N.B. : CPB – Cardio-Pulmonary Bypass, ACC – Aortic Cross-Clamp, TAP-Trans-annular patch, ASD – Atrial septal defect, RVP/LVP : Post-operative right and left ventricle pressure ratio, PVI-Pulmonary vein Index.
13 ) Prediction of Post-operative Residual Shunts
(A) RV (or PA) systolic pressure (PASP) can be estimated from the velocity of the tricuspid regurgitation (TR) jet, if present, by the following equation:
RVSP (or PASP) = 4 (V)2 + RA pressure where V is the TR jet velocity.
For example,
If the TR velocity is 2.5 m/sec
Then, RVSP or PASP = 4(2.5)2 + RA pressure
= 25 mm Hg + RA pressure
Assuming RA pressure is 10 mm Hg and if no PS
Then, RVSP or PASP = 35 mm Hg.
(B) RV (or PA) systolic pressure can also be estimated from the velocity of the VSD jet by the following equation:
RVSP (or PASP) = Systemic SP (or arm SP) − 4(V)2
where V is the VSD jet.
For example, if the VSD jet flow velocity is 3 m/sec, the instantaneous pressure drop between the LV and RV is 4 × (3)2 = 36 mm. Hg.
RVSP (or PASP) = 36 mm. Hg.
If LVSP is assumed to be 90 mm. Hg., the RVSP is (LVSP-RVSP) = (90 − 36) = 54 mm. Hg.
In the absence of PS, the PASP will be about 54 mm Hg.
(C)LVSP can be estimated from the velocity of flow through the aortic valve (V) by the following equation:
LVSP = 4(V)2 + Systemic SP (or arm SP)
where V is the aortic flow velocity.
N.B. Arm pressure is usually 5 to 10 mm. Hg is higher than the LV systolic pressure.
Significant pulmonary regurgitation (PR) can occur after the repair of TOF. Although the PR has been well tolerated for a decade or two, moderate to severe PR may eventually develop when there is significant RV dilatation and dysfunction. This requires the surgical insertion of a homograft pulmonary valve. RV function is best assessed by MRI 2-D echocardiography.
Surgical Technique -
The operation was performed on our patient with full-flow cardiopulmonary bypass and moderate hypothermia using repeated Del Nido crystalloid cardioplegia under general anesthesia.
Glutaraldehyde treated pericardial patch closure of the ventricular septal defect was performed with the continuous running of 5/0 polypropylene sutures through the right atrial (RA) approach. We then resected the right ventricular outflow tract (RVOT) via trans-atrial and trans-outflow approaches. We reconstructed the PTFE monocusp valve 0.1 membrane of the RVOT. We then employed TAPE augmentation.
Monocusp Preparation
We first measured the circumference of the RVOT from points A to C using black silk marking. A Hegar dilator two sizes larger than required for the patient’s body weight was employed. We used the marked silk threads for width (point A, B, C) and the Hegar dilator to shape the membrane. Finally, we sutured the vertex of the membrane to the native area of the pulmonary valve and both the ends to the width ends of the RVOT using 6-0 polypropylene sutures.
Results
A molecular assay for the qualitative detection of SARS-CoV-2 was performed; the results of which were negative. The patient then underwent a detailed cardiological evaluation, including an electrocardiogram, a 2D echocardiogram, and a cardiac CT dynamic study.
The patient’s PVI was 368.12 mm2/m2, which resulted in a smooth, uneventful postoperative course, with no symptoms of low cardiac output syndrome.
In this study,we evaluated the predictive value of PVI for the determination of early post-operative outcomes among patients with TOF.A reduced PVI is a significant risk factor for both early mortality and prolonged post-operative recovery.
Cardiac CT Dynamic study is a valuable tool that can provide detailed information on the morphology of extra-cardiac vessels,viz.,the coronary vessels,PAs,aorta,and pulmonary and systemic veins.
A secondary objective of this case report was to assess the performance of polytetrafluoroethylene monocusp valves (PTFE-MVs). PTFE-MVs do not calcify in the membrane. Instead, a well-vascularized layer of non-obstructive fibrocollagenous tissue is incorporated into the PTFE with focal areas of endothelialization. The MV integrates with the RVOT patch to variable degrees. Reconstruction of the RVOT with a PTFE-MV has proven a simple, reproducible technique with excellent early postoperative function and minimal PR. Early clinical benefits are seen in patients reconstructed with a monocusp valve compared with those who undergo TAP repairs. Hence, the PVI with PTFE-MV reconstruction of the RVOT is a valuable preoperative predictor of the early prognosis of TOF patients.