Effects of diltiazem on cardiovascular responses during exercise in systemic hypertension and comparison with propranolol

Chronic Use of Antihypertensive Medications and Peak Exercise Blood Pressure in Adult Men and Women from the BALL ST Cohort

PURPOSE

To determine if individuals chronically (>1 yr) prescribed antihypertensive medications have a normal BP response to peak exercise compared with unmedicated individuals.

METHODS

Participants included 2555 adults from the Ball State Adult Fitness Longitudinal Lifestyle STudy cohort who performed a peak treadmill exercise test. Participants were divided into groups by sex and antihypertensive medication status. Individuals prescribed antihypertensive medications for >1 yr were included. Exaggerated and blunted SBP within each group was categorized using the Fitness Registry and the Importance of Exercise: A National Database (FRIEND) and absolute criteria as noted by the American Heart Association.

RESULTS

The unmedicated group had a greater prevalence ( P < 0.05) of blunted SBP responses, whereas the medicated group had a higher prevalence ( P < 0.05) of exaggerated SBP responses using both the FRIEND and absolute criteria. Peak SBP was higher ( P < 0.01) in medicated compared with unmedicated participants in the overall cohort when controlling for age and sex, but not after controlling for resting SBP ( P = 0.613), risk factors ( P = 0.104), or cardiorespiratory fitness ( P = 0.191). When men and women were assessed independently, peak SBP remained higher in the medicated women after controlling for age and resting SBP ( P = 0.039), but not for men ( P = 0.311). Individuals on beta-blockers had a higher peak SBP even after controlling for age, sex, risk factors, and cardiorespiratory fitness ( P = 0.022).

CONCLUSIONS

Individuals on antihypertensive medications have a higher peak SBP response to exercise. Given the prognostic value of exaggerated peak SBP, control of exercise BP should be considered in routine BP assessment and in the treatment of hypertension.

Relationship between left ventricular diastolic function at rest and exercise capacity in patients who have suffered a previous myocardial infarction

To assess whether left ventricular (LV) diastolic function is a determinant of exercise capacity in patients who have suffered a previous myocardial infarction (MI), we investigated the relationship between maximum exercise duration and resting LV diastolic function in 65 MI patients. Each patient underwent both a symptom-limited exercise test and LV biplane angiography with simultaneous high-fidelity pressure measurements. LV relaxation was assessed by the time constants (T1/e and T1/2) of isovolumic pressure decay, and LV diastolic distensibility was assessed by the LV end-diastolic volume (V) index-pressure (P) ratio. The time constants of relaxation did not correlate with maximum exercise capacity (r = -0.19 for T1/e, NS; r = - 0.17 for T1/2, NS). LV diastolic distensibility also did not correlate with exercise capacity (r = - 0.08, NS). These results suggest that the resting LV diastolic dysfunction is unlikely to be the principal cause of exercise intolerance in MI patients without congestive heart failure.

The Diltiazem Different Doses Study--a dose-response study of once-daily diltiazem therapy for hypertension

The objective was to evaluate the dose-related efficacy/tolerance profile of 240, 300, 360, and 420 mg diltiazem slow-release, once-daily (OD) doses, with emphasis on the 300 mg dose. The study was randomized and double-blinded with a 36-week parallel, two-branched, cross-over design after a single-blind, run-in period of 4 weeks on placebo and 6 weeks on 300 mg diltiazem OD. Each branch included six 6-week active treatment periods with 180, 240, and 300 mg tablets, one or two tablets OD. Participants were men and postmenopausal women, aged 40-70 years, with uncomplicated primary hypertension (WHO stages I and II) and a supine diastolic blood pressure of 95-115 mm Hg in the absence of antihypertensive medication. A total of 138 patients from various clinics participated in the study. All were included in the intention to treat analysis, and 117 patients were included in the per protocol analysis. Criteria for evaluation were blood pressure, heart rate, and response rate, as well as plasma diltiazem and metabolite M1 concentration before morning dose. Well-being of the patients and adverse events were recorded. Electrocardiogram and standard laboratory tests were obtained. Analysis of variance was used for statistical calculations. Supine blood pressures and response rates in the per protocol analysis were 161.2/97.0 for placebo (29.1%), 155.2/ 92.8 for 240 mg (54.7%), 153.8/91.6 for 300 mg (55.6%), 155.5/92.0 for 360 mg (59.0%), and 152.0/90.5 for 420 mg (63.2%) of diltiazem OD. The intention to treat analysis was very similar to the per protocol analysis. There was a small but statistically significant decrease in heart rate for all doses of diltiazem OD compared to placebo. A linear relationship existed between the dose and the plasma concentration of both diltiazem and metabolite M1, as well as a dose-response relationship. Diltiazem OD in the dose range 240-420 mg was generally well tolerated and not differently perceived from the placebo treatment except for ankle edema (2-6%). The study shows that OD diltiazem is significantly superior to placebo for mild to moderate hypertension and that the effect is large enough to be clinically valuable. It also shows that there is a linear dose-response relationship for diltiazem between 240 and 420 mg.

Diltiazem: ten years of clinical experience in the treatment of hypertension

Diltiazem hydrochloride is a benzothiazepine derivative calcium-channel blocker with proven antianginal and antihypertensive capabilities. Its primary mechanism of action is vasodilatation, which results in diminished vascular resistance and improved perfusion to various vascular beds and target organs. The antihypertensive efficacy of diltiazem in various demographic groups has been studied and compared with diuretics, beta-blockers, angiotensin-converting enzyme inhibitors, and other calcium-channel blockers. These studies have shown that the antihypertensive effect of diltiazem is similar to that of the other therapies. Diltiazem does not adversely affect electrolytes or carbohydrate or lipid metabolism, and it may have beneficial effects on the heart and kidneys. Diltiazem reduces myocardial hypertrophy and exerts antianginal effects on the heart through coronary vasodilation and reduction in the blood pressure double product. Diltiazem improves renal perfusion and attenuates proteinuria. These effects may be helpful in limiting the progression of renal injury. Overall, the efficacy and tolerability of diltiazem, as well as its salutary effects on the heart and kidneys, make it an important therapeutic consideration for patients with hypertensive disease.

Modification of exercise performance by sharp reduction of blood pressure. A study in patients with uncomplicated hypertension

We evaluated exercise performance in 14 patients with uncomplicated essential hypertension 1 h after the administration of a single dose of placebo, nifedipine (20 mg), captopril (50 mg), and propranolol (80 mg). Drugs were administered at the same time of day following a randomized, double-blind protocol. Mean resting blood pressure (+/- SE) was 135 +/- 3 mm Hg with placebo administration, 118 +/- 4 with captopril, 110 +/- 4 with nifedipine, and 115 +/- 5 with propranolol and increased with exercise to 163 +/- 4, 146 +/- 3, 136 +/- 4, 136 +/- 4, respectively. Oxygen consumption at peak exercise and at ventilatory anaerobic threshold (VAT) was 25.2 +/- 1.1 and 18.1 +/- 1.0 ml/min/kg with placebo. Only propranolol (-2.3 ml/min/kg) decreased peak exercise oxygen consumption. Oxygen consumption at VAT was reduced by nifedipine and propranolol but unaffected by captopril. The effects on exercise capacity of blood pressure reduction in hypertensive patients are dependent on the drug utilized and are not related to the amount of blood pressure reduction. The lowered oxygen consumption at VAT observed with nifedipine and propranolol, and not with captopril, might be due to an excessive downward shift of the muscle perfusion pressure--oxygen consumption relationship which might take place during exercise.

Clinical experience with a once-daily, extended-release formulation of diltiazem in the treatment of hypertension

Although calcium channel blockers were only recently approved for antihypertensive therapy, 10 years of data have demonstrated their beneficial effects. Among the available calcium channel blockers, diltiazem hydrochloride appears to have a highly favorable side-effect profile. A new, extended-release formulation of diltiazem has been developed for the treatment of essential hypertension. The safety and efficacy of various once-daily doses of this new formulation were assessed in two multicenter studies. The first study was a dose-ranging trial of 275 patients with mild-to-moderate hypertension. Patients were randomly assigned to once-daily diltiazem (120, 240, 360, or 480 mg) or placebo for a 4-week, double-blind treatment period. A patient subgroup underwent ambulatory blood pressure monitoring (ABPM) twice. Once-daily diltiazem (dose range, 240-480 mg) significantly lowered trough systolic and diastolic blood pressure in a clearly dose-related fashion. ABPM results demonstrated consistent decreases in systolic and diastolic blood pressure throughout the 24-hour dosing interval. Dosages greater than or equal to 240 mg/day provided trough drug blood levels within the therapeutic range (i.e., greater than or equal to 40 ng/mL). The second study was a forced-escalation trail of 115 patients with mild-to-moderate hypertension. Patients were randomized to treatment with either placebo or escalating dosages of diltiazem (180 mg/day for 2 weeks, 360 mg/day for 2 weeks, and then 540 mg/day for 2 weeks). Statistically significant (p less than 0.01) reductions in supine systolic and diastolic blood pressure were observed with the 360 mg/day and 540 mg/day dosages. Dose escalations resulted in incremental blood pressure reductions and an increase in the percentage of responders. There was a significant correlation between diltiazem peak and trough plasma concentrations and antihypertensive effects in both studies, supporting the 24-hour efficacy of this extended-release formulation. Diltiazem administered once daily was found to be safe and well tolerated by the patients in these studies; adverse events were generally mild, with an incidence similar to placebo. Results indicate that this new extended-release formulation of diltiazem, administered once daily in doses greater than 120 mg, effectively lowers systolic and diastolic blood pressure in patients with mild-to-moderate essential hypertension.

Exercise performance in patients with uncomplicated essential hypertension. Effects of nifedipine-induced acute blood pressure reduction

In untreated patients with uncomplicated essential hypertension, exercise induces an abnormal increase in blood pressure; the influences of this increase on exercise were evaluated by a cardiopulmonary exercise test (CPX) performed in control conditions (step 1) and during acute blood pressure reduction (step 2). Patients were classified as (1) normotensive (resting diastolic blood pressure [BPd] less than 90 mm Hg; n = 14), (2) mildly hypertensive (BPd of 90 to 104 mm Hg; n = 9), and (3) moderately to severely hypertensive (BPd greater than or equal to 105 mm Hg; n = 16). For the three groups, peak mean blood pressure during exercise was 125 +/- 5 mm Hg (mean +/- SEM), 144 +/- 3 mm Hg (p less than 0.01 vs normotensive), and 161 +/- 4 mm Hg (p less than 0.01 vs normotensive and p less than 0.01 vs mild hypertension), respectively. Oxygen consumption (VO2) at peak exercise and at ventilatory anaerobic threshold was 26.1 +/- 1.1 and 17.2 +/- 0.5 ml/min/kg, 25.4 +/- 1.1 and 16.9 +/- 0.8 ml/min/kg, and 26.4 +/- 1.3 and 17.5 +/- 1.2 ml/min/kg in normotensive subjects, those with mild hypertension, and those with moderate to severe hypertension, respectively. Fourteen normotensive subjects, six with mild hypertension, and nine with moderate to severe hypertension participated to step 2 (nifedipine vs placebo, double-blind crossover). Nifedipine reduced blood pressure at rest and at peak exercise in those with hypertension. Peak exercise VO2 was unaffected by nifedipine in both normotensive subjects and those with hypertension. With nifedipine, ventilatory anaerobic threshold occurred earlier and at a lower VO2 in mild and in moderate to severe hypertension (delta VO2 = -1.9 and -2.4 ml/min/kg, respectively). These findings might be due to nifedipine-induced redistribution of blood flow during exercise and might be the reason for the complaint of weakness after blood pressure reduction in hypertensive subjects.

Hemodynamic effects of Ro 23-6152 in patients with essential hypertension

In a double blind study 8 patients with uncomplicated essential hypertension received in random order single oral doses of placebo and 10, 30 and 80 mg Ro 23-6152, a novel calcium entry blocker, on 4 different days. Patients were assessed 15 min before dosing and at several time intervals over the following 6 h. Ro 23-6152 30 and 80 mg induced a significant decrease (mean maximum 7 mmHg.1-1.min-1) in total peripheral resistance, while cardiac output, stroke volume and heart rate were slightly increased (mean maximum 0.51.min-1, 10 ml, 5 beats.min-1, respectively) but not significantly so. Systolic blood pressure decreased significantly (5 to 10 mmHg) from 0.5 to 6 h after the 80 mg dose. After the 10 and 30 mg doses the decreases in systolic pressure were not significant. Diastolic blood pressure and mean arterial blood pressure were non-significantly decreased (mean maximum 7 mmHg) after all doses. The PQ interval was also non-significantly increased by no more than 20 ms. It appears that the main hemodynamic effect of Ro 23-6152 in hypertensive patients is a decrease in peripheral resistance. The antihypertensive effect, at least in this short term study, was only modest, probably because the fall in peripheral resistance was partly compensated by an increase in cardiac output.

Effects of diltiazem on long-term outcome after acute myocardial infarction in patients with and without a history of systemic hypertension. The Multicenter Diltiazem Postinfarction Trial Research Group

The effect of diltiazem on long-term outcome in patients with acute myocardial infarction with and without a history of systemic hypertension was investigated in 2,466 patients using the Multicenter Diltiazem Postinfarction Trial data-base. The baseline variables were comparable in the diltiazem and placebo-treated patients within the groups with and without hypertension. The initial 60-mg dose of diltiazem was associated with a significant (p less than 0.001) but modest (3%) reduction in blood pressure and heart rate in both groups with and without hypertension. Univariate and multivariate analyses revealed a meaningful overall reduction in first recurrent cardiac events (cardiac death or nonfatal reinfarction, whichever occurred first) and cardiac death in patients with hypertension treated with diltiazem compared with results in those treated with placebo. Similar effects were not observed in patients without a history of hypertension. When first recurrent cardiac events were used as the end point, the diltiazem:placebo hazard ratio (95% confidence limits) was 0.77 (0.58, 1.01) for the total hypertension group, and 0.67 (0.47, 0.96) and 1.32 (0.83, 2.10) for patients with hypertension with and without pulmonary congestion during the acute infarction, respectively. Similar results were observed using cardiac death as the end point. Beta blockers had a negligible effect on the hypertension-diltiazem relation. These findings suggest that diltiazem may exert a long-term beneficial effect in most patients with hypertension who do not have pulmonary congestion during an acute infarction, and a detrimental effect in the minority who have pulmonary congestion.

Hypertension

In brief When exercise alone does not NMM control hypertension, a medical ISMS regimen can be used in conjunction with exercise or other nonpharmacologic interventions. Diuretics, beta blockers, calcium antagonists, and angiotensin-converting enzyme (ACE) inhibitors are widely used to treat hypertension. ACE inhibitors and calcium antagonists are good choices for exercising patients because they do not limit exercise performance and have few side effects. The author gives guidelines for changing the regimen from exercise alone to exercise and medication, and for stepping down from medical therapy.

Calcium channel antagonists. Part III: Use and comparative efficacy in hypertension and supraventricular arrhythmias. Minor indications

The major antihypertensive mechanism of calcium antagonists is by decreasing the systemic vascular resistance, modified by the counter-regulatory responses of the baroreflexes and the renin-angiotensin-aldosterone system. In severe hypertension, the concept that calcium overload of the vascular myocyte could precipitate or aggravate peripheral vasoconstriction provides a logical basis for the use of these agents as first choice therapy; nifedipine, especially, has been well tested. As monotherapy for mild to moderate hypertension each of the three first-generation agents compares well with beta-blockers. Calcium antagonists may have a special role in the therapy of certain patient groups (elderly, black) or in those subjects whose life style involves intense physical or mental exertion (hemodynamics better maintained than with beta-blockade) or in patients with early end-organ damage such as left ventricular hypertrophy or renal insufficiency. However, the goal blood pressure may not be reached during monotherapy so that drug combinations may be required. Further indications for these compounds are as follows. Verapamil and diltiazem are frequently used in supraventricular tachycardias including acute and chronic atrial fibrillation. In the arrhythmias of the Wolff-Parkinson-White syndrome, there is the potential danger of provocation of anterograde conduction. Further indications for calcium antagonists, still under evaluation, include congestive heart failure (controversial), hypertrophic cardiomyopathy (verapamil), primary pulmonary hypertension (high doses required), Raynaud's phenomenon (nifedipine and diltiazem effective), peripheral vascular disease (proof not yet documented), cerebral insufficiency and subarachnoid hemorrhage (nimodipine promising), migraine, exertional bronchospasm, renal disease, atherosclerosis (experimental), and primary aldosteronism (nifedipine inhibits aldosterone release). Second-generation agents include dihydropyridines, such as nitrendipine, nicardipine, felodipine, amlodipine, nisoldipine, nimodipine, and isradipine. From these will be selected agents that are longer acting and provide higher vascular selectivity. New preparations of existing agents include slow-release formulations of nifedipine, verapamil, and diltiazem. Minor side effects include those caused by vasodilation (flushing and headaches), constipation (verapamil), and ankle edema. Serious side effects are rare and result from improper use of these agents, as when intravenous verapamil is given to patients with sinus or atrioventricular nodal depression from drugs or disease, or nifedipine to patients with aortic stenosis. The potential of a marked negative inotropic effect is usually offset by afterload reduction, especially in the case of nifedipine. Yet caution is required when calcium antagonists, especially verapamil, are given to patients with myocardial failure unless caused by hypertensive heart disease. Drug interactions of calcium antagonists occur with other cardiovascular agents such as alpha-adrenergic blockers, beta-adrenergic blockers, digoxin, quinidine, and disopyramide.(ABSTRACT TRUNCATED AT 400 WORDS)

Calcium antagonists and their potential for antihypertensive therapy

Calcium antagonists are potent arterial vasodilators devoid of relevant chronic sympathetic reflex activation and sodium and volume retention. This favorable hemodynamic profile of action renders them suitable for monotherapy of hypertension where they act to reduce an enhanced, calcium-influx-dependent vasoconstrictor mechanism which may be brought about by altered smooth muscle cation handling and increased intracellular free calcium concentrations. Clinical studies have proved their efficacy, safety, and good tolerability alone or in combination with other drugs in uncomplicated hypertension where they are particularly effective in older and low-renin and possibly black patients. These properties and their efficacy in the treatment of severe and accelerated hypertension or hypertensive emergencies make them a valuable addition to already available drug therapy.

Effect of calcium channel blockade and beta-adrenoceptor blockade on short graded and single-level endurance exercises in normal men

The effect of verapamil (240 mg) on exercise capacity was studied during a short graded and a single-level endurance exercise test in 12 normal volunteers; it was compared to the effects of atenolol (100 mg x day-1). Intake of verapamil, atenolol and placebo, administered according to a randomized, double-blind cross-over design, was started 3 days before the exercise tests. Compared to placebo, verapamil did not affect peak oxygen uptake in the graded test or exercise duration in the endurance test. Heart rate, systolic blood pressure, rating of perceived exertion and respiratory data at submaximal and peak exercise were unaffected in either test. On the other hand atenolol reduced maximal oxygen uptake by 5% (p less than 0.001) and endurance exercise duration by 17% (p less than 0.05). Besides marked decreases in heart rate and systolic blood pressure during the two types of exercise, atenolol also reduced oxygen uptake at submaximal exercise levels and it increased the rating of perceived exertion (p less than 0.05), the latter only during the endurance exercise test.

Drug treatment of hypertension

There are several first choices for the treatment of mild and moderate hypertension. The selection of a drug may be influenced by concomitant pathology, with positive indications for particular drugs, e.g. coexistent angina, indicating use of a beta-receptor blocking drug or calcium antagonist; fluid retention indicating a diuretic; or contraindication e.g. asthma, and beta-adrenoceptor blocking drugs. beta-Adrenoceptor blocking drugs have the advantage of a long history and of possibly being cardioprotective following myocardial infarction, but they have not yet been established as primary preventive agents in hypertensive patients. The alpha-receptor blocking drugs have the advantage of favourably affecting lipid profile and blood pressure. Therefore, there may be advantages in the use of combined alpha- and beta-blockade. The diuretics, which have the advantage of being inexpensive, are widely used but long term metabolic effects, particularly hypokalaemia, cause concern. This is correctable by co-administration of a potassium sparing diuretic and often preventable by using low doses of the diuretic. Diet may be important as hypokalaemia appears to be less of a problem where potassium intake is high. Experience with calcium antagonists is widening but the use of converting enzyme inhibitors is more limited, and some physicians are less ready to use them as first choice in mild hypertension at present. Drugs like methyldopa, clonidine, the adrenergic neurone inhibitory drugs are now used more as reserve agents. More severe cases of hypertension may require drugs from 2 of the 3 major groups: beta-blocking drugs, vasodilators and diuretics. In some cases, drugs from each of these 3 groups will be required.

Exercise stress test in young hypertensive patients. Response to vasodilators (prazosin) vs. beta-blocker (atenolol) agents

Dynamic response of arterial blood pressure during exercise has been studied in 40 normotensive young subjects and 20 mild hypertensive young patients (20-40 years of age). Hypertensive patients were treated with atenolol (beta blocker) and prazosin (vasodilator). Both groups underwent maximal exercise stress test. A double-blind nonrandomized study was practiced in hypertensive patients with placebo, prazosin (3 mg/12 h), and atenolol (100 mg/24 h). Heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), and exercise duration (ED) were analyzed. All parameters remained stable in both groups. The hypertensive patients showed an increase in maximum SBP more than 230 mmHg during the placebo phase. This same group showed a significant increase in HR at rest two hours after administration of prazosin. Atenolol produced a significant reduction in HR both during rest and exercise. Both drugs produced a significant decrease in SBP and DBP (at rest and exercise). We conclude that exercise test is a noninvasive procedure that could distinguish mild arterial hypertension. The dynamic changes of arterial blood pressure can be controlled with prazosin (3 mg/12 h) or 1 daily intake of 100 mg atenolol.

Comparison of diltiazem and atenolol in young, physically active men with essential hypertension

The antihypertensive efficacy and effect on maximal exercise performance of diltiazem was evaluated and compared with atenolol in patients specifically selected on the basis of their being young and physically active. Diltiazem (sustained-release preparation, 90 mg twice daily) was administered to 14 patients (aged 33 +/- 2 years) and atenolol (50 mg once daily) to 13 patients (aged 30 +/- 2 years) with essential hypertension in a 16-week randomized, double-blind, parallel study. The 2 drugs had comparable antihypertensive effects at rest, with mean decreases of 18 and 17 mm Hg (p less than 0.001) for supine and standing diastolic blood pressure (BP), respectively, during diltiazem treatment, and mean decreases of 21 and 18 mm Hg (p less than 0.001) during atenolol treatment. During maximal graded exercise testing, systolic BP, diastolic BP, heart rate and heart rate-BP product were significantly reduced by both drugs. However, the reductions in systolic BP, heart rate and heart rate-BP product during exercise were considerably greater (p less than 0.001) with atenolol than with diltiazem. Maximal exercise performance was essentially unchanged with diltiazem and slightly (3%, p less than 0.05) reduced with atenolol. Thus, diltiazem is effective and well-tolerated single therapy for young patients with mild to moderate essential hypertension who lead a physically active life style and compares favorably with atenolol.

Diltiazem versus propranolol in essential hypertension: responses of rest and exercise blood pressure and effects on exercise capacity

Both beta-blocking and calcium channel-blocking drugs are being used with increasing frequency as initial therapy for essential hypertension. The present study was designed to compare the antihypertensive effects of a beta-blocking drug, propranolol, with a calcium channel-blocking drug, diltiazem, at rest and during upright bicycle exercise and to determine whether exercise capacity is altered by these therapies. Twenty-one patients with uncomplicated systemic hypertension and a diastolic blood pressure (BP) of 95 to 110 mm Hg without medication were randomly assigned to propranolol or diltiazem therapy in a double-blind manner. The total daily dosages were titrated as needed, from 160 to 480 mg of propranolol (mean 371 mg) and 120 to 360 mg of diltiazem (mean 307 mg) over 12 weeks, and the titrated dose was maintained for 4 additional weeks. Both drugs significantly reduced supine BP (from 149 +/- 14/101 +/- 4 to 136 +/- 17/89 +/- 10 mm Hg with propranolol and from 157 +/- 14/103 +/- 4 to 144 +/- 13/93 +/- 8 with diltiazem. Only diltiazem reduced BP during submaximal exercise, but both agents produced significant responses during maximal exercise. Diltiazem had no effect on maximal heart rate, exercise duration or O2 uptake, whereas propranolol reduced maximal VO2 from 27 +/- 6 to 22 +/- 6 ml/min/kg (p less than 0.01) and also shortened duration of exercise. Propranolol, despite its effects on heart rate, maintained the workload VO2 relation at submaximal loads, suggesting an increased oxygen delivery. However, these adaptive mechanisms appear to be insufficient during maximal effort.

Exercise and antihypertensive therapy

The effects of exercise on central hemodynamic mechanisms and the changes induced by treatment have been studied invasively in approximately 500 men with essential hypertension. In patients with mild hypertension, the increase in blood pressure (BP) during dynamic exercise is similar to that seen in normal subjects, but in patients with severe hypertension it is steeper. During dynamic exercise total peripheral resistance is increased in all categories of hypertensive patients, including young subjects with apparently "normal" resistance at rest. The increase in stroke volume in transition from rest to exercise is subnormal, probably reflecting increased stiffness in the left ventricle. Static exercise causes dramatic increase in systolic as well as diastolic BP. Most antihypertensive agents control BP similarly during exercise and at rest. The hemodynamic mechanisms, however, differ greatly. The beta blockers induce a long-term reduction in cardiac output, muscle blood flow and, frequently, endurance capacity. In contrast, alpha-receptor blockers, calcium antagonists and angiotensin converting enzyme inhibitors all reduce total peripheral resistance and do not decrease blood flow. Increase in endurance time has been reported with long-term calcium antagonist treatment. It would seem logical to select an antihypertensive drug that does not reduce exercise capacity when treating physically active patients with mild and moderate hypertension.

[Prevention of hypertensive attacks after carotid surgery. The value of nifedipine and diltiazem]

A randomized study was carried out to determine whether postoperative administration of either intranasal nifedipine or intravenous diltiazem was effective in preventing hypertensive episodes after carotid endarterectomy. Sixty-three consecutive patients undergoing this surgery were randomly assigned to three groups (n = 21): control (C), nifedipine (N) and diltiazem (D). Anaesthesia was induced with flunitrazepam (0.02 mg X kg-1), fentanyl 6 micrograms X kg-1 and pancuronium (0.1 mg X kg-1), and maintained by N2O/O2 (50%), additional fentanyl and halothane or enflurane when warranted. Postoperatively, patients were warned whilst under mechanical ventilation in a recovery room. Upon arrival in the recovery room, intranasal nifedipine (10 mg) was given to patients included in group N, while patients from group D received an intravenous dose of 0.3 mg X kg-1 of diltiazem, followed by a continuous infusion of 3 micrograms X kg-1 X min-1 until 15 min after extubation. No preventive treatment was given to patients in group C. If postoperative systolic blood pressure rose to more than 180 mmHg, 10 mg of nifedipine were administered intranasally. During the postoperative period, 13 patients from group C, 5 from group N and 4 from group D exhibited hypertensive episodes (systolic blood pressure greater than 180 mmHg or diastolic blood pressure greater than 100 mmHg). Intranasal administration of 10 mg nifedipine led to the normalization of blood pressure in 20 out of these 22 patients. This study confirmed the high incidence of hypertensive attacks after carotid endarterectomy, and showed that prophylactic administration of nifedipine or intravenous diltiazem was highly effective in preventing such hypertensive episodes.

Immediate and short-term hemodynamic effects of diltiazem in patients with hypertension

The immediate effects of intravenous diltiazem effects and short-term (4 weeks) of the oral drug on systemic and regional hemodynamics, cardiac structure, and humoral responses were evaluated by previously reported methods in nine patients with mild-to-moderate essential hypertension and in one patient with primary aldosteronism. Diltiazem was first administered in three intravenous doses of 0.06, 0.06, and 0.12 mg/kg, respectively; patients were then treated for 4 weeks with daily doses ranging from 240 to 360 mg (average 300 mg). Intravenous diltiazem immediately reduced mean arterial pressure (from 115 +/- 3 to 96 +/- 3 mm Hg; p less than .01) through a fall in total peripheral resistance index (from 37 +/- 3 to 23 +/- 2 U/m2; p less than .01) that was associated with an increase in heart rate (from 66 +/- 2 to 77 +/- 3 beats/min; p less than .01) and cardiac index (from 3.3 +/- 0.3 to 4.3 +/- 0.4 liters/min/m2; p less than .01). These changes were not associated with changes in plasma levels of catecholamines or aldosterone or in plasma renin activity. After 4 weeks the significant decrease in mean arterial pressure persisted (104 +/- 3 mm Hg; p less than .01) and there were still no changes in the humoral substances or plasma volume. Renal blood flow index increased (from 368 +/- 52 to 462 +/- 57 ml/min/m2; p less than .01) and renal vascular resistance index decreased (from 0.37 +/- 0.06 to 0.26 +/- 0.04 U/m2; p less than .01), while splanchnic hemodynamics did not change.(ABSTRACT TRUNCATED AT 250 WORDS)

Antihypertensive therapy with calcium-channel blockers: comparison with beta blockers

As a result of concern about the safety and long-term toxicity of diuretics, there is a growing trend toward the use of alternative agents as initial therapy in essential hypertension. Worldwide, beta blockers and vasodilators, especially the calcium-channel blockers, are the most commonly used alternative agents. Several studies comparing these 2 classes of medications are reviewed. These studies indicate that verapamil, nifedipine and diltiazem are all comparable in efficacy to beta blockers. When combined, calcium-channel blockers and beta blockers produce additive responses. These agents may differ in the relation between the magnitude of their antihypertensive effect and patients' pretreatment plasma renin activity and age. Younger persons and those with high plasma renin activity tend to respond better to beta blockers; older subjects and those with low plasma renin activity are more consistently responsive to calcium-channel blockers. The choice of agent should be individualized, based upon accompanying illnesses, adverse-effect profile and demographic factors.

Effects of diltiazem on serum lipids, exercise performance and blood pressure: randomized, double-blind, placebo-controlled evaluation for systemic hypertension

Treatment of hypertension with diuretics, beta blockers and alpha blockers may be associated with adverse effects on exercise performance, serum lipids and blood chemistries, as well as with orthostatic effects and fluid retention. A randomized, double-blind, placebo-controlled trial of a sustained-release preparation of diltiazem as sole therapy for moderate essential hypertension was conducted. Diltiazem was administered 2 times a day (360 mg/day) to 16 patients and placebo to 14 patients in a 12-week study. Average supine blood pressure with diltiazem therapy fell from 161/100 to 144/87 mm Hg without fluid retention or orthostatic effects. In an open-label study, patients from the placebo and diltiazem groups continued with diltiazem therapy. At an average of over 8 months, supine blood pressure on diltiazem was 147/88 mm Hg, and after withdrawal to single-blind placebo, average supine blood pressure increased to 173/104 mm Hg. All changes were significant compared with baseline and placebo (p less than 0.01). On diltiazem therapy, maximal treadmill exercise was increased by an average of 55 seconds (p less than 0.01), whereas heart rate, blood pressure and double product (heart rate X blood pressure) were reduced at submaximal exercise, and heart rate and double product were reduced at maximal exercise. No changes in serum glucose, potassium or uric acid were found. No adverse effects on serum lipids occurred. Diltiazem treatment was associated with an increase in high-density lipoprotein cholesterol (52 to 60 mg/dl, p less than 0.006) and a decrease in total cholesterol:high-density lipoprotein cholesterol ratio (4.7 to 4.2, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of diltiazem and atenolol in angina

Diltiazem was compared to atenolol in a double-blind trial involving 78 patients suffering from coronary heart disease. Following a 2 week control period, patients were randomly allocated to 6 weeks treatment with one or the other drug. The patients themselves made daily records of anginal attacks, trinitrate requirements, well-being and exercise tolerance. With both drugs there were highly significant reductions in the anginal attack rate and trinitrate requirements, and significant improvement on the other measures. However, there were no significant between drug differences. The incidence of side effects with diltiazem was very low and no patient had to omit treatment for this reason, although three patients did so on atenolol.

Alternative pharmacologic approaches to the initial management of hypertension

Recent clinical trials in hypertension report more deaths due to coronary heart disease in mild hypertensives who received aggressive antihypertensive drug therapy and achieved better blood pressure control. Subset analyses of these trials suggest that diuretic therapy may have contributed to this outcome, possibly through a reduction in serum potassium or an elevation in serum lipids. Because of this, patients with an abnormal pretreatment electrocardiogram, history of myocardial infarction, unstable coronary heart disease, or diuretic-induced hyperlipidemia or hypokalemia unresponsive to management are candidates for alternative antihypertensive agents. A review of the literature suggests that most of the currently available beta-blockers, the alpha 1-antagonist prazosin, the angiotensin-converting enzyme inhibitor captopril, and the vasodilator hydralazine are effective alternatives to thiazide therapy in the initial management of hypertension and are recommended for particular subgroups of patients. Monotherapy with the centrally and peripherally acting sympatholytic agents is not recommended because of the frequent side effects encountered and the inferior hypotensive efficacy reported. Calcium channel blocking agents also appear to be suitable alternatives to thiazides in hypertension, but more experience with these is needed. Alternative pharmacologic agents may be selected on the basis of age, and, to a lesser extent, race.

Calcium channel blockers in emergency medicine

Diltiazem, nifedipine, and verapamil inhibit calcium entry into cells via different mechanisms with different pharmacologies. They display different relative effects on different cardiovascular functions, a complex interplay of direct actions and adrenergic reflexes. Peripheral arterial vasorelaxation causes adrenergic reflex activity which opposes their direct negative chronotropic, dromotropic, inotropic, and hypotensive actions. Verapamil's most potent activity is electrophysiologic, and nifedipine's effects are hemodynamic; diltiazem acts like a less-potent combination of verapamil and nifedipine. All three drugs are efficacious in angina. These three drugs may not be interchangeable in all patients, but individualization of therapy is possible. Future indications for calcium channel blocker therapy may include hypertrophic cardiomyopathy, cerebral vasospasm, migraine headaches, pulmonary hypertension, asthma, esophageal spasm, intestinal ischemia, Raynaud's phenomenon, dysmenorrhea, and premature labor.