| BackgroundHypertension is a major risk factor that closely associated with the morbidity and mortality of cardiovascular disease. In the past, hypertension guidelines just focused on the blood pressure value without paying attention to the total cardiovascular risks. In recently, amounts of evidence from clinical trials have demonstrated that successful blood pressure reduction can lower the cardiovascular risks. Though these evidences have been accepted widely, the control rate of hypertension is still very low. Medicine treatment is an essential part for hypertension control and the aim of taking antihypertensive medicine is not only to change the blood pressure values, but to prevent and delay the stroke, myocardial infarction, sudden cardiac death and other severe complications. In the national hypertension manage guidelines, β-blockers along with Calcium Channel Blockers,Angiotensin Converting Enzyme Inhibiters,Angiotensin Receptor Blocker and diuretics, as the first-line antihypertensive agents, can be used both in the initial therapy or long-term continuing therapy.β-blockers have beenconsidereda cornerstone in therapy for hypertension for more than50years. Since the first one propranolol came on the scene, they were widely used in the treatment of various cardiovascular diseases. In the past4decades,β-blockers are recommended as the first-line antihypertensive drug in most recent international guidelines in uncomplicated hypertension.Nowadays, based on some large-scale, multicenter randomized controlled trials, many physicians perceived β -blockers as the most protective class of drugs for the heart and brain and considered them the most effective therapy in reducing CV mortality among all other drugs. In some published meta-analysis related with β-blockers also indicated that it is inferior to other antihypertensive agents in reducing the risk of stroke in elderly as well as increasing the risk of new onset diabetes. Whereas, in these above RCTs, a potential explanation for the reduced efficacy of β-blockade is that most older trials used atenolol at low doses, such as50mg, which are perhaps not effective in allowing24-hour BP control and the results were lack of the evidences of other β-blockers. In China, Chinese Society of Cardiology of Chinese Medical Association has issued an expert consensus about the use of β-blockers in cardiovascular diseases. It pointed that Chinese clinicians should combine with Chinese actual conditions and information from foreign experts and made exact decisions in their work. It should be more standardized of the application of β-blockers in cardiovascular field.ObjectiveThe aim of our study is to make a comparison between the β-blockers(including traditional agents like atenolol, metoprolol, propranolol and the newer β-blockers showing vasodilatory properties, such as carvedilol and nebivolol) with other antihypertensive agents(CCBs, ACEI, ARBs and diuretics) to explicit their influence on the all-caused mortality, incidence of stroke and cardiovascular events with lowering blood pressure. On the other hand, in order to confirm the efficacy and advantages of Atenolol compared with other newer β-blockers, we made another meta-analysis to verify why it was so important in these large-scale trialsso that we could reanalyze the state and value of β-blockers in the treatment of hypertension.Methods In study one, searchPubmed(1985-2013/Oct) and Embase (1980-2013/Oct), Google2013/Oct, the ScienceDirect, Cochrane library and input these keywords using OR to link (1)β-blockers, beta-adrenergic antagonists, atenolol, bisoprolol, propranolol, metoprolol, nebivolol(2)hypertension, antihypertensive treatment;(3) cardiovascular events, cardiovascular risk, total mortality, stroke.Put the (1)(2)(3) together using AND then finish the search process.In study two, we search the same database with another strategy:using OR to link these key terms(1)atenolol(2)carvedilol, bisoprolol, metoprolol, nebivolol(3) hypertension, antihypertensive treatment (4)blood pressure, wave reflection, left ventricular hypertrophy, total mortality, cardiovascular event. Make (1)(2)(3)(4) together using AND to finish the search process.At last, we’ve enlarged the retrieval in above databases and read related reviews and references to get more information. According to inclusion and exclusion criteria, we screened literatures respectively and then evaluated them using Jadad measuring scale. We extracted the useful data including the baseline characteristics, the use of medicines in intervention group and control group, follow-up years, primary end-point events and so on. Finally, we entered data into the Review Manager5.2system for study one to compare the different effects on total mortality, incidence of stroke and cardiovascular diseases when used β-blockers or other antihypertensive agents.And in study two, we used the same software and made a meta-analysis to illustrate which β-blocker is better in cardiovascular protection.ResultsIn study one, in the younger group (less than65years),we summarized5trials including17615subjects which8767from β-blocker treatment group and8848from the control group. The results showed that compared to the control group, β-blockers can reduce the risk of stroke(OR=0.81,95%CI: [0.67,0.98], P=0.03) but not be superior to other antihypertensive drugs in lowering the incidence of total mortality and cardiovascular diseases in the younger hypertensive patients.In the older group (more than65years),7trials were incorporated into our study. The total number of study participants was72386that34763patients received the β-blockers based antihypertensive therapy while the rest37623patients received other medicine therapy. In the results, β-blockers demonstrated similar influence on the incidence of total mortality. However, it is inferior to the other antihypertensive agents in reducing the risk of stroke (OR=1.26,95%CI:[1.16,1.37], P<0.0001) and the incidence of cardiovascular events (OR=1.10,95%CI:[1.01,1.19], P=0.02).In study two, in the comparison of antihypertensive efficacy between atenolol and other newer β-blockers, the latter showed a obvious advantage in reducing the central artery pressure than atenolol (MD=4.7;95%CI;[2.69,6.71]; P<0.00001). Moreover, the newer β-blockers were also much better than atenolol in lowering the augmentation index. However, there was no significant difference in lowering brachial blood pressure and heart rate between them.ConclusionFor younger patients, using β-blockers as the initial therapy for hypertension is a wise choice.β-lockers exhibit similar efficacy to other antihypertensive agents and can also reduce the risk of stroke significantly. Although in older group, β-blockers are not superior to other antihypertensive drugs in protecting cardiovascular and brain, considering the complicated clinical situations of elderly hypertensive patients with other complications like coronary heart diseases, chronic heart failure which are both strong indications of β-blockers. In addition, in our study we’ve proved that atenolol wasn’t superior to other newer β-blockers in lowering blood pressure and heart rate, even inferior to them in reducing the CAP and AIx.Whereas for lack of directly sufficient evidence from large-scale RCTs about the newer β-blockers, we cannot say that β-blockers have a cardiovascular protective effect in hypertensive patients. |
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