Background
The detection of atrial septal defects (ASDs) and other shunts is sometimes difficult on transthoracic echocardiography. In addition, the quantitative assessment of right-heart volume loading as an indicator of significant shunting can be difficult, with subjective estimation commonly used. Thus, the initial aim of this study was to test the accuracy of a simple, noninvasive index using atrial area dimensions to detect the presence of an ASD. Subsequently, the index was used to assess the degree of normalization and remodeling of atrial size following percutaneous ASD device closure.
Methods
The relative atrial index (RAI) was derived from standard apical 4-chamber views as right atrial area divided by left atrial area. RAI was calculated in patients with previously diagnosed secundum atrial defects (n = 219) with no concomitant lesions and then compared with those calculated in age-matched controls (n = 219). 101 of the 219 patients with secundum atrial defects underwent percutaneous device closure. Measurements were obtained before and 1 day after percutaneous closure as well as in the early (mean, 124 days) and late (mean, 390 days) stages of follow-up.
Results
The mean RAI in patients with ASDs (1.23 ± 0.23) was significantly higher than that in the age-matched normal control group (0.78 ± 0.1) ( P < .0001). The mean RAI in patients with ASD was also significantly higher than that in the general population (0.81 ± 0.15) ( P < .0001). Receiver operating characteristic curve analysis suggested that a nominal RAI cutoff value of >0.92 predicted patients with ASDs versus matched controls with 99.1% sensitivity and 90.5% specificity. After percutaneous closure, significant atrial remodeling occurred immediately, with a reduction in the mean RAI at day 1 to 0.93 ± 0.16 ( P < .0001) and complete normalization at early follow-up to 0.81 ± 0.12.
Conclusion
The RAI, a novel and simple transthoracic parameter, reliably identifies patients with possible atrial shunting. The resolution of right atrial enlargement occurs remarkably early after percutaneous ASD closure, as demonstrated by this novel parameter.
Isolated secundum atrial septal defects (ASD) account for approximately 7% to 11% of all congenital cardiac defects. The detection of an ASD is important because this congenital condition, depending on shunt size, can result in significant volume overload of the right heart chambers, with secondary dilatation of the right ventricle (RV) and right atrium (RA), pulmonary hypertension, RV failure, atrial arrhythmias, and impaired aerobic capacity. With the progression of these changes in right-heart physiology, the potential for alteration in interventricular septal motion and impairment of left ventricular filling and ejection fraction also increases.
The detection of ASDs is occasionally difficult on transthoracic echocardiography (TTE). Because of the complex anatomy of the RV, the accurate assessment of right-heart volume loading, as an indicator of shunting, has been difficult to achieve, with subjective estimation commonly used. We therefore sought to determine the diagnostic accuracy of the atrial size ratio, known as the relative atrial index (RAI), for the detection of an ASD and its possible use as a screening tool to aid in avoiding a missed diagnosis. We also sought to determine if normalization of the RAI occurs following percutaneous Amplatzer (AGA Medical Corporation, Golden Valley, MN) secundum ASD device closure.
Methods
Patient Population
This was a retrospective review of routinely available data sourced from The Prince Charles Hospital echocardiographic database (ProSolv CardioVascular Analyzer; ProSolv CardioVascular, Indianapolis, IN). Information was obtained from a total of 438 individuals; patient demographics are summarized in Table 1 . Group 1 consisted of 219 patients (134 women; mean age, 29.7 ± 25.2 years) with previously diagnosed echocardiographic findings of isolated ASD and left-to-right shunting with no concomitant lesions. Group 2 consisted of 219 age-matched normal controls (119 women; mean age, 29.7 ± 25.2 years) with no cardiovascular pathology and normal echocardiographic findings.
Variable | Group 1: patients with secundum ASDs (n = 219) | Group 2: age-matched controls (n = 219) | P , group 1 vs group 2 |
---|---|---|---|
Age (y) | 29.7 ± 25.2 | 29.7 ± 25.2 | NS (.50) |
Men | 85 (39.0%) | 100 (46%) | |
Height (cm) | 160.6 ± 24.2 | 160.6 ± 26.4 | NS (.36) |
Weight (kg) | 68.6 ± 27.3 | 58.2 ± 27.5 | NS (.31) |
Body surface area (m 2 ) | 1.73 ± 0.48 | 1.56 ± 0.69 | <.0001 |
Rhythm | |||
Sinus | 204 (93.2%) | 219 (100%) | <.0001 |
Atrial fibrillation | 14 (6.4%) | 0 (0%) | <.0001 |
Paced rhythm | 1 (0.5%) | 0 (0%) | <.0001 |
Of the 219 patients (group 1) with secundum ASDs, 101 (46.1%) of these (57 women; mean age, 38 ± 21 years) were deemed suitable and underwent the implantation of percutaneous ASD devices. The remainder of the patients were treated medically (37.9%) because of small lesions or via surgical means (16.0%). RAI measurements were obtained before and after percutaneous ASD closure as well as in the early (mean, 124 days) and late (mean, 390 days) stages of follow-up.
Echocardiographic Data
Patients underwent standard transthoracic echocardiographic examinations according to the American Society of Echocardiography guidelines, using the echocardiographic parameters presented in Table 2 . Studies were performed using commercially available ultrasound systems (Philips iE33, Philips Medical Systems, Andover, MA; Hewlett-Packard 7500, Philips Medical Systems, Andover, MA; Vivid 7, GE-Vingmed Ultrasound AS, Horten, Norway; Acuson Sequoia, Siemens Medical Solutions, Mountain View, CA) and were performed by fully trained and experienced cardiac sonographers.
Group 1: patients with secundum ASDs | Group 2: age-matched controls | ||
---|---|---|---|
Variable | (n = 219) | (n = 219) | P |
LVEDD (mm) | 38.9 ± 10.0 | 42.0 ± 11.0 | .008 |
LVEDD indexed to BSA (mm/m 2 ) | 28.4 ± 11.8 | 29.0 ± 10.0 | NS |
LVEDV (mL) | 64.2 ± 6.7 | 74.3 ± 38.5 | NS |
LVEDV indexed to BSA (mL/m 2 ) | 44.9 ± 13.5 | 49.6 ± 11.3 | <.01 |
LVEF (%) | 66.7 ± 53.3 | 63.3 ± 5.6 | NS |
RVEDD, M-mode (mm) | 31.0 ± 3.6 | 19.0 ± 6.0 | <.0001 |
RVEDD indexed to BSA (mm/m 2 ) | 25.9 ± 25.9 | 14.0 ± 5.0 | <.0001 |
RV size (2-dimensional) | |||
Normal | 57 (26%) | 219 (100%) | <.0001 |
Mild | 102 (46.6%) | 0 (0%) | <.0001 |
Moderate | 43 (19.6%) | 0 (0%) | <.0001 |
Severe | 17 (7.8%) | 0 (0%) | <.0001 |
RV function | |||
Normal | 189 (86.3%) | 219 (100%) | <.0001 |
Mild | 23 (10.5%) | 0 (0%) | <.0001 |
Moderate | 3 (1.4%) | 0 (0%) | <.0001 |
Severe | 4 (1.8%) | 0 (0%) | <.0001 |
Diastolic function | |||
Normal | 182 (83.1%) | 193 (88.1%) | <.0001 |
Grade 1a | 9 (4.1%) | 26 (11.9) | <.0001 |
Grade 1b | 3 (3%) | 0 (0%) | <.0001 |
Grade 1c | 10 (10%) | 0 (0%) | <.0001 |
Grade 2 | 12 (5.5%) | 0 (0%) | NS |
Indeterminate | 3 (1.4%) | 0 (0%) | <.0001 |
TR quantity | |||
None | 115 (25.5%) | 149 (68%) | .0004 |
Trivial | 31 (14.2%) | 38 (17.4%) | .0004 |
Mild | 44 (20.1%) | 32 (14.6%) | .0004 |
Moderate | 20 (9.1%) | 0 (0%) | .0004 |
Moderately severe | 7 (3.2%) | 0 (0%) | .0004 |
Severe | 2 (0.9%) | 0 (0%) | .0004 |
MR quantity | |||
None | 137 (62.6%) | 151 (68.9%) | NS |
Trivial | 39 (17.8%) | 57 (26%) | NS |
Mild | 32 (14.6%) | 11 (5.0%) | NS |
Moderate | 10 (4.6%) | 0 (0%) | NS |
Severe | 1 (0.5%) | 0 (0%) | NS |
From the apical 4-chamber, view the RAI was derived by measuring the left atrial (LA) and RA areas. As per the American Society of Echocardiography guidelines, the atrial areas were measured at the end of ventricular systole, when the atrial chambers were at their greatest dimension. When measuring LA area, the pulmonary vein inlets and LA appendage were excluded. The RAI was then derived by dividing the RA area by the LA area ( Figure 1 ).
![](https://i0.wp.com/thoracickey.com/wp-content/uploads/2018/06/gr1-520.jpg?w=960)
RV size was initially measured from two-dimensional guided M-mode tracings performed from the parasternal long-axis view of the left ventricle. The RV cavity was measured at end-diastole from the endocardial surface of the anterior RV wall to the anterior endocardial surface of the interventricular septum. From the apical 4-chamber view, RV size was also assessed qualitatively. The RV was normal in size if the midcavity diameter was smaller than the left ventricle, mildly dilated if the RV diameter was approaching the same size as the left ventricle, moderately dilated if the RV diameter was similar to the left ventricle with sharing of the apex of the heart, and severely dilated if the RV diameter was greater than the left ventricle with the RV forming the apex. RV systolic function was estimated qualitatively on the basis of the displacement of the tricuspid annulus and the function of the RV free wall.
In the absence of RV outflow tract obstruction or pulmonary valve stenosis, RV systolic pressure was estimated via the tricuspid regurgitant jet using the simplified Bernoulli equation: RV systolic pressure = 4( V TR ) 2 + RAP, where V TR is the velocity of the tricuspid regurgitation signal, and RAP is RA pressure. RAP was estimated via observation of the caliber and reactivity of the inferior vena cava with respiration from the subcostal window. If the inferior vena cava was normal in size (≤1.7 cm), with a 50% decrease in size, RAP was estimated at 0 to 5 mm Hg. Once the inferior vena cava became dilated (>1.7 cm), with a ≥50% inspiratory collapse, RAP was estimated at 6 to 10 mm Hg; with a <50% inspiratory collapse, RAP was estimated at 10 top 15 mm Hg; and with no collapse, RAP was estimated at >15 mm Hg.
Device Implantation
The Amplatzer secundum ASD closure device and delivery system have been described in detail in previous reports. Devices were implanted in the cardiac catheterization laboratory under fluoroscopy and transesophageal echocardiographic (TEE) or intracardiac echocardiographic (Acuson Sequoia) guidance.
Statistical Analysis
Data were collected and statistically analyzed using SPSS version 16 (SPSS, Inc, Chicago, IL). Numerical variables are expressed as mean ± SD. Means were compared using the unpaired t test. A P value ≤ .05 was considered significant. Receiver operating characteristic curve analysis was used to evaluate the ability of the RAI to detect the presence of an ASD. An optimal cutoff value was chosen that provided the best clinical compromise from the derived sensitivity and specificity.
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