Paul Thompson, MD: Be Wary of Normal Stress Tests in Athletes with Possible Cardiac Symptoms

Paul Thompson, MD

Due to my interest in exercise and sports cardiology, I am often called by physicians whose patients have had sudden death during exercise. The most tragic deaths are those due to anomalous coronary artery origin (ACAO).

Almost always, the possibility of ACAO was dismissed because the stress test was normal. For unclear reasons, stress tests in young adults with ACAO are often normal. This phenomenon of normal stress tests was, to my knowledge, first reported by Christina Basso, MD, PhD, with Barry Maron, MD, in 2000.^1​

They reported 27 young athletes who died during or immediately after exercise. Of these, 15 had no symptoms before death, but 12 had symptoms including chest discomfort and syncope/near syncope. To my point, however, 6 had exercise tests that were considered normal in all 6 athletes! Granted there is ascertainment bias because it’s a study of athletes who died and those with positive stress tests were likely fixed, but the point is that a negative stress test does not mean “case dismissed”.

The classic story is of a young person who is usually mid- to late-teens who presents with anginal-like chest pain, and/or syncope/near syncope, and/or exertional dyspnea, and/or exertional “anxiety” and/or new onset “exercise asthma”. There is no clear explanation as to why they often present around puberty, but I have postulated that the increase in body, and therefore heart size, out-strips the anomalous coronary artery’s ability to supply sufficient blood for the demands of exercise. Also, for unclear reasons, the symptoms are variable.

The patient can experience symptoms during one exercise bout but not during a subsequent, similar workout. I am usually reassured when an athlete has had symptoms for several years before they see me, but young adults with AOCAs often have symptoms for several years before diagnosis or catastrophe. Any young athlete with anginal symptoms warrants a CTA to look for AOCA or an MRI even if the stress test is normal.

There is an increase in the diagnosis of AOCAs in adults because of the increased use of CTAs. Some of these newly diagnosed patients wind up undergoing CABG. That is often a bad idea.

Adults with AOCAs are survivors. If the artery was going to get them into trouble, it usually does so before adulthood. I know of individuals in their 50’s-60’s who had CABG for asymptomatic AOCA often after vague symptoms lead to angiography. CABG is usually the wrong approach.

For CABG to be beneficial the bypass graft has to stay open. Because even a symptomatic ACA is obstructive and causes symptoms only intermittently, there is competitive flow to the heart via both the ACA and by the bypass graft. Given the competitive flow from two sources, one will close—usually the vein graft or the LIMA does not grow with flow and becomes atretic. The better treatment of anomalous coronary arteries is usually not bypass but either reimplantation to the correct sinus or unroofing if the ACA runs in the aortic wall.

Why ACAs cause symptoms and sudden cardiac death remains unclear. A left coronary ACAO is always more dangerous than a right because the left system supplies more of the heart. It was thought that an arterial course between the pulmonary artery and aorta was most dangerous because the ACA was squeezed between the pulmonary artery and aorta by the increased stroke-volume in both great vessels.

Recent thought suggests that either an acute angle takeoff of the coronary artery from the aorta instead of the normal straight exit or a course of the ACA within the aortic adventitia is the ultimate cause of ischemia. The acute angle takeoff means that the opening is compromised as the aorta expands with blood during exercise. An artery coursing in the aortic adventitia tissue would be similarly compromised by the increase in stroke volume.

Earlier I said that adults with AOCA are likely survivors and probably should be left alone. There is an exception. The ACA’s course is not as straight as normal. This angulation creates flow turbulence and turbulence accelerates atherosclerosis. You get atherosclerosis where arteries twist, turn or bend, like in the coronaries, the aortic bifurcation, etc.

We reported a 21-year-old with classic angina and an anomalous right coronary artery (RCA)^.2 I was surprised that he had symptoms but when he was surgically repaired, his ACA had tons of atherosclerosis in the proximal RCA. Consequently, I treat anomalous coronary arteries with lifelong low-dose statin if they are young or higher dose statins if they are older to help prevent coronary atherosclerosis even if they are asymptomatic and even if I think they are a survivor and should otherwise be left alone.