Investigation of cardiovascular effects of long-term endurance exercise training in rabbits and dogs
█ Original article
Polyák Alexandra1, Kui Péter1, Morvay Nikolett2, Leprán István2, Ágoston Gergely3, Varga Albert3, Baczkó István2, Farkas András2, Papp Gyula2, Varró András2, Farkas Attila1
1SZTE, Általános Orvostudományi Kar, II. sz. Belgyógyászati Klinika és Kardiológiai Központ, Szeged
2SZTE, Általános Orvostudományi Kar, Farmakológiai és Farmakoterápiai Intézet, Szeged
2SZTE, Általános Orvostudományi Kar, Családorvosi Intézet és Rendelő, Szeged
Aims: Several tragic sudden deaths involving young athletes have been reported in the recent years. In some of cases the cause remains obscure. The effect of long-term intensive exercise on cardiac morphology and electrical activity was assessed in animal models.
Methods: Rabbits (1. series, n=7) and mongrel dogs (2. series, n=2) were randomized into “sedentary”, “exercised” and “doping” (2nd set of experiment) groups that were treated with testosterone-undecanoate periodically. ’Exercised’ and ’doping’ groups were trained during a 16-week long treadmill-running protocol. Echocardiography and resting ECG recordings were performed. In dogs, proarrhythmic sensitivity and the autonomic alterations by a pharmacological parasympathetic inhibition were tested.
Results: At 16. week the left ventricular end-diastolic diameter (LVEDD) showed significant increase in the ’exercised’ rabbits and an increasing tendency in the ’exercised’ dogs (rabbit: 17.5±0.6 vs. 13.6±0.7 mm; dog: 27.2±0.2 vs. 24.0±3.0 mm, p<0.05). The length and the variability parameters of the RR intervals were greater in the trained groups. Dofetilide tended to increase the QTc in greater extent, atropine treatment resulted in moderate heart frequency increase both in “exercised” and “doping” groups compared to the “sedentary” group.
Conclusions: Our echocardiographic results correspond to the human endurance trained athlete’s heart morphology. The lengthened RR intervals, the increased heart rate variability are the signs of the increased parasympathetic tone and are characteristics of the exercise-induced autonomic changes. Repolarization changes may indicate the sensibility of the hearts to arrhythmia, however further investigations with higher ‘n’ numbers are warranted.