Abstract

<p>n 2008, Professor Breijo-Márquez described an electrocardiographic pattern consisting of the presence of a short PR (or PQ) <br>interval together with a short QT interval in the same individual. It was published under the headline "Decreased cardiac <br>electrical systole" in the International Journal of Cardiology (IJC) [1]. <br>From then until today, this electrocardiographic pattern is increasingly studied and diagnosed by various cardiologists, both in <br>isolation and as part of other well-known entities in cardiology (to be described below). <br>As is well known, the PR interval on the ECG tracing represents the distance from the onset of atrial depolarization (P wave) to <br>the onset of ventricular depolarization (QRS complex). Normalized values, considered within normal ranges, range from 0.120 <br>milliseconds to 0.200 milliseconds (below the 0.120 millisecond digit is considered "short"; above the 0.200 millisecond value <br>is considered "atrioventricular block")[2]. <br>Similarly, it is also well known that the QT interval includes both ventricular depolarization (QRS complex) and ventricular <br>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 <br>branch of the T wave, when this branch reaches the isoelectric line of the electrocardiographic (ECG) tracing. <br>However, at present there are still many discrepancies as to which values should be considered as standard when it comes to <br>the QT interval. <br>The standard values for the length of this interval are not precisely uniform for all authors. For most authors, including us, the <br>values range from 0.360 milliseconds to 0.450 milliseconds (for some authors in women they would be in ranges up to 0.460 <br>milliseconds). <br>The shortening of the PR interval by less than 0.120 milliseconds makes the myocardium more unstable and more prone to <br>cause cardiac electrical disturbances, which can lead to serious arrhythmias that can be life-threatening; the most frequent <br>arrhythmias are tachyarrhythmias in their different types and etiologies [2]. <br>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 <br>cardiac death, but it is still not well and completely defined, and information on long-term follow-up remains very scarce at the <br>moment [3]. <br>A short QT interval is the major component, but because of a strange relationship between the QT interval and the RR interval<br>in patients with a short QT interval, the shortened QT interval in such patients is often only apparent at a heart rate near 60 <br>bpm. <br>In fact, a large percentage of physicians consider electrocardiographic tracings carrying the aforementioned pattern to be within <br>normality, when in fact this is not the case. <br>Because routine ECGs are usually taken at a higher than normal heart rate, many patients with cardiac electrical involvement <br>may go undetected [3]. <br>Many mutations are responsible for the short QT interval, but in published families, only one in four were found, which have <br>been genetically tested [4, 5]. Thus, most diagnoses are based on the patient's own clinical presentation with a relative who has died suddenly, and the latter <br>is also difficult to prove. The treatment of choice is an implantable defibrillator [4,5, 6]</p>