A three-dimensional computed model of ST segment abnormality in type 1 Brugada Pattern: A key role of right ventricular outflow tract orientation?

Since its first description, Brugada Syndrome is characterized by definite ECG abnormalities (J wave, elevated ST segment) confined in right precordial leads. Brugada Pattern (BP) could be found in one or more right precordial leads, at conventional or higher intercostal spaces. A recent study, conducted by our group, reported that slightly less than one half of patients with type 1 BP show a definite ST segment depression (≥0.1 mV with duration ≥ 0.08 s) in the inferior leads. With these premises, 4 distinct ST abnormalities phenotypes can be recognizable in Type 1 BP. We speculated the key role of orientation of right ventricular outflow tract in the thorax, particularly the inclination of anterior wall compared to the sternum, contributing to the determination of these various ECG phenotypes. An interactive program, ECGsim, able to simulate ECG appearance in several anatomical and electrical models, confirmed this assumption. This computed model affirmed the strict relationship between ST segment depression in the inferior leads and the ST segment elevation in right precordial leads, typical of type 1 BP. A horizontal right ventricular outflow tract, in fact, gives raise to abnormal BP vector directed both superiorly and anteriorly, explaining, at the same time, typical BP appearance in right precordial leads and ST segment depression in the inferior leads.

Consideration of QRS complex in addition to ST-segment abnormalities in the estimation of the "risk region" during acute anterior or inferior myocardial infarction.

The myocardial area at risk (MaR) is an important aspect in acute ST-elevation myocardial infarction (STEMI). It represents the myocardium at the onset of the STEMI that is ischemic and could become infarcted if no reperfusion occurs. The MaR, therefore, has clinical value because it gives an indication of the amount of myocardium that could potentially be salvaged by rapid reperfusion therapy. The most validated method for measuring the MaR is (99m)Tc-sestamibi SPECT, but this technique is not easily applied in the clinical setting. Another method that can be used for measuring the MaR is the standard ECG-based scoring system, Aldrich ST score, which is more easily applied. This ECG-based scoring system can be used to estimate the extent of acute ischemia for anterior or inferior left ventricular locations, by considering quantitative changes in the ST-segment. Deviations in the ST-segment baseline that occur following an acute coronary occlusion represent the ischemic changes in the transmurally ischemic myocardium. In most instances however, the ECG is not available at the very first moments of STEMI and as times passes the ischemic myocardium becomes necrotic with regression of the ST-segment deviation along with progressive changes of the QRS complex. Thus over the time course of the acute event, the Aldrich ST score would be expected to progressively underestimate the MaR, as was seen in studies with SPECT as gold standard; anterior STEMI (r=0.21, p=0.32) and inferior STEMI (r=0.17, p=0.36). Another standard ECG-based scoring system is the Selvester QRS score, which can be used to estimate the final infarct size by considering the quantitative changes in the QRS complex. Therefore, additional consideration of the Selvester QRS score in the acute phase could potentially provide the "component" of infarcted myocardium that is missing when the Aldrich ST score alone is used to determine the MaR in the acute phase, as was seen in studies with SPECT as gold standard: anterior STEMI (r=0.47, p=0.02) and inferior STEMI (r=0.58, p<0.001). The aim of this review will be to discuss the findings regarding the combining of the Aldrich ST score and initial Selvester QRS score in determining the MaR at the onset of the event in acute anterior or inferior ST-elevation myocardial infarction.