**2. Normal electrocardiogram tracing**

#### **2.1. Waves: intervals and segments**

The **P-wave** reflects atrial depolarization (contraction).

The **PR-interval** corresponds to the delay between the end of atrial depolarization (contraction) and the beginning of ventricular depolarization (contraction); its length must be between 0.120 s and 0.200 s.

The **Q wave** is a negative deflection in the ECG resulting at the beginning of ventricular depolarization (first wave in QRS complex).

The **T wave** is a reflection of ventricular repolarization.

The **QT interval** includes a complete ventricular depolarization and repolarization (full ventricular cycle); its length must be between 0.400 and 0.450 s (depending on authors and their conveniences since some authors have studied and published in different journals what the correct length of the QTc interval should be. Even they have not agreed with their different conclusions. We agree to Gollop, these values may vary; for us and with a broader context, the standard QTc values are between 0.400 and 0.450 s in length).

There are many formulas to measure the amount of these ranges; the most used are *Bazett and Fridericia* yet (**Figure 1**).

Like the R-R interval, the QT interval is dependent on the heart rate in an obvious way (the faster the heart rate, the shorter the R-R Interval and QT interval) and may be adjusted to improve the detection of patients at increased risk of ventricular arrhythmia.

The length of the PR (or PQ) interval, of the QRS complex, of the ST segment and the corrected QT interval, are all-important and must be valued in all cases.

The PR interval must be greater than 120 ms and lower than 200 ms.

symptoms that are considered mild, such as: Palpitations, usually nocturnal, which awaken the patient from the natural sleep. Profuse nocturnal sweating. Light-headedness feelings misinterpreted. 2. A feeling of chest pain very unspecified, not irradiated and whose electrocardiographic study is regarded, in the vast majority of cases, as nonspecific and atypical, since coronary alterations are not observed. 3. A personal background, in childhood, of seizures treated with antiepileptic drugs without the presence of an epileptic focus on the electroencephalogram. 4. Low levels of lythemia. 5. A preference for young age (up to 40) and

In 2008, Breijo-Marquez et al. [1–3] presented an electrocardiographic pattern, in which both the PR and QT intervals were shorter in milliseconds than what is regarded as acceptable

They called this phenomenon as *Decrease of electrical cardiac systole"*[1], since both, depolarization and repolarization, atrial and ventricular, are lower in their standard lengths (PR interval

It is well known that, in an electrocardiogram, there are different waves, intervals, and

In spite of the repeated repetition of the image, we put it below to gain a better understanding:

The **PR-interval** corresponds to the delay between the end of atrial depolarization (contraction) and the beginning of ventricular depolarization (contraction); its length must be between

The **Q wave** is a negative deflection in the ECG resulting at the beginning of ventricular depo-

The **QT interval** includes a complete ventricular depolarization and repolarization (full ventricular cycle); its length must be between 0.400 and 0.450 s (depending on authors and their conveniences since some authors have studied and published in different journals what the correct length of the QTc interval should be. Even they have not agreed with their different

male sex.

146 Cardiac Arrhythmias

limits.

and QT interval).

They are as follows:

0.120 s and 0.200 s.

**A. Waves**: P, Q, R, S, T.

**C. Segments**: ST fundamentally.

**2.1. Waves: intervals and segments**

larization (first wave in QRS complex).

**B. Intervals**: PR (for other PQ authors). QRS. QT.

**2. Normal electrocardiogram tracing**

The **P-wave** reflects atrial depolarization (contraction).

The **T wave** is a reflection of ventricular repolarization.

segments.

Otherwise, we would find a **"short PR"** if this is fewer than 120 ms.

If greater than 200 ms, it would be denominated like an *Auricle-ventricular block in any of its variants.*

The QRS complex should have a maximum length of 0.10 s. If it were longer lasting, we would be in front of a branch block in its different modalities (complete or incomplete).

**Figure 1.** Graphical representation of a normal heart cycle. Indicating the waves, segments and intervals in time (abscissa) and millivolts (ordinate).

The great controversy that persists to this date is about which should be considered as an average length of the QT interval since it is related to the heart rate, that is, the QT value is frequency—dependent.

As we have previously mentioned, the typical features of the **Breijo pattern** are:

As we have mentioned previously, we agree with Gollop et al. [9] on when the QTc interval

Breijo Electrocardiographic Pattern

149

http://dx.doi.org/10.5772/intechopen.75446

Gollop et al. have written over 61 cases of Short QT Syndrome. Their cohort of 61 cases was predominantly male (75.4%) and had a mean QTc value of 0.306 s with values ranging from 0.248 to 0.381 s in symptomatic cases. For Gollop et al., the overall median age at clinical presentation was 21 years (adulthood) [IQR: 17–31.8 years) with a value of 20 years (IQR:

These authors developed the ECG characteristics of the general population, and in consideration of clinical presentation, family history and genetic findings, a highly sensitive diagnostic

<370 1 <350 2 <330 3

<120 1

Sudden cardiac arrest 2 Polymorphic VT or VF 2 Unexplained syncope 1 Atrial fibrillation 1

First or second degree relative to SQTS 2 First or second degree relative to sudden death 1 Sudden infant death syndrome 1

Genotype positive 2 Mutation of undetermined significance in a culprit gene 1 Patients are deemed high probability (≥ 4 points), intermediate probability (3 points) or low probability (≤ 2 points).

**1.** A PR interval of fewer than 120 ms (short PR).

Both on the same electrocardiographic tracing.

duration ought to be considered as "**short**."

17–29 years) in males and 30 years (IQR: 19–44 years) in females].

**2.** A QTc interval fewer than 360 ms.

using a scoring system.

**QTc in ms**

**J point-T peak interval**

**Clinical history**

**Family history**

**Genotype**

This "scoring system" includes:

Several formulas are used to correct the QT interval (QTc). The most used are those of *Bazett and Fridericia.*

However, for these authors, typical values would be between 0.40 and 0.44 s, regardless of the person's age and sex.

The discrepancies among the different authors about the typical values of corrected QT are immense. These controversies are producing an authentic catastrophe when it comes to cataloging when it is or not a short QTC [4–8].

For us, in accordance with Gollop [9]—any QT value corrected interval less than 0.360 s must be considered as "short QT."


The most commonly used formulas are as follows (**Table 1**):

**Table 1.** Formulas for QTc measure.
