Is there a rationale for combining angiotensin-converting enzyme inhibitors and calcium antagonists in cardiovascular disease?

Effects of verapamil slow release plus trandolapril combination therapy on essential hypertension

BACKGROUND

Fixed-dose combination antihypertensive therapy has been recommended for patients with essential hypertension who are unresponsive to monotherapy or as a first-line treatment.

OBJECTIVE

We investigated the effects of a fixed-dose combination of the phenylalkylamine-type calcium channel blocker verapamil slow release (SR)plus the angiotensin-converting enzyme inhibitor trandolapril on blood pressure (BP), serum lipid profile, urinary albumin excretion (UAE), left ventricular mass (LVM), and LVM index (LVMI), as well as the adverse events associated with this treatment.

METHODS

Patients aged 30 to 65 years with mild to moderate essential hypertension were included in the study. All of the patients received capsules containing combination treatment with verapamil SR 180 mg plus trandolapril 2 mg orally, daily for 12 weeks. Mean arterial pressure (MAP), systolic BP (SBP), diastolic BP (DBP), and heart rate (HR) were measured at baseline and at 4, 8, and 12 weeks of treatment. Serum lipid profile, UAE, LVM, LVMI, and body mass index (BMI) were determined at baseline and at the end of the study period. All patients underwent electrocardiography and echocardiography at baseline and week 12. The primary end point of the study was to achieve an SBP/DBP ≤140/≤90 mm Hg (ie, normotensive) during week 12. All adverse events were assessed as mild, moderate, or severe at each visit. According to the response rate at week 12, patients were divided into 2 groups: those who became normotensive (responders) or those who remained hypertensive (SBP/DBP >140/>90 mm Hg; nonresponders).

RESULTS

Forty-one patients (29 women, 12 men; mean [SD] age, 47.7 [7.8] years; mean [SD] BMI, 29.4 [3.5] kg/m(2)) were enrolled. The median durationof hypertension prior to enrollment was 5 months. Mean MAP, SBP, DBP, UAE, total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), LDL-C/highdensity lipoprotein cholesterol (HDL-C) ratio, LVM, LVMI, and BMI decreased significantly after 12 weeks of combination treatment; HR and triglyceride level did not change significantly. Treatment-related adverse events occurred in 31.7% of patients, and none were severe or caused any patient to withdraw from the study. The most common adverse events were cough, constipation, headache, and dryness in the throat. Microalbuminuria, which may be a marker of endothelial dysfunction, was found in 7 (17.1%) patients at baseline and regressed significantly after 12 weeks.

CONCLUSIONS

In this study population, the fixed-dose combination of verapamil-trandolapril was an effective and well-tolerated antihypertensive therapy. This combination significantly reduced MAP, BP, TC, LDL-C, LDL-C/HDL-C ratio, UAE, LVM, and LVMI. Also, microalbuminuria decreased after this treatment. Verapamil-trandolapril may be useful in preventing microalbuminuria and left ventricular hypertrophy in patients with essential hypertension.

Combination therapy with renin-angiotensin system blockers: Will amlodipine replace hydrochlorothiazide?

Amlodipine is a highly effective and safe antihypertensive dihydropyridine calcium channel blocker. It is even more effective when used in combination with other antihypertensive medications, including hydrochlorothiazide. When antihypertensive calcium channel blockers were first introduced, evidence in the laboratory that they had some natriuretic properties was adduced to suggest that they would be "the diuretics of the 1990s." This turned out not to be the case. Because of its clinical efficacy, amlodipine is frequently used in fixed-dose combination products, but it is not likely to replace hydrochlorothiazide.

Beneficial effects of combined benazepril-amlodipine on cardiac nitric oxide, cGMP, and TNF-alpha production after cardiac ischemia

The aim of this study was to determine if myocardial inflammation is increased after myocardial ischemia and whether angiotensin-converting enzyme inhibitors, calcium channel blockers, or diuretics decrease mediators of inflammation in rats with induced myocardial ischemia. Changes in cardiac interstitial fluid (CIF) levels of nitric oxide metabolites (NOX), cyclic guanosine 3',5'-monophosphate (cGMP), angiotensin II (Ang II), and tumor necrosis factor-alpha (TNF-alpha) were monitored with/without oral administration of benazepril, amlodipine, combined benazepril-amlodipine, or hydrochlorothiazide. Using a microdialysis technique, levels of several mediators of inflammation were measured after sham operation or 30-minute occlusion of the left anterior descending coronary artery. Compared with sham animals, levels of CIF NOX and cGMP were decreased in animals with ischemia (P < 0.001). Benazepril or amlodipine significantly increased NOX levels (P < 0.05 vs. untreated ischemia), but only benazepril significantly increased cGMP (P < 0.05). Combined benazepril-amlodipine further increased CIF NOX and cGMP (P < 0.001), compared with either drug alone. CIF Ang II and TNF-alpha in sham animals did not change significantly. In animals with ischemia, CIF Ang II and TNF-alpha increased progressively. Amlodipine alone, benazepril alone, or combined benazepril-amlodipine significantly reduced TNF-alpha (P < 0.01 for monotherapies and P < 0.001 for combination therapy). Hydrochlorothiazide did not cause significant changes in NOX, cGMP, or TNF-alpha. Combination benazepril-amlodipine may be beneficial for managing cardiac ischemia.

Hydrogen peroxide acts as both vasodilator and vasoconstrictor in the control of perfused mouse mesenteric resistance arteries

BACKGROUND

Hydrogen peroxide (H2O2) plays a key role in the control of resistance artery (RA) tone and is hypothesized as an endothelial-derived hyperpolarizing factor.

METHODS

In this study, we investigated the effects of the same concentration of exogenous H2O2 on mouse mesenteric RA tone induced by intraluminal pressure, G-protein coupled receptor activation and KCl. RAs were cannulated in an arteriograph in the absence or presence of vasoconstrictors.

RESULTS

RA developed myogenic tone (MT) in response to stepwise pressure increases. Under phenylephrine, H2O2 induced a dose-dependent (1-50 micromol/l) vasodilation with maximum dilation at 50 micromol/l. H2O2 at 50 micromol/l induced a full dilation of RA under MT or contraction by phenylephrine that was independent of nitric oxide synthase, cyclooxygenase, endothelium and potassium channels iberiotoxin and apamin sensitive. The Ca2+ channel inhibitor, nimodipine, significantly blocked MT and also the contraction to phenylephrine and KCl. Under these conditions, H2O2 had no effect on RA diameter. Under KCl, the same concentration of H2O2 induced a potent vasoconstriction. This contraction involved p38 mitogen-activated protein-kinase activation but not ERK1/2.

CONCLUSIONS

These findings provide the first evidence showing that the same and low concentrations of H2O2 can act as a relaxing factor but also as a vasoconstrictor under conditions in which hyperpolarization is compromised.

The L-arginine-nitric oxide pathway in hypertension

Nitric oxide is involved in the regulation of resting vascular tone, adaptation of blood flow to metabolic demand of tissue, and adaptation of vessel diameter to volume of inflow, ie, flow-mediated dilation. Arterial hypertension is associated with an increased vascular tone of resistance vessels, a reduced compliance of conduit arteries, along with a thickening of the intima-media leading to vascular remodeling. Dysfunctional endothelium triggers such maladaptive processes. A reduced bioavailability of nitric oxide has been shown in hypertensive individuals dependent on the duration and severity of arterial hypertension. Angiotensin-converting enzyme inhibitors reverse endothelial dysfunction, whereas a concomitant reduction in significant cardiac events due to improved bioavailability has yet to be established. Long-term follow-up studies in individuals with manifest endothelial dysfunction and in offspring from hypertensive patients underscore the prognostic and genetic significance of a reduced nitric oxide bioavailability for the pathophysiology of arterial hypertension.

Effects of long-term treatment with verapamil on left ventricular function and myocardial blood flow in patients with dilated cardiomyopathy without overt heart failure

Myocardial blood flow (MBF) abnormalities are present in early stage dilated cardiomyopathy (DCM) and have been attributed to coronary microvascular abnormalities. The favorable effects of verapamil on coronary microcirculation might indicate its use in early stage DCM. We assessed the safety of long-term combination therapy of verapamil and enalapril and its effects on both left ventricular function and myocardial perfusion compared with enalapril alone in 18 patients with DCM (15 men, 3 women; mean age, 50+/-9 years) without overt heart failure (NYHA class I-II). At baseline and after 6 months of randomized treatment with either enalapril (10-20 mg) (nine patients, group 1) or enalapril (10-20 mg) and verapamil (120-240 mg) (nine patients, group 2), left ventricular function was assessed at rest, during handgrip, and during bicycle exercise by equilibrium radionuclide angiography. Mean MBF was measured at rest and after dipyridamole by positron emission tomography (PET) and 13N-ammonia as a flow tracer. At baseline, the two groups had reduced left ventricular ejection fraction at rest, which was further impaired during isometric exercise, but increased at peak bicycle exercise. MBF was similarly reduced in the two groups at rest and during dipyridamole. During treatment, no adverse events occurred in either group. After 6 months there was no significant difference in the main study variables either between the two groups or within each group before and after treatment. Long-term combination therapy with verapamil and enalapril is safe in patients with DCM without overt heart failure. Despite no favorable effect on myocardial perfusion, combined treatment prevented deterioration of left ventricular function, similarly to enalapril alone.

Inconsistencies in the classification of preventive interventions

BACKGROUND AND OBJECTIVE

Preventive measures are commonly classified into primary (prevention of a disease from occurring), secondary (screening of asymptomatic persons with a view of early detection and treatment of disease), and tertiary (treatment of patients with a view of palliation, cure, rehabilitation, prevention of relapse, or prevention of complications). The objective of the present survey was to assess the adherence to this classification in a sample of abstracts of scientific publications.

METHOD

We searched the literature (key terms prevention and primary, secondary, or tertiary) and identified 317 abstracts describing various preventive interventions. We tabulated the level of prevention as defined in the abstract, by what was done, to whom, and why.

MAIN FINDINGS

There was a considerable variability in the way the various levels of prevention were defined in the reviewed abstracts.

CONCLUSIONS

The definitions of the levels of prevention are not specific enough to be appropriately used by all. We suggest, therefore, to define clinical interventions by their objective, target population, and type ("reduction of mortality of patients with symptomatic ventricular ectopy by beta-blockers"), rather than in terms of level of prevention ("tertiary prevention of ventricular ectopy").

Effects of a novel calcium antagonist, benidipine hydrochloride, on platelet responsiveness to mental stress in patients with essential hypertension

The effects of a novel calcium antagonist, benidipine hydrochloride, on responses of platelets to mental stress were evaluated in nine patients with essential hypertension. Before and 12 weeks after the monotherapy with benidipine (2-4 mg/day), platelet aggregability and plasma beta-thromboglobulin were determined during rest and after a 10-min arithmetic stress. Before the treatment, arithmetic stress significantly increased platelet aggregability in response to adenosine diphosphate (ADP) and plasma beta-thromboglobulin level. Blood pressure, pulse rate, and plasma catecholamines also increased during arithmetic stress. The treatment with benidipine did not affect resting values of platelet functions, but attenuated significantly stress-induced alterations in primary aggregation to 1.0 microM ADP (34 +/- 4% to 40 +/- 3% before treatment vs. 32 +/- 2% to 34 +/- 3% after benidipine), ADP threshold for biphasic aggregation (2.2 +/- 0.4 to 1.8 +/- 0.3 microM before treatment vs. 2.2 +/- 0.3 to 2.2 +/- 0.4 microM after benidipine) and plasma beta-thromboglobulin level (74 +/- 16 to 104 +/- 15 ng/ml before treatment vs. 60 +/- 10 to 52 +/- 8 ng/ml after benidipine; p < 0.05 for Stress x Treatment interactions in all values). The pretreatment elevations in blood pressure and sympathetic activity with stress were not modified by benidipine treatment. In conclusion, the monotherapy with benidipine did not affect platelet function during the resting condition, but significantly suppressed the platelet activation induced by arithmetic stress in patients with essential hypertension.

Effect of verapamil on responses to endothelin-1 in aortic rings from streptozotocin-induced diabetic rats

In this study, we investigated the constrictor responsiveness to endothelin-1 (ET-1, 10-30 n m) of aortic rings (under 1 g resting tension in Krebs-Bicarbonate solution) from 8-weeks streptozotocin (STZ, 65 mg kg-1, i.p)-induced diabetic rats and vehicle-treated control rats. The maximum ET-1-induced contraction of the aorta in diabetic rats was increased by 150%, but the EC50 of ET-1 remained unchanged. Although in both groups, verapamil reduced the constrictor responses to ET-1 (diabetic group P<0.001, control group P<0.05), there were not any significant differences between PD2 values. These results suggest that verapamil inhibits ET-1-induced Ca2+ entry through the L-type channel and this effect did not change in diabetes mellitus.