Discussion
TCM is a rare clinical diagnosis with a prevalence estimated between 0.7-2.5% of patients presenting with troponin-positive suspected ACS (5). Although the obscure etiology of TCM is still unclear, the clinical ubiquity of the disease has seen a rise as more cases are reported (6). Postmenopausal women within the range of 58-75 years old are a preeminent risk factor for this condition, with 90% of cases presenting within this age group (6). Despite the meager amount of literature available to establish prominent triggers and pathophysiology, there are several plausible factors described in the International Takotsubo Registry (ITR), based on 1750 patients. A physical trigger contributed to 36% of cases, while 28.5% of patients had no triggers at all. 27.7% had emotional liabilities, and 7.8% of patients had both emotional and physical stressors (7,8).
Among the variants of TCM, the classical type (also known as apical type; apical akinesia, basal hyperkinesia) is the most common variant (82%), followed by the midventricular type (14.6%), the reverse type (2%, also known as basal type; basal akinesia, apical hyperkinesia), and the focal type (1.5%) (8,10).
It is essential that wall motion abnormalities are appreciated via imaging and all potential causes of these abnormalities are elaborated to establish a diagnosis of TCM. The advent and addition of Magnetic Resonance Imaging (MRI) into cardiovascular imaging (CMRI) has proved to be a milestone when high-quality imaging is required. The results have been promising when applied to exempt other entities, such as myocarditis or myocardial infarction (MI), and validate the diagnosis of TCM (11). The myocardium is noticeably inflamed during the acute phase of TCM and is visualized as edema on CMRI, where the edematous region corresponds to the pathological area of wall motion abnormality. However, this can lead to a false-positive diagnosis as the findings are not exclusive to TCM and may also be observed in myocarditis or MI. This warrants the usage of gadolinium-based contrast, which is adopted by a technique known as late gadolinium enhancement (LGE), which can discriminate between TCM and other diagnoses, as the presence of LGE is testimonial in MI or myocarditis but is usually absent in TCM (11,12).
The reversible, transient left ventricular systolic function so particular to TCM is also described in cases of pheochromocytoma, acute brain injury as seen in subarachnoid hemorrhage, cerebrovascular events, and in various other neurologic conditions such a neurogenic stunned myocardium, where stress causing a catecholamine efflux is ordained to be the most plausible mechanism responsible. The histopathological picture, which is the manifestation of an upheaval of intracellular Ca+2 secondary to catecholamine surge, is distinguished by the finding of a contraction band necrosis, which is a shrunken area, walled-off with hypercontracted sarcomeres, housing islands of lysed myocytes in a sea of mononuclear inflammatory cells and densely eosinophilic transverse bands (13).
TCM, due to drug administration, is a very interesting etiological factor that further consolidates the role of catecholamines in developing this benign condition. A systematic review of case reports published by Kido et al. navigates the 157 cases reported of drug-induced TCM and elucidates the pragmatic relation between catecholamines and TCM, as 68.2% of these cases were the consequence of catecholamine-related rugs. 11% of cases were reportedly due to coronary spasms, while 14.3% of cases did not have any identifiable cause, as in the case we have presented above (14).
The case that we presented above is in accordance with the proposed criteria; hence, an unfaltering diagnosis of TCM has been made.
TCM and ACS are often mistakenly misdiagnosed owing to the overlapping clinical presentation. As the primary investigations, it is an intriguing ordeal if ECG and Echo can discriminate between ACS and TCM, but regrettably, there is a lack of data establishing any compelling link between a unique ECG pattern or specific findings on echocardiography and TCM. Patients with TCM may present with ECG findings strongly suggestive of MI, and inconclusive echo findings with focal or diffuse involvement of the myocardial wall, posing a challenge in the differentiation based on these two modalities. A comparative study found that 56% of cases of TCM report ST segment elevations in the anterior leads, and no ST segment elevations in the remaining 44%, among which 17% are non-specific or normal ECGs, while 17% reveal diffuse T-wave inversions, and 10% show healed anterior infarctions (16).
There are currently no clinical guidelines pertaining to the absolute treatment regimen for patients with TCM; however, the standard heart failure medications comprising Beta-blockers, ACE inhibitors, and diuretics are also employed in these cases. Patients are also counseled to avoid any identified trigger factors and are usually managed on Beta-blockers to prevent further episodes. The case we reported above was also managed as per the treatment layout presented above.
In conclusion, we described and explained a rare case of TCM involving a focal segment in an atypical age group with a presentation mimicking a Non-ST segment elevation Myocardial Infarction but with no identifiable triggers suggestive of aggravating TCM. Further genetic studies may explain the unusual presentation of our case and provide insights to better health outlook for such patients.