Table 1.
Patient characteristics and postoperative outcomes stratified by center volume
| Variable | Low Volume (N=1,173) |
Medium Volume (N=5,353) |
High Volume (N=11,700) |
P-Valuea |
|---|---|---|---|---|
| Demographics | ||||
| IMPACT score (±SD) | 6.3 (4.0) | 6.2 (3.7) | 6.2 (3.8) | 0.8 |
| Age, years (±SD) | 48.9 (13.9)b | 51.7 (11.9)b | 52.5 (12.1) | <0.01 |
| Female, n (%) | 262 (22.4%) | 1,318 (24.6%) | 2,731 (23.3%) | 0.1 |
| Caucasian, n (%) | 839 (71.5%)b | 3,792 (70.8%)b | 8,697 (74.3%) | <0.01 |
| African-American, n (%) | 226 (19.3%)b | 952 (17.8%)b | 1,810 (15.5%) | <0.001 |
| Diagnosis, n (%) | <0.01 | |||
| Idiopathic | 452 (38.5%) | 2,288 (42.7%) | 4,988 (42.6%) | |
| Ischemic | 535 (45.6%) | 2,508 (46.9%)b | 5,165 (44.2%) | |
| Congenital | 89 (7.6%)b | 95 (1.8%)b | 285 (2.4%) | |
| Other | 97 (8.3%) | 462 (8.6%) | 1,262 (10.8%) | |
| Acuity | ||||
| HTN, n (%) | 373 (39.7%) | 1,593 (44.0%)b | 3,200 (39.0%) | <0.01 |
| Diabetes Mellitus, n (%) | 220 (18.9%)b | 1,301 (24.5%) | 2,677 (23.2%) | <0.01 |
| Creatinine Clearanceb, ml/min (±SD) | 68.8 (27.1)b | 67.3 (27.1)b | 65.5 (25.5) | <0.01 |
| Serum bilirubin, mg/ml (±SD) | 1.4 (3.1)b | 1.2 (2.2) | 1.3 (2.3) | 0.02 |
| Preop Mechanical Ventilation | 34 (2.9%) | 172 (3.2%)b | 277 (2.4%) | <0.01 |
| Ischemic time, hours (±SD) | 3.0 (1.1)b | 3.1 (1.0)b | 3.3 (1.0) | <0.01 |
| Temporary Circulatory Supportd, n (%) | 26 (2.2%)b | 62 (1.2%) | 165 (1.4%) | 0.1 |
| Ventricular Assist Device | ||||
| Early Generatione, n (%) | 188 (16.0%) | 891 (16.6%)b | 1,724 (14.7%) | <0.01 |
| Late Generationf, n (%) | 5 (0.4%) | 34 (0.6%) | 45 (0.4%) | 0.08 |
| Heartmate II, n (%) | 24 (2.1%)b | 307 (5.7%)b | 571 (4.9%) | <0.01 |
| IABP, n (%) | 43 (3.7%)b | 267 (5.0%) | 656 (5.6%) | <0.01 |
| Postoperative Outcomes | ||||
| Need for cardiac reoperation, n (%) | 120 (13.0%) | 409 (11.7%) | 881 (11.6%) | 0.4 |
| Stroke, n (%) | 26 (2.2%) | 140 (2.6%) | 250 (2.2%) | 0.2 |
| New onset dialysis, n (%) | 113 (9.9%)b | 423 (8.1%)b | 799 (7.2%) | <0.01 |
| Treated rejection in first year, n (%) | 355 (40.3%)b | 1,457 (34.4%)b | 2,598 (28.8%) | <0.01 |
P-value based on Analysis of Variance(continuous variables) or chi-square test (categorical variables)
Post-hoc pairwise comparison p<0.05 (reference = high volume) by Tukey-Kramer method for continuous variables or univariate logistic regression for categorical variables
Based on Cockcroft-Gault Calculation
Includes ECMO and/or extracorporeal VADs i.e.Abiomed BVS5000 (Abiomed, Inc. Danvers, MA), Bio-Medicus(Medtronic Inc. Eden Prairie, MN), TandemHeart (Cardiac Assist, Inc., Pittsburg PA) and Levitronix/Centrimag(Levitronix, Waltham, MA)
Early generation includes para and intracorporeal pulsatile VADs including Abiomed AB5000, Heartmate I, XE and XVE, ThortecIVAD(Thoratec Corp, Pleasanton, CA), Toyobo(Toybo Osaka, Japan), Novacor(World Heart Inc, Oakland CA), Medos(Medos Stolberg, Germany) and LionHeart(Arrow International Inc, Reading PA).
Later generation continuous VADs including Jarvik(Javik Heart Inc, New York, NY), Micromed, Debakey(MicroMed Technology Inc. Houston, TX) and VentrAssist(Ventracor, Sydney, Australia), excluding Heartmate II
Abbreviations: IMPACT=index for mortality prediction after cardiac transplantation; HTN=hypertension; PVR=pulmonary vascular resistance; hrs=hours; IABP=intra-aortic balloon pump.