Prognostic value of stress-gated 99m-technetium SPECT myocardial perfusion imaging: risk stratification of patients with multivessel coronary artery disease and prior coronary revascularization.

BACKGROUND: This study assessed the prognostic value of stress-gated 99mTc-sestamibi myocardial perfusion SPECT (MPS) in patients with multivessel coronary artery disease (CAD) and prior revascularization according to the presence and severity of ischemia. METHODS AND RESULTS: We studied the outcome of 472 patients with multivessel CAD and prior revascularization (coronary angioplasty, 290 patients; bypass surgery, 182 patients), who underwent exercise or dipyridamole 99mTc-sestamibi MPS for evaluation of ischemia. Visual scoring of perfusion images used 20 segments and a 5-point scale. Gated post-stress EF was automatically calculated. Endpoints included hard events: cardiac death (CD) and nonfatal myocardial infarction (MI). During a mean follow-up of 3.0 ± 1.0 years, 37 hard events occurred, including CD in 15 (3%) and MI in 22 (5%) patients. In a risk-adjusted multivariable Cox model, a history of prior MI, diabetes, abnormal MPS, moderate-to-severe ischemia, and post-stress EF <35% were important predictors of cardiac events. Four-year risk-adjusted survival was 97.9% for normal MPS, 87.3% for abnormal MPS with ischemia, and 82.1% for moderate-to-severe ischemia. CONCLUSIONS: Among patients with previous coronary revascularization, stress-gated 99mTc-sestamibi MPS provides prognostic information for the prediction of cardiac events. A normal perfusion scan confers an excellent prognosis and an exceedingly low hard event rate (<1%/year). The presence of moderate-to-severe ischemia or a post-stress EF <35% identifies patients at highest risk of subsequent cardiac events.

Accuracy of dual-source CT to identify significant coronary artery disease in patients with uncontrolled hypertension presenting with chest pain: comparison with coronary angiography.

It has been previously reported that the sensitivity and specificity of multislice CT for detecting significant CAD (coronary artery disease) is high. Chest pain is a common presentation in patients with uncontrolled hypertension. We investigated the sensitivity and specificity of dual-source CT to detect and rule out significant CAD in patients presenting with uncontrolled hypertension accompanied by chest pain. 260 consecutive patients presenting with acute chest pain in the context of stage 2 hypertension (systolic pressure ≥160 and/or diastolic pressure ≥100) were enrolled in the study. After admission, control of blood pressure and risk stratification, 82 patients were excluded due to renal insufficiency, prior coronary revascularisation or refused participation in the study. 90 further patients with low pre-test probability of CAD were also excluded. 88 remaining patients were subjected to CT coronary angiography using dual-source CT (Definition, Siemens Medical Solutions, Forchheim, Germany) within 24 h before invasive coronary angiography. A contrast-enhanced volume dataset was acquired (120 kV, 400 mAs/rot, collimation 2 × 64 × 0.6 mm, retrospective ECG gating). Data sets were evaluated concerning the presence or absence of significant coronary stenoses and validated against invasive coronary angiography. A significant stenosis was assumed if the diameter reduction was ≥50%. 88 patients (mean age 66 ± 11 years, mean heart rate 61 ± 9 bpm) were evaluated regarding the presence or absence of significant CAD (at least one stenosis ≥50% diameter reduction). Mean systolic blood pressure on presentation was 203 ± 20 mmHg and mean diastolic blood pressure was 103 ± 13 mmHg. On a per patient basis, the sensitivity and specificity for dual-source CT to detect significant CAD in vessels >1.5 mm diameter was 100% (36/36, 95% CI 90-100) and 90% (47/52, 95% CI 79-97), respectively with a negative predictive value (NPV) of 100% (47/47, 95% CI 92-100) and a positive predictive value (PPV) of 88% (36/41, 95% CI 74-96). On a per artery basis, 352 vessels were evaluated (left main, left anterior descending, left circumflex and right coronary artery in 88 patients, 12 vessels could not be assessed due to either motion artefacts or heavy calcification and were considered positive for stenoses) with a sensitivity of 84% (54/64, 95% CI 72-95) and specificity of 94% (272/288, 95% CI 88-100); NPV was 96% (272/282, 95% CI 90-100) and PPV was 77% (54/70, 95% CI 62-91). Our study demonstrates high sensitivity, specificity and negative predictive value of dual-source CT to detect significant CAD in patients presenting with uncontrolled hypertension accompanied by chest pain. Dual-source CT angiography may be useful to safely rule out coronary artery stenoses and avoid invasive angiograms in these patients.

Coronary vessel and luminal area measurement using dual-source computed tomography in comparison with intravascular ultrasound: effect of window settings on measurement accuracy.

BACKGROUND: Image display settings (window and level) have a substantial impact on measurements of coronary artery and plaque dimensions in computed tomography (CT), and their influence on measurement accuracy has not been systematically evaluated. We analyzed the influence of window width/level settings on the accuracy for determining cross-sectional lumen and outer vessel diameters in contrast-enhanced CT angiography compared with intravascular ultrasound (IVUS). METHODS: We evaluated the data sets of 35 patients. Coronary CT angiography was performed as part of a research protocol before invasive coronary angiography. A contrast-enhanced volume data set was acquired using a dual-source CT (DSCT) scanner (Siemens Healthcare, Forchheim, Germany). Intravascular ultrasound was performed using a 40-MHz IVUS catheter (Atlantis, Boston Scientific Corporation, Natick, Mass) and motorized pullback at 0.5 mm/s. One hundred exactly corresponding sites within the coronary artery system were identified in both DSCT and IVUS using bifurcation points as fiducial markers. In DSCT data sets, multiplanar reconstructions (0.75-mm slice thickness) were rendered orthogonally to the centerline of the coronary artery at each of the 100 sites. Computed tomographic images were displayed using 4 previously published settings (700/200, 700/140, and 500/150 Hounsfield units [HU], and 1 HU/65% of the mean luminal intensity [HU] and 155%/65% of the mean luminal intensity [HU] for window width/level) as well as with a visually adjusted setting for subjectively optimal lumen and outer vessel area measurement. Coronary lumen and cross-sectional vessel areas were manually traced using all 5 display settings and compared with IVUS measurements. RESULTS: Concerning cross-sectional vessel area measurements, correlation was close and significant compared with IVUS using all settings (r ≥ 0.93, P = 0.01 for all settings). Bland-Altman analysis revealed a good agreement between both modalities with a systematic bias toward overestimation in CT. Least bias was demonstrated using the setting 155%/65% of the mean luminal intensity for window width/level, with a mean (SD) difference of 0.2 (1.73) mm2. For the measurement of the luminal area, the window setting using a width of 1 HU and a level of 65% of the mean luminal intensity showed the lowest correlation to IVUS (r = 0.85), with a systematic bias toward underestimation of the lumen in CT. Bland-Altman analysis revealed a moderate agreement with a mean (SD) difference of -2.1 (1.6) mm2. For all other settings, a very close correlation was observed (r > 0.9, P = 0.01), and Bland-Altman analysis revealed a slight trend toward lumen underestimation in CT, yet with a good agreement. The least bias was demonstrated using the setting 700/200 HU for window width/level with a mean (SD) difference of -0.1 (0.9) mm2. CONCLUSION: Previously published window settings and visually adjusted window setting correlate very well with IVUS measurements regarding coronary artery cross-sectional and luminal area, with a better agreement for luminal area measurements. A systematic bias toward overestimation of vessel area in CT was observed as well as a slight trend toward lumen underestimation. This bias was least for vessel area measurement using 155%/65% of the mean luminal intensity (HU) for window width/level, whereas for luminal area measurement, the setting 700/200 HU for window width/level yielded the least bias.

Automated three-dimensional quantification of noncalcified coronary plaque from coronary CT angiography: comparison with intravascular US.

PURPOSE: To determine the accuracy of a previously developed automated algorithm (AUTOPLAQ [APQ]) for rapid volumetric quantification of noncalcified and calcified plaque from coronary computed tomographic (CT) angiography in comparison with intravascular ultrasonography (US). MATERIALS AND METHODS: This study was approved by the institutional review board and was HIPAA compliant; all patients provided written informed consent. APQ combines derived scan-specific attenuation threshold levels for lumen, plaque, and knowledge-based segmentation of coronary arteries for quantification of plaque components. APQ was validated with retrospective analysis of 22 coronary atherosclerotic plaques in 20 patients imaged with coronary CT angiography and intravascular US within 2 days of each other. Coronary CT angiographic data were acquired by using dual-source CT. For each patient, well-defined plaques without calcifications were selected, and plaque volume was measured with APQ and manual tracing at CT and with intravascular US. Measurements were compared with paired t test, correlation, and Bland-Altman analysis. RESULTS: There was excellent correlation between noncalcified plaque volumes quantified with APQ and intravascular US (r = 0.94, P < .001), with no significant differences (P = .08). Mean plaque volume with intravascular US was 105.9 mm³ ± 83.5 (standard deviation) and with APQ was 116.6 mm³ ± 80.1. Mean plaque volume with manual tracing from CT was 100.8 mm³ ± 81.7 and with APQ was 116.6 mm³ ± 80.1, with excellent correlation (r = 0.92, P < .001) and no significant differences (P = .23). CONCLUSION: Automated scan-specific threshold level-based quantification of plaque components from coronary CT angiography allows rapid, accurate measurement of noncalcified plaque volumes, compared with intravascular US, and requires a fraction of the time needed for manual analysis.

Accuracy of dual-source computed tomography to identify significant coronary artery disease in patients with atrial fibrillation: comparison with coronary angiography.

AIMS: 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. METHODS AND RESULTS: One hundred and ten consecutive patients with AF who were admitted for a first diagnostic coronary angiogram were screened for participation. Out of these, 50 patients were excluded either due to renal insufficiency, inability to maintain an adequate breath hold or due to rapid AF non-responsive to ß-blocker therapy (heart rate > 100 b.p.m.). Sixty remaining patients (mean age 71 ± 7 years) were included and subjected to CT angiography using DSCT within 24 h before invasive coronary angiography. A contrast-enhanced volume data set was acquired (330 ms gantry rotation, collimation 2 × 64 × 0.6 mm, retrospective electrocardiogram gating). Data sets were evaluated concerning the presence or absence of significant coronary stenoses and validated against invasive coronary angiography. A significant stenosis was assumed if the diameter reduction was ≥50%. Mean heart rate during CT was 70 ± 15 b.p.m. (range 32-107 b.p.m.). On a per-patient basis, the sensitivity and specificity for DSCT to detect significant coronary stenoses in vessels >1.5 mm diameter was 100% [14/14, 95% confidence interval (CI) 77-100] and 85% (39/46, 95% CI 71-94), respectively, with a negative predictive value (NPV) of 100% (39/39, 95% CI 91-100) and a positive predictive value (PPV) of 67% (14/21, 95% CI 43-85). On a per-artery basis, 240 vessels were evaluated (left main, left anterior descending, left circumflex, and right coronary artery in 60 patients, with 3 non-assessable vessels due to either severe calcification or motion artefacts which were considered positive for stenoses) with a sensitivity of 95% (21/22, 95% CI 77-100) and specificity of 94% (204/218, 95% CI 89-97); NPV was 99% (204/205, 95% CI 96-100), and PPV was 60% (21/35, 95% CI 38-80). CONCLUSION: Our study demonstrates high sensitivity, specificity, and NPV of DSCT to detect significant CAD in selected patients with rate controlled AF.

Characterization of culprit lesions in acute coronary syndromes using coronary dual-source CT angiography.

OBJECTIVE: We analyzed typical morphological features of coronary atherosclerotic plaques in acute coronary syndromes (ACS) using contrast-enhanced coronary Dual-Source CT angiography (CTA) in comparison to stable coronary lesions. PATIENTS AND METHODS: Fifty-five patients with ACS and 55 controls with stable angina pectoris (SAP) with similar atherosclerotic risk profile were studied. CT angiography was performed using a Dual-Source CT scanner (330 ms rotation, 2 x 64 x 0.6mm collimation, 60-80 mL contrast agent i.v. at 6 mL/s) before invasive catheterization. We analyzed plaque volume (mm(3)), mean and minimal CT density (HU), remodeling index, plaque type (calcified/non-calcified/mixed) and presence of "spotty" calcifications as well as presence of contrast rims. RESULTS: In patients with ACS and SAP, 28 and 10 lesions showed both calcified and non-calcified components, but in a greater proportion of non-calcified material, 6 and 23 lesions showed a greater proportion of calcified material and 21 and 8 lesions were completely non-calcified, respectively. None of the culprit plaques in ACS and 14 of the lesions in SAP were completely calcified. A "spotty" pattern of calcification within the plaque and a central filling defect surrounded by a rim of contrast were present in 11 and 14 of 55 ACS cases, but never in SAP lesions. For culprit lesions in ACS and for lesions in patients with SAP, mean plaque volumes were 192.8 + or - 114.9 mm(3) and 103.8+/-51.8 mm(3) (p=0.001), mean and minimal CT densities were 85.6 + or - 45.1HU and 47.2 + or - 33.7 HU versus 143.8 + or - 104.1 HU and 95.9 + or - 84.0 HU (p<0.01) and mean remodeling indices were 1.6 + or - 0.4 and 0.97 + or - 0.17 (p<0.001), respectively. CONCLUSION: Plaques of culprit lesions in ACS show specific morphologic characteristics in non-invasive coronary CT angiography. As compared to stable lesions, culprit lesions in ACS display greater proportion of non-calcified material and presence of "spotty" calcifications/contrast rims as well as larger plaque volumes, lower CT attenuation and higher remodeling indices.

Prevalence of first-pass myocardial perfusion defects detected by contrast-enhanced dual-source CT in patients with non-ST segment elevation acute coronary syndromes.

OBJECTIVE: To investigate the prevalence and diagnostic value of first-pass myocardial perfusion defects (PD) visualised by contrast-enhanced multidetector computed tomography (MDCT) in patients admitted for a first acute coronary syndrome (ACS). METHODS: Thirty-eight patients with non-ST segment elevation myocardial infarction (NSTEMI) or unstable angina (UA) and scheduled for percutaneous coronary intervention underwent dual-source CT immediately before catheterisation. CT images were analysed for the presence of any PD by using a 17-segment model. Results were compared with peak cardiac troponin-I (cTnI) and angiography findings. RESULTS: PD were seen in 21 of the 24 patients with NSTEMI (median peak cTnI level 7.07 ng/mL; range 0.72-37.07 ng/mL) and in 2 of 14 patients with UA. PD corresponded with the territory of the infarct-related artery in 20 out of 22 patients. In a patient-based analysis, sensitivity, specificity, negative and positive predictive values of any PD for predicting NSTEMI were 88%, 86%, 80% and 91%. Per culprit artery, the respective values were 86%, 75%, 80% and 83%. CONCLUSION: In patients with non-ST segment elevation ACS, first-pass myocardial PD in contrast-enhanced MDCT correlate closely with the presence of myocardial necrosis, as determined by increases in cTnI levels.

Quantification of non-calcified coronary atherosclerotic plaques with dual-source computed tomography: comparison with intravascular ultrasound.

BACKGROUND: The quantification of non-calcified coronary plaques using multidetector computed tomography has not been extensively investigated. OBJECTIVE: To evaluate the ability of dual-source computed tomography (DSCT) to quantify non-calcified plaque volumes using intravascular ultrasound (IVUS) as the standard of reference. METHODS: The datasets of 70 patients with suspected or known coronary artery disease who underwent DSCT (330 ms gantry rotation, 2 x 64 x 0.6 mm collimation, 60-90 ml contrast agent) were analysed before invasive coronary angiography, with IVUS performed as part of the diagnostic procedure. 100 individual non-calcified coronary atherosclerotic plaques (one to three plaques per patient) with suitable fiducial markers were matched and selected for plaque volume measurements using manual segmentation. Only DSCT datasets with good or excellent image quality were considered for analysis. RESULTS: Intra and interobserver variability for plaque volume measurements by DSCT were 6+/-5% and 11+/-7%, respectively. Mean total plaque volume by DSCT was 89+/-66 mm(3) (range 14-400 mm(3)). Mean total plaque volume by IVUS was 90+/-73 mm(3) (range 16-409 mm(3)). The mean difference between DSCT and IVUS was 1+/-34 mm(3) (range -131-85 mm(3)). Despite the good correlation for plaque volume measurements (r=0.89, p<0.001), agreement between the two methods was only modest (Bland-Altman limits of agreement -67 to +65 mm(3)). CONCLUSIONS ; Non-calcified plaque volumes as determined by DSCT yielded good correlation but only modest agreement in comparison with IVUS.

Coronary computed tomography angiography with a consistent dose below 1 mSv using prospectively electrocardiogram-triggered high-pitch spiral acquisition.

AIMS: We evaluated the feasibility and image quality of a new scan mode for coronary computed tomography angiography (CTA) with an effective dose of less than 1 mSv. METHODS AND RESULTS: In 50 consecutive patients (body weight

Radiation exposure and image quality in staged low-dose protocols for coronary dual-source CT angiography: a randomized comparison.

OBJECTIVE: To evaluate staged low-dose approaches for coronary CT angiography (CTA) in which a standard sequence was added if the low-dose sequence did not allow reliable rule-out of coronary stenosis. PATIENTS AND METHODS: A total of 176 consecutive patients referred for dual-source CTA were randomized to three protocols: group 1 using prospective ECG-triggering (100 kV, 330 mAs), group 2 a retrospectively gated "MinDose" sequence (100 kV, 330 mAs) and group 3 a standard spiral sequence (120 kV, 400 mAs). If image quality in low-dose groups 1 or 2 was non-diagnostic, an additional standard CT examination (as in group 3) was performed. RESULTS: Non-diagnostic image quality was found in 11/56, 4/55, and 2/65 patients (46/896, 4/880 and 3/1,040 coronary segments) in groups 1, 2 and 3, respectively. Median (interquartile ranges) volumes of contrast material, CTDI(vol), DLP and effective dose for low-dose groups 1 and 2 and for standard group 3 were 92.5 (11.3), 75.0 (2.5) and 75.0 (9.0) ml; 8.0 (1.4), 16.8 (4.8) and 48.1 (14.2) mGy; 108.0 (27.3), 246.0 (93.0) and 701.0 (207.8) mGy cm; and 1.5 (0.4), 3.4 (1.3) and 9.8 (2.9) mSv, respectively. CONCLUSION: A staged coronary CTA protocol with an initial low-dose approach and addition of a standard sequence--should image quality be too low--can lead to a substantial reduction in radiation exposure.

Comparison of dual source computed tomography versus intravascular ultrasound for evaluation of coronary arteries at least one year after cardiac transplantation.

This study evaluated the ability of dual-source computed tomography (DSCT) to detect coronary allograft vasculopathy (CAV) in heart transplant recipients using intravascular ultrasound (IVUS) as the standard of reference. Thirty patients with heart transplants (81% men, mean age 40 years) underwent DSCT (330-ms gantry rotation, 2 x 64 x 0.6-mm collimation, 60- to 80-ml contrast agent, no additional beta blockers) before invasive coronary angiography including IVUS of 1 vessel. Detection of CAV by DSCT was qualitatively defined as the presence of any coronary plaque. Mean heart rate during dual-source computed tomographic scanning was 80 +/- 14 beats/min. Four hundred fifty-nine segments with a vessel caliber >or=1.5 mm according to quantitative coronary angiography were evaluated in 30 patients. Of these, 96% were considered to have excellent or good image quality. IVUS detected CAV in 17 of 30 patients (57%) and in 41 of 110 coronary segments (37%). Compared to IVUS, sensitivity, specificity, positive and negative predictive values for the detection of CAV by DSCT were 85%, 84%, 76%, and 91%, respectively. In conclusion, DSCT permits the investigation of transplant recipients concerning the presence of CAV with good image quality and high diagnostic accuracy.

Prospectively ECG-triggered high-pitch spiral acquisition for coronary CT angiography using dual source CT: technique and initial experience.

OBJECTIVE: We evaluated radiation exposure and image quality of a new coronary CT angiography protocol, high-pitch spiral acquisition, using dual source CT (DSCT). MATERIAL AND METHODS: Coronary CTAwas performed in 25 consecutive patients with a stable heart rate of 60 bpm or less after premedication, using 2 x 128 0.6-mm sections, 38.4-mm collimation width and 0.28-s rotation time. Tube settings were 100 kV/320 mAs and 120 kV/400 mAs for patients below and above 100-kg weight, respectively. Data acquisition was prospectively ECG-triggered at 60% of the R-R interval using a pitch of 3.2 (3.4 for the last 10 patients). Images were reconstructed with 75-ms temporal resolution, 0.6-mm slice thickness and 0.3-mm increment. Image quality was evaluated using a four-point scale (1 = excellent, 4 = unevaluable). RESULTS: Mean range of data acquisition was 113 +/- 22 mm, mean duration was 268 +/- 23 ms. Of 363 coronary artery segments, 327 had an image quality score of 1, and only 2 segments were rated as "unevaluable". Mean dose-length product (DLP) was 71 +/- 23 mGy cm, mean effective dose was 1.0 +/- 0.3 mSv (range 0.78-2.1 mSv). For 21 patients with a body weight below 100 kg, mean DLP was 63 +/- 5 mGy cm (0.88 +/- 0.07 mSv; range 0.78-0.97 mSv). CONCLUSION: Prospectively ECGtriggered high-pitch spiral CT acquisition provides high and stable image quality at very low radiation dose.

Left bundle branch block causes relative but not absolute septal underperfusion during exercise.

AIMS: Left bundle branch block (LBBB) often causes septal perfusion defects in radionuclide myocardial perfusion imaging using exercise (Ex) but rarely using vasodilator stress. We studied whether this is due to an underlying structural disease inherent to spontaneous LBBB or whether it is also found in temporary LBBB induced by right ventricular pacing (PM) indicating a functional rather than a structural alteration. METHODS AND RESULTS: Regional myocardial blood flow (MBF) at rest and at Ex was measured with 15O-H2O and PET in 10 age-matched healthy volunteers (controls), 10 LBBB patients and 10 PM patients with right ventricular pacing off and on (PM off and PM on). Although at Ex septal MBF tended to be higher in LBBB than in controls (3.04 +/- 1.18 vs. 2.27 +/- 0.72 mL/min/g; P = ns), the ratio septal/lateral MBF was 19% lower in LBBB than in controls (P < 0.05). Similarly, switching PM on at Ex decreased the ratio septal/lateral MBF by 17% (P < 0.005). CONCLUSION: The apparent septal perfusion defect in LBBB is mainly due to a relative lateral hyperperfusion rather than to an absolute septal flow decrease. This pattern seems to be reversibly inducible by right ventricular pacing, suggesting a functional rather than a structural alteration.

Coronary CT angiography and myocardial perfusion imaging to detect flow-limiting stenoses: a potential gatekeeper for coronary revascularization?

AIMS: To evaluate the diagnostic accuracy of a combined non-invasive assessment of coronary artery disease with coronary CT angiography (CTA) and myocardial perfusion imaging (MPI) for the detection of flow-limiting coronary stenoses and its potential as a gatekeeper for invasive examination and treatment. METHODS AND RESULTS: In 78 patients (mean age 65 +/- 9 years) referred for coronary angiography (CA), additional CTA and MPI (using single-photon emission-computed tomography) were performed and the findings not communicated. Detection of flow-limiting stenoses (justifying revascularization) by the combination of CTA and MPI (CTA/MPI) was compared with the combination of quantitative coronary angiography (QCA) plus MPI (QCA/MPI), which served as standard of reference. The findings of both combinations were related to the treatment strategy (revascularization vs. medical treatment) chosen in the catheterization laboratory based on the CA findings. Sensitivity, specificity, positive and negative predictive value, and accuracy of CTA/MPI for the detection of flow-limiting coronary stenoses were 100% each. More than half of revascularization procedures (21/40, 53%) was performed in patients without flow-limiting stenoses and 76% (47/62) of revascularized vessels were not associated with ischaemia on MPI. CONCLUSION: The combined non-invasive approach CTA/MPI has an excellent accuracy to detect flow-limiting coronary stenoses compared with QCA/MPI and its use as a gatekeeper appears to make a substantial part of revascularization procedures redundant.

Caffeine impairs myocardial blood flow response to physical exercise in patients with coronary artery disease as well as in age-matched controls.

BACKGROUND: Caffeine is one of the most widely consumed pharmacologically active substances. Its acute effect on myocardial blood flow is widely unknown. Our aim was to assess the acute effect of caffeine in a dose corresponding to two cups of coffee on myocardial blood flow (MBF) in coronary artery disease (CAD). METHODOLOGY/PRINCIPAL FINDINGS: MBF was measured with (15)O-labelled H2O and Positron Emission Tomography (PET) at rest and after supine bicycle exercise in controls (n = 15, mean age 58+/-13 years) and in CAD patients (n = 15, mean age 61+/-9 years). In the latter, regional MBF was assessed in segments subtended by stenotic and remote coronary arteries. All measurements were repeated fifty minutes after oral caffeine ingestion (200 mg). Myocardial perfusion reserve (MPR) was calculated as ratio of MBF during bicycle stress divided by MBF at rest. Resting MBF was not affected by caffeine in both groups. Exercise-induced MBF response decreased significantly after caffeine in controls (2.26+/-0.56 vs. 2.02+/-0.56, P<0.005), remote (2.40+/-0.70 vs. 1.78+/-0.46, P<0.001) and in stenotic segments (1.90+/-0.41 vs. 1.38+/-0.30, P<0.001). Caffeine decreased MPR significantly by 14% in controls (P<0.05 vs. baseline). In CAD patients MPR decreased by 18% (P<0.05 vs. baseline) in remote and by 25% in stenotic segments (P<0.01 vs. baseline). CONCLUSIONS: We conclude that caffeine impairs exercise-induced hyperaemic MBF response in patients with CAD to a greater degree than age-matched controls.

High-pitch spiral acquisition: a new scan mode for coronary CT angiography.

Coronary CT angiography allows high-quality imaging of the coronary arteries when state-of-the-art CT systems are used. However, radiation exposure has been a concern. We describe a new scan mode that uses a very high-pitch spiral acquisition, "Flash Spiral," which has been developed specifically for low-dose imaging with dual-source CT. The scan mode uses a pitch of 3.2 to acquire a spiral CT data set, while covering the entire volume of the heart in one cardiac cycle. Data acquisition is prospectively triggered by the electrocardiogram and starts in late systole to be completed within one cardiac cycle. Images are reconstructed with a temporal resolution that corresponds to one-quarter of the gantry rotation time. Throughout the data set, subsequent images are reconstructed at later time instants in the cardiac cycle. In a patient with a heart rate of 49 beats/min, the Flash Spiral scan mode was used with a first-generation dual-source CT system and allowed artifact-free visualization of the coronary arteries with a radiation exposure of 1.7 mSv for a 12-cm scan range at 120 kVp tube voltage.

Protocol for measuring myocardial blood flow by PET/CT in cats.

PURPOSE: The aim of this study was to establish a protocol for measuring myocardial blood flow (MBF) by PET/CT in healthy cats. The rationale was its future use in Maine Coon cats with hypertrophic cardiomyopathy (HCM) as a model for human HCM. METHODS: MBF was measured in nine anaesthetized healthy cats using a PET/CT scanner and (13)NH(3) at rest and during adenosine infusion. Each cat was randomly assigned to receive vasodilator stress with two or three adenosine infusions at the following rates (microg/kg per minute): 140 (Ado 1, standard rate for humans), 280 (Ado 2, twice the human standard rate), 560 (Ado 4), 840 (Ado 6) and 1,120 (Ado 8). RESULTS: The median MBF at rest was 1.26 ml/min per g (n = 9; range 0.88-1.72 ml/min per g). There was no significant difference at Ado 1 (n = 3; median 1.35, range 0.93-1.55 ml/min per g; ns) but MBF was significantly greater at Ado 2 (n = 6; 2.16, range 1.35-2.68 ml/min per g; p < 0.05) and Ado 4 (n = 6; 2.11, 1.92-2.45 ml/min per g; p < 0.05). Large ranges of MBF values at Ado 6 (n = 4; 2.53, 2.32-5.63 ml/min per g; ns) and Ado 8 (n = 3; 2.21, 1.92-5.70 ml/min per g; ns) were noted. Observed adverse effects, including hypotension, AV-block and ventricular premature contractions, were all mild, of short duration and immediately reversed after cessation of the adenosine infusion. CONCLUSION: MBF can be safely measured in cats using PET. An intravenous adenosine infusion at a rate of 280 microg/kg per minute seems most appropriate to induce maximal hyperaemic MBF response in healthy cats. Higher adenosine rates appear less suitable as they are associated with a large heterogeneity in flow increase and rate pressure product, most probably due to the large variability in haemodynamic and heart rate response.

Multimodality preoperative planning and postoperative follow-up of a hybrid cardiac intervention.

We describe the case of a 59-year-old man who had aortic regurgitation and a hypoplastic aortic valve and for whom an echocardiography evaluation revealed a vascular tumor in the roof of the left atrium, which was suspected to be a hemangioma. After undergoing preoperative invasive catheter coronary angiography, echocardiography, and multislice computed tomography examinations, the patient underwent an aortic miniroot replacement. Intraoperative findings confirmed the findings of the preoperative evaluations. The tumor, although macroscopically verified as a hemangioma, was not resected because of the tumor's position and size, and the threat of uncontrollable bleeding. After an uneventful postoperative clinical course, a subsequent successful transcatheter coil occlusion of the coronary fistula from the left circumflex coronary artery was performed as an alternative to surgical resection of the tumor. This case emphasizes the future role of a multimodality hybrid approach for diagnosis, planning (different 2- and 3-dimensional imaging modalities), and treatment in the form of combining interventional (transcatheter) and surgical (open heart) techniques, which could optimize different treatment strategies. This approach could be further improved by increasing the installations of hybrid operating rooms.

Role of attenuation correction to discriminate defects caused by left bundle branch block versus coronary stenosis in single photon emission computed tomography myocardial perfusion imaging.

PURPOSE: To define the impact of attenuation correction (AC) on interpretation of perfusion abnormalities induced by left bundle branch block (LBBB) in myocardial perfusion imaging (MPI) and single photon emission computed tomography (SPECT). METHODS: Thirty-six patients with spontaneous and 12 with pacemaker (PM)-induced LBBB (mean age 68.6 +/- 9.7) underwent gated 1-day adenosine stress/rest Tc-99m tetrofosmin SPECT on a hybrid SPECT-CT dual-head detector camera with Hawkeye facility (Infinia, GE Healthcare, Milwaukee, WI). Images were analyzed using iterative reconstruction (IR) and AC by computerized tomography (IR-AC) and compared with filtered back protection (FBP) as a standard of reference. Defect extent and severity for the anterior, septal, apical, inferior, and lateral regions were assessed by computerized analysis. The combination of septal with anterior and/or apical perfusion defects was attributed to the typical LBBB-induced pattern. RESULTS: LBBB caused a typical perfusion pattern in 24 patients with spontaneous and in 10 with PM-induced LBBB, whereas MPI was normal in 14 patients. FBP revealed a partial reversibility of anterior (spontaneous LBBB) and apical-septal (spontaneous and PM-induced LBBB) defect severity. By IR-AC, LBBB caused comparable anteroseptal reversible perfusion defects (P < 0.05) but fixed apical defects. Apical-septal defect severity was higher and defect extent was larger in IR-AC compared with FBP (both P < 0.05). Defect extent was unchanged between rest and stress for both reconstructions. CONCLUSIONS: Spontaneous and PM-induced LBBB often induces typical perfusion defects in MPI at stress, partly reversible at rest. With IR-AC this typical pattern is more pronounced and less reversible, strengthening the confidence to discriminate such findings from ischemia.

Functionally relevant coronary artery disease: comparison of 64-section CT angiography with myocardial perfusion SPECT.

PURPOSE: To prospectively determine the accuracy of 64-section computed tomographic (CT) angiography for the depiction of coronary artery disease (CAD) that induces perfusion defects at myocardial perfusion imaging with single photon emission computed tomography (SPECT), by using myocardial perfusion imaging as the reference standard. MATERIALS AND METHODS: All patients gave written informed consent after the study details, including radiation exposure, were explained. The study protocol was approved by the local institutional review board. In patients referred for elective conventional coronary angiography, an additional 64-section CT angiography study and a myocardial perfusion imaging study (1-day adenosine stress-rest protocol) with technetium 99m-tetrofosmin SPECT were performed before conventional angiography. Coronary artery diameter narrowing of 50% or greater at CT angiography was defined as stenosis and was compared with the myocardial perfusion imaging findings. Quantitative coronary angiography served as a reference standard for CT angiography. RESULTS: A total of 1093 coronary segments in 310 coronary arteries in 78 patients (mean age, 65 years +/- 9 [standard deviation]; 35 women) were analyzed. CT angiography revealed stenoses in 137 segments (13%) corresponding to 91 arteries (29%) in 46 patients (59%). SPECT revealed 14 reversible, 13 fixed, and six partially reversible defects in 31 patients (40%). Sensitivity, specificity, and negative and positive predictive values, respectively, of CT angiography in the detection of reversible myocardial perfusion imaging defects were 95%, 53%, 94%, and 58% on a per-patient basis and 95%, 75%, 96%, and 72% on a per-artery basis. Agreement between CT and conventional angiography was very good (96% and kappa = 0.92 for patient-based analysis, 93% and kappa = 0.84 for vessel-based analysis). CONCLUSION: Sixty-four-section CT angiography can help rule out hemodynamically relevant CAD in patients with intermediate to high pretest likelihood, although an abnormal CT angiography study is a poor predictor of ischemia.