This study suggests that while THI enhances imaging of difficult to visualize valves, it may overestimate mitral and aortic valve thickness. This could lead to overdiagnosis and unnecessary follow-up studies. Cardiologists interpreting THI echocardiograms should become familiar with the modality's shortcomings.

These images are from a 51-year-old man who presented to the emergency department with an anterior ST-segment elevation myocardial infarction, Killip class I. During emergency coronary angiography, we were unable to engage the right coronary artery (RCA) with a JR4 catheter (Cordis, Bridgewater, New Jersey) and proceeded to engage the left coronary artery with an XB3.5 guiding Figure 1. Angiographic Images (A) LAO caudal angiography pre-PCI. (B to D) RAO caudal, AP cranial, and LAO caudal angiography, respectively, post-PCI. (E) CT angiography. CT ϭ computed tomography; LAO ϭ left anterior oblique; PCI ϭ percutaneous coronary intervention; RAO ϭ right anterior oblique.

This is a unique case of Merkel cell carcinoma, a rare neuroendocrine tumor, metastasizing to the heart and inducing a progression of cardiac complications such as new-onset atrial fibrillation, malignant pericardial effusion with tamponade physiology, first-degree heart block, and complete heart block. Metastases to the heart are relatively rare but should be suspected if a patient with a known neoplasm presents with new cardiac manifestations. This is the first case report of cardiac metastases from Merkel cell carcinoma causing cardiac tamponade or complete heart block. This case highlights the clinical decision-making involved in managing cardiac tamponade and complete heart block in the setting of metastatic disease to the heart.