MONTREAL — Chest pain in patients with low coronary calcium scores may serve as a red flag for the presence of obstructive soft or uncalcified coronary atherosclerosis, Dr. John S. Ho said during a poster presentation at the annual meeting of the American Society of Nuclear Cardiology.
Dr. Ho based this conclusion on an analysis of 353 patients who underwent myocardial perfusion imaging (MPI) between 1998 and 2005, and whose calcium score was quantified with electron beam CT as 0–10 Agatston units.
Only 7 (2%) of 353 of patients had an abnormal scan. Despite these small numbers, the investigators were able to show a highly significant association between a history of chest pain and an increased frequency of an ischemic MPI study. Among symptomatic patients, 4% had an abnormal perfusion study, which is more than 10 times the frequency of an abnormal scan in those without chest pain.
Contrary to conventional thinking, the presence of traditional coronary risk factors—such as age, gender, family history of premature coronary heart disease, hyperlipidemia, and diabetes—was not predictive of an abnormal study, said Dr. Ho, a cardiologist with the Cooper Clinic in Dallas.
The absence of significant coronary artery calcification is associated with a low risk of subsequent adverse cardiovascular events, but rare cases of clinically significant ischemic heart disease do occur in individuals with a very low calcium score. Such cases are thought to be the result of a significant burden of soft or uncalcified plaque, predominantly in younger, female individuals, he said.
Overall, 50% of patients in the study had hyperlipidemia, 4.5% had diabetes mellitus, 34% had hypertension, 13% were current smokers, and 67% were overweight. Furthermore, 38% had a family history of heart disease, 30% had an abnormal ECG, and 30% had chest pain. Their mean age was 55 years, and 58% were male.
Some physicians believe that Framingham risk factors explain 90% of atherosclerosis, but Dr. Ho said that clinically, some patients have no risk factors or well-controlled risk factors and still have extensive disease. “Using coronary calcium is a measure of atherosclerosis, and a more direct means with which we can assess risk,” he said.
The protocol at the Cooper Clinic is to utilize calcium scoring for both asymptomatic and symptomatic at-risk patients. In patients with chest pain, the decision to perform nuclear stress testing is based on clinical judgment, Framingham risk scores, and Forester evaluation of chest pain, Dr. Ho said.
'Using coronary calcium is a measure of atherosclerosis, and a more direct means [to] assess risk.' DR. HO