as it has a high false-positive rate in this population and a radiation hazard.
Table 3.1 Indications for stress imaging, as opposed to plain treadmill stress ECG.
| Treadmill stress imaging (nuclear or echo) >Treadmill stress ECGBaseline ST depression >1 mmaHigh pre-test probability of CADPrior coronary revascularization (stress imaging allows localization of ischemia and has a higher sensitivity in detecting single-vessel ischemia)Prior stress ECG with intermediate result Pharmacological stress imaging (nuclear or echo)Unable to walkAble to walk but baseline ECG has LBBB or ventricular paced rhythm (classically, pharmacological nuclear imaging is performed)b |
a LVH without ST depression is appropriately tested with stress ECG.
b Exercise and dobutamine may exaggerate the septal motion abnormality and septal defect present in LBBB, falsely suggesting ischemia, but have shown an appropriate yield when the apical motion or perfusion is analyzed, rather than the septum.25
Table 3.2 Risk stratification with stress testing.
| High risk: yearly cardiac mortality >3%, yearly cardiac events >5%DTS ≤–11aReversible, large or severe perfusion defect (summed stress score >+8, corresponding to ischemia involving >10% of the myocardium)Fixed, large or severe perfusion defect with LV dilatation/low EFRest- or stress-induced LV dysfunction with EF ≤35%, even if the defect is mild or moderateOn stress echo: ischemia of ≥3 segments (out of 17), or >one coronary distribution, especially if it occurs at a low rate <120 bpm or a low dose of dobutamine (≤10 mcg/kg/min) Intermediate risk: yearly cardiac mortality 1–3%, cardiac events 1–5%DTS –10 to +4Summed stress score 4–8 Low risk: yearly cardiac mortality and cardiac events <1% (~0.5% with stress imaging)DTS ≥+5 (≥ +8 is very low risk)No perfusion defect or small perfusion defect with a summed stress score <4 |
a Duke Treadmill Score (DTS) = prognostic score for treadmill stress testing
= Exercise time on Bruce protocol – 5 × (the deepest ST depression on ECG) – 4 × (angina score) (Angina score: 0 = no angina, 1 = non-limiting angina, 2 = exercise-limiting angina)
E. Risk stratification with stress testing
Treadmill stress ECG, more specifically the Duke Treadmill Score (DTS), is a powerful risk stratifier. A high-risk DTS implies an increased cardiac mortality and a 75% probability of left main or three-vessel CAD, regardless of imaging results. A low-risk DTS often implies a low mortality; however, ~10% of patients with a low-risk DTS have severe three-vessel or left main disease with a high mortality, and another 10% have two-vessel or proximal LAD disease, and thus, 20% of symptomatic patients with normal stress ECG have significant, high-risk CAD (particularly men).22 These patients are likely to be picked up by stress imaging.23,24 In fact, a high-risk result on nuclear or echo stress imaging overrules a low- or intermediate-risk result on stress ECG.23,24 Thus, stress imaging is preferred to stress ECG in patients with a high probability of CAD or with prior coronary revascularization even if ECG is interpretable, while stress ECG is preferred in patients with an intermediate or low CAD probability who are able to walk and have an interpretable baseline ECG (Table 3.1).18
A high-risk DTS, on the other hand, implies a high risk regardless of imaging results, with a 75% probability of left main or three-vessel CAD and >90% probability of any significant CAD.22 Because of balanced ischemia, some patients with extensive disease have normal or mildly abnormal perfusion imaging but are picked up by ECG variables, DTS, severe angina during testing, and post-stress LV dysfunction. Table 3.2 stratifies the risk according to stress testing.
In patients who have undergone PCI: (i) chest pain relief followed by recurrence months later is typical of in-stent restenosis, or progression of moderate disease outside the stented area (especially in patients who initially presented with ACS); (ii) a persistent chest pain without a pattern of relief and recurrence suggests either non-cardiac pain or residual, non-revascularized disease. The same applies to patients with prior CABG (graft disease instead of in-stent restenosis). Repeat the coronary angiogram if typical angina occurs on mild exertion.
Warranty periods
When should stress testing be repeated in patients with prior negative studies who present with chest pain? Stress tests have “warranty periods” during which the risk of cardiovascular events is low (<1% per year) and during which there is no need to perform a coronary angiogram unless the patient has objective evidence of new CAD, such as ACS with positive cardiac markers or new, severe ischemia on the ECG.
This “warranty period” of a stress test varies according to the context, and is generally 1-2 years, less so for pharmacological testing, older age (>70-80), CAD history, or uncontrolled risk factors.26
When a coronary angiogram shows normal coronary arteries or minimal disease, the risk of coronary events is low for 5 years, and unless there is evidence of MI, the angiogram is not usually repeated within the next 5 years. As per the CASS registry, the 7-year survival is 96% for patients with normal EF and normal coronaries and 92% for patients with mild coronary disease <50% (much better prognosis than obstructive CAD).27
How about patients who had a coronary angiogram showing single- or multivessel moderate disease (30–70%), or showing severe disease (>70%) in a small branch where PCI is not beneficial? If they present with recurrent or persistent chest pain a few months or 1–2 years later, the coronary angiogram may not need to be repeated unless there is an ischemic ST abnormality, a positive troponin, or a dramatic change in the severity of a typical, exertional angina. Also, the true functional significance of moderate stenoses (50–70%) is worth assessing with stress imaging or FFR.
Patients with moderate stenoses that are insignificant by FFR have a very low risk of MI from each individual stenosis, yet the summation risk of MI from all nonsignificant lesions is not negligible, ~1.5% per year (FAME 2 trial).28
These “warranty periods” are used for guidance; ultimately, decisions are based on clinical judgment.
F. Putting it together: diagnostic approach and management of chronic chest pain (Figure 3.2)
Figure 3.2 Proposed diagnostic approach to chronic chest pain. Note that CTA has gained a central role in high CAD probability and high-risk patients, including high-risk stress test, thanks to ISCHEMIA trial. The main goal of CTA in high-risk patients is to rule out left main disease, in which case conservative management is acceptable. The only exception is CKD (GFR<60), wherein stress imaging is preferred for diagnosis, keeping in mind that even a high-risk result is appropriately managed conservatively with no angiographic assessment at all. The solid arrows
