The process of diagnosing TC is, to a large extent, one of exclusion of other conditions that it mimics (e.g. acute coronary syndrome and myocarditis). This is based on the clinical presentation, and findings from the electrocardiogram (ECG), biomarkers and cardiac imaging: 30–50 % of cases present with ST-segment elevation and one-third with deep T-wave inversion. Deep T-wave inversion and QT prolongation may be seen at presentation or develop in the days following admission. Using contemporary troponin assays, a modest elevation in troponin is universally detected. Routine measurement of catecholamine levels has not been shown to be helpful. Catecholamines may be measured in select cases where there is no clear trigger for TC to screen for a pheochromocytoma, especially if hypertension is present. Neither the troponin profile nor the ECG is helpful in differentiating TC from and acute myocardial infarction (MI).
Left ventriculography, echocardiography and magnetic resonance imaging demonstrate the typical wall motion abnormalities of TC (see Figure 1). The imaging modality used depends on the clinical setting, availability and local expertise. Left ventriculography is typically performed, and is very helpful, in cases where an acute coronary syndrome is initially suspected, but angiography demonstrates normal or mildly diseased arteries. Cardiac magnetic resonance imaging is useful in excluding myocarditis and infarction, especially in cases where there is diagnostic uncertainty. Transient proximal or mid-segment occlusion of a large left anterior descending artery may produce a regional wall motion abnormality pattern that mimics TC. Thus, it is essential to carefully evaluate for regional wall motion abnormality in the distribution of all three major epicardial coronary arteries in order to distinguish the classic form of TC from a left anterior descending artery territory infarct or stunning. In these cases, the presence of true lateral wall systolic dysfunction is useful in differentiating features between TC and anterior MI. Other variant patterns of regional wall motion abnormalities of TC have been described, and while less common, tend to be pathognomonic. These include the mid-ventricular variant where apical function is preserved, or inverted/reverse TC, where the apical (and often the mid) segments are preserved with akinesis/hypokinesis of the basal regions.
Coronary angiography is indicated whenever TC is suspected in order to exclude obstructive multi-vessel coronary artery disease. Computed tomography (CT) angiography may be appropriate in cases where cardiac catheterisation is not safe or feasible.
The Mayo Clinic diagnostic criteria are the most widely used and require all four of the following:14 i) presence of transient regional wall motion abnormality of the left (and often right) ventricular mid- segments with or without apical involvement. The regional wall motion abnormalities extend beyond a single epicardial vascular distribution. (Follow-up imaging is required to demonstrate that the ventricular dysfunction was transient); ii) absence of obstructive coronary disease or angiographic evidence of acute plaque rupture (TC may occasionally occur in patients with obstructive coronary atherosclerosis); iii) new electrocardiographic abnormalities (either ST-segment elevation and/ or T-wave inversion) or modest elevation in cardiac troponin; iv) exclusion of myocarditis and pheochromocytoma.