Renal artery stenosis and ischemic nephropathy.

Renal artery stenosis (RAS), in its most severe form, can result in diminished renal function and loss of kidney mass. The prevalence of ischemic nephropathy is greatly under-appreciated in the elderly population and is the source of substantial morbidity and mortality. Diagnostic tests for RAS in patients with renal insufficiency are problematic, and medical therapy does little to slow the natural progression of the disease. Renal artery stenting can achieve long-term vessel patency and has been shown to preserve renal function. Proper technique and careful case selection are critical to the success of such procedures. Large-scale trials are needed to clearly identify groups of patients who will benefit most from percutaneous revascularization.

Percutaneous arterial aortoiliac intervention.

Historically reconstructive vascular surgery, has been a cornerstone of treatment for symptomatic obliterative aortoiliac disease. Surgical results include a reported aortobifemoral bypass 5-year patency rate from 85% to 90% and a 10-year patency rate of 70% to 75%. Operative mortality for aortoiliac reconstruction ranges from 1.6% to 3.3%, with an aggregated systemic morbidity of 8.3%. Clinical indications for surgical intervention are well-established and are limited primarily to severe claudication and limb-threatening ischemia. Broader application of surgical intervention is not recommended because of significant morbidity and mortality associated with the procedure. As balloon angioplasty and endovascular stenting technologies evolve, they are proving to be an effective modality for the treatment of aortoiliac disease. These lower risk procedures have allowed expansion of traditional indications for intervention. Treatment is recommended presently for patients with clinical symptoms that impact lifestyle and professional requirements. Less conventional indications include allowing access for coronary intervention or for placement of an intra-aortic balloon pump, or improving inflow prior to a distal surgical bypass procedure. Results of aortoiliac percutaneous interventions are difficult to compare with surgical data since methods and technology continue to improve and evolve, and randomized studies are limited. It is clear that as long as outcomes of percutaneous interventions are predictable and secondary patency rates acceptable, the low complication rates of a percutaneous intervention are clearly preferable to a riskier surgical alternative.

Use of fractional myocardial flow reserve to assess the functional significance of intermediate coronary stenoses.

The goal of the present study was to compare the use of pressure-derived myocardial fractional flow reserve for detecting ischemia with nuclear stress imaging in patients undergoing stent placement for intermediate coronary lesions. We demonstrated that myocardial fractional flow reserve detects ischemia in intermediate coronary lesions accurately when compared with nuclear stress imaging.

Intracoronary Doppler assessment of moderate coronary artery disease: comparison with 201Tl imaging and coronary angiography. FACTS Study Group.

BACKGROUND: Coronary angiography may not reliably predict whether a stenosis causes exercise-induced ischemia. Intracoronary Doppler ultrasound may enhance diagnostic accuracy by providing a physiological assessment of stenosis severity. The goal of this study was to compare intracoronary Doppler ultrasound with both 201Tl imaging and coronary angiography. METHODS AND RESULTS: Fifty-five patients with 67 stenotic coronary arteries underwent coronary angiography with intracoronary Doppler ultrasound and had exercise 201Tl testing within a 1-week period. Coronary flow reserve was measured, and analyses were performed by independent core laboratories. The mean stenosis was 59+/-12%; 51 of 67 stenoses were intermediate in severity (40% to 70%). A coronary flow reserve < 1.7 predicted the presence of a stress 201Tl defect in 56 of 67 stenoses (agreement=84%; kappa=0.67; 95% CI=0.48 to 0.86). In the patients who achieved 75% of their predicted maximum heart rate, the Doppler and 201Tl imaging data agreed in 46 of 52 stenoses (agreement=88%; kappa=0.77; 95%CI=0.57 to 0.97). Scatter was evident when angiography was compared with coronary flow reserve (r=.43), and the angiogram did not reliably predict the results of the 201Tl stress test (kappa=0.21; agreement=57% to 63%). CONCLUSIONS: Doppler-derived coronary flow reserve accurately predicts the presence of exercise-induced ischemia on stress 201Tl imaging, and coronary angiography does not reliably assess the physiological significance of an intermediate coronary stenosis.

Correlations between coronary flow reserve measured with a Doppler guide wire and treadmill exercise testing.

We compared exercise test results to a physiologic depiction of stenosis severity, coronary flow reserve (CFR), measured with a Doppler guide wire in 35 patients with single-vessel coronary disease. Group 1 (n = 21) had abnormal CFR, and group 2 (n = 14) had normal CFR. In group 1, 14 of 21 had ST-segment depression versus 3 of 14 in group 2 (p < 0.01). Exercise treadmill time (Bruce protocol) was normalized to the age- and sex-predicted time. Exercise time and normalized exercise time were less in group 1 (5.6 +/- 2.3 vs 9.9 +/- 1.8 min and 0.82 +/- 0.32 vs 1.25 +/- 0.23, p < 0.00001). Having either ST-segment depression or a normalized exercise time <1 during exercise had a 95% sensitivity, 71% specificity, and 86% predictive accuracy in identifying abnormal CFR. Coronary stenoses and minimal lumen diameter were similar in groups 1 and 2. By using stepwise logistical regression analysis, exercise time and ST-segment depression predicted CFR with a total r2 of 0.51. Minimal lumen diameter did not significantly add to the model. Exercise test variables, ST-segment depression, and exercise time are predictive of the physiologic significance of coronary lesions.

Clinical application of coronary flow reserve using an intracoronary Doppler guide wire.

Coronary flow reserve (CFR) is a critical measurement in the assessment of the coronary circulation. The development of this physiologic variable in animal and human studies is reviewed. Human studies documenting the limitations of coronary angiography, especially in the setting of severe diffuse coronary artery disease, are analyzed. Furthermore, the important variables that must be accounted for when CFR is measured are examined. With this background, the application of CFR in a variety of clinical settings and the development and use of the Doppler FloWire for its measurement are discussed.

Intracoronary Doppler guide wire versus stress single-photon emission computed tomographic thallium-201 imaging in assessment of intermediate coronary stenoses.

OBJECTIVES: The purpose of this study was to compare measures of coronary flow reserve by an intracoronary Doppler guide wire with results of stress single-photon emission computed tomographic (SPECT) thallium-201 imaging in patients with intermediate coronary artery disease (40% to 70% stenosis). BACKGROUND: Visual assessment of the coronary arteriogram as a means of predicting the physiologic significance of intermediate coronary stenoses is inaccurate. Coronary flow reserve is a reliable marker of the functional importance of a coronary lesion. The recent development of an intracoronary Doppler guide wire permits routine assessment of coronary flow reserve distal to coronary artery stenoses. METHODS: We prospectively evaluated coronary flow reserve in 30 subjects with intermediate stenoses using an intracoronary Doppler guide wire during elective coronary angiography. Patients subsequently underwent stress SPECT thallium-201 testing, and the blinded interpretations were correlated. Coronary flow reserve in a control group with normal coronary arteries classified our sample into group 1 (abnormal flow reserve, < 2.0) and group 2 (normal flow reserve, > or = 2.0). RESULTS: As defined, the coronary flow reserve of 16 vessels in group 1 was diminished in comparison to that of 19 vessels in group 2 (p = 0.0001). Qualitative and quantitative analysis of stress SPECT thallium-201 images confirmed perfusion defects in 15 of 16 vascular territories in group 1 in contrast to 1 of 19 regions in group 2. The sensitivity, specificity and overall predictive accuracy of Doppler-determined coronary flow reserve for stress SPECT thallium-201 results were 94%, 95% and 94%, respectively. CONCLUSIONS: In appropriately selected patients with intermediate coronary artery stenoses, Doppler guide wire determination of lesion significance provides equivalent data to those acquired by stress SPECT thallium-201 imaging.