Precipitating Factors
In most cases, TTC presents shortly after the individual experiences a major emotional or physical stressor (see Figure 1). A prospective study of 136 patients presenting 
with TTC found that 47 % of the patients experience an emotional stressor, 42 % a physical stressor and 11 % had no evidence of any stressor.10 In the COUNTS study, 39 % patients experienced a preceding emotional trigger and 34 % patients a physical stressor.7 Emotional stressors range from public speaking, work conflicts/job concerns, anger, to hearing bad news such as death of a family member or a pet. Physical stressors include medical illness such as undergoing surgery or chemotherapy, a fall or drug use. Even though a clear precipitating stressor could not be identified in some TTC patients, the lack of a stressor does not exclude the possibility of diagnosing TTC.
Certain drugs are shown to be precipitating factors in TTC. Out of 58 patients with case reports of drug-induced TTC, 45 were due to medications that cause direct or indirect stimulation of the sympathetic nervous system (SNS).11 These included agents such as dobutamine, epinephrine, norepinephrine, ephedrine, ergonovine, atropine, nortriptyline and oxymetazoline.11 Levothyroxine has been linked to TTC, and although it does not act on the SNS, the cardiac effects of levothyroxine mimic those caused by catecholamines. Pazopanib is a vascular endothelial growth factor receptor antagonist that inhibits nitric oxide production, and increases sensitivity to catecholamines.11 Agents with no clear link to catecholamine activity including dypyridamole, potassium chloride, lumiracoxib, 5-fluoruracil and combretastatin have also been implicated in TTC.11