From the Guidelines
For an asymptomatic patient with new onset incomplete right bundle branch block (RBBB) and marked left axis deviation on electrocardiogram (EKG), I recommend a comprehensive cardiac workup, including a transthoracic echocardiogram, to assess for underlying structural heart disease, as suggested by the 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay 1. The patient's EKG findings may represent a bifascicular block, which could be a normal variant but may also indicate underlying cardiac disease.
- Key considerations in the management of this patient include:
- Assessing for symptoms that may indicate cardiac disease, such as syncope or presyncope
- Evaluating for risk factors for heart disease
- Considering advanced imaging tests, such as cardiac MRI or computed tomography, if clinical suspicion of structural heart disease is high
- Regular follow-up with annual EKGs to monitor for progression of conduction disease The yield of transthoracic echocardiography is higher when there are clinical indications of structural disease, as noted in the guideline 1.
- Additional testing, such as 24-hour Holter monitoring or an exercise stress test, may be considered on a case-by-case basis to detect intermittent arrhythmias or inducible ischemia. In the absence of symptoms or risk factors for heart disease, routine imaging is not recommended, as stated in the guideline 1.
- A cardiology consultation is essential to determine the best course of management for this patient, taking into account the patient's individual risk factors and clinical presentation.
From the Research
Management of Asymptomatic Patient with New Onset Incomplete RBBB and Marked Left Axis Deviation
- The management of an asymptomatic patient with new onset incomplete right bundle branch block (RBBB) and marked left axis deviation on electrocardiogram (EKG) is not directly addressed in the provided studies.
- However, the studies suggest that incomplete RBBB can be a benign condition, but it can also be associated with underlying cardiac abnormalities, such as Brugada syndrome 2, arrhythmogenic right ventricular cardiomyopathy, or ventricular preexcitation—Wolf-Parkinson-White syndrome 3.
- In some cases, new-onset RBBB can be a sign of critical coronary occlusion, particularly in the context of acute myocardial infarction 4.
- The presence of marked left axis deviation can be associated with various conditions, including left posterior fascicular block or intermittent right axis deviation 5.
- Given the potential for underlying cardiac abnormalities, it is essential to perform a thorough clinical evaluation, including a detailed medical history, physical examination, and additional diagnostic tests, such as echocardiogram, exercise test, or electrophysiologic study, to determine the cause of the incomplete RBBB and left axis deviation 2, 3.
- If the patient is found to have an underlying cardiac condition, such as Brugada syndrome, treatment may involve the use of medications, such as sotalol, or the implantation of an Automatic Implantable Cardioverter Defibrillator 2.