Restenosis following angioplasty is an iatrogenic disease of increasing 
frequency. Restenosis may be defined in terms of either angiographic or clinical 
criteria. Definitions of angiographic restenosis have varied in different 
studies, accounting in part for the differences in reported restenosis rates. 
Most studies now define angiographic restenosis as either a > 50% loss of 
initial gain or an absolute lesion stenosis of > or = 50% at follow-up 
angiogram. Common clinical end points used in defining restenosis include 
recurrent angina, need for repeat revascularization, or myocardial infarction. 
Despite technical advances and multiple pharmacologic interventions, most 
studies have found that the incidence of angiographic restenosis remains in the 
range of 40%; in none of these studies, however, was complete angiographic 
follow-up obtained, and thus actual restenosis rates may be somewhat higher. In 
several studies, clinical restenosis has been found to occur in approximately 
36-40% of patients. Thus, a minority of patients with angiographic restenosis 
have no clinical manifestations. Most patients who develop symptoms of 
restenosis develop these symptoms within the first 3 months after angioplasty. 
The presenting symptom in the majority of these patients is progressive 
exertional angina. Patients occasionally will present with unstable angina and 
only rarely with acute myocardial infarction. In patients who present with 
recurrent chest pain, several features have been found to be helpful in 
predicting whether they will have angiographic restenosis at follow-up 
angiography. Patients who present 1-6 months after angioplasty with typical 
anginal symptoms have a high likelihood of having angiographic restenosis. By 
contrast, patients who present more than 6 months after percutaneous 
transluminal coronary angioplasty with recurrent chest pain are more likely to 
have new, significant coronary lesions to account for their symptoms. 
Noninvasive testing in patients with clinical presentations suggestive of 
restenosis can, in general, add only modest information in predicting whether 
restenosis is indeed present. A negative exercise thallium test appears to have 
a high specificity in ruling out restenosis and may be helpful in patients who 
present with more atypical symptoms. Repeat angioplasty is the therapy most 
frequently utilized to treat restenosis, although coronary artery bypass surgery 
or medical therapy may be reasonable alternative therapies. Clinical success 
rates with repeat angioplasty are > 90%, and major complications are rare; 
however, restenosis will recur in a significant percentage of these patients. 
Some patients who develop such recurrent restenoses will ultimately benefit from 
a strategy of repeat angioplasties, although many will require surgical 
revascularization.