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.

(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).

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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