ACS, risk stratification, and coronary CT angiography

We had a cardiology subspeciatly morning report today where we discussed an elderly patient presenting with a classical history for unstable angina. 

This patient twice had bypass surgery, and multiple PCI subsequent who now presents with worsening retrosternal chest pain both at rest and with minimal exertion increasing in intensity and duration with diminishing relief with nitro.

Investigations revealed no new ECG changes and serial troponins were negative; however given how 'good' the story was for ischemic heart disease, the patient was admitted and treated as ACS with consultation to cardiology for further management. 

In this particular case the patient stabilized in hospital with a plan to arrange angiography for potential symptom relief in the near future. 

This case though classic, raised a couple very interesting points.

To cath or not to cath:

This patient has obvious risk factors for coronary disease and a convincing history as such. However the point was raised as to how one would know (in the absence of potentially localizing ECG changes) where the target lesion was? Given his history of bypass and multiple PCI's, it is possible that he has multiple areas of potentially significant occlusion, but which exactly is the target would be difficult to know.

One strategy to address this would be to arrange a nuclear scan or stress ECHO prior to the angiography, with hopes of localizing the target area.

What about for less obvious cases?

We then discussed patients at lower risk for ischemic heart disease and to what extent they should be worked up.

Specifically we discussed coronary CT angiography (CCTA). There are multiple studies looking at CCTA including the Rule Out Myocardial Infarction Using Computer Assisted Tomography II (ROMICAT-II) from the NEJM in 2012. This study randomly assigned 1000 patients presenting with chest pain to either CCTA or standard evaluation (which may not have been any testing) and found that time from presentation in the ER to discharge was shortened with only slightly higher incurred costs. The downside was the increased radiation exposure from the CT. 

This study along with others support that CCTA is a useful rule out test in patient with low-intermediate risk for acs, though at the cost of radiation exposure (though now with better technology the amount radiation is lowering).

One important question, is whether any further testing is required at all for low-intermediate risk patients. One could argue that in these patients, given their low risk profile, that they could be safely discharged without any further testing.  These factors and more need to be considered when weighing the risk/benefits/costs of further testing such as CCTA in evaulating this subset of patients. 

Click here for the NEJM article