In our research, significant TAD decreases were found in 13 patients with severe idiopathic scoliosis, whose scoliotic curves exceeded 80°Cobb. Our results indicated that patients with severe idiopathic scoliosis had RV systolic functional limitations.
Surgery in severe scoliosis means a high risk of not spine dependent complications. To patients with severe scoliosis, surgeons must ensure that their heart function can endure such surgery with its extensive influence on all organs and long procedure time. The larger bloodloss and prolonged pressure on the heart (prone position during surgery) may influence the RV function. If severe RV dysfunction occurred during surgery, tachycardia and hypotension may occur, then even cardiac arrest, which can influence or interrupt surgery, or induce death. So it is very important to assess the complete cardiac function before surgery. By that the scoliosis surgeons can make appropriate decisions by assessing surgical opportunities according to the condition of the cardiac system. For example, will a patient have scoliosis surgery or drug treatment first. In our research centre, doctors who majored in pediatric cardiology, used various kinds of methods for assessing the heart function before surgery, including left and right cardiac function. This paper is a part of our study, which aimed to compare the RV function among various degree scoliotic patients and healthy subjects to determine whether differences exist.
Recently, some papers [8, 9] have reported that patients with idiopathic scoliosis presented cardiorespiratory restrictions, even in patients with mild or moderate scoliosis. But these studies have evaluated the whole functions including lung and heart, and the main aspect was respiratory function. So there is a need to know the exact condition of the heart function in patients with idiopathic scoliosis. If serious RV dysfunction is found, the clinical heart function level, the size of the heart and liver, the respiratory function and the blood level of brain natriuretic peptide (BNP) should be cared first. According to the results, cardiac drugs can be decided using or not. During and after surgery, intensive care of cardiac function is necessary, cardiologists may be called.
Echocardiography is a noninvasive method for assessing cardiac function, which has been widely used in clinical work. In our research centre, every patient with idiopathic scoliosis was examined by echocardiography. Most scoliosis surgeons usually focus on the left ventricular ejection fraction (EF) and fractional shortening (FS), especially to patients with severe scoliosis. Left ventricular EF and FS are two traditional parameters for assessing left ventricular function, which have no relationship with RV function.
The importance of RV function is gradually realized by more and more doctors. Some researchers have found RV dysfunction occurred while left ventricular function was normal in patients with pulmonary hypertension [10, 11]. And due to the connection of the right ventricle with pulmonary artery, the expiratory restriction usually affects the right ventricle more easily, and not so much the left one. Therefore, it is necessary to explore the condition of RV function in patients with scoliosis, which may have expiratory restriction (in our study, we found the results). But precise evaluation of RV function using echocardiography is a hard topic due to the crescent shape and complex morphology of the right ventricle.
Right ventricular ejection fraction (RVEF) measured by magnetic resonance imaging (MRI) is still thought to be the gold standard assessing the RV function. But the longer examining time and the expensive consume restricted the widely used in these patients in our country. In our research, we used improved Simpson’s method to measure RVEF. Results indicated that there were no significant differences among the groups. We think this is because patients with scoliosis have deformities of spine and chest, inducing the abnormalities of cardiac position and morphology. And the RVEF will be more easily affected by the cardiac morphology. So we think this parameter is not suitable for RV function evaluation in patients with idiopathic scoliosis.
It has been certified that the contraction of the right ventricle occurred predominantly along the longitudinal plane . Thus TAD which is the systolic displacement of the tricuspid annulus toward the RV apex, closely correlates with RVEF  measured by MRI. Meanwhile, the measurement of TAD does not require higher equipped echo machine, RV endocardial definition or geometric assumptions. So TAD is thought to be an excellent parameter which is highly reproducible and practical, and can be used widely and conveniently in clinical work.
Some recent studies [14–17] have shown that TAD closely correlated with RVEF in a variety of populations. Sato T  believed that TAD had the best accuracy to assess the RV systolic function in patients with pulmonary hypertension among the echocardiography measurements. In the current study, TAD decreases have been found in patients with severe scoliosis, and our results have indicated that TAD had good negative correlation with severity of the scoliotic curve. So our study shows that RV function impaired in patients with severe scoliosis. You may concern these patients’ clinical heart function evaluation. In our study, these patients didn’t have the signs of exercise tolerance decreased, hepatomegaly, tachypnea, dyspnea, et al. We think TAD is a sensitive parameter, which finding the RV function changes before obvious clinical manifestations. To say in other words, we consider that the RV function of patients with severe scoliosis is in period of compensation, which can be easily influenced. So to these patients, surgeons have to pay attention to the volume and speed of infusion. Too large volume or rapid infusion may lead to RV dysfunction before left ventricle influenced (we have encountered these cases in our work). In our research centre, when we found TAD decreased in patients with scoliosis, we would talk to the surgeons and strengthen patients’ care during and after surgery. In some severe cases, cardiac medical treatment (cardiotonic, diuretics, et al.) may be used.
In our study, PASP evaluating by echocardiography has been compared between scoliotic patients and healthy subjects, and no significant differences have been found. We think patients with scoliosis in our study have not happened pulmonary hypertension, and TAD depression is not due to higher pulmonary pressure. These findings hint that the abnormality of the chest may induce RV dysfunction directly because of the anterior position of the right ventricle.
These results indicate that TAD is a highly sensitive and specific predictor of RV dysfunction in patients with severe idiopathic scoliosis. Thus, TAD should be incorporated into the cardiac functional assessment of patients with idiopathic scoliosis. However, TAD is a simple approach used as the first step assessment of RV systolic function. To patients with depressed TAD, we would perform further evaluation.