Measurement of cardiac synchrony using Approximate Entropy applied to nuclear medicine scans

As cancer therapy becomes more effective, allowing patients to live longer, the long-term morbidity of treatment assumes greater significance. Trastuzumab (Herceptin®), a monoclonal antibody that targets the epidermal growth factor, has proven efficacy in breast cancer patients but is also known to be cardiotoxic. Left ventricular ejection fraction (LVEF), a measure of cardiac function, is commonly used to evaluate patients receiving trastuzumab by Multiple Gated Acquisition (MUGA) isotope scans. In this paper, we have assessed the utility of previously published ventricular synchrony parameters in patients undergoing trastuzumab therapy. In addition, we apply Approximate Entropy (ApEn) to MUGA images, as a new measure of cardiac dysfunction and have evaluated its utility in the same patients. A significant change in LVEF (p = 0.015) and ApEn (p = 0.020) but not ventricular synchrony measures were observed over the course of treatment in these patients. The results suggest that ApEn provides a useful measure of cardiac function and synchrony.