ECG to save Babies
ECG Interpretation Best to have a system to methodically evaluate ECG (from Dubin) * Rate * Rhythm * Axis * Intervals * Hypertrophy * Infarction
Electrical Activity in the heart 5 events 3 events seen on ECG Atrial depolarisation Atrial repolarisation AV conduction Ventricular Depolarisation Ventricular Repolarisation Atrial depolarisation ( P wave) Vent depolarisation (QRS wave) Ventricular repolarisation (T wave) AV conduction inferred (relationship of P to QRS)
ECG CONVENTION Paper Speed * 25mm/sec: 1 big box = 0.2 sec (or 200 msec), 1 little box = 0.04 sec (or 4 0 msec) * Voltage * Standard: 1mV = 1cm (10 mm) * Half standard: 1mV = 0.5cm (5mm) * Double Standard: 1mV = 2cm (20mm)
Age Consideration * Age exact age is very important in the interpretation of ECGs in infants * Normal values for 7 different age categories in the first year of life * < 1 day, 1-2 days, 3-6 days, 1-3 weeks, 1-2 months, 3-5 months, 6-11 months,
QRS Axis Check Leads if I + avf are +ve = axis normal (between 0 and 90 ) axis is perpendicular to equiphasic QRS Normal axis varies with age: * newborn 60-180 * 1 yr 0-100 * adult 30-90 Frontal Plane I, II, III, avr, avl, avf Chest (Precordial) Leads V1, V2,V3, V4, V5, V6
ECG : Rhythm * Normal Sinus Rhythm * P wave precedes every QRS AND Upright (+) P waves in I and avf I avf Site of Origin + (positive) - (Negative) - (negative) - (Negative) + (positive) - (negative) Low right atrium (normal variant) High Left Atrium (lead reversal, situs inversus, ectopic atrial tach) Low Left Atrium (lead reversal, situs inversus, ectopic atrial tach)
Axis Summaries Left Axis Deviation Right Axis Deviation Superior Axis = L anterior hemiblock (abnormal conduction system likely to be in wrong place) Endocardial cushion defects (complete AV canal and ostium primum septal defect) Tricuspid atresia PS (Noonan) esp if HCM single ventricle RVH RBBB AVSD WPW syndrome = Ebstein Anomaly, L-Transposition of the great Arteries (L- TGA) Complete heart block = L-TGA, polyspenia syndrome, maternal Lupus
INTERVALS PR * from start of P to start of Q = excitation traveling from SA node ventricular muscle * with exercise * 0.12 0.2 <0.16 in children <0.18 in adolescents/ adults Prolonged PR interval 1 st degree heart block * normal variant * myocarditis * digitalis toxicity * CHD (AVSD, ASD, Ebsteins) Shortened PR * pre-excitation (WPW, Lown-Ganong-Levine syndrome) * glycogen storage disease * low right atrial pacemaker (-ve in avf)
QRS From start of Q to end of S = time it takes for excitation to spread through ventricles * with age * 0.08 (children) 0.10 (adults) * Q waves abnormal in V1 think RVH, LBBB, cctga * ArepathologicalinV1(except occasional newborns) and indicate L- TGA, single ventricle, severe RVH or anterior MI (deep and wide). * neonate has dominant R in V1 by 3 years reaches adult pattern (S in V1, R in V6) Prolonged QRS = abnormal ventricular conduction * RBBB * LBBB * WPW * interventricular block * premature ventricular beats * VT * ventricular pacemaker
QTc * QTc * from start of Q to end of T * < 0.44 (<0.49 in infants <6/12)
Hypertrophy * atrial (P wave) * ventricular (LVH, RVH, CVH) * RAE * tall and tented P wave (P-pulmonale) (>/= 3mm) in II, V1 and V2 * ASD, TR, ToF, TAPVR/PAPVR, severe PS * * LAE * long and bifid P wave (P-mitrale) (>/= 0.10 secs) * infants < 1 yr may be > 0.08 seconds * biphasic P wave normal in V1 * MR
Rules of thumb for RVH and LVH 5,4,3,2,1 rule RVH * look at R wave in V1 RVH if * > 5 squares in <1mo * >4 squares in <1yo * > 3 squares in >1yo * look at S wave in V6 RVH if * > 3 squares in <1mo * >2 squares in <1yo * > 1 squares in >1yo LVH * look at R wave in V6 LVH if * > 3 squares in <1mo * > 4 squares in <1yo * > 5 squares in >1yo * look at S wave in V1 LVH if * > 1 squares in <1mo * > 2 squares in <1yo * > 3 squares in >1yo Size of the Ventricle changes as the infant grows RV is larger and thicker at birth because of the physiologic stresses on it during fetal development By Approximately 1 month of age, LV will be slightly larger By 6 months of age, the LV is twice the size of the RV and by adolescence it is 2.5 times the size
Ventricular Hypertrophy RVH RAD for the patient's age * rightward and anterior QRS axis * R in V1, V2, avr * S in I, V6 * abnormal R/S ratio in favor of right ventricle * R/S ratio in V1 * S/R ratio in V4-6 after 1 month of age * upright T in V1 (if <6yrs) * q wave in V1 (normal in 10% of neonates) * wide QRS-T angle with the T axis outside normal ranges
LVH * LAD for the patient's age * QRS voltages in favor of the LV * R in I, II, III, avl, avf, V5, or V6 (Pressure Overload: II, III, avf; Volume Overload: V5, V6) * S in V1 * abnormal R/S ratio in favor of LV * R/S Ratio in V1, V2 * Q in V5 and V6 > 5 mm coupled with Tall peaked T- waves * wide QRS-T Angle with T axis outside normal range * flat or inverted T waves in I or avf
CVH criteria * voltage criteria for both RVH and LVH (without BBB or pre-excitation) * voltage criteria for RVH or LVH with large voltages in other ventricle * large equiphasic QRS complexes in two or more limb leads or in V2 thru V5 (Katz-Wachtel Phenomenon)
Repolarisation (T wave) and ST segment * T waves should be inverted between day 3 and puberty (or at least > 6yrs) * < 6yrs, upright T wave in V1 = RVH (persistent inverted T wave normal until 18yrs) * T waves are always upright in V6 if inverted consider myocarditis or cardiomyopathy if T wave axis changes + QRS-T >90 suggests strain pattern Tall T waves * hyperkalemia * LVH * Benign early repolarisation Flat/low T-waves * Normal newborn * K * hypothyroidism * Myocarditis/Pericarditis * ischemia * Digitalis
Summary Reporting ECG Step-by-step approach * Rate * Rhythm * Axis * Intervals * Hypertrophy * Infarction