DOES PHYSIOLOGIC CARDIAC REMODELING IN ENDURANCE ATHLETES ALTER REPOLARIZATION OR QT DYNAMICS?
CCC ePoster Library. Osman W. 10/26/19; 280509; 274
Wesseem Osman
Wesseem Osman
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Abstract
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BACKGROUND: Increases in QT and QTc duration, and their alterations with changes in heart rate, are associated with dysrhythmias and increased sudden death rates in population studies. Long standing endurance sport is associated with reduced cardiac mortality. Endurance athletes are known to develop physiologic LV remodeling concomitant with increases in LV mass, which may be associated with QT prolongation. However, QT dynamics in middle-aged athletes has not been studied extensively. We sought to compare the QT interval at rest and during exercise in healthy middle-aged adults with and without a history of long-standing endurance exercise.

METHODS AND RESULTS: Healthy participants on no medications, between 45-65 years old (>10 years of regular physical activity participation) were recruited, and underwent physical examination. Eligible participants, including 86 endurance athletes (EA) and 24 recreationally-active (RA) adults, had a resting baseline 12-lead ECG and a standardized graded exercise testing with a 12-lead ECG taken every 1-2 minutes during exercise until exhaustion. QT intervals were measured as the longest QT in anterior precordial lead or lead 2 by two investigators and discrepancies resolved by consensus; QT intervals were corrected for rate using Bazett's formula (QTc=QT/RR in sec). Seventy-five participants also had a resting cardiac magnetic resonance to evaluate cardiac structure and physiological remodeling related to exercise. Participant demographics and ECG characteristics are summarized in Table 1. The higher cardiorespiratory fitness (VO2max) and left-ventricular mass reflected normal physiological adaptation to endurance exercise training. While mean resting QT interval was longer in EA vs. RA, there was no difference when QT interval was corrected for heart rate (QTc). The QT and QTc slopes (linear relationship of QT vs. RR and QTc vs. RR during exercise) were not different between EA and RA.

CONCLUSION: Among long-standing middle-aged athletes with normal physiologic remodeling, there is no difference in QT intervals in EA vs. RA when corrected for their lower resting heart rate. Despite physiologic LV remodelling, chronic endurance exercise training is associated with normal repolarization at rest and during exercise among middle-aged endurance athletes.
BACKGROUND: Increases in QT and QTc duration, and their alterations with changes in heart rate, are associated with dysrhythmias and increased sudden death rates in population studies. Long standing endurance sport is associated with reduced cardiac mortality. Endurance athletes are known to develop physiologic LV remodeling concomitant with increases in LV mass, which may be associated with QT prolongation. However, QT dynamics in middle-aged athletes has not been studied extensively. We sought to compare the QT interval at rest and during exercise in healthy middle-aged adults with and without a history of long-standing endurance exercise.

METHODS AND RESULTS: Healthy participants on no medications, between 45-65 years old (>10 years of regular physical activity participation) were recruited, and underwent physical examination. Eligible participants, including 86 endurance athletes (EA) and 24 recreationally-active (RA) adults, had a resting baseline 12-lead ECG and a standardized graded exercise testing with a 12-lead ECG taken every 1-2 minutes during exercise until exhaustion. QT intervals were measured as the longest QT in anterior precordial lead or lead 2 by two investigators and discrepancies resolved by consensus; QT intervals were corrected for rate using Bazett's formula (QTc=QT/RR in sec). Seventy-five participants also had a resting cardiac magnetic resonance to evaluate cardiac structure and physiological remodeling related to exercise. Participant demographics and ECG characteristics are summarized in Table 1. The higher cardiorespiratory fitness (VO2max) and left-ventricular mass reflected normal physiological adaptation to endurance exercise training. While mean resting QT interval was longer in EA vs. RA, there was no difference when QT interval was corrected for heart rate (QTc). The QT and QTc slopes (linear relationship of QT vs. RR and QTc vs. RR during exercise) were not different between EA and RA.

CONCLUSION: Among long-standing middle-aged athletes with normal physiologic remodeling, there is no difference in QT intervals in EA vs. RA when corrected for their lower resting heart rate. Despite physiologic LV remodelling, chronic endurance exercise training is associated with normal repolarization at rest and during exercise among middle-aged endurance athletes.
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