Isolated and complicated left anterior fascicular block: a review of suggested electrocardiographic criteria

A Case With Inferior Wall Myocardial Infarction and Conduction Abnormalities: Addressing the Diagnostic Challenges

Conduction disturbances are an important complication of ST-elevation myocardial infarction (STEMI). Conduction disturbances such as fascicular blocks and bundle branch blocks are associated with alteration of QRS morphology and secondary ST-T wave changes that can influence the diagnosis of acute myocardial ischemia. We report an interesting case where a patient presented with inferior wall myocardial infarction (MI), right bundle branch block (RBBB), and left anterior hemiblock (LAHB). We discuss the challenges in diagnosing MI in such patients, including the impact of QRS changes in RBBB and LAHB, their influence on diagnosis of STEMI, and differentiation of combined first-degree AV block and bifascicular block from trifascicular block.

Electrocardiogram (ECG) patterns of left anterior fascicular block and conduction impairment in ventricular myocardium: a whole-heart model-based simulation study

Left anterior fascicular block (LAFB) is a heart disease identifiable from an abnormal electrocardiogram (ECG). It has been reported that LAFB is associated with an increased risk of heart failure. Non-specific intraventricular conduction delay due to the lesions of the conduction bundles and slow cell to cell conduction has also been considered as another cause of heart failure. Since the location and mechanism of conduction delay have notable variability between individual patients, we hypothesized that the impaired conduction in the ventricular myocardium may lead to abnormal ECGs similar to LAFB ECG patterns. To test this hypothesis, based on a computer model with a three dimensional whole-heart anatomical structure, we simulated the cardiac exciting sequence map and 12-lead ECG caused by the block in the left anterior fascicle and by the slowed conduction velocity in the ventricular myocardium. The simulation results showed that the typical LAFB ECG patterns can also be observed from cases with slowed conduction velocity in the ventricular myocardium. The main differences were the duration of QRS and wave amplitude. In conclusion, our simulations provide a promising starting point to further investigate the underlying mechanism of heart failure with LAFB, which would provide a potential reference for LAFB diagnosis.

[Non-Q-wave-electrocardiograms. Signs of earlier myocardial infarction]

An increasing number of elderly people and diabetes patients with myocardial infarction go unrecognized because of painless ischemia and regression of major Q-waves over time. An increased awareness of diagnostic electrocardiogram (ECG) abnormalities other than Q-waves should allow physicians to optimize patient management. Particularly emphasized is the R-peak delay in V6, i.e. the R-peak in V6 being later than the S-peak in V2, as a sign of masked anterior myocardial infarction and ECG findings if infarcts are masked by left ventricular hemiblocks and left bundle branch block (LBBB). In left anterior hemiblocks dramatically decreased R-waves in leads II, III and AVF in conjunction with disappearance of Q-waves in leads I and aVL help to identify posterodiaphragmatic infarction. The left posterior hemiblock is itself a potent indicator of underlying posterodiaphragmatic infarction not recognized by Q-waves. In LBBB Cabrera's sign, RSR' morphology in the left-sided or inferior leads, inverse R-progression from V1 to V3 and primary repolarization abnormalities overlying the secondary T-wave changes are specific indicators of myocardial infarction. QRS-prolongation greater than 150 ms independently identifies ventricular function impairment in chronic coronary heart disease.

Prognostic Significance of Left Anterior Hemiblock in Patients With Suspected Coronary Artery Disease

OBJECTIVES

This study was designed to assess the functional and prognostic significance of left anterior hemiblock (LAHB) in patients with no history of myocardial infarction referred for dobutamine stress echocardiography (DSE).

BACKGROUND

The significance of isolated LAHB in patients with suspected coronary artery disease (CAD) is unclear.

METHODS

We studied 1,187 patients with suspected CAD and no history of myocardial infarction who underwent DSE and were followed for occurrence of cardiac death.

RESULTS

Left anterior hemiblock was detected on baseline electrocardiogram in 159 patients (13%). Ischemia occurred more frequently in patients with LAHB (43% vs. 33%, p = 0.02). During a mean follow-up of 5.0 +/- 2.5 years, 125 patients (11%) died of cardiac causes. The annual cardiac death rate was 4.9% in patients with LAHB and 1.9% for patients without (p < 0.0001). Patients with both LAHB and an abnormal DSE had the highest annual cardiac death rate (6.3%). In a Cox multivariable analysis, independent predictors of cardiac death were age, smoking, history of heart failure, diabetes, and ischemia. Left anterior hemiblock was independently associated with increased risk of cardiac death among patients with normal DSE (hazard ratio 1.8, 95% confidence interval 1.1 to 3.8) and in patients with abnormal DSE (hazard ratio 1.7, 95% confidence interval 1.1 to 2.7).

CONCLUSIONS

In patients with suspected CAD referred for stress testing, LAHB is associated with increased risk of cardiac death. This risk is persistent after adjustment for major clinical data and abnormalities on the stress echocardiogram. Therefore, isolated LAHB should not be considered a benign electrocardiographic abnormality in these patients.

Importance of left anterior hemiblock development in inferior wall acute myocardial infarction

The aim of this study was to investigate the clinical and angiographic importance of left anterior hemiblock (LAHB) during acute inferior myocardial infarction (AIMI) by comparing patient groups with and without LAHB after AIMI. One hundred seventy-two patients (141 men and 31 women) between 28 and 84 years of age (mean 55 +/-10 years) with AIMI were included in the study. Patients were divided into 2 groups according to electrocardiogram (ECG) criteria: group I comprised 25 patients in whom ECG pattern characteristic of LAHB developed, group II comprised 147 patients without this pattern. According to the electrocardiogram, patients were placed in group I if the mean QRS axis was deviated to the left < 30 degrees in the frontal plane with the following pattern: increased S-wave voltage and decreased R-wave voltage in leads II, the appearance of a deep S-wave in lead II, and a terminal positive R-wave in lead aVR. Coronary angiography was performed within 2 weeks. A coronary stenosis was considered if the vessel diameter was narrowed by > 50%. The dominant coronary artery was classified as right or left or balanced. The left ventricular ejection fraction (LVEF) was calculated from left ventriculography. The mean age of the patients in group I was significantly higher (58 vs 54 years, p = 0.007), while the risk factors were similar in both groups. Left anterior descending (LAD) and multi-vessel coronary artery disease (CAD) were found to be significantly higher in group I compared with group 11 (80% vs 38%, p=0.0001; 84% vs 52%, p=0.001, respectively). The mean LVEF was found to be lower in group I (51% vs 56%, p=0.04). Peak creatine phosphokinase MB (CKMB) values were not different (216 vs 162 IU/L, p = 0.09). The frequency of left dominant or balanced coronary artery was determined to be higher in group I (44% vs 17%, p = 0.018). LAHB development during AIMI can be an indicator of LAD lesions, multivessel coronary artery disease, and impaired left ventricular systolic function.

Importance of left anterior hemiblock development in inferior wall acute myocardial infarction

Of the 87 consecutive patients admitted with first inferior wall acute myocardial infarction, 17 had acute left anterior hemiblock. The appearance of left anterior hemiblock identified a specific group with more extensive coronary artery disease and suggests disease of the left anterior descending coronary artery.

Limitations of the electrocardiographic diagnosis of left ventricular hypertrophy: the influence of left anterior hemiblock and right bundle branch block

We analysed the performance of the electrocardiogram in diagnosing left ventricular hypertrophy in 70 patients with isolated left anterior hemiblock and in 75 patients with right bundle branch block, either isolated (44 cases) or associated (31 cases) with left anterior hemiblock. Left ventricular hypertrophy defined as an echocardiographically determined left ventricular mass greater than 261 g in men and 172 g in women or left ventricular mass index greater than 125 g/m2 in men and 112 g/m2 in women was present in 48 subjects (57%) with isolated left anterior hemiblock and 33 subjects (44%) with right bundle branch block. In patients with isolated left anterior hemiblock the best results were obtained using the SV1 or SV2 + (RV6 + SV6) greater than 25 mm with 74% in sensitivity and 67% in specificity; the criterion SIII + (R + S) maximal in a precordial lead greater than or equal to 30 mm showed a sensitivity of 74% but a specificity of 47%. In the whole group of patients with right bundle branch block none of the criteria nor combination of criteria achieved an acceptable performance (sensitivities ranged from 17% to 41% and specificities ranged from 54% to 85%). When these patients were divided according to the presence or absence of concomitant left anterior hemiblock the electrocardiographic indexes mostly showed, in comparison to whole group, higher values in sensitivity and lower values in specificity in right bundle branch block plus left anterior hemiblock and an opposite behaviour in isolated right bundle branch block.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrocardiographic diagnosis of left ventricular hypertrophy in the presence of bundle branch block

Autopsy and echocardiographic studies indicate that ECG criteria for LVH tend to maintain their sensitivity in the presence of LBBB, with the exception of left precordial lead criteria alone. With RBBB, ECG criteria for LVH using right precordial S waves and combination criteria of right precordial S waves and left precordial R waves have a marked reduction in sensitivity, whereas left precordial R wave criteria have modestly reduced sensitivity. Limb lead criteria for LVH have increased sensitivity in the presence of RBBB and, to a lesser extent, in the presence of LBBB. Acceptable sensitivity for the diagnosis of LVH in patients with bundle branch block requires a combination of limb and precordial lead voltage criteria and/or other nonvoltage ECG criteria, since the prevalence of LVH in the presence of RBBB or LBBB appears higher than the sensitivity of individual criteria.

Electrocardiographic criteria for diagnosis of left ventricular hypertrophy in the presence of complete right bundle branch block

The usual electrocardiographic criteria recommended for left ventricular (LV) hypertrophy may be unreliable in the presence of complete right bundle branch block (BBB). Thirty-six standard electrocardiographic criteria for LV hypertrophy were evaluated in 100 patients (mean age +/- standard deviation 67 +/- 11 years) with right BBB and technically satisfactory echocardiograms. Eight additional electrocardiographic criteria derived from this study also were evaluated. LV mass index was determined from the echocardiogram using the Penn method. LV hypertrophy defined as LV mass index greater than 132 g/m2 in men and 109 g/m2 in women was present in 56 of the 100 patients. Electrocardiographic criteria with the highest sensitivity were SIII + (R + S) maximal precordial lead greater than or equal to 30 mm (sensitivity 68%), specificity 66%), left axis deviation of -30 degrees to -90 degrees (sensitivity 59%, specificity 71%) and combination of left axis deviation and SIII + (R + S) maximal precordial lead greater than or equal to 30 mm (sensitivity 52%, specificity 84%). The electrocardiographic criteria with the highest sensitivity and specificity greater than 90% were left axis deviation of -30 degrees to -90 degrees and SV1 greater than 2 mm (sensitivity 34%), point-score system, RaVL greater than 12 mm and RI + SIII greater than 25 mm (each with a sensitivity of 27%). In general, limb lead voltage criteria such as RaVL greater than 11 mm (sensitivity 29%, specificity 86%) had higher sensitivities than criteria using right precordial lead S-wave voltage criteria such as SV1 + RV5, V6 greater than 35 mm (sensitivity 2%, specificity 100%).(ABSTRACT TRUNCATED AT 250 WORDS)

Electrocardiographic detection of left ventricular hypertrophy in the presence of left anterior fascicular block

The hitherto available electrocardiographic indexes for the detection of left ventricular hypertrophy in the presence of left anterior fascicular block do not provide a reliable diagnosis. Consequently, a new index based on the behavior of the QRS complex in left anterior fascicular block in the frontal and horizontal plane was constructed and its value assessed by echocardiographic measurements. The new index SIII + (R + S) maximal precordial greater than or equal to 30 mm was applied to the electrocardiograms of 50 patients without myocardial infarction and without right bundle branch block, showing a specificity of 87%, a sensitivity of 96%, a positive predictive value of 89% and a negative predictive value of 95%. Echocardiographic measurements were used as reference. Compared with the electrocardiographic indexes used so far (which were also applied to the 50 electrocardiograms), the new index showed a comparable high specificity and a distinctly superior sensitivity. The apparent paradox--why the electrocardiographic diagnosis of left ventricular hypertrophy is easier in the presence rather than in the absence of left anterior fascicular block--is discussed.

Left anterior fascicular block and masking of inferior wall infarction

A case of inferior wall myocardial infarction that was obscured by left anterior hemiblock is presented. This report illustrates that changes in the sequence of electrical activation of the left ventricle resulting from this conduction disturbance may lead to a missed electrocardiographic diagnosis.

Left bundle branch block: a continuously evolving concept

Eppinger and Rothberger in 1909 and 1910 first acknowledged the importance of the conduction system, yet a confusion of the pattern of left bundle branch block with right bundle branch block resulted which persisted for 25 years. In left bundle branch block, right ventricular endocardial activation begins before, and is often completed before, initiation of left ventricular endocardial activation. Most likely, right to left septal activation then follows, resulting in left ventricular endocardial activation. Although it is hazardous to make definitive diagnoses of infarction in the presence of left bundle branch block, clues do exist. Benign left bundle branch block is rare; usually disease becomes manifest. Electrocardiographic criteria of hypertrophy are not as helpful in older patients with chronic left bundle branch block (mainly because of the very high incidence of left ventricular hypertrophy) as in younger patients with block of nonatherosclerotic origin. Left bundle branch block is often associated with other abnormalities of the conduction system. Fascicular blocks may mask or mimic myocardial infarction. Left posterior fascicular block is most often an indicator of left ventricular myocardial deficit if right ventricular enlargement is eliminated. Mortality is higher in patients with associated left axis deviation than in those with a normal axis, although the incidence of progression of atrioventricular (AV) block is low. In symptomatic patients with prolonged His to ventricular intervals, the incidence of progression of AV block is higher (12%). Preexisting left bundle branch block in the absence of clinical evidence of heart disease is rare, yet carries with it a slightly increased mortality. Newly acquired left bundle branch block carries a 10-fold increase in mortality; the incidence of sudden death as the first manifestation of heart disease is increased 10-fold.

Criteria for intraventricular conduction disturbances and pre-excitation. World Health Organizational/International Society and Federation for Cardiology Task Force Ad Hoc

In an effort to standardize terminology and criteria for clinical electrocardiography, and as a follow-up of its work on definitions of terms related to cardiac rhythm, an Ad Hoc Working Group established by the World Health Organization and the International Society and Federation of Cardiology reviewed criteria for the diagnosis of conduction disturbances and pre-excitation. Recommendations resulting from these discussions are summarized for the diagnosis of complete and incomplete right and left bundle branch block, left anterior and left posterior fascicular block, nonspecific intraventricular block, Wolff-Parkinson-White syndrome and related pre-excitation patterns. Criteria for intraatrial conduction disturbances are also briefly reviewed. The criteria are described in clinical terms. A concise description of the criteria using formal Boolean logic is given in the Appendix. For the incorporation into computer electrocardiographic analysis programs, the limits of some interval measurements may need to be adjusted.

Coronary angiographic significance of left anterior fascicular block during acute myocardial infarction

The clinical and angiographic significance of isolated left anterior fascicular block occurring during the early stage of acute myocardial infarction was studied in 141 consecutive patients who underwent cardiac catheterization before hospital discharge. Left anterior fascicular block occurred in 15 of the 62 patients with an anterior wall infarction and in 13 of the 79 with an inferior infarction. None of the clinical characteristics differed among patients with or without left anterior fascicular block. The number of coronary vessels with significant stenosis, the Friesinger and the Gensini scores for severity of stenosis and the ejection fraction were also similar in the two groups. Patients with left anterior fascicular block had more severe narrowing of the coronary artery supplying the infarct zone (88 +/- 21 versus 70 +/- 35%, p less than 0.001) and tended to have less developed collateral circulation (collateral score 0.7 +/- 0.8 versus 1 +/- 0.8, p = 0.10). A significant stenosis of the left anterior descending coronary artery was found as frequently in patients with as in those without left anterior fascicular block (64 versus 65%); 29% of the patients with inferior wall infarction and left anterior fascicular block had left anterior descending coronary artery stenosis compared with 47% of the patients without this conduction disturbance (no significant difference). When the infarction was located anteriorly, a significant stenosis of the proximal segment of the left anterior descending coronary artery was present in 47% of the patients with and in 45% of the patients without left anterior fascicular block.(ABSTRACT TRUNCATED AT 250 WORDS)