Correlation of the Size of Isolated Right Ventricular Infarction with the Changes of ST Segment in Dogs

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Abstract Vectorcardiographic, electrocardiographic, and hemodynamic changes in isolated infarction (infarct confined to the right ventricular free wall) were studied in 19 mongrel dogs. An isolated right ventricular infarction was produced by embolizing the right coronary artery with Spongel under closed chest conditions. The size of the infarct, identified by TTC staining, accounted for 6–65% (35.9±22.0%, mean ± SD) of the right ventricular free wall. The STx, STy, STz, and the spatial magnitude of the ST segment (STM) were continuously recorded with an automated, real‐time vectorcardiographic ST‐segment analyzer (ST‐monitor) using the Frank lead system. The cardiac index (CI) ratio (CI after embolization/CI before embolization) of all dogs with larger infarcts (infarct > 35% of the right ventricle) was below 1.0. In dogs with smaller infarcts (% RVI±35%), there were no differences in the hemodynamic data before and 4 h after embolization. In dogs with larger infarcts, however, pulmonary arterial pressure and heart rate 4 h after embolization were significantly decreased compared with those before embolization. In addition, right atrial pressure 4 h after embolization in the larger infarct group was significantly elevated compared with that in the smaller infarct group. In dogs with larger infarcts, STx, STy, and STM were significantly larger than in those with smaller infarcts both 15 min and 4 h after embolization. There were no significant correlations between infarct size and change in vectorcardiographic ST segments in the smaller infarct group. There was, however, a significant correlation between the size of the infarct (percent of right ventricle infarcted, % RVI) and the vectorcardiographic ST‐segment changes in the larger infarct group and in all dogs. These results suggest that an infarct size larger than 35% or the right ventricular free wall can induce detrimental hemodynamic changes and that the RV infarct size can be determined by vectorcardiographic ST deviation with a real‐time ST monitor using the Frank lead system.

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