Electrocardiographic patterns in acute inferior myocardial infarction with and without right ventricle involvement: Classification, diagnostic and prognostic value, masking effect

Background: In acute inferior myocardial infarction (AIMI), the ST depression from V₁ to V₄ has been the subject of many papers, while the ST changes in other leads, their association, and the right ventricular (RV) involvement have been studied less. Hypothesis: This study was performed to contribute to the meaning of the ST changes and RV involvement in AIMI. Methods: Seventy-one patients, admitted within 6 h from symptom onset, all thrombolysed, were enrolled. We classified them according to ST patterns and RV involvement. We divided the right coronary artery into three segments, considering the origin of RV branch and the crux as dividing points. We established a coronary score attributing 2 points to each terminal branch. Comparisons were performed between the electrocardiographic (ECG) findings at onset, the creatine phosphokinase (CPK) peaks, the radionuclide ejection fractions, and the coronary angiographies. Results: We found that the ST changes give indications regarding the site, extension, and extent of AIMI; RV involvement can mask posterior extension, points to the right coronary as the culprit vessel (100%), and, with high probability, indicates the proximal segment as the site of the lesion; the ECG signs of isolated AIMI indicate a peripheral obstruction; and a collateral circulation may appear relatively early. Conclusions: Our findings prove the diagnostic and prognostic value of the ST changes and RV involvement at the onset of AIMI and suggest that the higher in-hospital mortality and complication rates found with RV involvement and reported in the literature are related more to posterior extension, masked by RV involvement than to this involvement per se. Furthermore, these findings prove the clinical value of our classification of the AIMIs and distinction in segments of the fight coronary artery.