Functional Assessment Of Coronary Stenosis Research Articles

Evaluation of intermediate coronary stenosis with intravascular ultrasound and fractional flow reserve: Its use and abuse

Clinical decision making in patients with intermediate coronary stenosis is still debated. Intravascular ultrasound (IVUS) examination and/or functional assessment of coronary stenosis by fractional flow reserve (FFR) are currently used to define the severity of such lesions. There are very few studies with a small sample size that have a head-to-head comparison between IVUS and FFR in the evaluation of angiographically de novo intermediate lesions. There are no randomized, controlled trials to demonstrate the superiority of IVUS versus FFR in providing improved clinical outcomes in comparison with angiography alone. However, the issue of superiority might be irrelevant, because IVUS and FFR could be complementary techniques to be used in the catheterization laboratory to provide critical anatomic and functional data that permit more accurate decisions in the management of the patient.

Long-Term Prognosis in Diabetic Patients in Whom Revascularization Is Deferred Following Fractional Flow Reserve Assessment

The fractional flow reserve (FFR) has been shown to be a valid and useful measure in the functional assessment of coronary stenoses of intermediate severity. Our aim was to determine the usefulness of FFR assessment in diabetic patients, in whom determination of the FFR can be influenced by microvascular dysfunction. Between 1997-2004, FFR assessment was used to evaluate 222 consecutive coronary lesions judged by an interventional cardiologist to be of intermediate severity (ie, 40%-70%). Intravenous adenosine (140 microg/kg per min) was used to achieve maximum hyperemia. The occurrence of cardiac events (ie, death, non-fatal acute myocardial infarction, and target lesion revascularization) was compared in diabetics and nondiabetics in whom FFR assessment gave a negative result and intervention was deferred. The mean follow-up period was 30+/-21 months. Revascularization was deferred for 144 lesions (in 136 patients) in which the FFR was >/=0.75. Of these, 42 lesions (29.2%) were in diabetics (40 patients). The proportion of patients who were female or who had hypertension, dyslipidemia or multivessel disease was greater in the diabetic group. There was no difference in indications for coronary angiography. In both groups, the most frequently investigated vessel was the left anterior descending coronary artery. The mean FFR was 0.87+/-0.06, and there was no difference between the groups. On long-term follow-up, there was no difference in the rate of death or acute myocardial infarction. Overall, 8.8% of nondiabetics and 14.3% of diabetics with a negative FFR test result required target lesion revascularization (P=.32). Our results indicate that deferring percutaneous coronary intervention in diabetics with a moderately severe coronary artery stenosis and an FFR >/=0.75 is safe.

214 Can stress echocardiography with tissue characterization evaluate non-critical coronary stenosis? A validation study against simultaneous measurement of fractional flow reserve

Background: Fractional flow reserve (FFR) is accepted as gold standard for the functional assessment of coronary stenosis. The typical marker of acute myocardial ischemia by tissue Doppler echocardiography with strain rate imaging (TDE/SRI) is postsystolic shortening (PSS). The study evaluated different echocardiographic modalities for detection of myocardial ischemia due to non-critical coronary stenosis. Material and methods: We investigated 22 consecutive patients presenting with stable angina, negative exercise tests and coronary 1-vessel disease with 50-75% diameter stenosis. TDE/SRI was performed at baseline and at peak hyperemia during 0.14 mg/kg/min adenosine infusion simultaneously with intracoronary FFR measurements. Angioplasty was carried out if FFR 0.3, with reduced Ss <15%. Results: Pathologic FFR <0.75 was found in 11 patients, who underwent angioplasty. Myocardial contractility reflected by SRs increased during hyperemia only in the patient group with FFR ≥0.75 and decreased markedly during balloon inflation, but its variation was not robust enough to predict pathologic FFR (Fig. 1). PSS was identified in 10 of 11 patients during vessel occlusion, but had a low sensitivity (2 of 11 patients with FFR <0.75) for the more subtle changes during hyperemia. Conclusion: Although TDE/SRI enhances the diagnostic accuracy of adenosine stress echocardiography, it still cannot serve as a reliable noninvasive alternative to FFR for the functional assessment of moderate-to-severe coronary stenosis.

Assessment of ambiguous coronary lesions by intravascular ultrasound.

Until recently, coronary angiography has been regarded as the 'gold standard' for visualizing and quantifying coronary artery disease. Coronary angiography, however, is a luminographic technique revealing only the inner lumen of the coronary artery. In contrast, intravascular ultrasound investigations yield a detailed morphological description of the vessel wall and plaque characteristics. Based on these analyses, new insights into the pathogenesis of atherosclerotic coronary disease have evolved, including the remodeling phenomena. Thus, nowadays intravascular ultrasound can be regarded as the new 'gold standard' for the morphological assessment of lesion severity during cardiac catheterizations. Likewise, intracoronary Doppler and intracoronary pressure measurements have demonstrated their superiority in the functional assessment of coronary stenoses. Intravascular ultrasound investigations can be performed with high success and low complication rates. The present manuscript concentrates on the value of IVUS for the assessment of ambiguous lesions. Several forms of ambiguous lesions based on the angiographic appearance, i.e. intermediate lesion with undetermined stenosis severity, aneurysmatic widening of the coronary segment, ostial lesions, branching vessels, vessel tortuosity, main stem lesions, focal spasm, sites of plaque rupture, dissections, unclear haziness and contrast density changes are discussed and illustrated by respective angiographic and IVUS examples. Both the advantages and the limitations of angiographic and intravascular ultrasound examination are discussed in detail. In conclusion, additional intravascular ultrasound examination helps to diagnose accurately the underlying atherosclerotic disease, to define lesion characteristics and to optimize individual patient care and cost with respect to diagnostic catheterizations and coronary interventions.

Intracoronary dobutamine echocardiography: An innovative approach for the functional assessment of coronary stenoses: Jeffrey S. Cohen MD, Alice K. Jacobs MD, Deanna Mahoney, Ravin Davidoff MD, Boston University Medical Center, Boston, MA

Intracoronary dobutamine echocardiography: An innovative approach for the functional assessment of coronary stenoses: Jeffrey S. Cohen MD, Alice K. Jacobs MD, Deanna Mahoney, Ravin Davidoff MD, Boston University Medical Center, Boston, MA

Transstenotic coronary pressure gradient measurement in humans: In vitro and in vivo evaluation of a new pressure monitoring angioplasty guide wire

Objectives. The present study was designed to investigate 1) the feasibility and accuracy of coronary pressure measurements with a novel 0.015-in. (0.038 cm) fluid-filled guide wire, and 2) the effect of the guide wire itself on stenosis hemodynamics.Background. To assess the functional results of coronary angioplasty, measurements of the transstenotic pressure gradient have been advocated. However, this is no longer routinely measured because it is not reliable when determined with the angioplasty catheter.Methods. A fluid-filled 0.015-in. guide wire to be connected to a conventional pressure transducer was developed. Five wires were tested for their frequency response characteristics and for their accuracy in measuring hydrostatic pressure. In an in vitro model of stenosis (reference diameter 4 mm), the pressure gradient was determined at incremental flow levels for varying stenosis severity with and without a 0.015-in. guide wire through the narrowing. In 37 patients, the transstenotic pressure gradient was measured before and after angioplasty and compared with obstruction area and percent area stenosis as determined by quantitative coronary angiography.Results. The correlation between the actual pressure and the pressure recorded by the guide wire was excellent (r = 0.98) despite a slight underestimation (−3 ± 5%). Phasic pressure recordings were precluded by a long time constant of 16 ± 4 s. The presence of the guide wire produced a significant overestimation (>20%) of the pressure decrease only in cases of tight stenosis (>90% area reduction). Furthermore, a theoretic model based on the fluid dynamic equation predicted that this overestimation was inversely proportional to the reference diameter of the vessel, yet was only slightly influenced by the flow. The lesion was crossed in all but one (97%) and pressure gradient was recorded throughout the study in 34 (94%) of 36 patients. The mean pressure gradient decreased from 30 ± 19 before to 3 ± 5 mm Hg after angioplasty (p < 0.01). A curvilinear relation was found between the pressure gradient and both percent area stenosis (r2= 0.67) and obstruction area (r2= 0.72). A sharp increase in pressure gradient was noted once the stenosis exceeded 75% area reduction.Conclusions. Mean transstenotic pressure gradients can be easily and reliably recorded with a 0.015-in. fluid-filled guide wire. This ability should facilitate the functional assessment of coronary stenoses of intermediate severity and of immediate postangioplasty results.

Clinical applications of Doppler coronary flow reserve measurements

The development of a subselective coronary Doppler catheter coupled with pharmacologic coronary resistance vessel vasodilation has enabled clinicians to assess coronary vasodilator reserve in humans. This technique has proven useful in the clinical management of patients with a variety of cardiologic problems. This review describes usefulness of Doppler measurements of coronary flow reserve for (1) functional assessment of coronary stenoses of intermediate severity; (2) determination of the need for lesion-specific interventional therapy; (3) assessment of the severity of saphenous vein bypass graft and graft-native vessel anastomotic lesions; (4) assessment of the coronary microcirculation.