Abstract 12144: The Association Between High Cardiac Index and Mortality

Background: Elevated cardiac index (CI) is implicated in the pathophysiology of heart failure. However, data on the CI hemodynamic spectrum that is associated with adverse outcome are lacking. We hypothesized that elevated CI is associated with increased mortality in patients referred for right heart catheterization (RHC).

Methods and Results: We retrospectively assembled data for patients undergoing RHC at Vanderbilt University (1998-2013) with ≥ 1 yr follow-up, excluding patients with low CI (<2.2 L/min/m ² ) which is known to be associated with increased mortality (N=2,548; age median 60 IQR [50-69] yrs; male, 50%; body mass index [BMI], 29 [25-35] kg/m ² ). Univariate Cox-regression was used to assess the association between CI (measured by thermodilution) octile and all-cause mortality (N=925 [36%] events, time to event 4.7 [3.1-8.8] yrs). All-cause mortality was 31% higher in the highest CI octile (N=317; 4.1 [3.9-4.7] L/min/m ² ; HR=1.31 [95%CI: 1.01-1.71], P=0.046) compared to the CI octile with lowest mortality risk (N=311; 3.1 [3.0-3.2] L/min/m ² ). Patients with CI >4.1 L/min/m ² were younger (54 [46-63] vs. 60 [49-67] yrs, P<0.001) and had lower BMI (28 [24-34] vs. 31 [26-36] kg/m ² , P<0.001), pulmonary vascular resistance (1.4 [0.9-2.4] vs. 1.8 [1.3-2.7] WU, P<0.001), and hemoglobin (11.9 [10.3-13.7] vs. 12.7 [11.1-13.8] g/dL, P=0.003); similar mean pulmonary arterial pressure (27 [19-35] vs. 26 [20-36] mmHg, P=0.556), pulmonary arterial wedge pressure (13 [8-18] vs. 13 [9-18] mmHg, P=0.352), frequency of hemodialysis (11% vs. 9%, P=0.259) and hyperthyroidism (2% vs. 1%, P=0.491); but significantly higher frequency of liver cirrhosis (18% vs. 7%, P<0.001) compared to the low risk CI group. The mortality association for CI >4.1 L/min/m ² remained significant after adjusting for age, sex, liver cirrhosis and hemodialysis (HR 1.34 [95%CI 1.03-1.76], p=0.032).

Conclusion: Cardiac index >4.1 L/min/m ² is associated with a significant increase in all-cause mortality among patients referred for RHC, even after adjusting for established risk factors for high-output heart failure. These data expand the mortality continuum related to CI and support further studies that clarify the clinical phenotype of at-risk patients.