Many patients believe that one can also assess the coronary arteries during this examination, known as the coronary vessels. Those are the three vessels that lie outside the heart and supply blood to the heart muscle itself. If one of these vessels becomes blocked, it can lead to a heart attack. In the case of chronic narrowing, the patient may experience chest pressure (angina pectoris) or shortness of breath. However, the coronary arteries have a diameter of approximately 2.5 mm, which is too small to be seen and assessed from the outside using ultrasound. The assessment of the coronary arteries is done through a coronary CT (contrast agent required) or, in some cases, through a myocardial scintigraphy (radioactive examination). Ultimately, the most accurate examination is the cardiac catheterization itself.