Functional assessment of PTCA results by stress echocardiography: when and how to test.

Angiographic follow-up has shown that restenosis after PTCA is a continuous and ubiquitous process rather than a dichotomous event. Since the functional significance of restenosis involves more factors than minimal lumen diameter, functional tests after PTCA cannot be expected to match exactly the degree of angiographic restenosis. In the past, nuclear perfusion imaging has been the most accurate non-invasive method to predict restenosis, but now there is a new technique: stress echo. This uses physical (treadmill, exercise), pharmacological (dipyridamole, dobutamine), or pacing stress (together with transoesophageal imaging) for the detection of stress-inducible wall motion abnormalities; resolution of resting abnormalities may also be observed. These stress modalities have been employed to detect restenosis in limited numbers of patients, with diagnostic accuracies (so far, except for dobutamine) comparable to nuclear imaging. Therefore, it seems that the decision to use echo stress testing depends on patient characteristics, availability of methods, and, importantly, experience of the echo laboratory. Timing of the test after PTCA must take into account delayed functional recovery after PTCA; this has been well described by nuclear perfusion imaging. Thus, very early (< 1 month) tests lack specificity. On the other hand, development of restenosis after 6 months is rare. Stress tests therefore should be performed within the time window of 1 to 6 months after PTCA.