The experimental myocardiopathy's (MC) canine models actually includes canines with Chagas' disease (MCC) or with MC induced by doxorubicin (MCID). Both models are used to compare the normal cardio-respiratory parameters and the relationship to congestive dilated idiopathic MC (CDMC) in humans^1,2. The heart rate variability's (HRV) is and index which could indicate the extent of damage of the autonomic nervous system (ANS) in the MC ^3,4. This study aim was to evaluate the extent of ANS's damages by evaluating the cardio-respiratory parameters and the heart rate variability using pharmacological blockers on experimental myocadiopathy´s canine models⁵. Three groups of canine subjects were evaluated: control (CO) (n=8); with Chagas's disease in undetermined stages (n=9) and with MCID (n=5) subjects. Each one received at random intravenously 0.04 mg/kg of atropine and 0.06 mg/kg of propranolol. The dogs were supervised before and at intervals of 5, 10, 20, 30 and 60 minutes after application of the pharmaceuticals. The cardio-respiratory parameters observed were: heart rate, respiratory frequency, arterial pulse, arterial pressure (diastolic, systolic and media) and rhythm; on the electrocardiogram (ECG): PR, QT, and QRS's duration, P and R's waves amplitudes, ST and T wave configuration, rhythm and HRV. The conclusion was that the HRV growth down in canines with MCID by the activation of the SNAS's tone⁶ and that the MCC's HRV was similarly the CO by the compensation of the simpato-vagal balance presents in the Chagas' undeterminated stage^7,8,9.

References

1.  Andrade, Z. A .et al. The indeterminate phase of Chagas'disease: ultrastructural characterization of cardiac changes in the canine model. American Journal of Tropical Medicine, v. 57, n. 3, p. 328-336, 1997.

2.  Malliani, A. Principles of cardiovascular neural regulation in health and disease. 1 ed. Norwell, Massachusetts, Kluwer Academic Publishers, 2000, 222p.

3.  Malik, M., Camm, A. J. Heart rate variability and clinical cardiology. British Heart Journal, v. 71, p. 3-6, 1994.

4.  Stys, A.; Stys, T. Current Clinical Applications of Heart Rate Variability. Clinical Cardiology, v. 21, p. 719-24, 1998

5.  Elghozi, J.; et al. Effects of drugs on autonomic control of short-term heart rate variability. Autonomic Neuroscience: Basic and Clinical, v. 90, p. 116-121, 2001.

6.  Bristow, M. R.; et al. Acute and chronic cardiovascular effects of doxorubicin in the dog: the cardiovascular pharmacology of drug-induced histamine release. Journal of Cardiovascular Pharmacology,