The goal of this research study is to further understand the physiological mechanisms involved in a heart condition called takotsubo cardiomyopathy, also known as broken heart syndrome. Furthermore, the investigators will be assessing the effects different cardiac medications have on these physiological mechanisms.

This will be achieved by performing cardiac MRI scans using a special dye called manganese. Manganese uptake in the heart is altered in patients with takotsubo cardiomyopathy. The investigators will study the effects that different cardiac medications have on manganese uptake.

Takotsubo cardiomyopathy is a medical condition which presents similarly to a heart attack. It is usually caused by physical or emotional stress and typically affects women aged 50-74. It causes sudden severe impairment in heart muscle function, which was previously thought to get better in a matter of weeks. However, 1 in 10 patients will die in hospital and those that recover have substantially reduced long-term survival. There is no definitive treatment for takotsubo cardiomyopathy at present. Standard heart scans carried out in clinical care suggest that takotsubo cardiomyopathy gets better within a few weeks. However, patients don't always feel better at this stage.

Researchers at the University of Edinburgh have previously demonstrated that performing an MRI scan of the heart using a special dye called manganese shows that changes in the heart muscle persist for months to years after the original diagnosis of takotsubo cardiomyopathy. The investigators propose to assess the effects of established heart failure therapy on patients with takotsubo cardiomyopathy, specifically the effects this has on manganese-enhanced MRI scans.

Participants will be divided into two study groups based on the timing of their diagnoses. Participants with a recent diagnosis less than 3 months ago will be allocated to receive Bisoprolol, Valsartan or no medication. Participants with a diagnosis more than 6 months ago will be allocated to receive Sacubitril/Valsartan or Dapaglifozin for 3 months then will change to the alternative medication for 3 months with a 1-month wash-out period in between. Participants will attend for study visits every few weeks-months to assess the effects of the medication. At the study visits the participants will undergo a range of investigations including the manganese-enhanced MRI scan, echocardiogram, ECG, walking test and blood tests. Furthermore, participants will undergo a clinical assessment by the study doctor and be asked to complete a symptom questionnaire.

Inclusion Criteria:

• Males and females >18 years of age
• Clinical presentation of takotsubo cardiomyopathy
• Have capacity to give formal consent

Exclusion Criteria:

• Unable to tolerate or contraindication to magnetic resonance imaging
• Renal failure (estimated glomerular filtration rate <30 mL/min/1.73 m2) - this would be assessed by performing a blood test
• Prior history of cardiomyopathy
• Current pregnancy
• Weight greater than 250kg
• Severe asthma for study 1 (given Bisoprolol is contraindicated in this condition)
• Type 1 diabetes mellitus for study 2 (given Dapaglifozin is contraindicated in this population)
• Significant hypotension (given the medications prescribed as part of the study can also cause hypotension as a side effect)
• Significant bradycardia for study 1 (given Bisoprolol can exacerbate any pre-existing significant bradycardia)
• Prescribed Digoxin (this medication interacts with the Manganese)
• Unable to give formal consent