Left anterior hemiblock obscuring the diagnosis of right bundle branch block in acute myocardial infarction

Conduction Disorders in the Setting of Acute STEMI

ST-elevation myocardial (STEMI) is frequently associated with conduction disorders. Regional myocardial ischemia or injury may affect the cardiac conduction system at various locations, and neural reflexes or changes in the balance of the autonomous nervous system may be involved. Sinoatrial and atrioventricular blocks are more frequent in inferior than anterior STEMI, while new left anterior fascicular block and right bundle branch block indicate proximal occlusion of the left anterior descending coronary artery. New left bundle branch block is associated with multi-vessel disease. Most conduction disorders associated with STEMI are reversible with reperfusion therapy, but they may still impair prognosis because they indicate a large area at risk, extensive myocardial infarction or severe coronary artery disease. Acute STEMI recognition is possible in patients with a fascicular or right bundle branch block, but future studies need to define the cut-off values for ST depression in the leads V1-V3 in inferolateral MI and for ST elevation in the same leads in anterior STEMI. In the left bundle branch block, concordant ST elevation is a specific sign of acute coronary artery occlusion, but the ECG feature has low sensitivity.

Rescue Percutaneous Coronary Intervention for a Lethal "Jailed" Septal Perforator Branch to Resolve Delayed Complete Atrioventricular Block

Delayed complete atrioventricular (AV) block associated with an occluded septal perforator branch (SPB) is an uncommon complication after performing percutaneous coronary intervention (PCI) for the left anterior descending coronary artery (LAD). Here we report the case of a 74-year-old man who underwent elective PCI for proximal LAD complicated with occlusion of the first major SPB and developed a complete AV block 78 hours after PCI was performed. The patient received a temporary transvenous pacemaker via the jugular vein and successfully underwent balloon angioplasty of the lethal "jailed" SPB, resulting in recovery from the complete AV block. Permanent pacemaker implantation was avoided. Our findings indicate the importance of postprocedural monitoring and consideration of rescue PCI for an occluded SPB in cases of complicated AV conduction disturbances.

Masquerading bundle branch block: a variety of right bundle branch block with left anterior fascicular block

The so-called 'masquerading' type of right bundle branch block is caused by the simultaneous presence of a high-degree left anterior fascicular block often accompanied with severe left ventricular enlargement and/or fibrotic block in the anterolateral wall of the left ventricle. These conditions tend to reorient the terminal electrical forces of the QRS complex towards the left and upwards, in such a way that the characteristic slurred S wave in lead I becomes smaller or even disappears. In many cases of standard masquerading right bundle branch block, a small Q wave in lead I is present due to the initial forces of the left anterior fascicular block, which are oriented rightwards and inferiorly. However, in some cases, the Q wave in lead I also vanishes, and the mimicking of a left bundle branch block becomes perfect in standard leads. This is commonly associated with an inferior myocardial infarction or severe inferior fibrosis in cardiomyopathies. The typical QRS changes of right bundle branch block may eventually be concealed even in the right precordial leads; under such circumstances, the ECG diagnosis may be mistaken and the right bundle branch block totally missed. The masquerading right bundle branch block carries a poor prognosis, since it always implies the presence of a severe underlying heart disease.

Atrial fibrillation associated with exogenous subclinical hyperthyroidism, changing axis deviation, troponin-I positive and without acute coronary syndrome

Changing axis deviation has been rarely reported also during atrial fibrillation or atrial flutter. Changing axis deviation has been also rarely reported during acute myocardial infarction associated with atrial fibrillation or at the end of atrial fibrillation during acute myocardial infarction. Subclinical hyperthyroidism is an increasingly recognized entity that is defined as a normal serum free thyroxine and free triiodothyronine levels with a thyroid-stimulating hormone level suppressed below the normal range and usually undetectable. It has been reported that subclinical hyperthyroidism is not associated with coronary heart disease or mortality from cardiovascular causes but it is sufficient to induce arrhythmias including atrial fibrillation and atrial flutter. It has also been reported that increased factor X activity in patients with subclinical hyperthyroidism represents a potential hypercoagulable state. Serum troponin-I is a sensitive indicator of myocardial damage but abnormal troponin-I levels have been also reported without acute coronary syndrome and without cardiac damage. Abnormal troponin-I levels after supraventricular tachycardia have been also reported. We present a case of changing axis deviation in a 49-year-old Italian man with atrial fibrillation, exogenous subclinical hyperthyroidism and troponin-I positive without acute coronary syndrome. Also this case focuses attention on changing axis deviation, on subclinical hyperthyroidism and on the importance of a correct evaluation of abnormal troponin-I levels.

Ischemic blocks during early phase of anterior myocardial infarction: correlation with ST-segment shift

Of 760 consecutive cases with anterior acute myocardial infarction (AMI), 55 developed acute bundle-branch block (BBB), fascicular block, or high-degree atrioventricular block during the hyperacute ECG stage of AMI. According to the direction of the ST segment during the acute ischemic episode, patients were divided into two groups. Group A consisted of 32 patients who developed BBB during ST-segment elevation, positive T wave, and absent or minimal Q wave. Group B consisted of 23 patients who developed BBB during ST-segment depression and evolved into anterior AMI. Group A was characterized by a higher incidence of right BBB and left anterior hemiblock [91% vs. 26% and 56% vs. 13%, respectively (p less than 0.005)]. Group B was characterized by a higher incidence of left BBB and left posterior hemiblock [57% vs. 9% and 26% vs. 12%, respectively (p less than 0.001)]. The BBB was transient (disappearing within hours to one day) in 14 patients in Group A and in 5 patients in Group B. The incidence of progression to high-degree atrioventricular block was almost equal in the two groups (25% and 26%). The mortality rate was very high in both groups, but higher in Group B [74% vs. 59% (p = NS)] especially in those with LBBB (85%). Most patients died on the day of occurrence of BBB [Group A, 50% vs. Group B, 70% (p = NS)]. The causes of death in both groups were cardiogenic shock and/or electromechanical dissociation.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Left anterior hemiblock masking the diagnosis of right bundle branch block

A case is presented in which left anterior hemiblock obscured totally the diagnosis of right bundle branch block by abolishing the S wave in leads 1 and aVL, and terminal R wave in leads V1 and V2. The presence of right bundle branch block was confirmed by recording high V1 and V2 leads. Subsequently, the ECG revealed how a greater degree of conduction delay in the right bundle branch may uncover the previously concealed right bundle branch block. The electrocardiographic features of these findings are discussed.

Advanced early and late atrioventricular block in acute inferior wall myocardial infarction

Seventy-six patients with acute inferior acute myocardial infarction (AMI) and advanced atrioventricular (AV) block are described. According to pre-established ECG criteria and time of appearance of the advanced AV block, patients were divided into two groups. The early block group consisted of 31 patients who developed advanced AV block during the hyperacute ECG stage of AMI. Advanced AV block in these patients was characterized by early appearance, short duration, third-degree type block, poor response to atropine, and increased need for pacemaker therapy. The late block group consisted of 45 patients who developed advanced AV block during subsequent ECG stages of AMI. Advanced AV block in these patients was characterized by late appearance, longer duration, second-degree type block, positive response to atropine, and diminished need for pacemaker therapy. Morbidity and mortality also differed between both groups. Patients with early block had more syncope (32% vs 2%, p less than 0.0001), more left heart failure (36 vs 7%, p less than 0.005), and more cardiogenic shock (39% vs 2%, p less than 0.001) than patients with late block. The mortality rate in the early block group was high (23%) and similar to that reported in the literature, whereas the mortality rate in the late block group was low (7%, p less than 0.05) and similar to the mortality rate reported for acute inferior AMI without advanced AV block. These data identify a subgroup of patients with acute inferior AMI and advanced AV block, which accounts for the high mortality rate reported in this group of patients.

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

The electrocardiographic criteria for isolated left anterior fascicular block are reviewed and illustrated. Left anterior fascicular block decreases the voltage in the chest leads and increases the voltage in the limb leads. The usual voltage criteria of left ventricular hypertrophy must be modified appropriately. Changes in repolarization include a decrease in the T wave of leads I and AVL and an increase in leads II, III, AVF, V5 and V6. Small Q waves in V2 may simulate an anteroseptal myocardial infarction. Three criteria for the possible diagnosis of superimposed inferior myocardial infarction have been suggested. Both inferior and anterior myocardial infarctions may be masked by R waves replacing Q waves. In the presence of a recent anterior infarction, right bundle branch block may also be masked. Thus, left anterior fascicular block may mask or mimic infarction and left ventricular hypertrophy and mask right bundle branch block in the setting of an acute anterior myocardial infarction.

An accurate and simplified method to calculate angiographic left ventricular ejection fraction

An accurate and simplified method to calculate left ventricular (LV) ejection fraction (EF0 derived from the ellipsoidal formula for LV volume calculation is described. The LV Minor axis (D) is obtained from the average of three equidistant LV diameters at end-diastole (Ded) and end-systole (Des), and the shortening fraction of D2 (% delta D2) calculated as (D2ed - D2es)/D2ed. EF is calculated as EF = [delta D2 + ([1 - delta D2] X delta L)] X 100, where delta L = the shortening fraction of the long axis. The coefficient of correlation between the EF by this method and the EF derived from measurements of LV volumes with the area-length method was 0.98, SEE = 3.57% (n = 50). No significant over- or underestimation was observed according to the regression equation Y = 0.922X + 0.82. Thus, this simplified method allows accurate LVEF calculation without the need for planimetry of LV area.

An unusual ECG pattern: left posterior fascicular block obscuring a right ventricular conduction defect?

A 23-year-old man with a history of palpitations and a single syncopal attack is described. Results of the physical examination were negative. The ECG showed a marked right axis deviation, a QRS duration of 0.13 sec. and an rS pattern from V1 to V6. In the high right precordial leads an rsR' pattern was recorded. The VCG (Frank system) showed a rightward dislocation of QRS vectors, a clockwise inscription of the QRS loop in the frontal and transverse planes and a slowing of the rightward and posterior terminal vectors. The X-ray film and the echocardiogram were negative. Neither intra-cardiac shunts nor pressure abnormalities were detected at the heart catheterization. The basal His bundle electrogram showed an H-V prolongation. Atrial pacing caused a progressive increase of the QRS duration and the appearance of an R configuration in the V1 lead, without axis shifting. We propose that the electrocardiographic pattern was suggestive of a left posterior fascicular block masking in the standard right precordial leads an associated right ventricular conduction defect.