Intraventricular conduction delay electrocardiogram: Difference between revisions
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===Electocardiogram=== | ===Electocardiogram=== | ||
===Complete Left Bundle Branch Block=== | ===Complete Left Bundle Branch Block=== | ||
* [[QRS]] duration ≥120 msec in adults | *[[QRS]] duration ≥120 msec in adults | ||
*Abnormal interventricular septum activation by RBB : | *Abnormal interventricular septum activation by RBB : | ||
**Absent q waves in leads I, V5, and V6, but in the lead aVL, a narrow q wave may be present in the absence of myocardial disease. | **Absent q waves in leads I, V5, and V6, but in the lead aVL, a narrow q wave may be present in the absence of myocardial disease. | ||
| Line 24: | Line 24: | ||
*QRS axis : | *QRS axis : | ||
**In some cases, the mean QRS axis may change in the frontal plane to the right, to the left, or superiorly, in a rate-dependent manner. | **In some cases, the mean QRS axis may change in the frontal plane to the right, to the left, or superiorly, in a rate-dependent manner. | ||
===Incomplete Left Bundle Branch Block=== | |||
*QRS duration is of 110 to 119 milliseconds. | |||
*Abnormal interventricular septum activation by RBB : Absence of q wave in leads I, V5, and V6 and frequent replacement by a slurred initial upstroke (pseudo-delta wave). | |||
*Right ventricular activation : Small or absent initial r waves in right precordial leads V1 and V2 followed by deep S waves. | |||
*Delayed left ventricular activation : R wave peak time longer than 60 milliseconds in leads V4, V5, and V6. Slurring and notching of the upstroke of tall R waves. The pattern commonly is similar to that of [[LVH]]. | |||
==References== | ==References== | ||
Revision as of 19:34, 9 September 2013
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mugilan Poongkunran M.B.B.S [2]
Overview
Intraventricular conduction delay is a common clinical abnormality detected on the electrocardiogram (ECG). Right and left bundle branch blocks usually reflect intrinsic impairment of conduction in either the right or left bundle system (intraventricular conduction disturbances) which can be either chronic or intermittent. Transient rate-related bundle branch blocks occurs when the heart rate increases (tachycardia or acceleration-dependent) or when heart rate decreases (bradycardia or deceleration-dependent) which are relatively rare.
Electocardiogram
Complete Left Bundle Branch Block
- QRS duration ≥120 msec in adults
- Abnormal interventricular septum activation by RBB :
- Absent q waves in leads I, V5, and V6, but in the lead aVL, a narrow q wave may be present in the absence of myocardial disease.
- Right ventricular activation :
- An rS or QS pattern in lead V1.
- Small or absent initial r waves in right precordial leads V1 and V2 followed by deep S waves.
- Delayed left ventricular activation :
- Broad notched or slurred R wave in leads I, aVL, V5, and V6 and an occasional RS pattern in V5 and V6 attributed to displaced transition of QRS complex.
- R wave peak time >60 msec in leads V5 and V6 but normal in leads V1, V2, and V3, when small initial r waves can be discerned in the above leads.
- Repolarization changes :
- The ST segment and T wave are discordant with the QRS complex.
- ST and T waves usually opposite in direction to QRS.
- Positive T wave in leads with upright QRS may be normal (positive concordance). The ST segment is usually depressed and the T wave is inverted in leads with positive QRS waves (e.g., leads I, aVL, V5, and V6).
- Depressed ST segment and negative T wave in leads with negative QRS (negative concordance) are abnormal. The ST segment is usually elevated and the T wave is upright in leads with negative QRS complexes (e.g., leads V1 and V2).
- QRS axis :
- In some cases, the mean QRS axis may change in the frontal plane to the right, to the left, or superiorly, in a rate-dependent manner.
Incomplete Left Bundle Branch Block
- QRS duration is of 110 to 119 milliseconds.
- Abnormal interventricular septum activation by RBB : Absence of q wave in leads I, V5, and V6 and frequent replacement by a slurred initial upstroke (pseudo-delta wave).
- Right ventricular activation : Small or absent initial r waves in right precordial leads V1 and V2 followed by deep S waves.
- Delayed left ventricular activation : R wave peak time longer than 60 milliseconds in leads V4, V5, and V6. Slurring and notching of the upstroke of tall R waves. The pattern commonly is similar to that of LVH.