Search PubMed⌕ Search

Biomedical subjects

R I Ogilvie

Publications and source records attributed to R I Ogilvie.

At least 19 recordsLinked to original sources
PubMed1999

Lifestyle modifications to prevent and control hypertension. 2. Recommendations on obesity and weight loss. Canadian Hypertension Society, Canadian Coalition for High Blood Pressure Prevention and Control, Laboratory Centre for Disease Control at Health Canada, Heart and Stroke Foundation of Canada.

OBJECTIVE: To provide updated, evidence-based recommendations concerning the effects of weight loss and maintenance of healthy weight on the prevention and control of hypertension in otherwise healthy adults (except pregnant women). OPTIONS: The main options are to attain and maintain a healthy body weight (body mass index [BMI] 20-25 kg/m2) or not to do so. For those at risk for hypertension, weight loss and maintenance of healthy weight may prevent the condition. For those who have hypertension, weight loss and maintenance of healthy weight may reduce or obviate the need for antihypertensive medications. OUTCOMES: The health outcome considered was change in blood pressure. Because of insufficient evidence, no economic outcomes were considered. EVIDENCE: A MEDLINE search was conducted for the years 1992-1996 with the terms hypertension and obesity in combination and antihypertensive therapy and obesity in combination. Other relevant evidence was obtained from the reference lists of the articles identified, from the personal files of the authors and through contacts with experts. The articles were reviewed, classified according to study design and graded according to level of evidence. VALUES: A high value was placed on the avoidance of cardiovascular morbidity and premature death caused by untreated hypertension. BENEFITS, HARMS AND COSTS: Weight loss and the maintenance of healthy body weight reduces the blood pressure of both hypertensive and normotensive people. The indirect benefits of a health body weight are well known. The negative effects of weight loss are primarily the frustrations associated with attaining and maintaining a healthy weight. The costs associated with weight loss programs were not measured in the studies reviewed. RECOMMENDATIONS: (1) It is recommended that health care professionals determine weight (in kilograms), height (in metres) and BMI for all adults. (2) To reduce blood pressure in the population at large, it is recommended that Canadians attain and maintain a healthy BMI (20-25). (3) All overweight hypertensive patients (BMI greater than 25) should be advised to reduce their weight. VALIDATION: These recommendations are similar to those of the World Hypertension League, the National High Blood Pressure Education Program Working Group on Primary Prevention of Hypertension, the Canadian Hypertension Society and the Canadian Coalition for High Blood Pressure Prevention and Control. They have not been clinically tested. SPONSORS: The Canadian Hypertension Society, the Canadian Coalition for High Blood Pressure Prevention and Control, the Laboratory Centre for Disease Control at Health Canada, and the Heart and Stroke Foundation of Canada.

Adult↗
PubMed1998

Captopril and angiotensin II receptor antagonist therapy in a pacing model of heart failure.

Twenty-four splenectomized dogs were subjected to rapid right ventricular pacing (RRVP) at 250 beats/min for five weeks. During the final three weeks, four groups six dogs were untreated or treated with captopril alone, with the angiotensin II type 1 (AT1) receptor antagonist L158,809 alone or with the two drugs combined by constant intravenous infusion. Hemodynamic studies were carried out during light anesthesia at baseline, and after two and five weeks of pacing. Total vascular capacitance and stressed blood volume were calculated from the mean circulatory filling pressure during transient circulatory arrest after acetylcholine administration at three different circulating volumes. Central blood volume and cardiac output were measured by thermodilution. Severe heart failure was present in the untreated group after five weeks of RRVP, characterized by low cardiac output and total vascular capacitance, high right atrial and pulmonary capillary wedge and mean circulatory filling pressure, plus increased stressed and central blood volumes. While L158,809 had not effect, captopril alone or combined with L158,809 ameliorated the reduction in total vascular capacitance, and reduced right atrial and mean circulatory pressure and stressed blood volumes. Combined therapy reduced pulmonary capillary wedge pressure. Thus, angiotensin-converting enzyme inhibition with captopril was effective in this model of chronic low output heart failure, whereas AT1 receptor antagonism was not.

Angiotensin II↗
PubMed1995

Acute effect of L-arginine on hemodynamics and vascular capacitance in the canine pacing model of heart failure.

The effect of L-arginine, 250 mg/kg over 10 min, on hemodynamics and venous function was studied in nine splenectomized dogs under light pentobarbital anesthesia before and after 17 +/- 1 days of rapid right ventricular pacing (RRVP) at 250 beats/min. Chronic RRVP induced mild congestive heart failure with increased mean circulatory filling (Pmcf), right atrial (Pra) and pulmonary capillary wedge pressures (Ppcw), and reduced cardiac output (CO). During the development of heart failure, total vascular compliance assessed from Pmcf-blood volume relationships during circulatory arrest was unchanged, but total vascular capacitance was markedly reduced, with an increase in stressed and reduction in unstressed blood volumes. At baseline but not after RRVP, L-arginine increased CO and reduced pulmonary vascular resistance. There were no significant changes in Pra, Ppcw, or total peripheral resistance. L-Arginine failed to alter total vascular compliance and capacitance or central blood volume in the baseline or failure state. These results do not support the hypothesis that increased Pmcf and reduced total vascular capacitance in the early stages of pacing-induced heart failure are caused by reduced substrate availability for or an endogenous competitive antagonist of NO synthase in venous endothelial cells.

Animals↗
PubMed1995

Vascular capacitance and cardiac output in pacing-induced canine models of acute and chronic heart failure.

The relationship between stressed and total blood volume, total vascular capacitance, central blood volume, cardiac output (CO), and pulmonary capillary wedge pressure (Ppcw) was investigated in pacing-induced acute and chronic heart failure. Acute heart failure was induced in anesthetized splenectomized dogs by a volume load (20 mL/kg over 10 min) during rapid right ventricular pacing at 250 beats/min (RRVP) for 60 min. Chronic heart failure was induced by continuous RRVP for 2-6 weeks (average 24 +/- 2 days). Total vascular compliance and capacitance were calculated from the mean circulatory filling pressure (Pmcf) during transient circulatory arrest after acetylcholine at three different circulating volumes. Stressed blood volume was calculated as a product of compliance and Pmcf, with the total blood volume measured by a dye dilution. Central blood volume (CBV) and CO were measured by thermodilution. Central (heart and lung) vascular capacitance was estimated from the plot of Ppcw against CBV. Acute volume loading without RRVP increased capacitance and CO, whereas after volume loading with RRVP, capacitance and CO were unaltered from baseline. Chronic RRVP reduced capacitance and CO. All interventions, volume +/- RRVP or chronic RRVP, increased stressed and central blood volumes and Ppcw. Acute or chronic RRVP reduced central vascular capacitance. Cardiac output was increased when stressed and unstressed blood volumes increased proportionately as during volume loading alone. When CO was reduced and Ppcw increased, as during chronic RRVP or acute RRVP plus a volume load, stressed blood volume was increased and unstressed blood volume was decreased. Thus, interventions that reduced CO and increased Ppcw also increased stressed and reduced unstressed blood volume and total vascular capacitance.

Acute Disease↗
PubMed1995

Effect of perindopril in pacing-induced canine models of acute and chronic heart failure.

OBJECTIVE: To examine the effects of perindopril, a nonsulfhydryl-containing angiotensin-converting enzyme inhibitor, on total vascular capacitance and hemodynamics in acute and chronic dog models of heart failure. METHODS: Acute heart failure was induced in anesthetized, splenectomized dogs by a volume load (dextran 70, 20 mL/kg) during rapid right ventricular pacing (RRVP) at 250 beats/min. Pretreatment with perindopril (0.3 mg/kg daily for six days, n = 7) was compared with no treatment (n = 7). Total vascular capacitance and compliance were measured from plots of mean circulatory filling pressure during acetylcholine-induced circulatory arrests at different blood volumes. Chronic heart failure was induced by continuous RRVP in splenectomized dogs treated with perindopril (0.3 mg/kg daily, n = 8), which were compared with untreated dogs (n = 8). Hemodynamics and total vascular capacitance and compliance were measured at baseline and after 33 days of RRVP. RESULTS: Perindopril treatment did not significantly modify the increased pulmonary capillary wedge and mean circulatory filling pressures, reduced total vascular compliance or total vascular capacitance associated with the volume load and acute RRVP. During chronic RRVP, perindopril reduced weight gain and the development of ascites, reduced right atrial pressure (6.3 +/- 1.3 versus 10.3 +/- 1.2 mmHg), mean circulatory filling pressure (9.3 +/- 1.0 versus 14.7 +/- 1.2 mmHg), stressed blood volume (22 +/- 3 versus 33 +/- 4 mL/kg) and central blood volume (10 +/- 1 versus 14 +/- 1 mL/kg) while increasing cardiac output (122 +/- 9 versus 98 +/- 7 mL/kg). However, the reduction in total vascular capacitance was not attenuated and pulmonary capillary wedge pressure was not lowered significantly (18.5 +/- 1.5 versus 21.4 +/- 1.3 mmHg). CONCLUSION: Perindopril failed to modify hemodynamics in the pacing-induced canine model of acute heart failure but had beneficial effects in the model of chronic heart failure.

Acute Disease↗
PubMed1995

Acute hemodynamic effects of drugs acting on the renin-angiotensin system in acute heart failure.

OBJECTIVE: To determine the role of the renin-angiotensin system in a model of acute heart failure. METHODS: Placebo or drugs (Ro 44-9375, a renin inhibitor; captopril, an angiotensin-converting enzyme [ACE] inhibitor; or DuP 532, an angiotensin II receptor [AT1] antagonist) were given to anesthetized splenectomized dogs (n = 12 for each group) for 50 mins after a volume load (dextran 70, 25 mL/kg over 10 mins) during rapid right ventricular pacing at 250 beats/min. Total vascular compliance and capacitance were determined from mean circulatory filling pressure-blood volume curves during transient circulatory arrests induced by acetylcholine. Cardiac index was measured by thermal dilution. RESULTS: Compared with the untreated group, all three drugs significantly reduced systemic pressure and total peripheral resistance while increasing arterial compliance. Captopril alone increased cardiac index (25 +/- 11 versus -23 +/- 13 mL/kg/min) and reduced pulmonary capillary wedge pressure (16.6 +/- 0.7 versus 21.9 +/- 1.0 mmHg). None of the drugs altered the mean circulatory filling pressure, total vascular compliance or capacitance, stressed or unstressed blood volumes, or central blood volume. CONCLUSION: The renin-angiotensin system is not strongly implicated in the hemodynamic manifestations of this model of acute heart failure. These drugs had effects on the arterial but not the venous side of the circulation. Captopril alone reduced pulmonary capillary wedge pressure, perhaps by nonangiotensin effects.

Acute Disease↗
PubMed1994

Pharmacokinetic and pharmacodynamic interactions during multiple-dose administration of nisoldipine and propranolol.

OBJECTIVES: The pharmacokinetic and pharmacodynamic interactions after 7 days of oral treatment with nisoldipine (10 mg twice daily) and propranolol (80 mg twice daily) were investigated in a partially randomized, placebo-controlled crossover study of 12 healthy volunteers. METHODS: At the end of each treatment period, pharmacokinetic parameters were measured, along with blood pressure, heart rate, cardiac function, systemic hemodynamics, plasma catecholamines, forearm blood flow, and apparent hepatic blood flow (estimated by the clearance of indocyanine green dye). RESULTS: After 7 days of treatment with nisoldipine and propranolol, neither drug altered the other's bioavailability or elimination parameters, and propranolol did not change the area under the plasma concentration-time curve of nisoldipine's metabolite, N-9425. Nisoldipine alone increased apparent hepatic blood flow and forearm blood flow compared with the other treatment groups but, with the addition of propranolol, both of these parameters were similar to those in the placebo group. Changes in the other hemodynamic parameters were consistent with the known effects of these drugs, and no differences in plasma catecholamine levels were detected. CONCLUSIONS: In contrast to the findings with single-dose treatment, administration of the combination of nisoldipine and propranolol for 7 days is not associated with any measurable kinetic interactions, although significant hemodynamic interactions do occur.

Adult↗
PubMed1994

Effect of captopril treatment on total and central vascular capacitance in dogs with chronic heart failure.

Chronic rapid right ventricular pacing (RRVP) at 250 beats/min produces low cardiac output (CO) heart failure, marked reduction in total vascular capacitance, and a shift in volume centrally. The effect of converting enzyme inhibition with captopril on cardiac preload was investigated in this model of heart failure. Eight splenectomized dogs were treated with captopril (6.4 mg/kg daily) for 3 days before and 35 +/- 3 days (mean +/- SEM) after continuous RRVP was initiated and the outcome was compared with that of 5 untreated dogs subjected to RRVP for 32 +/- 3 days. Similar reductions in systemic arterial pressure (Psa) and CO and increases in right atrial pressure (Pra) and total peripheral resistance (TPR) were noted in both groups, however, pulmonary capillary wedge pressure (Ppcw) was higher in the untreated group (18.4 +/- 1.6 vs. 12.1 +/- 2.0 mm Hg). Total vascular compliance and capacitance was estimated from mean circulatory filling pressures (Pmcf) at different blood volumes (TBV) during transitory cardiac arrests with acetylcholine (ACh). Pmcf after chronic RRVP was higher in untreated animals (12.6 +/- 1.9 vs. 8.4 +/- 0.7 mm Hg) and compliance was lower (1.9 +/- 0.2 vs. 2.6 +/- 0.2 ml/mm Hg/kg). Total vascular capacitance at a Pmcf of 6 mm Hg was lower in untreated animals (50 +/- 6 vs. 68 +/- 3 ml/kg). Central vascular capacitance was also lower in untreated animals because Ppcw was higher and central blood volume (CBV) as a proportion of TBV was higher (21 +/- 3 vs. 15 +/- 2%). Four of 5 untreated and 1 of 8 treated dogs had severe ascites.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1993

Captopril attenuates pacing-induced acute heart failure by increasing total vascular capacitance.

To study the effects of captopril pretreatment on vascular capacitance in acute heart failure, anesthetized splenectomized dogs were subjected to rapid right ventricular pacing (RRVP) at 250 beats/min for 60 min combined with an intravenous (i.v.) 20-ml/kg volume load of dextran 70 over 10 min. Captopril pretreatment [50 mg every 8 h for 3 days plus 0.5 mg/kg intravenously (i.v.) at induction of anesthesia] attenuated development of acute heart failure associated with RRVP, maintaining normal cardiac output (CO) and pulmonary capillary wedge pressures (PCWP). Total vascular capacitance after a volume load plus RRVP was higher in captopril-pretreated animals (129.8 +/- 3.2 vs. 100.4 +/- 4.8 ml/kg) owing to an increase in unstressed volume (118.6 +/- 3.1 vs. 88.4 +/- 5.6 ml/kg). Arterial capacity and pulmonary (central) vascular capacitance were also increased.

Acute Disease↗
PubMed1993

Calcium antagonists in heart transplant recipients: effects on cardiac and renal function and cyclosporine pharmacokinetics.

OBJECTIVE: Cyclosporine increases transmembrane calcium flux in mesangial and vascular smooth muscle cells, which may explain cyclosporine-induced decreases in renal bloodflow and glomerular filtration rate. Calcium antagonists, thus, may play a role in the prevention/reversal of cyclosporine nephrotoxicity. DESIGN: In a single-blind, randomized, cross-over study the authors evaluated the effects of a one-week treatment with nifedipine 20 mg bid, diltiazem 120 mg bid or placebo on cardiac and renal functions of six stable heart transplant recipients treated chronically with cyclosporine. RESULTS: Both calcium antagonists lowered blood pressure compared with placebo, but only nifedipine increased cardiac output and, therefore, decreased total peripheral resistance significantly more than diltiazem. Nifedipine induced a significant increase in effective renal plasma flow and an insignificant increase in glomerular filtration rate, whereas diltiazem caused a reduction in these parameters. Cyclosporine pharmacokinetics were not affected by either calcium antagonist to a clinically significant extent. CONCLUSIONS: Nifedipine and diltiazem exert distinctly different cardiac and renal hemodynamic effects in cardiac transplants, which may have clinical consequences.

Cyclosporine↗
PubMed1992

Isoproterenol increases defibrillation energy requirements in dogs.

The effect of intravenous isoproterenol on the energy requirements for successful defibrillation (DF) was examined in anesthetized dogs following cholinergic blockade with atropine (n = 5) and following treatment with d- and d,l-sotalol (n = 16). Defibrillation shocks were administered through left and right ventricular epicardial patch electrodes and the energy requirements for DF were studied using two different methods. Multiple shocks of varying energies were delivered and the energies required for 50% success (E50) and 80% success (E80) in DF were estimated using logistic regression. Atropine (0.04 mg/kg) increased E50 by 32 +/- 30% (p = 0.046) and E80 by 39 +/- 38% (p = ns). Subsequent administration of isoproterenol (10 micrograms/ml), increasing the heart rate by 52 +/- 35% (p = 0.025), resulted in a further 108 +/- 21% (p = 0.015) and 88 +/- 55% (p = 0.02) rise in E50 and E80 values, respectively. In a second set of experiments, d- (n = 9) and d,l-sotalol (n = 7) (4 mg/kg bolus followed by 0.025 mg/kg/min maintenance infusion) were administered and baseline curves relating delivered energy to % success in DF were calculated. Isoproterenol (10 +/- 4 micrograms/min) was given to increase the heart rate by 54 +/- 32% (p less than 0.025), and resulted in decreases in % success at each of two energy levels, falling in the midrange of the dose-response curve. Following d,l-sotalol, % successful shocks fell from 60 +/- 15 to 42 +/- 28% (p less than 0.05); following d-sotalol, the % success fell from 66 +/- 13 to 38 +/- 36% (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Effect of chronic rapid ventricular pacing on total vascular capacitance.

BACKGROUND: Rapid right ventricular pacing (RRVP) at 250 bpm for 3-6 weeks produces chronic heart failure manifested by a reduction in cardiac output and increases in right atrial, pulmonary artery, and capillary wedge pressures. METHODS AND RESULTS: One week after splenectomy and pacemaker placement, vascular capacitance, unstressed volume, and compliance were determined in 19 anesthetized dogs from pressure-volume curves using transient circulatory arrests induced by acetylcholine. Nine dogs were restudied 31 +/- 1 days later without RRVP, and 10 dogs underwent RRVP at 250 bpm and were restudied at 23 +/- 8 and 38 +/- 8 days in cardiac failure and after 1 and 2 weeks of postpacing recovery. Control animals had no changes in vascular capacitance or compliance. Dogs undergoing RRVP exhibited a marked increase in mean circulatory filling pressure (5.4 +/- 0.4 to 10.5 +/- 1.5 mm Hg) during the development of cardiac failure with a reduction in unstressed volume (81.9 +/- 5.7 to 43.9 +/- 8.1 ml.kg-1) without changing total vascular compliance. Total blood volume decreased (95.4 +/- 6.2 to 66.7 +/- 6.5 ml.kg-1) primarily due to a reduction in packed cell volume. The pressure gradient for venous return and overall venous resistance was unaltered. Central blood volume as a proportion of total blood volume increased (9.3 +/- 1.7% to 16.0 +/- 2.7%). Arterial compliance and capacity and pulmonary vascular compliance were reduced. In the 2-week postpacing period, except for a reduced cardiac response to a volume load, all of these parameters returned to baseline values. CONCLUSIONS: Chronic RRVP induced cardiac failure with a marked reduction in total vascular capacitance due to a reduction in unstressed volume without altering compliance. The rise in mean circulatory filling pressure was limited by a reduction in total blood volume.

Animals↗
PubMed1992

Acute effect of rapid ventricular pacing and volume loading on total vascular capacitance.

OBJECTIVE: Rapid right ventricular pacing (RRVP) at 250 beats/min plus a saline volume load produces acute heart failure manifested by a limited increase in cardiac output in response to the volume load and increased right atrial, pulmonary artery and capillary wedge pressures. The effects on vascular capacitance are unknown. DESIGN: Three groups of six anesthetized splenectomized dogs were subjected to RRVP alone at 250 beats/min for 40 mins volume loading alone with intravenous 0.9% sodium chloride 40 mL/kg over 10 mins or volume loading followed by RRVP for 15 mins. Vascular capacitance, unstressed volume and compliance were determined from pressure-volume curves using transient circulatory arrests induced by acetylcholine before and 40 mins after starting the interventions. RESULTS: Neither RRVP nor volume loading alone produced acute heart failure or altered total vascular compliance. Fifteen minutes of RRVP after the volume load induced heart failure, reduced compliance (3.4 +/- 0.5 to 2.5 +/- 0.3 mL/mmHg/kg, P < 0.05), increased central blood volume (7.7 +/- 0.7 to 10.6 +/- 0.5 mL/kg, P < 0.01) and reduced the unstressed vascular volume to 57 +/- 10 mL/kg, compared with 77 +/- 9 mL/kg (P < 0.01) after the volume load alone. Stressed blood volume was increased similarly with either volume loading alone (20.1 +/- 2.0 to 30.0 +/- 1.7 mL/kg, P < 0.01) or volume loading plus RRVP (23.5 +/- 3.8 to 30.2 +/- 4.9 mL/kg, P < 0.01). The reduction in unstressed volume rather than an increase in stressed volume was the major peripheral change associated with acute heart failure induced by volume loading plus RRVP. CONCLUSION: RRVP reduced vascular capacitance by a reduction in unstressed volume. Acute volume loading of this smaller vascular compartment resulted in redistribution centrally and acute heart failure.

Animals↗