Stress cardiomyopathy in stranded cetaceans: a histological, histochemical and immunohistochemical study

What is it about?

Both humans and other animals, have evolved mechanisms to cope with stress in their lives, but when this is excessive or prolonged over time they can develop different diseases and induce myocardial injury. An example is the Stress Cardiomyopathy (SCMP), or “Apical Ballooning Syndrome”, Takotsubo Disease”, otherwise known as the “Broken Heart Syndrome” in the popular press, which is a reversible cardiomyopathy in humans, most often occurring after an emotional or physical stress. Several cases have been reported globally but it is under-recognized and often misdiagnosed. 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. Here, we aimed to characterize the stress cardiomyopathy of stranded cetaceans, as an injury resulting from extreme stress responses, based on pathological analyses (histological, histochemical, and immunohistochemical). Specifically, we examined heart samples, from 67 cetaceans found ashore (48 live strandings, seven dead from ship collision, and 12 dead 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 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. This study advances current knowledge about the pathologies of cetaceans and their implications on conserving this group of animals by reducing mortality and enhancing their treatment and subsequent rehabilitation to the marine environment.

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