Table 1.
Baseline Characteristics Stratified by Type of Implantable Cardioverter-Defibrillator (ICD)
| Characteristic | Total (n = 87 115) |
DC ICD (n = 50 626) |
SC ICD (n = 36 489) |
P Value |
|---|---|---|---|---|
| Demographics | ||||
| Age, mean (SD), y | 62.81 (13.17) | 64.13 (12.72) | 60.97 (13.55) | <.001 |
| Female, No. (%) | 23 763 (27.28) | 13 410 (26.49) | 10 353 (28.37) | <.001 |
| Race/ethnicity, No. (%) | ||||
| White | 61 382 (70.46) | 36 543 (72.18) | 24 839 (68.07) | <.001 |
| Black | 17 115 (19.65) | 9041 (17.86) | 8074 (22.13) | |
| Hispanic | 5466 (6.27) | 3169 (6.26) | 2297 (6.30) | |
| Other | 3152 (3.62) | 1873 (3.70) | 1279 (3.51) | |
| Comorbidities, No. (%) | ||||
| Atrial fibrillation/atrial flutter | 14 804 (16.99) | 9942 (19.64) | 4862 (13.32) | <.001 |
| Cerebrovascular disease | 10 784 (12.38) | 6558 (12.95) | 4226 (11.58) | .06 |
| Chronic lung disease | 19 561 (22.45) | 11 835 (23.38) | 7726 (21.17) | <.001 |
| Diabetes mellitus | 32 939 (37.81) | 19 134 (37.79) | 13 805 (37.83) | .07 |
| Hypertension | 66 090 (75.87) | 39 226 (77.48) | 26 864 (73.62) | <.001 |
| Renal failure–hemodialysis | 3313 (3.80) | 1856 (3.67) | 1457 (3.99) | <.001 |
| Physician characteristics | ||||
| Physician volume, mean (SD), No. | 54.22 (42.73) | 52.89 (40.93) | 56.07 (45.03) | <.001 |
| EP operator ICD training, No. (%) | ||||
| Board-certified EP | 60 514 (74.05) | 34 654 (72.53) | 25 860 (76.18) | <.001 |
| EP fellowship only | 5157 (6.31) | 2943 (6.16) | 2214 (6.52) | |
| Surgery boards | 1644 (2.01) | 1130 (2.37) | 514 (1.51) | |
| Pediatrics cardiology boards | 66 (0.08) | 47 (0.10) | 19 (0.06) | |
| Credentialeda | 8917 (10.91) | 5683 (11.89) | 3234 (9.53) | |
| Other | 5425 (6.64) | 3321 (6.95) | 2104 (6.20) | |
| Hospital characteristics | ||||
| Hospital annual volume, mean (SD) | 213.2 (152.9) | 210.4 (151.8) | 217.1 (154.4) | <.001 |
| Geographic location, No. (%)b | ||||
| New England | 3449 (3.96) | 1254 (2.48) | 2195 (6.02) | <.001 |
| Mid Atlantic | 12 951 (14.88) | 5887 (11.64) | 7064 (19.38) | |
| South Atlantic | 20 819 (23.92) | 12 224 (24.17) | 8595 (23.58) | |
| Northeast Central | 15 734 (18.08) | 9546 (18.87) | 6188 (16.97) | |
| Southeast Central | 7867 (9.04) | 4636 (9.17) | 3231 (8.86) | |
| Northwest Central | 6479 (7.44) | 4463 (8.82) | 2016 (5.53) | |
| Southwest Central | 9571 (11.00) | 5819 (11.50) | 3752 (10.29) | |
| Mountain | 3518 (4.04) | 2340 (4.63) | 1178 (3.23) | |
| Pacific | 6649 (7.64) | 4412 (8.72) | 2237 (6.14) | |
| Profit type, No. (%) | ||||
| Government | 1574 (1.81) | 1091 (2.16) | 483 (1.32) | <.001 |
| Private/community | 72 559 (83.29) | 43 173 (85.28) | 29 386 (80.53) | |
| University | 12 982 (14.90) | 6362 (12.57) | 6620 (18.14) | |
| Community, No. (%) | ||||
| Rural | 8796 (10.10) | 5107 (10.09) | 3689 (10.11) | <.001 |
| Suburban | 23 561 (27.05) | 14 273 (28.19) | 9288 (25.45) | |
| Urban | 54 758 (62.86) | 31 246 (61.72) | 23 512 (64.44) | |
| Patient beds, mean (SD), No. | 481.2 (255.4) | 468.0 (249.4) | 499.5 (262.4) | <.001 |
| Teaching | 48 282 (55.42) | 26 413 (52.17) | 21 869 (59.93) | <.001 |
| With EP laboratory | 58 634 (67.31) | 34 503 (68.15) | 24 131 (66.13) | <.001 |
Abbreviations: DC, dual-chamber; EP, electrophysiologist; SC, single-chamber.
a
Credentialed refers to an alternative pathway for non-EP physicians to be “credentialed” to perform ICD implants. It was strictly voluntary and has subsequently expired, such that no additional physicians will be characterized as being credentialed through this alternative pathway.
b
As defined by the US Census.18