Collin I. Johnston

Controlled trial of enalapril in congestive cardiac failure.

Twenty five patients with chronic congestive cardiac failure had enalapril (n = 13) or placebo (n = 12) added to their existing regimen of digoxin and frusemide in a randomised double blind trial. Four hours after the first 5 mg dose, the enalapril group showed significant falls in blood pressure, heart rate, and concentrations of plasma angiotensin II, angiotensin converting enzyme, and noradrenaline. During the 12 week trial heart failure became worse in one enalapril treated patient (8%) and in seven placebo treated patients (58%). There were no significant changes in cardiac ejection fraction or exercise duration in either group. Plasma noradrenaline response to graded exercise and maximum exercise rate-pressure product were significantly reduced after four and 12 weeks of active treatment but unchanged with placebo treatment. There was a sustained increase in plasma potassium and a slight rise in plasma creatinine in the enalapril group. Plasma concentrations of the active drug, enalaprilate, were dose related and log enalaprilate correlated significantly with percentage of plasma angiotensin converting enzyme activity (r = -0.66). Enalapril was well tolerated and produced no adverse effects. The drug appears to be superior to placebo and offers considerable promise for the treatment of this condition.

Who's really hypertensive? - Quality control issues in the assessment of blood pressure for randomized trials

The characterization of blood pressure in treatment trials assessing the benefits of blood pressure lowering regimens is a critical factor for the appropriate interpretation of study results. With numerous operators involved in the measurement of blood pressure in many thousands of patients being screened for entry into clinical trials, it is essential that operators follow pre‐defined measurement protocols involving multiple measurements and standardized techniques. Blood pressure measurement protocols have been developed by international societies and emphasize the importance of appropriate choice of cuff size, identification of Korotkoff sounds, and digit preference. Training of operators and auditing of blood pressure measurement may assist in reducing the operator‐related errors in measurement. This paper describes the quality control activities adopted for the screening stage of the 2nd Australian National Blood Pressure Study (ANBP2). ANBP2 is cardiovascular outcome trial of the treatment of hypertension in the elderly that was conducted entirely in general practices in Australia. A total of 54 288 subjects were screened; 3688 previously untreated subjects were identified as having blood pressure >140/90 mmHg at the initial screening visit, 898 (24%) were not eligible for study entry after two further visits due to the elevated reading not being sustained. For both systolic and diastolic blood pressure recording, observed digit preference fell within 7 percentage points of the expected frequency. Protocol adherence, in terms of the required minimum blood pressure difference between the last two successive recordings, was 99.8%. These data suggest that adherence to blood pressure recording protocols and elimination of digit preferences can be achieved through appropriate training programs and quality control activities in large multi‐centre community‐based trials in general practice. Repeated blood pressure measurement prior to initial diagnosis and study entry is essential to appropriately characterize hypertension in these elderly patients.

Prediction of cardiovascular and all-cause mortality at 10 years in the hypertensive aged population

BACKGROUND We have previously developed a score for predicting cardiovascular events in the intermediate term in an elderly hypertensive population. In this study, we aimed to extend this work to predict 10-year cardiovascular and all-cause mortality in the hypertensive aged population. METHODS Ten-year follow-up data of 5,378 hypertensive participants in the Second Australian National Blood Pressure study who were aged 65-84 years at baseline (1995-2001) and without prior cardiovascular events were analyzed. By using bootstrap resampling variable selection methods and comparing the Akaike and Bayesian information criterion and C-indices of the potential models, optimal and parsimonious multivariable Cox proportional hazards models were developed to predict 10-year cardiovascular and all-cause mortality. The models were validated using bootstrap validation method internally and using the Dubbo Study dataset externally. RESULTS The final model for cardiovascular mortality included detrimental (age, smoking, diabetes, waist-hip ratio, and disadvantaged socioeconomic status) and protective factors (female sex, alcohol consumption, and physical activity). The final model for all-cause mortality also included detrimental (age, smoking, random blood glucose, and disadvantaged socioeconomic status) and protective factors (female sex, alcohol consumption, body mass index, and statin use). Blood pressure did not appear in either model in this patient group. The C-statistics for internal validation were 0.707 (cardiovascular mortality) and 0.678 (all-cause mortality), and for external validation were 0.729 (cardiovascular mortality) and 0.772 (all-cause mortality). CONCLUSIONS These algorithms allow reliable estimation of 10-year risk of cardiovascular and all-cause mortality for hypertensive aged individuals.

Role of vasopressin in experimental congestive cardiac failure.

The hemodynamic and hormonal changes produced by adriamycin-induced cardiomyopathic congestive heart failure in rabbits were studied. Adriamycin cardiomyopathy in rabbits led to ventricular dilatation, pleural and pericardial effusions, hepatic congestion, and ascites. These pathological changes were associated with the maintenance of a normal blood pressure but a lowered cardiac output and increased total peripheral resistance. Plasma renin activity and plasma norepinephrine were increased twofold in rabbits with congestive cardiac failure. However, plasma vasopressin and osmolality were normal, whereas an increased vascular sensitivity to the infusion of exogenous vasopressin was demonstrated. Despite the normal levels of plasma vasopressin, administration of a specific vascular vasopressin antagonist led to a fall in blood pressure, a significant increase in cardiac output, and a decrease in total peripheral resistance. No such hemodynamic changes occurred on infusing normal rabbits with the vascular vasopressin antagonist, nor did any significant hemodynamic changes occur on injecting vehicle in rabbits with heart failure. These results suggest that in adriamycin-induced cardiomyopathic heart failure in rabbits, there is activation of the renin-angiotensin system and the sympathetic nervous system together with an increased sensitivity to vasopressin. These three hormonal systems help to maintain blood pressure by increasing total peripheral resistance in this experimental model of heart failure.

FEASIBILITY OF CONDUCTING CARDIOVASCULAR OUTCOME RESEARCH IN AUSTRALIAN GENERAL PRACTICE: RESULTS FROM THE ANBP2 PILOT STUDY

1. The present study aimed to determine the feasibility of conducting a 5 year cardiovascular outcome trial of the treatment of 6000 elderly hypertensive patients in Australian general practices.

Felodipine Compared to Prazosin as Additional Therapy to a Beta-Blocking Drug

Felodipine was compared with prazosin in patients with essential hypertension whose blood pressure was not controlled by a beta-blocking drug. One hundred patients with a supine diastolic blood pressure greater than or equal to mm Hg after 4 weeks or more on a beta-blocking drug and placebo were randomly assigned to felodipine or prazosin tablets. The drugs were titrated at 2-week intervals if diastolic BP was greater than or equal to 90 mm Hg. Titration steps of felodipine were 5, 10, 20 mg b.i.d. and of prazosin were 1, 2, 4 mg b.i.d. The fall in blood pressure with felodipine 32/21 mm Hg was greater than the fall with prazosin 16/12 mm Hg (p less than 0.001); 36 patients achieved a diastolic blood pressure of less than 90 mm Hg with felodipine, which was a significantly greater number than the 20 patients who obtained such a level with prazosin (p less than 0.01). Both drugs were well tolerated, but more patients complained of vascular type side effects (flushing, peripheral edema) with felodipine than with prazosin. There was significant weight gain with prazosin but not with felodipine. Felodipine was shown to be a well-tolerated, effective antihypertensive agent when used with a beta-blocking drug and to be suitable for people with hypertension who fail to be controlled with a beta-blocking drug.