"Broken heart syndrome" in cetaceans: histological, histochemical and immunohitochemical study

Abstract

Both humans and other animals, like cetaceans, have evolved mechanisms to cope with stressful situations in their lives. However, it is possible to develop different diseases when the stress is excessive or prolonged over time. An example is the Stress Cardiomyopathy (SCMP), also known as “Takotsubo disease”, “Broken Heart Syndrome”, or “Apical Ballooning Syndrome”, which is a reversible cardiomyopathy (CMP) in humans, most often occurring after an emotional or physical stress. Free-living cetaceans are threatened, daily, by a wide variety of stressful situations that affect their well-being and previous studies suggest that cetaceans would be especially predisposed to develop stress cardiomyopathies due to the characteristic of their cardiovascular adaptations. Different pathological entities have as central in its pathogenesis the acute stress so for this study we examined heart samples, from sixty-seven ashore cetaceans (48 stranded alive, 7 died from ship collision and 12 from bycatch) on the coast of the Canary Islands from 2000 to 2016 and on the coast of Andalucía from 2011 to 2014. As it occurs in the SCMP, all the above mentioned pathological entities share the same microscopic findings, characterized by acute or subacute cardiac degenerative necrotic lesions, presenting a perivascular pattern and consisting of: contraction band necrosis (49.25%), wavy fibers (43.28%), cytoplasmic hypereosinophilia and pyknotic nuclei (100%), perinuclear vacuolization (97.01%); vascular changes illustrated as congestion (67.41%), interstitial edema (38.81%) and hemorrhages (22.38%); infiltration of inflammatory cells (25.37%) and presence of interstitial myoglobin globules (43.28%). Immunohistochemically, it is also characteristic the depletion of cardiac troponin I, cardiac troponin C and myoglobin, besides the expression of fibrinogen in the degenerated/necrotic cardiomyocytes. Likewise, we intend to provide more knowledge about the pathologies and their implications in the conservation of cetaceans, through the reduction of mortality of these animals, their treatment and subsequent rehabilitation to the marine environment.