Layer-specific Distribution of Myocardial Deformation from Anthracycline-induced Cardiotoxicity in Patients with Breast Cancer-From Bedside to Bench

Background: Anthracycline anticancer drugs such as epirubicin and doxorubicin may induce myocardial dysfunction, leading to poor prognosis. Early detection of minor left ventricular (LV) myocardial dysfunction is important for the prevention of anthracylcine-induced cardiotoxicity. Using layer-specific speckle tracking echocardiography (STE), we investigated the progressive distribution of myocardial dysfunction in both breast cancer patients and an animal toxicity model.

Methods: Patients with preserved LV ejection fraction (LVEF) preparing for epirubicin chemotherapy (N = 125) were prospectively enrolled. Layer-specific STE, including LV longitudinal and circumferential strains on subepicardium and subendocardium, were evaluated at baseline and after the first cycle, third cycle and six months of epirubicin therapy. A decline of LVEF above 10% to <55% at six months was defined as cardiotoxicity. These same strain measures were obtained in doxorubicin-treated rats and the distribution of myocardial fibrosis evaluated.

Results: In patients developing cardiotoxicity, LV longitudinal strain on subendocardium (LVLSendo) was significantly reduced after three cycles of therapy despite no significant changes in conventional LV systolic, diastolic parameters as well as LV circumferential strains at that moment. Compared to conventional echocardiographic parameters, LVLSendo was significantly predictive of cardiotoxicity. Declines in LVLSendo were also observed in doxorubicin-treated rats at an early stage. These reductions also predicted significant fibrosis in the subendocardial layer.

Conclusion: LVLSendo is useful for the early detection of minor cardiac dysfunction during chemotherapy, thereby implicating endocardial involvement in the development of cardiotoxicity.