Aortic bulb-aortic orifice hemodynamics in left ventricle-systemic arterial interaction.

Experiments were conducted in open-chest dogs in which ascending aortic blood flow (Q) was measured with an electromagnetic flow probe, and pressure was measured in the left ventricle (LV) and ascending aorta. The aorta just distal to the flow probe was occluded suddenly, causing the aortic bulb (AB) to be the only part of the arterial system to be in communication with the LV during clamped beats. Pressure and flow data from preocclusion, occlusion, and occlusion-release periods were analyzed to assess AB compliance (CAB) and the longitudinal impedance properties of inertance (LVO) and resistance (RVO) in the AB-aortic orifice region.

Mechanical determinants of transient changes in stroke volume.

To better define beat-to-beat regulation of stroke volume (SV), the several-beat transient response of the left ventricle (LV) to sudden changes in hydraulic loading impedance was studied. Data were collected from eight canine isolated heart-lung preparations with controlled LV loading impedance. At a selected diastolic interval, a sudden increase in hydraulic loading resistance was induced.

Arterial baroreflex control of heart rate in the horse, pig, and calf.

The heart rate (HR) response to stepwise changes in mean arterial pressure (MAP) produced by methoxamine and sodium nitroprusside was studied in conscious horses, pigs, and calves. The respective steady-state arterial baroreflex sensitivities (delta HR/delta MAP expressed as beats min-1 . mm of Hg-1) were -1.

Internal capacitance and resistance allow prediction of right ventricle outflow.

The relationship between right ventricle afterloading pressure (P) and outflow (Q) was studied in three isolated canine right ventricle (RV) preparations. Right atrial pressure was held constant while graded elevations in P were induced with stepwise occlusions of the right and left branches of the pulmonary artery. P and Q signals were collected and analyzed using a digital computer system.