Med Biol Eng Comput. 2012; 50(1):53-59

Capelli C, Bosi GM, Cerri E, Nordmeyer J, Odenwald T, Bonhoeffer P, Migliavacca F, Taylor AM, Schievano S

OBJECTIVES: Transcatheter aortic valve implantation (TAVI) enables treatment of aortic stenosis with no need for open heart surgery. According to current guidelines, only patients considered at high surgical risk can be treated with TAVI. In this study, patient-specific analyses were performed to explore the feasibility of TAVI in morphologies, which are currently borderline cases for a percutaneous approach.

METHODS: Five patients were recruited: four patients with failed bioprosthetic aortic valves (stenosis) and one patient with an incompetent, native aortic valve. Three-dimensional models of the implantation sites were reconstructed from computed tomography images. Within these realistic geometries, TAVI with an Edwards Sapien stent was simulated using finite element (FE) modelling. Engineering and clinical outcomes were assessed.

RESULTS: In all patients, FE analysis proved that TAVI was morphologically feasible. After the implantation, stress distribution showed no risks of immediate device failure and geometric orifice areas increased with low risk of obstruction of the coronary arteries. Maximum principal stresses in the arterial walls were higher in the model with native outflow tract.

CONCLUSIONS: FE analyses can both refine patient selection and characterise device mechanical performance in TAVI, overall impacting on procedural safety in the early introduction of percutaneous heart valve devices in new patient populations.

PMID: 22286953

J Am Coll Cardiol. 2012; 59(2):119-127

Hamdan A, Guetta V, Konen E, Goitein O, Segev A, Raanani E, Spiegelstein D, Hay I, Di Segni E, Eldar M, Schwammenthal E

OBJECTIVES: The purpose of this study was to assess deformation dynamics and in vivo mechanical properties of the aortic annulus throughout the cardiac cycle. Understanding dynamic aspects of functional aortic valve anatomy is important for beating-heart transcatheter aortic valve implantation.

METHODS: Thirty-five patients with aortic stenosis and 11 normal subjects underwent 256-slice computed tomography. The aortic annulus plane was reconstructed in 10% increments over the cardiac cycle. For each phase, minimum diameter, ellipticity index, cross-sectional area (CSA), and perimeter (Perim) were measured. In a subset of 10 patients, Young’s elastic module was calculated from the stress-strain relationship of the annulus.

RESULTS: In both subjects with normal and with calcified aortic valves, minimum diameter increased in systole (12.3 ± 7.3% and 9.8 ± 3.4%, respectively; p < 0.001), and ellipticity index decreased (12.7 ± 8.8% and 10.3 ± 2.7%, respectively; p < 0.001). The CSA increased by 11.2 ± 5.4% and 6.2 ± 4.8%, respectively (p < 0.001). Perim increase was negligible in patients with calcified valves (0.56 ± 0.85%; p < 0.001) and small even in normal subjects (2.2 ± 2.2%; p = 0.01). Accordingly, relative percentage differences between maximum and minimum values were significantly smallest for Perim compared with all other parameters. Young’s modulus was calculated as 22.6 ± 9.2 MPa in patients and 13.8 ± 6.4 MPa in normal subjects.

CONCLUSIONS: The aortic annulus, generally elliptic, assumes a more round shape in systole, thus increasing CSA without substantial change in perimeter. Perimeter changes are negligible in patients with calcified valves, because tissue properties allow very little expansion. Aortic annulus perimeter appears therefore ideally suited for accurate sizing in transcatheter aortic valve implantation.

PMID: 22222074

Eur J Echocardiogr. 2012; 13(1):79-85

Joutsiniemi E, Saraste A, Pietilä M, Ukkonen H, Kajander S, Mäki M, Koskenvuo J, Airaksinen J, Hartiala J, Saraste M, Knuuti J

OBJECTIVES: Accelerated flow at the site of flow-limiting stenosis can be detected by transthoracic Doppler echocardiography (TTDE). We studied feasibility and accuracy of sequential coronary computed tomography angiography (CTA) and TTDE in detection of haemodynamically significant coronary artery disease (CAD).

METHODS: We prospectively enrolled 107 patients with intermediate (30-70%) pre-test likelihood of CAD. All patients underwent CTA using a 64-slice scanner. Using TTDE, the ratio of maximal diastolic flow velocity to pre-stenotic flow velocity (M/P ratio) was measured in the coronary segments with stenosis in CTA. In all patients, the results were compared with invasive coronary angiography, including measurement of fractional flow reserve when appropriate. All analyses were done blinded.

RESULTS: TTDE was feasible in 276 of 285 evaluated coronary segments. Significant coronary stenoses were associated with a higher M/P ratio than non-significant stenoses (3.59 ± 1.82 vs. 1.28 ± 0.60, P < 0.001). The optimal M/P ratio for detection of significant stenosis was 2.2 (area under receiver operating characteristic curve 0.92, P < 0.001). Compared with the strategy of CTA alone, sequential CTA and focused TTDE had a better positive predictive value (PPV; 61 vs. 78%) and diagnostic accuracy (93 vs. 96%, P = 0.006) without impairment of the negative predictive value (97 vs. 97%).

CONCLUSIONS: Sequential use of CTA and TTDE is feasible for combined anatomic and functional evaluation of coronary stenoses. Compared with coronary CTA alone, addition of TTDE improved PPV for detection of significant CAD.

PMID: 21880607

J Am Coll Cardiol. 2012; 59(5):462-474

Rory Hachamovitch, Benjamin Nutter, Mark A. Hlatky, Leslee J. Shaw, Michael L. Ridner, Sharmila Dorbala, Rob S.B. Beanlands, Benjamin J.W. Chow, Elizabeth Branscomb, Panithaya Chareonthaitawee, W. Guy Weigold, Szilard Voros, Suhny Abbara, Tsunehiro Yasuda, Jill E. Jacobs, John Lesser, Daniel S. Berman, Louise E.J. Thomson, Subha Raman, Gary V. Heller, Adam Schussheim, Richard Brunken, Kim A. Williams, Susan Farkas, Dominique Delbeke, Uwe J. Schoepf, Nathaniel Reichek, Stuart Rabinowitz, Steven R. Sigman, Randall Patterson, Carolyn R. Corn, Richard White, Ella Kazerooni, James Corbett, Sabahat Bokhari, Josef Machac, Erminia Guarneri, Salvador Borges-Neto, John W. Millstine, James Caldwell, James Arrighi, Udo Hoffmann, Matthew Budoff, Joao Lima, James R. Johnson, Barbara Johnson, Mariya Gaber, Julie A. Williams, Courtney Foster, Jon Hainer, Marcelo F. Di Carli SPARC Investigators

OBJECTIVES: This study examined short-term cardiac catheterization rates and medication changes after cardiac imaging. Noninvasive cardiac imaging is widely used in coronary artery disease, but its effects on subsequent patient management are unclear.

METHODS: We assessed the 90-day post-test rates of catheterization and medication changes in a prospective registry of 1,703 patients without a documented history of coronary artery disease and an intermediate to high likelihood of coronary artery disease undergoing cardiac single-photon emission computed tomography, positron emission tomography, or 64-slice coronary computed tomography angiography.

RESULTS: Baseline medication use was relatively infrequent. At 90 days, 9.6% of patients underwent catheterization. The rates of catheterization and medication changes increased in proportion to test abnormality findings. Among patients with the most severe test result findings, 38% to 61% were not referred to catheterization, 20% to 30% were not receiving aspirin, 35% to 44% were not receiving a beta-blocker, and 20% to 25% were not receiving a lipid-lowering agent at 90 days after the index test. Risk-adjusted analyses revealed that compared with stress single-photon emission computed tomography or positron emission tomography, changes in aspirin and lipid-lowering agent use was greater after computed tomography angiography, as was the 90-day catheterization referral rate in the setting of normal/nonobstructive and mildly abnormal test results.

CONCLUSIONS: Overall, noninvasive testing had only a modest impact on clinical management of patients referred for clinical testing. Although post-imaging use of cardiac catheterization and medical therapy increased in proportion to the degree of abnormality findings, the frequency of catheterization and medication change suggests possible undertreatment of higher risk patients. Patients were more likely to undergo cardiac catheterization after computed tomography angiography than after single-photon emission computed tomography or positron emission tomography after normal/nonobstructive and mildly abnormal study findings.

PMID:

Circ Cardiovasc Imaging. 2012; 5(1):147-154

Truong QA, Massaro JM, Rogers IS, Mahabadi AA, Kriegel MF, Fox CS, O'Donnell CJ, Hoffmann U

OBJECTIVES: Main pulmonary artery diameter (mPA) and ratio of mPA to ascending aorta diameter (ratio PA) derived from chest CT are commonly reported in clinical practice. We determined the age- and sex-specific distribution and normal reference values for mPA and ratio PA by CT in an asymptomatic community-based population.

METHODS: In 3171 men and women (mean age, 51±10 years; 51% men) from the Framingham Heart Study, a noncontrast, ECG-gated, 8-slice cardiac multidetector CT was performed. We measured the mPA and transverse axial diameter of the ascending aorta at the level of the bifurcation of the right pulmonary artery and calculated the ratio PA. We defined the healthy referent cohort (n=706) as those without obesity, hypertension, current and past smokers, chronic obstructive pulmonary disease, history of pulmonary embolism, diabetics, cardiovascular disease, and heart valve surgery.

RESULTS: The mean mPA diameter in the overall cohort was 25.1±2.8 mm and mean ratio PA was 0.77±0.09. The sex-specific 90th percentile cutoff value for mPA diameter was 28.9 mm in men and 26.9 mm in women and was associated with increase risk for self-reported dyspnea (adjusted odds ratio, 1.31; P=0.02). The 90th percentile cutoff value for ratio PA of the healthy referent group was 0.91, similar between sexes but decreased with increasing age (range, 0.82-0.94), though not associated with dyspnea.

CONCLUSIONS: For simplicity, we established 29 mm in men and 27 mm in women as sex-specific normative reference values for mPA and 0.9 for ratio PA.

PMID: 22178898

Am J Cardiol. 2012; 109(3):320-326

Hayano S, Ichimiya S, Ishii H, Kanashiro M, Watanabe J, Kurebayashi N, Yoshikawa D, Amano T, Matsubara T, Murohara T

OBJECTIVES: It is well known that chronic kidney disease is a risk factor for atherosclerosis. The present study was conducted to identify any relation between the estimated glomerular filtration rate (eGFR) and coronary plaque characteristics using integrated backscatter intravascular ultrasound (IB-IVUS), which can detect coronary plaque composition.

METHODS: We performed IB-IVUS for 201 consecutive patients undergoing percutaneous coronary intervention, and they were divided into 3 groups according to the eGFR values (group 1 [n = 20], ≥90 ml/min/1.73 m(2); group 2 [n = 123], 60 to 90 ml/min/1.73 m(2); and group 3 [n = 58], <60 ml/min/1.73 m(2)). Coronary plaques in nonculprit lesions on 3-dimensional analysis were evaluated using IB-IVUS.

RESULTS: The baseline characteristics were similar, except for older age and a greater prevalence of men in group 3. IB-IVUS showed a percentage of lipid volume of 44.7 ± 5.0% in group 1, 53.6 ± 6.2% in group 2, and 63.5 ± 6.2% in group 3 (p <0.01), with a corresponding percentage of fibrous volume of 53.9 ± 4.9%, 45.1 ± 6.0%, and 35.3 ± 6.1%, respectively (p <0.01). The eGFR correlated significantly with both parameters (r = -0.68, p <0.001 and r = 0.68, p <0.001, respectively).

CONCLUSIONS: In conclusion, lower eGFR levels were associated with greater lipid and lower fibrous contents, contributing to coronary plaque vulnerability.

PMID: 22245411

JACC Cardiovasc Imaging. 2012; 5(1):71-82

Nakano M, Vorpahl M, Otsuka F, Taniwaki M, Yazdani SK, Finn AV, Ladich ER, Kolodgie FD, Virmani R

OBJECTIVES: This study sought to examine the capability of optical frequency domain imaging (OFDI) to characterize various morphological and histological responses to stents implanted in human coronary arteries. A precise assessment of vascular responses to stents may help stratify the risk of future adverse events in patients who have been treated with coronary stents.

METHODS: Fourteen human stented coronary segments with implant duration ≥1 month from 10 hearts acquired at autopsy were interrogated ex vivo by OFDI and intravascular ultrasound (IVUS). Comparison with histology was assessed in 134 pairs of images where the endpoints were to investigate: 1) accuracy of morphological measurements; 2) detection of uncovered struts; and 3) characterization of neointima.

RESULTS: Although both OFDI and IVUS provided a good correlation of neointimal area with histology, the correlation of minimum neointimal thickness was inferior in IVUS (R(2) = 0.39) as compared with OFDI (R(2) = 0.67). Similarly, IVUS showed a weak correlation of the ratio of uncovered to total stent struts per section (RUTSS) (R(2) = 0.24), whereas OFDI maintained superiority (R(2) = 0.66). In a more detailed analysis by OFDI, identification of individual uncovered struts demonstrated a sensitivity of 77.9% and specificity of 96.4%. Other important morphological features such as fibrin accumulation, excessive inflammation (hypersensitivity), and in-stent atherosclerosis were characterized by OFDI; however, the similarly dark appearance of these tissues did not allow for direct visual discrimination. The quantitative analysis of OFDI signal reflections from various in-stent tissues demonstrated distinct features of organized thrombus and accumulation of foamy macrophages.

CONCLUSIONS: The results of the present study reinforce the potential of OFDI to detect vascular responses that may be important for the understanding of long-term stent performance, and indicate the capability of this technology to serve as a diagnostic indicator of clinical success.

PMID: 22239896

JACC Cardiovasc Interv. 2011; 4(11):1175-1182

Muller O, Mangiacapra F, Ntalianis A, Verhamme KM, Trana C, Hamilos M, Bartunek J, Vanderheyden M, Wyffels E, Heyndrickx GR, van Rooij FJ, Witteman JC, Hofman A, Wijns W, Barbato E, De Bruyne B

OBJECTIVES: This study sought to evaluate the long-term clinical outcome of patients with an angiographically intermediate left anterior descending coronary artery (LAD) stenosis in whom the revascularization strategy was based on fractional flow reserve (FFR). When revascularization is based mainly on angiographic guidance, a number of hemodynamically nonsignificant stenoses will be revascularized.

METHODS: In 730 patients with a 30% to 70% isolated stenosis in the proximal LAD and no significant valvular disease, FFR measurements were obtained to guide treatment strategy. When FFR was ≥ 0.80, the patients (n = 564) were treated medically (medical group); when FFR was <0.80, the patients (n = 166) underwent a revascularization procedure (revascularization group; 13% coronary artery bypass graft surgery and 87% percutaneous coronary intervention). A 100% long-term clinical follow-up (median follow-up: 40 months) was obtained. The 5-year survival of the medical group was compared with that of a reference population. For each patient, 4 controls were selected from an age- and sex-matched control population.

RESULTS: The 5-year survival estimate was 92.9% in the medical group versus 89.6% in the controls (p = 0.74). The mean diameter stenosis was significantly smaller in the medical than in the revascularization group (39 ± 14% vs. 54 ± 13%, p < 0.0001), but there was a large overlap between both groups. The 5-year event-free survival estimates (death, myocardial infarction, and target vessel revascularization) were 89.7% and 68.5%, respectively (p < 0.0001).

CONCLUSIONS: Medical treatment of patients with a hemodynamically nonsignificant stenosis (FFR ≥ 0.80) in the proximal LAD is associated with an excellent long-term clinical outcome with survival at 5 years similar to an age- and sex-matched control population.

PMID: 22035875

Radiographics. 2012; 32(1):9-32

Elena Pena, Carole Dennie, John Veinot, and Susana Hernandez Muniz

Pulmonary hypertension is defined as an abnormal elevation of pressure in pulmonary circulation, with a mean pulmonary arterial pressure higher than 25 mmHg, regardless of the underlying mechanism. The clinical classification system for pulmonary hypertension was updated at the fourth World Symposium on Pulmonary Hypertension in Dana Point, California, in 2008. In patients with suspected pulmonary hypertension, the diagnostic approach includes four stages: suspicion, detection, classification, and functional evaluation. It is crucial to understand the advantages and disadvantages of the different imaging tools available for the diagnostic work-up and follow-up of patients with pulmonary hypertension. Many conditions that cause pulmonary hypertension have suggestive findings at multidetector computed tomography or magnetic resonance imaging; some causes may be surgically treatable, whereas others may demonstrate adverse reactions to vasodilator therapies used during the course of treatment. Therefore, the radiologist plays an important role in evaluating patients with this disease.

PMID: 22236891

J Cardiovasc Comput Tomogr. 2011; 5(6):357-369

Ghoshhajra BB, Maurovich-Horvat P, Techasith T, Medina HM, Verdini D, Sidhu MS, Blankstein R, Brady TJ, Cury RC

OBJECTIVES: Cardiac CT has the potential to offer comprehensive infarct detection by assessing regional wall motion abnormalities (RWMAs), rest perfusion defects (RPDs), and delayed contrast enhancement (DCE). However, the diagnostic accuracy of these techniques for the detection of myocardial infarction (MI) is unknown.

METHODS: Forty-eight patients with intermediate-to-high probability for coronary artery disease after single-photon emitting CT myocardial perfusion imaging were prospectively enrolled for a research comprehensive 64-detector row dual-source cardiac CT protocol that included cine images for RWMA, first-pass images for RPD, and delayed images for DCE. Blinded readers independently assessed each technique. Subsequently, a final combined analysis (cine + rest + DCE) was performed. The universal definition for MI by the 2007 American Heart Association task force was used as the “gold standard.”

RESULTS: Twenty-four of 48 patients (50%) had infarct by the universal definition. The combined CT analysis was most accurate (90%) with the highest per-patient sensitivity (88%) and specificity (92%) versus individual assessments (RWMA, 79% and 88%; RPD, 67% and 92%; DCE, 79% and 88%). Similar findings were observed on a per-vessel basis analysis. A combination of DCE and cine showed a good accuracy (85%) and high sensitivity (92%).

CONCLUSIONS: Infarct detection with CT is feasible with overall good diagnostic accuracy compared with the universal definition. A combined evaluation that included all techniques (cine, RPD, and DCE) had the highest diagnostic accuracy. These findings may have implications when designing future clinical and research CT protocols for optimal infarct detection.

PMID: 22210535