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When your CAC scan comes back with calcium in the right coronary artery, the natural question is: how worried should I be? The answer, as with most things in cardiovascular medicine, is that context is everything. RCA calcium is real, it matters, and it tells your physician something important about the state of your arteries, but it doesn't carry the same weight as calcium in the LAD or left main artery. Understanding why, and what RCA calcium does and doesn't predict, makes you a more informed participant in your own cardiovascular care.
The right coronary artery supplies blood primarily to the right side of the heart and, in most people, to the inferior wall of the left ventricle and the electrical conduction system. Like all coronary arteries, it can accumulate calcified plaque over time as part of the atherosclerotic process. A CAC scan detects and quantifies this calcium using a standard Agatston scoring method, and vessel-specific scores are generated for each of the four major coronary arteries, the left main, LAD, left circumflex (LCx), and RCA, alongside the more familiar total score.
RCA calcium, like calcium anywhere in the coronary tree, is a marker of underlying atherosclerosis. Its presence confirms that plaque has been building, likely for years. The question is not whether it matters at all, but how much prognostic weight it carries relative to calcium elsewhere, and the answer, as the research makes clear, is that it carries less than most people assume.
When researchers account for calcium in all four coronary vessels simultaneously, only the left main and LAD emerge as statistically significant independent predictors of mortality (p < 0.0001 for both). The RCA and LCx lose their independent predictive power in that multivariate model. This doesn't mean RCA calcium is irrelevant; it means that much of what RCA calcium predicts is already captured by calcium elsewhere, particularly in the higher-risk left-sided vessels.
The mortality numbers illustrate the gap clearly. For patients with extensive calcification of more than 20 lesions, annual mortality rates in the RCA territory range from approximately 5 to 10%. That is a meaningful risk, but it is substantially lower than the 27% or higher annual mortality rates associated with comparable lesion burdens in the LAD or left main territory. The RCA is, in relative terms, the lower-stakes vessel.
The relationship between RCA calcium and ischemia, reduced blood flow to heart muscle, is also weaker than for the LAD or LCx. In patients with moderate or severe ischemia in the RCA territory, mean calcium scores were 261 ± 321, compared to 114 ± 237 in those with no or mild ischemia (p = 0.045). That difference is statistically significant, but when researchers ran a multivariate analysis, only age and male gender remained independently associated with high RCA calcium scores. Ischemia severity itself dropped out. This contrasts with the LAD and LCx, where moderate or severe ischemia remained an independent predictor of high calcium even after adjusting for other variables. The implication is that RCA calcium is more a marker of general aging and systemic atherosclerotic burden than a direct signal of territory-specific flow limitation.
Where RCA calcium does gain prognostic traction is in the context of multivessel disease. Patients with calcium in multiple arteries, including the RCA, experience higher event rates than those with disease confined to a single vessel. The number of vessels involved, whether one, two, three, or all four, provides incremental prognostic information beyond the total Agatston score alone, with each additional vessel carrying higher risk of all-cause mortality and coronary events. RCA calcium, in other words, is most important not as an isolated finding but as a contributor to the broader pattern of how widely atherosclerosis has spread.