Treatment of Moderate Intraventricular Conduction Delay

Diagnostic Evaluation

The American College of Cardiology recommends a 12-lead ECG as the primary method for diagnosing intraventricular conduction disorders, documenting rhythm, rate, and conduction abnormalities 2
The American College of Cardiology suggests transthoracic echocardiography for patients with newly detected conduction abnormalities to identify underlying structural heart disease or left ventricular dysfunction 3, 4
The American Heart Association recommends ambulatory electrocardiographic monitoring to establish correlation between symptoms and rhythm disturbances, with the specific type of monitor chosen based on symptom frequency 5, 6
The American College of Cardiology considers exercise electrocardiographic testing reasonable for patients with exercise-related symptoms suspicious for bradycardia or conduction disorders 5
Electrophysiology studies may be considered in selected patients when noninvasive evaluation is nondiagnostic, according to the American College of Cardiology 2

Asymptomatic patients with isolated intraventricular conduction delay without evidence of structural heart disease generally do not require specific treatment, as stated by the American College of Cardiology 3
Regular follow-up is recommended as nonspecific intraventricular conduction delay may be a marker for development of coronary disease and heart failure, according to the American College of Cardiology 3
The American College of Cardiology recommends a lower threshold for further cardiac imaging or functional testing in patients with left bundle branch block (LBBB) compared to other forms of conduction delay 3

The American College of Cardiology indicates permanent pacing for patients with symptomatic bradycardia due to conduction disorders 7
Patients with syncope and bundle branch block who have an HV interval ≥70 ms or evidence of infranodal block at electrophysiology study should receive permanent pacing, as recommended by the American College of Cardiology 7
The American College of Cardiology recommends permanent pacing for patients with alternating bundle branch block due to high risk of developing complete heart block 7

The American College of Cardiology recommends cardiac resynchronization therapy (CRT) for patients with LBBB, QRS duration ≥150 ms, left ventricular ejection fraction (LVEF) ≤35%, and NYHA class II-IV symptoms despite optimal medical therapy 1
CRT should be considered for patients with non-LBBB morphology, QRS duration ≥150 ms, and LVEF ≤35%, according to the American College of Cardiology 1

Temporary pacing is indicated in patients with acute MI and symptomatic or hemodynamically significant bradycardia due to conduction delay, as stated by the American Heart Association 8
Permanent pacing is indicated after an appropriate waiting period for persistent second-degree Mobitz type II, high-grade AV block, alternating bundle-branch block, or third-degree AV block following MI, according to the American Heart Association 8
The American Heart Association recommends against permanent pacing in patients with acute MI and transient atrioventricular block that resolves 8
Permanent pacing should not be performed in patients with acute MI and a new bundle-branch block or isolated fascicular block in the absence of higher-degree AV block, as stated by the American Heart Association 8

The development of intraventricular conduction delay following myocardial infarction reflects extensive myocardial damage rather than an isolated electrical problem, according to the American College of Cardiology and the American Heart Association 1, 8
Patients with anterior myocardial infarction and associated conduction impairment generally have worse prognosis than those with inferior myocardial infarction, as stated by the American College of Cardiology 1

Implanting permanent pacemakers too early (<72 hours) after myocardial infarction, as conduction abnormalities may resolve with reperfusion and recovery, according to the American College of Cardiology 1
Failing to recognize that intraventricular conduction delay may be the first manifestation of underlying structural heart disease or cardiomyopathy, as stated by the American College of Cardiology 7
Overlooking the importance of QRS morphology (LBBB vs. non-LBBB) and duration (≥150 ms vs. 120-149 ms) in determining the likelihood of response to CRT, according to the American College of Cardiology 1