What is the initial workup for a patient with moderate intraventricular conduction delay?

From the Guidelines

The initial workup for a patient with moderate intraventricular conduction delay should include a comprehensive cardiac evaluation starting with a detailed history and physical examination, focusing on symptoms like syncope, palpitations, chest pain, or dyspnea. A 12-lead ECG is essential to characterize the conduction delay, measuring QRS duration and morphology, as defined in the 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay 1. Laboratory tests should include electrolytes (particularly potassium, calcium, and magnesium), renal function, and cardiac biomarkers if acute cardiac injury is suspected. An echocardiogram is recommended to assess cardiac structure and function, looking for underlying structural heart disease, as it can uncover treatable disease or impact management decisions such as cardiac resynchronization device placement 1. Ambulatory ECG monitoring (24-48 hour Holter or longer event monitoring) may be necessary to correlate symptoms with arrhythmias, aiming to uncover a symptom-rhythm correlation for patients with fatigue, dizziness, or syncope suspected of having atrioventricular block or SND in addition to their manifest conduction system disease 1. Exercise stress testing can evaluate for ischemia and assess the behavior of the conduction delay during exertion. Advanced imaging such as cardiac MRI might be indicated if structural abnormalities are suspected, particularly if sarcoidosis, connective tissue disease, myocarditis, or other dilated cardiomyopathies are suspected on clinical grounds 1. Electrophysiology studies are considered for patients with concerning symptoms or those at risk for progression to complete heart block, as they can provide acute diagnostic information and predict a higher risk for complete heart block in patients with fascicular or bundle branch block 1. This comprehensive approach helps identify the underlying cause of the conduction delay, assess its hemodynamic significance, determine the risk of progression, and guide appropriate management strategies. Some key points to consider in the workup include:

• The presence of LBBB on ECG markedly increases the likelihood that left ventricular systolic dysfunction will be diagnosed by echocardiogram 1
• Patients with RBBB or intraventricular conduction delay on ECG also have increased risk of left ventricular systolic dysfunction compared with those with completely normal ECGs 1
• Cardiac MRI can detect subclinical cardiomyopathy in patients with asymptomatic LBBB and a normal echocardiogram 1
• Electrophysiology studies can predict a higher risk for complete heart block in patients with fascicular or bundle branch block 1

From the Research

Initial Workup for Moderate Intraventricular Conduction Delay

The initial workup for a patient with moderate intraventricular conduction delay (IVCD) involves several key steps:

• Electrocardiogram (ECG) analysis to confirm the presence and severity of IVCD, as well as to identify any associated conduction abnormalities such as left or right bundle branch block 2
• Clinical evaluation to assess for symptoms and signs of heart failure, as IVCD can be a marker of underlying cardiac disease 3, 4
• Measurement of QRS duration to determine the severity of IVCD, with prolonged QRS duration (>110 ms) being associated with increased mortality and adverse outcomes 4

Diagnostic Considerations

When evaluating a patient with IVCD, it is essential to consider the following:

• The presence of IVCD can be a predictor of mortality in the general population, with increased risk of all-cause mortality, cardiac mortality, and arrhythmic death 4
• The pathophysiology of IVCD is complex and varied, and can be associated with cardiomyopathy, ischemic heart disease, and other conditions 3
• Cardiac resynchronization therapy (CRT) may be beneficial in patients with IVCD, particularly those with prolonged QRS duration and left bundle branch block or intraventricular conduction delay 5, 6

Further Evaluation and Management

Further evaluation and management of IVCD may involve:

• Echocardiography to assess left ventricular function and identify any signs of dyssynchrony or cardiac remodeling 5
• Consideration of CRT or other device therapies, such as implantable cardioverter-defibrillators, in patients with severe IVCD and associated heart failure or high-risk features 6
• Optimization of medical therapy, including beta-blockers, ACE inhibitors, and other heart failure medications, to improve symptoms and reduce mortality risk 3, 6