Left-Ventricular Unloading with a New Pulsatile Assist Device: the HIA-VAD System and its Influence on Myocardial Stunning

Summary

To assess the mechanical unloading properties of a new pneumatic cardiac assist device (60 ml Medos® HIA-VAD®) 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® HIA-VAD®, significant unloading could be demonstrated: left-ventricular dP/dtmax 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 concludc that mechanical unloading with the 60 ml Medos® HIA-VAD® significantly improves recovery from myocardial stunning.

Zusammenfassung

Es wird über experimentelle Untersuchungen an 12 Schafen berichtet, an denen das HIA-VAD Assistenz-System zur Entlastung des linken Ventrikels eingesetzt wurde. Die Myokardschädigung wurde durch eine 15 Minuten dauernde Koronararterien-Okklusion erzielt. Folgende hämodynamischen Parameter wurden gemessen: HZV, systemische arterielle Drucke, linksventrikulärer Druck, Pulmonalarteriendruck und der Druck in beiden Vorhöfen. Außerdem wurde die regionale Myokardfunktion mittels Messung der Wanddicke bestimmt. Vier Tiere ohne linksventrikuläre Entlastung dienten als Kontrolle. Mit diesem Assistenz-System, das während der Ischämie oder in der Reperfusionsphase angewendet wurde, ließ sich eine deutliche Erholung des geschädigten Myokards erzielen.

Key words

Cardiac assist device - Mechanical unloading - Myocardial stunning - HIA-VAD