Novel Formula to Calculate Three-Dimensional Angle Between Inflow Cannula and Device Body of HeartMate II LVAD

Abstract

The acute angle between inflow cannula and device body of HeartMate II left ventricular assist device (LVAD) (Abbott, Pleasanton, California) is associated with device thrombosis. However, most studies utilized two-dimensional (2D) angle obtained from chest roentgenogram (CXR), which is unlikely accurate. We aimed to create and validate a formula to estimate actual three-dimensional (3D) angle. We retrospectively reviewed the cohort undergoing HeartMate II LVAD implantation between 2008 and 2016. A formula for calculating 3D angles of the LVAD inflow cannula relative to the device body was mathematically derived, using simple 2D measurements from CXR. The cohort included consecutive 275 patients with HeartMate II (median age: 60 [25% quartile: 51, 75% quartile: 68] years). There was no significant difference between the calculated 3D angles (from formula) and actual 3D angles (from computed tomography) from the subset group with 3D computed tomography (n= 28) (71.7° ± 13.4° vs 71.1° ± 11.5°, P= .858). Among all participants, the calculated 3D angle (from formula) was 74.4° ± 14.2°, which was significantly larger than the 2D projected angle (from CXR) (65.2° ± 11.3°, P < .001). There was no statistical difference in the calculated 3D angles (from formula) between patients with/without device thrombosis, hemorrhagic stroke, ischemic stroke, or mortality (P > .05 for all). We established a novel formula to mathematically calculate actual 3D angles between inflow cannula and device body of HeartMate II. The formula would help investigators to validate their findings of the relationship between 2D projected angle (from CXR) and device thrombosis.