SNOWMASS, COLO. – according to Matthew W. Martinez, MD, medical director of the Sports Cardiology and Hypertrophic Cardiomyopathy Center at the Lehigh Valley Health Network in Allentown, Pa.
“The MRI may be the single test that best helps you sort out when you’re not quite sure. If you think about a single study that’s going to help you identify cardiac arrest etiologies – hypertrophic cardiomyopathy, myocarditis, anomalous coronaries, left-sided disease, right-sided disease like arrhythmogenic right ventricular cardiomyopathy, valvular heart disease, aortic disease – MRI is a very powerful tool because it will help you evaluate all of those groups more than 90% of the time,” he said at the Annual Cardiovascular Conference at Snowmass sponsored by the American College of Cardiology.
, who serves as lead cardiologist for U.S. Major League Soccer and is also heavily involved with the National Football League, spends a lot of time with elite professional or Olympic athletes who fall into what he calls “the gray zone,” with a left ventricular wall thickness of 12-15 mm as measured on echocardiography. While that would clearly be considered abnormal in a nonathlete or a recreational sports enthusiast, his experience as well as that of other sports cardiologists working with professional soccer, football, and basketball players, bicyclists, and high-level track and field competitors has been that wall thickness in the 12- to 15-mm range in elite athletes can represent physiological adaptation to their enormous cardiovascular workloads. For example, more than 10% of National Football League players have a maximum left ventricular wall thickness of 13 mm or more, as do more than 10% of National Basketball Association players.
But what if that echocardiographic measurement of wall thickness is off by a millimeter or two, as is often par for the course?
“It’s well described that MRI gives a better look at wall thickness than echocardiography, especially where there’s areas of hypertrophy next to normal wall. In that gray zone, where we have to know if it’s really 10-12 or 14-16 mm, the MRI better identifies the actual thickness,” he said.
In addition, cardiac MRI readily provides accurate, reproducible measurements of left and right ventricular chamber size. But the most important way in which cardiac MRI helps in evaluating the significance of cardiac remodeling in athletes is via the gadolinium study. Late gadolinium enhancement is a concerning finding. It indicates the presence of myocardial fibrosis and scar, which at least in the general population is a prognostic sign for worse outcome.
“If you detect fibrosis, the search for pathology has to start,” the cardiologist emphasized.
He noted that the most comprehensive review to date of myocardial fibrosis in endurance athletes identified the intraventricular septum and the junction of the right ventricle and septum as the most common sites of involvement. The investigators concluded that, while there is a lack of compelling data on the clinical impact and prognosis of myocardial fibrosis in athletes, potential mechanisms include exercise-induced repetitive microinjury, pulmonary artery pressure overload, genetic predisposition, and silent myocarditis ().
That being said about the value of cardiac MRI as a tiebreaker, Dr. Martinez asserted that “there’s no specific test that’s going to get you out of jail. ... I would submit to you that you have to load the boat. Be comprehensive and try to build a case for one side or the other. And I would encourage you to ask for help; we do it all the time.”
Dilated chambers outside the normal range are common in competitive athletes. Don’t accept the echocardiographic hard numeric cutoffs that have been established as “normal” in the general population. For example, 36% of National Basketball Association players have a left ventricular end diastolic dimension (LVEDD) greater than 60 mm.
“I’ve seen LVEDDs up to 70 mm in cyclists. And all but a handful have a normal left ventricular ejection fraction greater than 50%,” he noted.
Dilated chambers in elite athletes are reassuring, provided stroke volume is preserved or, as is more often the case, enhanced.
“One of the hallmarks of being an athlete is the ability to suck in blood and increase stroke volume as a result. A typical stroke volume in an athlete is well above normal, with 85-90 cc or more being common. On tissue Doppler assessment, you shouldn’t have a normal inflow pattern or normal relaxation. A septal E prime velocity of 11-14 cm/sec is what I typically expect in an athlete. A lower E prime velocity suggests early pathologic change. If you find an E prime velocity of less than 9 cm/sec on tissue Doppler, or an elevated filling pressure like 15 mm Hg, that correlates with a greater than 90% sensitivity for pathology, such as hypertrophic cardiomyopathy. The average E prime velocity in Major League Soccer players is about 13 cm/sec, so that’s an important number to keep in your head,” according to the cardiologist.
Cardiac remodeling in elite athletes tends towards one of two forms, depending upon their sport. Endurance athletes, such as marathon runners, are repetitively volume challenged, so expect a tendency towards aortic regurgitation. For pressure-challenged athletes, such as power weightlifters, the tendency is toward aortic stenosis.
“But also expect a blend. It’s rarely just one or the other. Understanding that can help you discern the gray zone athlete,” he said.
Dr. Martinez reported having no financial conflicts of interest regarding his presentation.