Blockage of which blood vessel would most likely cause ischemia of the right side of the heart, including the interventricular septum and posterior walls of both ventricles?

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The heart’s muscle is fed by its own coronary arteries, and which vessel supplies a region determines where ischemia will show up when a blockage occurs. In most hearts, the right coronary artery (RCA) gives rise to the posterior descending artery (PDA), which travels in the posterior interventricular sulcus and supplies the posterior portion of the interventricular septum and the posterior walls of both ventricles. So a blockage of the RCA deprives these specific areas of blood flow, leading to ischemia there, which matches the described region—the right side of the heart including the interventricular septum and the posterior ventricular walls.

The left coronary artery, by contrast, mainly supplies the anterior wall and much of the interventricular septum through the left anterior descending and circumflex branches, not the posterior regions, especially in right-dominant circulation. The pulmonary artery and the aorta aren’t the myocardial blood supply routes; occluding them would cause very different, broader circulatory problems rather than focal ischemia of these posterior regions.