Research is underway in many areas of Takotsubo cardiomyopathy, being a rare and often missed diagnosis in cardiac medicine.
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Research on guidelines
Studies have been under way to help construct appropriate guidelines for the diagnosis of Takotsubo syndrome. The Mayo Clinic has already proposed a set of diagnostic criteria which have been modified. The 2004 Mayo guidelines are as follows:
- The mid-left ventricle should show dyskinesia, akinesia or hypokinesia irrespective of apical involvement. The wall motion abnormality should not be confined to the region supplied by a single epicardial vessel. The patient should have a history of strong and recurrent stress triggers.
- Angiography should be negative for acute rupture of an atherosclerotic plaque or coronary obstruction
- Novel ECG abnormalities such as ST-segment elevation or T-wave inversion, or a small increase in cardiac troponin;
- Absence of myocarditis and pheochromocytoma.
More work is ongoing to clarify the relevance of these criteria.
It is already clear that this syndrome is not confined to Japan, but is found to occur worldwide. The largest body of data with respect to cohort studies has come from the Nationwide Inpatient Sample (NIS) from the US.
Is TCM a cardiomyopathy?
The actual nature of the syndrome itself remains somewhat controversial. The American Heart Association considers it a primary and acquired cardiomyopathy, but the European Society of Cardiology has issued a position statement in which it considers it an unclassified cardiomyopathy. However, both agree that it is an acute cardiac syndrome with reversible cardiac failure.
The incidence and nature of the complications of Takotsubo syndrome remain a subject of study. Researchers need to identify the clinical risk factors that can help predict serious and acute complications such as ventricular rupture, outlet obstruction, and cardiac failure. The mechanisms by which they occur will also require clarification to help prevent and treat them.
Research on outcomes
While most practitioners consider TCM to be fully reversible, recent experiments show that one episode of TCM is followed by permanent weakening of heart function. This was supported by imaging techniques, which suggested scarring of the myocardium in addition to a reduction in its contractility and slower response to electrical activity in the left ventricle. Further work is going on to develop imaging tools which will help predict the extent of recovery as well as differentiate TCM from myocardial infarction.
Several recent studies have focused on a group of cases in which typical Takotsubo symptoms and signs were associated with apical sparing of the left ventricle with basal akinesia. This was termed inverted TCM. More studies currently exist to determine if this is due to variation in the innervation and vasculature of the myocardial wall.
Neuropsychiatric aspects of TCM
One unique aspect of broken heart syndrome is that over half of patients with this condition had a history of brain illness, manifesting as a psychiatric or neurologic disorder. This was either past or present, and could be acute or chronic. Some conditions found to be correlated with this finding include subarachnoid hemorrhage, traumatic brain injury, anxiety, ischemic stroke, and epilepsy.
This is important because coronary microcirculation depends upon brain-sourced neural signals, therefore the sudden loss of this innervation may account for the myocardial stunning which is so prominent a feature of TCM. The link between neuropsychiatric conditions and TCM is, therefore, one of great interest and much remains to be done to explore it.
What kind of stress triggers TCM?
This has been a vexing question since both emotional and physical events have been known to precede the first clinical signs of this condition. However, recent reviews have pointed out that anxiety, depression and chronic stress can all increase the chances of TCM. In fact, these patients are more likely than the general population to already have been diagnosed with anxiety disorders or other psychiatric illnesses. In other words, the existence of chronic worry, stress, and emotional fatigue, or hopelessness, may be significant risk factors for TCM. Such research seems to say that the acute trigger acts to produce TCM only in individuals already primed by chronic emotional depletion, or even as a result of their passing the critical point of emotional instability. The immense importance of this finding lies in the potential for prevention of TCM by timely and successful treatment of chronic overwhelming stress in such individuals.