Angiography

Catheterization of the heart is a somewhat invasive but commonly employed procedure for visualization of the heart's coronary vessels, chambers, valves, and/or great vessels. Basic catheterization techniques involve inserting a long, flexible, radio-opaque catheter into either a peripheral vein (for venous or right heart catheterization) or peripheral artery (for coronary artery or the left heart) under fluoroscopy (continuous X-ray observation). During this invasive procedure, a radio-opaque contrast medium is commonly injected into a cardiac vessel or chamber. Thus, this type of procedure may be used to visualize the anatomical features of the coronary arteries, cardiac veins, aorta, pulmonary blood vessels, and/or ventricles. Such investigations may provide pertinent clinical information about structural abnormalities in blood vessels that restrict flow (such as those caused by atherosclerotic plaque), abnormal ventricular blood volumes, inappropriate myocardial wall thicknesses, and/or altered wall motions. However, it should be noted that multiple contrast injections can be potentially acutely deleterious to patients, especially in those with compromised cardiac outputs [2].

To date, coronary artery angiography has been the primary visualization modality used clinically. Contrast is injected into the coronary arteries to identify existing occlusions or narrowing due to atherosclerotic plaques/calcifications. This visualization approach also provides the physician with roadmaps for the delivery of percutaneous therapies (e.g., a coronary stent) or for planning a subsequent coronary artery bypass surgery (i.e., determine where best to place suture so to avoid an attempted assess to a rigid calcified arterial wall) [3].

A sample venogram from an isolated heart preparation can be seen to the right. The green sheath contains a venogram balloon catheter. The balloon is inflated to block off antegrade flow and then contrast is injected retrograde, such that the coronary venous system (branching) is visible. Such imaging techniques are typically used for mapping the target vein for the delivery of a left-sided pacing lead (e.g., for biventricular pacing therapies).

Ultrasound

Various types of ultrasound are also used to visualize the coronary system. For instance, prior to lead implantation, tissue Doppler imaging can be utilized to identify the target implant region for a transvenous pacing lead placements [5]. Additionally, intravascular ultrasound (IVUS) can be used to identify the presence or absence of calcifications within the coronary arteries: e.g., during a procedure for the delivery of stents.

References

1. Coatrieux JL, Hernandez AI, Mabo P, Garreau M, Haigron P. Transvenous path finding in cardiac resynchronization therapy. Functional Imaging and Modeling of Heart, Proceedings, 2005:236-45.
2. Leon AR. Cardiac resynchronization therapy devices: Patient management and follow-up strategies. Rev Cardiovasc Med 2003;4 Suppl 2: S38-46.
3. von Ludinghausen M. The clinical anatomy of coronary arteries. Adv Anat Embryol Cell Biol 2003;167:III-VIII, 1-111.
4. Oginosawa Y, Abe H, Nakashima Y. Prevalence of venous anatomic variants and occlusion among patients undergoing implantation of transvenous leads. Pacing Clin Electrophysiol 2005;28:425-8.
5. Ansalone G, Giannantoni P, Ricci R, Trambaiolo P, Fedele F, Santini M. Doppler myocardial imaging to evaluate the effectiveness of pacing sites in patients receiving biventricular pacing. J Am Coll Cardiol 2002;39:489-99.