Objectives 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. The mechanism is believed due to malignant ventricular and / or left ventricular outflow tract obstruction (LVOTO), and myocardial fibrosis and scar were thought to be the pathological substrate, which is reported 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 April 2010 to May 2012, we followed up all HCM patients come to our hospital every 3 to 6 month 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 hospitalisation 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 procedure to 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.
Results Totally 392 patients were followed up; including 80 patients received gradient reduction therapy during the follow-up. Among the 312 natural procession patients, LGE was observed in 218 patients (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. 35 patients reached the primary end points, including 5 in the LGE negative and 30 in the LGE positive group (5.3% vs. 13.8%, p < 0.05); while 3 cardiac deaths, 1 heart transplantation and 9 sustained ventricular tachycardia/ventricular fibrillation were all happened in the fibrosis group. 77 patients reached the secondary end points, including 10 in the LGE negative and 67 in 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 left ventricular outflow tract obstruction (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.
Conclusions 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
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