Discussion
From this study, we tested the diagnostic value of 2D, 3D strain and 3D
volumetric analysis in detecting early changes of left ventricular
function in breast cancer patients who was undergoing anthracycline
chemotherapy. In particular, we further assessed and compared the global
and segmental longitudinal strains about the left ventricle derived from
2D strain and 3D strain.
The findings of the study indicated that:
1) on standard 2D echocardiographic
examination, with the cumulative doses of anthracycline increased
2D derived EF decreased gradually
and the E/e’ ratio representing left ventricular diastolic function
increased significantly; 2) on RT-3DE examination, the 3D volumetric
parameters, especially 3D derived EF can detect changes that cannot be
seen by two-dimensional echocardiography in time;
3) on 2D and 3D STE examination, The
subclinical changes of LV longitudinal function can be found in the
early stage of the course of the disease, whether it is the GLS
parameters derived from 2D strain or the GLS parameters derived from the
3D strain. The difference is that 3D-derived GLS earlier, besides, 3D
derived STE all the strain components decreased obviously with the
cumulative doses of anthracycline increased. 4) After anthracycline
chemotherapy, although the decrease degree of peak systolic strain in
each myocardial segment was different, the apical segments were found to
be the most vulnerable.
According
to the time of occurrence, the myocardial damage caused by
anthracyclines can be listed as three categories: acute, chronic,
delayed cardiotoxicity. In most patients, cardiotoxicity can occur
quickly after anthracycline administration, and the damage is obvious
with the extension of time. The chronic and delayed cardiotoxicity of
anthracyclines were positively correlated with their cumulative
dose[22, 23]. Echocardiography and CMR have the advantage of
obtaining information on cardiac structure and function, and both can
avoid radiation exposure. More
convenient and cheaper echocardiography is the first choice for most
patients during monitoring. Monitoring the changes of LVEF is still the
basis for the identification of cardiotoxicity. From this study, we
could find both 2D derived EF, and 3D
derived EF decreased with the
increased doses of anthracycline[24]. And studies have proved that
3D derived EF and CMR have similar accuracy[25].
However,
compared with STE, it is not sensitive to detect early myocardial
damage, because a detectable decrease in EF occurs only after a large
amount of myocardial tissue is lost, and this is consistent with recent
research[26].
Anthracycline-based cardiac toxicity
induced by drugs is characterized by myocardial cell death and
irreversible cardiac injury. Because the affinity of the anthracycline
with myocardial tissue is significantly higher than that of other
tissues, so myocardial tissue is more likely to be damaged. The early
cardiotoxicity is characterized by cardiomyocyte edema and degeneration,
followed by cardiomyocytes myolysis, sarcoplasmic reticulum distortion,
replaced by fibrous tissue, and even cardiomyocyte necrosis, resulting
in heart failure. The basic
structure of myocardium is made up of circumferential fibres in the
mid-wall layer, the endocardial layers and epicardial layers are
composed of longitudinal and oblique muscle fibres[27]. In an
analysis by Crosby et al., researchers found that the absolute values of
the peak strain of ventricular septum contraction in each segment after
myocardial injury were different, and our results also confirmed
this[28]. According to the latest recommended by the American
college of cardiology section 17 section method, the left ventricular
segmental 17 bull ’s-eye map blood supply distribution, the left
anterior item first-just branch (left anterior descending, LAD) supply
basal anterior(BA),basal
anteroseptal(BAS), mid anterior(MA) , mid anteroseptal(MAS), apical
anterior(AA), apical septal(AS) , apex section, right coronary (right
coronary artery, RCA) supply basal
inferoseptal(BIS), basal lateral(BL), mid inferoseptal(MIS), mid
lateral(ML), apical inferior(AI) segment, and the left circumflex branch
(left circumflex artery, LCX) supply
basal inferolateral(BIL), basal
anterolateral(BAL), mid inferolateral(MIL), mid anterolateral(MAL),
apical lateral(AL) segment[29]. From the findings of this study,
most of the descending segments belong to the blood supply region of the
left anterior descending branch, and the trend of the apical segments
were the most obvious. And 3D GLS was detected earlier than 2D GLS,
which is more meaningful for early detection. 3D-STE the motion of echo
spots from three-dimensional space by collecting real-time
three-dimensional images of the heart, so it can evaluate the motion of
the heart more accurately than 2D-STE.