Objective: To assess the influence of age on pulmonary hemodynamics and hemorheological properties in healthy dogs.
Animals: 14 healthy Beagles.
Procedures: Dogs were placed in 2 age groups as follows: young dogs (<or= 5 years old; n = 8) and old dogs (>or= 8 years old; 6). Hematologic characteristics, plasma total protein and fibrinogen concentrations, and blood viscosity were measured. Systolic time intervals of pulmonary blood flow were recorded by pulsed-wave Doppler echocardiography. Early (E') and late (A') diastolic myocardial velocities, isovolumic contraction velocity, and systolic myocardial velocity of the free tricuspid annulus were recorded by pulsed-wave tissue Doppler imaging (TDI). Dogs were anesthetized and pulmonary arterial pressures (PAP) and cardiac output were recorded with a pediatric thermodilution Swan-Ganz catheter.
Results: Hemorheological measurements were not different between the 2 groups. Systolic, mean, and diastolic PAP were higher in old dogs, compared with values in young dogs; this difference was attributed to a high pulmonary vascular resistance and low arterial compliance in old dogs. Systolic time intervals of pulmonary blood flow stayed unchanged. The A' wave of the free tricuspid annulus was increased in old, compared with that young dogs, and the E':A' ratio was decreased. Pulmonary vascular resistance was inversely correlated with compliance.
Conclusions and clinical relevance: The age of dogs should be taken into account when interpreting pulmonary hemodynamic results and TDI variables of right ventricular diastolic function.