Our studies findings demonstrated that for detecting RCT in all patients, TTE had a sensitivity of 48% and specificity of 98%, so it has a likelihood to miss almost 50% potential RCTs. For TEE, the sensitivity and specificity of it can reach a high level, which is 99% and 94% respectively. That means TEE is pretty matched with surgical findings of previous studies [8]. Monin.et al. [7]reported the diagnosis accuracy of RCT confirmed by TTE could reach 90%. Conversely, Alam.et al. [6] reported that RCT was seen in none of 23 patients (sensitivity = 0%). In brief, the reported sensitivity of TTE for detecting RCT has varied considerably. Herein, our study of 6 observational studies, which showed differences in sensitivity of TTE for the diagnosis of RCT that ranged from 0–65%[3, 5, 6, 9–11]. The significant heterogeneity based on I2 for TTE analyses from the Alam in 1991, probably because the sample size is small.
Rupture of mitral chordae tendineae is one of the causes of acute mitral valve regurgitation, which can lead to acute pulmonary edema and cardiogenic shock [12]. It is one of the most common valvular heart diseases, which is secondary to Marfan syndrome, connective tissue disease, coronary heart disease, congenital heart disease, infective endocarditis, rheumatic heart disease and degenerative valvular disease [13]. It often occurs because of the weakness of mitral chordae tendineae, papillary muscles, and abnormal valve position or shape. Primary person refers to the mitral valve leaflet and annular disease caused by degeneration. It is also one of the valvular diseases treated surgically [14]. Early diagnosis of RCT has great significance for treatment, which can save the patient's life. Long-term follow-up shows that patients with RCT and MR are more likely to use valve repair [15]. Valve repair has more advantages than valve replacement, such as lower mortality, higher long-term survival rate, lower risk of thrombus embolism and bleeding, better left ventricular systolic function after the operation. The etiology, lesion location and characteristics of mitral valve prolapse are important factors determining the surgical method, among which, mitral valve posterior lobe prolapse and chordae tendineae ruptures are more suitable for the application of valve repair [16]. Therefore echocardiography it is very significant, in addition to diagnosis, it also needs to understand the location of the diseased lobe and the pathological characteristics of its accessory structure before the operation.
TEE and TTE are important for the diagnosis of RCT [17]. TEE has a better view because the esophagus is closer to the heart, TEE can avoid the interference of thoracic morphology and lung, and the TEE probe has a higher discrimination rate, so it is easier to view the morphology, texture and motor characteristics of the diseased lobe and chordae tendineae [18]. Therefore, the accuracy of TEE in the diagnosis of valvular heart disease is higher than that of TTE [19]. Besides, TEE can have side effects that make patients feel unpleasant as mentioned before, so inspectors should not overuse TEE method to increase the burden on patients. Yu HT et al. [20] did a study in 2013 showed a high prevalence of unrecognized RCT in mitral valve prolapse patients undergoing valve surgery. RCTs were not found in 124 patients, 73 have no RCT observed at surgery, but 51 surgically proved RCT, which means TTE still has a large chance to miss many subtle RCTs even with rapidly developing imaging facilities.
As we have known the typical echocardiography manifestations of mitral valve prolapse and chordae tendineae rupture are the tip of the diseased valve lobe or the chordae tendineae partially ruptured moving back and forth between the atrioventricular in the following cycles [21].The ruptured end of the systolic chordae tendineae was under the lobe of the healthy side and was impacted by the regurgitation tract. Its residual end pointed to the atrial wall or atrial septum of the healthy side, while it returned to the ventricular chamber during diastole [22]. And, when the course of disease gets longer, the calcification of disease change place is heavier; TTE is not easy to detect RCT. Under this situation, TTE it is easier to miss diagnoses.
Combined with our research, we had a finding. Although with the developments in the resolution of TTE over the past 30 years, the sensitivity of TTE to detect RCT has no significant improvement. Complex co-combination of valve conditions occurs with calcification or infectious endocarditis. Maybe TTE has a high sensitivity for the typical signs but not for complicated or untypical signs.
Our study also has several clinical implications. For patients with mitral regurgitation, TTE should be the recommended examination for all patients because of convenient and its high specificity. In these patients, if TTE is highly indicative of RCT, the diagnostic accuracy is high because TTE is highly specific to RCT [23]. Conversely; the absence of valve abnormalities in TTE mostly reduced the likelihood of RCT, so there is no need for TEE. This can eliminate needless hurts that are associated with cost and risk for complication. However, the decision on whether to continue with TEE or not should be determined by the patient's clinical symptoms and doctor. When the valve condition is complex, TTE is difficult to distinguish from the abnormal valve as if due to degenerative mitral valve diseases, vegetation or RCT, TEE should be performed.
This study had several limitations due to potential biases. We included patients that constructed both TTE and TEE could miss many studies that underwent TTE or TEE only.