The goal of this observational study is to keep track of the cardiological follow-up of patients who have undergone back surgery because of symptomatic narrowing of the spinal canal and in whom microscopic examination of the tissue removed during this surgery showed a high amount of local deposits of small proteins. This finding may be an early sign of a condition in which other organs (especially the heart) may also be affected by these proteins, called amyloidosis. Patients who participate in this study, will be followed up for life. During the first routine consultation with the cardiologist, the physician-investigator will collect information, such as demographics (age, weight, height, gender), medical history, medication, symptoms and the results of prescribed examinations. These examinations include microscopic examination of tissue removed during the surgery, blood tests, electrocardiography, echocardiography and a bone scan. These examinations are clinically necessary and appropriate, and patients should undergo them even without participating in the study.