Coronary blood flow measurements with left atrial injection of microspheres in conscious rats

Since left atrial (LA) injection of microspheres has been shown to give more precise coronary blood flow (CBF) determinations, and also since studies in a conscious state have obvious advantages, we have developed a technique of chronic LA catheterisation for these purposes in rats. Through a thoracotomy in the third left intercostal space, the LA appendage was cannulated and a catheter (PE-10 tubing) advanced into the left atrium. The catheter itself was passed through the chest and exteriorised at the back of the neck. Following recovery over 24 to 48 h, flow studies with microspheres could be performed for 3 to 8 days. One-hundred and twenty procedures performed over a 4 month period were analysed. Left atrial catheterisation could be performed in approximately 45 min with no bleeding in 79% of cases and only minimal or moderate bleeding in the rest (13% and 4%, respectively); respiratory complications were rare (less than 1%). The rats recovered rapidly, and all catheters remained patent for the duration of the preparation. Infections developed in 5% and the total mortality rate was 7%; a complete haemodynamic study could be obtained in 130/120 rats (86%). Small renal infarcts were found in 25% of the rats, but neither the infarcts nor the intraoperative blood loss had any significant effect on haemodynamic indices and flow measurements performed 3 to 8 days after atrial catheterisation. Coronary blood flow values in 33 normal rats were within the range of values reported in the literature. These results demonstrate that chronic LA catheterisation is possible in rats with no major difficulties and will allow the precise determination of coronary blood flow with microspheres in conscious animals.