Outcomes in patients with aortic stenosis and severely reduced ejection fraction following surgical aortic valve replacement and transcatheter aortic valve replacement.

BACKGROUND: Patients with severe aortic stenosis (AS) and left ventricular (LV) dysfunction demonstrate improvement in left ventricular injection fraction (LVEF) after aortic valve replacement (AVR). The timing and magnitude of recovery in patients with very low LVEF (≤ 25%) in surgical or transcatheter AVR is not well studied. OBJECTIVE: Determine clinical outcomes following transcatheter aortic valve replacement (TAVR) and surgical aortic valve repair (SAVR) in the subset of patients with severely reduced EF ≤ 25%. METHODS: Single-center, retrospective study with primary endpoint of LVEF 1-week following either procedure. Secondary outcomes included 30-day mortality and delayed postprocedural LVEF. T-test was used to compare variables and linear regression was used to adjust differences among baseline variables. RESULTS: 83 patients were enrolled (TAVR = 56 and SAVR = 27). TAVR patients were older at the time of procedure (TAVR 77.29 ± 8.69 vs. SAVR 65.41 ± 10.05, p < 0.001). One week post procedure, all patients had improved LVEF after both procedures (p < 0.001). There was no significant difference in LVEF between either group (TAVR 33.5 ± 11.77 vs. SAVR 35.3 ± 13.57, p = 0.60). Average LVEF continued to rise and increased by 101% at final follow-up (41.26 ± 13.70). 30-day mortality rates in SAVR and TAVR were similar (7.4% vs. 7.1%, p = 0.91). CONCLUSION: Patients with severe AS and LVEF ≤ 25% have a significant recovery in post-procedural EF following AVR regardless of method. LVEF doubled at two years post-procedure. There was no significant difference in 30-day mortality or mean EF recovery between TAVR and SAVR. TRIAL REGISTRATION: Indiana University institutional review board granted approval for above study numbered 15,322.

Heparin Dosing During Percutaneous Coronary Intervention and Obesity.

ABSTRACT: Unfractionated heparin is the most common anticoagulant used during percutaneous coronary intervention. Practice guidelines recommend an initial weight-based heparin bolus dose between 70 and 100 U/kg to achieve target activated clotting time (ACT) of 250-300 seconds. The impact of severe obesity on weight-based heparin dosing is not well studied. We performed a retrospective analysis of 424 patients undergoing percutaneous coronary intervention who received heparin for anticoagulation. We collected detailed data on cumulative heparin administration and measured ACT values in this cohort. We performed separate analyses to identify clinical predictors that may affect dose-response curves. There was significant variability in dosing with mean dose of 103.9 ± 32-U/kg heparin administered to achieve target ACT ≥ 250 seconds. Women received higher initial heparin doses when adjusted for weight than men (97.6 ± 31 vs. 89 ± 28 U/kg, P = 0.004), and only 49% of patients achieved ACT ≥ 250 s with the initial recommended heparin bolus dose (70-100 U/kg). Lower heparin dose (U/kg) was required in obese patients to achieve target ACT. In multivariate linear regression analysis with ACT as dependent variable, after inclusion of weight-based dosing for heparin, body mass index was the only significant covariate. In conclusion, there is significant variability in the therapeutic effect of heparin, with a lower weight-adjusted heparin dose required in obese patients.

Fulminant myocarditis: COVID or not COVID? Reinfection or co-infection?

We describe a unique case of fulminant myocarditis in a patient with presumed SARS-CoV-2 reinfection. Patient had initial infection 4 months backand had COVID-19 antibody at the time of presentation. Endomyocardial biopsy showed lymphocytic myocarditis, that is usually seen in viral myocarditis. The molecular diagnostic testing of the endomyocardial biopsy for cardiotropic viruses was positive for Parvovirus and negative for SARS-CoV-2. Authors highly suspect co-infection of SARS-CoV-2 and Parvovirus, that possibly triggered the immune cascade resulting in fulminant myocarditis. Patient was hemodynamically unstable with ventricular tachycardia and was supported on VA ECMO and Impella CP. There was impressive recovery of left ventricular function within 48 h, leading to decannulation of VA ECMO in 72 h. This unique case was written by the survivor herself.

Prediction of Ischemic Events after Percutaneous Coronary Intervention: Thrombelastography Profiles and Factor XIIIa Activity.

BACKGROUND: High plasma fibrin clot strength (MA) measured by thrombelastography (TEG) is associated with increased risk of cardiac events after percutaneous coronary interventions (PCIs). Factor XIIIa (FXIIIa) cross-links soluble fibrin, shortens clot formation time (TEG-K), and increases final clot strength (MA). METHODS: We analyzed platelet-poor plasma from patients with previous PCI. Kaolin-activated TEG (R, K, MA) in citrate platelet-poor plasma and FXIIIa were measured (n = 257). Combined primary endpoint was defined as recurrent myocardial infarction (MI) or cardiovascular death (CVD). Relationship of FXIIIa and TEG measurements on cardiac risk was explored. RESULTS: FXIIIa correlated with TEG-MA (p = 0.002) and inversely with TEG-K (p < 0.001). High MA (≥35.35 mm; p = 0.001), low K (<1.15 min; p = 0.038), and elevated FXIIIa (≥83.51%; p = 0.011) were associated with increased risk of CVD or MI. Inclusion of FXIIIa activity and low TEG-K in risk scores did not improve risk prediction as compared with high TEG-MA alone. CONCLUSION: FXIIIa is associated with higher plasma TEG-MA and low TEG-K. High FXIIIa activity is associated with a modest increase in cardiovascular risk after PCI, but is less sensitive and specific than TEG-MA. Addition of FXIIIa does not provide additional risk stratification beyond risk associated with high fibrin clot strength phenotype measured by TEG.

Simultaneous administration of high-dose atorvastatin and clopidogrel does not interfere with platelet inhibition during percutaneous coronary intervention.

BACKGROUND: Reloading with high-dose atorvastatin shortly before percutaneous coronary interventions (PCIs) has been proposed as a strategy to reduce periprocedural myonecrosis. There has been a concern that statins that are metabolized by cytochrome P450 3A4 may interfere with clopidogrel metabolism at high doses. The impact of simultaneous administration of high doses of atorvastatin and clopidogrel on the efficacy of platelet inhibition has not been established. METHODS: Subjects (n=60) were randomized to receive atorvastatin 80 mg together with clopidogrel 600 mg loading dose (n=28) versus clopidogrel 600 mg alone (n=32) at the time of PCI. Platelet aggregation was measured at baseline, 4 hours after clopidogrel loading dose, and 16-24 hours after clopidogrel loading dose by light transmittance aggregometry using adenosine diphosphate as agonist. RESULTS: Platelet aggregation was similar at baseline in both the atorvastatin and the control groups (adenosine diphosphate 10 µM: 57%±19% vs 61%±21%; P=0.52). There was no significant difference in platelet aggregation between the atorvastatin and the control groups at 4 hours (37%±18% vs 39%±21%; P=0.72) and 16-24 hours post-clopidogrel loading dose (35%±17% vs 37%±18%; P=0.75). No significant difference in incidence of periprocedural myonecrosis was observed between the atorvastatin and control groups (odds ratio: 1.02; 95% confidence interval 0.37-2.8). CONCLUSION: High-dose atorvastatin given simultaneously with clopidogrel loading dose at the time of PCI does not significantly alter platelet inhibition by clopidogrel. Statin reloading with high doses of atorvastatin at the time of PCI appears to be safe without adverse effects on platelet inhibition by clopidogrel (ClinicalTrials.gov: NCT00979940).

Two-in-one aortic valve sizing and valvuloplasty conductance balloon catheter.

BACKGROUND: Inaccurate aortic valve sizing and selection is linked to paravalvular leakage in transcatheter aortic valve replacement (TAVR). Here, a novel sizing valvuloplasty conductance balloon (SVCB) catheter is shown to be accurate, reproducible, unbiased, and provides real-time tool for aortic valve sizing that fits within the standard valvuloplasty procedure. METHODS AND RESULTS: The SVCB catheter is a valvuloplasty device that uses real-time electrical conductance measurements based on Ohm's Law to size the balloon opposed against the aortic valve at any given inflation pressure. Accuracy and repeatability of the SVCB catheter was performed on the bench in phantoms of known dimension and ex vivo in three domestic swine aortic annuli with comparison to computed tomography (CT) and dilator measurements. Procedural workflow and safety was demonstrated in vivo in three additional domestic swine. SVCB catheter measurements had negligible bias or error for bench accuracy considered as the gold standard (Bias: -0.11 ± 0.26 mm; Error: 1.2%), but greater disagreement in ex vivo versus dilators (Bias: -0.3 ± 1.1 mm; Error: 4.5%), and ex vivo versus CT (Bias: -1.0 ± 1.6 mm; Error: 8.7%). The dilator versus CT accuracy showed similar agreement (Bias: -0.9 ± 1.5 mm; Error: 7.3%). Repeatability was excellent on the bench (Bias: 0.02 ± 0.12 mm; Error: 0.5%) and ex vivo (Bias: -0.4 ± 0.9 mm; Error: 4.6%). In animal studies, the device fit well within the procedural workflow with no adverse events or complications. CONCLUSIONS: Due to the clinical relevance of this accurate, repeatable, unbiased, and real-time sizing measurement, the SVCB catheter may provide a useful tool prior to TAVR. These findings merit a future human study.

Factor XIII Val34Leu polymorphism and recurrent myocardial infarction in patients with coronary artery disease.

Factor XIII (FXIII) is necessary for cross linking of fibrin strands and generation of stable fibrin clot. FXIII Val34Leu is a common genetic single nucleotide polymorphism that has been associated with accelerated fibrin stabilization and reduced rate of fibrinolysis. The contribution of Val34Leu to long term risk of recurrent myocardial infarction (MI) in patients with coronary stenting has not been conclusively established. The objective of the study was to examine the effects of Val34Leu on fibrin generation, platelet aggregation, and long term clinical outcomes in patients with coronary artery disease treated with dual antiplatelet therapy. Patients with angiographically documented coronary artery disease who were treated with aspirin and clopidogrel were enrolled (n = 211). Light transmittance aggregometry and plasma fibrin clot formation using thrombelastography (TEG) were determined. Genotyping of Val34Leu was performed using Taqman assay. Clinical events during follow up were recorded. Homozygous carriers of 34 Leu variant had significantly shorter fibrin clot formation time as compared to wild type individuals (TEG K: 1.27 ± 0.3 vs. 1.68 ± 1.1 min, p = 0.011). The Val34Leu variant was associated with gene dose dependent increased risk of MI (log rank, p = 0.002) or occurrence of composite of MI and CV death (log rank, p = 0.005) with highest event rates observed in homozygous carriers of 34 Leu. In summary, FXIII Val34Leu polymorphism was associated with increased rate of fibrin stabilization in homozygous carriers of the variant and may increase risk of recurrent MI and death in patients with angiographically established coronary artery disease treated with dual antiplatelet therapy.

A lumen sizing workhorse guidewire for peripheral vasculature: two functions in one device.

OBJECTIVES: Ideally, guidewires used during peripheral vasculature (PV) interventions could serve both as a therapy delivery platform and a diagnostic tool for real-time vessel sizing (2-in-1 function). BACKGROUND: Vascular imaging modalities, like intravascular ultrasound (IVUS), used during lower PV interventions, can improve outcomes versus angiographic assessment alone, but are rarely used due to added time, cost, and required clinical training/interpretation. METHODS: A 0.035″ bodied 0.035″ conductance guidewire (CGW) is described here as a vascular navigation and diagnostic real-time PV sizing tool. When attached to a console, the CGW creates a safe, electric field to determine vascular size through simultaneous voltage measurements. RESULTS: The CGW showed functionality as a workhorse guidewire on the bench (torqueability and trackability equivalent to a Wholey guidewire) and in vivo (over-the-wire stent deployment in domestic swine and first-in-man study with no major adverse events). Validation of CGW sizing versus the true diameter and IVUS was completed in 4-10 mm diameter phantoms on the bench and in swine and showed virtually no bias with excellent repeatability and accuracy (i.e., CGW repeatability: swine phantom bias = 0.03 ± 0.09 mm (1.3% error). CGW vs. true diameter: in vivo bias = 0.14 ± 0.15 mm (2.7% error). IVUS vs. true diameter: swine phantom bias = 0.01 ± 0.36 mm (4.7% error). CCW vs. IVUS: swine phantom bias = 0.13 ± 0.26 mm (3.8% error)). CONCLUSIONS: Real-time, accurate, and safe PV dimension assessment and therapy-delivery (2-in-1 function) is possible using a novel workhorse 0.035″ bodied CGW.

Conductance sizing balloon for measurement of peripheral artery minimal stent area.

BACKGROUND: Because stent underdeployment occurs frequently, accurate minimal stent area (MSA) measurement during postdilatation is necessary. This study investigated the accuracy and repeatability for MSA determination using a novel conductance balloon (CB) catheter for peripheral vessels. METHODS: The CB catheter is a standard balloon catheter that measures electrical conductance (ratio of current/voltage drop) in real-time during inflation, which directly relates to the balloon cross-sectional area through Ohm's law. CB measurements were made in 4- to 10-mm phantoms on the bench, ex vivo in stents fully deployed in diseased human peripheral arteries, and in vivo in stents fully deployed in peripheral vessels in six swine. CB measurement accuracy and repeatability were calculated and compared with the known dimension (bench phantoms) or with intravascular ultrasound (IVUS) measurement after stent deployment (ex vivo and in vivo). RESULTS: CB measurements were highly accurate (error: 1.8% bench, 5% ex vivo, and 5% in vivo) and repeatable (error: 0.9% bench, 1.8% ex vivo, and 1.3% in vivo), with virtually no bias (average difference in measurements: -0.05 mm bench CB vs known phantom diameters, -0.06 mm ex vivo CB vs IVUS, and -0.11 mm in vivo CB vs IVUS). CONCLUSIONS: The CB sizing capability can be integrated within a standard balloon catheter (two-in-one function) to provide accurate, real-time assessment of MSA to ensure full stent apposition rather than the use of pressure as a surrogate for size.

C-reactive protein and fibrin clot strength measured by thrombelastography after coronary stenting.

Inflammation is implicated in the progression of coronary artery disease and the molecular processes of inflammation and thrombosis are closely intertwined. Elevated levels of C-reactive protein (CRP) have been associated with an elevated risk of adverse ischaemic events after coronary stenting and hypercoagulability. Heightened whole blood clot strength measured by thrombelastography (TEG) has been associated with adverse ischaemic events after stenting. We intended to examine the relationship of CRP to plasma fibrin clot strength in patients after coronary stenting. Plasma fibrin clot strength was measured by TEG in 54 patients 16-24 h after undergoing elective percutaneous coronary intervention (PCI). Coagulation was induced in citrated plasma by addition of kaolin and CaCl2. Plasma levels of CRP and fibrinogen were measured by enzyme-linked immunoassay. Increasing quartiles of CRP were associated with increasing levels of maximal plasma fibrin clot strength measured by TEG (P < 0.001) and increasing BMI (P = 0.04). Patients in the highest quartile of CRP had significantly higher maximal fibrin clot strength (G) than the patients in the lowest quartile (G: 3438 ±â€Š623 vs. 2184 ±â€Š576 dyn/cm, P < 0.0001). Fibrinogen concentration was not significantly different across quartiles of CRP (P = 0.97). Patients with established coronary artery disease undergoing coronary stenting who have elevated CRP after PCI exhibit heightened maximal plasma fibrin clot strength as compared with those with low CRP. Thrombotic risk associated with elevated CRP may be linked to procoagulant changes and high tensile fibrin clot strength independent of fibrinogen concentration.

Protease activated receptor-1 (PAR-1) mediated platelet aggregation is dependent on clopidogrel response.

INTRODUCTION: Clopidogrel inhibits ADP mediated platelet aggregation through inhibition of the P2Y12 receptor by its active metabolite. Thrombin induces platelet aggregation by binding to protease activated receptor-1 (PAR-1), and inhibition of PAR-1 has been evaluated in patients treated with clopidogrel to reduce ischemic events after acute coronary syndromes. Residual PAR-1 mediated platelet aggregation may be dependent on extent of clopidogrel response. MATERIAL AND METHODS: Platelet aggregation was measured in 55 patients undergoing elective PCI at 16-24 hours after 600 mg clopidogrel loading dose by light transmittance aggregometry using ADP 20 µM and thrombin receptor agonist peptide (TRAP) at 15 µM and 25 µM as agonists. Genomic DNA was genotyped for common CYP2C19 variants. RESULTS: Increasing quartiles of 20 µM ADP induced platelet aggregation after clopidogrel loading were associated with increasing levels of TRAP mediated platelet aggregation. Patients in the highest quartile (clopidogrel non-responders) of post treatment ADP aggregation had significantly higher TRAP mediated aggregation than the patients in the lowest quartile (clopidogrel responders) [TRAP 15 µM: 79.6 ± 5% vs. 69.5 ± 8%, p<0.001]. CONCLUSIONS: Non-responders to clopidogrel show increased residual platelet aggregation induced by TRAP, whereas clopidogrel responders exhibit attenuated response to TRAP. Addition of PAR-1 antiplatelet drugs may be most effective in patients with reduced clopidogrel response and high residual TRAP mediated platelet aggregation.

Mis-sizing of stent promotes intimal hyperplasia: impact of endothelial shear and intramural stress.

Stent can cause flow disturbances on the endothelium and compliance mismatch and increased stress on the vessel wall. These effects can cause low wall shear stress (WSS), high wall shear stress gradient (WSSG), oscillatory shear index (OSI), and circumferential wall stress (CWS), which may promote neointimal hyperplasia (IH). The hypothesis is that stent-induced abnormal fluid and solid mechanics contribute to IH. To vary the range of WSS, WSSG, OSI, and CWS, we intentionally mismatched the size of stents to that of the vessel lumen. Stents were implanted in coronary arteries of 10 swine. Intravascular ultrasound (IVUS) was used to size the coronary arteries and stents. After 4 wk of stent implantation, IVUS was performed again to determine the extent of IH. In conjunction, computational models of actual stents, the artery, and non-Newtonian blood were created in a computer simulation to yield the distribution of WSS, WSSG, OSI, and CWS in the stented vessel wall. An inverse relation (R(2) = 0.59, P < 0.005) between WSS and IH was found based on a linear regression analysis. Linear relations between WSSG, OSI, and IH were observed (R(2) = 0.48 and 0.50, respectively, P < 0.005). A linear relation (R(2) = 0.58, P < 0.005) between CWS and IH was also found. More statistically significant linear relations between the ratio of CWS to WSS (CWS/WSS), the products CWS × WSSG and CWS × OSI, and IH were observed (R(2) = 0.67, 0.54, and 0.56, respectively, P < 0.005), suggesting that both fluid and solid mechanics influence the extent of IH. Stents create endothelial flow disturbances and intramural wall stress concentrations, which correlate with the extent of IH formation, and these effects were exaggerated with mismatch of stent/vessel size. These findings reveal the importance of reliable vessel and stent sizing to improve the mechanics on the vessel wall and minimize IH.

Selective autoretroperfusion preserves myocardial function during coronary artery ligation in swine.

BACKGROUND: External pumps have been previously used to minimize edema and hemorrhage caused by coronary retroperfusion. The objective of this study was to use a pump-less approach (selective autoretroperfusion, SARP) to preserve myocardial function after acute coronary artery ligation. METHODS: In five experimental pigs, the LAD artery was ligated distal to the first diagonal and retroperfusion was instituted for three hours from a brachiocephalic artery at 50 mmHg pressure through an adjustable occluder on the cannula. In eight control pigs, the LAD artery was ligated distal to the second diagonal for the same duration with no SARP. RESULTS: ECG showed more prominent S-T segment elevation in the untreated control group despite the more distal ligation. The degree of myocardial contraction was significantly attenuated in the control group but was largely preserved in the SARP treated group. The myocytes were well preserved in the SARP group with no rupture of venous microvessels. Myocyte edema and disruption was observed in the control group with only mild extracellular edema in the SARP treated group. CONCLUSION: SARP preserved myocardial function with no damage to the myocyte and venules during three hours of acute LAD ligation.

A nonimaging catheter for measurement of coronary artery lumen area: a first in man pilot study.

OBJECTIVES: The objective of this human pilot study was to determine the safety and the level of agreement between a novel nonimaging 2.7 Fr. catheter-based system (LumenRECON, LR) that uses electrical conductance for measurement of lumen cross-sectional area (CSA) with intravascular ultrasound (IVUS) and quantitative coronary angiography (QCA). Based on previous animal studies, we hypothesized the level of agreement between LR and IVUS to be 13%. BACKGROUND: Accurate and reproducible vessel sizing is essential for optimal percutaneous coronary intervention (PCI). METHODS: A total of 12 patients were studied to evaluate the safety, accuracy, and reproducibility of the system in comparison with IVUS and QCA. The CSA of coronary arteries was determined by IVUS, QCA, and LR in the distal, proximal, and center of a lesion during standard PCI. RESULTS: A Bland-Altman plot of the LR versus IVUS and QCA show a nonsignificant mean difference between the two measurements of 0.04 and 0.07 mm in diameter, respectively. The root mean square error of LR versus IVUS and QCA was 14.3 and 25.8% of the mean IVUS or QCA diameter, respectively. The mean of the difference between two LR duplicate measurements was nearly zero (0.03 mm) and the repeatability coefficient was within 8.7% of the mean of the two measurements. There were no procedural complications nor were any device-related MACE reported within 30 days of the procedure. CONCLUSIONS: This proof of concept pilot study establishes the safety and accuracy of the conductance technology for a pivotal trial of coronary sizing.

Usefulness of fragmented QRS on a 12-lead electrocardiogram in acute coronary syndrome for predicting mortality.

Electrocardiographic signs of a non-ST elevation myocardial infarction (NSTEMI) are nonspecific, and therefore the diagnosis of NSTEMI during acute coronary syndromes (ACS) depends mainly on cardiac biomarker levels. Fragmented QRS (fQRS) represents myocardial conduction abnormalities due to myocardial infarction (MI) scars in patients with coronary artery disease. However, the time of appearance of fQRS during ACS has not been investigated. It was postulated that in patients with ACS, fQRS on 12-lead electrocardiography occurs within 48 hours of presentation with NSTEMI as well as ST elevation MI and that fQRS predicts mortality. Serial electrocardiograms from 896 patients with ACS (mean age 62 +/- 11 years, 98% men) who underwent cardiac catheterization were studied. Four hundred forty-one patients had MIs, including 337 patients with NSTEMIs, and 455 patients had unstable angina (the control group). Serial electrocardiograms were obtained every 6 to 8 hours during the first 24 hours after the diagnosis of MI and the next day (<48 hours). Fragmented QRS on 12-lead electrocardiography was defined by the presence of single or multiple notches in the R or S wave, without a typical bundle branch block, in > or =2 contiguous leads in 1 of the major coronary artery territories. Fragmented QRS developed in 224 patients (51%) in the MI group and only 17 (3.7%) in the control group (p <0.001). New Q waves developed in 122 (28%), 76 (23%), and 2 (0.4%) patients in the MI, NSTEMI, and control groups, respectively. The sensitivity values of fQRS for ST elevation MI and NSTEMI were 55% and 50%, respectively. The specificity of fQRS was 96%. Kaplan-Meier survival analysis revealed that patients with fQRS had significantly decreased times to death compared to those without fQRS. Fragmented QRS, T-wave inversion, and ST depression were independent predictors of mortality during a mean follow-up period of 34 +/- 16 months. In conclusion, fQRS on 12-lead electrocardiography is a moderately sensitive but highly specific sign for ST elevation MI and NSTEMI. Fragmented QRS is an independent predictor of mortality in patients with ACS.

A novel system for the reconstruction of a coronary artery lumen profile in real time: a preclinical validation.

Accurate sizing of vessel diameter is important for understanding the physiology of blood vessels as well as the treatment of coronary and peripheral artery disease. The objective of this study was to validate a novel catheter-based system [the LumenRECON (LR) system] for the real-time reconstruction of lumen cross-sectional area (CSA) along the length of a vessel segment. A total of 22 swine (20 Yorkshire and 2 atherosclerotic Ossabaw swine) were used to evaluate the accuracy, reproducibility, and safety of the system compared with intravascular ultrasound (IVUS). The CSA of the right coronary artery, left anterior descending coronary artery, and left circumflex artery were determined by IVUS and the LR system over a 3- to 4-cm segment in 12 Yorkshire and 2 atherosclerotic Ossabaw swine and 2 postmortem atherosclerotic human hearts. In eight chronic animals, the effect of the LR catheter on the vessel wall was evaluated at 1 day and 2 wk (4 animals each) after the intervention. A Bland-Altman plot of the LR and IVUS data showed a mean difference between the two measurements of 0.055 mm in diameter, which was not statistically significant from zero, indicating a lack of bias in the comparison of the LR system with IVUS. The root mean square error of the two measurements was 10.2% of the mean IVUS diameter. The repeatability of the LR system was assessed using duplicate measurements. The mean of the difference between the two measurements was nearly zero, and the repeatability coefficient was within 4.5% of the mean of the two measurements. No injury or intimal hyperplasia was found acutely or chronically after the use of the LR system. This study establishes the accuracy, reproducibility, and safety of a nonimaging 2.7-Fr catheter for lumen sizing of coronary arteries. The system provides a continuous quantitative axial profile of the mean vessel lumen in real time and may have significant utility in vascular research and clinically in the catheterization laboratory.

Effects of stent sizing on endothelial and vessel wall stress: potential mechanisms for in-stent restenosis.

Stent sizing and apposition have been shown to be important determinants of clinical outcome. This study evaluates the mechanical effects of undersizing and oversizing of stents on endothelial wall shear stress (WSS) and vessel wall stress to determine a possible biomechanical mechanism of in-stent restenosis and thrombosis. Three-dimensional computational models of stents, artery, and internal fluid were created in a computer-assisted design package, meshed, and solved in finite element and computational fluid dynamic packages. The simulation results show that the effects of various degrees of undersizing on WSS, WSS gradient, and oscillatory shear index were highly nonlinear. As the degree of undersizing increased, the heterogeneity of WSS became smaller. The WSS distribution for the 20% undersizing was smooth and uniform, whereas the 5% case was very heterogeneous. The combination of lower WSS and higher WSS gradient and oscillatory shear index in the 5% undersized case may induce neointimal hyperplasia or thrombosis. Additionally, the oversizing simulation results show that the maximum intramural wall stress of the 20% oversizing case is significantly larger than the maximum stress for the 10% and zero oversizing cases. Edge stress concentration was observed, consistent with the restenosis typically observed in this region. This study demonstrates that proper sizing of stent is important for reducing the hemodynamic and mechanical disturbances to the vessel wall. Furthermore, the present findings may be used to improve stent design to reduce endothelial flow disturbances and intramural wall stress concentrations.