Background
Aortic regurgitation (AR) significantly hampers the unloading effect and the antegrade flow enhancement expected from the micro-axial flow pump Impella (Abiomed, Danvers). To date, no dedicated hemodynamic index is available to inform on the severity of AR during Impella support.
Methods
We included 100 patients receiving Impella support for CS with invasive hemodynamic assessment with pulmonary artery catheter (PAC). PAC measures were obtained 48 hours after Impella support initiation. AR grading was performed by either trans-thoracic or trans-esophageal echocardiography in the following strata: 0-none; 1-mild; 2-moderate; 3-moderate-severe; 4-severe. Study cohort was dichotomized according to AR severity≥2+. Several relevant hemodynamic indexes were validated against echocardiographic AR assessment to identify those mostly associated with significant AR (AR severity≥2+), including: AR index [ARI, calculated as (diastolic arterial pressure – pulmonary artery wedge pressure)/systolic arterial pressure, abbreviated in (DAP-PAWP)/SAP], diastolic pulse pressure (DPP, calculated as DAP-PAWP), MAP-adjuster ARI [ARIMAP calculated as (diastolic arterial pressure – pulmonary artery wedge pressure)/mean arterial pressure, abbreviated in (DAP-PAWP)/MAP)].
Results
Significant AR (≥2+) was found in 31% patients. Patients with AR≥2+ had higher values of pulmonary artery wedge pressure (PAWP) after 48 hours from support initiation [15 (12, 21) vs 12 (10, 16) mmHg; 0.021]. Several invasive hemodynamic indexes differentiated AR≥2+ vs AR<2 patients, including: ARI [0.42 (0.36, 0.51) vs 0.50 (0.44, 0.61); 0.001], DPP [47 (37, 58) vs 57 (48.00, 68) mmHg; p=0.003] and ARIMAP [0.62 (0.54, 0.70) vs 0.70 (0.64, 0.75); p=0.005] (Figure 1). ARI demonstrated the strongest association and the greatest accuracy in identifying AR≥2+ (area under the curve 0.73; 95%CI: 0.61-0.85; p=0.002). The threshold of ARI 0.39 had excellent specificity (88.0%) and moderate sensitivity (62.9%), Figure 2. Conclusions The easy-to-use ARI metric [(DAP-PAWP)/SAP] accurately identifies patients with significant AR during Impella support, at the optimal cutoff of ARI 0.39. This index may be complementary to echocardiography in the assessment of AR during Impella support.
