Comment on the above paper
In the current study by Williams et al, the added value of the number of calcified lesions in addition to the total calcium score was explored. With calcium scoring, an estimate of the total (calcified) plaque burden in the coronary tree is obtained, and its prognostic value has been established in numerous studies. However, total calcium score does not take the location of the calcific plaque into account. Also, the presence of multiple small calcium deposits rather than focal calcified lesions, a phenomenon that has been linked to acute coronary syndromes, is not reflected by the total calcium score. Accordingly, additional prognostic information could theoretically be derived.
A large cohort of asymptomatic patients (n= 14,659) were followed for an average of 6.8 years after initial calcium scoring. No prior history of coronary artery disease was present, although all patients presented with at least 1 risk factor. In addition to the total coronary calcium score, the number of calcified lesions was recorded in total as well as for each coronary artery.
On average, patients with higher number of calcified lesions were older, more often male and presented more often with risk factors such as diabetes. After an average follow-up of 6.8 years, 281 deaths occurred, resulting in an adjusted Cox survival of 99.2% after 5 years. A strong relationship between increasing number of calcified lesions and decreasing survival was noted. Annual mortality rate exceeded 1% per year for patients with ≥10 calcified lesions. Moreover, in patients with ≥20, this percentage exceeded 2%. However, when compared against the prognostic information obtained from the total calcium score, only minimal additional value was observed. Accordingly, it appears that risk stratification based on total calcium score is accurate, regardless of this score represents few larger or numerous small calcifications.
Importantly however, when considering also location of the lesions, a significantly higher mortality rate was observed in the presence of lesions located in the left main coronary artery as compared to other coronary arteries. For example, the presence of 6 or more lesions in the left main coronary artery was associated with a significantly increased mortality of 13% per year. Mortality also increased with the presence of elevated calcium scores in the left main coronary artery. Similar observations were noted for the left anterior descending coronary artery. Accordingly, the current findings support the relatively greater prognostic impact of the left main and left anterior descending coronary artery, as demonstrated in previous studies.
A few limitations should be acknowledged. As the authors state, the influence of multiple small calcifications on the occurrence on non-fatal cardiovascular events, including myocardial infarction or unstable angina, remains to be determined. Moreover, only asymptomatic patients were studied. Accordingly, the potential incremental value of multiple spotty calcifications for risk stratification in symptomatic patients, including those presenting with acute coronary syndromes, remains to be elucidated
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