Dipyridamole Stress and Rest Myocardial Perfusion by 64-Detector Row Computed Tomography in Patients With Suspected Coronary Artery Disease

OBJECTIVES: Recently, stress myocardial computed tomographic perfusion (CTP) was shown to detect myocardial ischemia. Our main objective was to evaluate the feasibility of dipyridamole stress CTP and compare it to single-photon emission computed tomography (SPECT) to detect significant coronary stenosis using invasive conventional coronary angiography (CCA; stenosis >70%) as the reference method.

METHODS: Thirty-six patients (62 +/- 8 years old, 20 men) with previous positive results with SPECT (<2 months) as the primary inclusion criterion and suspected coronary artery disease underwent a customized multidetector-row CT protocol with myocardial perfusion evaluation at rest and during stress and coronary CT angiography (CTA). Multidetector-row computed tomography was performed in a 64-slice scanner with dipyridamole stress perfusion acquisition before a second perfusion/CT angiographic acquisition at rest. Independent blinded observers performed analysis of images from CTP, CTA, and CCA. All 36 patients completed the CT protocol with no adverse events (mean radiation dose 14.7 +/- 3.0 mSv) and with interpretable scans.

RESULTS: CTP results were positive in 27 of 36 patients (75%). From the 9 (25%) disagreements, 6 patients had normal coronary arteries and 2 had no significant stenosis (8 false-positive results with SPECT, 22%). The remaining patient had an occluded artery with collateral flow confirmed by conventional coronary angiogram. Good agreement was demonstrated between CTP and SPECT on a per-patient analysis (kappa 0.53). In 26 patients using CCA as reference, sensitivity, specificity, and positive and negative predictive values were 88.0%, 79.3%, 66.7%, and 93.3% for CTP and 68.8, 76.1%, 66.7%, and 77.8%, for SPECT, respectively (p = NS).

CONCLUSIONS: In conclusion, dipyridamole CT myocardial perfusion at rest and during stress is feasible and results are similar to single-photon emission CT scintigraphy. The anatomical-perfusion information provided by this combined CT protocol may allow identification of false-positive results by SPECT.

PMID: 20643238

Relation of Microchannel Structure Identified By Optical Coherence Tomography to Plaque Vulnerability in Patients With Coronary Artery Disease

OBJECTIVES: Increased neovascularization in atherosclerotic plaques is associated with plaque vulnerability. The high resolution of optical coherence tomography (OCT) might provide a chance to directly visualize plaque neovascularization in vivo. The aim of the present study was to investigate the relation between microchannels in culprit plaques identified by OCT and plaque vulnerability in patients with coronary artery disease.

METHODS: A total of 63 consecutive patients with coronary artery disease who had undergone both OCT and intravascular ultrasound before any interventions to examine culprit lesion morphologies were enrolled. Microchannel was defined as a no-signal tubuloluminal structure on the cross-sectional optical coherence tomographic image.

RESULTS: Microchannels were found in 24 (38%) of the 63 patients. The patients were divided into 2 groups according to the presence or absence of microchannels. The frequency of plaque rupture tended to be greater in the microchannel group (50% vs 28%, p = 0.11). The thickness of the fibrous cap (median 60 vs 100 microm, p = 0.001) was significantly less in the patients with microchannels, and significant differences were found in the frequency of thin-cap fibroatheroma (54% vs 21%, p = 0.012) and positive remodeling (67% vs 36%, p = 0.02) between the 2 groups. The high-sensitivity C-reactive protein levels in the microchannel group was significantly greater than those in the no-microchannel group (median 0.27 vs 0.13 mg/dl, p = 0.015). Moreover, increased microchannel counts were associated with greater high-sensitivity C-reactive protein levels (p = 0.01).

CONCLUSIONS: In conclusion, a significant relation was found between the presence of microchannels in plaques identified by OCT and plaque vulnerability in patients with coronary artery disease.

PMID: 20538113

Development of Lipid-Rich Plaque Inside Bare Metal Stent: Possible Mechanism of Late Stent Thrombosis? An Optical Coherence Tomography Study

OBJECTIVES: To study in-stent tissue characteristics by optical coherence tomography (OCT) at long-term follow-up in patients with previous bare metal stent implantation.

METHODS: Among 1636 patients who underwent bare metal stent (BMS) implantation between 1999 and 2006, 39 patients with 60 BMS who developed recurrent ischaemia underwent repeat catheterisation and OCT imaging between June 2008 and August 2009.

RESULTS: The average time interval between initial BMS implantation and OCT imaging was 6.5±1.3 years. A lesion that had features of lipid-rich plaque was found in 20 stents (33.3%) in 16 patients (41%). Fibrous intima was observed in the remaining 40 stents. In the group with lipid-rich plaque, average fibrous cap thickness was 56.7±5.8 μm and lipid arc was 173±58. Six patients had evidence of recent plaque disruption and another six patients had mural thrombus. Hypertension and smoking were more common in these patients than in those with fibrous intima.

CONCLUSIONS: Lipid-rich plaque with a thin fibrous cap was seen in patients with previous BMS implantation and recurrent ischaemia at late follow-up. This may be one possible mechanism for late stent thrombosis.

PMID: 20639235

Incremental Prognostic Value of Coronary CT Angiography in Patients With Suspected Coronary Artery Disease

OBJECTIVES: Multidetector CT coronary angiography (MDCTCA) is capable of detecting coronary artery disease (CAD) with a high diagnostic accuracy. In particular, this technique is credited with having a negative predictive value close to 100%. However, data about the prognostic value of MDCTCA are currently lacking. We sought to determine the prognostic value of MDCTCA in patients with suspected but undocumented CAD and, in particular, the incremental prognostic value as compared with clinical risk and calcium scoring.

METHODS: A total of 441 patients (age, 59.7+/-11.6 years) with suspected CAD underwent MDCTCA to evaluate the presence and severity of the disease. Patients were followed up as to the occurrence of hard cardiac events (cardiac death, nonfatal myocardial infarction, and unstable angina requiring hospitalization).

RESULTS: Coronary lesions were detected in 297 (67.3%) patients. During a mean follow-up of 31.9+/-14.8 months, 44 hard cardiac events occurred in 40 patients. CT calcium scoring showed a statistically significant incremental prognostic value as compared to a baseline clinical risk model (P=0.018), whereas MDCTCA provided an additional incremental prognostic value as compared with a baseline clinical risk model plus calcium scoring if considering both nonobstructive versus obstructive CAD (P=0.016) or, better, plaque composition (calcified versus noncalcified and/or mixed plaques, P=0.0001). During follow-up, an excellent prognosis was noted in patients with normal coronary arteries, with an annualized incidence rate of 0.88% if compared with those with mild CAD (3.89%) and with patients with significant coronary disease (8.09%). The presence of noncalcified or mixed plaques, regardless of lesion severity, was found to be the strongest predictor of events (P<0.0001) as a potential marker of plaque vulnerability.

CONCLUSIONS: MDCTCA provides independent and incremental prognostic information as compared to baseline clinical risk factors and calcium scoring in patients with suspected CAD.

PMID: 20460497

Remodeling of Carotid Arteries Detected with MR Imaging: Atherosclerosis Risk in Communities Carotid MRI Study

OBJECTIVES: To determine the extent of thickening of the carotid arterial walls that may be accommodated by outward remodeling.

METHODS: Institutional review board approval was obtained at each participating site, and informed consent was obtained from each participant. All study sites conducted this study in compliance with HIPAA requirements. A total of 2066 participants (age range, 60-85 years) from the Atherosclerosis Risk in Communities (ARIC) study were enrolled in the ARIC Carotid MRI Study. Maximum wall thickness and luminal area were measured with gadolinium-enhanced magnetic resonance (MR) imaging in both common carotid arteries (CCAs) and in one internal carotid artery (ICA) 2 mm above the flow divider. Complete data were available for 1064 ICAs and 3348 CCAs. The association of maximum wall thickness with lumen area was evaluated with linear regression, and adjustments were made for participant age, sex, race, height, and height squared.

RESULTS: In the ICA, lumen area was relatively constant across patients with a wall thickness of 1.38 mm or less. In patients with a wall thickness of more than 1.38 mm, however, lumen area decreased linearly as wall thickness increased. Wall area represented a median of 61.9% of the area circumscribed by the vessel at a maximum wall thickness of 1.50 mm +/- 0.05 (standard deviation) and 75.4% at a maximum wall thickness of 4.0 mm +/- 0.10. In the CCA, lumen area was preserved across wall thicknesses less than 2.06 mm, representing 99% of vessels.

CONCLUSIONS: Atherosclerotic thickening in the ICA appears to be accommodated for vessels with a maximum wall thickness of less than 1.5 mm. Beyond this threshold, greater thickness is associated with a smaller lumen. The CCA appears to accommodate a wall thickness of less than 2.0 mm. These estimates indicate that the carotid arteries are able to compensate for a greater degree of thickening than are the coronary arteries.

PMID: 20651061

Minimally-Invasive Valve Surgery: STATE-OF-THE-ART PAPER

Minimally-invasive approaches have become increasingly important in cardiac valve surgery. Smaller incisions have become commonplace in many major centers. We reviewed the existing literature and present the current state-of-the-art of minimally-invasive valve operations in this paper.

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Aortic Stiffness Independently Predicts Exercise Capacity in Hypertrophic Cardiomyopathy: A Multimodality Imaging Study

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Cardiac Computed Tomography and Myocardial Perfusion Scintigraphy for Risk Stratification in Asymptomatic Individuals Without Known Cardiovascular Disease: A Position Statement of The Working Group on Nuclear Cardiology and Cardiac CT of the European Society of Cardiology

OBJECTIVES: Cardiovascular events remain one of the most frequent causes of mortality and morbidity worldwide. The majority of cardiac events occur in individuals without known coronary artery disease (CAD) and in low- to intermediate-risk subjects. Thus, the development of improved preventive strategies may substantially benefit from the identification, among apparently intermediate-risk subjects, of those who have a high probability for developing future cardiac events. Cardiac computed tomography and myocardial perfusion scintigraphy (MPS) by single photon emission computed tomography may play a role in this setting. In fact, absence of coronary calcium in cardiac computed tomography and inducible ischaemia in MPS are associated with a very low rate of major cardiac events in the next 3–5 years.

METHODS: Based on current evidence, the evaluation of coronary calcium in primary prevention subjects should be considered in patients classified as intermediate-risk based on traditional risk factors, since high calcium scores identify subjects at high-risk who may benefit from aggressive secondary prevention strategies. In addition, calcium scoring should be considered for asymptomatic type 2 diabetic patients without known CAD to select those in whom further functional testing by MPS or other stress imaging techniques may be considered to identify patients with significant inducible ischaemia.

RESULTS: From available data, the use of MPS as first line testing modality for risk stratification is not recommended in any category of primary prevention subjects with the possible exception of first-degree relatives of patients with premature CAD in whom MPS may be considered.

CONCLUCIONS: However, the Working Group recognizes that neither the use of computed tomography for calcium imaging nor of MPS have been proven to significantly improve clinical outcomes of primary prevention subjects in prospective controlled studies. This information would be crucial to adequately define the role of imaging approaches in cardiovascular preventive strategies.

PMID: 20630895

Small Coronary Calcifications Are Not Detectable by 64-Slice Contrast Enhanced Computed Tomography

OBJECTIVES: Recently, small calcifications have been associated with unstable plaques. Plaque calcifications are both in intravascular ultrasound (IVUS) and multi-slice computed tomography (MSCT) easily recognized. However, smaller calcifications might be missed on MSCT due to its lower resolution.

METHODS: Because it is unknown to which extent calcifications can be detected with MSCT, we compared calcification detection on contrast enhanced MSCT with IVUS. The coronary arteries of patients with myocardial infarction or unstable angina were imaged by 64-slice MSCT angiography and IVUS. The IVUS and MSCT images were registered and the arteries were inspected on the presence of calcifications on both modalities independently. We measured the length and the maximum circumferential angle of each calcification on IVUS.

RESULTS: In 31 arteries, we found 99 calcifications on IVUS, of which only 47 were also detected on MSCT. The calcifications missed on MSCT (n = 52) were significantly smaller in angle (27° ± 16° vs. 59° ± 31°) and length (1.4 ± 0.8 vs. 3.7 ± 2.2 mm) than those detected on MSCT. Calcifications could only be detected reliably on MSCT if they were larger than 2.1 mm in length or 36° in angle.

CONCLUSIONS: Half of the calcifications seen on the IVUS images cannot be detected on contrast enhanced 64-slice MSCT angiography images because of their size. The limited resolution of MSCT is the main reason for missing small calcifications.

PMID: 20602171

Prognostic Significance of Myocardial Fibrosis Quantification by Histopathology and Magnetic Resonance Imaging in Patients With Severe Aortic Valve Disease

OBJECTIVES: Does myocardial fibrosis (MF) in patients with severe aortic valve (AV) disease, assessed by histopathology or contrast-enhanced magnetic resonance imaging (ce-MRI), predict outcomes following surgical AV replacement?

METHODS: Fifty-four patients (mean age 46.8 years, 78% male) with symptomatic severe aortic regurgitation (n = 26) or aortic stenosis (n = 28) were prospectively evaluated. All patients underwent preoperative quantitative assessment of MF by ce-MRI and had myocardial tissue samples obtained during surgery for histopathologic evaluation. Patients were grouped based on degree of MF and were compared to assess for differences in left ventricular (LV) functional improvement and survival postoperatively.

RESULTS: ce-MRI assessment of MF correlated well with histopathology (r = 0.69, p < 0.0001), and the degree of MF was higher in the study group than in normal controls. LV functional changes were evaluated in 25 patients who underwent follow-up MRI; LV mass was decreased and LV ejection fraction (EF) improved (EF 54 ± 10% pre-op vs. 59 ± 14% post-op, p = 0.02). LVEF improvement was inversely related to the degree of pre-op MF. Overall, those who died had more MF, and this increased burden of MF was associated with lower postoperative survival. Finally, on multivariate analysis, the amount of MF, along with advanced age, independently predicted all-cause mortality.

CONCLUSIONS: In patients with severe AV disease, the amount of MF assessed by histopathology or ce-MRI is associated with LV function improvement and mortality. 

PMID: 20633819

Serial Coronary CT Angiography-Verified Changes in Plaque Characteristics as an End Point: Evaluation of Effect of Statin Intervention

OBJECTIVES: This study sought to assess, by serial computed tomography angiography (CTA), the effect of statin treatment on coronary plaque morphology. In addition to the assessment of luminal stenosis, CTA also allows characterization of plaque morphology. Large, positively remodeled plaques with large necrotic cores have been reported as indicators of plaque instability.

METHODS: CTA was performed in 32 patients (26 men, ages 64.3 ± 8.5 years). Of these, 24 received fluvastatin after the baseline study; 8 subjects who refused statin treatment were followed as the control subjects. Serial imaging was performed after a median interval of 12 months. All vessels were examined in every subject, and a 10-mm-long segment was identified for comparison before and after intervention. Total plaque volume, low attenuation plaque (LAP) volume, lumen volume, and remodeling index were calculated.

RESULTS: In the statin-treated patients, the total plaque volume (92.3 ± 37.7 vs. 76.4 ± 26.5 mm³, p < 0.01) and LAP volume (4.9 ± 7.8 vs. 1.3 ± 2.3 mm³, p = 0.01) were significantly reduced over time; however, there was no change in the lumen volume (63.9 ± 25.3 vs. 65.2 ± 26.2 mm³, p = 0.59). On the other hand, no change was observed in the CTA characteristics in the control subjects, including total plaque volume (94.4 ± 21.2 vs. 98.4 ± 28.6 mm³, p = 0.48), LAP volume (2.1 ± 3.0 vs. 2.3 ± 3.6 mm³, p = 0.91), and lumen volume (80.5 ± 20.7 vs. 75.0 ± 16.3 mm³, p = 0.26). The plaque volume change (–15.9 ± 22.2 vs. 4.0 ± 14.0 mm³, p = 0.01) and LAP volume change (–3.7 ± 7.0 vs. 0.2 ± 1.5 mm³, p < 0.01) were significantly greater in the statin than the control group. The lumen volume (1.3 ± 15.6 vs. –5.5 ± 13.1 mm³, p = 0.24) and remodeling index (–2.4 ± 6.8% vs. –0.3 ± 6.5%, p = 0.53) did not show the significant differences between the 2 groups. The decrease in the plaque volume was due to reduction in the LAP volume (R = 0.83, p < 0.01), and was not related to any changes in the lumen volume (R = 0.21, p = 0.24).

CONCLUSIIONS: This preliminary study suggests that serial CTA evaluation of coronary plaques allows for the assessment of interval change in the plaque morphology. Statin treatment results in decreases in the plaque and necrotic core volume. The features known to be associated with plaque instability.

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Accuracy of Dual-Source Computed Tomography to Identify Significant Coronary Artery Disease in Patients With Atrial Fibrillation: Comparison With Coronary Angiography

OBJECTIVES: It has been previously reported that the sensitivity and specificity of multislice computed tomography (CT) for detecting significant coronary artery disease (CAD) is high. However, regular sinus rhythm has been considered a prerequisite for an adequate examination, even though atrial fibrillation (AF) is common among patients evaluated for the presence of coronary heart disease. In this study, we investigated the sensitivity and specificity of dual-source CT (DSCT) to detect and rule out significant coronary stenoses in patients with AF referred for invasive coronary angiography.

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Cumulative Exposure to Ionizing Radiation from Diagnostic and Therapeutic Cardiac Imaging Procedures: A Population-Based Analysis

OBJECTIVES: The purpose of this study was to describe radiation exposure from cardiac imaging procedures over time in a general population. Cardiac imaging procedures frequently expose patients to ionizing radiation, but their contribution to effective doses of radiation in the general population is unknown.

METHODS: We used administrative claims to identify cardiac imaging procedures performed from 2005 to 2007 in 952,420 nonelderly insured adults in 5 U.S. health care markets. We estimated 3-year cumulative effective doses of radiation in millisieverts from these procedures We then calculated population-based annual rates of radiation exposure to effective doses 3 mSv/year (background level ofradiation from natural sources), >3 to 20 mSv/year, or >20 mSv/year (upper annual limit for occupational exposure averaged over 5 years).

RESULTS: A total of 90,121 (9.5%) individuals underwent at least 1 cardiac imaging procedure using radiation. Among patients who underwent 1 cardiac imaging procedures, the mean cumulative effective dose over 3 years was 16.4 mSv (range 1.5 to 189.5 mSv). Myocardial perfusion imaging accounted for 74% of the cumulative effective dose. Overall, 47.8% of cardiac imaging procedures were performed in physician offices; this proportion was higher for myocardial perfusion imaging (74.8%) and cardiac computed tomography studies (76.5%). The annual population-based rate of receiving an effective dose of >3 to 20 mSv/year was 89.0 per 1,000; and 3.3 per 1,000 for cumulative doses >20 mSv/year. Annual effective doses increased with age and were generally higher among men.

CONCLUSIONS: Cardiac imaging procedures lead to substantial radiation exposure and effective doses for many patients in the U.S.

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Safety and Efficacy of the Subclavian Approach for Transcatheter Aortic Valve Implantation With the CoreValve Revalving System

OBJECTIVES: Transcatheter aortic valve implantation (TAVI) is a new option for patients with severe aortic stenosis at high surgical risk. The standard retrograde approach through the femoral artery is contraindicated in case of unfavorable iliofemoral anatomy or extensive disease. In these patients, a trans-subclavian approach may be feasible.

METHODS: Between June 2007 and July 2009, TAVI with the CoreValve bioprosthesis (Medtronic, Minneapolis, Minn) was performed in 514 consecutive patients at 13 Italian hospitals, using the subclavian approach in 54 cases.

RESULTS: The median logistic EuroSCORE was significantly higher in the subclavian (19.4; interquartile range, 12.5 to 29.8) versus femoral group (25.3; interquartile range, 15.1 to 36.6) (P=0.03), as well as the rate of comorbidities. Procedural success was obtained in 100% versus 98.4% of the subclavian versus femoral groups, respectively (P=0.62), with intraprocedural mortality of 0% versus 0.9% (P=1.00). The most common in-hospital complications were a new left bundle-branch block (22.4%) and the need for pacemaker (16.3%). No specific complications for the subclavian access (vessel rupture, vertebral or internal mammary ischemia) were reported. The learning curve for the subclavian approach led to a wider use of local anesthesia. Thirty-day mortality was 0% versus 6.1% in the subclavian versus femoral groups, respectively (P=0.13). Six-month mortality rate was 9.4% versus 15.8% (P=0.44), whereas valve-related adverse events were 13.6% versus 13.9% (P=0.79). \

CONCLUSIONS: TAVI through the subclavian approach appeared feasible and safe, with excellent procedural success and low in-hospital complication rates. This new technique allows patients with contraindications to the femoral approach to be treated with TAVI.

PMID: 20606135

Single-Photon Emission Computed Tomography Myocardial Perfusion Imaging and the Risk of Sudden Cardiac Death in Patients With Coronary Disease and Left Ventricular Ejection Fraction >35%

OBJECTIVES: The aim of this study was to determine whether single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) is an effective method of risk stratification for sudden cardiac death (SCD) in patients with coronary artery disease (CAD) and left ventricular ejection fraction (LVEF) >35%. Most victims of SCD have an LVEF >35%.

METHODS: The study population included 4,865 patients with CAD and LVEF >35% who underwent gated SPECT MPI. We used Cox proportional hazard modeling to examine the relationship between patient characteristics and SCD.

RESULTS: The median age of the population was 63 years (25th, 75th percentile: 54, 71 years), and the median LVEF was 56% (25th, 75th percentile: 50%, 64%). The median follow-up for all patients was 6.5 years (25th, 75th percentile: 3.6, 9.3 years). During follow-up, there were 161 SCDs (3.3%). After multivariable adjustment, LVEF, the Charlson index, hypertension, smoking, antiarrhythmic drug therapy, and the summed stress score (SSS) were associated with SCD (all p < 0.05). For each 3-U increase in the SSS, the hazard ratio for SCD was 1.13 (95% confidence interval: 1.04 to 1.23). The addition of perfusion data to the clinical history and LVEF was associated with increased discrimination for SCD events (c-index 0.728). Risk stratification with a derived SPECT nomogram did not result in statistically significant net reclassification improvement (p = 0.26) or integrated discrimination improvement (p = 0.38).

CONCLUSIONS: Among patients with CAD and LVEF >35%, the extent of stress MPI perfusion defects is associated with an increased risk of SCD. Future large prospective studies should address the role of perfusion imaging in the identification of high-risk patients with LVEF >35% who might benefit from ICD implantation.

PMID: 19808541