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.