CARDIOVASCULAR PROCEDURES << BACK Myocardial Biopsy Myocardial biopsy is a diagnostic procedure in which a small piece of heart muscle tissue is removed for examination. It is performed similarly to (or as part of) cardiac catheterization. A catheter (thin tube) is inserted through a vein or artery. The catheter is then carefully threaded into the heart, using a type of X-ray images called fluoroscopy to guide the insertion. A catheter with jaws in its tip, called a bioptome, is then introduced. Once the bioptome is in place, three to five small pieces of tissue are removed from the heart muscle. This tissue is then examined to determine a diagnosis or treatment.