Cardio-Respiratory Parameters and Heart Rate Variability Clinical Evaluation Using Pharmacological Blockers on Experimental Myocardiopathy's Canine Models
Veterinary School of Anhembi Morumbi University, Rua São João 775, Cotia, SP, Brazil
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 humans1,2. 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 stage7,8,9.
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,