Bundle branch block

Refers to a block in the electrical impulse down one of the bundle branches, knovm either as a left or right Bundle Branch Block (LBBB/RBBB). The principle characteristic of a Bundle Branch Block is a widened QRS complex. This occurs because the impulse cannot travel down the fast conduction pathway due to the blockage (Fig. 7.1). The impulse takes an alternative route through the myocardium resulting in delayed ventricular depolarisation and the characteristic widened QRS complex (Fig. 7.2). A normal QRS complex has a width of 0.06-0.10 s (1.5-2.5 small 

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The easiest method of determining the difference between a LBBB and a RBBB is to look in lead V,. 

If the QRS complex is negatively deflected in lead V, wider than 2.5 small sqnares and cannot be explained by any of the other causes of a widened. 

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ST-segment elevation of at least 1 mm in height in two or more contiguous leads, or new or presumed new left bundle-branch block... 

ECC first-degree heart block, right bundle-branch block, and arrhythmias... 

AFB Acid-fast bacillus aortofemoral bypass aspirated BBB Bundle-branch block, blood-brain barrier... 

The sequence of cardiovascular signs as serum magnesium increases from 3 mEq/L to 15 mEq/L is hypotension, cutaneous vasodilation, QT-interval prolongation, bradycardia, primary heart block, nodal rhythms, bundle branch block, QRS- and then PR-interval prolongation, complete heart block, and asystole. 

Despite concerns regarding safety and side effects, TCAs are appropriate for some patients. When starting a TCA, a baseline EKG is required. If the EKG reveals a second-degree or higher heart block, a bundle branch block, or a corrected QT interval exceeding 440 milliseconds, then a TCA should not be started. The initial doses should be low, especially in older patients or those with anxiety who are particularly sensitive to side effects. Over the first 7-14 days, the dose should be increased gradually to the lower end of the expected therapeutic range. After an additional 2-3 weeks, the dose may be increased further if necessary. 

Cardiovascular - Ang na pectoris aggravated, arrhythmia, arrhythmia atrial, atrial fibrillation, bradycardia, bundle branch block, cardiac failure, extrasystole, heart murmur, heart sound abnormal, hypertension, hypotension. Ml, palpitation, Q-wave abnormality, tachycardia, ventricular tachycardia (5% or less). 

Hypersensitivity or idiosyncrasy to quinidine or other cinchona derivatives manifested by thrombocytopenia, skin eruption or febrile reactions myasthenia gravis history of thrombocytopenic purpura associated with quinidine administration digitalis intoxication manifested by arrhythmias or AV conduction disorders complete heart block left bundle branch block or other severe intraventricular conduction defects exhibiting marked QRS widening or bizarre complexes complete AV block with an AV nodal or idioventricular pacemaker aberrant ectopic impulses and abnormal rhythms due to escape mechanisms history of drug-induced torsade de pointes history of long QT syndrome. 

Use quinidine with extreme caution in incomplete AV block, because complete block and asystole may result. The drug may cause unpredictable dysrhythmias in digitalized patients. Use cautiously in patients with partial bundle branch block, severe CHF, and hypotensive states due to the depressant effects of quinidine on myocardial contractility and arterial pressure. 

Conduction abnormalities Use caution in patients with sick sinus syndrome, Wolff-Parkinson-White syndrome or bundle branch block. 

Preexisting second- or third-degree AV block, right bundle branch block when associated with a left hemiblock (bifascicular block), unless a pacemaker is present to sustain the cardiac rhythm if complete heart block occurs recent myocardial infarction (Ml) presence of cardiogenic shock hypersensitivity to the drug. 

If second-or third-degree AV block, or right bundle branch block associated with a left hemiblock occurs, discontinue therapy unless a ventricular pacemaker is in place to ensure an adequate ventricular rate. 

Cardiovascular - Benign intracranial hypertension (pseudotumor cerebri) has been reported rarely. Bulging fontanels, as a sign of benign intracranial hypertension in infants, have been reported rarely. Changes in electrocardiogram (eg, nonspecific ST/T wave changes, bundle branch block) have been reported in association with pulmonary reactions. 

Baldasseroni S, Opasich C, Gorini M, et al. Left bundle-branch block is associated with increased 1-year sudden and total mortality rate in 5517 outpatients with congestive heart failure a report from the Italian network on congestive heart failure. Am. Heart J. 2002 143 398-405. 

Godman MJ, Lassers BW, Julian DG. Complete bundle-branch block complicating acute myocardial infarction. N. Engl. J. Med. 1970 282 237. ... 

Hindman MC, Wagner GS, JaRo M, et al. The clinical significance of bundle branch block complicating acute myocardial infarction. 1. Clinical characteristics, hospital mortality, and one-year follow-up. Circulation 1978 58 679-88. 

Stenestrand U, Tabriz F, Lindback J, England A, Rosenqvist M, Wallentin L. Comorbidity and myocardial dysfunction are the main explanations for the higher 1-year mortality in acute myocardial infarction with left bundle-branch block. Circulation 2004 110 1896-902. 

Xiao HB, Lee CH, Gibson DG. Effect of left bundle branch block on diastolic function in dilated cardiomyopathy. Br. Heart J. 1991 66 443-7. 

Sade LE, Kanzaki H, Severyn D, Dohi K, Gorcsan J, III. Quantification of radial mechanical dyssynchrony in patients with left bundle branch block and idiopathic dilated cardiomyopathy without conduction delay by tissue displacement imaging. Am. J. Cardiol. 2004 94 514-8. 

Nelson GS, Berger RD, Fetics BJ, et al. Left ventricular or biventricular pacing improves cardiac function at diminished energy cost in patients with dilated cardiomyopathy and left bundle-branch block, [erratum appears in Circulation 2001 Jan 23 103 (3) 476]. Circulation 2000 102 3053-9. 

In contrast, intravenous fibrinolytic therapy is harmful without acute ST-segment elevation, a true posterior MI or a presumed new left bundle-branch block. 

This arrhythmia usually occurs in young people and preponderantly in men. The electrocardiogram often shows right bundle branch block with left axis deviation (superior axis deviation). This type of VT is often sensitive to verapamil or other calcium channel blockers, but not to /3-blockers. Radiofrequency catheter ablation may be helpful to abolish it. 

Contraindications to procainamide are similar to those for quinidine. Because of its effects on A-V nodal and His-Purkinje conduction, procainamide should be administered with caution to patients with second-degree A-V block and bundle branch block. Procainamide should not be administered to patients who have shown procaine or procainamide hypersensitivity and should be used with caution in patients with bronchial asthma. Prolonged administration should be accompanied by hematological studies, since agranulocytosis may occur. 

Flecainide is contraindicated in patients with preexisting second- or third-degree heart block or with bundle branch block unless a pacemaker is present to maintain ventricular rhythm. It should not be used in patients with cardiogenic shock. 

Bundle-branch block, AV block, bradycardia, hypertension Serious Reactions... 

Overdose with TCAs causes tachycardia, hypotension, prolonged EKG intervals, and fatal arrhythmias, including ventricular tachycardias and bundle branch blocks (lack of conduction of the cardiac impulse). Conduction deficits alone and in combination with hypotension account for most of the morbidity and mortality associated with TCA overdose (Baldessarini, 1996). 

In the case of patients with preexisting heart disease and patients older than 40 years, an electrocardiogram should be obtained before the initiation of TCA treatment. TCAs should not be used in patients with bundle branch block unless all other options have failed. 

Slow conduction, which places patients with bundle branch block at risk for development of conduction complications... 

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