Cardiac fluoroscopy

Fluoroscopy is another modality used to study cardiac motion and identify calcifications in the heart and mediastinum. Cardiac fluoroscopy is no longer routinely performed, but may be useful in certain clinical settings to detect coronary calcifications (i.e., when cardiac CT is unavailable or contraindicated), to image calcifications of the heart valves or pericardium, or to analyze the integrity of prosthetic valves. Because the chest radiograph is a static image of the moving heart, small calcifications blur and are not seen; however, dynamic fluoroscopy captures their movement. Fluoroscopy can additionally aid in determining whether a foreign body seen on chest radiograph is embedded in the heart or simply in the chest wall or other non-cardiovascular structure, since during a breath hold, the cardiovascular structures continue moving. For example, a bullet seen on chest radiograph could be lodged in the mediastinum or could have embolized and come to rest in one of the cardiac chambers; in the former case, the bullet would not move during a breath hold under fluoroscopic visualization, but in the latter case, the bullet would have a "to and fro" motion with the cardiac cycle.

Cardiac fluoroscopy is generally performed with the patient upright, similar to a chest radiograph. The position and projection used with depend on the structures under study. The aortic valve, for example, is best imaged in a left anterior oblique projection, and the mitral valve in a right anterior oblique view. Coronary artery calcifications are generally imaged in both the left anterior oblique view to visualize the right, left main, and left circumflex coronary arteries and the right anterior oblique view to visualize the left anterior descending artery.

Excursion of the sewing ring of a prosthetic valve greater than 10 degrees between systole and diastole suggests significant dehiscence of the prosthesis, and limited motion of mechanical valve parts during systole suggests suggests thrombus or vegetation on the prosthesis. These findings correlate well with 2-D echocardiographic findings, however, unlike Doppler echocardiography and angiography, fluoroscopy does not give any information about the degree of regurgitation.

Reference: Braunwald E, Ed. Heart Disease: A Textbook of Cardiovascular Medicine, 4th Ed.