Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiac disease in the general population. Myocardial fibrosis has become a prominent and clinically relevant pathophysiologic component of this complex genetic disease, related to the risk for both sudden death and heart failure. For example, left ventricular replacement fibrosis and scarring has been implicated in triggering life threatening ventricular tachycardia/fibrillation and most recently has become a novel risk marker for sudden death, based on in vivo demonstration of extensive late gadolinium enhancement (LGE) with cardiovascular magnetic resonance (CMR). Extensive LGE identifies patients who benefit from primary prevention of sudden death with the implantable cardioverter-defibrillators (ICD), or who evolve to the end-stage of this disease with systolic dysfunction and consideration for heart transplant.
The mineralocorticoid aldosterone has been shown to be a mediator of myocardial fibrosis, and blockade with spironolactone normalizes collagen content in HCM murine models. In addition, aldosterone antagonists have favorable clinical effects in patients with a variety of diseases associated with myocardial scarring such as congestive heart failure, systemic hypertension, and atherosclerotic coronary artery disease. However, it is uncertain whether spironolactone would have similar effects on the clinical and phenotypic expression of a genetic disease such as HCM. Therefore, we investigated whether mineralocorticoid receptor blockade with spironolactone would reduce measures reflecting myocardial fibrosis, producing favorable LV remodeling and ultimately leading to positive clinical effects for patients with HCM.
The general aim of this study is to explore the role of fibrosis in HCM by testing the hypothesis that: the presence of magnitude of myocardial fibrosis bears clinical relevance for patients with HCM, and that mineralocorticoid receptor blockade will reduce myocardial fibrosis and thereby alter the natural history of the disease.
Experimental design: prospective, randomized, double-blind, placebo-controlled trial in a consecutive HCM population at a single clinical center (Tufts Medical Center HCM Institution).
Study procedures: HCM patients were recruited from Tufts Medical Center HCM Institution population from November 2007 to June 2009. Enrolled patients were randomized into two arms; treatment arm received 25mg at the start of study and then increased to target dose of 50mg if serum potassium was \<5.5mmol/L and serum creatinine-baseline creatinine was \<0.5mg/dl. This arm was then followed for 12 months. The control arm of the study received 25mg of placebo over 12 months. There was an additional control arm of age and gender-matched controls without HCM in the control arm to evaluate the serum markers of collagen turnover at baseline. These controls had a one time blood draw of 15mL (3 teaspoons) to assess serum biomarkers of interest and were not be followed for 12 months.
Specific outcome measures:
Primary Outcome: examine the effects of a 12-month treatment with the aldosterone antagonist spironolactone on magnitude of fibrosis as measured by serum markers of collagen turnover as well as changes in clinical and morphologic disease parameters.
Secondary Outcomes: explore the effects of a 12-month treatment with aldosterone antagonist spironolactone on heart failure status, diastolic function, arrhythmic burden, and total LV mass and quantity of fibrosis by CMR.
Secondary Outcome: assess serum markers of collagen turnover at baseline and correlate these findings with a variety of clinical and morphologic disease parameters
