A total of 240 patients who were referred to the cardiology department for pre-chemotherapy fitness were screened and found to be eligible. Of them, 32 patients were excluded, and another 48 patients were lost to follow-up. Hence, a total of 160 patients completed the study and were used for this analysis. There were 29 patients (18.1%) who were TnI + and 106 patients (81.9%) were TnI- (Fig. 2). Baseline characteristics (Table 1) were comparable between the two groups. The mean age in both groups was similar, 52.8 (50.7, 54.8) in TnI- group and 51.5 (47.4, 55.5) in TnI + group, p = 0.59. Breast cancer accounted for more than 3/4th of all cancers in both groups, and expectedly, females predominated the study population accounting for 86.3% of TnI- group and 93.1% of TnI + group. Other malignancies encountered in the remainder included bladder cancer, Hodgkin's lymphoma, Non-Hodgkin's lymphoma, sarcoma, and stomach cancer. The risk factors considered were hypertension, diabetes, and previous myocardial infarction, and none of them showed a difference between groups. Baseline ECG parameters were also comparable between groups (Table 2).
Table 1
Comparison of baseline categorical variables between Troponin I negative and positive groups
Variable
|
Subgroups
|
% in Troponin Negative
|
% in Troponin Positive
|
p value
|
Gender
|
Male
|
13.7
|
6.9
|
0.53
|
Female
|
86.3
|
93.1
|
Malignancy
|
Bladder
|
0.8
|
0
|
0.7
|
Breast
|
78.6
|
82.8
|
Hodgkin's lymphoma
|
2.3
|
0
|
Non-Hodgkin's lymphoma
|
5.3
|
10.3
|
Sarcoma
|
4.6
|
6.9
|
Stomach
|
6.9
|
0
|
Others
|
0.8
|
0
|
Hypertension
|
Yes
|
30.5
|
27.7
|
0.75
|
No
|
69.5
|
72.4
|
Diabetes
|
Yes
|
16
|
17.2
|
0.53
|
No
|
84
|
82.8
|
Myocardial infarction
|
Yes
|
2.3
|
3.4
|
0.55
|
No
|
97.7
|
96.6
|
Table 2
Comparison of baseline characteristics between Troponin I negative and positive groups
|
Troponin Negative
|
Troponin Positive
|
|
Parameter
|
Mean
|
95% CI
|
Mean
|
95% CI
|
p value
|
Age
|
52.8
|
50.7, 54.8
|
51.5
|
47.4, 55.5
|
0.59
|
QT
|
352.8
|
347, 358.6
|
340.7
|
329.5, 351.9
|
0.08
|
HR
|
88
|
85.3, 90.6
|
93.6
|
88.2, 98.9
|
0.07
|
QTcH
|
401.7
|
398, 405.4
|
399.4
|
393, 405.8
|
0.60
|
TP
|
204.2
|
185.7, 223.2
|
170.3
|
137.4, 203.3
|
0.12
|
TP/QT
|
0.56
|
0.52, 0.61
|
0.49
|
0.40, 0.58
|
0.16
|
PQ
|
152.5
|
147.3, 157.7
|
143.5
|
133, 153.9
|
0.14
|
PQ/QT
|
0.44
|
0.42, 0.45
|
0.43
|
0.39, 0.46
|
0.59
|
Post-chemotherapy ECG showed a statistically significant difference in three variables between groups (Table 3). Heart rate, TP, and TP/QT had a significant difference in means. Other parameters (QT, QTcH, PQ, and PQ/QT) were not different between groups. Mean HR in TnI- groups was 97.2 (94.3, 100) and in TnI + group was 106.4 (99.8, 113.1), p < 0.01. Mean TP segment in TnI- group was 162.9 (145.4, 180.4) and in TnI + group was 117.9 (89, 146.8), p = 0.03 and TP/QT in the respective groups were 0.47 (0.42, 0.51) and 0.35 (0.27, 0.42), p = 0.02.
Table 3. Comparison of post-chemotherapy ECG characteristics between Troponin I negative and positive groups
Change in the baseline values of ECG parameters after chemotherapy were assessed using paired samples t-test. All parameters except HR and PQ/QT showed a statistically significant change from baseline (Table 4). Mean difference of QT in TnI- group was 11.5 (5.7, 17.2; p < 0.01), HR was − 9.2 (-11.8, -6.7, p < 0.01), TP was 41.5 (26.4, 56.7, p < 0.01), TP/QT was 0.1 (0.06, 0.14, p < 0.01) and PQ was 6.6 (0.9, 12.2, p = 0.02). In the TnI + group, mean HR difference was − 12.9 (-18.9, -6.8, p < 0.01), QTcH was − 14.2 (-25.3, -3.1, p < 0.01), TP was 52.4 (19.5, 85.4, p < 0.01) and TP/QT was 0.14 (0.05, 0.23, p < 0.01). QT, PQ, and PQ/QT did not show a significant change in mean. Difference scores of all the ECG parameters were also calculated and compared between groups to see if this change in parameters was significant. To calculate the difference-scores, post-chemotherapy scores were subtracted from the baseline scores, and independent samples t-test was performed. It did not show a statistically significant difference in any of the measured variables (Table 4). Multivariate analysis was performed on ECG variables QTcH, TP, TP/QT, and PQ, and none of the variables showed a significant association with positive Troponin test.
Table 4. Change in ECG parameters from baseline to post-chemo in Troponin negative and positive groups
There was a linear correlation between HR, TP, TP/QT, and Troponin I values. However, when Pearson's partial correlation was run for controlling HR as a confounder, the relationship of both TP and TP/QT with Troponin I ceased to be statistically significant (p = 0.35).