Short-term analysis of the relationship between blood pressure and urinary sodium excretion in normotensive subjects

The aim of this study was to investigate whether, in the short term, physiological blood pressure changes are coupled with changes in urinary sodium excretion in normotensive subjects, maintained at fixed sodium intake and under controlled postural and behavioural conditions. Twelve normotensive subjects were recruited. For each subject, seven urine samples were collected at fixed time intervals during an overall 26 h period: late afternoon (16.00-20.00 hours), evening (20.00-24.00 hours), night (24.00-06.00 hours), quiet wakefulness (06.00-09.00 hours), morning (09.00-12.00 hours), post-prandial (12.00-15.00 hours) and afternoon (15.00-18.00 hours). Blood pressure was monitored by an ambulatory blood pressure device during the whole 26 h period. Each urine sample was used to measure urinary sodium excretion and glomerular filtration rate (creatinine clearance). Blood pressure, heart rate, urinary sodium excretion and glomerular filtration rate recorded in the daytime were higher than those measured during the night-time. A significant positive correlation between mean blood pressure and urinary sodium excretion was found during the night, over the whole 26 h period, and during two subperiods of the daytime: quiet wakefulness and the post-prandial period. The coefficient of the pressure-natriuresis curve was significantly decreased by postural changes. We conclude that, in normotensive subjects, blood pressure and urinary sodium excretion are coupled in the short term. The assumption of an upright posture can mask this relationship, presumably by activating neurohumoral factors.

Increased left ventricular dimensions in patients with frequent nonsustained ventricular arrhythmia and no evidence of underlying heart disease

INTRODUCTION

To test the hypothesis that frequent nonsustained ventricular premature beats (VPBs) in patients without underlying heart disease are the first marker of mild systolic dysfunction of the left ventricle, we evaluated whether a subclinical abnormality of left ventricular function and/or an intraventricular conduction defect was present at the first clinical documentation of the arrhythmia.

METHODS AND RESULTS

We compared 57 patients (mean age 46 +/- 14 years) with > 30 VPBs/hour and no heart disease (A) to 32 healthy volunteers (mean age 42 +/- 12 years) without arrhythmia (B). Left ventricular echocardiographic parameters and signal-averaged ECG were evaluated. Filtered QRS duration (98 +/- 10 msec in A vs 98 +/- 7 msec in B) was similar in the two groups. End-diastolic left ventricular diameter (EDLVD) was 50 +/- 6 mm in A versus 47 +/- 3 mm in B (P < 0.005); 15 patients (26%) and none of the controls had EDLVD > or = 55 mm (P < 0.005). Filtered QRS interval was longer in the subgroup of patients (n = 15) with increased EDLVD (> or = 55 mm) compared with the subgroup (n = 42) with EDLVD < 55 mm (106 +/- 9 msec vs 95 +/- 9 msec; P < 0.001) and was related to greater left ventricular mass.

CONCLUSION

We documented a subclinical but significant increase of left ventricular dimensions that suggests that frequent VPBs may be an initial marker of mild systolic dysfunction of the left ventricle. However, an effect of VPBs per se in modifying left ventricular dimensions cannot be excluded.

Arterial hypertension as a risk factor in the elderly and its treatment

PURPOSE

World Health Statistic Annuals between 1973 and 1982 show that mortality from cardiovascular and coronary heart disease fell significantly during this period. Against this background, the present review analyses results from trials of antihypertensive therapy in elderly hypertensives.

STUDY SELECTION

The review examined available trials specifically devoted to testing the hypothesis that antihypertensive treatment in the elderly hypertensive can lead to a decrease in morbidity and mortality.

RESULTS OF DATA ANALYSIS

Different, randomly allocated, controlled trials have shown that a pharmacological reduction in blood pressure can reduce the incidence of cardiovascular events in the elderly to a similar extent as in young and adult hypertensive patients. Recent reviews have indicated, in contrast to previous suggestions, that the available antihypertensive agents do not have an age-dependent effect. Therefore the choice of antihypertensive therapy is more dependent on previous use or the presence of concomitant diseases.

CONCLUSIONS

Arterial hypertension is a risk factor in the elderly which can be reduced with pharmacological intervention.

The effects of nicardipine in elderly hypertensive patients

Hypertension becomes more prevalent with advancing age, and the hemodynamic pattern differs from that in younger patients. In the elderly, elevated blood pressure is primarily due to reduced compliance of large vessels, resulting in an increase in total peripheral resistance, but in younger subjects it mainly reflects an increase in cardiac output. Vasodilator drugs, such as calcium antagonists, might therefore be expected to be particularly effective in lowering blood pressure in the elderly. Clinical experience has confirmed the safety and antihypertensive efficacy of these drugs, with some workers suggesting that calcium antagonists are particularly effective in the elderly. A 6-month multicenter study involving 2,184 patients has shown a direct correlation between pretreatment blood pressure and the degree of blood pressure reduction observed during nicardipine treatment with or without other antihypertensive drugs. Isolated systolic hypertension was significantly reduced but diastolic blood pressure was not affected. The incidence of side effects among elderly hypertensive patients, both with and without concomitant disease, was slightly lower than in younger patients.

Nicorandil, a new vasodilator drug, in patients with essential hypertension

In 12 mild to moderate hypertensive patients we investigated the acute antihypertensive efficacy of three different doses of nicorandil, a new vasodilating agent which probably acts by increasing the potassium efflux from smooth muscle cells and causing a cellular hyperpolarization. After a 3-day placebo period the patients were given, according to a double-blind Latin-square randomized design, 10, 20 and 30 mg nicorandil as a single acute dose every other day. Blood pressure and the heart rate were measured in both supine and upright positions at various times for 24 h after the dosing; fractional urine collections were obtained at the end of the placebo period and after each active dose. All doses of nicorandil similarly and significantly (P less than 0.01) reduced supine blood pressure, with a peak after 4-6 h (10 mg: -21/-8 mmHg; 20 mg: -20/-9 mmHg; 30 mg: -29/-17 mmHg), and the effect was still present, though reduced, after 24 h; no change in the heart rate was observed. The results from the upright position were similar. There were no significant changes in urine volume and electrolyte excretion during the nicorandil administration. The three different doses of nicorandil caused similar acute blood pressure reductions without change in the heart rate, nor in the urine volume and urinary sodium.

Cardiovascular and renal effects of single administration of three different doses of isradipine in hypertensive patients. Dose-response curves of the different effects

The antihypertensive, humoral, and renal effects of acute single oral administration of placebo and isradipine, a new dihydropyridine calcium antagonist, at doses of 2.5 mg, 5.0 mg, and 7.5 mg once daily were investigated in 11 patients with mild-to-moderate uncomplicated essential hypertension. The patients maintained a constant daily intake of 100 mmol of sodium and 40 mmol of potassium. Placebo and isradipine were randomly administered to each patient, according to a Latin-square design, at intervals of at least 48 hours. The antihypertensive effect was dose-dependent and peaked at two hours after oral administration; changes at the lowest dose were already statistically significant (p less than 0.01). Increases in heart rate were mild and similar with all isradipine doses. Glomerular filtration rate and renal plasma flow showed a trend towards a dose-dependent rise; plasma renin activity was statistically increased (p less than 0.05) following the highest isradipine dose, whereas plasma aldosterone was unmodified. Isradipine resulted in a statistically significant rise (p less than 0.05) in sodium excretion and urine volume, which was similar with all active doses. In conclusion, the antihypertensive efficacy of isradipine is dose-dependent, whereas the natriuretic and diuretic effects are already at maximum following 2.5 mg per day, the lowest dose in this study.