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Original Article
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Prompak Nitayavardhanam M.D., Teerapong Tocharoenchok M.D.
Division of Cardiothoracic Surgery, Department of Surgery, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, ailand.
Predictive Value of Right Ventricular Pressure
Measurement for Residual Pulmonary Stenosis in
Tetralogy Repair
ABSTRACT
Objective: e long-term outcome of tetralogy of Fallot repair depends on an adequate relief of right ventricular
outow tract obstruction and preservation of the pulmonary valve function. Since intraoperative transesophageal
echocardiography is not routinely performed in small patients, we postulated that the post-bypass right ventricular
pressure measured intraoperatively could predict residual pulmonary stenosis when evaluated by transthoracic
echocardiography.
Materials and Methods: Of the 187 patients who underwent tetralogy repair between 2012 and 2019 at Siriraj
Hospital, ailand, 95 with right ventricular pressure measurements and pre-discharge echocardiography were
included in the study. eir intraoperative parameters, and postoperative outcomes were analyzed. e tolerable
pressure cuto was determined.
Results: e median patient age was 3.9 years old (interquartile range 2.75–6). Fiy-three patients (54.6%) required
the use of the transannular patch. Ten patients (10.3%) had signicant residual pulmonary stenosis with a mean
right ventricular systolic pressure of 64.0±10.6 mmHg compared with 48.7±14.4 mmHg for the other patients.
ere was an association between the pressure gure and the degree of residual pulmonary stenosis (rho=0.391,
p=0.01). A systolic pressure above 49 mmHg predicted pulmonary stenosis with a likelihood ratio of 2.18 (1.94-
2.80, 95%CI). e likelihood rose to 2.93 (2.44-4.01, 95%CI) if the pressure resulted in a right to le ventricular
pressure ratio above 0.62. e patients whose gures did not exceed 49 mmHg experienced no signicant residual
obstruction, regardless of the pressure ratio.
Conclusion: Intraoperative measurement of the right ventricular pressure can predict residual pulmonary stenosis
aer tetralogy repair with a reassuring cuto of 49 mmHg.
Keywords: Tetralogy of Fallot repair; right ventricular pressure; residual pulmonary stenosis; intraoperative
assessment (Siriraj Med J 2022; 74: 225-232)
Corresponding author: Teerapong Tocharoenchok
E-mail: Teerapong.toc@mahidol.ac.th
Received 26 November 2021 Revised 21 December 2021 Accepted 22 December 2021
ORCID ID: https://orcid.org/0000-0001-9983-3915
http://dx.doi.org/10.33192/Smj.2022.28
INTRODUCTION
Tetralogy of Fallot is the most common cyanotic
congenital heart disease worldwide. e rst corrective
surgery was performed in the 1950s and the treatment
has been evolving ever since.
1
e current strategies
involve adequate relief of right ventricular outow tract
obstruction and optimal preservation of the right ventricular
and pulmonary valve function, guided predominantly
by intraoperative transesophageal echocardiography.
2,3
Residual pulmonary stenosis or regurgitation aer
the repair is not infrequent and, to some extent, it can
lead to progressive right ventricular dysfunction requiring
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subsequent reoperation to prevent sudden cardiac death.
4-6
In the light of a paradigm shi from complete relief of the
right ventricular outow tract obstruction to preserving
the pulmonary valve and infundibulum during tetralogy
repair, the adequacy of resection has gained elevated
importance as some reports have revealed a high incidence
of residual right ventricular outow tract obstruction
following valve-sparing surgery. even during short-term
follow-up.
7
Intraoperative echocardiography is not routinely
performed in small children at many institutes, including
at our institute, and instead, many surgeons measure the
right ventricular pressure intraoperatively to predict the
degree of residual pulmonary stenosis and to identify
whether the problematic outow justies immediate
revision.
8
Unfortunately, the maximum tolerable pressure
is arbitrary and depends on the individual threshold of
acceptance. Besides, the le to the right systolic ventricular
pressure ratio alone is subject to errors as it depends on
the systemic vascular resistance, which may vary across
patients in response to the cardiopulmonary bypass.
We postulate that, in the absence of intraoperative
echocardiography, the right ventricular systolic pressure can
predict residual right ventricular outow tract obstruction.
Further, in this study, we tried to identify the pressure
criteria for outow tract revision.
MATERIALS AND METHODS
Patients
Between 2012 to 2019, 187 consecutive tetralogy
of Fallot patients underwent total correction at Siriraj
Hospital, ailand. Aer exclusion of the patients without
documented post-bypass right ventricular systolic
pressure measurements and pre-discharge transthoracic
echocardiography, 95 patients were included in the study
analysis. e decision to measure the ventricular pressure
primarily depended on the surgeon’s routine. Table 1
shows the baseline characteristic and operative variables
of the study population. e preoperative pulmonary
valve z-value and McGoon ratio were obtained from
the cardiac catheterization measurements. e clinical
outcomes between the 95 included patients were similar
to those of the rest patients (who were excluded because of
no documented intraoperative right ventricular pressure
measurement) concerning signicant residual pulmonary
stenosis and in-hospital care duration (the results not
shown).
e study was approved by Siriraj Institutional
Review Board (COA no. Si 003/2020). e patient consent
is waived as it contained minimal risk to the subject.
TABLE 1. Patient characteristics.
Variables Study patients
(n=95)
Age,y mean±SD 6.0±6.7
median[IQR] 3.9[2.75–6]
Weight,kg mean±SD 15.7±8.7
median[IQR] 13[10.5–17.8]
PreoperativePVz-score -2.14±1.52
McGoonratio 2.21±0.47
Bypasstime,min 165.5±58.7
Cross-clampingtime,min 121.2±39.2
Transannularpatch,n(%) 52(54.7)
DirectRVSP,mmHg 50.3±14.8
DirectPrv/Plvratio 0.60±0.18
PostOpTTERVOTPPG,mmHg 25.2±14.3
missing,n(%) 15(15.8)
PostOpTTEPSgrade,n(%)
none 16(16.8)
mild 69(72.6)
moderate 10(10.5)
severe 0
SignicantresidualPS,n(%) 10(10.5)
ICUstay,d mean±SD 3.2±6.6
median[IQR] 2[1,3]
Hospitalstay,d mean±SD 9.8±7.4
median[IQR] 8[7–11]
Abbreviations: ICU; intensive care unit, Plv; le ventricular pressure,
Prv; right ventricular pressure, PostOp; postoperative, PPG; peak
pressure gradient, PS; pulmonary stenosis, PV; pulmonary valve,
RVOT; right ventricular outow tract, RVSP; right ventricular systolic
pressure, TTE; transthoracic echocardiography.
Surgical technique and right ventricular pressure
measurement
All repairs were conducted through median
sternotomy with cardiopulmonary bypass under mild
systemic hypothermia. Intermittent, antegrade cold blood
cardioplegia was given for myocardial protection. e
surgical approach was transatrial and transpulmonary
and/or transventricular in all the patients depending
on the degree of infundibular hypoplasia and on the
anatomy of the ventricular septal defect. The right
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ventricular outow was managed with either annular-
preserving repair or standard transannular patch repair
with monocusp creation using a 0.1 mm-thick expanded
polytetrauoroethylene membrane according to the
intraoperative annular measurement. e patch size was
tailored for a normal pulmonary valve size for the age
and height of the patient. Aer the patients had come
o the bypass, all the transducers were calibrated, and
the right ventricular pressure was obtained by direct
puncture to the right ventricular free wall using a 25
mm-long, 22-gauge needle connected to the pressure
transducer system. e le ventricular pressure was
simultaneously estimated by the peripheral arterial line
and an arterial outlet pressure monitoring device.
Postoperative course and transthoracic echocardiography
In the intensive care unit, the hemodynamic support
and ventilator management were adjusted according
to the clinical progress by the attending physicians.
Postoperative echocardiography was performed by pediatric
cardiologists before hospital discharge or otherwise as
clinically indicated. e pressure gradient across the
right ventricular outow tract, degree of pulmonary
stenosis, and regurgitation were noted.
Denitions
e degree of residual pulmonary stenosis was
estimated using transthoracic echocardiography by a
combination of the morphologic appearance, and the
measured peak velocity and peak pressure gradient across
the pulmonary valve.
• Mild: peak velocity < 3 m/s, peak gradient < 36
mmHg
• Moderate: peak velocity = 3–4 m/s, peak gradient
= 36–64 mmHg
• Severe: peak velocity > 4 m/s, peak gradient >
64 mmHg
Signicant residual pulmonary stenosis is dened
as a moderate or greater degree of pulmonary stenosis.
Statistical analysis
Based on the expected correlation coecient of 0.3,
a minimum sample size of 85 was required to estimate
Spearman’s rank correlation with a power of 0.8 and a
signicance level of 0.05. Descriptive statistics were used
to present the baseline characteristics of the patients.
Continuous variables were presented as the mean with the
standard deviation or the median with the interquartile
range. e dierences were evaluated using the Student’s
t-test or Mann–Whitney U test, as appropriate. Categorical
variables were presented as number and percentage, and
dierences were evaluated using the chi-square test or
Fischer’s exact test, as appropriate. A p-value < 0.05 was
set as the threshold for statistical signicance. Receiver
operating characteristic (ROC) curves were generated
to determine the optimal cuto values for the variables
in the prediction of signicant residual outow tract
obstruction. All the data were analyzed using the SPSS™
soware version 20.0 (SPSS Inc., IBM Company, Chicago,
Illinois, USA).
RESULTS
No operative mortality was observed. e pre-
discharge transthoracic echocardiography was performed
at the median post-operative day 5 (interquartile range
1-6). e mean intraoperative right ventricular systolic
pressure aer the repair was 50.3±14.8 mmHg (range
17–83 mmHg). e mean intraoperative right to le
systolic ventricular pressure ratio was 0.60±0.18 (range
0.21–1.08). Concerning the degrees of postoperative
tricuspid regurgitation, only 5 patients experienced
moderate tricuspid regurgitation while the rest had
no or mild regurgitation. Table 2 shows comparisons
between the two surgical approaches: the transannular
and non-transannular techniques. e transannular
patch repair group was associated with less residual
outow obstruction, more pulmonary regurgitation,
and a longer ICU stay and hospital stay.
Ten patients (10.5%) were documented to have
significant residual right ventricular outflow tract
obstruction with a higher systolic right ventricular
pressure and pressure ratio. None of them underwent
surgical revision at the index admission. Comparisons
between the patients with and without signicant residual
pulmonary stenosis are shown in Table 3. e patients
with residual subpulmonary obstruction required less
transannular patching and subsequently a shorter in-
hospital care duration. e characteristics of the patients
with signicant residual pulmonary stenosis are shown
in Table 4.
rough Spearman’s rank correlation analysis, we
found a correlation between the systolic right ventricular
pressure and the degree of postoperative residual pulmonary
stenosis (rho = 0.391; p = 0.01). e right to le systolic
ventricular pressure ratio was also correlated with the
degree of postoperative residual pulmonary stenosis
(rho = 0.369; p = 0.01). rough ROC curve analysis,
we analyzed each intraoperative pressure parameter and
the combination of both to identify the diagnostic cuto
for signicant residual pulmonary stenosis identied
by pre-discharge transthoracic echocardiography. e
results are depicted in Fig 1. A systolic right ventricular
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TABLE 2. Comparison of two outow reconstruction techniques among the study patients.
Variables Transannular approach Transatrial/Pulmonary P-value
(n=52) (n=43)
Age,y mean±SD 5.1±4.9 7.1±8.3 0.15
median[IQR] 3.4[2.8–6.2] 4.8[2.8–6.0] 0.43
Weight,kg mean±SD 14.5±6.9 17.1±10.5 0.16
median[IQR] 12.2[10.4–16.3] 14[10.5–18.5] 0.27
PreoperativePVz-score -2.82±1.47 -1.30±1.14 <0.001
McGoonratio 2.21±0.47 2.27±0.59 0.58
Bypasstime,min 176.1±68.5 148.7±40.1 0.022
Cross-clamping,min 129.5±42.3 108.4±32 0.007
DirectRVSP,mmHg 52±15 48.5±14.7 0.26
DirectPrv/Plvratio 0.62±0.19 0.58±0.18 0.26
PostOpTTEPSgrade,n(%) 0.46
none 8(15.4) 7(16.3)
mild 41(76.9) 27(62.8)
moderate 2(3.8) 8(18.6)
severe 0 0
SignicantresidualPS,n(%) 2(3.8) 8(18.6) 0.039
PostOpTTEPRgrade,n(%) <0.001
none 0 7(16.3)
mild 4(7.7) 10(23.3)
moderate 20(38.5) 21(48.8)
severe 27(51.9) 4(9.3)
PostOpTTERVOTPPG,mmHg 24.4±13.9 25.6±13.5 0.72
missing,n(%) 9(17.3) 7(16.3)
ISatICUarrival mean±SD 11.3±12.7 8.2±6.2 0.15
median[IQR] 7.5[5–15] 7[4–13] 0.38
ICUstay,d mean±SD 4.3±8.8 2±1.5 0.09
median[IQR] 2.5[1–4] 1[1–2] 0.006
Hospitalstay,d mean±SD 11.5±10 8.1±2.7 0.032
median[IQR] 10[7–11.8] 8[6–10] 0.007
Abbreviations: ICU; intensive care unit, IS; inotropic score, Plv; le ventricular pressure, Prv; right ventricular pressure, PostOp; postoperative,
PPG; peak pressure gradient, PR; pulmonary regurgitation, PS; pulmonary stenosis, PV; pulmonary valve, RVOT; right ventricular outow
tract, RVSP; right ventricular systolic pressure, TTE; transthoracic echocardiography.
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TABLE 3. Comparison of two outow reconstruction techniques among the study patients.
Variables Patients with Patients without P-value
signicantresidualPS signicantresidualPS
(n=10) (n=85)
Age,y mean±SD 3.8±2.0 6.3±7.0 0.019
median[IQR] 3.3[2.3–5.3] 4.3[2.8–6.3] 0.31
Weight,kg mean±SD 14.2±5.0 15.9±9.1 0.39
median[IQR] 13.3[10–17.6] 13[10.6–17.8] 0.85
PreoperativePVz-score -1.59±0.74 -2.21±1.58 0.22
McGoonratio 2.58±0.57 2.17±0.44 0.05
Bypasstime,min 144±24.9 168±61 0.028
Cross-clampingtime,min 109.6±29.5 122.6±40.1 0.23
Transannularpatch,n(%) 2(20) 49(57.6) 0.039
DirectRVSP,mmHg 64±10.6 48.7±14.5 0.001
DirectPrv/Plvratio 0.76±0.13 0.58±0.18 0.002
PostOpTTERVOTPPG,mmHg 46.7±10.2 21.8±10.9 <0.001
missing,n(%) 0 14(16.5)
ISatICUarrival mean±SD 8.6±6.9 9.9±10.7 0.60
median[IQR] 7[4–11.3] 6.8[4.4–15] 0.89
ICUstay,d mean±SD 1.7±1.9 3.5±6.9 0.07
median[IQR] 1[1–1.3] 2[1–3] 0.018
Hospitalstay,d mean±SD 7.7±1.8 9.3±3.6 0.042
median[IQR] 7[6.8–8.5] 8[7–11] 0.27
Abbreviations: ICU; intensive care unit, IS; inotropic score, Plv; le ventricular pressure, Prv; right ventricular pressure, PostOp; postoperative,
PPG; peak pressure gradient, PS; pulmonary stenosis, PV; pulmonary valve, RVOT; right ventricular outow tract, RVSP; right ventricular
systolic pressure, TTE; transthoracic echocardiography.
pressure above 49 mmHg predicted postoperative
residual pulmonary stenosis with a likelihood ratio of
2.18 (95%CI 1.94–2.80). A systolic right to le ventricular
pressure ratio above 0.62 predicted postoperative residual
pulmonary stenosis with a likelihood ratio of 2.57 (95%CI
2.21–3.42). e combination of both pressure criteria
raised the likelihood of residual outow obstruction to
2.93 (95%CI 2.44–4.01). Fig 2 shows the outow tract
decision owchart according to our results. None of the
study patients whose ventricular pressure did not meet
both criteria experienced signicant residual outow
obstruction.
DISCUSSION
We found an association between right ventricular
systolic pressure and the degree of pulmonary stenosis.
As a predictor for residual right ventricular outow tract
obstruction, the absolute gure of the intraoperative
pressure performed comparably to the pressure ratio
(an almost identical area under the ROC curve). When
we combined both parameters, the predictive value from
the likelihood ratio increased considerably. Apart from
the pressure ratio, this information implies how high the
right ventricular pressure is also matters, especially when
the right to le systolic pressure ratio approaches the
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TABLE 4. Characteristics of the patients with signicant residual pulmonary stenosis.
Patient Gender Preoperative McGoon Technique RVSP, Prv/lv PostOp TTE IS at ICU ICU stay, Hospital
PV z-score ratio mmHg ratio RVOT PPG, arrival day stay, day
mmHg
1 M -2.06 2.73 Subannular, valvulotomy 52 0.66 39 4 1 6
2 F -1.5 2.3 Subannular, valvulotomy 50 0.63 49 15 2 6
3 M -1.18 3.5 Supravalve, valvulotomy 69 0.69 47 11.7 8 12
4 F -2.6 3 Transannular, monocusp 67 0.76 55 20 4 10
5 M -1.9 2.5 Supravalve, valvulotomy 64 0.75 42 7 1 8
6 M -1.63 1.5 Sub/supravalve patch, 50 0.70 38 5 1 8
valvulotomy
7 M -2.4 2 Supravalve, valvulotomy 81 0.70 55 10 1 7
8 F -1.79 3.12 Transannular, monocusp 75 0.90 66 7.5 1 7
9 M -0.4 2.53 Supravalve, valvulotomy 70 1.08 41 5 1 8
10 M -0.4 2.6 Transatrial 62 0.73 44 10 1 7
Abbreviations: ICU; intensive care unit, IS; inotropic score, Plv; le ventricular pressure, Prv; right ventricular pressure, PostOp; postoperative, PPG; peak pressure gradient, PV; pulmonary valve, RVOT;
right ventricular outow tract, RVSP; right ventricular systolic pressure, TTE; transthoracic
Echocardiography.
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Fig 2. Outow tract assessment decision owchart
Abbreviations: Prv/lv; right ventricular to le ventricular systolic pressure ratio, PS; pulmonary stenosis, RV; right ventricle, RVSP; right
ventricular systolic pressure.
Fig 1. Receiver operating characteristic (ROC) curves of the predictors of right ventricular outow tract obstruction. (A) Right ventricular
systolic pressure (RVSP). (B) Right to le ventricular pressure ratio (Prv/Plv ratio).
Abbreviations: AUC; area under the curve, Sn; sensitivity, Sp; specicity.
published revision criteria. Although in the majority of
the cases both the pressure and pressure ratio went in the
same direction and magnitude, in some patients with a
relatively low systolic blood pressure initially o the pump,
use of the pressure ratio alone tended to overestimate
the residual outow obstruction. Only one of the sixteen
patients (specically, patient #9) with an initial systolic
blood pressure below 70 mmHg experienced signicant
residual pulmonary stenosis despite a mean pressure ratio
of 0.75±0.29 in the group with hypotension. Adding the
absolute right ventricular pressure to the consideration
could prevent unnecessary intervention in this context.
To the best of our knowledge, this piece of information
has not been reported before in the literature.
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Regarding the pressure ratio cuto value of 0.62,
which is quite low compared with other reports
2,9
, this
gure was selected as a reassuring cuto, not the revision
one. As the specicity of the test suggested, some patients
whose measurement exceeded these criteria eventually
fell into the insignicant residual outow stenosis at the
sonographic follow-up. is implies that even if both
proposed criteria are met, the surgeon should logically
identify the culprit location and consider the possibility of
further resection without scarifying the pulmonary valve
integrity before commencing the second pump run. e
reason behind this is possibly due to the heterogeneous
nature of postoperative Fallot’s outow tract restriction
(i.e., xed or dynamic)
10
, which, unfortunately, might
need intraoperative echocardiography to dierentiate.
3
Unsurprisingly, the patients who needed the pulmonary
valve ring enlarged performed worse than those with an
intact pulmonary valve ring in terms of the pulmonary
valve integrity and in-hospital care duration (Table 2).
In contrast to a previous report
8
, our study demonstrated
better in-hospital outcomes among the patients with
signicant residual outow tract obstruction (shorter
ICU and hospital stay). is result could probably be
attributed to the eect of the transannular approach and
the resultant pulmonary insuciency rather than the
gradient itself (the transannular patching requirement
of the patients with insignificant residual stenosis
was almost triple that of the signicant counterpart,
Table 3).
It is to be noted that our study had limitations due
to its retrospective nature and short period of follow-up.
Also, changes in the outow tract gradient over time
were monitored only in selected patients. Furthermore,
as we did not have a patient with critical residual outow
tract obstruction in our series, the diagnostic cuto of
such a condition was, therefore, unattainable. Longer-
term follow-up of such a ‘signicant’ patient is needed
to elucidate the clinical signicance of such ndings.
CONCLUSION
In the setting without intraoperative transesophageal
echocardiography, the direct measurement of right
ventricular pressure can predict the adequacy of outow
tract reconstruction during the repair of tetralogy patients.
Adding an absolute pressure criterion of 49 mmHg to
the pressure ratio could prevent unnecessary surgical
revision and protect pulmonary valve integrity.
ACKNOWLEDGEMENTS
We acknowledge the contribution of Dr. Sasima
Tongsai from the Clinical Epidemiology Unit, who
performed the statistical analysis for this study.
Funding statement: is research received no specic
grant from any funding agency.
Conict of interest statement: None declared.
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