Left-ventricular unloading with a new pulsatile assist device: The HIA-VAD system and its influence on myocardial stunning

To assess the mechanical unloading properties of a new pneumatic cardiac assist device (60 ml Medos(R) HIA-VAD(R)) and its possible influence on recovery from myocardial stunning we performed a study in 12 anaesthetized sheep. After left thoracotomy measuring transducers were placed and the assist device connected between the left-atrial appendage and the descending thoracic aorta. Global hemodynamics were measured before and after unloading was performed. Myocardial stunning was induced by transient occlusion of a coronary artery for 15 minutes and regional myocardial wall thickening was measured. A group without unloading served as controls (group I, n=4). In a second group unloading was performed during the last ten minutes of ischemia (group II, n=4) and in a third group unloading was performed for 30 minutes starting after ten minutes of reperfusion (group III, n=4). After starting the Medos(R) HIA-VAD(R), significant unloading could be demonstrated: left-ventricular dP/dt(max) decreased significantly (p<0.05) to 54% and 61% in groups II and III and left-atrial pressure to 50% and 71%, respectively. Systolic and mean arterial pressure did not change significantly (p<0.05), while the diastolic pressure increased (p<0.05) to 134% and 138% in groups II and III. After mechanical unloading whether during ischemia or during reperfusion systolic wall thickening in the postischemic area recovered to 103% and 92% of preischemic control in groups II and III, respectively. Recovery was incomplete in the non-unloaded controls (76%) (p<0.05 versus groups II and III). Post-ejection thickening, a diastolic measure of stunning, diminished significantly after unloading in both protocols (p<0.05 for groups II and III versus group I). We conclude that mechanical unloading with the 60 ml Medos(R) HIA-VAD(R) significantly improves recovery from myocardial stunning.