3.Discussion
This study aimed at the cases where GNT was diagnosed as myocardial ischemia. After careful examination and combined with electrocardiogram and echocardiography, it was found that the position of the papillary muscle deformity moved down, and the papillary muscles were found to be hypertrophic and branched. Most of the papillary muscles (95%) are attached to the middle third, and only a small portion (5%) is located in the middle and lower third. It was confirmed that the base of the papillary muscle originated in the lower third of the left ventricular cavity, regardless of whether it was complicated with apical hypertrophy. On two-dimensional ultrasound, we found that 2 of them had posterior medial papillary muscles moving down and 2-3 groups of branches appeared, and the corresponding ECG leads showed T wave inversion. Left ventricular angiography clearly shows that the 11 patients in this study not only had papillary muscle hypertrophy, but the position of the papillary muscles moved downward, and some patients had multiple sets of deformities that led to end-systolic occlusion of the left ventricular apex. Studies have shown that papillary muscles have different morphological functions in samples of different types of papillary muscles [12]. These different patterns can be traced back to embryonic development and are related to changes in morphological characteristics of papillary muscles with incompletely differentiated left ventricular trabeculae [13]. In these 11 patients, the four-chamber view clearly showed that the anterolateral papillary muscle hypertrophy was reduced under the left ventricular angiography. The basal base originated from the 1/3 of the left ventricular apex, which was inserted into the anterior mitral valve. There are several branches in science, including 2 cases with posterior medial papillary muscle downward and 2-3 groups of branches, and the corresponding ECG leads have T wave inversion. In this case, if an abnormal T wave inversion occurs on the electrocardiogram, the position and morphological variation of the papillary muscles should be considered. In fact, in the past, on conventional echocardiography, due to poor apical sound transmission, information such as the position of the left ventricular apex and papillary muscles was often ignored. Left ventricular acoustic contrast can help improve the sensitivity of diagnosis, which has good specificity and repeatability. When we find that GNT exists in the 12-lead ECG and consider myocardial ischemia, echocardiography combined with left heart sonography should be used to give a clear diagnosis. This is very important for comparing and differential diagnosis of GNT. In this study, it was shown that the positional displacement and deformed papillary muscles are consistent with the conventional 12-lead ECG T wave inversion site, and the coincidence rate is more than 90%. We believe that it actually causes the negative ventricular extension of the relevant part. Therefore, the origin of abnormal papillary muscle location and papillary muscle morphology can also lead to the occurrence of GNT [14]. Isolated papillary muscle hypertrophy does not belong to the category of hypertrophic cardiomyopathy. In many cases, the two overlap. In the study population, overlaps need to be excluded. Isolated papillary muscle hypertrophy can cause T wave inversion, and an abnormally located papillary muscle with abnormal origin can also cause GNT. Changes in the shape and position of the papillary muscle may cause certain diseases. Some scholars have studied the relationship between papillary muscle morphology and cardiac arrest [15]. Parapapillary muscle and papillary muscle hypertrophy are associated with unexplained sudden cardiac arrest. Therefore, when GNT appears on the ECG, further echocardiography Examination of the chart to confirm the diagnosis is of guiding significance to the clinic. Therefore, when there is unexplained GNT, we need to consider the position of the papillary muscles close to the apex of the heart. Further supportive diagnostic tools can also rely on laboratory data, echocardiography, left ventriculography, coronary angiography, and cardiac CT / MRI analysis Comprehensive analysis of cardiac arrest [16]. The identification of papillary muscles close to the apex and apical hypertrophic cardiomyopathy is also clinically significant. Papillary muscle hypertrophy is the single factor that causes these ECG abnormalities to cause left ventricular wall hypertrophy. Limitations of this study: (1) Selecting patients from the People’s Hospital of China Medical University as the research object may have a certain selection bias due to the regional and economic nature of the disease. (2) This study is a single-center small sample study. But the heart is different from the thyroid or liver, and its individual differences are quite large. Although this study believes that the clinical manifestations of gross deformity of the papillary muscles and lowering of the position show that GNT is not an effective factor for myocardial ischemia, these results require the verification of large multicenter samples. Due to the small sample size, this study did not classify by different pathological types, and whether there are differences in myocardial ischemia of different pathological types during ultrasound examination remains unresolved. (3) In addition, due to the limitations of medical ethics, cardiac examinations cannot perform large sample testing at multiple centers.
This study first confirmed the relationship between the papillary muscle deformity and the inversion t wave and cardiac ischemia. However, in early detection of myocardial ischemia, the significance of applying 12-lead ECG and ultrasound imaging requires further research.