(a) Two identical twins (female) moderately preterm, 2 kg weight. The parameters are identical: PR and QRS duration are the same and the QTc delta is only 1 ms. This could be nice evidence that ECG is a reliable diagnostic tool. (b) Normal newborn . See the right prevalence in the precordial leads normal for age. R wave in V1 is 25 mm and S wave in V6 is 11 mm, both at the upper limit. The ST segment is mildly depressed up to V4 but not pathologic. Low amplitude, flat or slightly negative T waves are normal in the first week of life. P axis tends to the second quadrant. The ventricular mean vector is oriented to the right side as expected in a newborn

(a) One-week-old female, HR 150 bpm, QRS axis 105°. (b) Close-up: there are artifacts in many leads (movement or hiccups). These waves do not alter the P and R sequence and hence must be an extracardiac phenomenon

Male neonate four day old; note the non-specific ST–T changes , normal for age

One-week-old boy with mild pulmonary hypertension due to dystocia. ST–T changes are diffuse and more than normal in the precordial leads

Three-day-old female. The right axis deviation is normal. There is a positive T wave in V1; till the first week of life, a positive T wave in V1 is considered non-pathologic; on the contrary from 7 days to 7 years, a positive T wave in V1 is a sign of right ventricle overload (pressure > volume)

Male, 3 day old with sinus bradycardia . A relative bradycardia that responds to stimuli should not be considered pathological. There is a marked right axis deviation and the left forces are poorly represented, as expected in a newborn

Preterm infant. A left ventricular prevalence can be noted. The QRS axis is vertical in lead I and is isoelectric and then about 90°. The absence of the expected right ventricle prevalence is typical of a preterm baby (the more severe the prematurity, the more pronounced the left prevalence)

Fifteen-day-old boy. P wave in DII with a regular axis in the second left quadrant; HR of 150 b/min normal for the age. The QRS axis is deviated to the right (150°) but as an isolated feature is not pathological. In the precordial leads, you can see a right ventricular dominance with “left forces” rightly still behind. In the right precordial leads, the ST segment is mildly depressed (horizontal-descendent non-pathologic change)

(a) One-month-old female. HR around 150 bpm; aVL is the most isoelectric lead placing the ventricular axis around 60°.The right prevalence vanishes and left precordial leads begin to be pronounced. (b) Close-up

Two-month-old baby boy. Normal sinus rhythm for age (> 150 bpm), QRS axis around 80°, normal. The T in V1 is negative, then normal; in lead III there is a negative T, not pathological. The QTc interval is 415 ms; at a glance the T ends just after the point equidistant from the R waves among which the T is included. At 150 bpm that describes a normal QT

Three-month-old female. Axes P, R, and T normally point to the second left quadrant (between 0° and 90°) consistent with age. The QRS in V1 can be defined as “mild delay of right intraventricular conduction” and not a RBBB

One-month-old female. A left ventricle dominance can be noted. The patient was a severe preterm with systemic hypertension (see Fig. 6.7)

Six-month-old female. In the frontal plane the most isoelectric leads are I and aVL, a fact makes it possible to place the QRS axis around 60° and 90° (second quadrant, physiological for age). The generous R wave in V2 is normal, and also the absence of a deep S wave in V6 excludes right ventricular hypertrophy

Nine-month-old male, normal

One-year-old boy. Note the notch in the right precordial leads

Other examples of right precordial notched T . The notch is normal but can simulate a blocked P

The most isoelectric lead is aVF, placing the QRS axis between the first and second quadrant (between 0°and −15°). Right side voltages are well represented but within normal limits