What are the management strategies for interventricular conduction delay?

Management Strategies for Interventricular Conduction Delay

For patients with interventricular conduction delay, management should be guided by the presence of symptoms, underlying heart disease, and specific ECG findings, with permanent pacing recommended for symptomatic patients with evidence of significant conduction system disease. 1

Diagnostic Evaluation

• Transthoracic echocardiography is recommended for patients with newly detected LBBB to exclude structural heart disease (Class I recommendation) 1
• Ambulatory electrocardiographic monitoring is useful in symptomatic patients with conduction system disease to detect potential intermittent atrioventricular block 1
• Advanced imaging (cardiac MRI, CT, or nuclear studies) is reasonable when echocardiography is unrevealing but structural heart disease is still suspected in patients with LBBB 1, 2
• Electrophysiology study (EPS) is reasonable in patients with symptoms suggestive of intermittent bradycardia with conduction system disease identified by ECG 1
• Stress testing with imaging may be considered if ischemic heart disease is suspected in asymptomatic patients with LBBB 1, 2

Management Based on Clinical Presentation

Symptomatic Patients

• Permanent pacing is recommended for patients with syncope and bundle branch block who have an HV interval ≥70 ms or evidence of infranodal block at EPS (Class I) 1
• Permanent pacing is recommended for patients with alternating bundle branch block due to high risk of developing complete heart block (Class I) 1
• In patients with Kearns-Sayre syndrome and conduction disorders, permanent pacing is reasonable, with additional defibrillator capability if appropriate (Class IIa) 1
• In patients with Anderson-Fabry disease and QRS prolongation >110 ms, permanent pacing with additional defibrillator capability may be considered (Class IIb) 1

Patients with Heart Failure

• Cardiac resynchronization therapy (CRT) may be considered in patients with heart failure, mildly to moderately reduced LVEF (36%-50%), and LBBB with QRS ≥150 ms (Class IIb) 1, 3
• CRT is recommended for patients with LVEF ≤35%, sinus rhythm, LBBB with QRS duration ≥150 ms, and NYHA class II-IV symptoms on guideline-directed medical therapy 3, 4
• CRT can be useful for patients with LVEF ≤35%, sinus rhythm, non-LBBB pattern with QRS duration ≥150 ms, and NYHA class III/ambulatory class IV symptoms on guideline-directed medical therapy 3, 4
• Among non-LBBB patients, those with nonspecific intraventricular conduction delay (NICD) and QRS ≥150 ms may have better outcomes with CRT-D compared to ICD alone 5

Asymptomatic Patients

• Permanent pacing is NOT indicated in asymptomatic patients with isolated conduction disease and 1:1 atrioventricular conduction (Class III: Harm) 1
• In selected asymptomatic patients with extensive conduction system disease (bifascicular or trifascicular block), ambulatory electrocardiographic recording may be considered to document suspected higher degree of atrioventricular block 1

Special Considerations

• Prolonged interventricular and intraventricular conduction causes regional mechanical delay within the left ventricle that results in reduced ventricular systolic function, altered myocardial metabolism, functional mitral regurgitation, and adverse remodeling 3, 6
• QRS morphology is important: The benefit of CRT is greatest in patients with LBBB pattern compared to non-LBBB patterns 3, 5
• QRS duration is critical: Patients with QRS duration ≥150 ms show greater benefit than those with QRS duration 120-149 ms 3, 7
• Baseline interventricular electrical delay (measured as RV-LV interval) is a potent predictor of response to CRT, with longer delays associated with better outcomes 7
• For patients requiring CRT, the choice between CRT-Pacemaker and CRT-Defibrillator should be based on overall risk assessment 3

Common Pitfalls to Avoid

• Implanting permanent pacemakers too early (<72 hours) after myocardial infarction, as conduction abnormalities may resolve with reperfusion and recovery 3, 4
• Failing to recognize that interventricular conduction delay may be the first manifestation of underlying structural heart disease or cardiomyopathy 1, 4
• Overlooking the importance of QRS morphology and duration in determining the likelihood of response to CRT 3, 5
• Approximately one-third of patients with advanced heart failure have QRS prolongation, and this is associated with worse outcomes if left untreated 3, 8