The presence of bundle branch block (BBB) in patients with ST-segment elevation myocardial infarction has been associated with a poor outcome. However, the implications of BBB in patients undergoing primary angioplasty in the stent era are poorly established. Furthermore, the prognostic implications of BBB type (right vs left and previous vs transient or persistent) remain unknown. We analyzed the data from 913 consecutive patients with ST-segment elevation myocardial infarction treated with primary angioplasty. All clinical, electrocardiographic, and angiographic data were prospectively collected. The median follow-up period was 19 months. The primary end point was the combined outcome of death and reinfarction. BBB was documented in 140 patients (15%). Right BBB (RBBB) was present in 119 patients (13%) and was previous in 27 (23%), persistent in 45 (38%), and transient in 47 (39%). Left BBB (LBBB) was present in 21 patients (2%) and was previous in 8 (38%), persistent in 9 (43%), and transient in 4 (19%). Patients with BBB were older, and more frequently had diabetes, anterior infarctions, a greater Killip class, a lower left ventricular ejection fraction, and greater mortality (all p <0.005) than patients without BBB. The short- and long-term primary outcome occurred more frequently in patients with persistent RBBB/LBBB than in those with previous or transient RBBB/LBBB. On multivariate analysis, persistent RBBB/LBBB emerged as an independent predictor of death and reinfarction. In conclusion, in patients undergoing primary angioplasty in the stent era, BBB is associated with poor short- and long-term prognosis. This risk appears to be particularly high among patients with persistent BBB.
The onset of bundle branch block (BBB) in patients with ST-segment elevation myocardial infarction (STEMI) has been associated with a high mortality rate. In the prethrombolytic era, several studies showed that the presence of left BBB (LBBB) and right BBB (RBBB) was associated with large infarct sizes and often accompanied by heart failure, ventricular arrhythmia, or death. Although thrombolytic reperfusion decreased mortality in patients with STEMI, the appearance of BBB was still associated with a poor short- and long-term prognosis. Primary percutaneous coronary intervention (PCI) is currently considered the therapy of choice for patients with STEMI. Although some reports have addressed the incidence and prognosis of BBB in this setting, most of them have been post hoc analyses of large clinical trials that were not designed for this purpose. Moreover, most of the studies lacked long-term clinical follow-up or failed to analyze the importance of different BBB types (previous, transient, and persistent). The purpose of the present study was to assess the incidence of BBB in a consecutive series of unselected patients undergoing primary PCI in the stent era and to determine the short- and long-term prognosis.
Methods
All consecutive patients with STEMI undergoing primary PCI at San Carlos University Hospital from January 2004 to June 2008 were included. During this period, primary PCI was the default strategy for patients with STEMI at our institution. STEMI was defined according to the current clinical practice guidelines. Patients undergoing rescue PCI after failed thrombolysis and those with a pacing rhythm on the admission electrocardiogram were excluded.
A 12-lead electrocardiogram was obtained on admission and then repeated at the coronary care unit every 8 hours for the first 24 hours after PCI, once daily thereafter until discharge, and whenever a change in the QRS complex was noted on the monitor lead during the intervention or in the coronary care unit. The diagnostic criteria for conduction disturbances were defined by standard electrocardiographic criteria. BBB was present when the QRS duration was ≥120 ms. RBBB was present when the secondary R wave (R′) in V 1 and a wide S wave in leads V 5 to V 6 were detected. LBBB was considered present in the presence of a monophasic R wave and the absence of Q waves in leads I, V 5 , and V 6 , together with intrinsicoid deflection delay in leads V 5 and V 6 . BBB was classified as previous when it was documented on a previous electrocardiogram (previous electrocardiograms from the patients or other institutions were systematically collected and analyzed), transient when it resolved during the hospital stay, and persistent when it continued until the end of the hospital stay.
Emergency coronary angiography was performed through the femoral or radial arteries. PCI was performed using the standard technique and equipment and was confined to the infarct-related artery. Patients received aspirin 200 to 300 mg on admission and a loading dose of clopidogrel (300 to 600 mg) if contraindications were absent. At the beginning of the procedure, the patients received unfractioned heparin (70 to 100 UI//kg, depending on the concomitant use of glycoprotein IIb/IIIa inhibitors) and additional intravenous boluses to maintain an activating clotting time of >300 seconds. The use of glycoprotein IIb/IIIa inhibitors and thrombus removal devices were left to the preference of the attending interventionist. Coronary stenting was the default strategy during the study period; however, in rare cases, the interventionist decided not to implant a stent when the anatomic setting was considered highly unfavorable (e.g., small vessel size, bifurcation).
All demographic and clinical data, angiographic variables, and treatment received before and during admission were prospectively collected. Major adverse cardiovascular events during the hospital stay were systematically recorded. The primary study end point was the combined outcome of death and reinfarction. After discharge, follow-up visits were performed to assess the long-term outcomes; patients who did not come to the follow-up visit were interviewed by telephone. Patients gave written informed consent, and all results were analyzed according to the current data protection laws and following the ethical principles of the Declaration of Helsinki.
Univariate analysis was performed, and the frequencies and percentages were recorded for each categorical variable, along with the mean ± SD of the quantitative variables. The Kolmogorov-Smirnov test was used to analyze the normal distribution of variables. The chi-square test was used to determine the association between categorical variables. The association between quantitative variables and the appearance of adverse events was studied using the Student t test or analysis of variance, according to the number of categories of the selected variable. Multivariate analysis (logistic regression) was used to calculate the odds ratio (OR) and 95% confidence interval (CI) of death and reinfarction, adjusted for the variables that were significant on univariate analysis and/or clinically relevant after excluding potential interactions and collinearity: age, diabetes mellitus, previous acute myocardial infarction or PCI, Killip class ≥2, left ventricular ejection fraction <40%, anterior acute myocardial infarction, proximal occlusion, peak creatinine kinase, peak troponin, RBBB, and LBBB. Finally, Kaplan-Meier curves were constructed to estimate the survival rates, and comparisons were performed using the log-rank test. Statistical significance was set at p <0.05. Statistical analysis was performed using Statistical Package for Social Sciences, version 15.0, software (SPSS, Chicago, Illinois).
Results
A total of 913 consecutive patients were included in the present study. RBBB was documented in 119 patients (13%). It was previously documented in 27 (23%), persistent in 45 (38%), and transient in 47 (39%). LBBB was present in 21 patients (2%), and was previously documented in 8 (38%), persistent in 9 (43%), and transient in 4 (19%). The baseline characteristics, angiographic findings, and in-hospital outcomes of patients with and without RBBB and LBBB are listed in Tables 1 through 4 .
| Variable | No RBBB | RBBB | p Value | Previous RBBB | p Value | Persistent RBBB | p Value | Transient RBBB | p Value |
|---|---|---|---|---|---|---|---|---|---|
| Patients | 794 | 119 | — | 27 | — | 45 | — | 47 | — |
| Age (years) | 62 ± 13 | 69 ± 12 | <0.001 | 72 ± 9 | <0.001 | 68 ± 12 | 0.007 | 68 ± 136 | 0.017 |
| Men | 616 (78%) | 91 (77%) | 0.814 | 22 (82%) | 0.815 | 35 (78%) | 0.955 | 34 (72%) | 0.391 |
| Hypertension | 387 (49%) | 62 (52%) | 0.555 | 8 (30%) | 0.055 | 23 (51%) | 0.879 | 31 (66%) | 0.018 |
| Diabetes mellitus | 169 (21%) | 44 (37%) | <0.001 | 11 (41%) | <0.001 | 18 (41%) | <0.001 | 15 (32%) | 0.153 |
| Dyslipidemia | 311 (39%) | 45 (38%) | 0.840 | 8 (30%) | 0.423 | 17 (38%) | 0.864 | 20 (43%) | 0.607 |
| Smoker | 165 (21%) | 32 (27%) | 0.151 | 9 (33%) | 0.152 | 14 (31%) | 0.111 | 9 (19%) | 0.678 |
| Previous acute myocardial infarction | 88 (11%) | 21 (18%) | 0.048 | 5 (19%) | 0.358 | 11 (24%) | 0.008 | 5 (11%) | 0.778 |
| Previous percutaneous coronary intervention | 77 (10%) | 21 (18%) | 0.007 | 3 (11%) | 0.193 | 13 (28%) | <0.001 | 5 (11%) | 0.963 |
| Previous coronary artery bypass grafting | 22 (3%) | 3 (2%) | 0.761 | 1 (4%) | 0.533 | 1 (2%) | 0.248 | 1 (2%) | 0.792 |
| Killip class ≥2 | 155 (19%) | 61 (51%) | <0.001 | 2 (7%) | 0.072 | 36 (80%) | <0.001 | 23 (49%) | <0.001 |
| Left ventricular ejection fraction <40% at admission | 103 (13%) | 40 (33%) | <0.001 | 3 (11%) | 0.787 | 25 (56%) | <0.001 | 12 (26%) | 0.060 |
| Peak creatinine kinase (UI/L) | 2,166 ± 1746 | 2,833 ± 2,681 | 0.019 | 2,102 ± 1718 | 0.702 | 2,616 ± 2,416 | 0.387 | 3,386 ± 3,180 | <0.001 |
| Peak troponin (ng/ml) | 92 ± 140 | 123 ± 137 | 0.045 | 122 ± 190 | 0.350 | 104 ± 137 | 0.746 | 140 ± 130 | 0.047 |
| Anterior acute myocardial infarction | 296 (37%) | 62 (52%) | 0.002 | 5 (19%) | 0.025 | 29 (64%) | <0.001 | 28 (60%) | 0.004 |
| Infarct-related artery | |||||||||
| Left anterior descending | 330 (42%) | 72 (61%) | <0.001 | 9 (33%) | 0.256 | 31 (69%) | 0.001 | 32 (68%) | 0.001 |
| Right | 349 (44%) | 33 (28%) | 0.002 | 16 (59%) | 0.064 | 15 (16%) | <0.001 | 12 (25%) | 0.008 |
| Left circumflex | 102 (13%) | 10 (8%) | 0.168 | 1 (4%) | 0.169 | 5 (11%) | 0.808 | 4 (9%) | 0.420 |
| Left main | 11 (1%) | 2 (2%) | 0.800 | 0 (0%) | 0.526 | 2 (4%) | 0.079 | 0 (0%) | 0.398 |
| Vein graft/internal mammary | 2 (0.3%) | 1 (1%) | 0.296 | 1 (4%) | 0.002 | 0 (0%) | 0.693 | 0 (0%) | 0.686 |
| Thrombolysis In Myocardial Infarction 2-3 flow | |||||||||
| Baseline | 146 (18%) | 19 (16%) | 0.610 | 4 (15%) | 0.803 | 6 (13%) | 0.550 | 9 (19%) | 0.846 |
| Final | 747 (94%) | 111 (93%) | 0.677 | 26 (96%) | 0.934 | 40 (89%) | 0.181 | 45 (96%) | 0.856 |
| Proximal occlusion | 363 (46%) | 71 (60%) | 0.004 | 13 (48%) | 0.948 | 33 (73%) | <0.001 | 25 (53%) | 0.425 |
| Stent used | 709 (89%) | 102 (86%) | 0.248 | 23 (85%) | 0.542 | 35 (78%) | 0.016 | 44 (94%) | 0.285 |
| Drug-eluting stent | 324 (41%) | 45 (38%) | 0.176 | 9 (33%) | 0.776 | 14 (31%) | 0.133 | 22 (47%) | 0.195 |
| Percutaneous coronary intervention success | 754 (95%) | 114 (96%) | 0.694 | 26 (96%) | 0.765 | 42 (93%) | 0.581 | 46 (98%) | 0.362 |
| Treatment during admission | |||||||||
| Aspirin | 753 (95%) | 118 (99%) | 0.073 | 26 (96%) | 0.647 | 45 (100%) | 0.626 | 47 (100%) | 0.258 |
| Clopidogrel | 756 (96%) | 115 (97%) | 0.607 | 26 (96%) | 0.647 | 43 (96%) | 0.665 | 46 (98%) | 0.715 |
| Glycoprotein IIb/IIIa inhibitors | 450 (57%) | 58 (48%) | 0.087 | 14 (52%) | 0.693 | 18 (40%) | 0.020 | 26 (55%) | 0.972 |
| β Blockers | 609 (77%) | 86 (72%) | 0.254 | 21 (78%) | 0.524 | 35 (77%) | 0.568 | 30 (64%) | 0.071 |
| Calcium antagonist | 14 (2%) | 4 (3%) | 0.518 | 0 (0%) | 0.756 | 2 (4%) | 0.603 | 2 (4%) | 0.119 |
| Statins | 713 (90%) | 107 (89%) | 0.723 | 22 (82%) | 0.185 | 43 (96%) | 0.506 | 42 (89%) | 0.503 |
| Variable | Without RBBB | With RBBB | p Value | Previous RBBB | p Value | Persistent RBBB | p Value | Transient RBBB | p Value |
|---|---|---|---|---|---|---|---|---|---|
| Patients | 794 | 119 | 27 | 45 | 47 | ||||
| Death | 43 (5%) | 20 (17%) | <0.001 | 0 (0%) | 0.151 | 19 (42%) | <0.001 | 1 (2%) | 0.185 |
| Reinfarction | 25 (3%) | 11 (9%) | 0.001 | 2 (7%) | 0.348 | 7 (16%) | <0.001 | 2 (4%) | 0.910 |
| Postinfarction angina | 12 (2%) | 8 (7%) | <0.001 | 0 (0%) | 0.430 | 4 (9%) | 0.002 | 4 (9%) | 0.002 |
| Repeat percutaneous coronary intervention | 7 (1%) | 2 (2%) | 0.411 | 1 (4%) | 0.147 | 0 (0%) | 0.492 | 1 (2%) | 0.416 |
| Coronary artery bypass grafting | 5 (1%) | 1 (1%) | 0.791 | 0 (0%) | 0.668 | 1 (2%) | 0.183 | 0 (0%) | 0.567 |
| Stent thrombosis | 22 (3%) | 6 (5%) | 0.180 | 2 (7%) | 0.184 | 4 (9%) | 0.020 | 0 (0%) | 0.211 |
| Mechanical complications ⁎ | 6 (1%) | 1 (1%) | 0.898 | 0 (0%) | 0.327 | 1 (2%) | <0.001 | 0 (0%) | 0.816 |
| Major bleeding | 11 (2%) | 11 (9%) | <0.001 | 2 (7%) | 0.086 | 5 (11%) | <0.001 | 4 (9%) | 0.005 |
| Asystole | 13 (2%) | 7 (6%) | 0.002 | 0 (0%) | 0.429 | 5 (11%) | <0.001 | 2 (4%) | 0.291 |
| Ventricular fibrillation/ventricular tachycardia | 85 (11%) | 44 (37%) | <0.001 | 2 (7%) | 0.309 | 27 (60%) | <0.001 | 15 (32%) | <0.001 |
| Complete auriculoventricular block | |||||||||
| Permanent | 20 (3%) | 16 (13%) | <0.001 | 3 (11%) | 0.052 | 9 (20%) | <0.001 | 4 (9%) | 0.099 |
| Transient | 68 (9%) | 14 (12%) | 0.255 | 5 (19%) | 0.078 | 3 (7%) | 0.578 | 6 (13%) | 0.351 |
⁎ Including left ventricular free wall rupture, ventricular septal rupture, and acute mitral regurgitation.
| Variable | Without LBBB | With LBBB | p Value | Previous LBBB | p Value | Persistent LBBB | p Value | Transient LBBB | p Value |
|---|---|---|---|---|---|---|---|---|---|
| Patients | 892 | 21 | 8 | 9 | 4 | ||||
| Age (years) | 63 ± 13 | 69 ± 15 | 0.037 | 69 ± 15 | 0.254 | 73 ± 14 | 0.022 | 61 ± 17 | 0.766 |
| Men | 693 (78%) | 14 (67%) | 0.232 | 4 (50%) | 0.062 | 7 (78%) | 0.980 | 3 (75%) | 0.907 |
| Hypertension | 435 (49%) | 14 (67%) | 0.105 | 5 (63%) | 0.449 | 7 (78%) | 0.085 | 2 (50%) | 0.974 |
| Diabetes mellitus | 206 (23%) | 7 (33%) | 0.273 | 2 (25%) | 0.911 | 5 (56%) | 0.022 | 0 (0%) | 0.269 |
| Dyslipidemia | 348 (39%) | 8 (38%) | 0.932 | 4 (50%) | 0.521 | 3 (33%) | 0.726 | 1 (25%) | 0.565 |
| Smoker | 192 (22%) | 5 (24%) | 0.801 | 2 (25%) | 0.813 | 3 (33%) | 0.389 | 0 (0%) | 0.583 |
| Previous acute myocardial infarction | 107 (12%) | 2 (10%) | 0.730 | 1 (13%) | 0.961 | 1 (11%) | 0.939 | 0 (0%) | 0.601 |
| Previous percutaneous coronary intervention | 96 (11%) | 3 (14%) | 0.608 | 0 (0%) | 0.322 | 3 (33%) | 0.064 | 0 (0%) | 0.631 |
| Previous coronary artery bypass grafting | 25 (3%) | 0 (%) | 0.437 | 0 (0%) | 0.634 | 0 (0%) | 0.613 | 0 (0%) | 0.895 |
| Killip class ≥2 | 204 (23%) | 12 (57%) | <0.001 | 0 (0%) | 0.113 | 8 (89%) | <0.001 | 4 (100%) | <0.001 |
| Left ventricular ejection fraction <40% at admission | 135 (15%) | 8 (38%) | 0.007 | 2 (25%) | 0.620 | 4 (44%) | 0.025 | 2 (50%) | 0.120 |
| Peak creatinine kinase (UI/L) | 2,232 ± 1876 | 3,141 ± 2,814 | 0.052 | 2,681 ± 3,037 | 0.523 | 3,444 ± 2,514 | 0.124 | 3,760 ± 3,680 | 0.007 |
| Peak troponin (ng/ml) | 95 ± 135 | 148 ± 143 | 0.113 | 129 ± 131 | 0.486 | 171 ± 191 | 0.174 | 180 ± 98 | 0.049 |
| Anterior acute myocardial infarction | 349 (39%) | 9 (43%) | 0.737 | 2 (25%) | 0.405 | 5 (56%) | 0.316 | 2 (50%) | 0.661 |
| Infarct-related artery | |||||||||
| Left anterior descending | 392 (44%) | 10 (48%) | 0.738 | 3 (38%) | 0.709 | 5 (56%) | 0.484 | 2 (50%) | 0.810 |
| Right | 375 (42%) | 7 (33%) | 0.418 | 4 (50%) | 0.643 | 2 (22%) | 0.228 | 1 (25%) | 0.491 |
| Left circumflex | 109 (12%) | 3 (14%) | 0.775 | 1 (13%) | 0.984 | 1 (11%) | 0.915 | 1 (25%) | 0.437 |
| Left main | 11 (1%) | 1 (5%) | 0.191 | 0 (0%) | 0.733 | 1 (11%) | 0.140 | 0 (0%) | 0.810 |
| Vein graft/internal mammary | 3 (0.3%) | 0 (0%) | 0.790 | 0 (0%) | 0.870 | 0 (0%) | 0.863 | 0 (0%) | 0.908 |
| Thrombolysis In Myocardial Infarction 2-3 flow | |||||||||
| Baseline | 161 (18%) | 4 (19%) | 0.781 | 2 (25%) | 0.641 | 1 (11%) | 0.496 | 1 (25%) | 0.550 |
| Final | 838 (94%) | 20 (95%) | 0.630 | 8 (100%) | 0.612 | 8 (89%) | 0.576 | 4 (100%) | 0.783 |
| Proximal occlusion | 425 (48%) | 9 (43%) | 0.664 | 1 (13%) | 0.046 | 5 (56%) | 0.628 | 3 (75%) | 0.270 |
| Stent used | 792 (89%) | 19 (91%) | 0.808 | 7 (88%) | 0.905 | 8 (89%) | 0.995 | 4 (100%) | 0.477 |
| Drug-eluting stent | 358 (40%) | 11 (53%) | 0.535 | 2 (25%) | 0.785 | 7 (78%) | 0.137 | 2 (50%) | 0.920 |
| Percutaneous coronary intervention success | 849 (95%) | 19 (91%) | 0.325 | 7 (88%) | 0.320 | 8 (89%) | 0.389 | 4 (100%) | 0.648 |
| Treatment during admission | |||||||||
| Aspirin | 853 (95%) | 18 (87%) | 0.507 | 8 (100%) | 0.687 | 6 (67%) | 0.131 | 4 (100%) | 0.829 |
| Clopidogrel | 853 (95%) | 18 (87%) | 0.507 | 8 (100%) | 0.687 | 6 (67%) | 0.131 | 4 (100%) | 0.829 |
| Glycoprotein IIb/IIIa inhibitors | 497 (56%) | 11 (52%) | 0.612 | 6 (75%) | 0.396 | 4 (44%) | 0.500 | 1 (25%) | 0.217 |
| β Blockers | 685 (77%) | 10 (48%) | 0.060 | 5 (63%) | 0.294 | 3 (33%) | 0.144 | 2 (50%) | 0.243 |
| Calcium-antagonist | 17 (2%) | 1 (5%) | 0.267 | 0 (0%) | 0.923 | 0 (0%) | 0.970 | 1 (25%) | 0.135 |
| Statins | 805 (89%) | 15 (75%) | 0.194 | 8 (100%) | 0.417 | 4 (44%) | 0.290 | 3 (75%) | 0.353 |
| Variable | Without LBBB | With LBBB | p Value | Previous LBBB | p Value | Persistent LBBB | p Value | Transient LBBB | p Value |
|---|---|---|---|---|---|---|---|---|---|
| Patients | 892 | 21 | 8 | 9 | 4 | ||||
| Death | 57 (6%) | 6 (29%) | <0.001 | 0 (0%) | 0.439 | 6 (67%) | <0.001 | 0 (0%) | 0.585 |
| Reinfarction | 33 (4%) | 3 (14%) | 0.184 | 0 (0%) | 0.565 | 2 (22%) | 0.037 | 1 (25%) | 0.030 |
| Postinfarction angina | 19 (2%) | 1 (5%) | 0.415 | 0 (0%) | 0.671 | 0 (0%) | 0.262 | 1 (25%) | 0.002 |
| Repeat percutaneous coronary intervention | 9 (1%) | 0 (0%) | 0.644 | 0 (0%) | 0.777 | 0 (0%) | 0.764 | 0 (0%) | 0.841 |
| Coronary artery bypass grafting | 6 (1%) | 0 (0%) | 0.706 | 0 (0%) | 0.817 | 0 (0%) | 0.806 | 0 (0%) | 0.870 |
| Stent thrombosis | 26 (3%) | 2 (10%) | 0.083 | 0 (0%) | 0.613 | 1 (11%) | 0.016 | 1 (25%) | 0.011 |
| Mechanical complications ⁎ | 7 (1%) | 0 (0%) | 0.623 | 0 (0%) | 0.925 | 0 (0%) | 0.920 | 0 (0%) | 0.947 |
| Major bleeding | 19 (2%) | 3 (15%) | <0.001 | 0 (0%) | 0.655 | 2 (22%) | <0.001 | 1 (25%) | 0.003 |
| Asystole | 17 (2%) | 3 (15%) | <0.001 | 0 (0%) | 0.690 | 3 (33%) | <0.001 | 0 (0%) | 0.764 |
| Ventricular fibrillation/ventricular tachycardia | 122 (14%) | 7 (33%) | 0.011 | 0 (0%) | 0.249 | 4 (44%) | 0.009 | 3 (75%) | <0.001 |
| Complete auriculoventricular block | |||||||||
| Permanent | 31 (4%) | 5 (24%) | <0.001 | 0 (0%) | 0.565 | 5 (56%) | <0.001 | 0 (0%) | 0.685 |
| Transient | 80 (9%) | 2 (10%) | 0.930 | 0 (0%) | 0.372 | 1 (11%) | 0.822 | 1 (25%) | 0.261 |
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