Takotsubo Cardiomyopathy Workup

Cardiac markers, specifically troponin I and T, are elevated in 90% of patients with takotsubo cardiomyopathy (TCM), although to a lesser magnitude than is seen in ST-segment elevation myocardial infarction (STEMI). The brain natriuretic peptide level is also frequently elevated.

As with any patient in whom acute coronary syndrome is suspected, electrocardiography should be the initial test obtained soon after presentation to the emergency department.

Transthoracic echocardiography provides a quick method of diagnosing wall motion abnormalities typically seen in TCM, specifically hypokinesis or akinesis of the midsegment and apical segment of the left ventricle. The diagnosis of TCM is typically confirmed with cardiac angiography.

At the time of admission, the mean troponin T level has been found to be 0.49 ng/mL (normal < 0.01) and the mean troponin I level has been reported as 4.2 ng/mL (normal < 0.04), in patients with takotsubo cardiomyopathy (TCM), while mean peak values during hospitalization for troponin T and troponin I have been demonstrated to be 0.64 and 8.6 ng/mL, respectively.

As mentioned, the brain natriuretic peptide level is also frequently elevated, especially in those patients demonstrating left heart failure, as it is an indicator of increased left ventricular end-diastolic pressures that result from the stunned myocardium.

Several studies looked at levels of circulating catecholamines in the acute phase and found that nearly 75% of patients had elevations markedly higher than did patients with STEMI.^{[21, 22]}

As previously stated, transthoracic echocardiography provides a quick method of diagnosing wall-motion abnormalities typically seen in takotsubo cardiomyopathy (TCM), specifically hypokinesis or akinesis of the midsegment and apical segment of the left ventricle. Perhaps most importantly, these wall motion abnormalities extend beyond the distribution of any single coronary artery.

The left ventricular ejection fraction (LVEF) can be estimated by echocardiogram, cardiac magnetic resonance imaging (MRI), or left ventriculography. Mean LVEF on admission has been found to range from 20-49%.

Echocardiography is commonly used in following the resolution of the cardiomyopathy and impaired left ventricular function, with LVEF improving to 59-76% on average, by day 18. (See the images below.)

The diagnosis of takotsubo cardiomyopathy (TCM) is typically confirmed in the cardiac catheterization laboratory. In a review of 240 patients diagnosed with TCM, 211 were found to have completely normal coronary arteries, whereas the remainder had noncritical stenoses. The prevalence of normal coronary arteries by angiography in patients presenting with STEMI ranges from 1-12%. Aside from TCM, this phenomenon may be explained by transient vessel occlusion with spontaneous thrombolysis, by vasospasm, or it may be drug related.

Left ventriculography is perhaps the best imaging modality to demonstrate the pathognomonic wall motion and to evaluate LVEF.^{[17, 18]} (See the images below.)

As with any patient in whom acute coronary syndrome is suspected, ECG should be the initial test obtained soon after presentation to the emergency department. ST-segment elevation (67-75%) and T-wave inversion (61%) are the most common abnormalities seen on the initial ECG. Ninety-five percent of ST-elevations have been found to involve the precordial leads and to be maximal in leads V₂ -V₃. When compared with patients with STEMI from left anterior descending (LAD) coronary artery occlusion, the amplitude of ST-segment elevations in patients with takotsubo cardiomyopathy (TCM) was significantly less. (See the images below.)

An initially normal or nonspecific ECG finding is seen in 15% of patients with TCM. Diffuse T-wave inversions tend to occur in the days and weeks following presentation as the ST-segments normalize. No reliable way to differentiate TCM from STEMI is possible based solely on ECG findings.^{[17, 20]}

In a retrospective study of 33 patients with TCM, the authors proposed ECG criteria to distinguish TCM from anterior acute myocardial infarction (AMI) in those who presented within 6 hours of symptom onset. The combination of absent abnormal Q-waves, absent reciprocal changes, lack of ST-segment elevation in lead V₁, and presence of ST-segment elevation in lead aVR had more than 91% sensitivity and 96% specificity for TCM.^[23] (See the images below.)

Chest radiographs in takotsubo cardiomyopathy (TCM) are often normal, but they may demonstrate pulmonary edema.

Cardiac magnetic resonance imaging may be a diagnostic modality uniquely suited for establishing the diagnosis of TCM by accurately visualizing regional wall motion abnormalities, quantifying ventricular function, and identifying reversible injury to the myocardium by the presence of edema/inflammation and the absence of necrosis/fibrosis. This technology may give new insight into the pathophysiology of TCM and be of potential use at acute presentation, broadening recognition and improving clinical outcomes.^[24]

In addition to evaluating wall-motion abnormalities and LVEF, cardiac MRI has been found to differentiate TCM, characterized by the absence of delayed gadolinium hyperenhancement, from myocardial infarction and myocarditis, in which the opposite occurs.

Although not indicated in the initial evaluation of patients with TCM, reports are emerging of the use of coronary computed tomography (CT) angiography in the subsequent evaluation of patients with the disorder.^[25]