Transient left septal fascicular block and left anterior fascicular block as a consequence of proximal subocclusion of the left anterior descending coronary artery

Angiographic description of the anatomy and clinical aspects of the anterior interventricular artery in a group of Colombians individuals

Introduction

The anterior interventricular artery originates from the left coronary artery and irrigates the anterior surface of the ventricles, apex, and interventricular septum, making it the second most relevant artery of the heart.

Objective

To describe the anatomical and clinical aspects of the anterior interventricular artery through angiography.

Materials and methods

A descriptive study was conducted using 200 angiographic reports of Colombian individuals. The anterior interventricular artery's origin, course, patency, and coronary dominance were evaluated. Data related to chest pain, acute myocardial infarction, dyslipidemia, and electrocardiographic abnormalities were included. Statistical tests could not be performed due to this artery's low prevalence of anatomical variations.

Results

One anterior interventricular artery was found to have originated from the left coronary sinus without a myocardial bridge, with no alteration in permeability, and with left dominance. The frequency of bridges was 2%, and the most frequent dominance was right in 86%; permeability alterations occurred in 43% mainly affecting S13. Twentyfive per cent presented chest pain; 40%, echocardiographic alterations; 5%, ischemic heart disease, and 59%, electrocardiographic alterations.

Conclusions

Variations of origin of the anterior interventricular artery have a low prevalence according to reports from Chile, Colombia, and Spain. anterior interventricular artery myocardial bridges were scarce compared to other studies, suggesting better specificity of computed tomography angiography or direct dissection for these findings. The assessment of coronary permeability is graded with the thrombolysis in myocardial infarction scale; values 0 and 1 indicate occlusive lesion associated with ischemic heart disease. According to various techniques, the most frequent coronary dominance the right, followed by the left in men and balanced circulation in women.

Left septal fascicular block: Evidence, causes, and diagnostic criteria

The existence of a tetrafascicular intraventricular conduction system is widely accepted by researchers. In this review, we have updated the criteria for left septal fascicular block (LSFB) and the differential diagnosis of prominent anterior QRS forces. More and more evidence points to the fact that the main cause of LSFB is critical proximal stenosis of the left anterior descending coronary artery before its first septal perforator branch. The most important characteristic of LSFB that has been incorporated in the corresponding diagnostic electrocardiographic criteria is its transient/intermittent nature mostly observed in clinical scenarios of acute (ie, acute coronary syndrome including vasospastic angina) or chronic (ie, exercise-induced ischemia) ischemic coronary artery disease. In addition, the phenomenon proved to be phase 4 bradycardia rate dependent and induced by early atrial extrastimulus. Finally, we believe that intermittent LSFB has the same clinical significance as "Wellens syndrome" and the "de Winter pattern" in the acute coronary syndrome scenario.

Intermittent isolated anterior displacement of QRS complex - Differential diagnosis

BACKGROUND

The proposed criteria for diagnosis of left septal (middle) fascicular block (LSFB) appear to be conflicting. Moreover, it has been claimed that isolated anterior displacement (AD) of QRS complex could be a manifestation of a conduction delay of the right bundle branch, besides of LSFB. The purpose of the present study was to better define the etiology of AD through an analysis of the case reports dealing with intermittent AD, published up to now.

METHODS

PubMed search was performed to include all case reports dealing with intermittent AD occurring spontaneously, with an available 12‑lead electrocardiographic recording. Pertinent data were extracted from the papers for further analysis.

RESULTS

Eighteen case reports were found in the literature; in all cases intermittent AD was attributed to LSFB. In all cases AD was associated to changes of initial QRS forces, characterized by disappearance of septal q waves (in I and V6) and/or appearance of a small q wave in leads V1-V3. Morphology of terminal QRS forces, analysed for the first time, was unchanged in 90% of cases. Some Isolated ADs observed during induction of premature atrial extra-stimuli and recorded by vectorcardiographic tracing and some electrocardiographic leads were attributed to a conduction delay of the right bundle branch. In this case, initial QRS forces did not change and terminal QRS forces shifted to the right.

CONCLUSIONS

In the presence of intermittent isolated AD, a differential diagnosis between LSFB and a conduction delay of the right bundle branch appears to be possible by the analysis of initial and terminal QRS forces. Instead, the diagnosis of permanent LSFB remains a challenge.

Variant Angina with Spontaneously Documented Ischemia- and Tachycardia-induced "Lambda" Waves

In a patient with variant angina of the proximal left anterior descending coronary artery, myocardial ischemia changed the QRS-ST-T configurations without J-waves into those resembling "lambda" waves at maximal ST-segment elevation, and couplets or triplets of supraventricular extrasystole (SVE) changed the ischemia-induced "lambda" waves into QRS-ST-T configurations resembling a "tombstone" morphology or "monophasic QRS-ST complex." At the resolution phase of coronary spasm, the QRS-ST-T configurations returned to those without J-waves and were changed by SVE into "lambda" waves. Interestingly, neither ischemia- nor SVE-induced "lambda" waves or SVE-induced "tombstone" morphology or "monophasic QRS-ST complex" were complicated by ventricular tachyarrhythmia.

The tetrafascicular nature of the intraventricular conduction system

The existence of a tetrafascicular intraventricular conduction system remains debatable. A consensus statement ended up with some discrepancies and, despite agreeing on the possible existence of an anatomical left septal fascicle, the electrocardiographic and vectorcardiographic characteristics of left septal fascicular block (LSFB) were not universally accepted. The most important criteria requested to confirm the existence of LSFB is its intermittent nature. So far, our group has published cases of transient ischemia-induced LSFB and phase 4 or bradycardia-dependent LSFB. Finally, anatomical, anatomopathological, histological, histopathological, electrocardiographic, vectorcardiographic, body surface potential mapping, and electrophysiology studies support the fact that the left bundle branch divides into three fascicles or a "fan-like interconnected network."

Transient left septal fascicular block in a patient with stable effort angina and critical proximal obstruction of left anterior descending coronary artery

Several publications from our group and others have shown that a main cause of middle fiber block or left septal fascicular block of the left bundle of His is proximal obstruction of the left anterior descending coronary artery, before its first septal perforator branch, since this fascicle is the only one of the three fascicles irrigated exclusively by this artery. We present a case in which the phenomenon occurred transiently, causing prominent anterior QRS forces, confirmed by coronary angiography.

Transient left septal fascicular block and left anterior fascicular block as a consequence of proximal subocclusion of the left anterior descending coronary artery

The association of left anterior fascicular block (LAFB) with left septal fascicular block (LSFB) characterizes a left bifascicular block subtype rarely described in the literature, probably due to the fact that most researchers are not aware of the existence of the left septal fascicle. We describe a case with this transient intraventricular dromotropic disturbance due to left anterior descending coronary artery subocclusion.