Whole-heart dynamic three-dimensional magnetic resonance perfusion imaging for the detection of coronary artery disease defined by fractional flow reserve: determination of volumetric myocardial ischaemic burden and coronary lesion location.

AIMS: Dynamic three-dimensional-cardiac magnetic resonance (3D-CMR) perfusion proved highly diagnostic for the detection of angiographically defined coronary artery disease (CAD) and has been used to assess the efficacy of coronary stenting procedures. The present study aimed to relate significant coronary lesions as assessed by fractional flow reserve (FFR) to the volume of myocardial hypoenhancement on 3D-CMR adenosine stress perfusion imaging and to define the inter-study reproducibility of stress inducible 3D-CMR hypoperfusion. METHODS AND RESULTS: A total of 120 patients with known or suspected CAD were examined in two CMR centres using 1.5 T systems. The protocol included cine imaging, 3D-CMR perfusion during adenosine infusion, and at rest followed by delayed enhancement (DE) imaging. Fractional flow reserve was recorded in epicardial coronary arteries and side branches with ≥2 mm luminal diameter and >40% severity stenosis (pathologic FFR < 0.75). Twenty-five patients underwent an identical repeat CMR examination for the determination of inter-study reproducibility of 3D-CMR perfusion deficits induced by adenosine. Three-dimensional CMR perfusion scans were visually classified as pathologic if one or more segments showed an inducible perfusion deficit in the absence of DE. Myocardial ischaemic burden (MIB) was measured by segmentation of the area of inducible hypoenhancement and normalized to left ventricular myocardial volume (MIB, %). Three-dimensional CMR perfusion resulted in a sensitivity, specificity, and diagnostic accuracy of 90, 82, and 87%, respectively. Substantial concordance was found for inter-study reproducibility [Lin's correlation coefficient: 0.98 (95% confidence interval: 0.96-0.99)]. CONCLUSION: Three-dimensional CMR stress perfusion provided high diagnostic accuracy for the detection of functionally significant CAD. Myocardial ischaemic burden measurements were highly reproducible and allowed the assessment of CAD severity.

Cellular actors, Toll-like receptors, and local cytokine profile in acute coronary syndromes.

AIMS: Inflammation plays a key role in acute coronary syndromes (ACS). Toll-like receptors (TLR) on leucocytes mediate inflammation and immune responses. We characterized leucocytes and TLR expression within coronary thrombi and compared cytokine levels from the site of coronary occlusion with aortic blood (AB) in ACS patients. METHODS AND RESULTS: In 18 ACS patients, thrombi were collected by aspiration during primary percutaneous coronary intervention. Thrombi and AB from these patients as well as AB from 10 age-matched controls without coronary artery disease were assessed by FACS analysis for cellular distribution and TLR expression. For further discrimination of ACS specificity, seven non-coronary intravascular thrombi and eight thrombi generated in vitro were analysed. In 17 additional patients, cytokine levels were determined in blood samples from the site of coronary occlusion under distal occlusion and compared with AB. In coronary thrombi from ACS, the percentage of monocytes related to the total leucocyte count was greater than in AB (47 vs. 20%, P = 0.0002). In thrombi, TLR-4 and TLR-2 were overexpressed on CD14-labelled monocytes, and TLR-2 was increased on CD66b-labelled granulocytes, in comparison with leucocytes in AB. In contrast, in vitro and non-coronary thrombi exhibited no overexpression of TLR-4. Local blood samples taken under distal occlusion revealed elevated concentrations of chemokines (IL-8, MCP-1, eotaxin, MIP-1alpha, and IP-10) and cytokines (IL-1ra, IL-6, IL-7, IL-12, IL-17, IFN-alpha, and granulocyte-macrophage colony-stimulating factor) regulating both innate and adaptive immunity (all P < 0.05). CONCLUSION: In ACS patients, monocytes accumulate within thrombi and specifically overexpress TLR-4. Together with the local expression patterns of chemokines and cytokines, the increase of TLR-4 reflects a concerted activation of this inflammatory pathway at the site of coronary occlusion in ACS.

Ultrafast nuclear myocardial perfusion imaging on a new gamma camera with semiconductor detector technique: first clinical validation.

PURPOSE: To assess the diagnostic performance of a novel ultrafast cardiac gamma camera with cadmium-zinc-telluride (CZT) solid-state semiconductor detectors for nuclear myocardial perfusion imaging (MPI). METHODS: The study group comprised 75 consecutive patients (55 men, BMI range 19-45 kg/m(2)) who underwent a 1-day (99m)Tc-tetrofosmin adenosine-stress/rest imaging protocol. Scanning was performed first on a conventional dual-detector SPECT gamma camera (Ventri, GE Healthcare) with a 15-min acquisition time each for stress and rest. All scans were immediately repeated on an ultrafast CZT camera (Discovery 530 NMc, GE Healthcare) with a 3-min scan time for stress and a 2-min scan time for rest. Clinical agreement (normal, ischaemia, scar) between CZT and SPECT was assessed for each patient and for each coronary territory using SPECT MPI as the reference standard. Segmental myocardial tracer uptake values (percent of maximum) using a 20-segment model and left ventricular ejection fraction (EF) values obtained using CZT were compared with those obtained using conventional SPECT by intraclass correlation and by calculating Bland-Altman limits of agreement. RESULTS: There was excellent clinical agreement between CZT and conventional SPECT on a per-patient basis (96.0%) and on a per-vessel territory basis (96.4%) as shown by a highly significant correlation between segmental tracer uptake values (r=0.901, p<0.001). Similarly, EF values for both scanners were highly correlated (r=0.976, p<0.001) with narrow Bland-Altman limits of agreement (-5.5-10.6%). CONCLUSION: The novel CZT camera allows a more than fivefold reduction in scan time and provides clinical information equivalent to conventional standard SPECT MPI.

Non-invasive assessment of coronary artery disease with CT coronary angiography and SPECT: a novel dose-saving fast-track algorithm.

PURPOSE: To validate a new low-dose and rapid stepwise individualized algorithm for non-invasive assessment of ischemic coronary artery disease by sequential use of prospectively ECG-triggered low-dose CT coronary angiography (CTCA) and low-dose single-photon emission computed tomography myocardial perfusion imaging (SPECT-MPI). METHODS: Forty patients referred for elective invasive coronary angiography (CA) were prospectively enrolled to undergo a comprehensive non-invasive evaluation with low-dose CTCA and a dose-reduced stress/rest SPECT-MPI scan (using dedicated reconstruction algorithms for low count scans). The following algorithm was reviewed: CTCA first, followed by a stress-only MPI if a coronary stenosis (> or = 50% diameter narrowing) or equivocal findings were observed. Only abnormal stress MPI scans were followed by rest MPI. The accuracy of the individualized algorithm to predict coronary revascularization and its mean effective radiation dose were assessed. RESULTS: CTCA documented CAD in 18 and equivocal findings in two patients, thus, requiring additional stress MPI scans. Of these, 16 were abnormal, therefore requiring a rest MPI scan, revealing ischemia in 15 patients. Sensitivity, specificity, negative and positive predictive value, and accuracy of the individualized algorithm for predicting coronary revascularization was 93.3%, 96.0%, 96.0%, 93.3% and 95.0% on a per-patient base. The mean effective radiation dose was significantly lower for the individualized (4.8 +/- 3.4 mSv) versus the comprehensive method (8.1 +/- 1.5 mSv) resulting in a total population radiation dose reduction of 132.6 mSv. CONCLUSION: This new individualized low-dose algorithm allows rapid and accurate prediction of invasive CA findings and of treatment decision with minimized radiation dose.

Coronary calcium score scans for attenuation correction of quantitative PET/CT 13N-ammonia myocardial perfusion imaging.

PURPOSE: The aim of this study was to evaluate whether ECG-triggered coronary calcium scoring (CCS) scans can be used for attenuation correction (AC) to quantify myocardial blood flow (MBF) and coronary flow reserve (CFR) assessed by PET/CT with (13)N-ammonia. METHODS: Thirty-five consecutive patients underwent a (13)N-ammonia PET/CT scan at rest and during standard adenosine stress. MBF values were calculated using AC maps obtained from the ECG-triggered CCS scan during inspiration and validated against MBF values calculated using standard non-gated transmission scans for AC. CFR was calculated as the ratio of hyperaemic over resting MBF. In all 35 consecutive patients intraobserver variability was assessed by blinded repeat analysis for both AC methods. RESULTS: There was an excellent correlation between CT AC and CCS for global MBF values at rest (n = 35, r = 0.94, p < 0.001) and during stress (n = 35, r = 0.97, p < 0.001) with narrow Bland-Altman (BA) limits of agreement (-0.21 to 0.10 ml/min per g and -0.41 to 0.30 ml/min per g) as well as for global CFR (n = 35, r = 0.96, p < 0.001, BA -0.27 to 0.34). The excellent correlation was preserved on the segmental MBF analysis for both rest and stress (n = 1190, r = 0.93, p < 0.001, BA -0.60 to 0.50) and for CFR (n = 595, r = 0.87, p < 0.001, BA -0.71 to 0.74). In addition, reproducibility proved excellent for global CFR by CT AC (n = 35, r = 0.91, p < 0.001, BA -0.42-0.58) and CCS scans (n = 35, r = 0.94, p < 0.001, BA -0.34-0.45). CONCLUSION: Use of attenuation maps from CCS scans allows accurate quantitative MBF and CFR assessment with (13)N-ammonia PET/CT.

Real-time breath-hold triggering of myocardial perfusion imaging with a novel cadmium-zinc-telluride detector gamma camera.

PURPOSE: The aim of this study was to assess the ability of real-time breath-hold-triggered myocardial perfusion imaging (MPI) using a novel cadmium-zinc-telluride (CZT) gamma camera to discriminate artefacts from true perfusion defects. METHODS: A group of 40 patients underwent a 1-day (99m)Tc-tetrofosmin pharmacological stress/rest imaging protocol on a conventional dual detector SPECT gamma camera with and without attenuation correction (AC), immediately followed by scanning on an ultrafast CZT camera with and without real-time breath-hold triggering (instead of AC) by intermittent scanning confined to breath-hold at deep inspiration (using list mode acquisition). We studied the use of breath-hold triggering on the CZT camera and its ability to discriminate artefacts from true perfusion defects using AC SPECT MPI as the reference standard. Myocardial tracer uptake (percent of maximum) from CZT was compared to AC SPECT MPI by intraclass correlation and by calculating Bland-Altman limits of agreement. RESULTS: AC of SPECT MPI identified 19 apparent perfusion defects as artefacts. Of these, 13 were correctly identified and 4 were partially unmasked (decrease in extent and/or severity) by breath-hold triggering of the CZT scan. All perfusion defects verified by SPECT MPI with AC were appropriately documented by CZT with and without breath-hold triggering. This was supported by the quantitative analysis, as the correlation (r) of myocardial tracer uptake between CZT and AC SPECT improved significantly from 0.81 to 0.90 (p<0.001) when applying breath-hold triggering. Similarly, Bland-Altman limits of agreement were narrower for CZT scans with breath-hold triggering. CONCLUSION: This novel CZT camera allows real-time breath-hold triggering as a potential alternative to AC to assist in the discrimination of artefacts from true perfusion defects.

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.

Diagnostic accuracy of computed tomography coronary angiography and evaluation of stress-only single-photon emission computed tomography/computed tomography hybrid imaging: comparison of prospective electrocardiogram-triggering vs. retrospective gating.

AIMS: To determine diagnostic accuracy, effective radiation dose, and potential value of computed tomography coronary angiography (CTCA) for hybrid imaging with single-photon emission computed tomography (SPECT) comparing prospective electrocardiogram (ECG)-triggering vs. retrospective ECG-gating. METHODS AND RESULTS: Two hundred patients underwent standard myocardial stress/rest- SPECT perfusion imaging, which served as standard of reference. One hundred consecutive patients underwent 64-slice CTCA using prospective ECG-gating, and were compared with 100 patients who had previously undergone CTCA using retrospective ECG-gating. For predicting ischaemia, CTCA with prospective ECG-triggering and a stenosis cut-off >50% had a per-vessel sensitivity, specificity, negative, and positive predictive value of 100, 84, 100, and 30%; respective values for CTCA with retrospective ECG-gating were similar (P = n.s.): 86, 83, 98, and 33%. Combining CTCA with stress-only SPECT revealed 100% clinical agreement with regard to perfusion defects, and provided additional information in half the patients on preclinical coronary findings. Effective radiation dose was 2.2 +/- 0.7 mSv for CTCA with prospective ECG-triggering, and 19.7 +/- 4.2 mSv with retrospective ECG-gating (P < 0.001) (5.4 +/- 0.8 vs. 24.1 +/- 4.3 mSv for hybrid imaging). CONCLUSION: Prospective ECG-triggering for CTCA reduces radiation dose by almost 90% without affecting diagnostic performance. Combined imaging with stress-only SPECT is an attractive alternative to standard stress/rest-SPECT for evaluation of coronary artery disease, offering additional information on preclinical atherosclerosis.

Body physique and heart rate variability determine the occurrence of stair-step artefacts in 64-slice CT coronary angiography with prospective ECG-triggering.

The purpose of this study was to describe and characterize the frequency and extent of stair-step artefacts in computed tomography coronary angiography (CTCA) with prospective electrocardiogram (ECG)-triggering and to identify their determinants. One hundred and forty three consecutive patients (55 women, mean age 57 +/- 13 years) underwent 64-slice CTCA using prospective ECG-triggering. Occurrence of stair-step artefacts in CTCA of the thoracic wall and the coronary arteries was determined and maximum offset was measured. If stair-step artefacts occurred in both cases, a difference between thoracic wall and coronary artery offset of 0.6 mm or greater was attributed to additional motion of the heart. Mean effective radiation dose was 2.1 +/- 0.7 mSv (range 1.0-3.5 mSv). Eighty-nine patients (62%) had stair-step artefacts in CTCA of the coronary arteries (mean offset of 1.7 +/- 1.1 mm), while only 77 patients had thoracic wall stair-step artefacts (mean offset of 1.0 +/- 0.3 mm; significantly different, P < 0.001). Stair-step artefacts in CTCA of the thoracic wall were determined by BMI and weight (P < 0.01), while artefacts in CTCA of the coronary arteries were associated with heart rate variability (P < 0.05). Stair-step artefacts in CTCA with prospective ECG-triggering are determined by (a) motion of the entire patient during table travel, particularly in large patients and (b) by motion of the heart, particularly when heart rates are variable.

Accuracy of low-dose computed tomography coronary angiography using prospective electrocardiogram-triggering: first clinical experience.

AIMS: To evaluate the accuracy of low-dose computed tomography coronary angiography (CTCA) using prospective ECG-triggering for the assessment of coronary artery disease (CAD). METHODS AND RESULTS: A total of 30 patients (19 males, 11 females, mean age 58.8 +/- 9.9 years) underwent low-dose CTCA and invasive coronary angiography (CA) [median 2 days (0, 41)]. Before CT scanning, intravenous beta-blocker was administered in 18 of 30 patients as heart rate (HR) was >65 b.p.m., achieving a mean HR of 55.7 +/- 7.9 b.p.m. CAD was defined as coronary artery narrowing > or =50%, using CA as standard of reference. The estimated mean effective radiation dose was 2.1 +/- 0.7 mSv (range: 1.0-3.3), yielding 96.0% (383/399) of evaluable segments. On an intention-to-diagnose-base, all non-evaluative segments were included in the analysis. Vessels with a non-evaluative segment and no further finding were censored as false positive. Patient-based analysis revealed sensitivity, specificity, positive predictive value, and negative predictive value of 100, 83.3, 90.0, and 100%, respectively. The respective values per vessel were 100, 88.9, 85.7, and 100%, respectively. CONCLUSION: Prospective ECG-triggering allows low-dose CTCA and provides high diagnostic accuracy in the assessment of CAD in patients with stable sinus rhythm and a low heart rate.

Closure of Large Percutaneous Femoral Venous Access Using a Modified "Figure-of-Eight" Suture.

Recent advances in different percutaneous treatments made insertion of large-caliber sheaths in the femoral veins more common. Venous punctures are historically managed by initial manual compression with subsequent application of a compression bandage and bed rest. We describe a modified "figure-of-eight" suture technique for minimizing the risk of accidental puncture of the vein while grabbing the subcutaneous tissue. We examined the safety and feasibility of this technique combined with early mobilization in a real-world setting. We performed a retrospective analysis on 56 consecutive patients undergoing percutaneous mitral valve repair using large femoral venous access. The patient population was heterogeneous and bleeding risk characteristics were common. Bleeding Academic Research Consortium Consensus (BARC)-classifiable bleeding complications occurred in eight patients (14%), BARC of two events or more in five patients (8.9%), and BARC of three or more event in only one patient (1.8%), which is a comparable success rate to large venous access closure with suture-mediated closure devices. No BARC Type 3b or BARC Type 5 bleeding occurred. During routine clinical follow-up, no groin-related problems were reported in all patients. Closure of large femoral venous access using a modified temporary subcutaneous figure-of-eight suture in combination of a light compression bandage and bed rest for 2 to 4 hours provides a safe and low-cost alternative to closure devices for early mobilization.

Accuracy of smartphone apps for heart rate measurement.

Background Smartphone manufacturers offer mobile health monitoring technology to their customers, including apps using the built-in camera for heart rate assessment. This study aimed to test the diagnostic accuracy of such heart rate measuring apps in clinical practice. Methods The feasibility and accuracy of measuring heart rate was tested on four commercially available apps using both iPhone 4 and iPhone 5. 'Instant Heart Rate' (IHR) and 'Heart Fitness' (HF) work with contact photoplethysmography (contact of fingertip to built-in camera), while 'Whats My Heart Rate' (WMH) and 'Cardiio Version' (CAR) work with non-contact photoplethysmography. The measurements were compared to electrocardiogram and pulse oximetry-derived heart rate. Results Heart rate measurement using app-based photoplethysmography was performed on 108 randomly selected patients. The electrocardiogram-derived heart rate correlated well with pulse oximetry ( r = 0.92), IHR ( r = 0.83) and HF ( r = 0.96), but somewhat less with WMH ( r = 0.62) and CAR ( r = 0.60). The accuracy of app-measured heart rate as compared to electrocardiogram, reported as mean absolute error (in bpm ± standard error) was 2 ± 0.35 (pulse oximetry), 4.5 ± 1.1 (IHR), 2 ± 0.5 (HF), 7.1 ± 1.4 (WMH) and 8.1 ± 1.4 (CAR). Conclusions We found substantial performance differences between the four studied heart rate measuring apps. The two contact photoplethysmography-based apps had higher feasibility and better accuracy for heart rate measurement than the two non-contact photoplethysmography-based apps.

Influence of altitude exposure on coronary flow reserve.

BACKGROUND: Although no data exist on the effect of altitude exposure on coronary flow reserve (CFR), patients with coronary artery disease (CAD) are advised not to exceed moderate altitudes of approximately 2500 m above sea level. We studied the influence of altitude on myocardial blood flow (MBF) in controls and CAD patients. METHODS AND RESULTS: In 10 healthy controls and 8 patients with CAD, MBF was measured by positron emission tomography and 15O-labeled water at rest, during adenosine stress, and after supine bicycle exercise. This protocol was repeated during inhalation of a hypoxic gas mixture corresponding to an altitude of 4500 m (controls) and 2500 m (CAD). Workload was targeted to comparable heart rate-blood pressure products at normoxia and hypoxia. Resting MBF increased significantly in controls at 4500 m (+24%, P<0.01) and in CAD patients at 2500 m (+24%, P<0.05). Altitude had no influence on adenosine-induced hyperemia and CFR. Exercise-induced hyperemia increased significantly in controls (+38%, P<0.01) at 4500 m (despite a reduction in workload, -28%, P<0.0001) but not in CAD patients at 2500 m (moderate decrease in workload, -11%, P<0.05). Exercise-induced reserve was preserved in controls (+10%, P=NS) but decreased in CAD patients (-18%, P<0.005). CONCLUSIONS: At 2500 m altitude, there is a significant decrease in exercise-induced reserve in CAD patients, indicating that compensatory mechanisms might be exhausted even at moderate altitudes, whereas healthy controls have preserved reserve up to 4500 m. Thus, patients with CAD and impaired CFR should be cautious when performing physical exercise even at moderate altitude.

Isolated ventricular noncompaction is associated with coronary microcirculatory dysfunction.

OBJECTIVES: We sought to analyze whether a microcirculatory dysfunction might be associated with isolated ventricular noncompaction (IVNC). BACKGROUND: In IVNC, which is a cardiomyopathy thus far "unclassified" by the World Health Organization, heart failure and sudden cardiac death are common findings, but the pathophysiologic mechanisms are unknown. METHODS: In 12 patients with IVNC and 14 control subjects, quantitative evaluation of regional myocardial perfusion (myocardial blood flow [MBF]) and coronary flow reserve (CFR, hyperemic/baseline MBF) was performed using positron emission tomography and (13)N-ammonia. The left ventricular myocardium was divided into nine segments, and the two-dimensional echocardiogram in each patient with IVNC was compared with CFR in each segment. Noncompaction was defined as a two-layered structure with excessive trabeculation. RESULTS: The CFR in control subjects averaged 4.2+/-0.9, providing a cut-off value > or =2.5, but it was 2.1+/-0.8 in patients with IVNC. A perfusion scan defect was found in 14 of 24 segments with noncompaction, although no defect was found in 76 of 84 normal segments (overall agreement 83%, p < 0.0001 by the chi-square test). In 16 of 21 segments with noncompaction, a decreased CFR was found; but a decreased CFR was also found in 36 of 60 segments without noncompaction (p = NS). In 45 of the 57 segments with wall motion abnormalities, CFR was decreased, but it was preserved in 17 of the 24 segments with normal wall motion (agreement 77%, p < 0.0001). CONCLUSIONS: In patients with IVNC, a decreased CFR is not confined to noncompacted segments, but extends to most segments with wall motion abnormalities. Thus, coronary microcirculatory dysfunction is associated with IVNC.

Integrated PET/CT for the assessment of coronary artery disease: a feasibility study.

UNLABELLED: An accurate, noninvasive technique for the diagnosis of coronary artery disease (CAD) should provide complementary information on coronary anatomy and pathophysiologic lesion severity. We present, what is to our knowledge, the first clinical evaluation of integrated PET/CT for combined acquisition of coronary anatomy and perfusion. METHODS: On an integrated PET/CT scanner, contrast-enhanced CT angiography (CTA) and rest/adenosine-stress myocardial perfusion scanning with (13)N-ammonia were performed on 25 patients with CAD documented by coronary angiography. Contrast-enhanced CTA was performed with retrospective electrocardiography gating after injection of 150 mL of intravenous contrast medium. Decisions on whether to treat with revascularization (anatomic lesion plus ischemia) or conservatively (no lesion or no ischemia) based on PET/CT were compared with those based on PET plus coronary angiography. RESULTS: Of the 100 coronary artery segments (left main, left anterior descending, left circumflex, and right in 25 patients), 7 (in 5 patients) were considered impossible to evaluate by CT because of rapid vessel movement but were correctly categorized by PET alone. In the remaining 93 segments, the sensitivity and specificity of PET/CT versus PET plus coronary angiography were 90% and 98%, respectively. Positive and negative predictive values were 82% and 99%, and accuracy was 97%. CONCLUSION: The data of this preliminary study suggest that PET/CT allows accurate noninvasive clinical decision making about CAD. Because of its high negative predictive value, PET/CT may play an important role in noninvasive selection of CAD patients for revascularization. Integration of higher-performance multislice spiral CT scanners into PET/CT hybrids will accelerate the clinical implementation of this technique.

Platelet inhibition in percutaneous coronary interventions.

Mechanical disruption of atherosclerotic plaques at the time of percutaneous coronary intervention (PCI) is a potent stimulus for arterial thrombosis. Since platelets play a crucial role in the cascade of clot formation, platelet inhibition is an essential step for successful PCI. Aspirin remains the cornerstone of any antithrombotic regimen in the interventional setting. The addition of a thienopyridine is mandatory following stenting to prevent thrombosis of the device. Whenever possible, patients undergoing PCI should be pretreated with clopidogrel and the drug should be continued for up to 1 year. Glycoprotein IIb/IIIa antagonists should be administered in high-risk patients, such as those with acute coronary syndromes, diabetes, or complex coronary anatomy.

Bicycle exercise stress in PET for assessment of coronary flow reserve: repeatability and comparison with adenosine stress.

UNLABELLED: PET allows absolute measurements of myocardial blood flow (MBF). The aim of the present study was to evaluate the feasibility and repeatability of supine bicycle exercise stress, compared with standard adenosine stress, in PET. METHODS: In 11 healthy volunteers, MBF was assessed at rest, during adenosine-induced (140 microg/kg/min over 7 min) hyperemia, and immediately after supine bicycle exercise (mean workload, 130 W, which is 70% of the predicted value) using PET and (15)O-H(2)O. The assessment was then repeated after 20 min. Coronary flow reserve (CFR) was calculated as hyperemic/resting MBF for adenosine stress and exercise stress. Repeatability was evaluated according to the method of Bland and Altman. RESULTS: No significant differences were found between the paired resting MBF (1.22 +/- 0.16 vs. 1.26 +/- 0.21 mL/min/g; mean difference, 3% +/- 11%) and the hyperemic MBF with adenosine stress (5.13 +/- 0.74 vs. 4.97 +/- 1.05; mean difference, -4% +/- 14%) or exercise stress (2.35 +/- 0.66 vs. 2.25 +/- 0.61; mean difference, -4% +/- 19%). CFR was reproducible with adenosine stress (4.23 +/- 0.62 vs. 4.05 +/- 1.06, P = not statistically significant; mean difference, -5% +/- 19%) and exercise stress (1.91 +/- 0.46 vs. 1.80 +/- 0.44, P = not statistically significant; mean difference, -5% +/- 15%). Repeatability coefficients for MBF were 0.26 (rest), 1.34 (adenosine stress), and 0.82 (exercise stress) mL/min/g. CONCLUSION: Assessment of CFR with (15)O-H(2)O and PET using bicycle exercise in the PET scanner is feasible and at least as repeatable as using adenosine stress.

Gated (99m)Tc-tetrofosmin SPECT for discriminating infarct from artifact in fixed myocardial perfusion defects.

UNLABELLED: Soft-tissue attenuation artifacts generally appear as fixed perfusion-scan defects. Gated (99m)Tc-tetrofosmin SPECT may help differentiate myocardial infarction (MI) from artifacts, as fixed defects with decreased function (wall motion and thickening) probably represent MI, whereas attenuation artifacts represent preserved function. METHODS: Ungated stress and gated rest (99m)Tc-tetrofosmin SPECT was performed on 153 consecutive patients referred for evaluation of coronary artery disease. From stress and summed gated rest images, 107 patients (70%) were identified with isolated fixed defects. The function of the defects was assessed semiquantitatively from gated stress images. The findings were correlated with clinical (history or electrocardiographic Q waves) evidence of MI. RESULTS: Of 62 patients with fixed defects and clinical MI, 60 (97%) had an abnormal defect function. Of 45 patients with no clinical MI, 16 (36%) had decreased function of the defect, possibly indicating silent MI. In 29 of the 45 patients (64%) with no clinical MI, defect function was normal. Because most (90%) fixed defects with normal systolic function occurred in men with inferior fixed defects (87%) or women with anterior fixed defects (3%), these were most likely attenuation artifacts. By reclassifying the condition of patients with fixed defects and normal function as normal, patients with unexplained fixed defects (no clinical MI) decreased from 29% to 10%. CONCLUSION: Gating adds considerable value to (99m)Tc-tetrofosmin SPECT myocardial perfusion imaging in characterizing fixed defects and potentially improves test specificity.

Beta-adrenergic blockade and myocardial perfusion in coronary artery disease: differential effects in stenotic versus remote myocardial segments.

UNLABELLED: Beta-adrenergic blocking agents are widely used in coronary artery disease (CAD), although their impact on myocardial blood flow (MBF) and coronary flow reserve (CFR) remains unclear. We studied the effect of long-term beta-blocker treatment (carvedilol or metoprolol) on coronary microcirculation in CAD patients using PET. METHODS: Regional and global resting and adenosine-induced hyperemic MBF and CFR were measured with 13N-ammonia and PET in 36 CAD patients before and after 12 wk of oral therapy with either carvedilol, 50 mg/d, or metoprolol, 100 mg/d. RESULTS: Beta-blockade decreased global resting MBF in proportion to cardiac work (from 0.86 +/- 0.20 to 0.77 +/- 0.14 mL/min/g, P < 0.05) without affecting global hyperemic flow. Hyperemic MBF was significantly lower in stenosis-dependent segments than in remote segments (1.76 +/- 0.64 vs. 2.04 +/- 0.67 mL/min/g, P < 0.05) at baseline but was comparable in both after treatment (2.02 +/- 0.68 vs. 1.90 +/- 0.78 mL/min/g, P = not statistically significant [NS]), resulting in a significant CFR increase in stenotic segments (+15%, P < 0.05) but not in remote segments (+9%, P = NS). CONCLUSION: The beneficial effect of beta-adrenergic blockade can be explained by the reduction in oxygen consumption (= decreased demand) but also by a modest improvement in vasodilator capacity (= increased supply). The improvement in CFR is found predominantly in stenosis-dependent rather than remote segments.

CT attenuation correction for myocardial perfusion quantification using a PET/CT hybrid scanner.

UNLABELLED: In routine PET, a 10- to 20-min transmission scan with a rotating (68)Ge source is commonly obtained for attenuation correction (AC). AC is time-consuming using this procedure and could considerably be shortened by instead using a rapid CT scan. Our aim was to evaluate the feasibility of CT AC in quantitative myocardial perfusion PET using a hybrid PET/CT scanner. METHODS: (13)N-labeled NH(3) and PET were used to measure myocardial blood flow (MBF) (mL/min/g) at rest and during standard adenosine stress. In group 1 (n = 7), CT scans (0.5 s) of the heart area with different tube currents (10, 40, 80, and 120 mA) were compared with a standard (68)Ge transmission (20 min) and with no AC. In group 2 (n = 3), the repeatability of 8 consecutive CT scans at a tube current of 10 mA was assessed. In group 3 (n = 4), emission was preceded and followed by 3 CT scans (10 mA) and 1 (68)Ge scan for each patient. For reconstruction, filtered backprojection (FBP) was compared with iterative reconstruction (IT). RESULTS: For group 1, no significant difference in mean MBF for resting and hyperemic scans was found when emission reconstructed with (68)Ge AC was compared with emission reconstructed with CT AC at any of the different tube currents. Only emission without any correction differed significantly from (68)Ge AC. For group 2, repeated measurements revealed a coefficient of variance ranging from 2% to 5% and from 2% to 6% at rest and at stress, respectively. For group 3, similar reproducibility coefficients (RC) for MBF were obtained when (68)Ge AC(FBP) was compared with (68)Ge AC(IT) (RC = 0.218) and when CT AC(FBP) was compared with CT AC(IT) (RC = 0.227). Even better reproducibility (lower RC) was found when (68)Ge AC(FBP) was compared with CT AC(FBP) (RC = 0.130) and when (68)Ge AC(IT) was compared with CT AC(IT) (RC = 0.146). CONCLUSION: Our study shows that for the assessment of qualitative and quantitative MBF with a hybrid PET/CT scanner, the use of CT AC (with a tube current of 10 mA) instead of (68)Ge AC provides accurate results.