Progression of Wolff–Parkinson–White pattern 12-lead electrocardiogram changes in an asymptomatic athlete

CLINICAL PRESENTATION A male soccer player had been screened by sports physicians for routine annual preseason medical clearance since he was 14 years old. He had no family history of syncope, heart disease or sudden cardiac death (SCD), and no personal history of dizziness, syncope, palpitations, breathlessness or chest pain. He attended soccer training regularly and was able to perform to expectations. Physical examination was normal with blood pressure of 115/81 mmHg, heart rate (HR) measuring 58 beats per minute (bpm) and normal heart sounds with no murmur. Figures 1–4 show the patient’s serial 12-lead electrocardiograms (ECGs) performed during his annual routine medical clearance. What do the ECGs show?Figure 1: 12-lead electrocardiogram in 2016 (normal).Figure 2: 12-lead electrocardiogram in 2017 (normal).Figure 3: 12-lead electrocardiogram (ECG) in 2018. Features of Wolff–Parkinson–White pattern ECG: short PR interval (<120 ms), delta wave and QRS prolongation (>110 ms).Figure 4: 12-lead electrocardiogram (ECG) in 2018. Features of Wolff–Parkinson–White pattern ECG (more pronounced than Figure 3): short PR interval (<120 ms), delta wave and QRS prolongation (>110 ms).ECG INTERPRETATION Initial 12-lead ECGs performed at age 14 years (Figure 1) and 15 years (Figure 2) were normal, while those taken at age 16 years (Figure 3) and 17 years (Figure 4) show a Wolff–Parkinson–White (WPW) pattern. The serial ECGs over 4 years demonstrate progression of ECG changes, with HR ranging from 55–62 bpm. However, no ST segment or T wave discordant changes were seen. CLINICAL COURSE The patient was referred for cardiology opinion after his latest presentation at 17 years of age in view of the WPW pattern ECG. Echocardiogram showed normal cardiac structure and function. Exercise stress testing (EST) did not elicit any arrhythmias, but showed persistent WPW pattern throughout exercise, peak stress and recovery. He completed in 18 min 2 s, reaching stage 6 of the Bruce protocol (HR 171 bpm, metabolic equivalent 16.9). An electrophysiology study (EPS) was recommended in view of his sport, but he declined. Without an EPS, the sports physician and cardiologist opined that he could not be certified fit for further participation in elite youth soccer. He and his family were strongly advised on the potential risks of continued participation in moderate- to high-intensity physical activity. He was given an appointment for periodic review of his physical status and ECG. DISCUSSION Wolff–Parkinson–White syndrome refers to tachycardia in the presence of a congenital accessory pathway (AP), resulting in ventricular pre-excitation; the prevalence of WPW syndrome is 0.01%–0.3%.[1] It results in characteristic ECG changes termed as WPW pattern ECG. Both symptomatic and asymptomatic patients with WPW pattern ECG are at risk of developing life-threatening arrhythmias. Symptomatic patients are termed to have WPW syndrome. A large proportion of patients with WPW pattern ECGs are asymptomatic; hence, many individuals are undiagnosed and risk missing out on treatment. The concern regarding WPW syndrome is its association with SCD, especially during exercise,[1] with an estimated lifetime risk of 0.1%.[2] Risk factors include male gender, young age, history of atrial fibrillation (AF), previous syncope, familial WPW syndrome and congenital heart disease.[1] Wolff–Parkinson–White pattern ECG is of particular concern in athletes competing in moderate- to high-intensity sports. In a long-term registry of SCDs in athletes, WPW syndrome is listed as a cause of SCD in approximately 1% of the athletes, although the actual prevalence may be higher; WPW syndrome may account for a significant portion of autopsy-negative SCDs due to challenges in making a postmortem diagnosis in the absence of previous ECGs.[1] Exercise does not alter the AP, but may enhance conduction through it. Although the mechanism is unclear, most of the instances of SCD in WPW syndrome appear to occur during exercise.[1] There is also a higher incidence of AF in trained athletes than in the general population. However, it is unknown whether exercise has a consistent effect of promoting supraventricular tachycardia into AF. Intermittent WPW pattern on ECG is a known entity, and in some individuals, the WPW features may disappear over time;[3] this phenomenon has been reported in 10%–40% of individuals in several large cohort studies.[3,4] Intermittent pre-excitation may be related to the length of the AP effective refractory period (ERP), the location of the AP or variations in autonomic tone.[5] Some studies have shown that individuals with intermittent WPW pattern ECGs are at risk of SCD, especially in the paediatric population.[3] In our patient, the appearance of WPW pattern ECG after initial normal screening ECGs could be a result of intermittent pre-excitation or late-onset WPW pattern ECG due to developmental maturation of the AP with age. As the heart develops and grows throughout childhood and adolescence, conduction pathways, including APs, continue to develop and mature, and APs may express only at a later age.[6] As our patient’s initial screening ECGs were done during his adolescent years, the delayed presentation could be attributed to the AP not having fully matured during his initial visits for preparticipation screening. There was no ambulatory ECG monitoring (Holter study) performed, as the patient remained asymptomatic; hence, it is not possible to definitively exclude intermittent pre-excitation. However, several features make intermittent pre-excitation less likely in this case. Vagal tone in athletes increases in proportion to fitness. Pre-excitation can become more apparent with increased vagal tone, but increased vagal tone is usually accompanied by increased bradycardia. Our patient’s screening ECGs through the years showed no change in HR (55–62 bpm throughout), regardless of presence of WPW changes, although it can be argued that the degree of pre-excitation did increase at lower HRs. The ECG in Figure 4 shows more pre-excitation (shorter PR and wider QRS interval) at a lower HR of 55 bpm compared to the ECG in Figure 3 at an HR of 57 bpm, and no pre-excitation is seen at higher HR as shown in Figure 1 (HR 62 bpm) and Figure 2 (HR 59 bpm). Also, individuals with intermittent pre-excitation often have symptoms such as palpitations when pre-excitation occurs, while our patient was asymptomatic throughout, even when his ECG showed pre-excitation. In addition, during exercise, sympathetic activity increases and cardiac vagal tone decreases and conduction through the AP should decrease with more conduction through the atrioventricular node (AVN), resulting in disappearance of pre-excitation. In our patient, WPW pattern ECG persisted throughout the EST even when he reached stage 6 of the Bruce protocol. The persistence of WPW pattern ECG throughout the EST suggests that the patient has a high-risk AP and an EPS is indicated for further risk stratification and to guide treatment regardless of whether he has intermittent or continuous pre-excitation. With increasing sympathetic activity as the intensity of exercise increases throughout the EST, the effective ERPs of both the AP and AVN are shortened. The persistence of the delta wave up to stage 6 suggests that shortening of the AP ERP is more likely than the AVN ERP, and hence, conduction occurs through the AP at very high HRs. This can be life-threatening if the patient develops arrythmias at high HRs such as AF or ventricular fibrillation (VF). Intermittent pre-excitation in WPW syndrome has historically been thought to confer a lower risk of SCD than continuous pre-excitation. APs in intermittent WPW syndrome have been thought to have longer ERP and, therefore, a lower risk for development of sustained pre-excited AF or VF.[5,7] However, several recent studies, particularly those in paediatric patients, have suggested that the intermittent nature of an AP may not rule out potentially high-risk conduction characteristics.[3,8] All asymptomatic individuals with WPW pattern ECGs should undergo noninvasive risk stratification, involving 12-lead ECG, Holter study, echocardiogram and EST. Holter study and EST can identify low-risk pathways. Those with loss of pre-excitation at physiological HRs generally have slower conducting APs and may be considered lower risk.[1] During EST, abrupt and complete loss of pre-excitation confirms a long anterograde pathway refractory period and a low-risk profile.[1] Echocardiogram can rule out structural abnormalities such as Ebstein anomaly and hypertrophic cardiomyopathy, which are associated with WPW syndrome.[1] Further, invasive EPS is performed as indicated.[2] Guidelines published by the European Society for Cardiology (ESC) in 2019 and the American College of Cardiology/American Heart Association/Heart Rhythm Society (ACC/AHA/HRS) concur that in asymptomatic WPW syndrome, the risks of SCD or adverse events should be weighed against the risks of invasive testing and ablation. The decision to proceed with invasive testing is based on noninvasive test findings, risk stratification based on demographic characteristics, and clinical expertise available for invasive testing and ablation. It is reasonable for asymptomatic patients to be observed, as most observational cohort studies suggest that the majority of adults without ablation have a benign course. However, it is also reasonable to perform invasive testing for risk stratification of patients.[9,10] The clinical priority is identifying APs at increased risk of arrhythmic events, and EPS are generally associated with low risk of complications.[11] If noninvasive testing shows a low-risk pathway, it is reasonable not to perform invasive testing. However, in elite athletes, as well as individuals in high-risk occupations (e.g. pilots) whose AP would preclude employment, invasive testing may be required.[9,10] Special consideration should be given to the paediatric population, where the risk of ventricular fibrillation or SCD related to WPW syndrome is 1.3%–1.6% and is highest in the first two decades of life.[10,11] The 36th Bethesda Conference by the ACC recommends risk stratification with invasive EPS for asymptomatic younger athletes who are engaged in moderate- to high-intensity competitive sports, and this is also reflected in the ACC/AHA/HRS guidelines in 2015.[10,12] The ESC recommends that all athletes with WPW pattern ECGs should undergo comprehensive EPS, regardless of sport and even if a low-risk pathway is identified on noninvasive testing, as training in low-intensity sports may involve moderate- to high-intensity exercise.[9] There is also consensus regarding treatment of symptomatic athletes. Medical therapy includes antiarrhythmic drugs, which are not recommended due to potential adverse effects, including proarrhythmic risk and their effect on athletic performance.[1,12] Transcatheter ablation, which offers a potentially definitive cure, is recommended. Ablation is also recommended in individuals with high-risk pathways.[1,9,10] After ablation, if an athlete remains asymptomatic with normal atrioventricular conduction on ECG, he may return to sport at least 1 month after ablation if there are no recurrences, with regular follow-up.[1,9] Asymptomatic athletes with low-risk pathways identified are not required to undergo ablation therapy, but should continue to undergo monitoring.[1,9,10] Although there is consensus that preparticipation cardiovascular screening for elite and competitive athletes is justifiable,[13,14] there is much controversy regarding the inclusion of routine 12-lead ECGs. The AHA and American Medical Society of Sports Medicine (AMSSM) recommend universal screening of young athletes using the 14-point AHA preparticipation cardiovascular checklist, with preparticipation medical clearance consisting of history taking and physical examination. It acknowledges that screening ECGs not only enhance detection of cardiac disorders at potential risk of SCD or arrythmias, but also increase potential false-positive results and associated downstream consequences. The latest position statement by the AMSSM in 2016 does not provide strict recommendations, but advises physicians to consider differential risks of the athlete, needs of the athlete population, experience and available cardiology infrastructure, and risks and benefits of early detection in reducing cardiovascular morbidity and mortality.[14] The optimal age and frequency for cardiovascular screening in athletes are uncertain, but screening generally starts at ages 12–14 years and is repeated every 1–3 years.[14] The arguments for ECG screening in young athletes include the high negative predictive value, and although rare, the consequences of SCD in young athletes are devastating if WPW syndrome is not detected. One study in Italy found that routine ECGs reduced the annual incidence of SCD by 90%.[13] In another study comparing screening with the AHA 14-point evaluation to 12-lead ECGs, the sensitivity (18.8%), specificity (68.0%) and positive predictive value (0.3%) of the AHA 14-point evaluation were substantially lower than the sensitivity (87.5%), specificity (97.5%) and positive predictive value (13.6%) of ECGs.[15] Finally, there is no consensus regarding the frequency of follow-up screening ECGs for preparticipation clearance. CONCLUSION Wolff–Parkinson–White syndrome occurs due to the presence of a congenital AP. In the present case, initial ECG was likely unremarkable as there was no conduction through the AP. This case highlights an entity of individuals with initial normal ECGs who later develop WPW pattern changes, with the possible differential of intermittent pre-excitation. Without serial screening ECGs, these individuals may miss out on the opportunity for work-up and treatment. The role of screening ECGs is still highly debated, with differing opinions on its inclusion in preparticipation screening. This case report may support serial screening ECGs, especially in adolescent and youth athletes, particularly as intermittent WPW syndrome in the paediatric population does not exclude a high-risk AP. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest. SMC CATEGORY 3B CME PROGRAMME Online Quiz: https://www.sma.org.sg/cme-programme Deadline for submission: 6 pm, 09 August 2023