Left posterior hemiblock in acute myocardial infarction

Cardiopulmonary predictors of mortality in patients with COVID-19: What are the findings?

BACKGROUND

Since 2019, coronavirus disease 2019 (COVID-19) has been the leading cause of mortality worldwide.

AIMS

To determine independent predictors of mortality in COVID-19, and identify any associations between pulmonary disease severity and cardiac involvement.

METHODS

Clinical, laboratory, electrocardiography and computed tomography (CT) imaging data were collected from 389 consecutive patients with COVID-19. Patients were divided into alive and deceased groups. Independent predictors of mortality were identified. Kaplan-Meier analysis was performed, based on patients having a troponin concentration>99th percentile (cardiac injury) and a CT severity score ≥18.

RESULTS

The mortality rate was 29.3%. Cardiac injury (odds ratio [OR] 2.19, 95% confidence interval [CI] 1.14-4.18; P=0.018), CT score ≥18 (OR 2.24, 95% CI 1.15-4.34; P=0.017), localized ST depression (OR 3.77, 95% CI 1.33-10.67; P=0.012), hemiblocks (OR 3.09, 95% CI 1.47-6.48; P=0.003) and history of leukaemia/lymphoma (OR 3.76, 95% CI 1.37-10.29; P=0.010) were identified as independent predictors of mortality. Additionally, patients with cardiac injury and CT score ≥ 18 were identified to have a significantly shorter survival time (mean 14.21 days, 95% CI 10.45-17.98 days) than all other subgroups. There were no associations between CT severity score and electrocardiogram or cardiac injury in our results.

CONCLUSIONS

Our findings suggest that using CT imaging and electrocardiogram characteristics together can provide a better means of predicting mortality in patients with COVID-19. We identified cardiac injury, CT score ≥18, presence of left or right hemiblocks on initial electrocardiogram, localized ST depression and history of haematological malignancies as independent predictors of mortality in patients with COVID-19.

Left posterior fascicular block, state-of-the-art review: A 2018 update

We conducted a review of the literature regarding epidemiology, clinical, electrocardiographic and vectorcardiographic aspects, classification, and differential diagnosis of left posterior fascicular block.

Isolated left posterior fascicular block (LPFB) is an extremely rare finding both in the general population and in specific patient groups. In isolated LPFB 20% of the vectorcardiographic (VCG) QRS loop is located in the right inferior quadrant and when associated with right bundle branch block (RBBB) ≥40%.

The diagnosis of LPFB should always consider the clinical aspects, because a definite diagnosis cannot be made in the presence of right ventricular hypertrophy (RVH) (chronic obstructive pulmonary disease (COPD)/emphysema), extensive lateral myocardial infarction (MI) or extremely vertical heart.

Intermittent LPFBs are never complete blocks (transient or second degree LPFB) and even in the permanent ones, one cannot be sure that they are complete. When LPFB is associated with RBBB and acute inferior MI, PR interval prolongation is very frequent.

Prognostic implications of intraventricular conduction delays in a general population: the Health 2000 Survey

AIMS

We examined the prognostic impact of eight different intraventricular conduction delays (IVCD) in the standard electrocardiogram (ECG) in a community cohort.

METHODS AND RESULTS

Data were collected from 6299 Finnish individuals. During a mean 8.2 years (interquartile range 8.1 to 8.3) of follow-up 640 subjects died (10.2%); 277 (4.4%) were cardiovascular deaths. For both sexes, all-cause and cardiovascular mortality was higher in subjects with IVCD than in those without. In Cox regression analysis after adjustment for age and gender, the hazard ratio for cardiovascular mortality for non-specific IVCD was 4.25 (95% confidence interval [CI] 1.95-9.26, P < 0.0001) and for left bundle branch block (LBBB) 2.11 (95% CI 1.31-3.41, P = 0.002). Right bundle branch block (RBBB) was not related to additional mortality, while incomplete RBBB (IRBBB) presented a hazard ratio of 2.24 (95% CI 1.064-4.77, P = 0.036).

CONCLUSIONS

In the general population, non-specific IVCD, LBBB, and IRBBB were associated with increased relative risk for all-cause and cardiovascular mortality. RBBB did not have an impact on cardiovascular mortality either in subjects with or without previous heart disease.

Hemiblocks Revisited

The trifascicular nature of the intraventricular conduction system and the concept of trifascicular block and hemiblock were described by Rosenbaum and his coworkers in 1968. Since then, anatomic, pathological, electrophysiological, and clinical studies have confirmed the original description and scarce advances have been developed on the subject. In the present study, we attempt to review and redefine reliable criteria for the electrocardiographic and vectorcardiographic diagnosis of left anterior and posterior hemiblock. One of the most important problems related to hemiblocks is that they may simulate or conceal the electrocardiographic signs of myocardial infarction or myocardial ischemia and may mask or simulate ventricular hypertrophy. Illustrative examples of these associations are shown to help the interpretation of electrocardiograms. The incidence and prevalence of the hemiblocks is presented based on studies performed in hospital patients and general populations. One of the most common causes of hemiblocks is coronary artery disease, and there is a particularly frequent association between anteroseptal myocardial infarction and left anterior hemiblock. The second most important cause is arterial hypertension, followed by cardiomyopathies and Lev and Lenègre diseases. The hemiblocks may also occur in aortic heart disease and congenital cardiopathies. Left anterior hemiblock is more common in men and increases in frequency with advancing age. Evidence is presented regarding the relationship of spontaneous closure of ventricular septal defects, which may explain the finding of this and other conduction defects in young populations. Isolated left anterior hemiblock is a relatively frequent finding in subjects devoid of evidence of structural heart disease. Conversely, isolated left posterior hemiblock is a very rare finding; its prognostic significance is unknown and is commonly associated with right bundle-branch block. The most remarkable feature of this association is that the prognosis is much more serious with a great propensity to develop complete atrioventricular block and Adams-Stoke seizures.

Isolated left posterior fascicular block: a reliable marker for inferior myocardial infarction and associated severe coronary artery disease

The electrocardiographic (ECG) pattern of isolated left posterior fascicular block (LPFB) is a rare condition. It seems that true LPFB is often not recognized, whereas in cases of simple QRS axis of +60 degrees to +100 degrees in the frontal plane, the diagnosis of LPFB is made erroneously. Both facts rely on controversial and partially misleading opinions in the literature. Therefore, a retrospective and prospective study was performed in order to determine the prevalence of LPFB and to correlate its presence to the underlying disease. Retrospective study: Of a cohort of 830 patients referred in 1988 to a cardiologic laboratory for invasive investigation of certain or suspected coronary artery disease (CAD), 163 patients had an old inferior myocardial infarction (IMI). Nine patients (5.5%) showed the typical pattern of LPFB; eight of these had three-vessel disease. The diagnosis of IMI had been made only in one case before entry of the patient into the hospital, since LPFB generally masks IMI. Prospective study: 2502 ECGs were investigated, 1710 from a department of cardiology and 792 from two departments of internal medicine. Six LPFBs were detected (0.24%), all associated with IMI and four of them with three-vessel CAD. It is concluded that LPFB is a rare but clinically important intraventricular conduction disturbance. Its appearance is reliably connected with IMI and generally reflects severe three-vessel CAD, requiring invasive investigation.

Conduction defects in acute myocardial infarction in the Chinese in Hong Kong

In order to delineate the conduction defects complicating acute myocardial infarction in the Chinese, 636 Chinese patients admitted into one of the three medical units of a general hospital in Hong Kong in the period 1973-80 were reviewed. A relatively high incidence of conduction defects was observed, including atrioventricular block (11.3%), right bundle branch block (12.7%) and left bundle branch block (3.3%). Right bundle branch block (whether isolated or combined with left fascicular block) and atrioventricular block complicating anterior Q-wave infarction were ominous, with a high incidence of pump failure, cardiogenic shock and cardiac arrhythmias. These are markers of massive infarction. Atrioventricular and bundle branch blocks complicating inferior Q-wave infarction were benign. Left bundle branch block appeared to be a more chronic lesion, with moderate mortality, and isolated left anterior hemiblock did not adversely affect the short-term outcome. These results conform well to the patterns seen in Western series. The high incidence of conduction defects, in particular right bundle branch block and atrioventricular block complicating anteroseptal infarction, indicates a more serious clinical spectrum of acute myocardial infarction in the Chinese, and could have contributed to a higher hospital mortality in the Chinese series.

The Birmingham Trial of permanent pacing in patients with intraventricular conduction disorders after acute myocardial infarction

Patients surviving 2 weeks after myocardial infarction who had persistent conduction disorder (right bundle branch block alone or associated with left anterior or posterior hemiblock [LPH] or LPH alone) were allocated at random to permanent pacing or control groups. Throughout follow-up, up to 5 years, there was no significant difference in survival: at 2 years 14 of 23 (61%) of paced patients had died compared with 11 of 27 (41%) control patients. Progression of conduction disorder was not observed and measurement of infranodal conduction time (HV interval) did not predict outcome. Ventricular tachyarrhythmias were an important cause of death in these patients and pacing appears to offer no benefit.

Right axis deviation in acute myocardial infarction. Clinical significance, hospital evolution, and long-term follow-up

The incidence, in-hospital evolution, and long-term follow-up were studied in patients who developed acute deviation of the mean (frontal) QRS axis to the right during an acute myocardial infarction (AMI). Among 3,160 patients evaluated, 13 (0.41 percent) developed left posterior hemiblock (LPHB) and 57 (1.8 percent) developed an incomplete form of LPHB, the right axis deviation group (RAD). Patients in the LPHB group had a statistically significant higher incidence of in-hospital morbidity (69 percent incidence of congestive heart failure) and mortality (38.5 percent). Follow-up revealed a statistically significant higher incidence of cardiac symptomatology (angina pectoris and congestive heart failure) in the RAD group than in the control group, mainly in patients in whom RAD persisted for more than 24 hours. Patients developing LPHB during AMI constitute a high risk population with a high incidence of morbidity and mortality. Patients developing RAD constitute an intermediate group (between the LPHB and the control group) characterized by a high incidence of cardiac symptoms at the time of follow-up.

Histopathologic correlates of left posterior fascicular block

Thirteen hearts from subjects (10 male, 3 female; mean age 65 years) with left posterior fascicular block were studied. Left posterior fascicular block was associated with right bundle branch block in nine cases and alternated with left anterior fascicular block in three. In nine of the patients, the conduction disorders were observed during an episode of acute myocardial infarction. Of these nine patients, four showed interruptive lesions at the level of the posterior radiation of the left bundle or of the posterior portion of the main left bundle branch. Two were found to have severe alterations scattered throughout the left bundle branch system: One of them had alternating left anterior and left posterior fascicular block; and the other manifested complete heart block in the course of her illness. No interruptive changes of the posterior fibers were found in three cases in which the heart was obtained early after death. All 9 patients had severe coronary artery disease (six had triple vessel disease and three of the six had a left main coronary arterial stenosis or obstruction; two patients had double vessel disease). Among the four patients with chronic left posterior block, three were found to have heavy calcifications of the left side of the cardiac skeleton; the remaining one had diphtheritic myocarditis. All had major alterations of the left-sided conduction system that were consistently maximal at the level of the posterior fibers or posterior portion of the main left bundle branch. In two of these patients scattered lesions were found throughout the left bundle branch fibers; one had alternating left anterior and left posterior fascicular block and the other had complete heart block. In general, the alterations underlying left posterior fascicular block were less widely spread than in left anterior fascicular block; however, they were more severe and more proximally located.

The concept of trifascicular intraventricular conduction: historical aspects and influence on contemporary cardiology

The efforts of Mauricio Rosenbaum and his co-workers in putting together the anatomic and electrocardiographic correlations that led to the development of the concept of trifascicular intraventricular conduction have had a major impact on electrocardiography. Perhaps the greatest testimony to their contributions is the large number of related publications by many authors since the printing of Los Hemibloqueos more than 10 years ago.

Spatial Frank vectorcardiogram in left posterior fascicular block. Criteria and correlation with clinical and electrocardiographic data

Computer processing of spatial QRS parameters (Frank vectorcardiogram) was used to study left posterior fascicular block. The best set of vectorcardiographic criteria was sought in order to characterise the classic pattern of left posterior fascicular block. Using these criteria, 18 cases were selected from a group of 4600 patients and 340 healthy subjects; isolated left posterior fascicular block was seen in 10 cases, and was associated with right bundle-branch block in 8 cases. It is shown that some external factors can influence the aspect of the spatial QRS loop in left posterior fascicular block: cardiomegaly tends to produce a superior displacement of the main QRS forces: right bundle-branch block enhances the superior displacement of the initial forces and shifts the main QRS forces more anteriorly and to the right. The 'masquerading effect' of the left posterior fascicular block on a concomitant inferior myocardial infarct was also shown. The most important diagnostic feature was the opposite direction of the initial forces (left anterosuperior) and the maximal vector (right postero-inferior): the angle between these two vectors averaged 152 degrees. Other criteria, such as the direction of rotation or the axis of the frontal loop, the vertical direction of the spatial loop, the presence of a Q wave in leads II, III, and aVF of the electrocardiogram, are not mandatory for the diagnosis of left posterior fascicular block.

Histopathology of conducting system in left anterior hemiblock

In 8 cases of left anterior hemiblock, combined with right bundle-branch block in 7, serial sections of the conducting system of the heart were examined histologically. In all cases there were pathological changes in the left bundle-branch but the anterior part of it was predominantly affected in only 2 cases. Acute changes were found in 6 cases of early myocardial infarction, and fibrosis in 2 cases of chronic heart disease. Reversible lesions may have a pathogenetic role in acute hemiblocks. The right bundle-branch was disrupted by fibrosis in 6 of the 7 cases with right bundle-branch block, and minor changes in the AV node were observed in 1. The widespread damage to the left bundle-branch in the majority of the present cases does not seem to be consistent with the limited clinicopathological correlation implied by the terms anterior fascicular block or hemiblock. Other cardiac lesions within the left bundle-branch and outside it may contribute to this electrocardiographic pattern.