Molecular basis of regression of cardiac hypertrophy

Comparative efficacy of different types of antihypertensive drugs in reversing left ventricular hypertrophy as determined with echocardiography in hypertensive patients: A network meta-analysis of randomized controlled trials

Reversing left ventricular hypertrophy (LVH) can reduce the incidence of adverse cardiovascular events. However, there is no clear superiority-inferiority differentiation between angiotensin-converting enzyme inhibitors (ACEI), angiotensin receptor blockers (ARB), beta-blockers (BB), calcium channel blockers (CCB), and diuretics in reversing LVH in hypertensive patients. To provide further evidence for choosing the optimal antihypertensive drug for improving LVH, we performed a network meta-analysis of randomized controlled trials (RCTs) based on the Cochrane library database, Embase, and Pubmed, and identified 49 studies involving 5402 patients that were eligible for inclusion. It was found that ARB could improve LVH in hypertensive patients more effectively than CCB (MD -4.07, 95%CI -8.03 to -0.24) and BB (MD -4.57, 95%CI -8.07 to -1.12). Matched comparison of renin-angiotensin system inhibitors (RASi) showed that the effect of ACEI in reducing left ventricular mass index (LVMi) was not effective as that of ARB (MD -3.72, 95%CI -7.52 to -0.11). The surface under the cumulative ranking for each intervention indicated that the use of ARB was more effective among the different types of antihypertensive drugs (97%). This network meta-analysis revealed that the use of ARB in antihypertensive therapy could achieve better efficacy in reversing LVH in hypertensive patients.

The NF-κB subunit c-Rel stimulates cardiac hypertrophy and fibrosis

Cardiac remodeling and hypertrophy are the pathological consequences of cardiovascular disease and are correlated with its associated mortality. Activity of the transcription factor NF-κB is increased in the diseased heart; however, our present understanding of how the individual subunits contribute to cardiovascular disease is limited. We assign a new role for the c-Rel subunit as a stimulator of cardiac hypertrophy and fibrosis. We discovered that c-Rel-deficient mice have smaller hearts at birth, as well as during adulthood, and are protected from developing cardiac hypertrophy and fibrosis after chronic angiotensin infusion. Results of both gene expression and cross-linked chromatin immunoprecipitation assay analyses identified transcriptional activators of hypertrophy, myocyte enhancer family, Gata4, and Tbx proteins as Rel gene targets. We suggest that the p50 subunit could limit the prohypertrophic actions of c-Rel in the normal heart, because p50 overexpression in H9c2 cells repressed c-Rel levels and the absence of cardiac p50 was associated with increases in both c-Rel levels and cardiac hypertrophy. We report for the first time that c-Rel is highly expressed and confined to the nuclei of diseased adult human hearts but is restricted to the cytoplasm of normal cardiac tissues. We conclude that c-Rel-dependent signaling is critical for both cardiac remodeling and hypertrophy. Targeting its activities could offer a novel therapeutic strategy to limit the effects of cardiac disease.

Improving the managed care of hypertension with angiotensin II antagonists

Among the modifiable risk factors for cardiovascular disease, hypertension is the most powerful and treatable. For an asymptomatic patient to remain on a lifetime of antihypertensive treatment that might cause adverse effects is difficult for most patients. Managed care plans should treat hypertensive patients in ways that the patient can remain on therapy to prevent complications and thereby reduce the long-term costs associated with untreated hypertension. The recent disappointing outcomes achieved with antihypertensive drugs suggest there is room for improvement in the management of hypertension. Since the introduction of the first orally active angiotensin II receptor blocking drug, losartan, attention has been focused on the central role of angiotensin II in hypertension and cardiovascular disease. Studies of angiotensin II antagonists (AIIAs), which block the tissue receptor for angiotensin II, show that these agents effectively control hypertension when given once daily and cause no significant adverse effects or laboratory abnormalities. Losartan is unique among the AIIAs in that it offers 1-step titration dosing and has a uricosuric effect. Losartan, candesartan, and valsartan have been shown to improve the symptoms of congestive heart failure; losartan has been similar to an angiotensin-converting enzyme inhibitor in reducing systolic dysfunction congestive heart failure mortality. At 1 year, the refill rate for losartan in a managed care setting has been more than that for any other class of antihypertensive agents. Although there is not yet a clinical trial determining the long term mortality of AIIA treatment in hypertension compared with other antihypertensive agents, the use of AIIAs in conjunction with lifestyle modification and patient education can provide more efficient hypertension control and a provide a treatment with which patients can live.

The effect of non-antihypertensive doses of angiotensin converting enzyme inhibitor on myocardial necrosis and hypertrophy in young rats with renovascular hypertension

In renovascular hypertensive rats, low doses of angiotensin converting enzyme (ACE) inhibitors have been found to prevent myocardial hypertrophy independent of blood pressure level. This finding would suggest humoral rather than mechanical control of myocyte growth. The aim of this study was to examine the effect of nonantihypertensive doses of ACE inhibitor on myocardial hypertrophy and necrosis in hypertensive rats. Renovascular hypertension (RHT) was induced in four-week-old Wistar rats. Twenty-eight animals were treated for four weeks with three doses of ramipril (0.01, 0.1 or 1. 0 mg/kg/day, which are unable to lower blood pressure. Fourteen animals were not treated (RHT group). A sham operated, age/sex-matched group was used as control (n = 10). Myocardial histology was analysed in 3 microm thick sections of the ventricle stained with either haematoxylin-eosin, reticulin silver stain or Masson's trichrome. There was a significant correlation between systolic blood pressure and left ventricular to body weight ratio in both sets of animals: untreated plus controls and ramipril-treated rats. ACE inhibition prevented myocyte and perivascular necrosis and fibrosis in a dose-dependent manner. We conclude that myocardial hypertrophy in rats with renovascular hypertension is directly related to arterial pressure, and that this relationship is not affected by nonantihypertensive doses of ACE inhibitor. Myocardial necrosis/fibrosis and coronary artery damage induced by angiotensin II are prevented by ACE inhibitor in a dose-dependent manner, despite the presence of arterial hypertension.

Vascular remodeling: the role of angiotensin-converting enzyme inhibitors

Chronic sustained hypertension leads to structural changes of the small and large arteries. These alterations consist of smooth-muscle hypertrophy, increased deposition of collagen, and "dilution" or destruction of elastin fibers. In addition, there may be no growth at all, but a "rearrangement" of vascular wall material termed "remodeling." These changes serve to increase wall thickness and the media-to-lumen ratio and to decrease the external and internal diameter of the vessel--all of which contribute to increased systemic vascular resistance by the small arteries and increased impedance by the larger arteries. It has been suggested that these structural changes are an adaptive effort by the vessel to maintain a constancy of wall tension, but the end result is detrimental in that the effect is a further increase in systemic vascular resistance and blood-flow impedance, which lead to left ventricular hypertrophy and its consequences. The stimuli for these changes are stretch stimuli, mediated through stretch receptors on the arterial wall, and trophic stimuli mediated at the tissue level through the action of angiotensin II, aldosterone, and catecholamines. Angiotensin-converting enzyme inhibitors, especially those with effective tissue penetration, are ideal drugs to reverse these structural changes ("reverse remodeling"), decrease the systemic vascular resistance, and increase the vascular compliance. These agents exert their effects through suppression, at the tissue level, of angiotensin II, aldosterone, catecholamines, endothelins (ET1, ET3), and transforming growth factor-beta1 (TGF-beta1) and through an increase in local levels of kinins, prostaglandins, and nitric oxide, which have antigrowth effects. Although this is a class effect, it appears to be stronger with those angiotensin-converting enzyme inhibitors providing the greatest tissue penetration.

Prevention of left ventricular hypertrophy by ACE-inhibitor, ramipril in comparison with calcium-channel antagonist, felodipine

This perspective study was performed to demonstrate the prevention of left ventricular hypertrophy by ACE-inhibitor, ramipril, in hypertensives of recent onset. Thirty-four hypertensive patients, treated with ramipril (group I), and 32 controls who received another frequently employed drug (the calcium channel-antagonist, felodipine (group II), were evaluated. Neither of two groups received any anti-hypertensive drug and did not suffer from left ventricular hypertrophy. All selected patients underwent M-mode echocardiography for measuring the following parameters: diastolic diameter of left ventricle, (DDLV); systolic diameter of left ventricle (SDLV); inter-ventricular septum (IVS); thickness of the posterior wall (PW); and left ventricular mass index (LVMI). Two anti-hypertensive drugs reduce systemic hypertension the same way. But, in hypertensives receiving ramipril (group I), the echocardiographic parameters of the left ventricle increased non-significantly. On the other hand, in those treated with felodipine (II group), these parameters significantly changed. The mechanisms of non-increase in cardiac and non-cardiac proteins, due to the ACE-inhibitors, are illustrated.

Long-term effects of angiotensin-converting enzyme inhibitors and calcium antagonists on the right and left ventricles in essential hypertension

To compare the effects of chronic antihypertensive treatment on left and right ventricular structure and function, 24 patients with mild to moderate, never-treated hypertension were randomized to receive fosinopril (20 mg daily) or amlodipine (10 mg daily) for 12 months. At baseline and subsequently at the end of third, sixth, and twelfth months, each patient underwent an integrated echocardiographic study and noninvasive ambulatory blood pressure monitoring. Both drugs significantly reduced blood pressure, casual or monitored (p < 0.01), and left ventricular mass index (from 125 +/- 32 to 100 +/- 12 gm/m2 [p < 0.02] with amlodipine and from 106 +/- 18 to 89 +/- 10 gm/m2 [p < 0.02] with fosinopril). The decrease in left ventricular mass was essentially caused by a reduction of ventricular thickness. Free right ventricular wall thickness was also lowered in both groups, more consistently with amlodipine (from 8.0 +/- 2.1 to 6.4 +/- 0.8 mm; p < 0.01), without an increase in plasma natriuretic peptide and insulin concentrations or heart rate. With both treatments, the decrease in ventricular mass was not associated with impairment of systolic function, whereas a trend toward an improvement of Doppler echocardiographic indexes of biventricular diastolic function was observed. In conclusion, both amlodipine and fosinopril induced similar qualitative effects on anatomy and function of both ventricles. The clinical meaning of these observations must be defined further by means of adequately sized prospective trials.

Enhancement of left ventricular relaxation in the isolated heart by an angiotensin-converting enzyme inhibitor

BACKGROUND

ACE inhibitors exert both acute and chronic beneficial effects on cardiac function (eg, remodeling, diastolic dysfunction) in experimental studies and in patients. They inhibit the formation of angiotensin II as well as the degradation of endogenous bradykinin. We recently reported that bradykinin induces selective left ventricular (LV) relaxant effects in isolated hearts via the release of nitric oxide. The present study examined the direct effects of interaction between the ACE inhibitor captopril and endogenous bradykinin on cardiac contractile function.

METHODS AND RESULTS

Isolated ejecting guinea pig hearts were studied under conditions of constant loading and heart rate. LV pressure was monitored by a 2F micromanometer-tipped catheter. Captopril (1 mumol/L, n = 9) caused a progressive acceleration of LV relaxation without significantly affecting early systolic parameters (eg, LV dP/dtmax) or coronary flow. These effects were inhibited by the nitric oxide scavenger hemoglobin (1 mumol/L, n = 5) or by the B2-kinin receptor antagonist HOE140 (10 nmol/L, n = 5). In the presence of captopril, bradykinin (0.1 nmol/L, n = 6) markedly accelerated LV relaxation (significantly more than captopril alone), whereas bradykinin alone (0.1 nmol/L, n = 6) had no effect.

CONCLUSIONS

These data indicate that the ACE inhibitor captopril causes an acute and selective enhancement of LV relaxation independent of changes in coronary flow, probably via an endogenous bradykinin/nitric oxide pathway.