Clinical Application Of Magnetic Resonance Imaging In Hypertrophic Cardiomyopathy

Background Hypertrophic Cardiomyopathy (HCM) is the most common inherited genetic cardiovascular disease and the most frequent cause of sudden cardiac death (SCD) in young people. Ventricular arrhythmias,especially non-sustained ventricular tachycardia (NSVT) or sustained VT, are believed to be the main cause of SCD. The aim of this study was to evaluate the correlation between ventricular arrhythmias and late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) in a large Chinese HCM cohort.Methods310patients were enrolled and divided into two groups regarding ventricular arrhythmias, including frequent premature ventricular contractions (PVCs), couplets and NSVT. The LGE was defined as those with image intensities>2SD above the mean of image intensities in a remote myocardial region in the same section. Total volume of LGE was calculated by summing the planimetered areas of LGE in all short-axis slices and was expressed as a proportion of total LV myocardium (%/LV). LGE positive patients were divided into three groups:mild (1%-25%/LV), moderate (25%-50%/LV) and severe (>50%/LV). Left ventricle was divided into different segments according to American Heart Association17segment model. Prevalence of ventricular arrhythmias was calculated regarding LGE amount. Univariate and multivariate-Logistic regression was analyzed to figure out risk factors of NSVT. Receiver operating curve (ROC) was applied to assess the diagnostic capability of risk determinants on NSVT.Results Left ventricular hypertrophy and the myocardial fibrosis were mainly located in interventricular septum (IVS), and there is good correlation between the segments of hypertrophy and the spectrum of LGE. There were more extreme hypertrophy (>30mm) in the IVS than other segments. Patients with ventricular arrhythmias had more extreme hypertrophic segments than those without ventricular arrhythmias, also the average wall thickness in the anterior and inferior segments of ventricular arrhythmias groupwere larger than the negative group. LGE was present in217(70%) patients, occupying12.0±9.8%(range1.4%to57.8%) of LV myocardium. There were94cases (43%),83cases (38%) and40cases (18%) in the mild, moderate and severe LGE groups, respectively. Prevalence of PVCs didn’t show significant difference among groups, while prevalence of couplets showed statistical significance only between the moderate and severe LGE groups. Prevalence of NSVT arose as LGE amount increased with statistical significance among all groups. LGE positive patients had a7-fold higher risk of NSVT than those without, and the correlation coefficient between them was0.680. In multivariate analysis, LA diameter and LGE amount were independent determinants of NSVT, and their area under ROC curve were0.633and0.798, respectively. The cut-off value of LGE amount as11.5%had a sensitivity of67.4%and specificity of85.1%to predict NSVT.Conclusions Myocardial fibrosis was correlated with the spectrum of hypertrophic segments, and prevalence of ventricular arrhythmias is correlated with LGE amount.Both LGE amount and LA diameter are independent predictors of NSVT. Background Hypertrophic cardiomyopathy is the most common inherited genetic cardiovascular disease and the main cause of sudden cardiac death (SCD) in the young, it can also cause other hard end points such as heart failure death and stroke. Themechanism is believed due to malignant ventricular and/or left ventricular outflow tract obstruction (LVOTO), and myocardial fibrosis was thought to be the pathological substrate, as an independent determinant of adverse cardiac events. This study is aim to evaluate the prognostic role of myocardial fibrosis detected by cardiac magnetic resonance late gadolinium enhancement(LGE-CMR) in the mid-term follow up of HCM.Methods From April2010to May2012, we followed up all HCM patients come to our hospital every3to6month intervals, with exclusion of those who had prior gradient reduction therapy. Only new events occurred during the follow up were regards as end points, which primary end points included cardiovascular death, heart transplantation, SCD/aborted SCD, sustained ventricular tachycardia, ventricular fibrillation and appropriate implantable cardiac defibrillator (ICD) discharge; and secondary end point included progressive heart failure, unplanned cardiovascular hospitalization and non-sustained ventricular tachycardia (NSVT). The extent of LGE was divided into three groups:mild (1%-25%/LV), moderate (25%-50%/LV) and severe (>50%/LV). Kaplan-Meier curves and log-rank test were used to estimate the events free survival distributions and compare the difference among different LGE groups. A multivariable Cox proportional hazard model was constructed with a forward selection procedureto estimate the hazard ratio (HR) for the presence or absence of fibrosis and to estimate the effect on the outcomes of increased amounts of fibrosis. Hypertrophic obstructive cardiomyopathy (HOCM) patients were also compared with non-obstructive patients for the events free survival curves, and patients received gradient reduction therapy were compared with those HOCM who didn’t receive any surgical procedure.Results Totally392patients were followed up; including80patients received gradient reduction therapy during the follow-up. Among the312natural procession patients, LGE was observed in218patients (70%). There were statistical significance on NYHA cardiac class, left ventricular mass, average wall thickness, extreme hypertrophy (>30mm), prevalence of atrial fibrillation and NSVT between patients with and without LGE.35patients reached the primary end points, including5in the LGE negative and30in the LGE positive group (5.3%vs.13.8%, p<0.05); while3cardiac deaths,1heart transplantation and9sustained ventricular tachycardia/ventricular fibrillation were all happened in the fibrosis group.77patients reached the secondary end points, including10in the LGE negative and67in the LGE positive (10.6%vs.30.7, p<0.05). There was statistical significance among Kaplan-Meier survival curves among different LGE groups, no matter regarding to primary or secondary end points. The LVOTO and LGE positive were the independent determinants for the primary end points after Cox proportional hazard regression, while only LGE was the risk factor for the secondary end points. There were statistical significance among the events free survival among HOCM, non-obstructive and apical HCM patients, and patients received gradient reduction therapy had better prognosis than those HOCM patients who didn’t received intervention.Conclusion Myocardial fibrosis detected by CMR can play an important prognostic role in HCM. The prognosis of HOCM was worse than the non-obstructive HCM patients, while receive gradient reduction therapy would benefit the mid-term survival.