Assessment of Semi-automated Computed Tomographic Measures of Segmental Perfusion Defects in a Swine Model (Sus scrofa) of Intermediate Coronary Lesions.

Computed tomographic myocardial perfusion (CTP) imaging is a tool that shows promise in emergent settings for defining the hemodynamic significance of coronary artery disease. In this study, we examined the accuracy with which the transmural perfusion ratio (TPR) derived through semiautomated CTP analysis reflected segmental perfusion defects associated with intermediate coronary artery lesions in swine. Lesions (diameter stenosis, 65% ± 11%) of the left anterior descending coronary artery (LAD) were created in 10 anesthetized female swine (weight, 47.5 ± 1.9 kg) by using a pneumatic occlusion device implanted on the LAD. Occluder inflation pressures were adjusted to maintain fractional flow reserve (FFR, 74.3 ± 1.7) during adenosine infusion (140ug/kg/min). Static CTP imaging using a stress-rest protocol and segmental TPR derived from semiautomated CT perfusion software was compared with microsphere-derived TPR (mTPR) by using a 16-segment model and polar mapping. Intermediate LAD stenosis was verified through multiplanar coronary CT angiography. Receiver operating characteristic analysis identified an optimal threshold for segmental perfusion defects for intermediate lesions (TPR threshold, ≤0.80); however, the area under the receiver operating characteristic curve was 0.58, and the overall accuracy was 63%. At this threshold, the sensitivity and specificity were 65% and 61%, and the positive and negative predictive values were 61% and 65%, respectively. Although CTP-TPR illustrated segmental perfusion defects with intermediate lesions, the disparity between CTP-TPR and mTPR measures of segmental perfusion suggests that further advances in analysis software may be necessary to improve the localization of segmental defects for intermediated lesions.

Effects of adenosine and regadenoson on hemodynamics measured using cardiovascular magnetic resonance imaging.

BACKGROUND: Adenosine or regadenoson vasodilator stress cardiovascular magnetic resonance (CMR) is an effective non-invasive strategy for evaluating symptomatic coronary artery disease. Vasodilator injection typically precedes ventricular functional sequences to efficiently reduce overall scanning times, though the effects of vasodilators on CMR-derived ventricular volumes and function are unknown. METHODS: We prospectively enrolled 25 healthy subjects to undergo consecutive adenosine and regadenoson administration. Short axis CINE datasets were obtained on a 1.5 T scanner following adenosine (140mcg/kg/min IV for 6 min) and regadenoson (0.4 mg IV over 10 s) at baseline, immediately following administration, at 5 min intervals up to 15 min. Hemodynamic response, bi-ventricular volumes and ejection fractions were determined at each time point. RESULTS: Peak heart rate was observed early following administration of both adenosine and regadenoson. Heart rate returned to baseline by 10 min post-adenosine while remaining elevated at 15 min post-regadenoson (p = 0.0015). Left ventricular (LV) ejection fraction (LVEF) increased immediately following both vasodilators (p < 0.0001 for both) and returned to baseline following adenosine by 10 min (p = 0.8397). Conversely, LVEF following regadenoson remained increased at 10 min (p = 0.003) and 15 min (p = 0.0015) with a mean LVEF increase at 15 min of 4.2 ± 1.3%. Regadenoson resulted in a similar magnitude reduction in both LV end-diastolic volume index (LVEDVi) and LV end-systolic volume index (LVESVi) at 15 min whereas LVESVi resolved at 15 min following adenosine and LVEDVi remained below baseline values (p = 0.52). CONCLUSIONS: Regadenoson and adenosine have significant and prolonged impact on ventricular volumes and LVEF. In patients undergoing vasodilator stress CMR where ventricular volumes and LVEF are critical components to patient care, ventricular functional sequences should be performed prior to vasodilator use or consider the use of aminophylline in the setting of regadenoson. Additionally, heart rate resolution itself is not an effective surrogate for return of ventricular volumes and LVEF to baseline.

Association of tobacco use and cessation with coronary atherosclerosis.

BACKGROUND AND AIMS: The impact of tobacco use and cessation on atherogenesis remains unclear. We aimed to study the association of tobacco use and prior cessation with the presence, extent and severity of atherosclerosis on coronary computed tomographic angiography (CTA). METHODS: We examined 1798 consecutive symptomatic patients without known coronary artery disease (CAD) referred for CTA, stratified by smoking status (never, current [within 30 days], or former [>30 days before CTA]). Plaque severity (none, <50%, ≥50% stenosis), composition (non-calcified [NCP], partially calcified [PCP], or calcified plaque [CP]), and segment involvement score (SIS) were visually graded. Multivariate analysis was performed, adjusting for CAD risk factors and cholesterol lowering medication use. RESULTS: The median age of patients was 50 years [IQR:42-58] (61% male), with 74% never smokers, 12% current smokers, and 14% former smokers (median quit duration = 12 years [IQR:3-26]). Smoking exposure in former versus current smokers was 11 [IQR:5-25] and 10 [IQR:2-20] pack-years, respectively (p = 0.01). Compared to never smokers, current smokers demonstrated an increased odds ratio of all plaque types (adjusted OR: any NCP = 1.55 [95% CI 1.04-2.32], p = 0.03; any PCP = 1.61 [1.10-2.37], p = 0.02; any CP = 1.93 [1.32-2.81], p = 0.001), non-obstructive CAD (aOR = 1.47 [1.04, 2.07], p = 0.03), obstructive CAD (aOR = 1.81 [1.01-3.24], p = 0.047), and SIS > 4 (aOR = 1.60 [1.04-2.46], p = 0.03). Compared to current smoking, prior smoking cessation (≥12 years) was associated with a decreased odds ratio of any NCP (aOR = 0.42 [0.19-0.90], p = 0.03), CP (aOR = 0.43 [0.22-0.84], p = 0.02), and obstructive CAD (aOR = 0.40, [0.15-0.98], p = 0.048). CONCLUSIONS: Current smoking is independently associated with the presence and extent of coronary plaque, and a higher risk of non-obstructive and obstructive CAD compared to never smoking. Prior smoking cessation correlated with improvements in CTA-identified plaque measures.

Rest-Only Myocardial CT Perfusion in Acute Chest Pain.

OBJECTIVES: Cardiac computed tomography perfusion (CTP) using stress testing is an emerging application in the field of cardiac computed tomography. We evaluated patients with acute chest pain (CP) in the emergency department (ED) with evidence of obstructive coronary artery disease (CAD), defined as >70% stenosis on coronary computed tomography angiography (CCTA) and confirmed by invasive coronary angiography (ICA), to evaluate the applicability of resting CTP in the acute CP setting. METHODS: From January to December 2013, 183 low-intermediate risk symptomatic patients with negative cardiac biomarkers and no known CAD underwent a rapid CCTA protocol in the ED. Of these, 4 patients (1.4%) had obstructive CAD (≥70% stenosis) on CCTA confirmed by ICA. All 183 CCTA studies were evaluated retrospectively with CTP software by a transmural perfusion ratio (TPR) method with a superimposed 17-segment model. A TPR value <0.99 was considered abnormal based on previously published data. RESULTS: A total of four patients were included in this pilot analysis. The duration from resolution of CP to performance of CCTA ranged from 1.6 to 5.0 hours. Three patients underwent revascularization, two with percutaneous coronary intervention (PCI) and one with coronary artery bypass grafting. The fourth patient was managed with aggressive medical therapy. Two patients had multivessel obstructive CAD and two patients had single-vessel CAD. The first patient underwent CCTA 5 hours after resolution of CP symptoms. CCTA demonstrated noncalcified obstructive CAD in the mid-LAD and mid-right coronary artery. ICA showed good correlation by quantitative coronary assessment (QCA) in both vessels and the patient underwent PCI. CTP analysis demonstrated perfusion defects in the LAD and right coronary artery territories. The second patient underwent CCTA 1.6 hours after resolution of CP symptoms with findings of obstructive ostial left main CAD. ICA confirmed obstructive left main CAD by QCA and intravascular ultrasound. The patient underwent revascularization with coronary artery bypass grafting. CTP demonstrated perfusion defects in the anterior and lateral wall segments. The third patient was evaluated for CP in the ED with CCTA demonstrating single-vessel CAD 10 hours after resolution of symptoms with findings of a noncalcified obstructive stenosis in the mid-LAD. The patient subsequently underwent ICA demonstrating good correlation to the CCTA findings in the LAD by QCA. CTP analysis revealed perfusion defects in LAD territory. He was successful treated with PCI. The final patient underwent CCTA 5.4 hours following resolution of CP with the finding of an intermediate partially calcified stenosis in the distal LAD. ICA was performed, with fractional flow reserve demonstrating a hemodynamically insignificant distal LAD at 0.86. CTP detected a perfusion defect in the LAD territory. CONCLUSIONS: When positive, rest CTP may have value in the risk stratification of patients presenting to the ED with nontraumatic acute CP.