LV pressure-volume area and oxygen consumption: Evaluation in intact dog by fast CT

The relationship between left ventricular (LV) myocardial oxygen consumption (MV̇O₂) and LV systolic pressure-volume area (PVA) was investigated in anesthetized closed-chest dogs with intact reflexes and subsequently with β-adrenergic blockade, with or without simultaneous muscarinic blockade. LV chamber volumes were measured using a fast computerized tomography (CT) scanner (dynamic spatial reconstructor, DSR) at 33-ms intervals. Myocardial blood flow was measured from the DSR scans of aortic root angiograms. With intact reflexes, LV MV̇O₂ (Y) related to PVA (X) value as Y = (4.28 ± 1.81)X + (1.94 ± 6.0) (n = 24) (mJ·g^-1·cycle^-1). With β-adrenergic blockade, LV MV̇O₂ (Y) related to PVA (X) value as Y = (4.24 ± 1.03) X - (6.43 ± 6.5), (n = 9) (mJ·g^-1·cycle^-1). With β-adrenergic and muscarinic blockade, LV MV̇O₂ (Y) related to PVA (X) value as Y = (2.84 ± 1.72)X + (3.51 ± 5.15), (n = 13) (mJ·g^-1·cycle^-1). The slopes of these regressions are higher than the slopes demonstrated by others in isolated ventricles but very similar to those demonstrated in open-chest dogs.