Relationship of IFC Position to Preoperative Anatomy
We prospectively assessed anatomic variables that previously predicted Heartmate II IFC malposition. These included LVEDD, BMI, LV apex-midline distance, and LV apex-LVOT angle.
We did not find a relationship between LVEDD and malposition. A smaller LVEDD was associated with mortality and stroke in CF-LVADs6. We also found no association between malposition and PT/eCVA or mortality, as discussed below. Additional contributing factors beyond pump position likely explain this relationship.
We also found no relationship between BMI and malposition. A large INTERMACS registry study linked obesity with device malfunction and thrombosis, as well as readmissions7. However, only 16.8% of patients in that study received a CF-LVAD. It is possible that the smaller profile CF-LVADs makes them less sensitive to the effects of abdominal obesity than Heartmate II, which requires a pre- or intra-peritoneal pocket.
Both CT imaging measurements predicted malposition. A larger midline-LV apex distance was associated with increasingly septal IFC deviation. Additionally, a steeper LVOT angle predicted IFC deviation toward both the inferior wall and lateral walls.
A larger midline-LV apex distance indicates a more laterally and posteriorly displaced apex. This may increase the risk of malposition by making it difficult to reach the “true” apex. This is exacerbated in LTHS patients if the thoracotomy is not sufficiently lateral. Additionally, in these patients, the heart often impinges on the ribcage, so the pump can be displaced by the ribs at closure. By contrast, a shorter midline-LV apex distance predicted increased lateral-wall malposition. This measurement suggests an apex closer to midline, where the anterior chest wall could push the pump medially at closure.
A steeper LVOT angle indicates a more vertically-oriented heart. Since the natural lie of the CF-LVAD is horizontal, inserting it an up-tilted ventricle will tend to point it inferior to the apex-MV axis. The apex in these heart also tend to be more medial, which could portend a laterally displaced IFC by the mechanism discussed above.
Having become more cognizant of malposition risk, we routinely use preoperative CTs to select the intercostal space and extent of incision for LTHS procedures. We also obtain biplanar transesophageal echo imaging both before and after the chest is closed, since a uniplanar four-chamber view will miss inferior-wall malposition. We also have found preliminary success in repositioning CF-LVADs via a thoracotomy by pulling them inferiorly and securing them to a rib.