TTN and nonischemic cardiomyopathy: While the cause of peripartum cardiomyopathy remains poorly understood, increasing evidence suggests a vascular etiology that is regulated by hormonal factors including prolactin, relaxin, activin A, and soluble Fms-like tyrosine kinase 1.63 A genetic predisposition for peripartum cardiomyopathy has been recognized for some time, and genetic variants seen recently in nonischemic cardiomyopathy also have been identified in up to 15% of patients with peripartum cardiomyopathy, with the majority of these being mutations in TTN, the gene encoding titin.63,64