Electrocardiographic Anomalies and Their Underrated Role in Sudden Cardiac Events

In 2008, Professor Breijo-Márquez described an electrocardiographic pattern consisting of the presence of a short PR (or PQ) interval together with a short QT interval in the same individual. It was published under the headline "Decreased cardiac electrical systole" in the International Journal of Cardiology (IJC) 1. From then until today, this electrocardiographic pattern is increasingly studied and diagnosed by various cardiologists, both in isolation and as part of other well-known entities in cardiology (to be described below). As is well known, the PR interval on the ECG tracing represents the distance from the onset of atrial depolarization (P wave) to the onset of ventricular depolarization (QRS complex). Normalized values, considered within normal ranges, range from 0.120 milliseconds to 0.200 milliseconds (below the 0.120 millisecond digit is considered "short"; above the 0.200 millisecond value is considered "atrioventricular block") 2. Similarly, it is also well known that the QT interval includes both ventricular depolarization (QRS complex) and ventricular repolarization; it spans from the beginning of the Q wave (if present) or the beginning of the R wave to the end of the descending branch of the T wave, when this branch reaches the isoelectric line of the electrocardiographic (ECG) tracing. However, at present there are still many discrepancies as to which values should be considered as standard when it comes to the QT interval. The standard values for the length of this interval are not precisely uniform for all authors. For most authors, including us, the values range from 0.360 milliseconds to 0.450 milliseconds (for some authors in women they would be in ranges up to 0.460 milliseconds). The shortening of the PR interval by less than 0.120 milliseconds makes the myocardium more unstable and more prone to cause cardiac electrical disturbances, which can lead to serious arrhythmias that can be life-threatening; the most frequent arrhythmias are tachyarrhythmias in their different types and etiologies 2. Short QT interval (equal to or less than 0.350 milliseconds) appears to be a rare form of channelopathy with a high risk of sudden cardiac death, but it is still not well and completely defined, and information on long-term follow-up remains very scarce at the moment