Effects Of β-blocker In Targed Dosage On The Heart Function In Dilated Cardiomyopathy Patients With The Lower Heart Rate With The Backup Of Pacemaker

Objective: Dilated cardiomyopathy(DCM) is characterized by enlarged left or right ventricle, or both and with impaired systolic function. Patients with DCM usually present with congestive heart failure (CHF). It is very common in our clinical practice. It is one of the main causes of heart failure. After diagnosed, 5-year survival rate of these patients is lower than 30%.Therefore , it is of important value to explore the new approach for improvement of prognosis.Since it was reported that usingβ-blocker to treat DCM got a good result by Waagstein and his colleagues in 1975, scientists started to realize the importance ofβ-blocker in treating heart failure , including DCM. In our clinical practice, we found thatβ-blockers played a very important role in treating DCM. Unfortunately, some patients can not tolerateβ-blockers because of lower heart rates or heart blockes,which inhibit the use ofβ-blockers in these kind of patients. So the results were not very good. Firstly, we randmized these patients into two groups randomly. Secondly, we implanted pacemakers for the patients in the intervention group, while we took conservative therapies for the patients in control group. Thirdly, We increased the doses ofβ-blockers of the patients with pacemakers , then we observed the changes of the cardiac function and ventricular remodeling after larger doseβ-blocker treatment in patients with DCM.Methods: Including criteria were base the diagnostic standards of the world health organization in 1995 about DCM, which were DCM patients with New York Heart Association (NYHA) III～IV class, left ventricular ejection fraction (LVEF) <40%, and left ventricular end-diastolic diameter (LVEDD) >55cm and cardiothoracic ratio (CTR) of stemite >0.5.Between 2006-1 and 2007-9,we enrolled 25 patients. All the patients aged 14 to 75 years old, including 14 male and 11 female. Exclusion criteria were: rheumatic heart disease, congenital cardiopathy, hypertensive heart disease, other specific cardiomyopathy, endemic cardiomyopathy, diabetes, the patients of severe liver-renal inadequacy. The patients were randomely devided into intervention group (13 patients) and control group (12 patients). All patients took smaller dosages of Beta-blocker tolerately before enrollment. They took digitalis, diuretic, ACE inhibitor, aldosterone receptor antagonist. The patients in intervention group were implanted with pacemakers (AAI or DDD). The patients of control group took conservative therapies, including Beta-blocker. All the patients should not withdraw from the trial unless sever reactions accured.Cardiac function parameters, including chest X-ray, echocardiography, 6-minute walk test were measured regularly before and 6 months after enrollment respectively.Cardiothoracic ratio was measured by Kodak DirectView CR 850 type x-ray machine. The patients were taken in standing position when they were taken a photograph of orthotropia chest x-ray. CTR was a ratio of the widest transverse diameter of the heart and the bony thorax trans D.The cardiac function parameters were measured by SEQUOIA S-512 type ultrasonic diagnostic apparatus (Seimens company, Germany) using a 2.5MHZ frequency linear arrey transducer. these parameters include Left Ventricular end-systolic diameter (LVESD), Left Ventricular end-diastolic diameter (LVEDD), Left Ventricular fraction (LVEF), Left Ventricular posterior wall thickness (LVPWT), and Intraventricular Septal thickness (IVST). Body surface area {BSA(m2)=[0.0061×high (cm)+0.0128×weight(kg)]-0.01529,} was calculated according to their body length and weight, and Left Ventricular mass index(LVMI) was calculated according to Devereux Formula: LVMI(g/m2)=｛1.04×[(LVEDD+LVPWT +IVST)3-LVEDD3]-13.6｝÷BSA, at the same time, Left Ventricular end-shrinkable volume index (LVESVI) and Left Ventricular end-diastolic volume index (LVEDVI) were caculated.The method of six minutes walking test(6MWT) refered to Guyatt's method in 1985. Walks were conducted by a pre-measured, 30-meter straight path in a quiet airy hallway. Walk tests were timed with a stopwatch, and heart rate, blood pressure and breathing frequency were measured before and after the test, and electrocardiogram and clinical symptoms were monitored during the test. The patients were explained the test? s purpose and method before the test. Walking tests were initiated only when the patients indicated that they were ready for the test. They could slow down or stop if necessary, but the clock continued to run, and they were to resume walking as soon as they were able. They were encouraged properly during walk. The test could be stopped immediately if they suffered angina cordis, severe anhelation, malignant arrhythmia, lipothymia and so on during the test. At the end of 6MWT, total distance in meters was calculated for each walk, and the kinesi symptoms-angina cordis, severe anhelation, somasthenia, dizziness and lipothymia.All the data were analized by SPSS11.0 software pack. Initially the homogeneity of variance among all the groups was analyzed. All the measurement data was expressed by mean±standard deviation and students t test was used to test statistial significance. Chi-square test was used for analysis of categorical data. Data that did not distribute normally was compared by Wilcoxon-Mann-Whitney two sample test. We took P<0.05 as statistic significant level.Results: 1 During the study period, intervention group and control group had no case who died or lost.2 The clinical characteristics in age, sex, C/T ratio, heart rate, dose of Beta-blocker , 6MWT, LVEDD, LVESD, LVEF, LVMI, LVEDVI, LVESVI and cardiac function between both groups(P>0.05) were well matched.3 There were significant changes in intervention group and control group of LVEDD, LVESD, LVEF, LVMI, LVEDVI, LVESVI, 6MWT and C/T ratio compare with these of baseline at the end of the study(month 6) (P<0.05).4 Compared with control group, LVEDD, LVESD, LVEF, LVMI, LVEDVI, LVESVI , 6MWT and C/T ratio were significally improved at month 3 and the end of the study(month 6) (P<0.05).Concolusions: With the assistance of pacemaker, the targed dodage ofβ-blocker could reverse ventricular remodeling, and impove heart function better compared with smaller dosage ofβ-blocker.