Estimation of coronary flow reserve by sestamibi imaging in type 2 diabetic patients with normal coronary arteries

Background  We assessed coronary flow reserve (CFR) by sestamibi imaging in patients with type 2 diabetes without coronary artery disease and normal coronary vessels. Methods and Results  Dipyridamole/rest technetium 99m sestamibi imaging was performed in 33 patients with type 2 diabetes without a history of coronary artery disease and normal coronary vessels at angiography and in 12 control subjects. Myocardial blood flow (MBF) was estimated by measuring first-transit counts in the pulmonary artery and myocardial counts from tomographic images. Estimated CFR was expressed as the ratio of stress MBF to rest MBF. Rest MBF and CFR were corrected for rate-pressure product and expressed as normalized MBF and normalized CFR. At rest, estimated MBF and normalized MBF were not different in control subjects versus patients (0.98±0.4 counts·pixel⁻¹·s⁻¹ vs 1.42±0.9 counts·pixel⁻¹·s⁻¹ and 1.14±0.5 counts·pixel⁻¹·s⁻¹ vs 1.61±0.9 counts·pixel⁻¹·s⁻¹, respectively). Conversely, stress MBF was higher in control subjects than in patients (2.34±0.8 counts·pixel⁻¹·s⁻¹ vs 1.55±0.8 counts·pixel⁻¹·s⁻¹, P<.01). Thus estimated CFR was higher in control subjects than in patients (2.40±0.3 vs 1.36±0.8, P<.0001). After correction for the rate-pressure product, normalized CFR was still higher in control subjects than in patients (2.10±0.5 vs 1.28±0.8, P<.001). Conclusions  Sestamibi imaging may detect impaired coronary vascular function in response to dipyridamole in type 2 diabetic patients withou a history of coronary artery disease and with normal coronary arteries.     

胸痛伴正常冠状动脉造影患者超敏C反应蛋白的测定

目的　分析冠状动脉造影正常的典型胸痛患者超敏C反应蛋白 (hs CRP)的变化。方法　选择冠状动脉造影检查正常的胸痛患者 12 3例 ,测定并分析其超敏C反应蛋白的变化。结果　冠状动脉造影正常的胸痛患者中 ,运动试验阳性组hs CRP浓度 [(3.1± 3.2 )mg L]远高于阴性组hs CRP浓度[(1.2± 1.1)mg L ;P <0 .0 0 1) ]。结论　在冠状动脉造影正常的典型胸痛患者中 ,炎症可能参与了胸痛的发生     

心肌桥患者冠状动脉血流储备研究

目的　评估心肌桥对冠状动脉 (冠脉 )血流储备的作用。方法　 2 0 0 0年 9月至 2 0 0 3年 1月 ,13例冠脉造影显示心肌桥患者即刻测定冠脉血流储备 ,与同期 32例冠脉造影正常对照者比较。结果　两组患者一般情况无差异。 13例心肌桥患者临床均有稳定型心绞痛 ;心肌桥均位于左前降支 (中段 11例 ,中远段 2例 ) ,收缩期及舒张期冠脉狭窄分别为 78%± 7%和 15 %± 5 % ,血流储备较对照组显著降低 (2 .0± 0 .3和 3.3± 0 .6 ,P <0 .0 0 1)。结论　心肌桥使冠脉血流储备降低 ,这可能是患者发生心绞痛的原因     

Estimation of coronary flow reserve by Tc-99m sestamibi imaging in patients with coronary artery disease: Comparison with the results of intracoronary Doppler technique

BACKGROUND: This study compared coronary flow reserve (CFR) estimated by technetium 99m sestamibi imaging with the results obtained with intracoronary Doppler in patients with coronary artery disease. Intraobserver and interobserver reproducibility of the radionuclide-estimated CFR was also assessed. METHODS AND RESULTS: Fourteen consecutive patients (mean age, 54 +/- 7 years) with documented coronary artery disease in whom percutaneous coronary intervention was planned underwent dipyridamole (0.74 mg/kg) sestamibi imaging and intracoronary Doppler within 5 days. Myocardial blood flow (MBF) was estimated by measurement of first transit counts in the pulmonary artery and myocardial counts from single photon emission computed tomography images. Estimated CFR was expressed as the ratio of stress MBF to rest MBF. In the study vessels, CFR was 1.36 +/- 0.43 as estimated by sestamibi and 1.39 +/- 0.42 by intracoronary Doppler ( P = .69). A significant relationship between CFR estimated by sestamibi and CFR obtained by intracoronary Doppler was observed ( r = 0.85, P < .001). On Bland-Altman analysis, the mean difference between CFR by sestamibi and by Doppler was 0.03 and the intraclass correlation coefficients for intraobserver and interobserver reproducibility were high (all P < .001) for both global and regional CFR. CONCLUSIONS: This study demonstrates a good agreement between CFR estimated by sestamibi imaging and by intracoronary Doppler results and a lack of intraobserver and interobserver variability of this noninvasive approach.     

Assessment of coronary flow reserve using single photon emission computed tomography with technetium 99m-labeled tracers

The quantitative assessment of coronary flow reserve (CFR) may be useful for the functional evaluation of coronary artery disease (CAD), allowing judgment of its severity, tracking of disease progression, and evaluation of the anti-ischemic efficacy of therapeutic strategies. Invasive techniques, such as intracoronary Doppler ultrasound and the pressure-derived method, which directly assess CFR velocity and fractional flow reserve, have been used for the evaluation of the physiologic significance of coronary lesions. Considerable progress has been made in the improvement of technologies directed toward the noninvasive quantification of myocardial blood flow and CFR. Positron emission tomography has emerged as an accurate technique to quantify CFR. The absolute measurements obtained with this noninvasive approach have been widely validated. Nevertheless, it has not been applied to routine studies because of its high cost and complexity. On the other hand, technetium 99m-labeled tracers have been largely used for the evaluation of myocardial perfusion with single photon emission computed tomography (SPECT) imaging in patients with suspected or known CAD. Recently, attempts to estimate CFR with SPECT tracers have been made to obtain, with noninvasive methods, data for quantitative functional assessment of CAD. This review analyzes the relative merit and limitations of CFR measurements by cardiac SPECT imaging with Tc-99m-labeled tracers and describes the potential clinical applications of this technique.     

基于CCTA对胸痛病人高危斑块成分及血流动力学特征的研究

目的 基于冠状动脉CT血管成像（CCTA）研究伴高危斑块的胸痛病人其斑块成分特征及血流动力学特征。方法 回顾性纳入行CCTA且于2个月内行有创冠状动脉造影检查的43例冠心病病人,男30例,女13例,平均年龄（60.8±8.7）岁。依据病人是否存在高危斑块及胸痛将病人分为2组,组1同时存在胸痛和至少1个高危斑块特征（23例）,组2仅有胸痛或高危斑块特征任意一项（20例）。测量斑块成分特征参数[斑块总体积、钙化斑块体积、纤维斑块体积、脂质斑块体积占比（脂质斑块%）、脂质斑块面积、最小管腔面积、偏心指数]和血流动力学特征参数[基于CCTA的血流储备分数（FFR_CT）,斑块近、远端FFR_CT差值（△FFR_CT）]。采用Mann-Whitney U检验或独立样本t检验比较2组间参数的差异。利用约登指数计算斑块成分特征及血流动力学特征判断高危斑块合并胸痛的临界值,采用受试者操作特征（ROC）曲线分析计算其临界值的敏感度、特异度以及曲线下面积（AUC）。结果 组1的脂质斑块%、脂质斑块面积均高于组2（均P<0.05）,FFR_CT值低于组2（P<0.05）,2组间其他斑块成分特征参数及△FFR_CT差异均无统计学意义（均P>0.05）。分析脂质斑块%、脂质斑块面积及FFR_CT 特征参数的诊断能力,FFR_CT的临界值为0.82时的敏感度最高（61%）、特异度最低（85%）,AUC最高（0.80）。结论 采用CCTA分析高危斑块中脂质斑块成分特征并进行FFR_CT测量,可作为评估高危斑块合并胸痛病人的有效辅助手段,为临床治疗决策提供依据。     

PET心肌灌注显像测定心肌血流量及冠状动脉血流储备的研究进展

PET心肌灌注显像可绝对定量测定局部心肌血流量(MBF)和冠状动脉血流储备(CFR).由于显像剂半衰期短,允许在短时间内重复进行PET心肌灌注显像,获得静息态、冷加压试验和药物负荷试验等不同状态下的MBF,进而评价冠状动脉血管内皮依赖性和非依赖性的CFR功能.在早期诊断冠心病,准确诊断冠状动脉多支病变,评价微血管病变,早期检测冠状动脉内皮细胞功能异常及CFR功能的异常,估测预后,帮助临床治疗方案的制定以及检测疗效等方面,PET心肌灌注显像有重要的临床价值.该文将介绍PET心肌灌注显像相关知识及其在心血管领域的主要应用.     

冠状动脉血流储备分数、心肌血流储备和微循环阻力指数在冠心病患者中的临床应用价值

通过对冠状动脉性心脏病（CAD）进行准确、有效地冠状动脉生理学功能状况评估,有利于客观评价CAD的危险程度、选择合适的治疗策略以改善患者预后。目前临床上评价冠状动脉生理学功能的常用的指标包括血流储备分数（FFR）、心肌血流储备（MFR）和微循环阻力指数（IMR）,可通过无创或有创的方法获得。笔者就FFR、MFR和IMR在CAD患者中的临床应用价值作一综述。     

Myocardial flow reserve is influenced by both coronary artery stenosis severity and coronary risk factors in patients with suspected coronary artery disease

Purpose Myocardial flow reserve (MFR) measurement has an important role in assessing the functional severity of coronary artery stenosis. However, a discrepancy between the anatomical severity of coronary artery stenosis and MFR is often observed. Such a discrepancy may be explained by coronary risk factors. In this study, we aimed to investigate the influence of coronary artery stenosis severity and risk factors on MFR.Methods Seventy-four patients suspected to have coronary artery disease and seven age-matched healthy volunteers were enrolled. Myocardial blood flow (MBF) and MFR were measured using ¹⁵O-labelled water PET. Regional MFR was calculated in regions with significant coronary artery stenosis (stenotic regions) and in regions without significant stenosis (remote regions). The contributions of coronary artery stenosis severity and coronary risk factors were assessed using univariate and multivariate analyses.Results In stenotic regions, MFR correlated inversely with coronary artery stenosis severity (r=−0.50, p<0.01). Univariate analysis did not show any significant difference in MFR between the patients with and the patients without each risk factor. In remote regions, however, MFR was significantly decreased in the diabetes and smoking groups (each p<0.05). By multivariate analysis, diabetes and smoking were independent predictors of MFR (each p<0.05). In the group with more than one risk factor, MFR was significantly lower (2.78±0.79) than in the other group (3.40±1.22, p<0.05).Conclusion MFR is influenced not only by coronary stenosis severity but also by coronary risk factors. In particular, the influence of risk factors should be considered in regions without severe coronary stenosis.This study received no financial sponsorship.     

地尔硫(艹卓)对冠脉内支架术后胸痛患者的疗效

目的评价地尔硫对冠脉内支架术后胸痛患者的近期疗效和远期再狭窄的影响。方法冠脉内支架术后胸痛患者251例,其中地尔硫治疗189例(75.3%),其余62例(24.7%)未接受地尔硫治疗。比较两组随访期严重心脏事件(死亡、心肌梗死和重复靶血管再通治疗)和再狭窄率。结果在中位数128d的随访期内,严重心脏事件在地尔硫组为4.8%,非地尔硫组为12.9%(P=0.039)。42.6%患者于1年内行血管造影随访,地尔硫组的再狭窄发生率显著降低(11.5%和29.2%,P=0.05)。结论地尔硫对冠脉内支架术后胸痛患者有一定疗效。     

Comparison of Tc-99m sestamibi SPECT with fractional flow reserve in patients with intermediate coronary artery stenoses

BACKGROUND: Myocardial single photon emission computed tomography (SPECT) is an established noninvasive method for the assessment of the functional significance of coronary artery stenoses. Intracoronary pressure measurements to determine fractional flow reserve (FFR) are increasingly performed during coronary angiography whenever an immediate decision regarding possible intervention is required. We hypothesized that the regional summed difference score (SDSr), reflecting reversible perfusion defects in the myocardial supply area of the FFR target vessel, would be the best predictor of an abnormal FFR in patients without prior myocardial infarction. Otherwise, a regional summed stress score (SSSr) should be the best predictor of an abnormal FFR in patients with prior myocardial infarction for different patient subgroups with coronary artery disease. METHODS AND RESULTS: In this study 50 patients (mean age, 65 +/- 9.1 years; 18 women) with coronary artery disease and a 50% to 75% coronary stenosis (target vessel) were prospectively investigated. Dobutamine myocardial SPECT was performed as a single-day stress/rest protocol by use of technetium 99m sestamibi. For image interpretation, semiquantitative analysis was conducted by calculating SSSr and SDSr. Within 8 (+/-14.9) days, coronary angiography was performed and FFR was calculated by use of a pressure wire (normal FFR, > or = 0.75). The mean FFR of all patients was 0.78 +/- 0.14. Of 50 patients, 17 had an FFR lower than 0.75 in the target vessel. Receiver operating characteristic analysis identified an SDSr of 1 or greater and an SSSr of 3 or greater as the best threshold values for predicting ischemic FFR. Sensitivity, specificity, and negative and positive predictive values of SDSr and SSSr for the detection of FFR values lower than 0.75 in the target vessel were 80%, 76%, 53%, and 92%, respectively, and 70%, 93%, 78%, and 90%, respectively, in patients without prior myocardial infarction and 57%, 50%, 67%, and 40%, respectively, and 100%, 50%, 78%, and 100%, respectively, in patients with prior myocardial infarction. Weak correlation was found between the single values of FFR with both SDSr and SSSr for the different patient subgroups. CONCLUSION: Among the dobutamine myocardial scintigraphy variables studied, SDSr was the best predictor of an abnormal FFR (cutoff value of 0.75) in patients without prior myocardial infarction. As assumed, SSSr was the best predictor of an abnormal FFR in patients with prior myocardial infarction in the target region.     

Clinical assessment of chest pain and guidelines for imaging

For many emergency facilities, risk assessment of patients with diffuse chest pain still poses a major challenge. In their currently valid recommendations, the international cardiological societies have defined a standardized assessment of the prognostically relevant cardiac risk criteria. Here the classic sequence of basic cardiac diagnostics including case history (cardiac risk factors), physical examination (haemodynamic and respiratory vital parameters), ECG (ST segment analysis) and laboratory risk markers (troponin levels) is paramount. The focus is, on the one hand, on timely indication for percutaneous catheterization, especially in patients at high cardiac risk with or without ST-segment elevation in the ECG, and, on the other hand, on the possibility of safely discharging patients with intermediate or low cardiac risk after non-invasive exclusion of a coronary syndrome. For patients in the intermediate or low risk group, physical or pharmacological stress testing in combination with scintigraphy, echocardiography or magnetic resonance imaging is recommended in addition to basic diagnostics. Moreover, the importance of non-invasive coronary imaging, primarily cardiac CT angiography (CCTA), is increasing. Current data show that in intermediate or low risk patients this method is suitable to reliably rule out coronary heart disease. In addition, attention is paid to the major differential diagnoses of acute coronary syndrome, particularly pulmonary embolism and aortic dissection. Here the diagnostic method of choice is thoracic CT, possibly also in combination with CCTA aiming at a triple rule-out.     

Correlation between flow-sensitive alternating inversion recovery perfusion imaging with different inversion times and cerebral flow reserve evaluated by single-photon-emission computed tomography

The purpose of this study was to evaluate the effect of different inversion times (TIs) on flow-sensitive alternating inversion recovery (FAIR) perfusion imaging and compare them with the cerebral blood flow reserve evaluated by acetazolamide challenge using single-photon-emission computed tomography (SPECT). The subjects were nine patients with unilateral obstruction of the internal carotid artery. The signal ratio (SR16/8) of two images with different TIs (1,600 ms and 800 ms) was calculated, and the cerebral blood flow reserve (CFR) was evaluated by the increase in the ratio of cerebral perfusion after administration of acetazolamide in the SPECT study. A reversed linear correlation ( r =0.75) was found between SR and CFR, indicating that differences of FAIR images with changes of TI will be affected by cerebral flow reserve.     

Differences in diagnostic evaluation and clinical outcomes in the care of patients with chest pain based on admitting service: The benefits of a dedicated chest pain unit

Background  Chest pain is one of the most common complaints of patients presenting at emergency departments. However, the most appropriate diagnostic evaluation for patients with chest pain but without acute coronary syndrome remains controversial, and differs greatly among institutions and physicians. At our institution, patients with chest pain can be admitted to an internist-run hospitalist service, a private attending service, or a cardiologist-run Chest Pain Unit. The goal of the present study was to compare the management and outcomes of patients admitted with chest pain based on admitting service. Methods  The charts of 750 patients (250 consecutive patients per service) with a discharge diagnosis of chest pain were studied retrospectively. Results  Patients admitted to the Chest Pain Unit were younger and had a lower prevalence of known coronary artery disease, hypertension, or diabetes, but a similar prevalence of other risk factors compared with the other groups. Sixty percent of the patients in the Chest Pain Unit underwent stress myocardial perfusion imaging as their primary diagnostic modality (vs 22% and 12% of patients in the hospitalist and private services, respectively; P<.001). In contrast, 35% of the patients admitted to the hospitalist service underwent rest echocardiography (vs 8% and 17% of patients in the Chest Pain Unit and private services, respectively; P<.001). Finally, 47% of the patients in the private service underwent coronary angiography as their primary diagnostic modality (vs 6% and 10% of patients in the Chest Pain Unit and hospitalist services, respectively; P<.001). The length of stay was shortest for patients in the Chest Pain Unit (1.4±1.2 days vs 3.9±3.4 days and 3.5±3.6 days in the hospitalist and private services, respectively; P<.001), even when corrected for patient age and number of risk factors. Readmission within 6 months was lowest for patients in the Chest Pain Unit (4.4% vs 17.6% and 15.2% in the hospitalist and private services, respectively; P<.001). Conclusions  The results of this study demonstrate that a highly protocolized chest pain unit, using myocardial perfusion imaging as primary diagnostic modality, results in a decreased length of stay and readmission rate.     

Reduced myocardial flow reserve in anatomically normal coronary arteries due to elevated baseline myocardial blood flow in men with old myocardial infarction

BACKGROUND: Decreased myocardial flow reserve (MFR) in angiographically normal coronary arteries in patients with old myocardial infarction (OMI) has been reported. METHODS AND RESULTS: To clarify factors for the reduced MFR in OMI and to compare them with those in angina pectoris (AP), baseline myocardial blood flow (MBF) and MBF during dipyridamole administration were measured with nitrogen 13 ammonia positron emission tomography, after which MFR was calculated for 13 men with AP, 18 men with OMI, and 15 age-matched male control subjects. MFR was compared among the 3 groups in segments perfused by nonstenotic arteries. Baseline MBF in patients with OMI was significantly higher than that in patients with AP and control subjects. MBF during dipyridamole administration in patients with OMI was significantly lower than that in control subjects. MFR in patients with AP was 2.50 +/- 0.91 (P <.05 vs control subjects [3.47 +/- 1.25]), and that in patients with OMI was 1.83 +/- 0.61 (P <.01 vs control and AP groups). Ejection fraction (EF) in patients with OMI was significantly decreased compared with that in patients with AP. However, there was no significant difference in the mean score of the individual risk factors between patients with AP and those with OMI. In the pooled data with AP and OMI, baseline MBF and EF were significant for the reduced MFR. CONCLUSIONS: MFR and EF in patients with OMI were significantly decreased compared with those in patients with AP. Increased baseline MBF and decreased EF were significant factors for the reduced MFR in patients with AP and OMI.     

基于深度学习的FFRCT在可疑冠心病病人中的应用

目的 探讨基于深度学习的CT血流储备分数（FFR_CT）在可疑冠心病病人中应用的可行性,分析缺血性病变（FFR_CT≤0.80）的预测因素及对治疗决策的影响。方法 回顾性纳入因疑似冠心病行冠状动脉CT血管成像（CCTA）的病人292例,其中男187例,女105例,平均年龄（65.8±10.3）岁。利用CCTA影像将狭窄程度分为轻度 （≥25%且<50%）、中度（≥50%且<70%）和重度（≥70%且<99%）。采用基于深度学习的FFR_CT软件对病人的CCTA数据进行测量。根据FFR_CT数值范围将病人分为阳性组（FFR_CT≤0.80,102例）和阴性组（FFR_CT>0.80,190例）。2组病人的一般资料、CCTA上的血管特征及血运重建,以及基于FFR_CT与CCTA制定的治疗策略的比较采用Mann-Whitney U 检验、t检验及卡方检验。采用Logistic回归分析FFR_CT≤0.80的独立预测因素。结果 阳性组病人的年龄更大,男性更多,高血压、糖尿病和吸烟的比例均高于阴性组（均P<0.05）。阳性组较阴性组病人更多的表现为中重度狭窄（分别为80.4%和28.4%）,更多的病人行血运重建术（分别为56.8%和11.1%）,均P<0.05。74例病人（25.3%）基于FFR_CT的结果治疗决策发生改变。多因素Logsitic回归分析显示,高血压（OR=2.245）、糖尿病（OR=2.238）及中重度狭窄（OR=8.837）是FFR_CT≤0.80的独立预测因素（均P<0.05）。结论 基于深度学习的FFR_CT技术在可疑冠心病病人中的应用是可行的,高血压、糖尿病及中重度狭窄是FFR_CT≤0.80的独立预测因素,FFR_CT可能影响病人的治疗决策。     

Diagnostic image quality of a comprehensive high-pitch dual-spiral cardiothoracic CT protocol in patients with undifferentiated acute chest pain

Objective

To evaluate diagnostic image quality of high-pitch dual source comprehensive cardiothoracic CT protocol in patients presenting with acute undifferentiated chest pain.

Materials and methods

Consecutive symptomatic subjects (n = 51) with undifferentiated acute chest pain underwent ECG-synchronized high-pitch dual-spiral chest CT angiography (Definition Flash, Siemens Medical Solutions, 2 × 100 kVp or 2 × 120 kV if BMI > 30, collimation: 128 × 0.6 mm, pitch: 3.2). Independent investigators determined the image quality of each cardiac and pulmonary vessel segment, measured contrast-to-noise-ratio (CNR), and determined radiation exposure. In addition, the prevalence of CT findings (pulmonary embolism (PE), aortic dissection (AD) and significant coronary stenosis (≥50%)) was determined. Univariate and multivariate analysis were performed to determine the subpopulation with highest diagnostic quality.

Results

Among 51 subjects (66% male, average age: 63 ± 15.8), the prevalence of positive CT findings was moderate (overall: 11.7%). Overall, image quality of the pulmonary, aortic and coronary vasculature was good (1.26 ± 0.43 and CNR: 2.52) with an average radiation dose of 3.82 mSv and 3.2% of segments rated non-evaluable. The image quality was lowest in the coronary arteries (p = 0.02), depending on the heart rate (r = 0.52, p < 0.001). In subjects with a heart rate of ≤65 bpm (n = 30) subjective image quality and CNR of the coronary arteries were higher (1.6 ± 0.5 vs. 2.1 ± 0.5, p = 0.03 and 1.21 ± 0.3 vs. 1.02 ± 0.3, p = 0.05) with only 1.5% segments classified as non-evaluable.

Conclusion

High-pitch dual-spiral comprehensive cardiothoracic CT provides low radiation exposure with excellent image quality at heart rates ≤65 bpm. In subjects with higher heart rates, image quality of the aortic and pulmonary vasculature remains excellent, while the assessment of the coronary arteries degrades substantially.     

Acute ischemic dysfunction alters coronary flow reserve in remote nonischemic regions: Potential mechanical etiology identified in an acute canine model

BACKGROUND: Impaired coronary flow reserve (CFR) has been observed in remote nonischemic regions in patients after myocardial infarction. The mechanism for this impairment in remote nonischemic CFR remains undefined. This study evaluates the effect of progressive regional ischemic dysfunction on function in remote nonischemic regions, and the effect of the extent of dysfunction on remote nonischemic coronary flow and CFR. METHODS: In an anesthetized open-chest canine model (n = 7) of acute progressive distal and proximal left anterior descending (LAD) coronary artery occlusion, regional myocardial thickening fraction and coronary flow and CFR were measured with Doppler probes. CFR was assessed by an intracoronary injection of 36 microg of adenosine. Changes in thickening fraction and CFR were evaluated for isovolumic, ejection, and diastolic phases. Changes in resting regional flow were also assessed using radiolabeled microspheres. The extent of the ischemic area was defined as regions of myocardium with endocardial microsphere blood flow less than 0.3 mL/min/g. RESULTS: The ischemic area increased from 12% +/- 1% of left ventricle with distal occlusion to 30% +/- 2% of left ventricle with proximal occlusion (P < .001). The LAD thickening fraction decreased significantly from baseline (18% +/- 1%) to distal (-8% +/- 1%,) and proximal (-4% +/- 1%) occlusion (P < .001 for distal and proximal vs baseline). Isovolumic bulging in the LAD region was associated with a progressive increase in thickening fraction in the remote nonischemic left circumflex (LCX) artery region (baseline 12% +/- 1%; distal occlusion 15% +/- 2%, P = .014 vs baseline; proximal occlusion 17% +/- 2%, P = .02 vs baseline). Most of the increase in remote thickening fraction occurred during the isovolumic phase. There was no significant change in resting flow in remote nonischemic LCX regions or global hemodynamic parameters. However, there was a progressive decrease in remote nonischemic CFR (baseline 2.44 +/- 0.3), distal occlusion (2.19 +/- 0.31; P = .055 vs baseline), and proximal occlusion (1.79 +/- 0.22; P = 0.004 vs baseline, and P = .012 vs distal occlusion). A progressive decrease in CFR was noted in each phase of the cardiac cycle. CONCLUSION: In a canine model of acute progressive distal and proximal coronary occlusion, we observed a progressive decrease in CFR in remote nonischemic regions concurrent with an increase in the extent of ischemia. The decrease in remote nonischemic CFR was associated with ischemia-induced isovolumic bulging, which placed the remote regions at a mechanical disadvantage. These observations suggest a potential mechanical etiology for the observed impairment in remote CFR. Alterations in remote nonischemic CFR during acute ischemia may have important clinical implications for perfusion scintigraphy.