Screening athletes for cardiac abnormalities that increase the risk of exertional sudden cardiac death continues to be a problematic issue for sports medicine physicians. Detection can be difficult even in the best of circumstances, while even low “false-positive” rates lead to substantial medical and financial consequences. Two recent articles in ACSM journals make important contributions toward improving the accurate detection of cardiac abnormalities in athletes.
Keeping athletes safe and competitive in hot and humid environments is a common challenge faced by sports medicine physicians and athletic trainers. In the May 2017 issue of Medicine & Science in Sports & Exercise®, Schranner and colleagues report the results of their study comparing different cooling methods during a simulated tennis match. These findings have potential applications beyond just tennis.
Coronary Artery Evaluation by Screening Echocardiogram in Intercollegiate Athletes
Anomalies of the origin of the coronary arteries are the second most common cause of sudden cardiac death in young athletes. These anomalies can be identified on echocardiogram, but the ability to detect them in a screening situation has not been evaluated. Hoyt and colleagues (2) report their experience in identifying the origin and proximal course of the coronary arteries by screening echocardiograms of collegiate athletes in the May 2017 issue of Medicine & Science in Sports & Exercise®. Screening transthoracic echocardiograms were done by three registered sonographers on 146 intercollegiate athletes representing 22 sports and six ethnicities. The echocardiograms were independently read by two pediatric cardiologists with experience in congenital heart disease and sports cardiology. Particular attention was given to visualization of the right and left coronary artery ostia and proximal courses. The right and left coronary artery ostia were visualized in 98% of athletes, proximal course of the RCA in 82%, and proximal course of the LCA in 81%. Interobserver agreement between readers was 85.6% for RCA ostium and proximal course, 100% for left coronary ostium, and 84.9% for LCA proximal course. No coronary anomalies were found.
There are features of this study that limit its interpretation and generalizability. The ability of the echocardiogram to detect coronary artery anomalies could not be determined because no coronary anomalies were seen, and no further investigations were done to determine if there were anomalies that were not identified. The study was done in an ideal setting, with a cardiologist experienced in congenital heart disease and the imaging of coronary arteries present to oversee the acquisition of the echocardiograms. In addition, the echocardiograms were read by pediatric cardiologists with expertise in congenital heart disease and sports cardiology. These conditions would be difficult to recreate on a large scale for all athlete cardiac screenings. Detection accuracy would undoubtedly be less when applied in less ideal settings. However, the study showed that under optimal conditions, the coronary arteries could be reliably observed by echocardiogram in the vast majority of athletes. The addition of coronary artery assessment could potentially increase the ability of screening echocardiography to prevent sudden cardiac death in young athletes.
The Complex Phenotype of the Athletes Heart: Implications for Preparticipation Screening
A major obstacle to effective cardiac screening of athletes is a full understanding of the physiologic, nonpathologic cardiac adaptations to athletic training. Brown and colleagues postulate that an individualized approach to cardiac screening that includes demographic and training variables will improve diagnostic accuracy of screening tests. Their in-depth research overview, published in the April 2017 issue of Exercise and Sport Sciences Reviews, looks at the current knowledge of the impact of different training regimens on cardiac structure and function in athletes grouped by age, ethnicity, sex, and body size (1). Each of these factors may influence the physiologic athletic heart and its associated findings on cardiac tests such as the ECG and echocardiogram.
The review by Brown and colleagues raises more questions than answers, and demonstrates our lack of knowledge regarding the interaction of factors that determine cardiac adaptations to athletic training. The authors provide evidence that the traditional model of exercise induced cardiac remodeling, wherein endurance training induces eccentric left ventricle hypertrophy and strength training induces concentric left ventricle hypertrophy, is too simplistic. They also focus on adaptations of cardiac chambers other than the left ventricle, and how these chambers influence cardiac assessments. They make a strong case that an “individualized approach” to cardiac screening that takes into account specific training, ethnicity, sex, and fat-free mass, is necessary to effectively make the distinction between physiologic and pathologic cardiac structure and function in athletes.
In-Play Cooling Interventions for Simulated Match-Play Tennis in Hot/Humid Conditions
Schranner and colleagues (3) devised an intricate treadmill exercise protocol to compare the cooling effectiveness of two methods of cooling during tennis matches. The standard cooling method in International Tennis Federation (ITF) matches is an “ice towel” (ICE) method consisting of the application of ice wrapped in a wet towel around the athlete’s neck, with damp cold towels simultaneously placed on the head and thighs. This method was compared to a fan with skin wetting method (FAN), in which subjects dampened their neck, face, arms and thighs with cool water applied with a sponge, followed by cooling with a fan at an air velocity of 6.4 m·s−1 placed 1.5 m in front of the subject. The preprogrammed exercise protocol was specifically designed to simulate the metabolic load of a tennis match consisting of four sets of eight games (six points each) per set. Tennis match play was simulated by variations in brief intervals of running at top speed, followed by deceleration, walking, and standing. Cumulative energy cost was calculated to be equal to the energy cost reported for a live professional tennis match. Total time of the exercise protocol was 108 min and 12 s.
ITF regulations allow a rest break of 90 s after every odd-numbered game, and a rest break of 120 s after every set. Accordingly, the different cooling methods were employed during these rest breaks. Subjects were allowed to drink cold water under all conditions.
The effectiveness of cooling was determined by rectal temperature (Tr), skin temperature (Tsk), HR, thermal sensation (TS) measured on a VAS scale, and rate of perceived exertions (RPE). Tr, HR, and RPE were averaged over the last 15 s of every break. TS was assessed 3 times per break: before the cooling method, after removal of the cooling method, and after completion of the next “game” of the protocol.
Nine healthy, non-heat acclimatized, physically fit males, average age 25 ± 4 yr, performed the exercise protocol on three different days using different cooling methods on each day: ICE method, FAN method, and a control day in which no cooling method was employed. The exercise session was performed in an environmental chamber with a temperature of 36 degrees C and relative humidity of 50%. These conditions were equivalent to the peak heat stress experienced at a recent US Open tennis tournament.
The results of the study revealed that seven of the nine subjects were able to complete the FAN trial, five completed the ICE trial, and only one subject was able to complete the exercise protocol that did not include a cooling method. The authors hypothesized that the FAN cooling method would be superior to the ICE method because evaporation of water is a much more potent mechanism of heat loss than conduction, the primary mechanism of the ICE method. However, there were no discernible differences between the two methods on change in Tr, Tsk, thermal sensation, HR, or RPE. Both methods were significantly superior to the no cooling method in objective temperature measurements and subjective feelings of heat and fatigue. Increase in rectal temperature was less in the FAN and ICE trials compared to control by the first game of the second set, and precooling and postcooling skin temperature was significantly lower in the ICE and FAN trials compared to control by the second set. By the end of the second set, both RPE and HR were significantly higher in the control trials compared to the ICE and FAN trials. Since both the FAN and ICE methods were equally effective, the choice of cooling method should be determined by the athlete’s preference and ease/feasibility of the application.