Right bundle branch

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

Figure 13.3 Route of excitation and conduction in the heart. The heart beat is initiated in the sinoatrial (SA) node, or the pacemaker, in the right atrium of the heart. The electrical impulse is transmitted to the left atrium through the interatrial conduction pathway and to the atrioventricular (AV) node through the intemodal pathway. From the AV node, the electrical impulse enters the ventricles and is conducted through the AV bundle, the left and right bundle branches, and, finally, the Purkinje fibers, which terminate on the true cardiac muscle cells of the ventricles.

From the AV node, the electrical impulse spreads through the AV bundle or the bundle of His. This portion of the conduction system penetrates the fibrous tissue separating the atria from the ventricles and enters the interventricular septum where it divides into the left and right bundle branches. The bundle branches travel down the septum toward the apex of the heart and then reverse direction, traveling back toward the atria along the outer ventricle walls. This route of conduction of the impulse facilitates ejection of blood from the ventricles. If the impulse were to be conducted directly from the atria to the ventricles, the ventricular contraction would begin at the top of the chambers and proceed downward toward the apex. This would trap the blood at the bottom of the chambers. Instead, the wave of ventricular electrical stimulation and, therefore, contraction moves from the apex of the heart toward the top of the chambers where the semilunar valves are located and ejection takes place. 

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. 

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. 

Septal ablation related mortality at experienced centers is currently 1% to 2%, similar to that of surgical myectomy (Table 4). Conduction system abnormalities are relatively common complications of septal ablation, Permanent right bundle branch block occurs in about 50% of patients and transitory complete heart block in 60% and permanent pacemakers required for high grade atrioventricular block in about 5% to 20%, Concerns of late occurrence of complete heart block following septal ablation mandates in-patient monitoring for 4 to 5 days,... 

A 44-year-old woman took an overdose of venlafaxine 3 g. An electrocardiogram showed sinus rhythm and incomplete right bundle branch block (32). She was monitored in an intensive care unit and 10 hours later a further electrocardiogram showed atrial fibrillation with a wide QRS complex. Both of these abnormalities resolved with sodium bicarbonate (100 ml of a 1 M solution). No further conduction disturbances were noted over the following days. 

A 34-year-old man developed palpitation, shortness of breath, and chest pain. He had smoked a quarter to a half an ounce of marijuana per week and had taken it 3 hours before the incident. He had ventricular tachycardia at a rate of 200/minute with a right bundle branch block pattern. Electrical cardioversion restored sinus rhythm. Angiography showed a significant reduction in left anterior descending coronary artery flow rate, which was normalized by intra-arterial verapamil 200 micrograms. 

Left bundle branch block (LBBB) is characteristic of poisoning and is defined by Zimetbaum et al. (2004) as QRS > 0.12 s with delayed intrinsicoid deflection in the Vi, V5, and Vs leads greater than 0.05 s. The risk of arrhythmia is greatest when QRS is >0.11 s. Right bundle branch block (RBBB) greater than 0.12 s is a fairly good predictor of arrhythmic death. 

In a prospective study of 187 episodes of tachycardia in 127 unselected patients adenosine was given in an average dose of 9.7 mg (28). In 108 cases, adenosine induced transient ventricular extra beats or non-sustained ventricular tachycardia after successful termination of supraventricular tachycardia more than half had a right bundle branch block morphology that suggested that the dysrhythmias had originated from the inferior left ventricular septum. 

Class Ic antidysrhjdhmic drugs have been reported to cause the characteristic electrocardiographic changes of Brugada syndrome, which consists of right bundle branch block, persistent ST segment elevation, and sudden... 

Gould L, Patel C, Betzu R, Judge D, Lee J. Right bundle branch block a rare manifestation of digitalis toxicity— case report. Angiology 1986 37(7) 543-6. 

Right bundle branch block has also been reported (6). 

In a 37-year-old woman with atrial flutter with 1 1 conduction and partial right bundle branch block, intravenous dofetihde 5 micrograms/kg given over 5 minutes not only suppressed the atrioventricular nodal block to 2 1 or 3 1 but also caused complete right bundle branch block and QT interval prolongation (58). 

Brugada R, Brugada J, Antzelevitch C, Kirsch GE, Potenza D, Towbin JA, Brugada P. Sodium channel blockers identify risk for sudden death in patients with ST-segment elevation and right bundle branch block but structurally normal hearts. Circulation 2000 101(5) 510-15. 

In one study of 17 patients with mild Parkinson s disease who were given either mesulergine or pergolide, mesulergine impaired the quality of life frequent adverse effects were vomiting, lassitude, abdominal discomfort, depression, right bundle-branch block, fuzzy-headedness, and increasing insuhn requirements in a patient with diabetes (SEDA-13,113). 

Complete atrioventricular block occurred in a 10-year-old child with a history of hypertension, severe renal dysfunction, incomplete right bundle branch block, and a ventricular septal defect that had been repaired at birth (10). After slow induction with sevoflurane and nitrous oxide 66%, complete atrioventricular block occurred when the inspired sevoflurane concentration was 3% and reverted to sinus rhythm after withdrawal of the sevoflurane. The dysrhjrthmia recurred at the end of the procedure, possibly caused by lidocaine, which had infiltrated into the abdominal wound, and again at 24 hours in association with congestive cardiac failure following absorption of peritoneal dialysis fluid. 

It is unclear whether topiramate played any role in rare cardiovascular events. These included symptoms of Raynaud s phenomenon in three patients, and third-degree atrioventricular block requiring emergency cardiac pacemaker implantation in one patient with preexisting right bundle branch block (SEDA-21, 76). 

Brugada J, Brugada R, Brugada P. 1998. Right bundle-branch block and ST-segment elevation in leads VI through V3 a marker for sudden death in patients without demonstrable structural heart disease. Circulation 97 457-60... 

Additionally, when a typical right bundle branch block morphology is seen in the course of an STE-ACS, this greatly supports a high septal ischaemia (occlusion above the SI branch), causing this bundle branch, since first septal (SI)... 

Figure 4.53 Arrhythmogenic right ventricular dysplasia (ARVD). Note the image of atypical right bundle branch block, negative T wave in the V1-V4 leads, and premature ventricular complexes of the right ventricle. QRS duration...

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