[The Flack test: a test exploring the sinus function in athletes. Apropos of 351 tests]

Area of Science:

• Cardiology
• Sports Medicine
• Physiology

Background:

• Athletes often exhibit unique electrocardiographic (ECG) findings due to physiological adaptations.
• Distinguishing between normal athletic variations and pathological conditions is crucial for athlete health.
• The Flack's test is used to assess sinus node function and autonomic regulation.

Purpose of the Study:

• To evaluate the diagnostic utility of the standardized Flack's test in moderately trained athletes.
• To identify the prevalence and types of cardiac arrhythmias and conduction abnormalities during the test.
• To assess the impact of the Flack's test on pre-existing cardiac findings.

Main Methods:

• A standardized Flack's test with continuous electrocardiographic (ECG) recording was performed.
• 351 moderately trained athletes (317 men, 34 women; mean age 23.7 years) participated.
• ECG findings were compared with previous resting ECGs.

Main Results:

• The Flack's test yielded normal results in 88.3% of athletes.
• Cardiac abnormalities were noted in 8.3% of subjects (29/351), with 56 distinct events observed.
• Sinus dysfunction (bradycardia, sinoatrial block, sinus arrest) was the most common abnormality (44.6%), followed by conduction disorders (8.9%) and extrasystoles (16.1%).
• Tachycardia (>100 bpm) occurred in 3.4% of subjects.
• In 8 subjects, the Flack's test led to the disappearance of resting "athlete's heart" type conduction or excitability disorders.

Conclusions:

• The Flack's test is a valuable tool for detecting cardiac abnormalities in athletes.
• Sinus node dysfunction is a significant finding during the Flack's test in athletes.
• The test may reveal transient resolution of certain cardiac findings, highlighting the dynamic nature of athletic cardiovascular adaptations.