Takotsubo cardiomyopathy

Takotsubo cardiomyopathy or takotsubo syndrome (TTS), also known as stress cardiomyopathy, is a type of non-ischemic cardiomyopathy in which there is a sudden temporary weakening of the muscular portion of the heart. It usually appears after a significant stressor, either physical or emotional; when caused by the latter, the condition is sometimes called broken heart syndrome. Examples of physical stressors that can cause TTS are sepsis, shock, subarachnoid hemorrhage, and pheochromocytoma. Emotional stressors include bereavement, divorce, or the loss of a job. Reviews suggest that of patients diagnosed with the condition, about 70–80% recently experienced a major stressor, including 41–50% with a physical stressor and 26–30% with an emotional stressor. TTS can also appear in patients who have not experienced major stressors. The pathophysiology is not well understood, but a sudden massive surge of catecholamines such as adrenaline and noradrenaline from extreme stress or a tumor secreting these chemicals is thought to play a central role. Excess catecholamines, when released directly by nerves that stimulate cardiac muscle cells, have a toxic effect and can lead to decreased cardiac muscular function or "stunning". Further, this adrenaline surge triggers the arteries to tighten, thereby raising blood pressure and placing more stress on the heart, and may lead to spasm of the coronary arteries that supply blood to the heart muscle. This impairs the arteries from delivering adequate blood flow and oxygen to the heart muscle. Together, these events can lead to congestive heart failure and decrease the heart's output of blood with each squeeze. Takotsubo cardiomyopathy occurs worldwide. The condition is thought to be responsible for 2% of all acute coronary syndrome cases presenting to hospitals. Although TTS has generally been considered a self-limiting disease, spontaneously resolving over the course of days to weeks, contemporary observations show that "a subset of TTS patients may present with symptoms arising from its complications, e.g. heart failure, pulmonary edema, stroke, cardiogenic shock, or cardiac arrest". This does not imply that rates of shock/death of TTS are comparable to those of acute coronary syndrome, but that patients with acute complications may co-occur with TTS. These cases of shock and death have been associated with the occurrence of TTS secondary to an inciting physical stressor such as hemorrhage, brain injury sepsis, pulmonary embolism or severe chronic obstructive pulmonary disease (COPD). It occurs more commonly in postmenopausal women.

Signs and symptoms The typical presentation of takotsubo cardiomyopathy is chest pain with or without shortness of breath and associated electrocardiogram (ECG) changes mimicking an anterior wall myocardial infarction. During the course of evaluation of the patient, a bulging out of the left ventricular apex with a hypercontractile base of the left ventricle is often noted. It is the hallmark bulging-out of the apex of the heart with preserved function of the base that earned the syndrome the name takotsubo ("octopus trap") in Japan, where it was first described. Stress is the main factor in takotsubo cardiomyopathy, with more than 85% of cases set in motion by either a physically or emotionally stressful event that prefaces the start of symptoms. Acute asthma, surgery, subarachnoid hemorrhage, chemotherapy, and stroke are examples of physical stressors. In a few cases, the stress may be a happy event.

Risk factors

Stress trigger Although there have been documented cases of TTS without a triggering stressor, it is widely recognized that TTS is preceded by a stressful or emotional event. Case series looking at large groups of patients report that some patients develop takotsubo cardiomyopathy after experiencing emotional stress. Some patients have a preceding clinical stressor (such as a brain injury, asthma attack or exacerbation of a chronic illness) and research has indicated that this type of stress may even occur more often than emotionally stressful triggers. Roughly one-third of patients have no preceding stressful event. A 2009 large case series from Europe found that takotsubo cardiomyopathy was slightly more frequent during the winter season. This may be related to two possible/suspected pathophysiological causes: coronary spasms of microvessels, which are more prevalent in cold weather, and viral infections – such as Parvovirus B19 – which occur more frequently during the winter.

Gender Postmenopausal women are at greatest risk of developing TTS. This has led some researchers to theorize about the possible protective effects of estrogen in preventing TTS.

Genetic risk factors As of 2014 it is being investigated whether certain genetic traits associated with catecholamine receptors found on cardiac muscle cells play a role in the development of TTS. There is limited evidence tying TTS directly to a specific genetic expression or mutation, however there is a widely held hypothesis supporting the idea of the interaction between environmental factors and the interplay of genetic predisposition leading to the susceptibility to microvascular alterations that contribute to the TTS disease process.

Hormonal dysregulation Certain endocrine diseases including pheochromocytoma and thyrotoxicosis have been identified as potential risk factors for TTS. The relationship between thyroid function and stress cardiomyopathy is marked by a dual phenotype, where both impending primary hyperthyroidism and a high set point of thyroid homeostasis (encoding type 2 allostatic load) are common phenomena. A multi-centre observation study found normal thyroid function to be the exception rather than the rule in TTS. Especially hyperthyroidism is highly prevalent in takotsubo cardiomyopathy, and it seems to predict a poor prognosis in terms of complications and mortality. This observation was confirmed by results of the international GEIST registry, which demonstrated that thyrotoxicosis is associated with significantly increased fatality, whereas hypothyroidism indicates a better survival.

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