3.1 Among the 261 patients with acute anterior wall STEMI, 15.3% (40/261) presented with new onset CRBBB. The CRBBB group exhibited a significantly older patient population compared to the no-CRBBB cohort (P=0.001). Admission Killip class was predominantly class I-II in the no-CRBBB group, while it was majority of class III-IV in the CRBBB group (P<0.001). Although the CRBBB group exhibited lower admission blood pressure and higher heart rate compared to the no-CRBBB group, these differences were not statistically significant (P>0.05). No significant differences were found between the two groups regarding history of hypertension, diabetes, hyperlipidemia, coronary heart disease, chronic kidney disease, cerebrovascular disease, gout, gender, family history of cardiovascular disease, smoking, alcohol use, or PCI modality (P>0.05). However, there were significant differences in baseline laboratory values such as GLUC, TG, BUN, GFR, HDL, AST, ALT, WBC, and TNI (P<0.05). These data are presented in Table 1.
Table 1 Baseline characteristics
Variables
|
no-CRBBB
(n=221)
|
CRBBB
(n=40)
|
X2/t/Z
|
P value
|
Age(years)
|
59.36±10.59
|
65.35±10.85
|
-3.278
|
0.001*
|
Men(%)
|
185(83.7)
|
31(77.5)
|
0.916
|
0.339
|
Family history of CVD(%)
|
17(7.7)
|
1(2.5)
|
0.728
|
0.393
|
Smoking(%)
|
145(65.6)
|
22(55)
|
1.655
|
0.198
|
Alcohol(%)
|
52(23.5)
|
11(27.5)
|
0.292
|
0.589
|
Systolic BP(mmHg)
|
124.37±17.65
|
118.83±20.52
|
1.782
|
0.076
|
Diastolic BP(mmHg)
|
80.77±13.43
|
78.25±13.68
|
1.091
|
0.276
|
Heart rate(cpm)
|
80.31±14.49
|
83.13±17.83
|
-0.943
|
0.350
|
GLUC(mmol/L)
|
6.08(5.23,7.41)
|
7.14(5.77,11.40)
|
-2.915
|
0.004*
|
TC(mmol/L)
|
4.97(4.30,5.69)
|
4.59(3.83,5.60)
|
-1.377
|
0.168
|
TG(mmol/L)
|
1.63(1.2,2.59)
|
1.44(1.03,1.92)
|
-2.068
|
0.039*
|
HDL(mmol/L)
|
1.08(0.93,1.28)
|
1.23(1.01,1.52)
|
-2.526
|
0.012*
|
LDL(mmol/L)
|
2.90±0.87
|
2.80±1.07
|
0.660
|
0.510
|
Lp(a)(mmol/L)
|
20.5(8.8,38.05)
|
14.75(8.5,27.78)
|
-1.054
|
0.292
|
UA(umol/L)
|
345(287.5,409)
|
345.5(257,467.25)
|
-0.748
|
0.455
|
BUN(mmol/L)
|
5.19(4.30,6.51)
|
5.52(4.7,7.64)
|
-1.988
|
0.047*
|
Scr(umol/L)
|
78(65,90)
|
82(67.25,108.5)
|
-1.408
|
0.159
|
GFR(ml/min/1.73m2)
|
93.59(75.75,115.07)
|
80.07(62.63,107.01)
|
-2.198
|
0.028*
|
AST(U/L)
|
185(87.5,312)
|
280(182.75,534.25)
|
-3.653
|
<0.001*
|
ALT(U/L)
|
48(32.5,73)
|
67(41,105.5)
|
-2.636
|
0.008*
|
WBC(10~9/L)
|
11.13(9.21,12.89)
|
13.09(9.53,17.66)
|
-2.908
|
0.004*
|
RBC(10~12/L)
|
4.83±0.61
|
4.87±0.71
|
-0.395
|
0.693
|
HB(g/L)
|
149.19±18.28
|
150.13±21.38
|
-0.291
|
0.771
|
PLT(10~9/L)
|
211.04±67.44
|
215.93±64.36
|
-0.424
|
0.672
|
BNP(pg/mL)
|
102(44.85,233.5)
|
100.65(40.9,244.75)
|
-0.153
|
0.879
|
D-D(ng/mL)
|
473(101,1180)
|
487.5(114,1505)
|
-0.761
|
0.446
|
CK-MB(ng/mL)
|
80(43.2,80)
|
80(59.6,80)
|
-1.722
|
0.085
|
MYO(ng/mL)
|
495(262.5,500)
|
500(286,500)
|
-0.972
|
0.331
|
TNI(ng/mL)
|
27.9(8.12,30)
|
30(25.23,30)
|
-2.235
|
0.025*
|
Killip class(%)
|
|
|
|
|
I
|
146(66.1)
|
7(17.5)
|
95.104
|
<0.001*
|
II
|
56(25.3)
|
4(10)
|
III
|
4(1.8)
|
11(27.5)
|
IV
|
15(6.8)
|
18(45)
|
- Indicates Fisher's exact test; *Indicates the difference was statistically significant.
CVD, cardiovascular disease; GLUC, glucose; TC, cholesterol; TG, triglyceride; HDL, high density lipoprotein; LDL, low density lipoprotein; Lp(a), Lipoprotein (a); UA, uric acid ;BUN, blood urea nitrogen; Scr, serum creatinine; GFR, glomerular filtration rate; AST, aspartate aminotransferase; ALT, alanine aminotransferase; WBC, white blood cell; RBC, red blood cell; HB, hemoglobin; PLT, platelet; BNP, B-type natriuretic peptide; D-D, D-dimer; CK-MB, Creatine kinas-MB isoenzyme; MYO, myoglobin; TNI, troponin I.
3.2 Interventional therapy data revealed that the median time from first medical contact to wire (FMC2W) and total ischemic time were longer in the CRBBB group, although these differences did not reach statistical significance. In the CRBBB group, 97.5% of the infarction-related arteries (IRA) were proximal left anterior descending (LAD) arteries, while in the no-CRBBB group, 68.8% of the IRA were proximal LAD and 29.9% were mid LAD, representing a statistically significant difference (P<0.001). There were no significant differences between the two groups in terms of TIMI grade, presence of thrombus, number of diseased vessel branches of the IRA before PCI (P>0.05). Additionally, a comparison of intraoperative medications revealed a higher rate of dopamine use in the CRBBB group compared to the no-CRBBB group (P<0.05). However, no statistically significant differences were found in the use of other medications, including atropine, norepinephrine, tirofiban, nitroglycerin, sodium nitroprusside, adenosine, and nicorandil (P>0.05). These findings are presented in Table 2.
Table 2 Analysis of interventional therapy
Variables
|
no-CRBBB
(n=221)
|
CRBBB
(n=40)
|
X2
|
P value
|
PCI modality(%)
|
|
|
|
|
Primary PCI
|
108(48.9)
|
20(50)
|
0.017
-1.806
-0.821
|
0.895
0.071
0.412
|
PCI after thrombolysis
|
113(51.1)
|
20(50)
|
FMC2W(min)
|
248(157.5,367)
|
305.5(208,448.8)
|
ischemic time(min)
|
440(318,674.5)
|
490.5(342.3,682.5)
|
infarct-related arteries(%)
|
|
|
|
|
proximal LAD
|
152(68.8)
|
39(97.5)
|
17.761
|
<0.001*
|
mid LAD
|
66(29.9)
|
1(2.5)
|
distal LAD
|
2(0.9)
|
0(0)
|
right coronary artery
|
1(0.5)
|
0(0)
|
thrombus(%)
|
21(9.5)
|
5(12.5)
|
0.087
|
0.767
|
number of diseased vessel branches(%)
|
|
|
|
|
1
|
95(43)
|
17(42.5)
|
0.029
|
0.986
|
2
|
68(30.8)
|
12(30)
|
3
|
58(26.2)
|
11(27.5)
|
stent diameter(mm)
|
3(2.75,3)
|
3(2.75,3.5)
|
-1.912
|
0.056
|
stent length(mm)
|
24(18,33)
|
23(18,33)
|
-1.070
|
0.285
|
Intraoperative medication(%)
|
|
|
|
|
atropine
|
16(7.2)
|
2(5)
|
0.031
|
0.861
|
dopamine
|
22(10)
|
9(22.5)
|
3.965
|
0.046*
|
norepinephrine
|
19(8.6)
|
8(20)
|
3.598
|
0.058
|
tirofiban
|
87(39.4)
|
12(30)
|
1.262
|
0.261
|
nitroglycerin
|
77(34.8)
|
16(40)
|
0.393
|
0.531
|
sodium nitroprusside
|
26(11.8)
|
8(20)
|
2.027
|
0.154
|
adenosine
|
2(0.9)
|
1(2.5)
|
-
|
0.394
|
nicorandil
|
1(0.5)
|
2(5)
|
-
|
0.062
|
-Indicates Fisher's exact test; *Indicates the difference was statistically significant.
3.3 The CRBBB group exhibited a higher incidence of in-hospital major adverse cardiovascular events (MACEs), including cardiac death, recurrent myocardial infarction, acute left heart dysfunction, cardiogenic shock, complete atrioventricular block, ventricular fibrillation, and persistent ventricular tachycardia, compared to the no-CRBBB group. Additionally, the median left ventricular ejection fraction (LVEF) was significantly lower in the CRBBB group than in the no-CRBBB group (P < 0.05). Although the mean left ventricular end-diastolic diameter (LVEDD) was greater in the CRBBB group, the difference did not reach statistical significance compared to the no-CRBBB group (P > 0.05). Furthermore, there was a statistically significant difference in the use of vasoactive drugs (dopamine or norepinephrine) and the duration of use post-PCI between the two groups (P < 0.05). These results are summarized in Table 3.
Table 3 Analysis of prognosis
Variables
|
no-CRBBB
(n=221)
|
CRBBB
(n=40)
|
X2/t/Z
|
P value
|
in-hospital major adverse cardiovascular events(%)
|
84(38)
|
29(72.5)
|
16.412
|
<0.001*
|
LVEF(%)
|
60(52.5,67)
|
55(44.25,61)
|
-2.644
|
0.008*
|
LVEDD(mm)
|
48.84±6.70
|
49.46±4.08
|
-0.794
|
0.429
|
the use of vasoactive drugs after PCI(%)
|
39(17.6)
|
13(32.5)
|
4.683
|
0.030*
|
the duration of vasoactive drugs use after PCI(day)
|
0(0,0)
|
0(0,2)
|
-2.345
|
0.019*
|
*Indicates the difference was statistically significant.
3.4 Evaluation of microcirculatory function post-PCI revealed that the CRBBB group had a higher percentage of patients with TIMI ≤ grade 2 and ST-segment regression (STR) <50% in the IRA compared to the no-CRBBB group. Furthermore, the caIMR was significantly higher in the CRBBB group than in the no-CRBBB group (P < 0.05). However, the median corrected TIMI frame count (CTFC) was not statistically different between the two groups (P > 0.05). These findings are detailed in Table 4.
Table 4 Analysis of the microcirculatory function post-PCI
Variables
|
no-CRBBB
(n=221)
|
CRBBB
(n=40)
|
X2/Z
|
P value
|
TIMI grade(%)
|
|
|
|
|
≤2
|
19(8.6)
|
10(25)
|
7.640
|
0.006*
|
3
|
202(91.4)
|
30(75)
|
STR(%)
|
|
|
|
|
≥50%
|
181(81.9)
|
14(35)
|
39.434
|
<0.001*
|
<50%
|
40(18.1)
|
26(65)
|
CTFC(frames)
|
21.18(15.29,27.06)
|
24.71(15.88,32.65)
|
-1.622
|
0.105
|
caIMR
|
29.5(23.8,35)
|
40.25(33.35,49.68)
|
-5.650
|
<0.001*
|
*Indicates the difference was statistically significant.
3.5 Multivariate analysis was conducted to assess the microcirculatory function after PCI, with new CRBBB as the dependent variable. Binary logistic regression was utilized to adjust for confounding factors. The results demonstrated that, in addition to admission Killip classification, GLUC, HDL, and the location of IRA, TIMI grade ≤2 (OR=6.833, 95% CI: 1.009~46.287, P=0.049), STR ≥50% (OR=0.176, 95% CI: 0.051~0.606, P=0.006), CTFC (OR=1.079, 95% CI: 1.009~1.155, P=0.027), and caIMR (OR=1.120, 95% CI: 1.059~1.185, P<0.001) were independently associated with the presence of new CRBBB in patients with acute anterior STEMI. These associations are presented in Table 5.
Table 5 Analysis of microcirculatory function after PCI after correction for confounders
Variables
|
B value
|
Standard error of b-value
|
Wald's chi-square value
|
P value
|
OR value
|
95%CI
|
Age(years)
|
0.064
|
0.035
|
3.403
|
0.065
|
1.066
|
0.996~1.141
|
Killip class
|
0.859
|
0.274
|
9.846
|
0.002*
|
2.360
|
1.380~4.035
|
GLUC(mmol/L)
|
0.241
|
0.107
|
5.094
|
0.024*
|
1.272
|
1.032~1.569
|
TG(mmol/L)
|
-0.446
|
0.410
|
1.181
|
0.277
|
0.640
|
0.286~1.431
|
HDL(mmol/L)
|
1.878
|
0.953
|
3.882
|
0.049*
|
6.540
|
1.010~42.348
|
BUN(mmol/L)
|
-0.356
|
0.225
|
2.508
|
0.113
|
0.701
|
0.451~1.088
|
GFR(ml/min/1.73m2)
|
-0.012
|
0.012
|
1.095
|
0.295
|
0.988
|
0.966~1.011
|
AST(U/L)
|
0.001
|
0.002
|
0.177
|
0.674
|
1.001
|
0.997~1.005
|
ALT(U/L)
|
0.006
|
0.011
|
0.312
|
0.577
|
1.006
|
0.985~1.028
|
WBC(10~9/L)
|
0.176
|
0.095
|
3.476
|
0.062
|
1.193
|
0.991~1.436
|
TNI(ng/mL)
|
-0.020
|
0.036
|
0.295
|
0.587
|
0.981
|
0.914~1.052
|
PART of IRA
|
-4.149
|
1.646
|
6.357
|
0.012*
|
0.016
|
0.001~0.397
|
Dopamine use
|
-1.234
|
1.138
|
1.178
|
0.278
|
0.291
|
0.031~2.705
|
TIMI≤ grade 2
|
1.922
|
0.976
|
3.876
|
0.049*
|
6.833
|
1.009~46.287
|
STR≥50%
|
-1.740
|
0.632
|
7.583
|
0.006*
|
0.176
|
0.051~0.606
|
CTFC(frames)
|
0.076
|
0.035
|
4.913
|
0.027*
|
1.079
|
1.009~1.155
|
caIMR
|
0.114
|
0.029
|
15.603
|
<0.001*
|
1.120
|
1.059~1.185
|
*Indicates the difference was statistically significant.
3.6 The Killip grading system demonstrated the highest predictive value for new combined CRBBB in acute anterior STEMI, with an AUC of 82.5% (P<0.001), indicating excellent discrimination. The caIMR value showed good predictive power, with an AUC of 78.1% (P<0.001).(Figure 1)