Copyright © 1994 by the European Society of Cardiology.
© 1994 The European Society of Cardiology
Arrhythmias and ST segment deviation during prolonged exhaustive exercise (ski marathon) in healthy middle-aged men
Lääkäriasema Koe Oy, Helsinki; Central Military Hospital, Helsinki; and First Department of Medicine, Helsinki University Central Hospital Helsinki, Finland
Received 17 August 1992; revised 24 August 1993; .
Correspondence. Dr O. J. Luurila, Lääkänasema Koe Oy, Laboratory of Clinical Physiology, 00100 Helsinki, Finland
Abstract
To evaluate the occurrence of arrhythmias and silent ischaemia during a prolonged exhaustive exercise in cold climate conditions, we monitored 37 healthy middle-aged men (age 40–56 years) who were randomly selected from participants of a ski marathon. Completing the 75–90 km race took 7–12 h. The highest and lowest mean hourly heart rates during skiing were 150 ±9 (mean ± SD) and 138 ± 11 beats. Min1. The maximum heart rate was 161 ±9 beats. min1, and occurred in most skiers during the first hour. Ventricular premature complexes (VPCs) were present in 33 of 37 men (89%) with a median frequency of five beats during skiing (range 0–425). Complex forms occurred in eight men (22%), and atrial ectopics appeared in 33 of 35 participants (94%). The frequency of the arrhythmias did not increase over the skiing period At control monitoring during a representative period the highest mean hourly heart rate was 74 ± 12 beats. min1 and VPCs were seen in 21 men (57%) at a median frequency of one beat during the control period (range 0–338) and complex forms occurred in three men (8%).
Three men had asymptomatic ST segment depression of 0·2–0·3 m V lasting 2–10 min during the first hour of skiing. One of them had marginal ST segment depression (0·1 m V) at exercise electrocardiography, but all had normal results at exercise thallium scintigraphy and echocardiography.
Thus, arrhythmias were significantly (P<0001) increased in middle-aged men during exhaustive prolonged exercise as compared to those observed during a similar period of time of normal daily life. Transient ST segment depression was found in 8% of skiers at the beginning of the race, although they had not demonstrated coronary artery disease. This, however may indicate an increased risk during the initial part of the race
It is obvious that the risk of cardiac events is increased at the start of long lasting exhaustive exercise before adaptation to stress, but prolongation of exercise even in cold climates does not increase the risk of arrhythmia or other cardiac complications. However, cold climate conditions and symptoms of respiratory infection may increase the risk of cardiac arrhythmias.
Key Words: Exercise • cross-country skiing • ambulatory electrocardiography • cardiac arrhythmias • middle-aged men