Annular Tilt as a Screening Test for Right Ventricular Enlargement in Patients with Tetralogy of Fallot




Background


Right ventricular end-diastolic volume (RVEDV) greater than 150 mL/m 2 is a risk factor for sudden death in patients with tetralogy of Fallot (TOF) after repair. Because of its anterior placement and abnormal geometry, two-dimensional echocardiography is limited to a qualitative assessment of RVEDV. Cardiac magnetic resonance imaging (CMRI) and computed tomography angiography (CTA) are the accepted standards for quantifying RVEDV. This study evaluated the ability of a novel echocardiographic measure, the right ventricular annular tilt (RVAT), to identify patients with increased RVEDV.


Methods


All patients with repaired TOF with an echocardiogram and CMRI or CTA were included in this retrospective study. The RVAT was determined by measuring the angle of the tricuspid valve plane relative to the mitral valve plane at end-diastole in the apical 4-chamber view in study ( n = 38) and age-matched control ( n = 74) patients. The RVEDV measurements were obtained by CMRI ( n = 32) or CTA ( n = 6). The study and control patients’ ages were no different (11.3 and 11.8 years, P = .73).


Results


The study group RVAT was significantly higher than the control group RVAT (17.4 vs. 0.1 degrees; P < .0001). RVAT values greater than 20 degrees had a mean RVEDV of 166 ± 60 mL/m 2 , whereas RVAT less than 20 degrees had a mean RVEDV of 122 ± 25 mL/m 2 ( P = .0370). Receiver operating characteristic analysis demonstrated an RVAT of 17.9 degrees as the cutoff for predicting a RVEDV of greater than 150 mL/m 2 with a sensitivity of 75% and specificity of 73% (area under the curve = 0.76; confidence interval, 0.56-0.96; P = .0063). Intraclass correlation analysis demonstrated minimal interobserver and intraobserver variability when measuring RVAT (0.99 and 0.92).


Conclusion


An RVAT less than 20 degrees is associated with an RVEDV less than 150 mL/m 2 . RVAT is a useful echocardiographic technique for detecting increased RVEDV in patients with TOF and may help discern which patients should undergo RVEDV quantification by CMRI or CTA.


Right ventricular enlargement is an important risk factor for ventricular arrhythmias, right ventricular failure, and sudden death in patients with repaired tetralogy of Fallot (TOF). These patients typically have pulmonary regurgitation as a result of a transannular patch repair or an incompetent right ventricular to pulmonary artery conduit that leads to right ventricular enlargement. Pulmonary valve replacement can minimize right ventricular enlargement progression and potentially reverse the right ventricular size through remodeling, which is still possible when the right ventricular end-diastolic volume (RVEDV) is 150 mL/m 2 . Because of its anterior placement and abnormal geometry, two-dimensional echocardiography is limited to a qualitative assessment of RVEDV. Cardiac magnetic resonance imaging (CMRI) and computed tomography angiography (CTA) are the accepted standards for quantifying RVEDV. This study evaluated the ability of a novel echocardiographic measure, the right ventricular annular tilt (RVAT), to identify patients with increased RVEDV.


Materials and Methods


Patient Population


All patients with repaired TOF who had both an echocardiogram and a CMRI/CTA study at the Lucile Packard Children’s Hospital Heart Center between January 1, 2001, and November 30, 2009, were initially selected for this retrospective study. Patients who had a time interval of more than 6 months between echocardiogram and CMRI/CTA were excluded from further evaluation. In addition, any patient with an associated atrioventricular canal repair was also excluded because both atrioventricular valves were at the same level, and this may affect the RVAT. Age and body surface area-matched controls were selected by querying the database for patients without structural heart disease or cardiac dysfunction. Approximately double the number of study patients were selected as controls. Each patient’s body surface area using the Mosteller formula; gender, date of birth, date of death, and type of prior surgical intervention were obtained from patients’ electronic medical records. This study was approved by the Stanford University Institutional Review Board.


Echocardiogram Data


The ultrasound equipment used for the echocardiographic studies was the Siemens Sequoia C512, rev 12.0 (Siemens Medical Solutions USA, Inc., Mountain View, CA) or the Phillips IE33 (Philips Medical Systems, Bothell, WA). All offline measurements were made using syngo Dynamics workstation (Siemens Medical Solutions USA, Inc, syngo Dynamics Solutions, Ann Arbor, MI). The data were collected from the apical four-chamber view. The RVAT was measured at end-diastole, when the tricuspid valve leaflets coapt, by drawing two lines: 1) The baseline is drawn from the mitral valve annular insertion at the interventricular septum to the mitral valve annular insertion at the posterolateral wall; and 2) the line of the angle is drawn from the tricuspid valve annular insertion at the anterolateral wall to the interventricular septum, to connect with the baseline at the interventricular septum ( Figure 1 ). The RVAT was obtained from the four-chamber view. Because this measurement only depends on the angle between the tricuspid and mitral valve from the apical window, this view was considered acceptable if both atrioventricular valves were well seen in their entirety, and the image was obtained from an apical window.




Figure 1


(A) Apical four-chamber view of a control patient without congenital heart disease obtained at end-diastole. A line is drawn from the mitral valve plane at its hinge points ( white ). A second line is drawn from the tricuspid valve free wall hinge point to the interventricular septum at the initial lines bisecting point ( yellow ). This control patient’s RVAT measures negative 4.5 degrees. (B) Study patient with the same RVAT technique that measures positive 34.8 degrees. LA, Left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle.


The RVAT was obtained on all study and control patients. Given that the tricuspid valve is lower than the mitral valve in normal patients, some angles less than 0 degrees were anticipated in the control group. When available, each subject had three RVAT measurements from separate echocardiogram clips in the control and study group by one observer; these values were then averaged. The echocardiogram clip and frame number were recorded for each RVAT for reference. An independent reader also measured a subset of 10 studies within each patient group, blinded to the primary readers’ results using the same recorded clip and frame number. An additional 20 patients without structural heart disease or cardiac dysfunction were prospectively analyzed to ensure there was no respiratory variability when deriving an RVAT. The measurement was obtained at end-inspiration and end-expiration.


In addition to RVAT, other echocardiographic measurements in the study patients included the degree of tricuspid/pulmonary regurgitation, right ventricular outflow tract obstruction, and right atrial enlargement. A qualitative grade of pulmonary regurgitation was assigned by determining the width of the regurgitant jet compared with the right ventricular outflow tract diameter, the presence of flow reversal in the branch pulmonary arteries, and the pulmonary regurgitation deceleration time. The pulmonary regurgitation index by M-mode echocardiography was not assessed because M-mode through the right pulmonary artery was not performed. The degree of tricuspid valve regurgitation was determined by examining the vena contracta, and right atrial enlargement was assessed subjectively. Study patients were grouped into two groups according to right atrial size, moderate or greater right atrial enlargement, and mild or no right atrial enlargement. The RVAT was compared between these groups. The images were reviewed by two of the authors (TT/RP), and a consensus grade was obtained for all the study patients. Continuous-wave Doppler was used to assess the degree of right ventricular outflow tract obstruction; velocities were anticipated to be higher in all patients given the expected pulmonary regurgitant volume.


Statistics


Parametric testing was used to compare data with normal distributions, such as age, RVAT, and RVEDV. All comparisons of RVAT and ages were performed with the Student t test, and the paired t test was used to compare the RVAT at end-inspiration and end-expiration. Intraclass correlation coefficients were establish for interobserver and intraobserver variability analysis for the patients with three RVAT measurements. Nominal data were compared using the chi-square test. Receiver operating characteristic (ROC) curve analysis was used to determine the cutoff for predicting a right ventricular volume of 150 mL/m 2 . A P value of less than .05 was considered statistically significant. All statistical calculations were performed using the SAS Enterprise Guide version 4.2 (SAS Institute Inc, Cary, NC) and Microsoft Excel (Redmond, WA).




Results


Patient Population


Thirty-eight patients were included in the study, of whom 32 had CMRI studies. The remaining six patients had CTA studies ( Table 1 ). All of these patients had echocardiograms performed within an average of 67 ± 121 days of the CMRI or CTA study. Seventy-four age-matched controls were included. There was no difference in mean age (study mean age 11.3 ± 11.0 years, control mean age 11.8 ± 4.8 years; P = .73) or patient size (study mean size 1.3 ± 0.7 m 2 , control mean size 1.3 ± 0.5 m 2 ; P = .98) between study and control groups ( Table 2 ). Fifty-seven percent of the control patients were male, and 37% of the study group were male ( P = .0725). The RVAT among male and female patients in the study group was 17.9 ± 11.9 degrees and 16.5 ± 8.0 degrees, respectively ( P = .6818). The control group RVAT had a small difference of 2.9 degrees that did not quite achieve statistical significance (female = −0.8 ± 7.5 degrees vs males 2.1 ± 5.23 degrees, P = .07).



Table 1

Patients with tetralogy of Fallot included in the study



















































































































































































































































































































































































































































































































































































































Demographic data MRI/CT-derived data Echocardiogram-derived data
Pt Diagnosis Age y Prior intervention Mode RV EDV mL/m 2 RV ESV mL/m 2 RV EF % PR % Avg RVAT TR PR RAE ECG QRSD ms
1 TOF 11 RV-PA conduit MRI 123.4 55.9 54.6 14.0 21.0 trace mild none 129
2 TOF/PA 10 RV-PA conduit MRI 201.9 153.9 23.8 NA 25.9 mild-mod trace mod NA
3 TOF/PA 3 RV-PA conduit MRI 124.0 75.0 40.0 25.0 0.0 trace mod none NA
4 TOF 4 TAP repair MRI 94.7 54.9 42.1 25.0 6.9 trace moderate none NA
5 TOF 4 TAP repair MRI 98.4 33.8 65.7 16.0 33.9 trace severe mild 116
6 TOF 7 TAP repair MRI 155.0 88.0 43.0 37.0 12.4 trace moderate-severe none 91
7 TOF 10 TAP repair MRI 108.0 59.0 45.4 43.0 0.0 mild severe none 137
8 TOF 11 RV-PA conduit MRI 116.1 67.1 42.3 14.0 15.7 mild mild none 161
9 TOF/PA/MAP 14 RV-PA conduit MRI 144.2 103.0 28.5 NA 23.3 mild mild-moderate none NA
10 TOF 10 RV-PA conduit MRI 138.0 71.6 48.1 25.0 14.5 mild-mod mild-moderate mild NA
11 TOF/PA 2 RV-PA conduit MRI 100.0 36.6 63.3 34.0 9.8 mild severe none 88
12 TOF 7 TAP repair MRI 124.4 55.2 55.6 34.0 13.1 mild-mod severe none 83
13 TOF 4 TAP repair MRI 137.2 63.9 53.4 33.0 10.2 trace severe mild NA
14 TOF 13 TAP repair MRI 207.9 97.9 52.9 68.0 12.8 mild moderate mild-mod NA
15 TOF 3 TAP repair MRI 138.0 68.0 51.0 39.0 29.7 mild moderate-severe mild NA
16 TOF 14 TAP repair MRI 144.0 77.0 46.5 64.0 13.6 trace none none 139
17 TOF 2 Valve-sparing MRI 79.0 39.5 50.0 23.0 15.9 trace mod mild 115
18 TOF 10 TAP repair MRI 128.0 69.0 46.0 49.0 10.9 trace severe mild 155
19 TOF 3 TAP repair MRI 98.7 60.6 38.6 NA 7.5 mild severe mild NA
20 TOF 11 TAP repair MRI 96.8 54.0 44.3 29.0 19.8 mild moderate none 130
21 TOF 5 TAP repair MRI 137.6 72.2 47.5 34.0 17.8 trace moderate-severe none 113
22 TOF/PA 3 RV-PA conduit MRI 94.9 46.3 51.2 31.0 22.0 trace severe mild 146
23 TOF 15 TAP repair MRI 300.0 201.7 33.0 77.0 28.7 trace severe mild 173
24 TOF/PA 1 RV-PA conduit MRI 112.1 64.9 42.1 23.0 19.2 trace severe mod 67
25 TOF 2 TAP repair MRI 92.7 45.4 51.0 29.0 7.6 trace severe none 105
26 TOF 13 TAP repair MRI 115.5 57.7 50.2 20.0 7.9 mild mild mild NA
27 TOF 3 RV-PA conduit MRI 149.0 103.0 31.0 27.0 13.6 trace mild mild 128
28 TOF/PA/MAP 2 RV-PA conduit MRI 98.7 56.9 42.3 31.0 14.1 trace mild none 125
29 TOF 10 TAP repair MRI 172.0 102.3 40.5 46.0 17.9 trace severe none NA
30 TOF 9 RV-PA conduit MRI 183.0 123.4 32.6 35.0 57.9 mod severe mild NA
31 TOF 10 TAP repair MRI 146.0 64.0 56.0 47.0 14.1 trace severe mild NA
32 TOF 10 TAP repair MRI 134.9 77.7 42.0 30.0 28.5 trace moderate-severe none 120
33 TOF 16 TAP repair CTA 184.0 85.0 54.0 NA 13.5 trace moderate-severe mild 201
34 TOF 16 RV-PA conduit CTA 196.2 153.5 21.8 NA 34.8 mild-mod mild mild 169
35 TOF 38 RV-PA conduit CTA 107.2 62.2 42.0 NA 17.5 mild mild mild 138
36 TOF 37 RV-PA conduit CTA 100.2 52.4 47.8 NA 16.7 mild mild mild 155
37 TOF 37 RV-PA conduit CTA 112.6 56.9 49.4 NA 16.2 mild mild mild 157
38 TOF 48 TAP repair CTA 132.2 76.1 42.4 NA 8.8 none severe moderate 168

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Jun 16, 2018 | Posted by in CARDIOLOGY | Comments Off on Annular Tilt as a Screening Test for Right Ventricular Enlargement in Patients with Tetralogy of Fallot
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