Urothelial carcinoma is a rare cause of cardiac metastasis, with only 25 cases reported in the literature. Furthermore, our case is unusual as there were multiple metastases. Fever has also been rarely reported as a presenting complaint.
Cardiac metastases are often clinically silent and are generally discovered during post-mortem examinations, or incidentally on imaging [1, 2]. Bussani et al.  conducted a study of 18,751 post-mortem examinations where they identified malignancy in 38.8% of cases, among which 9.1% (662 patients) had cardiac metastasis. From the 662 cases, 98.5% had metastases to other sites other than the heart, indicating that cardiac metastasis is usually a feature of widespread disease. The most common malignancies found to metastasise to the heart included lung, followed by breast and lymphoma or leukaemia. Urothelial carcinoma represented only 1.8% of all primary malignancies with cardiac metastasis, making it an exceptionally rare cause for cardiac metastases .
Pericardial involvement is the most frequently cited location of cardiac metastasis, followed by the myocardium; while the least common site is the endocardium . Specific to urothelial metastasis, the majority of the cases reported involved the myocardium (19 cases), while the remaining 5 cases involved the pericardium. One case reported a lesion limited to the endocardial layer [5,6,7,8,9,10,11,12,13]. Similar to our case, only two other cases involved multiple cardiac metastatic lesions from a urothelial primary; Ueda et al.  reported a case of right and left myocardial metastases, while Sugimoto et al.  reported multiple myocardial metastatic nodules.
Patients with cardiac metastasis are often asymptomatic and are primarily noted on post-mortem examination, as mentioned above. If symptomatic, the symptoms reported by patients are often ambiguous. Symptoms of other organ metastases may be prevalent by the time metastasis to the heart occurs, explaining why cardiac metastases often remain undiagnosed. However, cardiac-specific symptoms may occur depending on the site of the metastatic lesions. Patients with pericardial metastasis may present with a pericarditis-like picture, including the development of a pericardial effusion and possibly tamponade [7, 9, 15]. Myocardial involvement may result in arrhythmic complications including life-threatening ventricular fibrillation or complete atrioventricular block [6, 16, 17]. Myocardial involvement may also compromise cardiac output mimicking congestive heart failure. Metastasis to the endocardium may cause left or right outflow obstruction with cardiogenic shock . Any of the described symptoms in a patient diagnosed with malignancy should raise concerns for possible cardiac metastasis. Among the 25 reported cases of cardiac metastases from urothelial carcinoma, many reported non-specific symptoms such as fatigue, cough, and weight loss, among others. Shortness of breath was also reported which may have been secondary to tamponade, a compromised cardiac output or lung metastasis. Among these 25 patients, only 2 cases reported fever as one of the presenting symptoms, similar to our case [7, 8].
Imaging modalities are the main investigations aiding in the diagnosis of cardiac metastasis, however, an electrocardiogram (ECG) may also contribute by revealing low voltage complexes (due to a pericardial effusion), arrhythmias, or nonspecific ST-T wave abnormalities; the latter being reported in our case . Chest x-ray and echocardiography may reveal a pericardial effusion, while echocardiography may also identify cardiac masses . CT, CMR or positron emission tomography-computed tomography (PET-CT) offer more definite imaging to localise and characterise cardiac masses while excluding differentials such as intracardiac thrombus, vegetations, and benign lesions. Our case offers an insight into the role of CMR in cardiac metastasis diagnosis; an imaging modality that was not frequently used in the literature of similar cases.
CMR protocols vary depending on the institution and involve different sequences which must be tailored towards the suspected cardiac pathology. Commonly used sequences include black-blood T1-weighted sequences (with and without fat saturation and before and after contrast enhancement), black-blood T2-weighted imaging, cine imaging with a steady-state free-precession (SSFP) sequence and early and late gadolinium enhancement (LGE) imaging . All these sequences were included in the reported case as part of the institution’s tumour protocol. Characteristics indicative of cardiac metastasis include smooth and spherical lesions, low or isointense T1-weighted images, hyperintense T2-weighted (owing to the high fluid content of malignant lesions), heterogenous LGE, no signal change on fat suppression sequence (absence of fat), presence of pericardial effusion (likely haemorrhagic), and haemorrhage within the mass [19,20,21]. The tumours in our case demonstrated the above-mentioned characteristics (Figs. 2, 3, 4, 5). Although a clinical diagnosis of cardiac metastasis can often be made on imaging, tissue histology remains the investigation of choice for diagnosis . Cardiac biopsy and treatment of the patient’s condition in the case were deemed ineffectual due to his poor condition.