Effects Of Left Bundle Disease On Cardiac Function In Dilated Cardiomyopathy Based On Cardiac Magnetic Resonance

BackgroundsDilated cardiomyopathy(DCM)is characterized by ventricular or biventricular dilatation and impaired myocardial contractility which is not explained by hypertension,congenital heart disease,valvular heart disease or significant coronary artery disease.DCM is the most common cause of heart failure and heart transplantation worldwide.However,the etiology of DCM is unknown.Individual genetic susceptibility,viral infection,and autoimmune dysfunction could be responsible for the onset and progression of DCM.The excessive activation of the nerve-humoral mechanism and the dysfunction of the immune system by various precipitating factors could aggravate myocardial remodeling of the genetically susceptible individuals and lead patients into a vicious circle.Decompensated heart failure and sudden cardiac death could occur at any stage in the course of DCM patients.However,there are no specific treatments for DCM patients currently.Therefore,the strategy that stratify the risk of DCM patients and determine the related factors that could increase the mortality and identify the DCM patients who need more close monitoring or treatment thereby could have a beneficial effect on treatment and prognosis of DCM patients.Electrocardiogram is widely used in the first medical contact to assessment for the patients with heart failure.It is essential to evaluate the impact of arrhythmia on cardiac function in patients with DCM and establish a reasonable treatment plan immediately.Wth the progression of DCM,inactivated fibrous tissue gradually replaced the functional myocardial cells,multiple conduction blocks can occur when the cardiac conduction system involved.According to the different parts of the left bundle branch that impaired in the progress of DCM,the left bundle disease(LBD)includes the complete left bundle branch block(CLBBB),left anterior fascicular block(LAFB),and the left posterior fascicular block(LPFB).CLBBB has an important clinical significance which found in about 1/4 of all patients with congestive heart failure and associated with increased mortality.The mechanism of the negative effect of CLBBB on cardiac function is in-coordinated ventricular contractions which result in left ventricular contractile inefficiency and decompensation,CLBBB is thereby also a sign of poor prognosis in patients with DCM.With the development of cardiac resynchronization therapy(CRT),the quality of life and long-term prognosis of DCM patients with CLBBB have improved significantly.However,there are a third of patients still have poor response of CRT.On the other hand,the impaired of the left anterior fascicle can be found as LAFB in electrocardiogram.Because of the anatomical characteristics of the left anterior fascicle that crosses the left ventricular outflow tract and dominated by isolated vessel,LAFB often coexists in patients with DCM.LAFB has usually been considered a benign electrocardiographic finding with mild cardiac risk and prognosis value,however,the recent research find LAFB could be a useful clinical marker for various cardiovascular diseases,and LAFB is associated with an increased risk of atrial fibrillation,heart failure,and even cardiac death.Transthoracic echocardiography(TTE)is commonly used in clinical for the analysis of the cardiac function in the patient with DCM.In general,TTE can quickly obtain the structure and function of the heart,which is both cost-effective and easily accessible.However,the low spatial resolution and large operator deviation of TTE decrease the credibility of the results.With the rapid development of non-invasive diagnostic technology in China,3.0T cardiac magnetic resonance(CMR)has an excellent soft tissue contrast,plenty of imaging sequences and better repeatability,which provides the most comprehensive cardiac evaluation including chamber size quantification,ventricular function and mass myocardial wall thicknesses,segmental function,and tissue characterization in a single examination,the cardiac magnetic resonance imaging is thereby considered as the one-stop shop to evaluate various cardiovascular disease.CMR is widely used and more accurate than TTE in assessing the cardiac morphology and function in patients with DCM.In addition,the delayed enhancement-MRI(DE-MRI)protocol of CMR can identify the myocardial fibrosis in a non-invasive way.DE-MRI currently become the "gold standard" for assessing myocardial fibrosis and scarring in DCM patients.The late gadolinium enhancement(LGE)detected by DE-MRI has an important value in the assessment of clinical condition and prognosis of DCM patients.ObjectiveTo explore the effect of left bundle disease on cardiac function in dilated cardiomyopathy and the clinical application value of 3.0T cardiac magnetic resonance in left bundle disease.MethodsA retrospective study was performed to analyze the clinical data of 139 patients admitted to the Department of Cardiology of the First Affiliated Hospital of Zhengzhou University and clinically confirmed as DCM from January 1,2018 to February 28,2019.The general clinical indicators of each patient were recorded at admission,such as height,weight,age and NYHA class of cardiac function.After fasting and water deprivation for 8 hours,blood sampling was drawn the next early morning for the electrolytes,complete blood count,liver and kidney function,N-terminal B-type natriuretic peptide(NT-proBNP)and other blood biochemical indicators.Each patient underwent 12-lead electrocardiogram,TTE and CMR.The following cardiac function parameters were measured:left ventricular end systolic volume index(LVESVI),left ventricular end diastolic volume index(LVEDVI),left ventricular end diastolic diameter index(LVEDDI),left ventricular myocardial mass index(LVMMI)and left ventricular ejection fraction(LVEF).Based on electrocardiogram results,the patients were divided into 93 cases with normal ventricular conduction group,17 cases in the left anterior branch block(LAFB)group and 29 cases in the complete left bundle branch block(CLBBB)group.The differences in clinical data,cardiac structure,cardiac function,blood biochemical indicators,and LGE between the three groups of patients were compared.Then combined patients in LAFB group and CLBBB group into the LBD group,and compared the clinical data,blood biochemical parameters,cardiac structure,cardiac function,and LGE between the two groups.Finally,logistic regression was used to analyze the potential adverse impact of each factor on LBD,Results? The comparison of general clinical results between CLBBB group,LAFB group and Normal group:There were 93(66.9%)patients in the normal ventricular conduction group,17(12.2%)in LAFB group,and 29(20.9%)in CLBBB group.Compared with the Normal group,the CLBBB group had a lower male proportion and elder age(P<0.05).There were no significant differences in hemoglobin,potassium,albumin,estimated glomerular filtration rate,NT-proBNP,hypertension,diabetes,and NYHA class of cardiac function between these 3 groups(P>0.05).?Cardiac function measured by TTE comparison between CLBBB group,LAFB group and Normal group:The differences between these 3 groups were no significant in LVESVI,LVEDVI,LVEDDI and LVEF measured by TTE.(P>0.05).?Cardiac function measured by CMR comparison between Normal group,LAFB group and CLBBB group:Compared with the Normal group,the LAFB group and CLBBB group had a lower LVEF values,and the LVESVI in the CLBBB group was greater than the normal group(P<0.05).Compared with the Normal group,the LAFB group and CLBBB group had higher rate of LGE.Furthermore,the rate of LGE were even higher in LAFB group when compared with the CLBBB group(P<0.05).There were no significant differences in LVEDVI and LVMMI measured by CMR between these 3 groups(P>0.05).?Results comparison between Normal group and LBD group:After combining LAFB group with CLBBB group,there were 46 patients(33.1%)in LBD group.The age of LBD patients,LVESVI and LGE measured by CMR were higher than those of normal ventricular conduction group;the LVEF measured by CMR was lower than those of normal ventricular conduction group(P<0.05).The gender,hemoglobin,potassium,albumin,estimated glomerular filtration rate,NT-proBNP,hypertension,diabetes,NYHA cardiac function,values measured by TTE,LVEDVI and LVMMVI measured by CMR between normal ventricular conduction group and LBD group were not statistically significant(P>0.05).?Logistic regression analysis:The increased of age,LVESVI,the incidence of LGE and decreased of LVEF value were risk factors for LBD when use the univariate logistic regression analysis(P<0.05).After adjusting for other confounding variables,the multivariate logistic regression analysis showed that the increased incidence of LGE(OR:4.869,95%CI:2.213-11.169,P<0.001)and the decrease in LVEF value(OR:0.937,95%CI:0.885-0.992,P<0.05)were associated with an increased risk of LBD in DCM patients.ConclusionsDCM patients combined with CLBBB or LAFB have worse cardiac function and the replacement fibrosis of myocardial is more common than patients with normal ventricular conduction.The increased incidence of LGE and the decreased of LVEF value are related to the increased risk of LBD in DCM patients,however,the left ventricular dilatation is not significant in the LBD patients.In addition,CMR can better detect the cardiac function changes in DCM patients than TTE.