Christian Alcaraz Frederiksen

OBJECTIVE: Right ventricular (RV) failure due to chronic pressure overload is a main determinant of outcome in congenital heart disease. Medical management is challenging because not only contractility but also the interventricular relationship are important for increasing cardiac output. This study evaluated the effect of milrinone alone and in combination with epinephrine or dopamine on haemodynamics, ventricular performance and the interventricular relationship.

DESIGN: RV failure was induced in 21 Danish landrace pigs by pulmonary artery banding. After ten weeks, animals were re-examined using biventricular pressure-volume conductance catheters.

RESULTS: The maximum pressure in the RV increased by 113% (p<0.0001) and end-diastolic volume by 43%, (p<0.002), while left ventricular pressure simultaneously decreased (p=0.006). Concomitantly, mean arterial pressure (MAP) (-16%, p=0.01), cardiac index (CI) (-23%, p<0.0001) and mixed venous oxygen saturation (SvO2) (-40%, p<0.0001) decreased. Milrinone increased CI (11%, p=0.008) and heart rate (HR) (21%, p<0.0001). Stroke volume index (SVI) decreased (7%, p=0.03), although RV contractility was improved. The addition of either epinephrine or dopamine further increased CI and HR in a dose-dependent manner but without any significant differences between the two interventions. A more pronounced increase in biventricular contractility was observed in the dopamine-treated animals. Left ventricular volume was reduced in both the dopamine and epinephrine groups with increasing doses.

CONCLUSIONS: In the failing pressure overloaded RV, milrinone improved CI and increased contractility. Albeit additional dose-dependent effects of both epinephrine and dopamine on CI and contractility, neither of the interventions improved SVI due to reduced filling of the LV.