ABC | Volume 112, Nº6, June 2019

Case Report Riera et al Atrial and ventricular infarction: P-loop shape Arq Bras Cardiol. 2019; 112(6):803-806 Figure 1 – ECG/VCG correlation. A) ECG diagnosis: Left atrial enlargement (positive Morris index), PR-segment depression in I, II, III and aVF, low QRS voltage in the limb leads (the amplitude of all the QRS complexes in these leads is < 5 mm). QS Pattern from V 1 to V 5 , and low r voltage wave in lead V 6 . ST-segment elevation convex upward. B) VCG diagnosis: combination of anteroseptal anterior and anterolateral infarction: QRS loop directed to the back and minimally to the left near the orthogonal Z lead. The T-loop directed to the front with broad QRS/T angle (≈+170°). Conclusion Acute extensive anterior myocardial infarction. Possible association with atrial infarction. or anterolateral wall, which corresponds to the LA, will produce PR-segment elevation in lead I with reciprocal depression in leads II, III and the anterior precordial leads V2-V4. 7 However, there are no universally accepted criteria. Discussion Detailed ECG analysis revealed PR-segment displacement in several leads. With the aim to clarify this doubt, we isolated the P loop by VCG and enhanced its size 32-fold. We found that the P loop in VCG fulfilled criteria for biatrial enlargement (“Erlenmeyer-like” shape) (Figure 2) with notches in the central portion of the loop; this confirmed the suspicion of associated AI. The apparent contradiction of an atrial abnormality in VCG in conjunction with apparently normal atria on echocardiography could be explained by the fact that the echocardiogram is not an optimal method to evaluate the size of the RA and ventricle, particularly in the absence of concomitant right ventricular enlargement; therefore, enlargement of the RA could go unnoticed. On the other hand, LA dilatation is not unexpected in an extensive anterior infarction with increase in the end-diastolic pressures. However, in the initial stages post-MI, the atrial chamber size can still be normal, although VCG shows a clearly abnormal P loop. In Figure 2, the comparison with the normal P loop is shown in the 3 planes in this case (AI with biatrial enlargement). The role of atrial coronary perfusion is incompletely understood. One of the main limitations of our current understanding is that the origin of posterior LA coronary irrigation is unknown. 10 Currently, three coronary branches supplying blood to the atria are known: 1. The right anterior atrial artery or sinus node artery, and other small branches arising from the right coronary artery, such as the right intermediate atrial artery. 2. The “ramutis ostii cavae superioris” or left anterior atrial artery which arises from the left main coronary artery, the proximal portion of the left circumflex (LCX), obtuse 804