Journal of Interventional Cardiac Electrophysiology https://doi.org/10.1007/s10840-018-0430-3

Bundle branch blocks and/or hemiblocks complicating acute myocardial or infarction

Samuel Lévy1

Received: 23 May 2018 /Accepted: 24 July 2018 # Springer Science+Business Media, LLC, part of Springer Nature 2018

Abstract Despite the bulk of anatomical and histologic evidence supporting the existence of three fascicules in the left branch of the His bundle, the concept of a bifascicular system proposed by Rosenbaum and his school has been adopted by the cardiological community as a practical teaching tool. Left anterior hemiblock (LAH) refers to block of the antero-superior branch of the left branch which is small and left posterior hemiblock (LPH) to block of the postero-inferior branch which is larger. The LAH is more common that the LPH and often associated with a complete right (RBBB). (CAD) is a major cause of hemiblocks. In this review article, we discuss various aspects of the relation of hemiblocks with CAD. We looked at the prevalence of LAH in consecutive patients undergoing coronary angiography and who had a significant coronary lesion in one vessel or more. In all patients with LAH, a significant lesion of the left anterior descending coronary artery was present, with in the majority of patients, an impairment of the left ventricular function. Bifascicular block (RBBB with LAH or LPH) can complicate acute and is often associated with a poor prognosis and the presence of failure. Thrombolysis and or early angioplasty in acute myocardial infarction have significantly improved the prognosis and reduced the mortality associated with bifascicular block. Left anterior hemiblock pattern was also observed during pectoris occurring at rest or induced by exercise or atrial pacing. In these circumstances, LAH is transient and is likely to be due to ischemia in the anterolateral wall related to a lesion of the main trunk or the proximal left anterior descending coronary artery with the postero-inferior wall being first depolarized. The presence of bifascicular block in acute myocardial infarction still is associated with an unfavorable prognosis as compared to non-bundle branch block patients because of the common association with and other comorbidities.

Keywords Right bundle branch block . Left anterior hemiblock . Left posterior hemiblock . Bifascicular block . Angina pectoris .

1 Introduction anatomical lesions. However, Rosenbaum and colleagues in 1968 adopted the concept of a bifascicular system in their Despite the bulk of evidence both anatomical and histological description of the electrocardiographic features of what supporting the possible existence of three fascicles in the left they called “hemiblocks” [4, 5] and used since as a practical branch of the His bundle as described in anatomical and the teaching tool. The hemiblocks refer to delay or block in the historical reports, the “bifascicular concept” has gained popu- antero-superior fascicle of the left branch of the His bundle larity [1–3]. The main left branch subdivides into an antero- (LAH) or to delay or block in the postero-inferior fascicle superior branch, a postero-inferior branch and possibly a sep- (LPH) although at times the block may be “focal” corre- tal branch. It should be emphasized that the anatomy of the sponding not to conduction delay or block in the fascicles left branch of the His bundle is more complex than previ- of the left branch but to conduction delay of the impulse in ously thought and it is hypothetical to establish a relation the myocardial territory of one or the other fascicle. Some between the electrocardiographic aspects and the possible authors prefer to use the term “fascicular blocks” instead of hemiblocks. But hemiblocks refer to ECG characteristics and not to possible lesions in the left bundle branch system. * Samuel Lévy In this review, we will use the nomenclature proposed by [email protected] Rosenbaum and his school [3–5] in their remarkable efforts “ ” 1 to promote the bifascicular concept of the left branch Aix-Marseille Université, School of Medicine, 2, Place Delibes, – 13008 Marseille, France system. Castellanos et al. [6 10] adopted their ECG J Interv Card Electrophysiol definitions with minor modifications in their study of include [1] (≥ 100°), (2) S1Q3 pattern hemiblocks in acute myocardial infarction (MI). in the limb leads, (3) QRS duration ≤ 110 ms, (4) rS The LAH and the LPH may be isolated or most of the morphology in I and aVL, and (5) qR pattern in II, III, times associated with right bundle branch block (RBBB). VF. The diagnosis should exclude other causes of right Such conduction disturbances may be associated with cor- axis deviation such as right , ver- onary artery disease (CAD) which is the most common tical heart in slender subjects, asthma, chronic obstructive underlying heart disease and may complicate the course of pulmonary disease and mitral stenosis. Left posterior an acute MI. The other common etiologies of conduction hemiblock with RBBB complicating an acute inferior disturbances include the in South America wall MI is shown in Fig. 2. Note the Q waves in leads and the primary fibrosis of the conduction system called II, III and VF. Lenègre disease [11] or Lev disease [12]. As stated before, the “bifascicular system scheme” is a teaching tool to describe these ECG aspects which does reflect the complexity of the left branch anatomy or the disease that 2 Diagnostic ECG criteria for hemiblocks may affect its branches. Furthermore, a middle fascicule may be present and ECG aspects possibly affecting the left septal The electrocardiographic features of hemiblocks may vary fascicle have been reported [13, 14]. Interconnections be- according to the clinical context, to the serial ECG trac- tween the fascicles create a network what Fisher in this issue ings recorded in a given patient and to the anatomic mor- called a “spiderweb” [2]. phology of the patient. The ECG diagnosis for LAH in- cludes three criteria according to Rosenbaum [4, 5]and Elizarietal.[3]: [1] a (− 45° or more). 3 Pure left anterior hemiblock in coronary For Castellanos et al. [6–10] an axis deviation ranging artery disease patients from − 30 to − 90° particularly when there is evidence of normal axis in previous ECG recordings [6]. [2]A Among the studies we did under the guidance of Dr. small q wave in leads I and VL and a small r in leads Agustin Castellanos Jr., we looked at the angiographic II, III and VF. [3] A QRS widening by no more than aspects of pure (without BBB) LAH in patients with sig- 0.02 s and less than 0.11 in total duration. An ECG trac- nificant (at least one or more coronary obstruction ≥ 70%) ing of LAH with RBBB complicating an extensive ante- coronary artery lesions [8]. We reviewed the complete rior wall MI is shown in Fig. 1. Note that the RBBB did ECG files and clinical records of 283 consecutive patients not obscure the diagnosis of acute anterior MI. There are with significant CAD at coronary angiography (> 70% obviously other causes of left axis deviation such as left obstruction) and found “pure” LAHin20ofthem ventricular hypertrophy, horizontal heart or Wolff- (7.3%). The age range was 46–71 years with a mean of Parkinson-White syndrome in some accessory connection 61 years. There were 18 men and 2 women. ECG features locations. Therefore, the clinical context should be taken of old myocardial infarction (MI) were present in 10 pa- into account in ECG interpretation. tients. In all 20 patients (100%), a significant lesion of the Diagnostic criteria for LPH include both ECG criteria proximal left anterior descending (LAD) coronary artery and clinical setting exclusion criteria. The ECG criteria was present. [2] All 20 patients had severe CAD (2.5

Fig. 1 12-lead ECG recorded in a patient admitted for acute anterior wall myocardial infarction and right bundle branch block (RBBB) and left anterior hemiblock (LAH) J Interv Card Electrophysiol

Fig. 2 ECG recorded in a patient with an acute inferior wall myocardial infarction and RBBB with left posterior hemiblock (LPH)

vessels involved per patient). [3] Impairment of LV func- acute MI including the 12 lead ECGs and the hourly mon- tion was found in 14 patients (77%), 9 of them with a left itoring strips were reviewed. The criteria used to diagnose ventricular aneurysm. This study supports CAD as a ma- the presence of hemiblocks are those described by jor cause of pure LAH and the presence of significant Castellanos [6–10] who used the frontal plane of the lesion involving the LAD. vectorcardiogram to describe the LAH characteristics in inferior wall MI: “(1). inferior and rightward orientation of the initial 10 and 20 msec. vectors (inferior orientation 4 Bifascicular block complicating acute of the initial 40-msec vectors, suggests the presence of an myocardial infarction associated lateral infarction); (2) superior and leftward de- before the thrombolysis era viation of the maximal QRS vectors, (3) counterclockwise rotation of the QRS loop, and (4) inferior orientation of the The ECG diagnosis of RBBB and LAH in acute MI may ST-T loop. This results in the ECG in a qR pattern in lead I be sometimes difficult, and conversely, there are cases in and aVL, and rS complexes with positive T waves in leads which the LAH may obscure the diagnosis of myocardial II, III, and aVF. These criteria are still valid in the presence ” infarction. [3–7]. Such difficult cases are well described of complete RBBB . As mentioned before, the diagnosis elsewhere [3] and may require comparison with previous of LPH cannot be made on the basis of the ECG alone as ECG tracings, if available. other conditions may result in similar ECG features. The In this study done with Dr. Castellanos Jr., the ECG ECG changes of LPH consist of: (1) right axis deviation charts of 590 patients admitted to the coronary care unit > + I20); (2) rS complexes in leads I and aVL, and qR of Jackson Memorial Hospital (University of Miami) for an complexes with negative T waves in lead II, III, and aVF.” In our study, we excluded those patients with Table 1 Prevalence and type of bifascicular block in 590 successive RBBB known to be present before admission. As shown in patients admitted in the coronary care unit with the diagnosis of acute myocardial infarction (MI). Patients with known right bundle branch Table 2 Degree of left ventricular failure (HF) on admission to block were excluded from these series coronary care unit. Note that the mortality associated with bifascicular block was high (51%). The higher the degree of heart failure on admission Incidence of bifascicular block in acute MI Acute MI in CCU* and the higher the mortality Number of pts. (Percent) Left ventricular failure on admission Total no. of Pts 590 RBBB and LAH or LPH or both 33 (5.5%) Degree of failure No. of pts. Deaths in CCU (%) RBBB with LAH 20 (60.6%) None 8 2 (25%) RBBB with LPH 8 ((24.2%) Mild to moderate 19 10 (52%) RBBB with LAH or LPH (alternating) 5 (15.1%) Pulmonary edema 4 3 (75%) RBBB on admission 14 (42%) Cardiogenic shock 2 2 (100%) Not present on admission 19 (57%) Total no. of pts. 33 17 (51%) J Interv Card Electrophysiol

Table 3 Maximum degree of heart failure (HF) in coronary care unit. explain the severity of the prognosis in patients with Although the number were small it seemed that the higher the maximum bifascicular block was the degree of left ventricular failure degree of heart failure and the higher the mortality. Note that 8 patients progressed to complete (CHB) and 6 of them died in hospital. on admission as seen in Table 2. This was also true when Note that 5 of them developed left ventricular failure we looked at the maximum degree on left ventricular fail- ure developed during the stay of the patients in the coro- Maximum degree of HF No. of pts. Progression to Deaths in coronary care unit CHB (died) nary care unit as seen in Table 3.

None 7 3 0 Mild to moderate 11 1 (1) 4 Pulmonary edema 8 2 (2) 6 5 Bundle branch block and hemiblocks Cardiogenic Shock 7 2 (2) 7 in the thrombolysis and angioplasty era Total no. of pts. 33 8 (24.2%) 17 Thrombolysis and/or angioplasty early after acute MI have improved the prognosis by reducing the mortality rate associ- Table 1, 33 patients (5.5%) had either RBBB, with LAH or ated with bifascicular block complicating MI. The GISSI Trial LPH. Twenty of the 33 patients (60.6%) had RBBB with in 1986 was the first randomized trial to show benefit with LAH, 8 patients had RBBB with LPH (24.2%), and 5 had thrombolysis using streptokinase IV when given early after RBBB with alternating LAH or LPH. Progression to complete the onset of MI [15]. The GUSTO-1 trial (1993) using strep- heart block occurred in 8 patients (24%). The location of the tokinase and rPA established the concept of the “open artery acute MI was anterior in 25 patients (75%), inferior or poste- hypothesis” [16]. The first angioplasty performed by Andreas rior in 7 patients (21%) and both anterior and inferior in 1 Gruntzig in 1973 was later on applied to acute MI in order to patient (3%). Six of the 8 patients (75%) who progressed to open “the infarct-related artery” [17, 18]. Angioplasty done complete heart block died in the hospital and the remaining 2 early after MI was also found to be superior to thrombolysis were discharged alive. Of the 25 patients who did not progress [19]. Among the studies [20–23] who looked at the mortality to advanced heart block, 13 (52%) died in the hospital and 12 and prognosis of bundle branch block isolated or associated (39%) were discharged alive. The mean follow-up after hos- with left hemiblocks, the study of Newby et al. [23]ispartic- pital discharge was 15.7 months. The two patients who ularly interesting. The authors looked at the new-onset bun- progressed to complete heart block discharged alive from hos- dle branch block in 681 patients treated with thrombolysis pital were still alive at the time of follow-up. Of the 12 patients and angioplasty detected by 12-lead ECG monitoring for 36 who did not progress to complete heart block and who were to 72 h. They found an overall incidence of BBB of 23.6% alive to be discharged from the hospital, 6 (24%) were alive, 4 (161patients), transient in 18.4% (125 patients) and persis- died, and 2 patients were lost to follow-up. tent in 5.3% (36 patients). In 89 patients (13.0%) RBBB In summary, the prognosis of RBBB with or without was detected and in 48 patients (7%) LBBB was detected. hemiblocks was poor at the time of our study since 17 of Alternating BBB occurred in 24 patients (3.5%). A strong the 33 patients (51%) with bifascicular block died in the correlation was found between the infarct-related artery and coronary care unit [8]. Among the factors that could the presence of BBB as when the LAD coronary artery was

Table 4 In hospital mortality and follow-up in patients (Pts) with Bundle branch block Number of pts. Mortalityinhospital Discharged alive Follow-up right bundle branch block (percent) no. of pts. from hospital 3–9months (RBBB) and Left Anterior hemiblock (LAH) or Left RBBB + hemiblock 33 (5.5) 19 (57.5) 14 (42.4) Alive: 8 Posterior Hemiblock (LPH) in our Died: 4 series in the pre-thrombolytic era Lost: 2 RBBB + LAH 20 RBBB + LPH 8 RBBB + LAH or LPH 5 Present on admission 14 (42.4) Not present on admission 19 (57.5) LBBB* 18 (3.0) 7 (63.6) 11 (61.1) Alive 3 New 11 Died 6 Present on admission 7 Lost 2 J Interv Card Electrophysiol

Table 5 Incidence, 30-day mortality, and mortality per 100 patient- waves showing minor non-specific changes. During sponta- years in a post-thrombolytic/angioplasty era. (from Melgarejo-Moreno neous chest pain, the 12-lead ECG showed sinus , et al. 2015) left axis deviation consistent with LAH, poor r wave progres- Bundle branch Incidence percent Percent 30 day Mortality at sion from V1–V3 and increased QRS duration from 0.06 to block of acute myocardial mortality 7.2 years per 100 0.10 in lead I (Fig. 3). Non-sustained VT was also recorded infarction patient-years during some episodes of chest pain. Following the angina All BBB 17.3 13.2 6.3 attack, the QRS axis became normal as did the QRS duration. RBBB 10.6 31.6 13.3 Coronary angiogram showed a 60% obstructive lesion of the LBBB 6.7 52.5 27.2 left main trunk and no other significant lesion in the remaining coronary tree. We showed using atrial pacing that the LAH was not rate related but occurred only during angina pain, involved, BBB was present in 54.1% compared to 36.3% spontaneous (at rest) or induced by atrial pacing and prevented for the right coronary artery and 6.9% for the left circum- by nitroglycerin. The LAH was likely in this case to be related flex coronary artery. The mortality was still higher in pa- to myocardial ischemia. We reported subsequently six such tients with BBB (8.7%) than in patients without BBB cases of LAH during angina pectoris at rest which is sugges- (3.5%). Nguyen et al. [24] studied in the Worchester area tive of a proximal severe obstruction of the LAD coronary (MA, USA) the 30-year trend of mortality in patients with artery or of the left main trunk. [26, 27]. These observations acute MI and complete heart block and found since 1991 a are consistent with the two cases of LAH occurring during steady decline from 5 to 2% in 2005. The prognosis of treadmill exercise test reported by Oliveros et al. [28]. bundle branch block complicating an acute myocardial in- AcaseofLAHrelatedtocoronaryarteryspasmina52- farction in the pre-thrombolytic era and in the post-throm- year-old fisherman referred for responsible for his bolytic/angioplasty era is shown in Table 4 and Table 5 shipwreck. He also complained before admission of episodes respectively. It remains poorer than in non-bundle branch of chest pain on exertion [29]. Coronary angiography was block patients because of the more frequent presence of indicated as part of the work-up. The ECG at the onset of heart failure and comorbidities [25]. the procedure showed a change in QRS axis consistent with LAH associated with mild chest discomfort. The coronary angiogram showed total obstruction of the LAD relieved by 6 Hemiblocks related to acute ischemia sublingual nitroglycerin. The likely interpretation for such ECG changes may be that the ischemic anterior wall of the We reported the transient occurrence of LAH in patients dur- left ventricle secondary to spasm of the proximal LAD may ing an episode of angina pectoris at rest in 1977 [26]. In brief, result in conduction delay of the impulse traversing the ische- a 49-year-old patient was admitted for (today mic anterior wall whereas the inferior wall is first relatively called ). On admission, the QRS depolarized explaining the superior axis deviation and the complexes were normal, both in width, in QRS axis, and T increase in QRS duration.

Fig. 3 12-lead ECG tracings recorded in a patient admitted for an acute coronary syndrome. He complained with episodes of angina at rest. Tracing A was recorded on admission. Tracing B was recorded during chest discomfort. Tracing C was recorded soon after as the pain subsided after sublingual nitroglycerin tablet. Note during pain repolarization changes in the anterolateral wall, , and increase in QRS duration (see text). Reproduced from reference from Levy et al. [22]withpermission J Interv Card Electrophysiol

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