Abstract
It has been assumed that ventricular standstill induces left ventricular dilation because filling continues without emptying. Left and right ventricular diameters by echocardiography and pressures were monitored continuously in 21 intact dogs before and during ventricular standstill induced by coronary embolization (E), potassium infusion (K+), or calcium infusion (Ca++) in 7 dogs respectively. At the onset of ventricular standstill, left ventricular pressure rose from an end-diastolic of 4.6±2.2 to 16.6±3.6 mmHg after E, 5.4±3.2 to 18.0±3.3 mmHg after K+, and 6.3±2.1 to 16.6±3.6 mmHg after Ca++ (all p<0.001). Left ventricular dimension rose from and end-diastolic of 44.6±8.0 to 49.4±8.5 mm after E, 43.1±5.1 to 46.3±4.6 mm after K+ but fell from 40.6±5.1 to 33.9±3.4 mm after Ca++ before ventricular standstill occurred. During the first 5 min of ventricular standstill, left ventricular pressure gradually fell from 16.6±3.6 to 5.4±1.1 mmHg (E), 18.0±3.3 to 5.9±2.0 (K+), 16.6±3.6 to 5.5±1.7 (Ca++) (all p<0.001) while left ventricular diameter gradually fell to 40.7±7.0 mm (E), 35.0±5.1 (K+), 29.6±3.6 (Ca++) (all p<0.001). Right ventricular pressure initially rose from 2.9±1.6 mmHg to 12.1±3.1 (E), from 2.7±1.3 to 12.0±2.0 (K+) from 2.7±1.0 to 12.6±2.6 (Ca++ within 15 sec, then gradually fell to 6.6±1.1 (E), 6.1±1.9 (K+), and 7.9±1.8 (Ca++) in 5 min whereas right ventricular diameter rose progressively from 4.4±3.0 mm to 21.0±1.7 (E), 4.7±2.6 to 20.3±1.3 (K+), 4.2±1.1 to 18.1±2.8 (Ca++) in 60 sec (all p<0.001). Thus ventricular standstill is characterized by early left ventricular emptying and inhibited left ventricular filling despite continued right ventricular filling, a finding that might reflect the different intrinsic properties of the two ventricles.
