Abstract
Introduction: Anthracyclines are used effectively to treat many cancers. However, cumulative and irreversible cardiotoxicity can limit anthracyclines’ clinical benefit. Mechanisms of cardiotoxicity have been assessed in murine models, but no studies directly assess human heart contractility. Our objective was to assess left ventricular contractile force, kinetics of contraction and relaxation, and frequency-dependent activation in anthracycline-induced failing human myocardium. Methods: From 2009-2019, we assessed live tissue-level contractile forces and kinetics in isolated left ventricular intact trabeculae from failing and non-failing human hearts. After the trabeculae were transferred to and stabilized in a custom setup, baseline contractile force and kinetic parameters were assessed at 1 Hz (normal resting in vivo heart rate), followed by frequency-dependent activation (0.5-3.0 Hz) under near-physiological conditions. Retrospectively, we analyzed muscles from three cohorts of individuals: (1) with non-ischemic cardiomyopathy due to anthracycline toxicity (NICM-AC; n =14), (2) with NICM and history of cancer without anthracycline or known cardiotoxic treatments (NICM; n =14), and (3) with non-failing myocardium and no history of cancer (NF; n =14). Results: At stimulation of 1 Hz, active developed force (Fdev) of NICM-AC trabeculae was significantly lower than NF and NICM trabeculae. NICM-AC trabeculae exhibited prolonged 90% relaxation time (RT90), significantly slower maximal rate of force decay (-dF/dt), and slower maximal kinetic rate of relaxation (-dF/dt/Fdev). In addition, frequency-dependent activation and relaxation were markedly impaired in both failing groups. Conclusions: Human myocardium failing due to anthracycline toxicity had significantly decreased force and slower relaxation kinetics compared to non-ischemic failing myocardium. With increase in stimulation frequency, anthracycline treated myocardium exhibited impaired activation and relaxation kinetics. These findings suggest that cardio-protection strategies should aim to improve not only contractile force, but also kinetics of relaxation.
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