Malignant ventricular arrhythmias (VA) can be life threatening in athletes. Withdrawal from competitive sports is highly recommended and potentially life saving in athletes with documented VA or in those at high risk for sudden cardiac death (2). Conversely, supraventricular tachycardias (SVT), such as atrioventricular nodal reentrant tachycardia (AVNRT), atrioventricular reentrant tachycardia (AVRT), atrial tachycardia (AT), or atrial flutter, are not associated with sudden cardiac death in athletes and can successfully be treated by catheter ablation with low complication rates (3). The same holds true for atrial fibrillation (AF), a common arrhythmia that is associated with high intensity endurance training (3,5,6).
Therefore, the correct diagnosis of an arrhythmia plays a crucial role in sports cardiology and may have profound effect on treatment decisions and implications for the future career of an individual athlete. European and US cardiology task forces have provided international guidelines for the treatment of arrhythmias in athletes (3,7,9).
Symptoms related to cardiac arrhythmias are often nonspecific and arrhythmia episodes can be asymptomatic. ECG recording of the rhythm disturbance is essential for diagnosis, risk stratification, and guidance of the arrhythmia-specific therapy in symptomatic athletes.
Because of the infrequent occurrence of many arrhythmias, 12-lead ECG recordings during arrhythmia are rarely available. Despite numerous options for ambulatory heart rhythm monitoring, the diagnosis of arrhythmias can be difficult, especially in exercise-related arrhythmias (2). Exercise testing can contribute to a diagnosis in some arrhythmias, such as catecholaminergic polymorphic ventricular tachycardia, but cannot reliably induce other arrhythmias, such as adrenergically mediated AF. Therefore, alternative ways of capturing the arrhythmia can be helpful.
Leadless, ambulatory HR monitors with chest strap transmitters have been designed for use in healthy athletes with a baseline sinus rhythm; however, they also have captured exercise-induced arrhythmias. This work describes our experience of this observed utility with three examples of different arrhythmias.
Athletes with palpitations regularly present in our outpatient clinic. Athletes using HR monitors during symptomatic episodes were asked to provide the recordings for analysis.
HR monitors can measure the instantaneous HR. Certain HR monitors store these data and some can additionally provide precise data on RR intervals. Many devices provide additional information about pace, distance, and altitude.
The athlete of the first case description used a HR monitor Polar® RS 800, the athlete of the second case description used an HR monitor Garmin® Forerunner 305, and the athlete of the third case description used Polar® S 625.
On presentation, a full cardiac workup was done in every patient, with history taking, physical examination, ECG recording, and echocardiography. The monitor recordings were analyzed by two cardiologists.
According to international guidelines, all subjects met criteria for an invasive electrophysiological (EP) study (10). All athletes provided written informed consent.
Presentation of Cases
A 32-yr-old cyclist perceived palpitations and decreased exercise capacity while training according to his usual schedule. His HR monitor revealed a fast and irregular HR. Despite decreasing his intensity, his symptoms persisted. Initial presentation to the emergency department revealed AF by 12-lead ECG that resolved spontaneously. His history was remarkable for prior similar episodes of short duration, largely exercise induced. Echocardiography and exercise testing were unremarkable. To maintain sinus rhythm, he was advised to reduce the intensity and duration of his training. In addition, β-blockers and antiarrhythmic drug therapy (flecainide) were prescribed. Despite these measures, arrhythmic episodes persisted and AF ablation was recommended and performed by pulmonary vein isolation. After the ablation, he remained free of palpitations during follow-up after 12 months. No arrhythmia was detected in the Holter monitoring 3, 6, and 12 months after ablation and his HR monitor.
HR, speed, and altitude during the bicycle training are illustrated in Figure 1A. Figure 1B shows RR intervals (=cycle length), depicting several changes between regular and irregular rhythms. The subject’s ECG tracing showing AF at the time of diagnosis is displayed in Figure 1C. Figure 1D shows the exact cycle length during selected episodes of arrhythmias during the training and the suspected rhythm.
A 36-yr-old cross-country skier reported paroxysms of palpitations lasting several seconds up to a few minutes, occurring predominantly shortly after finishing his training and during interruptions of his exercise session. Attempts at capturing it on a resting ECG were unsuccessful. Stress testing on a cycle ergometer until exhaustion at 325 W could not provoke the tachycardia. Echocardiography was unremarkable. The athlete then presented to medical attention with an episode captured by his own HR monitor during cross-country skiing (Fig. 2A). During the EP study, the presence of dual AV-nodal conduction properties was noted: depending on the coupling interval of the following beat, atrioventricular conduction went over the fast or the slow pathway. A typical AVNRT could be induced (Figs. 2C and D). The symptoms of the patient and the almost identical HR of the induced tachycardia made AVNRT as the clinically relevant tachycardia very likely. The patient was successfully treated with slow pathway ablation. No symptomatic arrhythmia recurred during the follow-up of 6 months.
A 28-yr-old triathlete presented with a sporadic exercise-induced tachycardia, occurring once per week and causing discomfort and moderate limitations in exercise capacity. During tachycardia, endurance training could be continued with reduced intensity, but participation in competitions was not pursued. Attempts to capture the tachycardia via Holter monitoring and by exercise testing were unsuccessful. He correlated his symptoms with runs of tachycardia on his HR monitor (170–200 bpm). Figures 3A and B illustrate two different running sessions with intermittent, sudden increases in the athlete’s HR. The athlete refused chronic pharmacologic treatment; therefore, a catheter ablation was planned.
The EP study induced an ectopic atrial tachycardia (Fig. 3C) at 155 beats per minute (bpm), induced only after infusion of high doses of isoproterenol and atropine. P wave morphology with positive P wave in V1 indicated a left atrial origin. Subsequent EP mapping revealed the right inferior pulmonary vein as the origin of the tachycardia. Ablation by selective isolation of the right inferior pulmonary vein was performed successfully. The varying cycle length of the tachycardia during exercise and during the EP study can be explained by varying adrenergic drive. He remained free of symptoms during the follow-up of 9 months.
History taking and 12-lead ECG during rest and during the arrhythmic episode will lead to diagnosis and guide the treatment of most arrhythmias. However, capturing these episodes can be problematic in exercise-related arrhythmias. HR monitors for use in sports are designed to control the intensity of exercise by displaying the HR instantaneously. HR variability (beat-to-beat variation of RR intervals) decreases with increasing intensity (1). Some HR monitoring devices are able to measure this HR variability to steer intensity during exercise and competition (4). Studies have validated R–R data obtained by leadless HR monitors with chest strap transmitters against Holter monitoring (8). Devices capable of measuring HR variability also can therefore be used to analyze the cycle length during arrhythmias (illustrated with case 1).
The leadless HR monitors described above are designed for use in athletes with sinus rhythm, but as we have described here, recordings of arrhythmias with such devices can provide supplemental information concerning the context of occurrence, frequency, and duration of the arrhythmia. Similar to the information from recordings of single-chamber implantable cardioverters-defibrillators, single-chamber pacemakers, or implantable loop recorders, HR monitors for athletic purposes can provide information about the kind of onset and termination of the arrhythmia (sudden vs gradual), about the regularity of the rhythm (regular vs irregular), the HR, and the duration of arrhythmia. However, there is no information about the morphology of the QRS complex and no detection of atrial signals. Therefore, such devices will not precisely distinguish between SVT and VA. For instance, an AVNRT could give the same picture on the HR monitor as a ventricular arrhythmia. However, sinus tachycardia and AF will most likely be correctly diagnosed. Artifacts might nevertheless mimic AF and other arrhythmias. It should also be emphasized that some HR monitors might not be eligible for analysis of arrhythmias. Ideal devices should be able to continuously record data. Measurement and recording of RR intervals seem to be useful features for analysis of arrhythmias. Because data are still sparse, further research is needed to provide general recommendations for analysis of arrhythmias with heart rhythm monitors. Advantages and limitations of different available monitoring devices are shown in Table 1.
Symptomatic arrhythmias in athletes carry critical weight from both a morbidity/quality of life as well as mortality standpoint. Appropriate treatment for these athletes may reverse or minimize the risks associated with their arrhythmias (2,3,7,9). These cases clearly demonstrate the utility of HR monitors with chest strap transmitters in diagnosing exercise-induced arrhythmias and therefore prompting appropriate, timely treatment.
The authors report no conflict of interest.
This work was not supported by funding sources.
The results of the current study do not constitute endorsement by the American College of Sports Medicine.
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