Noninvasive techniques for diagnosis of carotid artery disease.

A VARIETY of noninvasive techniques have been advocated for the detection of carotid artery disease. These techniques may be divided into 2 major groups: 1) those that assess the carotid bifurcation directly (phonoangiography, 1 audio-frequency analysis of bruits, 2 Doppler ultrasonic scanning, 3 " 8 and real-time B-scan imaging 7) and 2) those that assess the hemo-dynamics of the carotid system distal to the bifurca-tion and that indirectly provide information about its morphology (ophthalmodynamometry, 8 ' 9 thermog-raphy, 10 ' " oculopneumoplethysmography, 12-13 and directional Doppler flow studies 1417). An increasing number of reports suggest that these techniques can be utilized in varying combinations to obtain information about the extent of athero-sclerosis at the carotid bifurcation, particularly for lesions that produce 60 to 75% or greater stenosis — in which hemodynamic changes might be expected. 18 " 21 There are certain situations in which this information may be of clinical merit, but one must be cautious about allowing this information to indicate one type of therapy over another. It is not with the studies themselves that there is concern but rather with the way in which the information obtained from these studies is currently being used. It is in this area, especially , that technologic advances have outpaced clinical knowledge. Why is there so much interest in these noninvasive studies? The major reasons seem relatively clear: 1) the belief that carotid atherosclerosis is bad, 2) a bias that one form of therapy (that is, surgery) is more effective for certain types of lesions than are other methods, and 3) the belief that these studies may be useful in the selection of patients for angiography and in planning medical or surgical treatment. In determining the clinical usefulness of these techniques, certain observations about carotid atherosclerosis must be considered: namely, it is a relatively common disorder , symptoms may occur when only minimal disease is present, and severe disease may be present and not produce any symptoms. 22 These observations suggest that there must be more to evaluating patients (and the worth of any noninvasive instrument) than merely being able to describe the pathologic anatomy of the carotid arteries. The pathologic change may be, and likely is, responsible for some of the symptoms we see, but its presence alone cannot be used as the major criterion for judging the need for any treatment modality (medical or surgical), although this clinical practice is …