A quantitative histopathological study of right bundle branch block complicating acute anteroseptal myocardial infarction

Morphogenetic aspects of the septomarginal trabecula in the human heart

INTRODUCTION

The septomarginal trabecula is a constant element of the anatomy of the human heart, which connects the interventricular septum and the anterior wall of the right ventricle. Considering the diversity of opinions about the structure and numerous studies suggesting its important role in haemodynamics and conduction of electrical impulses in the heart, we decided to study this element in detail.

MATERIAL AND METHODS

The research was conducted on 220 human hearts. Attention was mainly paid to the structure and topography of the trabecula. Its relation to the anterior papillary muscle was also a part of the study.

RESULTS

The presence of this morphologically diverse element was confirmed in each of the studied hearts. In most cases the trabecula originated from the upper part of the interventricular septum, separating at an angle increasing proportionally to the number of branches of the crista supraventricularis as well as the number of secondary trabeculae. The criteria established for the study, which included the course of the trabecula in the lumen of the right ventricle and its relation to the anterior papillary muscle, let us distinguish 4 types of septomarginal trabecula (I, II, III, IV). The most common was type III, the undivided trabecula, tightly connecting with the anterior papillary muscle.

CONCLUSIONS

Based on the results of the following study we propose a hypothesis on the genesis of respective parts of the septomarginal trabecula and a plausible sequence of changes they undergo during human ontogenesis and phylogenesis of the primates.

Determinants of in-hospital death in left main coronary artery myocardial infarction complicated by cardiogenic shock

BACKGROUND

Acute myocardial infarction (AMI) due to left main coronary artery disease is associated with significantly elevated morbidity and mortality. The aim of this study was to identify the predictors of in-hospital death from left main AMI complicated by cardiogenic shock.

METHODS

Clinical record review identified a total of 25 cases of left main AMI with cardiogenic shock. Patients' background characteristics, laboratory data, and angiographic findings were analyzed according to the in-hospital mortality.

RESULTS

In this patient subset, in-hospital mortality (60%) was associated with a history of hypertension (p=0.02) and a higher heart rate (p=0.02). Furthermore, in-hospital mortality was also associated with a complete right bundle branch block (CRBBB) pattern in the admission ECG (p=0.01) and low HCO(3)(-) (p=0.0004). In stepwise logistic regression analysis, a CRBBB pattern (OR 48.59, 95% CI 1.34-1768.10, p=0.03) and low HCO(3)(-) (OR 0.62, 95% CI 0.40-0.94, p=0.02) were found to be independent predictors of mortality.

CONCLUSIONS

Left main AMI with cardiogenic shock was associated with high in-hospital mortality. A CRBBB pattern in the ECG on admission and a low HCO(3)(-) concentration were significant independent predictors of in-hospital death.

Right bundle branch block: varying electrocardiographic patterns. Aetiological correlation, mechanisms and electrophysiology

Ten dissimilar electrocardiographic (ECG) patterns associated with right bundle branch block (RBBB) are presented. Electrophysiologic basis of the changes is discussed and possible causes for such diversity outlined. We have not found any aetiological association to this variation. The morphological diversity in RBBB patterns is likely to be related to multiple factors--site of block, nature of defect (functional, necrosis, fibrosis), degree of conduction delay, and associated pathologies with their own ECG patterns. Distinguishing RBBB from a normal ECG-variant like rsr' is particularly important when associated with left hemiblocks as the latter situation warrants extensive cardiac evaluation.

Incidence and prognostic significance of right bundle branch block in patients with acute myocardial infarction receiving thrombolytic therapy

We assessed the incidence and prognostic significance of right bundle branch block (RBBB) in patients with acute myocardial infarction (AMI) receiving thrombolytic therapy. A prospective, one-year follow-up study involving 681 consecutive patients treated with thrombolytic agents for AMI was performed. Seventy-four patients developed RBBB (46% new-onset, 24% old and 30% indeterminate). RBBB was more common in older patients with large anterior AMI. New-onset RBBB were often transient (56%) and 84% of them resolved within 12 h after admission. Complicating events during the hospital phase, such as ventricular arrhythmias and development of heart failure, were more frequent in patients with RBBB. In-hospital and one-year mortality were higher in patients with RBBB (22.9 and 40.5% compared to 7.9 and 12.3% respectively in patients without block, both p<0.001). New-onset, non-transient RBBB were associated with the highest mortality rates (73% at one-year follow-up). By multivariate analysis, RBBB was retained as independent predictor of in-hospital and one-year mortality. We conclude that new-onset RBBB in patients receiving thrombolytic therapy for AMI is often transient. The development of RBBB has a negative and independent prognostic impact on the survival during the hospital phase and at one-year follow-up.

Incidence, clinical characteristics, and prognostic significance of right bundle-branch block in acute myocardial infarction: a study in the thrombolytic era

BACKGROUND

Whereas the significance of right bundle-branch block (RBBB) in acute myocardial infarction was extensively studied in the prethrombolytic era, a possible change in the overall incidence and meaning of RBBB as a consequence of thrombolytic therapy is not well known.

METHODS AND RESULTS

A multicenter, prospective study of 1238 patients consecutively diagnosed with acute myocardial infarction and admitted to three coronary care units was conducted. ECGs during the acute phase and clinical events until discharge and 1-year follow-up were monitored. In the 135 (10.9%) patients in whom RBBB was found, there were 51 (37.8%) new cases, 46 (34.1%) old cases, and 38 (28.1%) cases with an indeterminate time of origin. New RBBB was permanent in 26 and transient in 25 patients. RBBB was isolated in 76 (56%) and bifascicular in the remaining 59 (44%) patients. The following complications were more frequently associated with RBBB than non-RBBB patients: heart failure, 24% versus 46% (P<.001); use of pacemaker because of atrioventricular block, 3.6% versus 11% (P<.001); and 1-year mortality, 17.6% versus 40.7% (P<.001). Early mortality was significantly higher for new RBBB (43.1%, P<.001) than for old (15.5%) and indeterminate (15.3%) RBBB. These figures for 1-year mortality were 58.8% (P<.001), 35.5 (P<.01), and 23% (NS), respectively. Permanent and transient RBBB had different mortality rates: early mortality, 76% versus 8%, and 1-year mortality, 84% versus 32% (P<.001 for both). For isolated RBBB versus bifascicular block, early mortality was 14.4% versus 40.6%, and 1-year mortality was 30.2% versus 54.2% (P<.05 for both). Multivariate analysis showed an independent prognostic value of RBBB for early and 1-year mortality.

CONCLUSIONS

The overall meaning of RBBB in acute myocardial infarction has not changed in the thrombolytic era, although a higher rate of new and transient RBBB and a lower rate of bifascicular block may represent a beneficial effect of thrombolytic therapy.

Right bundle block in a patient with acute posterior myocardial infarction

We present here a patient with the unusual combination of a newly developed right bundle branch block (RBBB) and an acute posterior myocardial infarction (MI). A dissecting MI with interventricular septal (IVS) rupture was initially thought to have caused RBBB. However, histologic examination revealed that the right bundle branch (RBB) had no ischemic involvement, but did show fibrosis, which suggests that this chronic damage of the RBB was a major contributor to the development of RBBB. This case confirms that the RBB is rarely involved by a posterior MI even in the presence of a dissecting IVS rupture.