The influence of antihypertensive therapy on the structural arteriolar changes in essential hypertension: different effects of enalapril and hydrochlorothiazide

First-line drugs inhibiting the renin angiotensin system versus other first-line antihypertensive drug classes for hypertension

BACKGROUND

This is the first update of a Cochrane Review first published in 2015. Renin angiotensin system (RAS) inhibitors include angiotensin converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs) and renin inhibitors. They are widely prescribed for treatment of hypertension, especially for people with diabetes because of postulated advantages for reducing diabetic nephropathy and cardiovascular morbidity and mortality. Despite widespread use for hypertension, the efficacy and safety of RAS inhibitors compared to other antihypertensive drug classes remains unclear.

OBJECTIVES

To evaluate the benefits and harms of first-line RAS inhibitors compared to other first-line antihypertensive drugs in people with hypertension.

SEARCH METHODS

The Cochrane Hypertension Group Information Specialist searched the following databases for randomized controlled trials up to November 2017: the Cochrane Hypertension Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (from 1946), Embase (from 1974), the World Health Organization International Clinical Trials Registry Platform, and ClinicalTrials.gov. We also contacted authors of relevant papers regarding further published and unpublished work. The searches had no language restrictions.

SELECTION CRITERIA

We included randomized, active-controlled, double-blinded studies (RCTs) with at least six months follow-up in people with elevated blood pressure (≥ 130/85 mmHg), which compared first-line RAS inhibitors with other first-line antihypertensive drug classes and reported morbidity and mortality or blood pressure outcomes. We excluded people with proven secondary hypertension.

DATA COLLECTION AND ANALYSIS

Two authors independently selected the included trials, evaluated the risks of bias and entered the data for analysis.

MAIN RESULTS

This update includes three new RCTs, totaling 45 in all, involving 66,625 participants, with a mean age of 66 years. Much of the evidence for our key outcomes is dominated by a small number of large RCTs at low risk for most sources of bias. Imbalances in the added second-line antihypertensive drugs in some of the studies were important enough for us to downgrade the quality of the evidence.Primary outcomes were all-cause death, fatal and non-fatal stroke, fatal and non-fatal myocardial infarction (MI), fatal and non-fatal congestive heart failure (CHF) requiring hospitalizations, total cardiovascular (CV) events (fatal and non-fatal stroke, fatal and non-fatal MI and fatal and non-fatal CHF requiring hospitalization), and end-stage renal failure (ESRF). Secondary outcomes were systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR).Compared with first-line calcium channel blockers (CCBs), we found moderate-certainty evidence that first-line RAS inhibitors decreased heart failure (HF) (35,143 participants in 5 RCTs, risk ratio (RR) 0.83, 95% confidence interval (CI) 0.77 to 0.90, absolute risk reduction (ARR) 1.2%), and that they increased stroke (34,673 participants in 4 RCTs, RR 1.19, 95% CI 1.08 to 1.32, absolute risk increase (ARI) 0.7%). Moderate-certainty evidence showed that first-line RAS inhibitors and first-line CCBs did not differ for all-cause death (35,226 participants in 5 RCTs, RR 1.03, 95% CI 0.98 to 1.09); total CV events (35,223 participants in 6 RCTs, RR 0.98, 95% CI 0.93 to 1.02); and total MI (35,043 participants in 5 RCTs, RR 1.01, 95% CI 0.93 to 1.09). Low-certainty evidence suggests they did not differ for ESRF (19,551 participants in 4 RCTs, RR 0.88, 95% CI 0.74 to 1.05).Compared with first-line thiazides, we found moderate-certainty evidence that first-line RAS inhibitors increased HF (24,309 participants in 1 RCT, RR 1.19, 95% CI 1.07 to 1.31, ARI 1.0%), and increased stroke (24,309 participants in 1 RCT, RR 1.14, 95% CI 1.02 to 1.28, ARI 0.6%). Moderate-certainty evidence showed that first-line RAS inhibitors and first-line thiazides did not differ for all-cause death (24,309 participants in 1 RCT, RR 1.00, 95% CI 0.94 to 1.07); total CV events (24,379 participants in 2 RCTs, RR 1.05, 95% CI 1.00 to 1.11); and total MI (24,379 participants in 2 RCTs, RR 0.93, 95% CI 0.86 to 1.01). Low-certainty evidence suggests they did not differ for ESRF (24,309 participants in 1 RCT, RR 1.10, 95% CI 0.88 to 1.37).Compared with first-line beta-blockers, low-certainty evidence suggests that first-line RAS inhibitors decreased total CV events (9239 participants in 2 RCTs, RR 0.88, 95% CI 0.80 to 0.98, ARR 1.7%), and decreased stroke (9193 participants in 1 RCT, RR 0.75, 95% CI 0.63 to 0.88, ARR 1.7% ). Low-certainty evidence suggests that first-line RAS inhibitors and first-line beta-blockers did not differ for all-cause death (9193 participants in 1 RCT, RR 0.89, 95% CI 0.78 to 1.01); HF (9193 participants in 1 RCT, RR 0.95, 95% CI 0.76 to 1.18); and total MI (9239 participants in 2 RCTs, RR 1.05, 95% CI 0.86 to 1.27).Blood pressure comparisons between first-line RAS inhibitors and other first-line classes showed either no differences or small differences that did not necessarily correlate with the differences in the morbidity outcomes.There is no information about non-fatal serious adverse events, as none of the trials reported this outcome.

AUTHORS' CONCLUSIONS

All-cause death is similar for first-line RAS inhibitors and first-line CCBs, thiazides and beta-blockers. There are, however, differences for some morbidity outcomes. First-line thiazides caused less HF and stroke than first-line RAS inhibitors. First-line CCBs increased HF but decreased stroke compared to first-line RAS inhibitors. The magnitude of the increase in HF exceeded the decrease in stroke. Low-quality evidence suggests that first-line RAS inhibitors reduced stroke and total CV events compared to first-line beta-blockers. The small differences in effect on blood pressure between the different classes of drugs did not correlate with the differences in the morbidity outcomes.

Blood pressure normalization via pharmacotherapy improves cutaneous microvascular function through NO-dependent and NO-independent mechanisms

Hypertension is associated with endothelial dysfunction and vascular remodeling.

OBJECTIVE

To assess effects of antihypertensive pharmacotherapy on eNOS- and iNOS-dependent mechanisms and maximal vasodilator capacity in the cutaneous microvasculature.

METHODS

Intradermal microdialysis fibers were placed in 15 normotensive (SBP 111±2 mm Hg), 12 unmedicated hypertensive (SBP 142±2 mm Hg), and 12 medicated hypertensive (SBP 120±2 mm Hg) subjects. Treatments were control, iNOS-inhibited (1400w), and NOS-inhibited (l-NAME). Red cell flux, measured during local heating (42°C) and ACh dose-response protocols, was normalized to CVC (flux MAP^-1 ) and a percentage of maximal vasodilation (%CVC_max ).

RESULTS

Compared to normotensives, ACh-mediated vasodilation was attenuated in the hypertensive (P<.001), but not in medicated subjects (P=.83). NOS inhibition attenuated ACh-mediated vasodilation in normotensives compared to hypertensive (P<.001) and medicated (P<.001) subjects. With iNOS inhibition, there was no difference in ACh-mediated vasodilation between groups. Compared to the normotensives, local heat-induced vasodilation was attenuated in the hypertensives (P<.001), but iNOS inhibition augmented vasodilation in the hypertensives so this attenuation was abolished (P=.31). Compared to normotensives, maximal vasodilator capacity was reduced in the hypertensive (P=.014) and medicated subjects (P=.004).

CONCLUSIONS

In the cutaneous microvasculature, antihypertensive pharmacotherapy improved endothelial function through NO-dependent and NO-independent mechanisms, but did not improve maximal vasodilator capacity.

First-line drugs inhibiting the renin angiotensin system versus other first-line antihypertensive drug classes for hypertension

BACKGROUND

Renin-angiotensin system (RAS) inhibitors are widely prescribed for treatment of hypertension, especially for diabetic patients on the basis of postulated advantages for the reduction of diabetic nephropathy and cardiovascular morbidity and mortality. Despite widespread use of angiotensin converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) for hypertension in both diabetic and non-diabetic patients, the efficacy and safety of RAS inhibitors compared to other antihypertensive drug classes remains unclear.

OBJECTIVES

To evaluate the benefits and harms of first-line RAS inhibitors compared to other first-line antihypertensive drugs in patients with hypertension.

SEARCH METHODS

We searched the Cochrane Hypertension Group's Specialised Register, MEDLINE, MEDLINE In-Process, EMBASE and ClinicalTrials.gov for randomized controlled trials up to November 19, 2014 and the Cochrane Central Register of Controlled Trials (CENTRAL) up to October 19, 2014. The WHO International Clinical Trials Registry Platform (ICTRP) is searched for inclusion in the Cochrane Hypertension Group's Specialised Register.

SELECTION CRITERIA

We included randomized, active-controlled, double-blinded studies with at least six months follow-up in people with primary elevated blood pressure (≥130/85 mmHg), which compared first-line RAS inhibitors with other first-line antihypertensive drug classes and reported morbidity and mortality or blood pressure outcomes. Patients with proven secondary hypertension were excluded.

DATA COLLECTION AND ANALYSIS

Two authors independently selected the included trials, evaluated the risk of bias and entered the data for analysis.

MAIN RESULTS

We included 42 studies, involving 65,733 participants, with a mean age of 66 years. Much of the evidence for our key outcomes is dominated by a small number of large studies at a low risk of bias for most sources of bias. Imbalances in the added second-line antihypertensive drugs in some of the studies were important enough for us to downgrade the quality of the evidence.Primary outcomes were all-cause death, fatal and non-fatal stroke, fatal and non-fatal myocardial infarction (MI), fatal and non-fatal congestive heart failure (CHF) requiring hospitalization, total cardiovascular (CV) events (consisted of fatal and non-fatal stroke, fatal and non-fatal MI and fatal and non-fatal CHF requiring hospitalizations), and ESRF. Secondary outcomes were systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR).Compared with first-line calcium channel blockers (CCBs), we found moderate quality evidence that first-line RAS inhibitors decreased heart failure (HF) (35,143 participants in 5 RCTs, RR 0.83, 95% CI 0.77 to 0.90, ARR 1.2%), and moderate quality evidence that they increased stroke (34,673 participants in 4 RCTs, RR 1.19, 95% CI 1.08 to 1.32, ARI 0.7%). They had similar effects on all-cause death (35,226 participants in 5 RCTs, RR 1.03, 95% CI 0.98 to 1.09; moderate quality evidence), total CV events (35,223 participants in 6 RCTs, RR 0.98, 95% CI 0.93 to 1.02; moderate quality evidence), total MI (35,043 participants in 5 RCTs, RR 1.01, 95% CI 0.93 to 1.09; moderate quality evidence). The results for ESRF do not exclude potentially important differences (19,551 participants in 4 RCTs, RR 0.88, 95% CI 0.74 to 1.05; low quality evidence).Compared with first-line thiazides, we found moderate quality evidence that first-line RAS inhibitors increased HF (24,309 participants in 1 RCT, RR 1.19, 95% CI 1.07 to 1.31, ARI 1.0%), and increased stroke (24,309 participants in 1 RCT, RR 1.14, 95% CI 1.02 to 1.28, ARI 0.6%). They had similar effects on all-cause death (24,309 participants in 1 RCT, RR 1.00, 95% CI 0.94 to 1.07; moderate quality evidence), total CV events (24,379 participants in 2 RCTs, RR 1.05, 95% CI 1.00 to 1.11; moderate quality evidence), and total MI (24,379 participants in 2 RCTs, RR 0.93, 95% CI 0.86 to 1.01; moderate quality evidence). Results for ESRF do not exclude potentially important differences (24,309 participants in 1 RCT, RR 1.10, 95% CI 0.88 to 1.37; low quality evidence).Compared with first-line beta-blockers, we found low quality evidence that first-line RAS inhibitors decreased total CV events (9239 participants in 2 RCTs, RR 0.88, 95% CI 0.80 to 0.98, ARR 1.7%), and low quality evidence that they decreased stroke (9193 participants in 1 RCT, RR 0.75, 95% CI 0.63 to 0.88, ARR 1.7% ). Our analyses do not exclude potentially important differences between first-line RAS inhibitors and beta-blockers on all-cause death (9193 participants in 1 RCT, RR 0.89, 95% CI 0.78 to 1.01; low quality evidence), HF (9193 participants in 1 RCT, RR 0.95, 95% CI 0.76 to 1.18; low quality evidence), and total MI (9239 participants in 2 RCTs, RR 1.05, 95% CI 0.86 to 1.27; low quality evidence).Blood pressure comparisons between RAS inhibitors and other classes showed either no differences or small differences that did not necessarily correlate with the differences in the morbidity outcomes.In the protocol, we identified non-fatal serious adverse events (SAE) as a primary outcome. However, when we extracted the data from included studies, none of them reported total SAE in a manner that could be used in the review. Therefore, there is no information about SAE in the review.

AUTHORS' CONCLUSIONS

We found predominantly moderate quality evidence that all-cause mortality is similar when first-line RAS inhibitors are compared to other first-line antihypertensive agents. First-line thiazides caused less HF and stroke than first-line RAS inhibitors. The quality of the evidence comparing first-line beta-blockers and first-line RAS inhibitors was low and the lower risk of total CV events and stroke seen with RAS inhibitors may change with the publication of additional trials. Compared with first-line CCBs, first-line RAS inhibitors reduced HF but increased stroke. The magnitude of the reduction in HF exceeded the increase in stroke. The small differences in effect on blood pressure between the different classes of drugs did not correlate with the differences in the primary outcomes.

Losartan modulates muscular capillary density and reverses thiazide diuretic-exacerbated insulin resistance in fructose-fed rats

The renin-angiotensin system (RAS) is involved in the pathogenesis of insulin sensitivity (IS). The role of RAS in insulin resistance and muscular circulation has yet to be elucidated. Therefore, this study sought to determine the mechanisms of angiotensin II receptor blockers (ARBs) and/or diuretics on IS and capillary density (CD) in fructose-fed rats (FFRs). Sprague-Dawley rats were fed either normal chow (control group) or fructose-rich chow for 8 weeks. For the last 4 weeks, FFRs were allocated to four groups: an FFR group and groups treated with the thiazide diuretic hydrochlorothiazide (HCTZ), with the ARB losartan, or both. IS was evaluated by the euglycemic hyperinsulinemic glucose clamp technique at week 8. In addition, CD in the extensor digitorum longus muscle was evaluated. Blood pressure was significantly higher in the FFRs than in the controls. HCTZ, losartan and their combination significantly lowered blood pressure. IS was significantly lower in the FFR group than in the controls and was even lower in the HCTZ group. Losartan alone or combined with HCTZ significantly increased IS. In all cases, IS was associated with muscular CD, but not with plasma adiponectin or lipids. These results indicate that losartan reverses HCTZ-exacerbated insulin resistance, which can be mediated through the modulation of muscular circulation in rats with impaired glucose metabolism.

Effects of blood pressure control with perindopril/indapamide on the microcirculation in hypertensive patients

BACKGROUND

Microvascular rarefaction and endothelium dysfunction are hallmarks of hypertension. We assessed whether antihypertensive treatments affect the microcirculation and whether the fixed-dose combination perindopril/indapamide (per/ind) modifies the microcirculation of hypertensive patients independently of blood pressure reduction.

METHODS

One hundred ninety-three consecutive patients were enrolled into one of four groups depending on their blood pressure and existing treatment: (i) controlled hypertensive patients treated with per/ind (controlled-per/ind), (ii) controlled hypertensive patients treated with agents other than angiotensin-converting enzyme (ACE) inhibitors or diuretics (controlled-other), (iii) uncontrolled hypertensive patients treated with agents other than ACE inhibitors or diuretics (uncontrolled-other), (iv) untreated normotensive subjects. Macro- and microcirculation parameters were evaluated once in every patient. We used intravital video microscopy to measure dermal capillary density in the dorsum of the fingers. Microvascular endothelial function was assessed by measuring the perfusion increases after pilocarpine iontophoresis and central hemodynamic parameters by tonometry.

RESULTS

Capillary density was significantly higher in controlled-per/ind patients (99 ± 12 capillaries/mm(2)) than in all other groups (P < 0.05). Controlled-per/ind patients had a significantly greater endothelial response to pilocarpine than patients from all other groups (P < 0.05). Central hemodynamic parameters were similarly improved in both controlled groups compared with the uncontrolled-other group (P < 0.05).

CONCLUSIONS

Thus, hypertensive patients with blood pressure controlled with the combination per/ind had normalized capillary density and endothelial function, whereas other antihypertensive treatments, excluding ACE inhibitors or diuretics, had less effect despite similar blood pressure control.

Myocardial perfusion in hypertensive patients with normal coronary angiograms

BACKGROUND

Pressure-induced left ventricular hypertrophy is one of the mechanisms responsible for an impaired coronary vasodilating capacity leading to myocardial ischemia and angina. The aim of the study was to investigate myocardial perfusion using cardiovascular magnetic resonance in patients with arterial hypertension and a history of chest pain and normal coronary angiography, and to estimate the influence of left ventricular hypertrophy on the parameters of myocardial perfusion.

METHODS

The study included 102 patients (mean age 55.4 +/- 7.7 years) with well controlled hypertension and 12 healthy volunteers. In 96 patients, myocardial first-pass perfusion cardiovascular magnetic resonance both at rest and during an infusion of adenosine 140 microg/kg/min was performed. Semiquantitative perfusion analysis was performed by using the upslope of myocardial signal enhancement to derive the myocardial perfusion index and the myocardial perfusion reserve index. The study group was divided according to the presence of left ventricular hypertrophy in the cardiovascular magnetic resonance examination: group with left ventricular hypertrophy (n = 40) and without left ventricular hypertrophy (n = 56).

RESULTS

Independent of the presence of left ventricular hypertrophy, there were significant differences in baseline myocardial perfusion index between hypertensive patients and controls (0.13 +/- 0.07 vs. 0.04 +/- 0.01; P < 0.001), and in stress myocardial perfusion index (hypertensive patients 0.21 +/- 0.10 vs. controls 0.09 +/- 0.03; P < 0.001). In hypertensive patients, the myocardial perfusion reserve index was reduced in the mid and apical portions of the left ventricle (1.71 +/- 1.1 vs. 2.52 +/- 0.83; P < 0.02). There was no significant correlation of myocardial perfusion reserve index with left ventricular mass or hypertrophy.

CONCLUSION

In patients with mild or moderate hypertension and a history of chest pain with normal coronary angiography, there is regional myocardial perfusion reserve impairment that is independent of the presence of left ventricular hypertrophy and may be a reason for angina.

Small artery stucture adapts to vasodilatation rather than to blood pressure during antihypertensive treatment

OBJECTIVE

Correction of the abnormal structure of resistance arteries in essential hypertension may be an important treatment goal in addition to blood pressure (BP) reduction. We investigated how this may be achieved in a prospective clinical study.

METHODS

Plethysmography was used to measure forearm resting vascular resistance (Rrest) and minimum vascular resistance (Rmin) as a measure of vascular structure. Two different groups of patients with essential hypertension were examined at baseline and after 6 months of antihypertensive treatment. In group A, 21 patients with never-treated essential hypertension were treated by their general practitioners using a variety of drugs to allow an assessment of the drug-independent effects. In group B, 28 beta-blocker-treated patients were shifted to angiotensin II receptor blocker treatment (eprosartan) to allow vasodilatation with no change in BP.

RESULTS

In group A, mean ambulatory blood pressure (ABP) fell from 119 +/- 2 (SE) to 103 +/- 2 mmHg (P < 0.01), whereas mean ABP was unchanged in group B (100 +/- 1 to 99 +/- 1 mmHg, P = NS). Both groups showed similar reductions in Rrest (-33.4 and -28.5%, respectively) and in Rmin (-15.4 and -15.6%, respectively). There was a strong correlation between changes in Rrest and Rmin within both groups (r = 0.57, P < 0.01 and r = 0.68, P < 0.0001, respectively), whereas the change in BP in group A was not correlated to the change in Rmin (r = -0.03).

CONCLUSION

The correction of forearm resistance artery structure during antihypertensive treatment depends on the vasodilatation achieved rather than BP reduction.

Forearm plethysmography in the assessment of vascular tone and resistance vasculature design: new methodological insights

AIM

High peripheral resistance and structural alteration in resistance arteries are central phenomena in essential hypertension and have been widely examined by forearm venous occlusion plethysmography; at rest for studying vascular tone, and during reactive hyperaemia for studying vascular structure. This work concerns the influence of venous pressure on hyperaemic vascular resistance (Rmin), the reproducibility of hyperaemic and resting vascular resistances (Rrest) and the relation between forearm and total peripheral vascular resistance (TPR).

METHODS

In four healthy subjects, intravenous and intra-arterial blood pressures were measured simultaneously with plethysmographic recordings of hyperaemic and resting forearm blood flows. Reproducibility was examined in 15 young and 14 middle-aged healthy subjects and in 21 untreated hypertensive patients.

RESULTS

Rmin remained low in the first recorded cardiac cycle, but rose in the second, even though corrected for the venous pressure rise, suggesting vascular tone recovery along with venous congestion. Between-day reproducibility of Rmin was high in middle-aged normotensive (8.7%) and hypertensive subjects (10.6%), but Rmin fell significantly between successive days in the young subjects. Rrest correlated with TPR, but required up to 40 min to reach steady state and showed high day-to-day variation in young (21.8%) and hypertensive subjects (16.2%).

CONCLUSIONS

During hyperaemia, vascular resistance should be measured in the first cardiac cycle following venous occlusion to minimize influences of venous pressure rise and possible tone recovery. Rrest seems to reflect TPR. About 20 subjects may be needed to detect 15% changes between days in Rrest, fewer when concerning Rmin and TPR.

Rationale for fixed-dose combinations in the treatment of hypertension: the cycle repeats

Single-drug therapy remains the preferred way to begin treatment of hypertension, although in many patients this is unable to bring blood pressure (BP) to goal levels. Single-drug therapy, even when maximally titrated, is at best only modestly effective in normalising BP in Stage-I or II hypertension, which represents the majority of the hypertensive population. It is increasingly appreciated that the elusive goal of a 'normal' BP is achieved only if multi-drug therapy is employed. This is especially so when considered in the context of today's lower BP goals. The options for multi-drug therapy are quite simple: either fixed-dose combination therapy or drugs added sequentially one after another to then arrive at an effective multi-drug regimen. Advocates exist for both approaches. A considerable legacy, dating to the 1950's, exists for fixed-dose combination therapies. The rationale to this approach has remained constant. Fixed-dose combination therapy successfully reduces BP because two drugs, each typically working at a separate site, block different effector pathways. In addition, the second drug of such two-drug combinations may check counter-regulatory system activity triggered by the other. For example, a diuretic and beta-blocker combination may find the diuretic correcting the salt-and-water retention which occasionally accompanies beta-blocker therapy. The pattern of adverse effects also differs with fixed-dose combination therapy, in part, because less drug is generally being given. In addition, one component of a fixed-dose combination therapy can effectively counterbalance the tendency of the other to produce adverse effects. For example, the peripheral oedema, that accompanies calcium channel antagonist therapy, occurs less frequently when an ACE inhibitor is co-administered. ACE inhibitors improve, if not eliminate, the peripheral oedema associated with calcium channel antagonists because of their proven ability to cause venodilation. In addition, diuretic therapy-induced volume contraction may generate a state of secondary hyperaldosteronism and thereby electrolyte abnormalities such as hypokalaemia and/or hypomagnesaemia. In many cases, the co-administration of either an ACE inhibitor or an angiotensin II receptor blocker with a diuretic corrects the aforementioned electrolyte disturbances. Fixed-dose combination therapy has a proven record of reducing BP. This form of treatment has been available for close to a half-century. Over that period of time, many physicians have taken advantage of this therapeutic approach even when academic opinion was less than charitable to this concept. Academic opinion is rarely immutable and occasionally irrelevant to prescription practice. Prescription practice is driven by many considerations including ease of use, cost and tolerance of a therapy. Most importantly, the therapeutic pathway taken should successfully result in goal BP being reached in a large number of those treated. Unfortunately, despite the simplicity of the concept behind fixed-dose combination therapy, its success will ultimately rest on cost. If made truly cost-competitive, it will gain an increasing share of the hypertensive market. If not, market forces will relegate it to a secondary role for hypertension treatment.

ACE gene polymorphism as a prognostic indicator in patients with type 2 diabetes and established renal disease

OBJECTIVE

To investigate whether the DD genotype is a predictor of mortality and of the decline in renal function in patients with type 2 diabetes and established nephropathy.

RESEARCH DESIGN AND METHODS

A total of 56 such patients of Maltese Caucasian descent were recruited, and their ACE genotype was determined. Serum creatinine was estimated approximately every 4 months. The glomerular filtration rate (GFR) was calculated according to the Cockroft-Gault formula, and rate of change was determined by regression analysis.

RESULTS

The rate of change in calculated GFR was -7.76 ml.min(-1).year(-1) in those with the DD genotype (n = 31) and -1.17 ml. min(-1). h(-1) in those with the ID or II genotype (n = 25) (P < 0.01). The 3-year mortality was 45.2% in the DD group compared with 20.0% in the ID/II group (P < 0.05).

CONCLUSIONS

The DD genotype of the ACE gene polymorphism is associated with a more rapid decline in renal function and higher mortality in type 2 diabetic patients with established nephropathy.

Vasodilatation, not hypotension, improves resistance vessel design during treatment of essential hypertension: a literature survey

Correction of structural abnormalities in resistance arteries of patients with essential hypertension is a potential treatment goal, in addition to blood pressure reduction. However, available evidence from human as well as from animal studies indicates that antihypertensive therapy is not always accompanied by normalization of resistance vessel structure, despite normalization of blood pressure. Thus, blood pressure is not the only factor determining resistance vessel structure, and experimental studies show that several factors could play a role, including shear stress and hormonal stimulation. To date, there has been no systematic review of the many published papers which have studied the structural effects of antihypertensive therapy, and it is not known which conditions are best able to normalize resistance vessel structure. We have therefore made a survey of the available literature. The survey shows that change in blood pressure in indeed a poor indicator of change in resistance vessel structure. However, it is a remarkably consistent finding that normalization of resistance vessel structure is obtained with therapeutic regimens which reduce blood pressure by vasodilation rather than by lowering cardiac output Thus, to the extent that normalization of resistance vessel structure is deemed a goal of antihypertensive treatment, the survey points towards the importance of considering not only the treatment effect on blood pressure, but also the haemodynamic effects within patients with essential hypertension.

Relationship between salt and blood pressure in hypertensive patients on chronic ACE-inhibition

We investigated the effect of a 4-day oral salt load (150 mmol NaCl extra per day) on blood pressure, erythrocyte sodium transport and the activity in the renin-angiotensin system in six males with primary hypertension, who had attained normotension on chronic enalapril treatment for 4 years. The design was a placebo-controlled, randomized, two-way cross over, double-blind study, i.e. each patient served as his own control. Intracellular erythrocyte sodium and potassium content were measured by flame photomometry. The increase in the intracellular sodium concentration during 1 h in 37 degrees C incubation of whole-blood with ouabain (compared with no-ouabain) was measured to determine the rate of active sodium efflux. 24-h blood pressure registration was performed with Space-lab equipment (SL 90202) before and at the end of the salt load. Left ventricular morphology was evaluated with echocardiography and the minimal vascular resistance of the hand vascular bed with water plethysmography at baseline and after 4 years on enalapril. Four years' enalapril treatment caused a significant decrease in blood pressure, left ventricular mass and minimal vascular resistance. During the 4-day salt load average 24-h blood pressure was significantly elevated, 129+/-3/85+/-2 mmHg as compared to 124+/-2/82+/-2 mmHg during placebo treatment (p=0.025). The change (delta) in MAP during high salt intake showed a negative relationship to delta-sodium efflux rate constant (r=-0.65, p=0.047). No significant relationship was found between the blood pressure response to the salt load and structural cardiovascular changes. In conclusion, a short-term oral salt load in hypertensive patients on chronic enalapril treatment caused a blood pressure rise, which was related to cellular sodium transport but not to structural cardiovascular changes.

The Captopril Prevention Project (CAPPP) in hypertension--baseline data and current status

The Captopril Prevention Project (CAPPP) is an ongoing intervention study conducted in 11,019 hypertensive patients in Sweden and Finland. Patients have been randomized to receive either conventional antihypertensive therapy (diuretics and/or beta-blockers) or captopril-based treatment. A prospective, randomized, open, blinded-endpoint evaluation (PROBE) study design is used to compare these two therapeutic regimens as regards cardiovascular morbidity and mortality. The rationale for the CAPPP Study are the many observations of beneficial effects of ACE inhibition, as compared to diuretics and beta-blockers, on intermediary endpoints such as insulin sensitivity, serum lipoproteins, left ventricular hypertrophy and renal function. Captopril has also been shown to be markedly effective in the treatment of left ventricular dysfunction as well as congestive heart failure. The hypothesis is that these differences might result in improved risk reduction when ACE inhibitors are used in the treatment of hypertension. The present paper describes the baseline data and the changes in blood pressure during the first year in the total cohort. During the first year the average blood pressure was reduced by 11/8 mm Hg. A number of substudies have been conducted in the CAPPP Study. In one of these insulin sensitivity was compared in a subgroup of the patients using the euglycemic insulin clamp technique. In another substudy the ACE gene was sequenced and some new polymorphisms were discovered. Several other substudies are in progress or in the planning phase. The main results of the CAPPP Study should be available by mid-1998. Some of the intended anayses of the final results as well as other planned substudies are briefly described here.

The renin-angiotensin system and vascular hypertrophy

In addition to its vasoconstrictor and aldosterone-stimulating action, angiotensin II also drives cell growth and replication in the cardiovascular system, which may result in myocardial hypertrophy and hypertrophy or hyperplasia of conduit and resistance vessels in certain subjects. These actions are mediated through angiotensin II receptors (subtype AT1), which activate the G protein, phospholipase C, diacylglycerol and inositol trisphosphate pathway, to increase the expression of certain protooncogenes (c-fos, c-myc and c-jun) and growth factors (platelet-derived growth factor-A-chain, transforming growth factor-beta 1 and basic fibroblast growth factor). The cellular responses to angiotensin II in vascular smooth muscle have been shown in different hypertensive vessels to be either hypertrophy alone, hypertrophy and DNA synthesis without cell division (polyploidy) or DNA synthesis with cell division (hyperplasia). In genetic hypertension, the altered structure of small arteries is due to either cellular hyperplasia or remodeling, whereas in renovascular hypertension there is hypertrophy of vascular smooth muscle cells. Angiotensin II also increases synthesis of some matrix components, activates blood monocytes and is thrombogenic. Angiotensin-converting enzyme (ACE) inhibitors prevent or reverse vascular hypertrophy in animal models of hypertension; this seems to be a class effect, shared to some extent with calcium channel blocking agents. In human hypertension, ACE inhibitors reduce the increased media/lumen ratio of large and small arteries in hypertension and increase arterial compliance. These properties are also shared by losartan, the first of the new class of angiotensin II receptor (AT1) antagonists. The clinical implications of these findings need to be tested through rigorous and prospective clinical trials.

Withdrawal of antihypertensive therapy in the elderly. The issues

Studies of antihypertensive drug withdrawal suggest that at least 20% of selected older patients with hypertension can remain normotensive without drug treatment for periods of up to 5 years. Success of drug withdrawal is greater in those patients controlled on low dose monotherapy who have low on-treatment blood pressure (BP), are not overweight and who have no ECG evidence of left ventricular hypertrophy. Compliance with lifestyle advice may increase the chance of successful drug withdrawal. Unfortunately, many older hypertensive patients have poorly controlled BP despite treatment with antihypertensive drugs, and are overweight. These factors limit opportunities for drug withdrawal although they may not be so much of a problem in the very elderly. Patient who could be considered for a trial of antihypertensive drug withdrawal are those unhappy with such therapy who also: (a) have well controlled BP on monotherapy with no significant target organ damage, (b) have 'white-coat' hypertension, or (c) are very elderly (> 80 years). The withdrawal of antihypertensive drugs can improve drug-induced metabolic abnormalities and symptoms, and appears safe providing there is a gradual reduction in drug dosages and close follow-up to detect a return to hypertension.