We found that RVRP occurs when patients have lower SP0
2(< 80%), heigher HCT value, transannular patch repair, longer CPB time (> 110 min), longer aortic cross clamping time(> 100 min), lower TAPSE, PASP and TAPSE/PASP ratio and presence of ventricular hypertrophy. In our study male patients predominates in both groups. SP0
2 is determined by cardiac output and the arterial venous oxygen difference, age, sex, muscle mass, genetic endowment, lung function, and efficacy of exercise. Restrictive patients in this study had a lower SP0
2 than non restrictive patients. Any reduction in SP0
2 coincides with a reduction in inventilation capacity. For the restrictive group the mean age was higher than non restrictive group. The sex, age and weight of patients did not show any close relationship as a risk factor of RVRP. The reason behind this is we did not included adult patients in our study so we can’t make a comparison for age and weight [
11]. Some previous studies say that greater the age of patient higher the possibility of RVRP but other researchers contradict it [
12]. In our study and also in some previous studies it has been shown that the repair of transannular patches is an important risk factor for RVRP. We had a total of 6 patients who had TOF with PDA and of these 6 only 3 showed RVRP and 3 without RVRP so the incidence of RVRP was 50% in our study population but as TOF patients with PDA are very few in number we can not conclude that the TOF with PDA is a risk factor for RVRP. In the current study, indexing TAPSE to PASP did significantly strengthen the association between restrictive and non restrictive patients and RV function, suggesting that this simple echocardiography measure can supports further understanding into the severity of physiological evaluation in TOF patients.
Most of the previous articles discuss the mechanism of RVRP the clinical outcome and the echocardiographic characteristics. Some papers deals with the association of RVRP with the myocardial injury and oxidative stress, influence of restrictive physiology on LV diastolic function [
12]. It is very rare to find in previous studies that deal with the etiology of RVRP. Some previous studies found that RVRP appeared more predominant after transannular patch repair [
13,
14]. Norgard et al. also found, by multiple logistic regression analysis that right ventricular restrictive physiology is more likely related to the anatomic substrate requiring a transannular patch repair [
15]. Clark AL and their colleagues also suggest the same that transannular patch repair is main risk factor for restrictive physiology [
16]. In our study it was also found that restrictive physiology is correlated with the repair of transannular patches (76.5%).The reason behind this is the incidence of RV dilatation is higher in patients who had a transannular patch and this makes the right ventricle more susceptible to gradual dilatation as observed by Yetman and colleagues [
3]. Mulla and colleagues reported that restrictive physiology is limited by RV dysfunction not by use of a transannular patch [
3]. However this was contradicted by Mahle and colleagues [
17]. Mulla and colleagues also demonstrated that there is no any association between age of the patient at total correction of TOF and restrictive physiology [
12], but in our study we found that restrictive group had higher mean age than non restrictive group but the
p-value was not significant. In most of the previous studies the patients are adolescents or adults and their age is variable but in our study the age of our patients ranges between 5 months to 10 years and we did not include any adult patient in our study so we can not make any evaluation and conclusion whether the patient’s age and weight is a risk factor. [
18]. Rajiv R Chaturvedi and his colleagues described that acute right ventricular restrictive physiology is associated with greater intraoperative myocardial injury and postoperative oxidative stress with severe iron loading of transferrin, the cause of myocardial injury can be happened due to longer cardiopulmonary bypass(CPB) time and longer duration of aortic cross clamping time [
19]. In our study we also found that patients who have a longer duration of PCB and cross-clamping and more likely to show restrictive physiology. Therefore by minimizing CPB time and cross-clamping we can reduce myocardial injury and reduce the chances of RVRP. Peter Munkhammar and his colleagues described a strong association between the right ventricular restrictive physiology detected on MRI and fibrosis of the RVOT in children after repair of TOF, the link may be that the fibrosis decreases the RV compliance [
20]. In this case, RV with low compliance at atrial systole blood will pumped against a stiff right ventricle, resulting in forward pulmonary flow in ventricular diastole. In our study we also found a close relationship of RVOT fibrosis with RVRP but our technique used to detect fibrosis is echocardiography and we only have 2 patients who undergo an MRI exam before surgery so we exclude RVOT fibrosis of our study.