In the aging patient population seen routinely in the noninvasive vascular laboratory, the possibility of Doppler waveform abnormalities secondary to cardiac effects, rather than localized obstructive disease, should be kept in mind. These abnormalities present in a variety of ways in both the arterial and venous systems, but they tend to follow two general rules. First, cardiac effects are systemic; for example, on the arterial side the carotid arteries, aorta and femoral arteries would all be affected to some degree. Second, cardiac effects are bilateral; thus, if an abnormality is only seen in one carotid artery, it is likely a carotid problem. If the same abnormality is seen in both carotid arterial systems, one should at least consider a cardiac source. Common causes of waveform abnormalities include congestive heart failure (elevated right heart pressures), arrhythmias, aortic stenosis and aortic insufficiency, and a number of nonpathologic etiologies. Although the Doppler waveform will appear abnormal in these cases, it should still be possible to acquire the quantitative velocity information necessary to reach a diagnosis regarding the presence and severity of any peripheral vascular disease as well.