Early Right Ventricular Function After Repair Of Tetralogy Of Fallot , An Evidence Based Study.

This study aims to assessing right ventricular function early after surgical repair of tetralogy of Fallot and identifying the risk factors associated with development of RV dysfunction.

The shape of the RV is dramatically modified by surgical repair of CHD, with infundibular bulging and apical dilation and deformation, leading to a large range of RV shapes(1,2). Moreover, pericardial section and suture during surgery influence RV geometry, as RV is normally more con-strained by the pericardium then the LV because of its thinner wall (3).

Intra cardiac repair(ICR) is the definitive management of TOF. Refinement in surgical techniques, advancements in anaesthetic \& critical care has resulted in improving survival following ICR. Post operative mortality following ICR is reported between 1% - 5% (3). Post operative low cardiac output and mortality has been attributed to many factors such as anatomical defects with small main pulmonary artery annulus, severe hypoplasia or absent right or left pulmonary artery, ventriculotomy and right ventricular (RV) outflow patch, myocardial hypoxia during cardiopulmonary bypass, or ARDS (4). Certain patients despite satisfactory ICR exhibit difficult post operative course which is characterized by prolonged ventilation \& inotropic support. These patients have been identified to exhibit features of RV dysfunction (low cardiac output, high central venous filling pressure, increased inotropic requirement, and prolonged ventilation). Identification of risk factors to characterise this subset of patients allows for better allocation of hospital resources, improved outcome, and substantially reduced hospital costs. This study will try to identify the risk factors associated with development of RV dysfunction \& its course over a period of three months in patients of tetralogy following ICR.

MRI is a gold standard for assessment of right ventricular function (5). However, MRI has restricted availability, is costly, and there are many patients in whom MRI-non compatible devices prohibit its use.

Because of its complex shape, there is no geometrical assumption that can allow quantification of RV volumes and ejection fraction (RVEF) by standard two-dimensional (2D) echocardiography. For this reason, surrogate parameters of RV systolic function are used most frequently to assess RV systolic function, because they are easy to measure, feasible and reproducible. These parameters include:-

* Tricuspid annulus movement:- Measurements of tricuspid annulus movement by M-mode (tricuspid annular plane systolic excursion \[TAPSE\]) or tissue Doppler imaging (peak systolic velocity \[PSV\]) are used most frequently to assess RV function; they are highly feasible and reproducible. However, several studies have shown their dependence on loading condition; TAPSE and PSV values are increased in volume overload and decreased in pressure overload (6), independent of RVEF.

-2D global longitudinal peak systolic strain of the RV lateral wall:- Speckle-tracking echocardiography is a new technology that allows quantification of myocardial regional deformation. The main advantage compared with tissue Doppler imaging is its angle independency; it was also thought to be less load dependent, but further studies demonstrated that 2D longitudinal strain values increase in volume overload and decrease in barometric overload (7).

- Isovolumic acceleration time(IVA):- Is a quantitative assessment of RV contractile function that is supposed to be unaffected by RV geometry or loading conditions. In patients with tetralogy of Fallot, studies have shown a good correlation between pulmonary regurgitation severity and IVA (8,9).

-Myocardial performance index :- Myocardial performance index (MPI) is another tissue Doppler-derived parameter of RV systolic function. MPI is calculated using the following formula: MPI =(isovolumic contraction time + isovolumic relaxation time)/ejection time (10).

- Fractional area change:- FAC has been shown to correlate well with RVEF measured by MRI in the general population (10).

Eligibility Criteria:
Inclusion Criteria:

1. Pediatric patients up to 12 years old.
2. Recent echocardiography before the surgery giving detailed data about the components congenital anomalies of tetralogy of Fallot and if there are other associated congenital anomalies.
3. Obtaining written informed consent from parents or guardians of all patients confirming their willing and comply with study requirements
4. Parents or guardians of the Patient are willing to comply with all follow-up visits.

Exclusion Criteria:

1. Patients with tetralogy of Fallot who are indicated to palliative procedures and not for definitive surgical repair as in case of:-

   * Neonates with TOF and pulmonary atresia
   * Children with hypoplastic pulmonary artery
   * Age less than 3 months who have medically unmanageable hypoxic spells
   * Infant weight less than 2.5 kg
   * Abnormal coronary artery anatomy
2. Patients with TOF who are contraindicated to primary repair as in case of:-

   * Multiple VSDs
   * Multiple coexisting intracardiac malformations
   * Small pulmonary arteries
   * Very low birth weight
   * The presence of an anomalous coronary artery
3. Patient inaccessible for follow-up visits required by protocol.