Cath Lab Digest - September 2007 - (Page 50)

50 ASK THE CLINICAL INSTRUCTOR SEPTEMBER 2007 Ask the Clinical Instructor A Q&A column for those new to the cath lab Questions are answered by: Todd Ginapp, EMT-P, RCIS, FSICP Todd is the Cardiology Manager for Memorial Hermann Southeast in Houston, Texas. He also teaches an online RCIS Review course for Spokane Community College, in Spokane, Washington, and regularly presents with RCIS Review Courses. “We see people with myocardial bridges, but nothing is done for them. What is the bridge and what is its significance?” — email from an online RCIS review student Figure 1. From Gorlin R. Dynamic Vascular Factors in the genesis of myocardial ischemia. J Am Coll Cardiol 1983 Mar;1(3):897-906. Figure 2. During systole, the coronary artery is squeezed by the myocardium surrounding it. M yocardial bridges can be quite impressive and quite dramatic. Even the newest of cath lab team members can see that “something isn’t right.” The clinical significance of this phenomena is questionable, however, and we’ll explain why. The normal coronary artery is an epicardial artery. It normally sits on top of the myocardium. Small branches come off of the artery and penetrate into the myocardium creating the microvasculature, which we have talked about in the past few articles. “Bridging” is an anomaly in which part of the artery has been encapsulated by the myocardium itself (Figure 1). Instead of laying on top of the myocardium, it is IN the myocardium. This will result in squeezing of the artery during systole (Figure 2). The artery looks normal in diastole when the myocardium is relaxed (Figure 3). The distances of these encapsulations can be anywhere from a few millimeters up to 3 centimeters or more. The longer the bridge, the more dramatic it is on angiography. This can occur in 5–12% of patients and is almost exclusively seen in the left anterior descending (LAD) artery.1 Blood flow limitations severe enough to cause ischemia (at rest) or myocardial infarction are unlikely. To realize this concept, we need to revisit coronary blood flow physiology. In the LAD and circumflex, blood flow through the artery to the myocardium occurs in diastole. We think of blood moving around during systole, so this can seem perplexing at times. Let’s clarify further. In previous articles, we talked about how the microvasculature that is in the myocardium can become ‘plugged,’ preventing flow. During systole, this same lack of blood flow can occur, but this time it is reduced because the vessels are being squeezed by the heart in systole. If you clench your fist, you cannot run water through it. However, during diastole (or “open fist”), the myocardium has relaxed and the blood can flow freely through the vessels and the microvasculature. It should be noted that this concept does not apply to the right coronary artery (RCA). The myocardium covered by the RCA has less muscle mass and does not affect the flow as much. Some severe bridging can be associated with angina, stress test-induced ischemia and infarction. Most of these occur in cases with the myocardium in a state of hypertrophy. These large hearts are at the end of their compensatory mechanisms, so when there is a state of increased contractility, in exercise for example, the worsening compression of the vessel may produce symptoms. However, these reports appear to be extremely rare. The female patient from Figures 2 and 3 presented to the cath lab with atypical chest pain. Figure 3. In this identical angulation from the same angiography sequence, we can see that the vessel is wide open during diastole.

Table of Contents Feed for the Digital Edition of Cath Lab Digest - September 2007

St. Dominic Hospital The Genous Bio-engineered R Stent Percutaneous Treatment of Peripheral Arterial Chronic Total Occlusions: Device Options and Clinical Outcomes Contents Clinical Editor’s Corner Percutaneous Revascularization of Peripheral Chronic Total Occlusion — Which Patients, Why, and How? Myocardial Infarction and Syncope: A Manifestation of the “Raynaud-Prinzmetal Syndrome”? Essential Technical Components of the Transradial Approach If You Build It, Will They Come? Evidence-Based Medicine with Drug-Eluting Stents Back to School: The Value of Education in Cardiovascular Services The ACVP Standards and Competencies: Are You Using Them Effectively? What Do You Think? My Experience with Fibromuscular Dysplasia and Stroke A Brief Review of Fibromuscular Dysplasia Letter to the Editor A Look at On-the-Job Training: Perceptions, Reality and Our Profession Doing the Wave: Inventory Management with RFID The Ten-Minute Interview with… Paul Pinsker, RCIS CLD’s Annual Salary Survey Harrisburg Area Community College Volunteer Survey CEU Education Center SICP* Section Ask the Clinical Instructor: A Q&A Column for Those New to the Cath Lab Clinical & Industry News

Cath Lab Digest - September 2007

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