The value of CT cardiac angiography and CT calcium score testing in a modern cardiology service in New Zealand: a report of a single centre eight-year experience from 5,237 outpatient procedures.

BACKGROUND: Computed tomographic (CT) cardiac angiography is of increasing value in several areas of patient management in cardiology. We assessed the ability of CT cardiac angiography to effectively 'rule out' severe coronary stenoses in patients presenting with 'atypical' symptoms and/or an equivocal stress test, which offers a new approach to the management of coronary artery disease. We also examined the use of the CT calcium score test in cardiovascular (CVS) risk assessment. METHODS: From a large single centre (Mercy Hospital) in Auckland, using a prospectively acquired, comprehensive database, we audited the entire eight-year experience of 5,169 patients (7/8/06 to 31/1/14) who underwent 5,237 64-slice computed tomographic (CT) cardiac angiogram or CT calcium score tests (GE Lightspeed scanner). RESULTS: From 5,169 patients there were 5,237 CT procedures. The mean patient age was 57 (SD 10) years; 42% patients were female. Of the 3,603 (69%) full CT cardiac angiogram scans, 3,509 (67%) included a calcium score test. One thousand four hundred and eighty-three (28%) of scans were a calcium score test only. Of the 3,603 (69%) full CT cardiac angiogram scans, it was possible to 'rule out' significant coronary atheroma (stenosis ≥50%) in 2,947 (82%) of these procedures. Of the 4,903 (94%) patients who had a CT calcium score test, in whom we could calculate the NZ Framingham-based CVS risk, it was possible to reassign 532 (22%) of these patients who were previously thought to be at 'low risk' to be at a higher CVS risk. CONCLUSION: CT cardiac angiography has become established in the modern management of cardiology patients. It has particular value as a tool to 'rule out' severe coronary stenoses, and as a tool to give a more accurate assessment of CVS risk. It adds significant value to the care of many patients within an established cardiology practice.

High calcium scores in patients with a low Framingham risk of cardiovascular (CVS) disease: implications for more accurate CVS risk assessment in New Zealand.

AIMS: New Zealand (NZ) patients are recommended to undergo an 'adjusted' Framingham score to assess their cardiovascular (CVS) risk. The current (2009) NZ CVS Risk Guideline does not recommend the use of a 'calcium score' as an additional risk tool, although it has been shown to be powerfully predictive of CVS events above the predictive power of traditional Framingham risk factors. Calcium scores of >400 are very strongly predictive of a future CVS event and give direct evidence of atheromatous disease in the coronary circulation. Identification of people with advanced, premature coronary atheroma would allow early treatment of those who may benefit from more vigorous preventative strategies, including statin therapy. METHODS: Using a prospectively acquired, comprehensive database we audited the first 1000 patients (7 August 2006 to 28 November 2008) to undergo a 64-slice computed tomographic (CT) cardiac angiogram (GE Light Speed), which included a scan for a 'calcium score', at the Mercy Hospital, Auckland. We excluded 58 patients who had experienced one or more of a previous myocardial infarction (MI) (n=21), coronary artery bypass graft (CABG) surgery (n=15), percutaneous coronary intervention (PCI) (n=13) or stroke (n=21) and who therefore already had definite evidence of vascular disease and would be automatically placed in a high risk strata. We calculated each patient's Framingham risk from the original 'Anderson' equation, used by the 1996 NZ CVS risk Guideline, and the 'adjusted' Framingham 5-year CVS risk using the NZ Guidelines Group 2003/2009 recommendations, and then compared this with the observed calcium scores. RESULTS: The mean patient age was 56 (SD 9) years; 364 (39%) patients were female, 82% patients were Caucasian. 41% were current (4.6%) or previous (36%) cigarette smokers, 35% had a history of hypertension, 44% hyperlipidaemia and 5.6% had diabetes mellitus. The percentage of patients at 'low' 5-Year CVS risk (0-10% 5-year risk), using the 1996 and 2003/2009 guideline methods, was 78% and 58% respectively. Of patients in these Framingham 'low-risk' groups, 10% and 8.8% had a calcium score of >400 Agatston units, indicating that they were actually at very high CVS risk, and 203 (28%) and 147 (27%) respectively had a calcium score of >100 Agatston units, indicating that they were actually at 'high risk' and not 'low risk'. CONCLUSION: Approximately 10% to 27% of patients with a low CVS risk as assessed by the established Framingham equation have a markedly increased calcium score and hence a significantly increased risk of a CVS event. Currently promoted methods of risk assessment may be inadvertently, falsely re-assuring these patients. Clinicians managing patients may consider a calcium score as an additional tool to the standard risk assessment strategies.