Lbbb vs ivcd1/7/2024 If the QRS duration is ≥0,110 seconds but 0.05 seconds. Leads V5, V6, I and aVL shows positive T-waves. ST-T changes: V1-V2 shows downsloping ST-segments and inverted T-waves.S-wave duration is greater than R-wave duration, or S-wave duration is greater than 40 ms in V6 and I. The second R-wave (denoted R’) is virtually always larger than the first R-wave. Occasionally the S-wave does not reach the baseline. More specifically, the QRS complex displays rsr’, rsR’ or rSR’ pattern (rSR’ is the most common, exemplified in Figure 1). Leads V1-V2: The QRS complex appears as the letter “M”.ECG criteria for right bundle branch block (RBBB) The distinction between RBBB and LBBB is simple, as illustrated in this figure. The hallmark of both RBBB and LBBB is the QRS duration which is by definitions 120 ms or longer. Note that the paper speed is 50 mm/s (1 large box equals 100 ms). Right bundle branch block (RBBB) and left bundle branch block (LBBB). Note that the ventricular conduction system is the His-Purkinje system. The right bundle branch and the fascicles then branch further into the fine Purkinje network which sprouts out to the entire myocardium. The left bundle branch is then divided into an anterior and posterior fascicle. The AV node continues in the bundle of His, which branches into the right and left bundle branch. The sinoatrial (SA) node and atrioventricular (AV) node are located in the atria (they are not part of the ventricular conduction system). The electrical conduction system of the heart, with emphasis on the ventricles. Figure 2 illustrates a normal ECG, a right bundle branch block (RBBB) and a left bundle branch block (LBBB). The hallmark of right bundle branch block is QRS duration ≥0,12 seconds, large R’-wave in V1/V2 and a broad and deep S-wave in V5/V6. The slow spread of the impulse will result in a slow (and abnormal) activation of the right ventricle, which yields a bizarre and prolonged QRS complex on ECG. However, the electrical impulse that spreads from the left ventricle (to the right ventricle) will spread slowly because it travels partly or entirely outside of the conduction system. In the setting of RBBB, depolarization (i.e activation) of the right ventricle will depend on electrical impulses spreading from the left ventricle. Refer to Figure 1 for an overview of the components of the ventricular conduction system, including the right bundle branch. Atypical left bundle branch morphology defined as QS or rS in lead V1, broad R waves in lead I, and aVL but with QS or rS in V5-V6 is associated with favorable echocardiographic response to CRT and displays similar survival rates to typical LBBB patients.Ītypical left bundle branch block Cardiac resynchronization therapy Heart failure Left bundle branch block.Right bundle branch block (RBBB) is due to an anatomical or functional dysfunction in the right bundle branch, such that the electrical impulse is blocked. This subgroup of IVCD should be considered for CRT. Patients with ALBBB may have a favorable echocardiographic response to CRT and display similar survival rates to typical LBBB. Cumulative 2-year survival was 88% in ALBBB, 86% in TLBBB, and 76% in OIVCD (p value = 0.011). A multivariable model showed a lower likelihood of echocardiographic response in OIVCD and a similar likelihood in ALBBBB compared to TLBBB. 75% and 72%, respectively, p = 0.01 for both comparisons). Rates of echocardiographic response were lower among those with OIVCD compared to those with LBBB and ALBBB (50% vs. Endpoints were 2 years mortality and echocardiographic response, defined as a decrease of ≥ 10% in indexed LVESV or an increase of ≥ 5% in left ventricular ejection fraction at 1 year of follow-up.īaseline clinical characteristics were similar among all the three groups. ECGs were classified into the following three groups: (a) typical LBBB (TLBBB) according to accepted guidelines (n = 67) (b) IVCD with LBBB pattern criteria in V1, 1, and aVL but with QS or rS in V5-V6 which we defined as atypical LBBB (ALBBB) (n = 74) and (c) all other IVCD (OIVCD) patterns (n = 98). However, IVCD pattern is heterogeneous, and it is possible that QRS patterns may also respond to CRT.Ĭonsecutive baseline ECGs of 239 patients implanted between 20 with CRT were analyzed. Response to cardiac resynchronization therapy (CRT) is well-established in patients with typical left bundle branch block (LBBB) but modest or even negative in those with intraventricular conduction delay (IVCD).
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