ECG in TOF is frequently asked question in exams because of it’s reliability predicting diagnosis. In TOF although there is RVOT obstruction RV pressure never goes above systemic pressure as there overriding aorta and VSD these equalize pressure across three structure (TOF physiology)
Right atrium is not enlarged in TOF (RV pressure is never suprasystmeic), this leads to just peaking of P waves without increase in voltage.
As there is decreased pulmonary blood flow (RVOT obstruction) so blood reaching the left atrium is decreased. P wave duration is reduced (duration of P wave is measure of left atrium enlargement)
In normals, intrauterine high pulmonary artery pressure falls after birth, hence RV regress after birth, but in TOF, RV never regresses, as it is exposed to systemic pressure, hence right axis deviation of new born persist in TOF. Of course there is exception for this, in patient with TOF associated with common AV canal defect (about 2% association with TOF) has left axis deviation.
RVH of TOF is depicted by presence of monophasic R wave in lead V1, but in lead V2, there is sudden transition to rS pattern.
In adult TOF patient about 0.7% have LVH instead of RVH
Measure of pulmonary blood flow in TOF is done by depth of q/Q waves and height of r/R waves in lateral precardial leads (volume overload of LV ) more the blood reaching the LV bigger the Q and R waves in V5 and V6.
In patient with pulmonary atreisa, if systemic arterial collaterals are more, then also LV can be over filled and lead V5 and V6 show QR. P wave duration is also increase as Left atrium is also overfilled
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| ECG in TOF showing R wave in lead V1 with RS in V2 (sudden transition), Right axis deviation , no q waves in lateral leads suggesting decreased pulmonary blood flow |
In patient with underfilled LV instead rS waves are observed in V2-V6.
VSD in TOF is nonrestrictive (no gradient across VSD defect) in patient with pulmonary stenosis with restrictive VSD or intact ventricle septum, right precardial leads show deeply inverted T waves in right precardial leads, unlike in TOF right precardial leads may show uright or just inverted T waves, with equal frequency.
ECG in TOF is frequently asked question in exams because of it’s reliability predicting diagnosis. In TOF although there is RVOT obstruction RV pressure never goes above systemic pressure as there overriding aorta and VSD these equalize pressure across three structure (TOF physiology)
Right atrium is not enlarged in TOF (RV pressure is never suprasystmeic), this leads to just peaking of P waves without increase in voltage.
As there is decreased pulmonary blood flow (RVOT obstruction) so blood reaching the left atrium is decreased. P wave duration is reduced (duration of P wave is measure of left atrium enlargement)
In normals, intrauterine high pulmonary artery pressure falls after birth, hence RV regress after birth, but in TOF, RV never regresses, as it is exposed to systemic pressure, hence right axis deviation of new born persist in TOF. Of course there is exception for this, in patient with TOF associated with common AV canal defect (about 2% association with TOF) has left axis deviation.
RVH of TOF is depicted by presence of monophasic R wave in lead V1, but in lead V2, there is sudden transition to rS pattern.
In adult TOF patient about 0.7% have LVH instead of RVH
Measure of pulmonary blood flow in TOF is done by depth of q/Q waves and height of r/R waves in lateral precardial leads (volume overload of LV ) more the blood reaching the LV bigger the Q and R waves in V5 and V6.
In patient with pulmonary atreisa, if systemic arterial collaterals are more, then also LV can be over filled and lead V5 and V6 show QR. P wave duration is also increase as Left atrium is also overfilled
In patient with underfilled LV instead rS waves are observed in V2-V6.
VSD in TOF is nonrestrictive (no gradient across VSD defect) in patient with pulmonary stenosis with restrictive VSD or intact ventricle septum, right precardial leads show deeply inverted T waves in right precardial leads, unlike in TOF right precardial leads may show uright or just inverted T waves, with equal frequency.
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