Negative diastolic pressure in the intact canine right ventricle. Evidence of diastolic suction.

To determine whether the canine right ventricle (RV) can develop a negative diastolic pressure indicative of suction, RV pressure was measured in 15 dogs, with catheter-tip micromanometers. Six dogs were studied only with the chest closed. In these dogs, intrapleural pressure was measured medially (near the heart) in four and laterally in two. In nine dogs, RV pressure was evaluated with the chest closed and after the chest had been opened. In all dogs, with the chest closed, minimal RV diastolic pressure during expiration was negative, -4.8 +/- 0.3 mm Hg. The lowest diastolic pressures occurred during early diastole. Intrapleural pressure during expiration was never this low. Intrapleural pressure measured medially in four dogs was positive during expiration (1.0 +/- 0.6 mm Hg). In the two dogs which it was measured in the lateral pleural space, it was somewhat negative during expiration (-2.5 and -1.3 mm Hg, respectively). After the chest had been opened (nine dogs) minimal RV pressure during early diastole was negative in six dogs and positive in three (range: -1.8 to 0.8 mm Hg). These results indicate that the negative RV diastolic pressure during expiration did not result from a negative intrathoracic pressure. It appears that the RV during early diastole can create a sucking effect which may contribute to the filling process.