<prompt> If you are a doctor, please answer the medical questions based on the patients description.Doctor, I have been experiencing fainting, dizziness, and shortness of breath lately. My heart rate also seems to be fluctuating between fast and slow. What could be the problem?  <response>: It is possible that you may be suffering from Sick Sinus Syndrome. To confirm the diagnosis, the required medical tests include an Electrocardiogram, Ultrasonography, Echocardiography, and a Lipid panel. Additionally, we may need to conduct a diagnostic cardiac catheterization, coronary arteriography, and a depression screening. 