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Many advances in the knowledge of medical science are due to the observation of an unknown phenomenon that remains an open question. A plausible hypothesis must be demonstrated and proved through a scientific method in order to be accepted by the scientific community and the same results must be reached by following either the same or different techniques. The original case described by Rosenbaum MB et al., in this review triggered a series of anatomic and physiologic investigations with clinical and experimental observations that supported the trifascicular nature of the intraventricular conduction system of the heart and the concept of hemiblocks. The recognition and description of the left fascicular blocks made by the Argentinian School of Electrocardiology bridged an important gap in electrocardiography and many electrocardiograms that could not be explained until that moment could finally be understood. This review intends to redefine reliable criteria for the electrocardiographic and vectorcardiographic diagnosis of left fascicular blocks [hemiblocks]. The anatomy of the left bundle branch is also discussed to better understand the incidence, prevalence, clinical significance and main causes of left anterior and left posterior hemiblock either isolated or associated with right bundle branch block. This review offers the reader a reappraisal of the trifascicular nature of the intraventricular conduction system regarding the anatomy of the left bundle branch system and its pathophysiological and clinical significance.

Beside cardiac chamber enlargement, abnormalities in current flow pattern (conduction pathway) are equally important. Delay in intraventricular conduction leads to bundle branch and fascicular blocks. Electrocardiogram is the only diagnostic technique which is of great assistance in detecting these blocks. Importance of these blocks increases when these are associated with severe cardiac disease. Different electrocardiographic changes depicting right bundle branch block, left bundle branch block, and fascicular block have been detailed in this chapter.

Background The aim was to explore and improve the confidence levels of foundation doctors at interpreting ECGs in stressful situations. The Legitimate Peripheral Participation education theory is significant in the learning process surrounding simulation days as well as overall foundation training. Delegates are encouraged to identify learning as a contextual process achieved through participation in a community practice.1 The simulation day exaggerates this process and heightens the pressures usually encountered. Summary of work A questionnaire was distributed exploring confidence levels at interpreting key ECG rhythms, before and after their simulation days. Teaching on reading ECGs was provided. The simulation days went ahead as usual with multiple time pressured scenarios being completed either individually or as a team. Another questionnaire was distributed one month after the simulation session. For the second cycle the information sheet was provided on the online classroom as pre-reading material. Allowing the delegates to use the simulation day and teaching to consolidate their knowledge. The retention of learning from simulation days is known to be poor, because many of the scenarios are not managed solely by foundation doctors in clinical practice. Summary of results In cycle one, all delegates initially showed moderate confidence at identifying most of the ECG rhythms, with the least confidence shown for conduction abnormalities such as fascicular block. After the session, all delegates showed increased levels of confidence for all rhythms suggested. A further improvement was shown on the one-month post simulation day survey. In cycle two, the pre-simulation data showed least confidence at interpreting Atrial Flutter and Fascicular blocks. Once again the post simulation survey showed a general increase in confidence intervals at interpreting most of the ECG rhythms suggested, however the lack of confidence at recognising Fascicular blocks and Atrial Flutter persisted. The one-month post simulation data, however, showed significant improvement in all areas, compared to post simulation data, including the above mentioned conduction rhythms. Both cycles had poor response rates to the one-month post simulation questionnaire, with a 30% response rate in cycle one and 12.5% rate in cycle 2. Discussion and conclusion The ongoing increase in the confidence levels of foundation doctors at interpreting ECGs in stressful situations demonstrates that the teaching and learning during the simulation days allowed delegates to self-evaluate how well they were contributing to practice through their efforts. The aim for future works is to increase the power of the results by improving response rates. Reference Floding M, Sweir G. Legitimate Peripheral Participation: Entering a Community of Practice. Reflective Practice 2011; 31: 193–204.

Electrocardiograms (ECGs) have been employed to medically evaluate participants in population-based studies, and ECG-derived predictors have been reported for incident atrial fibrillation (AF). Here, we reviewed the status of ECG in predicting new-onset AF. We surveyed population-based studies and revealed ECG variables to be risk factors for incident AF. When available, the predictive values of each ECG risk marker were calculated. Both the atrium-related and ventricle-related ECG variables were risk factors for incident AF, with significant hazard risks (HRs) even after multivariate adjustments. The risk factors included P-wave indices (maximum P-wave duration, its dispersion or variation and P-wave morphology) and premature atrial contractions (PACs) or runs. In addition, left ventricular hypertrophy (LVH), ST-T abnormalities, intraventricular conduction delay, QTc interval and premature ventricular contractions (PVCs) or runs were a risk of incident AF. An HR of greater than 2.0 was observed in the upper 5th percentile of the P-wave durations, P-wave durations greater than 130 ms, P-wave morpholyg, PACs (PVCs) or runs, LVH, QTc and left anterior fascicular blocks. The sensitivity , specificity and the positive and negative predictive values were 3.6-53.8%, 61.7-97.9%, 2.9-61.7% and 77.4-97.7%, respectively. ECG variables are risk factors for incident AF. The correlation between the ECG-derived AF predictors, especially P-wave indices, and underlying diseases and the effects of the reversal of the ECG-derived predictors on incident AF by treatment of comorbidities require further study.

Background— Definitive diagnosis of bilateral bundle-branch delay/block may be made when catheter-induced right bundle-branch block (RBBB) develops in patients with baseline left bundle-branch (LBB) block. We hypothesized that a RBBB pattern with absent S waves in leads I and aVL will identify bilateral bundle-branch delay/block. Methods and Results— Fifty patients developing transient RBBB pattern in lead V1 during right heart catheterization were studied. Patients were grouped according to whether the baseline ECG demonstrated a normal QRS, left fascicular blocks, or LBB block pattern. The RBBB morphologies in each group were compared. The prevalence of bilateral bundle-branch delay/block pattern was examined in our hospital ECG database. All patients with baseline normal QRS complexes (n=30) or left fascicular blocks (4 anterior, 5 posterior) developed a typical RBBB pattern. Among the 11 patients with a baseline LBB block pattern, 7 developed an atypical RBBB pattern with absent S waves in leads I and aVL and the remaining 4 demonstrated a typical RBBB. The absence of S waves in leads I and aVL during RBBB was 100% specific and 64% sensitive for the presence of pre-existing LBB block. Among the consecutive 2253 hospitalized patients with RBBB, 34 (1.5%) had the bilateral bundle-branch delay/block pattern. Conclusions— An ECG pattern of RBBB in lead V1 with absent S wave in leads I and aVL indicates concomitant LBB delay. Pure RBBB and bifascicular blocks are associated with S waves in leads I and aVL.

Lead aVR is the only lead in the surface ECG that does not face the “typically” relevant walls of the left ventricle. Historically, its value has been neglected most likely due to its unusual configuration and direction, which appeared to have little correlation with other more congruous and easily diagnostic frontal leads. The isolation of the unipolar leads in the Standard surface ECG presentation may also have played an important role. Even with this “unfair” neglect, we know nowadays that it is very sensitive to locate obstructed epicardial coronary arteries. Besides helping distinguishing the culprit lesion of an infarct, lead aVR also helps recognizing other conditions that could be of clinical significance such as pericarditis, Brugada syndrome, fascicular blocks of the right branch, ectopic left atrial rhythms, etc. The purpose of this review is to revise the clinical value of lead aVR in the recognition of frequent and not so frequent clinical conditions. Ann Noninvasive Electrocardiol 2011;16(3):295–302

There are several papers in literature that prove in a conclusive and incontestable way, that the left branch of the His bundle, in most instances (85% of the cases) splits into three fascicles of variable morphological pattern, and not into two: left anterior fascicle (LAF), left posterior fascicle (LPF), and left septal fascicle (LSF). The abovementioned papers have anatomical, histological, anatomo-pathological, electrocardiographic, and vectocardiographic, body surface potential mapping or ECG potential mapping and electrophysiological foundation. Additionally, the mentioned papers have been performed both in animal models (dogs) and in the human heart. Several clinical papers have shown that the left septal fascicular block (LSFB) may occur intermittently or transitorily as a consequence of a temporary dromotropic alteration, constituting an aberrant ventricular conduction, rate-dependent or by the application of atrial extra-stimuli, or naturally during the acute phase of infarction when this involves the anterior descending artery, before the septal perforating artery that supplies the central portion of the septum, where the mentioned LSF runs. The ECG/VCG manifestation of LSFB consists in anterior shift of electromotive forces, known as Prominent Anterior Forces (PAF), which can hardly be diagnosed in the clinical absence of other causes capable of causing PAF, such as the normal variant by counterclockwise rotation of the heart on its longitudinal axis, in right ventricular enlargement, in the dorsal or lateral infarction of the new nomenclature, in type-A WPW, in CRBBB, and others. In this historical manuscript, we review in a sequential fashion, the main findings that confirmed the unequivocal existence of this unjustifiably "forgotten" dromotropic disorder. In the developed countries, its most important cause is coronary insufficiency, particularly the proximal involvement of the left anterior descending coronary artery, and in Latin America, Chagas disease.

Mithilesh K. Das, Douglas P. Zipes 486 pages. Philadelphia, PA: Elsevier Saunders, 2012. $77.99 ISBN 978-1-4377-2029-7 This book is a compendium of hundreds of examples of surface ECGs intermixed with other figures of ladder diagrams, intracardiac electrophysiological recordings, anatomic figures, and CARTO 3-dimensional maps. Each chapter starts with a brief review followed by multiple, clear examples of various arrhythmias. The book is a companion to Cardiac Electrophysiology: From Cell to Bedside. 1 There are 13 chapters, >450 figures, and 486 pages to the book. Chapter 1 reviews important concepts such as bundle-branch blocks and fascicular blocks, including diagnostic criteria in well-organized tables in addition to 47 clear ECG examples. Some of the better ECG figures include premature atrial complexes initiating atrial fibrillation, rate-related right bundle- branch block, atrial tachycardia …

There is an increasing need for nurses to interpret a 12-lead electrocardiogram, both in critical care units and in other areas. This can be a challenging task, especially in the presence of hypertrophies, bundle-branch blocks, and fascicular blocks. This article reviews the pathophysiology of intraventricular blocks and hypertrophy, characteristics found in the 12-lead electrocardiogram, and discusses what the significance of these findings may be.

Atrioventricular (AV) block is not only linked to some important electropathophysiologic mechanisms such as conduction slowing and escape rhythm, but also to typical ECG patterns such as Wenckebach period or Mobitz block, and to other potential precursors of complete AV block such as fascicular blocks and their combinations. All in all, AV block in its various degees is of great clinical importance.

Kearns-Sayre syndrome is the triad of progressive external ophthalmoplegia, pigmentary retinopathy, and complete AV block. The etiology is unknown, but is thought to be due to a mitochondrial DNA deletion. Reported electrocardiographic abnormalities include first-degree AV block, fascicular blocks, and complete heart block, as well as non-specific S-T segment changes and T wave abnormalities, but has not included sinus node dysfunction. We report a case with episodes of sinus arrest in an asymptomatic patient with Kearns-Sayre syndrome resulting in pauses lasting up to 6 seconds.

I ntroduction of the concept of hemiblock of the left bundle branch system’ (less erroneously termed “fascicular block”) was a pioneering effort that enabled electrocardiographers to think clinically in terms of the pathophysiology of conduction system lesions. Few would dispute that blocks can exist in particular parts of the conduction system, with or without accompanying myocardial lesions. However, it is questionable that one can securely deduce from the ordinary electrocardiogram the presence of such specific forms of interrupted conduction and highly questionable that their anatomic locations can be predicted. Much evidence now exists that the left bundle system only rarely approaches being biiascicular2~3 (negating any idea of hemiblock, which implies a bifascicular system); although an effective septal ramus can be demonstrated,4 even a trifascicular system remains too simplistic when d&sections of the left bundle system consistently show broader and narrower portions connected by loops and bridges, almost always among an assortment of fan-like smaller fascicles.2-5 These complex arrangements are further confounded by great intersubject variability.2,4 Moreover, tine dissection limited to the left bundle conducting system in patients whose electrocardiograms show either leftor right-axis deviation necessary to even consider a fascicular block from the electrocardiogram disclose a plethora of lesions, most quite proximal to the proposed anterior and posterior major fasci~les.**~ Furthermore, many patients with appropriate axis deviations have additional or isolated lesions of the myocardium both adjacent to and remote from the bundle system.4Jj Long ago, for example, Grant6 showed that a myocardial lesion in an appropriate location could slow intramyocardiil conduction so that the terminal portion of the QRS would be generated in such slowed areas, skewing the net QRS vector toward them. Thus, an. anterolateral infarct, for example, would tend to generate a left-axis deviation on this basis with or without involvement of the conducting system. Reeent eAeneer Phase analysis using a variety of approaches-is has found wide clinical and investigative application, primarily as a method for evaluating ventricular regional wall motion abnormalities in the diagnosis of ischemic heart disease. New evidence bearing on putative fascicular block has appeared using phase image characterization of ventricular contraction in patients with a range of left-axis deviation and left-axis deviation combined with right bundle branch block.”

Following electrocardiographic analysis, isolated or combined blocks in the intraventricular trifascicular system including predivisional left bundle branch block with left posterior hemiblock in Nigerians are presented and the underlying causes reviewed. The rarity of complete heart block, despite the not uncommon fascicular blocks, is of interest and may be related to the population age structure considering the invariably slow rate of degeneration of conduction fibres in the system.

When Rosenbaum et al. (1968) decided upon the criteria for the diagnosis of left anterior hemiblocks, he remarked that it was difficult to draw a precise dividing line between ordinary left axis deviation and left axis deviation due to left anterior hemiblocks. The existence of different degrees of left anterior hemiblocks has been recognized from the outset: different left anterior hemiblock patterns may occur, for example in the same patient, during aberrant ventricular conduction of premature supraventricular beats induced experimentally by programmed atrial stimulation (Kulbertus et al., 1976). As suggested by Durrer et al. (1966) the forme fruste endocardial cushion defect can produce left axis deviation probably due to abnormal development of the conducting system. The left posterior hemiblock as well as the left septal fascicular block do not behave as clearcut phenomena, and the different authors agree on their deceptive and non-specific nature (Rosenbaum et al., 1972); however in the majority of cases the histological findings are consistent with the known electrocardiographic criteria (Demoulin and Kulbertus, 1972).

An analysis of 69 cases of bifascicular and trifascicular types of intraventricular conduction disturbances in myocardial infarction is presented. Complications, causes of death and the follow-up of unpaced cases for a year have been recorded. Pump failure and severe degrees of blocks with consequent ventricular asystole are the important causes of death. Recurrent pump failure with occasional fatal outcome is more common in cases with RBBB and LAH than in other types of blocks.

1. Anatomy of intraventricular conduction system.- 2. Physiology of ventricular excitation.- 3. Bundle branch blocks.- 4. Fascicular blocks.- 5. Bifascicular and trifascicular blocks.- 6. Peripheral blocks.- 7. Intraventricular conduction disturbances in congenital heart disease and following cardiac surgery.- 8. Intraventricular conduction disturbances in acute myocardial infarction Clinical significance.- 9. Intraventricular conduction disturbances coexisting with healed myocardial infarction. Diagnostic problems.- 10. Intermittent intraventricular blocks.- 11. Prognostic value of HV interval in patients with intraventricular conduction disturbances.- 12. Noninvasive recording of His-Purkinje activity.- 13. Effect of anthiarrhythmic drugs on intraventricular conduction.- 14. Pacemaker therapy in patients with intraventricular disturbances.

The concept of continued and progressive coronary care rather than intermediate coronary care is proposed. At each clinical stage the patient may be at risk and his management needs to be planned appropriately--prevention of the development of coronary disease, prehospital care, acute coronary care, subacute coronary care, and late hospital stay. Meticulous continued care once the patient leaves the hospital and returns home may be needed for a long time. Although the benefit of an intermediate coronary care unit has not yet been proved, significant patient risk continues beyond 12 days of hospital admission. High risk patient subsets are emerging requiring careful continued monitoring and the ability to undertake emergency measures as needed, and this is particularly so in patients suffering large anterior infarction, in those with infarction associated with cardiac failure, when infarction is associated with fascicular block and other types of conduction disturbances, and in patients who continue with rhythm disturbances after their admission to the hospital. Electrocardiograph leads III and VI displayed simultaneously should be routinely monitored in patients with fascicular blocks and acute anterior infarction as a guide to instituting prophylactic transvenous pacemaking. The continuation of intensive patient care and monitoring beyond the usual 2 to 5 days in a coronary care unit allows early mobilisation of patients in safety, thus speeding their ultimate rehabilitation. There is, as yet, no satisfactory study documenting the need for intermediate coronary care units, but much presumptive evidence is available to indicate that this is so. A carefully controlled randomised study would be invaluable.

The effects of resection of post-ischemic ventricular scars on the electrocardiogram have been studied in 29 patients. No change occurred in atrial rhythm, P wave morphology, and A-V conduction. Fascicular blocks developed postoperatively in five patients. These were attributed to surgical trauma. Changes in mean frontal plane QRS axis were noted in 25 of 29 patients. There was no correlation between postoperative shifts in QRS axis and preoperative QRS axis, calculated scar size, or ventricular end-diastolic volume. No significant postoperative change was observed in Q waves or S-T segment deviation. It is concluded that electrocardiographic changes following scar resection occur randomly in a minority of patients. The presence of several unquantified factors makes it difficult to evaluate the post-resection electrocardiogram.

To determine the factors associated with persistent and transient fascicular blocks, 144 patients with Q-wave anterior wall acute myocardial infarction (AMI) were studied. Thirty-three patients had new onset of fascicular block considered to be a consequence of AMI. Multivariate analysis using 16 clinical variables revealed that the number of asynergic segments, serum potassium level and pericardial rub were significant factors related to the occurrence of fascicular block. Among the 33 patients with fascicular block, 18 had persistent (group 1) and 15 had transient (group 2) fascicular blocks. When the 2 groups with fascicular block were compared, group 1 had significantly more asynergic segments than group 2 (4.7 ± 1.2 vs 3.7 ± 1.6, respectively), whereas pericardial rubs were observed significantly more in group 2 (67%) than in group 1 (28%). Therefore, the inflammatory process of AMI was 1 of the mechanisms related to the occurrence of a transient fascicular block and a more extensive myocardial necrosis was associated with a persistent fascicular block.

Two hundred and four patients were monitored during oral surgery using three surface e.c.g. leads simultaneously. In nine patients, sustained supraventricular tachycardia was observed during surgical stimulation. The role of sympathetic stimulation and halothane anaesthesia in producing arrhythmia is discussed.