C. Di Mario

Prognostic value of intracoronary flow velocity and diameter stenosis in assessing the short- and long-term outcomes of coronary balloon angioplasty - The DEBATE study (Doppler Endpoints Balloon Angioplasty Trial Europe)

BACKGROUND The aim of this prospective, multicenter study was the identification of Doppler flow velocity measurements predictive of clinical outcome of patients undergoing single-vessel balloon angioplasty with no previous Q-wave myocardial infarction. METHODS AND RESULTS In 297 patients, a Doppler guidewire was used to measure basal and maximal hyperemic flow velocities proximal and distal to the stenosis before and after angioplasty. In 225 patients with an angiographically successful percutaneous transluminal coronary angioplasty (PTCA), postprocedural distal coronary flow reserve (CFR) and percent diameter stenosis (DS%) were correlated with symptoms and/or ischemia at 1 and 6 months, with the need for target lesion revascularization, and with angiographic restenosis (defined as DS > or = 50% at follow-up). Logistic regression and receiver operator characteristic curve analyses were applied to determine the prognostic cutoff value of CFR and DS separately and in combination. Optimal cutoff criteria for predictors of these clinical events were DS, 35%; CFR, 2.5. A distal CFR after angioplasty > 2.5 with a residual DS < or = 35% identified lesions with a low incidence of recurrence of symptoms at 1 month (10% versus 19%, P=.149) and at 6 months (23% versus 47%, P=.005), a low need for reintervention (16% versus 34%, P=.024), and a low restenosis rate (16% versus 41%, P=.002) compared with patients who did not meet these criteria. CONCLUSIONS Measurements of distal CFR after PTCA, in combination with DS%, have a predictive value, albeit modest for the short- and long-term outcomes after PTCA, and thus may be used to identify patients who will or will not benefit from additional therapy such as stent implantation.

Three-dimensional reconstruction of intracoronary ultrasound images. Rationale, approaches, problems, and directions.

Although intracoronary ultrasonography allows detailed tomographic imaging of the arterial wall, it fails to provide data on the structural architecture and longitudinal extent of arterial disease. This information is essential for decision making during therapeutic interventions. Three-dimensional reconstruction techniques offer visualization of the complex longitudinal architecture of atherosclerotic plaques in composite display. Progress in computer hardware and software technology have shortened the reconstruction process and reduced operator interaction considerably, generating three-dimensional images with delineation of mural anatomy and pathology. The indications for intravascular ultrasonography will grow as the technique offers the unique capability of providing ultrasonic histology of the arterial wall, and the need for a three-dimensional display format for comprehensive analysis is increasingly recognized. Consequently, three-dimensional imaging is being rapidly implemented in the catheterization laboratories for guidance of intracoronary interventions and detailed assessment of their results. However exciting the prospects may be, three-dimensional reconstructions at present remain partially artificial because the true spatial position of the imaging catheter tip is not recorded, and shifts in its location and curves of the arterial lumen result in pseudoreconstructions rather than true reconstructions. In this report, we address the principles of three-dimensional reconstruction with a critical review of its limitations. Potential solutions for refinement of this exciting imaging modality are presented.

Slope of the instantaneous hyperemic diastolic coronary flow velocity-pressure relation. A new index for assessment of the physiological significance of coronary stenosis in humans.

Coronary flow reserve (CFR), the functional index of stenosis severity more frequently used in the catheterization laboratory, is greatly affected by the hemodynamic conditions at the time of measurement and cannot be applied in the immediate assessment of the outcome of coronary interventions. The aim of the present study was to establish the feasibility and reproducibility of the assessment of the slope of the instantaneous diastolic relation between coronary flow velocity and aortic pressure during maximal hyperemia (IHDVPS) using a spectral analysis of the intracoronary Doppler signal, to assess the sensitivity and specificity of this index in the detection of flow-limiting coronary stenoses in comparison with CFR, and to study the possibility of deter-mining the zero-flow pressure from the intercept of the velocity-pressure relation on the pressure axis during a con-trolled cardiac arrest. Methods and ResultsThe instantaneous peak coronary flow velocity measured after intracoronary papaverine with a Doppler guidewire was plotted against the simultaneously measured aortic pressure, and the slope of the velocity-pressure relation in the phase of progressive diastolic velocity decrease was calculated during four consecutive beats. In nine normal arteries, a controlled diastolic cardiac arrest was induced by an intracoronary bolus injection of 3 mg adenosine. The IHDVPS could be assessed in 79 of 95 patients (83%), with a moderate intraobserver variability (0.4±11% after independent selection of different beats during maximal hyperemia). The IHDVPS showed no significant correlation with heart rate, mean diastolic aortic pressure, type of vessel studied, and cross-sectional area at the site of the velocity recording. The IHDVPS was significantly lower in arteries with.30% diameter stenosis than in normal or near-normal arteries (0.71±0.48 versus 1.73±0.80 cm · s−1 · mm Hg−1, P<.0000002). In the stenosis group, both IHDVPS and CFR were significantly correlated with the minimal luminal cross-sectional area (r=.46, P<.05 and r=.62, P<.002, respectively). The study of the velocity-pressure relation during long diastolic pauses showed a curvilinear relation between velocity and pressure in the lower pressure range, with an upward concavity to the velocity axis and no intercept with the pressure axis in most cases. ConclusionsThe IHDVPS can distinguish between arteries with and without coronary stenoses and has a significant inverse correlation with the severity of the stenosis. Under the stable hemodynamic conditions of this study, the IHDVPS and CFR had similar sensitivities and specificities in distinguishing normal and stenotic vessels and demonstrated similar correlation with minimal luminal cross-sectional area. The curvilinearity of the velocity-pressure relation during long diastolic pauses, possibly due to a significant reduction of luminal cross-sectional area at low pressures, complicates the use of the flow velocity-pressure relation for the assessment of the zero-flow pressure.

Prediction of restenosis after coronary balloon angioplasty. Results of PICTURE (Post-IntraCoronary Treatment Ultrasound Result Evaluation), a prospective multicenter intracoronary ultrasound imaging study.

BACKGROUND Intracoronary ultrasound (ICUS) imaging is potentially suitable to identify lesions at high risk of restenosis after percutaneous transluminal coronary angioplasty (PTCA), but it has not been studied systematically. METHODS AND RESULTS We recruited 200 patients in whom ICUS studies were performed after successful PTCA and related their ICUS parameters to 6-month follow-up quantitative coronary angiography. This was performed in 164 patients (82%), yielding 170 lesions for analysis. The overall incidence of a > or = 50% diameter stenosis at follow-up (categorical restenosis) was 29.4%. Quantitative ICUS parameters were weakly but significantly related to follow-up minimal luminal diameter on quantitative coronary angiography (lumen area: R2 = .36, P = .0001; vessel area: R2 = .29, P = .0002; plaque area: R2 = -.18, P = .021; percent obstruction: R2 = -.15, P = .05), but categorical restenosis was not significantly related to these parameters (P = .63, .77, .38, and .08, respectively). There were no significant predictors of restenosis in ICUS parameters of plaque morphology: eccentric versus concentric (P = 1.0), plaque type (hard, soft, or calcific, P = .98), or the number of calcified quadrants (P = .41). There were no significant predictors of restenosis in two predefined types of vessel-wall disruptions: (1) rupture: presence (P = .79), depth (partial versus complete, P = .85), or extent in quadrants (P = .6), and (2) dissection: presence (P = .31), depth (P = .82), or extent (P = .38). CONCLUSIONS Qualitative ICUS parameters after PTCA did not predict restenosis. A larger lumen and vessel area and a smaller plaque area by ICUS were associated with a larger angiographic minimal lumen diameter at follow-up, but these parameters were not significantly related to categorical restenosis.

Semi-automatic contour detection for volumetric quantification of intracoronary ultrasound

Volumetric quantification of the vessel lumen and plaque can be derived from a sequence of cross-sectional intracoronary ultrasound (ICUS) images. A semi-automatic approach has been developed to detect the contours of the lumen and plaque on a three-dimensional ICUS data set. This approach optimizes the contour detection algorithm by combining information from two perpendicular longitudinal views. Preliminary results have shown that this method is able to provide accurate and reproducible measurements of lumen and plaque volumes.<<ETX>>

Dynamic three-dimensional reconstruction of ICUS images based on an EGG-gated pull-back device

At present most systems used for three-dimensional reconstruction (3-D) of two-dimensional intracoronary ultrasound (ICUS) images are based on an image acquisition with a pull-back device which withdraws the catheter with a constant speed, not taking account of cardiac motion and coronary dynamic/pulsation. Cyclic changes of the vessel dimensions and the movement of the catheter inside the vessel result in artifacts and inaccuracies of quantitative measurements. This phenomenon limits accuracy and resolution when an attempt of 3-D reconstruction is performed, since images obtained in different phases of the cardiac cycle are compiled. To overcome these limitations the authors developed a custom-designed pull-back device driven by a stepping motor, which is controlled by a steering logic ensuring an ECG-gated image acquisition.

Histological changes in the aortic valve after balloon dilatation: evidence for a delayed healing process.

OBJECTIVE--To investigate whether balloon dilatation of the aortic valve induces long-term macroscopic or histological changes or both to explain the restenosis process. DESIGN--Prospective study of 39 consecutive patients. Sixteen later (mean (SD) 12 (10) months) required operation. This non-randomised subgroup was compared with 10 patients who had aortic valve replacement without prior dilatation. SETTING--University cardiology and cardiac surgery centre and pathology department. PATIENTS--16 patients who had aortic valve replacement because of failure of or restenosis after balloon dilatation of the aortic valve. Twelve resected valves were examined. INTERVENTIONS--Percutaneous balloon dilatation of the aortic valve (maximal balloon size: trefoil 3 x 12 mm balloon or bifoil 2 x 19 mm balloon) and surgical inspection before excision of the aortic valve leaflets during open-chest aortic valve replacement. Fixation, decalcification, and staining for histology. MAIN OUTCOME MEASURES--Presence of long-term pathological changes in the resected valve and their relation to restenosis after balloon dilatation. RESULTS--Macroscopically the previously dilated valves were indistinguishable from valves from the patients who had valve replacement only. Microscopically, the dilated aortic valves showed areas of young scar tissue that were not seen in a control group of surgically excised stenotic aortic valves. This persistent scarring reaction was seen around small tears or lacerations of the collagenous valve stroma, fractures in calcified areas, and splits in commissures. Young scar tissue without collagenisation was still present 24 months after dilatation. CONCLUSION--Organisation and collagenisation of scar tissue develops slowly after balloon dilatation of the aortic valve. This prolonged scarring reaction may explain the late development of restenosis in some patients.

Procedural and follow up results with a new balloon expandable stent in unselected lesions

Objective To assess the clinical and angiographic results of the first clinical application of a new balloon expandable stent, the NIR stent, characterised by high longitudinal flexibility and low profile before expansion, and by high radial support and minimal recoil and shortening after expansion. Design Single centre survey of unselected lesions in consecutive patients. Setting Tertiary referral centre. Patients and lesions 93 stents of various length (9, 16, and 32 mm) were implanted in 64 lesions in 41 patients. Twenty lesions (31%) were longer than 15 mm, and 17 lesions (27%) were located in vessels with a diameter smaller than 2.5 mm. Extreme tortuosity of the proximal vessel was present in 15 lesions (23%). All patients were treated with aspirin and ticlopidine. All lesions were evaluated before and after treatment by quantitative angiography, and in 47 lesions (75%) the stent expansion was also controlled by intracoronary ultrasound. Clinical follow up was available in all patients and angiographic follow up was performed in 53 lesions (84%), at a mean (SD) interval of 5.4 (1.7) months. Results Deployment of the stent failed in two lesions (3%). Minimum lumen diameter increased from 1.01 (0.54) mm to 2.94 (0.49) mm, and diameter stenosis decreased from 66(15)% to 7(11)%. There was one in-hospital non-Q wave myocardial infarction, one sudden death after 40 days, and 17 target lesion revascularisations (27%). Angiographic restenosis (⩾ 50% diameter stenosis) was documented in 19 lesions (36% of all lesions with angiographic follow up), with an average residual diameter stenosis of 43(21)% and minimum lumen diameter of 1.63 (0.74) mm. Restenosis was more common in vessels with a reference diameter < 2.5 mm (45%) and for lesions longer than 15 mm (46%). Conclusions The NIR stent could be used successfully in most lesions, achieving optimal angiographic results with very few in-hospital or subacute cardiac events. The angiographic restenosis rate and need for target lesion revascularisation remained high in this unfavourable lesion subset, especially in small vessels and long lesions.

Quantitative assessment of coronary artery stenosis by intravascular Doppler catheter technique.

does not provide much information. Provided that heart rhythm entropy equals HRV, the authors obtained some results that apparently are similar to some of those in our recent study in Circulation.2 Our article describes many other aspects than those stressed by Dr. Zbilut. Among other things, we demonstrated that HRV is significantly related to infarct size and left ventricular function, is increased after thrombolysis, is significantly related to mortality, and increases progressively over 3 months. A significant aspect of our work was the use of an index of HRV that had already been clinically validated.3 None of these points is readily apparent from the work of Khalfen and Temkin. Concerning the second article cited by Dr. Zbilut, which deals with patients having significant cardiac events,4 we would like to stress several points. The authors used very short strips of data (12 seconds of ECG), different recorders, manual calculations of the RR data on strips recorded at 25 mm/sec, a single observer, and a single measurement. Based on this study, it does not seem possible to derive that acute myocardial infarction (AMI) patients had lower HRV than non-AMI patients, because AMI patients were not considered as a distinct group. Patients were enrolled without differentiation between AMI patients and patients having lifethreatening arrhythmias. Gian Carlo Casolo, MD, PhD Piero Stroder, MD Claudia Signorini, MD Francesca Calzolari, MD Enrico Balli, MD Mauro Zucchini, MD Antonio Sulla, MD Stefano Lazzerini, MD University of Florence and Ospedale San Giovanni di Dio Florence, Italy

New concepts for interpretation of intracoronary velocity and pressure tracings.

The development of quantitative angiography and the introduction of new imaging techniques cannot replace functional methods of assessing the severity of stenosis. Measurement of transstenotic pressure gradient and poststenotic flow velocity using miniaturised sensors with guidewire technology offers an alternative to the conventional non-invasive methods that is immediately applicable in the catheterisation laboratory during interventional procedures. The complexity of the coronary circulation, however, makes it difficult to establish simple cut-off criteria to identify the presence of a flow-limiting stenosis. For intermediate lesions or in the presence of variable haemodynamic conditions, the accuracy of the assessment can be improved by the application of more complex indices proposed and validated in the laboratory animals. Two of these indices are myocardial fractional flow reserve and the slope of the instantaneous relation between pressure or pressure gradient and flow velocity.