service days (P = 0.037), chronic disease score (P = 0.032), beta-blocker adherence (P < 0.001) and ACE inhibitor adherence (P < 0.001). Adherence to beta-blockers and ACE inhibitors was very similar to adherence to statin medications at each year of follow-up. CONCLUSIONS: Patients who exhibit optimal adherence over one to two years after their initial cardiovascular event generally remain adherent over subsequent years. Also, adherence to beta-blockers and ACE inhibitors is significantly associated with statin adherence in a subset of patients; however, overall adherence to all three drugs was similarly poor.

Adrenergic beta-Antagonists↗
PubMed2005

Cardiovascular morbidity associated with nonadherence to statin therapy.

STUDY OBJECTIVE: To measure the extent of cardiovascular morbidity associated with nonadherence to 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor (statin) therapy. DESIGN: Retrospective cohort study. DATA SOURCE: Linked administrative health databases in Saskatchewan, Canada. PATIENTS: A total of 1221 patients aged 30-70 years who received a new prescription for a statin drug between 1994 and 2001, within 1 year of their first cardiovascular event (i.e., myocardial infarction, unstable angina, ischemic stroke, percutaneous transluminal coronary angioplasty [PTCA], or coronary artery bypass graft [CABG]). MEASUREMENTS AND MAIN RESULTS: Adherence was measured by the fill frequency (number of prescriptions filled during the observation period divided by months of observation). Patients with a fill frequency of 80% or greater were classified as adherent (661 patients); those with a fill frequency of 60% or less were classified as nonadherent (395 patients). The remaining 165 patients who had adherence rates of 61-79% were excluded from the analysis. The primary end point included a composite of myocardial infarction, unstable angina, PTCA, CABG, and death. Among 1056 patients, adherence was not associated with a reduction of the primary end point. However, patients in the adherent group were half as likely to experience a subsequent myocardial infarction as the patients in the nonadherent group (hazard ratio [HR] 0.45, 95% confidence interval [CI] 0.20-0.99, p=0.047). In patients younger than 65 years (both adherent and not), the associated reduction in myocardial infarction was even more profound (HR 0.14, 95% CI 0.04-0.46, p=0.001) and was accompanied by a trend for a lower frequency of unstable angina (HR 0.37, 95% CI 0.13-1.03, p=0.06). In patients 65 years or older (301 patients), adherence was not associated with significant changes in cardiovascular end points. CONCLUSION: A detectable excess of cardiovascular morbidity appears to be associated with nonadherence to statin therapy. Our analysis suggests that many occurrences of myocardial infarction could be prevented with improvements in adherence. Larger studies are necessary to determine the association between adherence and other cardiovascular end points.

Adult↗
PubMed2004

Beneficial and deleterious effects of rosiglitazone on hypertension development in spontaneously hypertensive rats.

The antihypertensive effect of the peroxisome proliferator-activated receptor (PPAR)gamma agonist rosiglitazone has been reported in patients with diabetes or obesity. The correlation of PPARgamma expression with blood pressure and the therapeutic application of rosiglitazone in spontaneously hypertensive rats (SHR) were investigated in the present study. Systolic blood pressure of 21-week SHR was significantly higher than that of age-matched Wistar-Kyoto rats (WKY) (225 +/- 5 v 144 +/- 2 mm Hg, P <.05). Basal expression levels of PPARgamma proteins in vascular tissues of 21-week SHR were significantly lower than that of age-matched 21-week WKY (P <.05). This reduced expression of PPARgamma was not detected between 5- and 13- week SHR and age-matched WKY. Cardiac PPARgamma expression was also not different among different age groups between SHR and WKY. Chronic treatment with rosiglitazone, but not PPARalpha agonist Wy14643, significantly retarded hypertension development and reversed abnormally faster heart rate in young SHR. An unfavorable effect of rosiglitazone treatment was the increased heart-to-body weight ratio accompanied by left ventricular hypertrophy. In conclusion, vascular PPARgamma protein expression in adult SHR (21 weeks) is significantly decreased in comparison with the age-matched WKY. Chronic rosiglitazone treatment retards hypertension development, but the associated prohypertrophy effect calls for a cautious use of this thiazolidinedindione in the treatment of insulin resistance syndrome associated with hypertension.

Animals↗
PubMed2004

Assessing return on investment of defined-population disease management interventions.

BACKGROUND: Strategies to reduce health expenditures through the improvement of health and quality of care are in high demand. A group of experts formed a nonpartisan, independent work group, under the sponsorship of the National Managed Health Care Congress. Its goal was to establish a list of easy-to-understand, actionable, and usable recommendations to enable disease management program advocates to conduct basic-level evaluations. RECOMMENDATIONS: The work group made recommendations concerning identification of reference and intervention population, population definitions, quantitative methods and data quality, confounding and bias, and stakeholder agreements/contracting. CASE STUDY: A case study was created to quantitatively illustrate some of the major issues raised by the work group. Five typical errors were simulated by applying different rules to the intervention population than to the reference population: differential inclusion (high versus low risk), differential exclusion (high versus low risk) and differential claims run-out. Compared with the true impact, four of the five errors resulted in a bias toward "intervention effect," while one (differential inclusion of high-risk patients) was biased against the "intervention effect." The direction and magnitude of the bias in natural settings will not necessarily follow this pattern.

Advisory Committees↗
PubMed2004

Accuracy of home blood pressure readings: monitors and operators.

OBJECTIVE: To evaluate the accuracy of automated digital blood pressure monitoring devices and operators in the community. Also, we tested the effects of a simple education program, and looked for arm-arm differences. DESIGN: Subjects who had bought their own automated digital blood pressure monitor were recruited via an advertisement in the local newspaper. On arrival, they were asked to record their blood pressure exactly as they would at home. The investigator noted any technique deficiencies then corrected them. Blood pressures were then recorded by the investigator and the subject, on opposite arms, simultaneously, and repeated with the arms switched. Finally, subjects recorded their blood pressure again. The subjects' readings were compared to the average of monitor and mercury readings using Bland-Altman methods. RESULTS: A total of 80 subjects were tested. Before educating, subjects' systolic blood pressure (SBP) readings were +5.8+/-6.4 (standard deviation) mmHg greater than the mean of all readings, and diastolic blood pressure (DBP) were +1.3+/-4.0 mmHg; after educating they were +1.3+/-4.0 and -1.3+/-2.7 respectively. The monitors, as a group, were accurate, and met British Hypertension Society and AAMI highest standards. We found no differences among monitors that had been validated (n=26) and those that had not. There were differences between the arms: 5.3+/-5.2 mmHg for SBP and 3.4+/-3.3 mmHg for DBP. Most patients had never been informed by anyone of proper blood pressure measuring techniques. CONCLUSIONS: We conclude that home blood pressure measurement, as practiced in our community, is prone to error, mostly due to mistakes by the operator. These can easily be corrected, so that readings become more accurate. Attention should be paid to arm-arm differences.

Aged↗
PubMed2004

Genetic influences on the increase in blood pressure with age in normotensive subjects in Barbados.

The authors tested the single and combined effects of nuclear and mitochondrial DNA genotypes on the phenotypes of systolic blood pressure (SBP) and weight, and their changes over 5 years in normotensive subjects living in Barbados. The nuclear genotypes were gender (Y chromosome), haptoglobin (HP), and group specific component (Gc). A mitochondrial genotype was chosen as a marker for maternal lineage. Baseline clinic SBP and weight (N=78), 24-hour SBP (N=28) were measured. Five years later, clinic SBP and weight were measured again in 28 participants. Male participants generally had higher pressures than female participants. The HP genotype was associated with 5 of the 8 SBP phenotypes. The haptoglobin-1 (HP1) allele was associated with higher clinic (P=.024) and evening SBP at baseline (P=.020). The effect of HP1 appears to be dominant. Haptoglobin-2 (HP2) was associated with the increase in weight over 5 years (P=.002). Group specific component (Gc) genotype was associated with 6 of the 8 SBP phenotypes. The Gc polymorphism 2 was associated with higher 24-hour SBP, sleep SBP (midnight-6 AM), afternoon SBP (noon-6 PM) and evening SBP (6 PM to midnight). Furthermore, we found a significant association between the haptoglobin/mt-DNA and Gc/mt-DNA polymorphisms with SBP between 6 PM and midnight (P=.009 and P=.011, respectively). The 5-year changes in SBP were significantly associated with the haptoglobin/mt-DNA and Gc/mt-DNA polymorphisms (P=.005 and P=.011, respectively). Multivariate analysis for genetic effects on change in weight and change in BP suggested the rise in BP, but was not suggestive of change in weight. Furthermore, multivariate analysis was associated with Gc, but not Haptoglobin genotype. In normotensive subjects of African descent living in Barbados, the increase in blood pressure with age is significantly influenced by both nuclear and mitochondrial genotypes that are more common in African derived populations.

Adult↗
PubMed2003

Are hot tubs safe for people with treated hypertension?

BACKGROUND: People with hypertension are commonly warned to check with a physician before using a hot tub, but there is little literature on which to base this advice. We compared symptoms, heart rate, and systolic and diastolic blood pressure in response to 10 minutes of hot-tub immersion in a group of patients with treated hypertension and in a control group normotensive subjects. METHODS: We recruited 21 patients (18 men and 3 women aged 43-76 years) with stable, treated hypertension and 23 control subjects (14 men and 9 women aged 19-83 years) without hypertension. They were studied, in mid-afternoon, at a public facility. Systolic and diastolic blood pressure and heart rate were measured at baseline, during immersion in a hot tub at 40 degrees C and for 10 minutes after immersion. We asked each subject to report any symptoms. RESULTS: None of the subjects reported dizziness, chest pain or palpitations. During immersion, systolic blood pressure fell in both groups, from a mean (and standard deviation [SD]) of 144 (17) mm Hg to 122 (18) mm Hg in the hypertensive group (p < 0.05) and from 130 (14) mm Hg to 110 (17) mm Hg in the control group (p < 0.05). It returned toward baseline within 10 minutes after the subjects left the hot tub. Diastolic blood pressure also fell, whereas heart rate was increased in both groups. The hypertensive group showed a slightly lower maximal increase in heart rate than the normotensive group (5 [SD 5] v. 13 [SD 10] beats/minute, p < 0.05). INTERPRETATION: Immersion in a hot tub for 10 minutes lowers blood pressure in subjects with treated hypertension, but no more than in normotensive control subjects. Spending 10 minutes in a hot tub should be safe for most treated hypertensive patients.

Adult↗
PubMed2003

Hypotension and bradycardia in infants after the use of topical brimonidine and beta-blockers.

Brimonidine is a selective alpha-2 adrenergic agonist used to treat glaucoma. There have been several reports of central nervous system depression after its use in infants. We observed rapid-onset bradycardia and decreased blood pressure in addition to central nervous system depression in 2 infants who received concomitant topical brimonidine and beta-blockers.

Administration, Topical↗
PubMed2003

White coat hypertension in treated hypertensives: a three year follow-up study.

Patients who participated in an initial study in a hypertension outpatient clinic in a tertiary care hospital in Western Canada were approached three years later to participate in a follow-up study. The aim of this study was to describe changes, over three years, in office (OBP) and ambulatory blood pressure and blood pressure load (BPL) in a group of treated hypertensives, with and without white coat hypertension (WCH). In the initial study, 103 consecutive patients with OBP over 140/90 (either/both), despite being prescribed two or more antihypertensive drugs, were divided into groups based on average daytime ambulatory blood pressures (DABP). Sustained hypertension was defined as DABP > 140/90 (both) and WCH as DABP < 135/85 (both). All others were defined as borderline hypertension. In 1998, we repeated office and DABP readings in 79 of the original 103 patients. Daytime BPL decreased significantly over the three years of the study for those originally categorized as sustained hypertension [78 + 21 to 50 + 34 for systolic BPL (p = < 0.001) and 75 + 21 to 41 + 29 for diastolic BPL (p = < 0.001)]. Similarly, BPL fell in borderline hypertensives while BPL remained low, but increased somewhat, for WCH. OBP declined in all groups; thus, from a medical standpoint, this supports the argument that all those diagnosed with hypertension based on the OBP should remain on antihypertensive treatment. For nurses counselling patients with WCH, it provides a cautionary note that these patients, if already on antihypertensive medication, should probably continue treatment as WCH does not appear to be stable over time.

Antihypertensive Agents↗
PubMed2002

The 2001 Canadian recommendations for the management of hypertension: Part one--Assessment for diagnosis, cardiovascular risk, causes and lifestyle modification.

OBJECTIVE: To provide updated, evidence-based recommendations for the assessment of the diagnosis, cardiovascular risk, identifiable causes and lifestyle modifications for adults with high blood pressure. OPTIONS: For persons in whom a high blood pressure value is recorded, hypertension is diagnosed based on the appropriate measurement of blood pressure, the level of the blood pressure elevation and the duration of follow-up. In addition, the presence of concomitant vascular risk factors, target organ damage and established atherosclerotic diseases must be assessed to determine the urgency, intensity and type of treatment. For persons receiving a diagnosis of hypertension, defining the overall risk of adverse cardiovascular outcomes requires an assessment of concomitant vascular risk factors, including laboratory testing, a search for target organ damage and an assessment for modifiable causes of hypertension. Home and ambulatory blood pressure assessment and echocardiography are options for selected patients. OUTCOMES: The outcomes were: the identification of persons at increased risk of adverse cardiovascular outcomes; the quantification of overall cardiovascular risk; and the identification of persons with potentially modifiable causes of hypertension. EVIDENCE: Medline searches were conducted from one year before the period of the last revision of the Canadian recommendations for the management of hypertension (May 1999 to May 2001). Reference lists were scanned, experts were polled, and the personal files of the subgroup members and authors were used to identify other studies. Identified articles were reviewed and appraised, using prespecified levels of evidence, by content experts and methodological experts. In addition to an update of the previous year's review, new sections on assessing overall cardiovascular risk and endocrine causes are provided. VALUES: A high value was placed on the identification of persons at increased risk of cardiovascular morbidity and mortality, and of persons with identifiable causes of hypertension. BENEFITS, HARMS AND COSTS: The identification of persons at higher risk of cardiovascular disease will permit counseling for lifestyle manoeuvres and introduction of antihypertensive drugs to reduce blood pressure for patients with sustained hypertension. The identification of specific causes of hypertension may permit the use of cause-specific interventions. In certain subgroups of patients, and for specific classes of drugs, blood pressure lowering has been associated with reduced cardiovascular morbidity or mortality. RECOMMENDATIONS: The present document contains recommendations for the assessment of the diagnosis, cardiovascular risk, identifiable causes and lifestyle modifications for adults with high blood pressure. These include the accurate measurement of blood pressure, criteria for the diagnosis of hypertension and recommendations for follow-up, assessment of overall cardiovascular risk, routine and optional laboratory testing, assessment for renovascular and endocrine causes, home and ambulatory blood pressure monitoring, the role of echocardiography and lifestyle modifications. VALIDATION: All recommendations were graded according to the strength of the evidence and voted on by the Canadian Hypertension Recommendations Working Group. Only those recommendations achieving high levels of consensus are reported. These guidelines will be updated annually. ENDORSEMENT: These guidelines are endorsed by the Canadian Hypertension Society, The Canadian Coalition for High Blood Pressure Prevention and Control, The College of Family Physicians of Canada, The Heart and Stroke Foundation of Canada, The Adult Disease Division and Bureau of Cardio-Respiratory Diseases and Diabetes at the Centre for Chronic Disease Prevention and Control, Health Canada.

Antihypertensive Agents↗