Methods

We performed a retrospective analysis of hospitalizations for ACHD surgery for discharges of patients 21 to 65 years of age from 2000 and 2011, using unmasked patient discharges, using data from the Office of Statewide Health Planning and Development. This database consists of deidentified demographic, clinical, and administrative data from all acute care hospitals in California. The use of this data set to examine patterns of specialty care hospitalization has been previously described.

Our study population was identified using a method similar to that of Karamlou et al. In addition to the 12 International Classification of Diseases, Ninth Revision (ICD-9), codes used, we added 6 additional ICD-9 codes we believed would capture most ACHD diagnoses ( Table 1 ). Ventricular septal defects associated with myocardial infarction were excluded. Other diagnoses, such as congenital aortic stenosis or regurgitation or pulmonary valve stenosis, were not included in the analysis given ambiguity in coding and variable complexity per guideline classification. ACHD surgical procedures were defined as open heart or thoracic surgery occurring in 1 of the 18 selected ICD-9 diagnostic groups. The ICD-9 procedural codes for cardiac transplantation (37.5x, 37.6x) and surgically coded procedures performed with a transcatheter approach were excluded from the data set. All CHD ICD-9 diagnosis codes were cross-referenced with ICD-9 procedural codes, and inference was made for CHD diagnosis by type of cardiac surgery by the method previously described. The most complex CHD lesion noted was used for grouping as simple, moderate, or complex according, to the extent possible with ICD-9 codes, to 2008 guidelines for the management of adults with CHD ( Table 1 ).

Patient-level covariates included age, gender, race, ethnicity, payer mix, distance to specialty ACHD center (centroid of ACHD center ZIP code to centroid of patient ZIP code), and presence of morbidities as previously defined by Elixhauser et al.

The specialty ACHD center designation was based on program or institution listing in a national, volunteer clinical ACHD program registry. The directory is maintained and supported jointly by the Adult Congenital Heart Association, a nonprofit patient advocacy organization, and the International Society for Adult Congenital Heart Disease ( http://www.achaheart.org/home/clinic-directory.aspx , accessed March 2013). At the time of data analysis (2013), there were approximately 100 specialty centers in the United States, with 11 such centers in California. During our study period of 2000 to 2011, 5 of these specialty centers were established, therefore requiring us to adjust our analyses accordingly.

We provide descriptive analyses summarized as means and SDs for continuous variables and as proportions for categorical variables. Demographic and clinical differences among discharges were analyzed using chi-square tests for categorical variables and Student’s t tests for continuous variables. Covariates associated with the primary outcome (ACHD surgery in patients with moderate or complex CHD being performed at a specialty ACHD center) were determined using multivariate logistic regression analysis. A 2-sided p value <0.05 was deemed statistically significant. Analyses were performed using SAS version 9.3 (SAS Institute, Inc., Cary, North Carolina).

The study activities were approved by the Stanford University Institutional Review Board and the State of California Committee for the Protection of Human Subjects.

Results

We identified 4,611 discharges that met the inclusion criteria. The discharge characteristics and a comparison of these characteristics between specialty and nonspecialty centers are listed for the entire cohort in Table 2 . In-hospital mortality was uncommon for specialty ACHD centers and nonspecialty centers (3.2% and 2.9%, respectively, p = 0.58).

Of the 4,611 discharges, 753 ACHD procedures (16%) were performed in patients with moderate or complex CHD. The discharge characteristics and a comparison of these characteristics between specialty and nonspecialty centers are listed in Table 3 . Most ACHD procedures in moderate or complex CHD were performed at specialty centers (465 [62%]). However, as demonstrated in Figure 1 , a large number of nonspecialty centers were involved in performing a small number of these operations, with 88% of the nonspecialty centers having very low surgical volume (≤10 cases from 2000 to 2011). In-hospital mortality for moderate and complex CHD at specialty and nonspecialty centers was 4.1% and 2.8%, respectively (p = 0.35).

Table 3

Characteristics associated with discharge from a specialty adult congenital heart center for moderate/complex congenital heart disease: univariate analysis

Table 1	Total = 753	Non-specialty = 288		ACHD specialty = 465		P value
	N	N	(%)	N	(%)
Age years: (mean ±sd)	37.1±11.7	39.9±12.3		35.3±11.0		<0.001
Gender						NS
Male	349	144	(41%)	205	(59%)
Female	404	144	(36%)	260	(64%)
Race						NS
Asian	70	24	(34%)	46	(66%)
Black	32	10	(31%)	22	(69%)
Hispanic	196	82	(42%)	114	(58%)
Other/Unknown	30	7	(23%)	23	(77%)
White	425	165	(39%)	260	(61%)
Number of co-morbidities						NS
0	279	104	(37%)	175	(63%)
1	228	91	(40%)	137	(60%)
2	153	53	(35%)	100	(65%)
3+	93	40	(43%)	53	(57%)
Payer						0.009
Private: HMO	257	117	(46%)	140	(54%)
Private: Non-HMO	238	78	(33%)	160	(67%)
Public/Other	258	93	(36%)	165	(64%)
Region						<0.001
Bay Area	175	51	(29%)	124	(71%)
Farm Belt	137	72	(53%)	65	(47%)
Los Angeles (LA)	173	77	(45%)	96	(55%)
North and Mountain	22	6	(27%)	16	(73%)
Southern California without LA	246	82	(33%)	164	(67%)
Distance to nearest ACHD center						<0.001
0-5	104	24	(23%)	80	(77%)
6-10	123	50	(41%)	73	(59%)
11-20	174	69	(40%)	105	(60%)
21-40	139	49	(35%)	90	(65%)
41+	213	96	(45%)	117	(55%)
Vital status at end of hospitalization						NS
Alive	726	280	(39%)	446	(61%)
Dead	27	8	(30%)	19	(70%)

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