Atrial coronary hyperemia and ischemia in response to variations in atrial pressure in dogs

Abstract

We altered the mechanical activity of the atrial myocardium in open-chest dogs and measured changes in coronary blood flow distribution, using the radioactive microsphere technique. When left and right atrial pressures were decreased to 2 mm Hg by hypovolemia, atrial coronary blood flow fell to values nearly 50% below baseline. Acute left atrial hypertension was induced by creating mitral valvular incompetence. Progressive incresses in left atrial pressure from 8 to 12 to 20 mm Hg caused increases in left atrial coronary blood flow from 47 to 54 to 75 ml/100 gm × min (mean values). Severe left atrial hypertension (32 mm Hg) caused a fall in left atrial blood flow to 30 ml/100 gm × min. The P wave in lead II of the ECG widened by a mean value of 18 msec, suggesting ischemic impairment of left atrial depolarization.