Background
Predischarge (pre-d/c) transthoracic echocardiography (TTE) is routine after surgery for congenital heart disease, but how it affects clinical care is unknown. The aim of this study was to test the hypothesis that pre-d/c TTE frequently reveals findings associated with short-term clinical course through a systematic review of findings on pre-d/c TTE and clinical events that followed.
Methods
Clinical outcomes of mortality, hospitalization, catheterization, and surgery at 1 year were examined for pediatric patients undergoing pre-d/c TTE between June 2010 and June 2012. Using logistic regression, a multivariate model was generated associating clinical, pre-d/c transthoracic echocardiographic, and demographic variables with unplanned postdischarge cardiac events (UCEs) within 1 year.
Results
Of 462 patients who underwent pre-d/c TTE, there were 265 male patients (57%) and 197 female patients (43%); the median age was 0.8 years (range, 0–33 years). Two hundred thirty–seven patients (51%) had findings (valve regurgitation, hemodynamic obstruction, ventricular dysfunction, unintended shunt, or pericardial effusion) on pre-d/c TTE, 57 of which were of more than mild severity. Agreement between pre-d/c TTE and postoperative transesophageal echocardiographic findings was only fair to moderate (κ = 0.27–0.43). Sixty-four patients (14%) had UCEs. Univariate analysis revealed that UCE were more frequent in patients with diagnoses and surgical procedures of high complexity. After accounting for these confounding nonechocardiographic variables, pre-d/c transthoracic echocardiographic findings, specifically valve regurgitation of more than mild severity, and ventricular dysfunction and obstructions of any severity were independently associated with UCEs (odds ratios, 1.90, 1.99, and 1.85, respectively).
Conclusions
Findings on pre-d/c TTE are frequent, commonly discordant with postoperative transesophageal echocardiographic results, and associated with adverse clinical events after surgery for congenital heart disease. These data would strongly support the practice of pre-d/c TTE after surgery for congenital heart disease.
Transthoracic echocardiography (TTE) is the primary imaging modality for the evaluation of congenital heart disease (CHD). Infants, children, and adolescents with CHD commonly undergo echocardiographic examinations to evaluate disease progression because it provides a noninvasive assessment of valvular function, ventricular function, dimensions of cardiovascular structures, and the results of medical or surgical intervention.
Despite its broad application in adult and pediatric practice, there are remarkably few data to quantify the true benefits of echocardiography, regardless of age or clinical context. In response to the need for the rational use of imaging, the American College of Cardiology, the American Society of Echocardiography, and other imaging subspecialty societies have collaboratively developed appropriate use criteria for echocardiography. Appropriate use criteria for echocardiography in adults with CHD and for initial outpatient pediatric TTE are available, but criteria for pediatric inpatient echocardiography have not yet been developed.
Although predischarge (pre-d/c) TTE is common practice for pediatric patients after CHD surgery, the associations of pre-d/c TTE with clinical outcomes are unknown, and there are neither data nor consensus on its benefits. If it provides new data that allow informed clinical management that fosters better outcomes, then imaging at dismissal after CHD surgery would be of high value and would potentially decrease health care costs. However, if pre-d/c TTE adds few new data, then this frequently used diagnostic test would serve primarily to increase cost of care. Therefore, understanding the diagnostic yield of pre-d/c TTE in terms of the detection of residual unintended shunts, obstructions, valve regurgitation, myocardial dysfunction, and pericardial effusion is important. Moreover, understanding the associations these findings might have with future clinical events could establish the importance of pre-d/c TTE in anticipatory management of surgically modified CHD. The purpose of this investigation was to test the hypothesis that findings on pre-d/c TTE are associated with death or the need for additional care during short-term follow-up. Therefore, we sought to document the frequency of findings on pre-d/c TTE in patients who underwent CHD surgery and the frequency of postdischarge events and to investigate the relation, if any, between the two.
Methods
This was an institutional review board–approved retrospective cohort study performed at a university-affiliated academic children’s hospital. Pre-d/c TTE is performed as part of routine protocol for patients who have undergone cardiovascular surgery at this institution. Pediatric cardiology databases were used to identify consecutive patients who underwent cardiovascular surgery between June 2010 and June 2012. Clinical characteristics, cardiac history, results of transesophageal echocardiography (TEE), and pre-d/c transthoracic echocardiographic data were obtained from medical record review.
Because of the likelihood that the cardiac diagnosis and the nature of the surgical procedure would be confounding variables associated with postdischarge events, these variables were collected for later use along with pre-d/c transthoracic echocardiographic results in multivariate analysis. Accordingly, patients were assigned by primary cardiac lesion into the most complex applicable category of the following: (1) atrial septal defect and anomalies of pulmonary venous connection, including secundum and venosus defects, patent foramen ovale, and partial or total anomalous pulmonary venous connections; (2) ventricular septal defect, including perimembranous, doubly committed subarterial, muscular, and double-outlet right ventricle type; (3) atrioventricular septal defects, complete or partial; (4) complex biventricular disease, including truncus arteriosus, tetralogy of Fallot, pulmonary atresia with ventricular septal defect, and d- and l-transpositions of the great arteries; (5) aortic valve and subaortic disease; (6) aortic arch or supravalve ascending aortic disease or mitral valve disease; (7) univentricular heart; (8) cardiomyopathies, pericardial disease, coronary artery disease, and arrhythmias; (9) patent ductus arteriosus, aortopulmonary window, and other great arterial shunts; and (10) pulmonary and tricuspid valve disease, including Ebstein’s anomaly and pulmonary branch stenosis.
To account for the possibility that risk for postdischarge event might be related more to the complexity of the surgery than to the general surgical category, patients were also categorized according to the Risk Adjustment for Congenital Heart Surgery classification, a consensus-based method that has been validated to provide risk adjustment for comparisons of in-hospital mortality after surgery for CHD.
Echocardiography
In accordance with the recommended standards and guidelines for pediatric echocardiography set by the Intersocietal Accreditation Commission Echocardiography and the American Society of Echocardiography, the institutional pre-d/c transthoracic echocardiographic protocol consisted of complete cardiac examinations performed by seven registered cardiac sonographers. The findings on pre-d/c TTE were grouped into five categories: residual valvular regurgitation, residual obstruction (valvular or outflow tract), residual unintended shunt, pericardial effusion, and ventricular dysfunction. Positive findings on pre-d/c TTE were reviewed and subclassified by a board-certified pediatric cardiologist (S.K.) as mild or greater than mild. To address the issue of subjectivity in the assessment of findings, a second observer (L.L.) reviewed and independently assessed all pre-d/c transthoracic echocardiograms. Interobserver differences between the two observers were evaluated, and in instances in which there were differences between the two, a third observer (D.A.D.) reviewed those studies and reconciled the differences. “Abnormal” findings that were intentional or expected for a particular disease (e.g., surgically created atrial communications, ventricular septal defect left open, pulmonary band) were not included as positive findings.
Follow-Up
Follow-up data 1 year after pre-d/c TTE were collected from hospital records and primary care physician office records to identify the occurrence of unplanned cardiac events (UCE), defined as mortality of cardiac cause, heart surgery, cardiac catheterization, and hospitalization for management of cardiac symptoms. Noncardiac events, such as hospitalization for evaluation of gastrointestinal conditions (diarrhea, vomiting, or abdominal pain), respiratory conditions (pneumonia, pleural effusion), noncardiac surgery (tracheostomy; ear, nose, and throat procedure; feeding tube procedure; sternal wire removal), infections (fever, sepsis, urinary tract infection), or failure to thrive, were not considered events. Planned cardiac events that would be routinely undertaken within 1 year of surgery (e.g., bidirectional Glenn shunt after Norwood operation for hypoplastic left heart syndrome) were also not counted as events.
Statistical Analysis
Descriptive statistics for categorical variables are reported as frequencies and percentages. Categorical variables were compared between the event and event-free outcome groups using χ 2 tests. Stepwise multiple variable binary logistic regression was used to generate a model associating variables (clinical features, results of pre-d/c TTE, diagnostic category, and Risk Adjustment for Congenital Heart Surgery category) with postdismissal event. The α values to enter and to exclude variables from the stepwise process were both 0.15. Quantitative assessments of agreement between pre-d/c TTE observers and between pre-d/c TTE and TEE were made using Cohen’s κ statistic, with description of the strength of agreement expressed according to published standards. Odds ratios with 95% confidence limits are reported for the components of the final model. In accordance with usual standards, the number of variables allowed as candidate variables for entry into the stepwise multiple variable modeling process was n /10, where n is the size of the less frequent response category ( n = 64 for UCEs). Those variables, up to a maximum of n /10, with the strongest univariate associations were therefore candidate variables for inclusion in stepwise regression. To limit the likelihood of reporting spurious associations with outcomes due to the large number of variables considered, univariate associations with odds ratios are reported only for candidate variables. Statistical analysis was performed with commercially available computer software (Minitab version 16.0; Minitab Inc, State College, PA).
Results
Characteristics of the Study Population
The study population consisted of 462 patients who underwent pre-d/c TTE out of a total 498 patients who underwent CHD surgery. The median age was 0.8 years (range, 0–33 years). There were 265 male patients and 197 female patients (43%). Four hundred twenty patients (91%) underwent a single operation, and 42 (9%) underwent more than one operation during the hospital stay. There were 396 patients (86%) operated for biventricular CHD and 66 (14%) for univentricular heart disease. The median length of hospital stay was 5 days, and the median duration from pre-d/c TTE to hospital discharge was 1 day.
Findings on Pre-d/c TTE
The distribution of pre-d/c transthoracic echocardiographic studies by cardiac diagnostic category is shown in Table 1 . There were 273 findings identified on pre-d/c TTE (categorized in Table 1 ), of which 57 were of greater than mild severity. There were 85 pre-d/c transthoracic echocardiograms with multiple findings. Cohen’s κ for interobserver agreement on pre-d/c transthoracic echocardiographic findings was 0.95 for degree of obstruction, 0.85 for degree of regurgitation, 1.0 for magnitude of residual shunt, 0.92 for severity of ventricular dysfunction, and 1.0 for size of pericardial effusion, indicating strong agreement in all areas.
| Distribution | |
|---|---|
| Diagnosis category | |
| 1. Atrial septal defect and anomalies of pulmonary venous connection | 41 (8.9%) |
| 2. Ventricular septal defects | 38 (8.4%) |
| 3. Atrioventricular septal defects, complete or partial | 24 (5.2%) |
| 4. Complex biventricular disease, including truncus arteriosus, tetralogy of Fallot, pulmonary atresia with ventricular septal defect, and d- and l-transposition of the great arteries | 125 (27.1%) |
| 5. Aortic valve and subaortic disease | 40 (8.7%) |
| 6. Aortic arch or supravalve ascending aortic disease or mitral valve disease | 62 (13.4%) |
| 7. Univentricular heart | 66 (14.3%) |
| 8. Cardiomyopathies, pericardial disease, coronary artery disease and arrhythmias | 23 (5%) |
| 9. Patent ductus arteriosus, aortopulmonary window and other great arterial shunts | 26 (5.6%) |
| 10. Pulmonary and tricuspid valve disease, including Ebstein’s anomaly and pulmonary branch stenosis | 16 (3.5%) |
| Findings on pre-d/c TTE in all patients | |
| Residual regurgitation | 177 (45.4%) |
| Residual stenosis | 60 (15.4%) |
| Residual shunt | 58 (14.9%) |
| Systemic ventricular dysfunction | 52 (13.3%) |
| Pericardial effusion | 43 (11.0%) |
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