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Bundle-branch block typically features
discordant ST-T-wave changes, meaning that the ST segment and T wave are directed opposite the major polarity of the QRS complex. In leads with positive QRS complexes, ST-segment depression and T-wave inversion are expected, and in leads with a primarily negative QRS complex, ST-segment elevation and an upright T wave are anticipated.
Fascicular blocks
do not significantly prolong the qrs complex duration but rare important because they can cause changes that mimic previous infarction and in certain circumstances identify patients at greater risk to develop DC
the left bundle branch splits into two fascicles, two
fascicular blocks are possible: the more common Left anterior ; and the relatively rare left posterior
TABLE 2.1. Causes of intraventricular conduction abnormalities
Atherosclerotic heart disease Congenital heart disease Connective tissue disease (eg, scleroderma; electrolyte abnormalities, fibrotic heart disease, latrogenic, infectious disease, inflitrative cardiomyopathy; PE; normal variant toxicologic
describe normal QRS complex: Consider the two precordial electrodes, V1 and V6 as being essentially
opposite each otehr in the horizontal plane in a vector representatino of ventricular depolarization
Also remember that a waveform; eg a Q an R or an S wave is positive if the depolarization vector is coming toward the electrode.
lead V1; demonstrates a small R wave followed by a large S wave
lead v6 ; a small initial Q wave; septal Q wave; followed by a large R wave
causes of R wave amplitude greater than S wave amplitude in lead V1
hypertrophic cardiomyopathy
normal variant especially children and adolescents
duchenne type pseudohypertrophic muscular dystrophy
PH
RBBB
RVH
true posterior MI
WPWS
a general rule: recognition of dominant R wave in lead V1 should prompt consideration of RBBB
criteria RBBB?
- in V6; small initial Q wave from the septum; then signifcant R wave, then wide S wave from delayed depolarization of the RV
criteria LBBB?
slurred monophasic R wave in V5-6 can be absent, but present in leads I and aVL
linker hartas is not a prerequisite for diagnosis but can occur with it ; more often it is however normal
if it is really negative; -90, that suggest preexisting or coincident left anterior fascicular block
in leads with a predominantly positive QRS complex, the ST segments and T waves are isoelectric or depressed; and vise versa, the transition leads in which the overall QRS complex is neutral do not necessarily follow this pattern;;;; deviation from this can suggest MI
dd large amplitude negative QS or rS complexes in leads V1 and V2 (right precordial leads)
criteria left anterior fascicular block
linker hartas is belangrijk; more liberal definition starts with -30, but in general -45
once left axis is noted, the next step focuses on analysis of the limb leads not the precordial leads
IMPORTANT; a key finding is poor precordial R wave progression or displacement of the transition zone
LVH should not be diagnosed by aVL R wave amplitude higher than 11 mm in the presence of this condition because R wave in lead aVL is bigger than normal
this abnormality is the most common intraventricular conduction abnormality seen in acute MI
left posterior fascicular block
type of bradycardias
escape pacemaker rhythms
heart blocks
AV blocks
third av block rest
causes of clinically significant av block
mobitz 1 vs 2
third degree AV block
narrow complex tachycardias
mechanisms of tachyarrhythimas
focal atrial tachyacardia caused by enhanced automaticity
multifocal atrial tachycardia
characteristics AF
