Measurement of Heart Dimensions in Anesthetized Dogs

The measurement of the heart dimensions allows to localize the effect of a drag on the activity of the heart. An ultrasonic technique is used for continuous measurement of left ventricular dimensions. Compounds are tested with potential anti-anginal activity due to the reduction of left ventricular diameter. The test is used to evaluate the influence of drugs on left ventricular external and internal diameter in anesthetized dogs. 

Male or female Beagle or Labrador-Harrier dogs weighing 15-25 kg are used for the test. The dog is anesthetized by intravenous injection of 35M0 mg/kg pentobarbital sodium followed by subcutaneous injection of 2 mg/kg morphine. Respiration is maintained through a tracheal tube with N2O/O2 (3 1) using a positive pressure respirator. 

Ultrasonic transducers are constructed and implanted as described by Stinson et al. (1974). 

To measure left ventricular external diameter (LVED), two ultrasonic transducers are fixed to the left ventricular wall. One crystal is sutured to the posterior wall within the rectangular area formed by the left circumflex coronary artery and the left posterior descending artery. The other one is placed near the first diagonal branch of the left anterior descending coronary artery. Exact positioning is assured with an oscilloscope. 

To measure left ventricular internal diameter (LVID), the transducers are placed in the same anatomical area as for the epicardial crystals. However, they are pushed through the wall of the left ventricle through stab wound incisions. The crystals are positioned across the greatest transverse diameter of the left ventricle, one on the anterior and the other on the posterior endocardial wall. 

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