AbstractAimsSubcutaneous implantable cardioverter defibrillators (S-ICDs) are well established. However, inappropriate shocks (IAS) remain a source of concern since S-ICDs offer very limited troubleshooting options. In our multicentre case series, we describe several patients who experienced IAS due to a previously unknown S-ICD system issue.Methods and resultsWe observed six patients suffering from this novel IAS entity. The IAS occurred exclusively in primary or alternate S-ICD sensing vector configuration (therefore called ‘Sense-B-noise’). IAS were caused by non-physiologic oversensing episodes characterized by intermittent signal saturation, diminished QRS amplitudes, and disappearance of the artefacts after the IAS. Noise/oversensing could not be provoked by manipulation, X-ray did not show evidence for lead/header issues and impedance measurements were within normal limits. The pooled experience of our centres implies that up to ∼5% of S-ICDs may be affected. The underlying root cause was discussed extensively with the manufacturer but remains unknown and is under further investigation.ConclusionSense-B-noise is a novel cause for IAS due to non-physiologic signal oversensing, arising from a previously unknown S-ICD system issue. Sense-B-noise may be suspected if episodes of signal saturation in primary or alternate vector configuration are present, oversensing cannot be provoked, and X-ray and electrical measurements appear normal. The issue can be resolved by reprogramming the device to secondary sensing vector.

Background: Direct oral anticoagulants (DOACs) have a favourable risk-benefit profile compared to vitamin K-antagonists (VKAs) in atrial fibrillation (AF). Dosing is based on age, weight and renal function, without need of routine monitoring.Methods and results: In two prospective, multicentre AF cohorts (Swiss-AF, BEAT-AF) patients were stratified as receiving VKAs or adequately-, under-or overdosed DOACs, according to label. Primary outcome was a com-posite of major adverse clinical events (MACE), defined as cardiovascular death, myocardial infarction (MI), ischaemic stroke and systemic embolism. Secondary outcomes included major bleeding. Adjustment for con-founding was performed. Median follow-up was 4 years.Of 3236 patients, 1875 (58%) were on VKAs and 1361 (42%) were on DOACs, of which 1137 (83%) were adequately-, 134 (10%) over-and 90 (7%) under-dosed. Compared to adequately dosed individuals, overdosed patients were more likely to be older and female. Underdosing correlated with concomitant aspirin therapy and coronary artery disease. Both groups had higher CHA2DS2-VASc scores. Patients on overdosed DOACs had higher incidence of MACE (HR 1.75; CI 1.10-2.79; adjusted-HR: 1.22) and major bleeding (HR 1.99; CI 1.14-3.48; adjusted-HR: 1.51). Underdosing was not associated with a higher incidence of MACE (HR 0.94; CI 0.46-1.92; adjusted-HR 0.61) or major bleeding (HR 1.07; CI 0.46-2.46; adjusted-HR 0.82). After adjustment, all CIs crossed 1.0.Conclusion: Inappropriate DOAC-dosing was more prevalent in multimorbid patients, but did not correlate with higher risks of adverse events after adjusting for confounders. DOAC prescription should follow label.

Abstract Background Atrial fibrillation (AF) has been described as a common cardiovascular manifestation in patients suffering from coronavirus disease 2019 (COVID-19) and is discussed to be a potential risk factor for a poor clinical course. AF is also already known to be associated with increased risk for all cause death. Purpose In the present study we sought to investigate the impact of AF on the clinical trajectory of patients suffering from COVID-19. Methods We included all patients hospitalized due to COVID-19 in 2020 in our Hospital. A poor clinical trajectory was defined as transfer to intensive care unit (ICU), intermediate care unit (IMC) or death from any cause. Initial ECGs were analyzed in consensus by two experienced readers. First, we compared patients with poor clinical trajectory vs. good clinical course. Secondly, the study population was categorized into two groups with or without AF on admission. A subgroup analysis was performed to differentiate between new onset AF and patients with known history of AF. To compensate for confounders (age, BMI, known cardiomyopathy (CMP), known coronary artery disease (CAD), chronic airway disease, renal insufficiency, diabetes, arterial hypertension and sex), a full clinically validated multiple logistic regression model with poor clinical trajectory as dependent target variable was performed. Results From our enrolled 666 patients in 2020 (58% male, average age: 66 (IQR:58–80)) 223 patients (33.5%) experienced a poor clinical course. 179 (27%) patients were transferred to IMC/ICU and 86 (13%) patients died. All in all, patients with poor clinical trajectory were more frequently male (70% vs. 52%; P<0.001), older (71±14 vs. 64±20; P<0.001) and had significantly more co-morbidities such as CAD, CMP, hypertension and diabetes in comparison to patients with a good clinical course. 96 (14.4%) had AF on admission. Among these 37.5% had new-onset AF, which showed similar baseline characteristics as patients without AF. Indeed, patients with COVID-19 and new onset AF were more likely to die (25% vs 12%; P=0.038), or be in need for ICU/IMC (25% vs. 62%; P<0.001) and therefore experienced a poor clinical trajectory more frequently (75% vs. 31%; P<0.001) with a confounder adjusted OR of 5.89. In the subgroup analysis of all patients with AF on admission. Patients with new onset of AF had significantly more underlying CMP, Diabetes and chronic airways disease. While mortality was not higher in patients with new onset of AF, IMC/ICU transfers (62% vs 24%; P<0.001) and as a result poor clinical trajectory (75% vs 40%; P=0.001) was significantly increased in comparison to patients with known AF. Conclusion In patients suffering from COVID-19, new onset of AF on admission was associated with a poor clinical course and higher in-hospital mortality. Funding Acknowledgement Type of funding sources: None.

Background: Leadless pacemakers are an established treatment option for bradyarrhythmias. Similar to conventional transvenous pacemakers, satisfying pacing values during implantation are targeted for optimal long-term device function. The objective is to investigate the role of a local injury current (IC) in leadless pacemaker implantations. Method: The IC, sensing value, capture threshold and impedance were collected in 30 consecutive patients receiving a leadless pacemaker. Results: 39 EGMs were recorded from 30 patients (including 9 device repositions). An IC was detected in 15 cases (38%). At implantation, the presence of an IC was associated with a significantly lower sensing (7.1 +/- 3.7 mV vs 12.0 +/- 4.0 mV; P = 0.004) and a higher capture threshold (median threshold 1.13 Vat 0.24 ms [0.50-2.00] vs 0.50 Vat 0.24 ms [0.25-0.75]; P = 0.002) and with a 26 fold higher likelihood of device repositioning compared to the absence of an IC (OR 26.3 [2.79-248], P < 0.001). Patients with an IC in their final implant position had a lower sensing (9.3 +/- 4.4 mV vs 13.6 +/- 4.7 mV at implantation, P = 0.04), while the initially similar capture threshold was lower after 24 h in the IC group. After 2 weeks, all parameters were similar between the two groups. Conclusions: Our study shows that an IC can readily be observed during leadless pacemaker implantation associated with a lower sensing and a higher capture threshold at implantation but with similar to even better values during follow-up. (C) 2020 Elsevier B.V. All rights reserved.

OBJECTIVES We studied the acute effect of caffeine on myocardial blood flow (MBF) at rest and exercise in healthy volunteers at normoxia and during acute exposure to simulated altitude. BACKGROUND Caffeine is a widely consumed stimulant, although its cardiovascular safety remains controversial and its effect on MBF is unknown. METHODS O-labeled H2O and positron emission tomography (PET) were used to measure regional MBF at rest and immediately after supine bicycle exercise in healthy volunteers at normoxia (n 10; mean workload, 175 W; 98% predicted; mean age, 27 6 years) as well as during hypoxia, simulating an altitude of 4,500 m by inhalation of a mixture of 12.5% oxygen (n 8; 148 W; 78% predicted; mean age, 29 4 years). Measurements were repeated 50 min after oral ingestion of caffeine (200 mg). Myocardial flow reserve (MFR) was calculated as the ratio of hyperemic to resting MBF. RESULTS Resting MBF was not affected by caffeine at normoxia (1.05 0.36 ml/min/g vs. 1.17 0.27 ml/min/g; p NS), although it was significantly increased at hypoxia (1.71 0.41 ml/min/g vs. 2.22 0.49 ml/min/g; p 0.001). By contrast, exercise-induced hyperemic MBF decreased significantly at normoxia (2.51 0.58 ml/min/g vs. 2.15 0.47 ml/min/g; p 0.05) and hypoxia (5.15 0.79 ml/min/g vs. 3.98 0.83 ml/min/g; p 0.005 vs. baseline; p 0.005 vs. normoxia). The MFR decreased by 22% at normoxia (2.53 0.69 to 1.90 0.49; p 0.01) and by 39% at hypoxia (3.13 0.60 to 1.87 0.45, p 0.005; p 0.05 vs. normoxia). CONCLUSIONS In healthy volunteers, a caffeine dose corresponding to two cups of coffee (200 mg) significantly decreased exercise-induced MFR at normoxia and was even more pronounced during exposure to altitude. (J Am Coll Cardiol 2006;47:405–10) © 2006 by the American ublished by Elsevier Inc. doi:10.1016/j.jacc.2005.08.064

AIMS:We studied the interrelation between oxygen consumption and myocardial blood flow (MBF) during recovery. MBF is directly dependent on oxygen consumption. The latter is linearly related to the heart rate-blood pressure product (RPP, bpm × mmHg), an index reflecting external cardiac work. In the immediate post-exercise period, cardiac output decreases considerably. This is expected to be paralleled by a rapid fall in oxygen demand, rendering ischaemia unlikely. Thus, the phenomenon of ST-segment depression during recovery remains unexplained.METHODS AND RESULTS:(15)O-labelled water and positron emission tomography were used to measure MBF in 14 young healthy volunteers (mean age 27 ± 3 years) during the following study conditions: (i) at rest, (ii) during a steady submaximal supine bicycle exercise stress within the scanner, and (iii) during recovery immediately after cessation of exercise. During recovery, RPP decreased by 43% (18 768 ± 1337 vs. 11 652 ± 3224, P < 0.001). In contrast, the associated decrease in MBF (2.52 ± 0.52 vs. 1.93 ± 0.50 mL/min/g, P < 0.001) and perfusion reserve (2.68 ± 0.51 vs. 2.03 ± 0.42, P < 0.001) was significantly less pronounced (-24%, P < 0.01), indicating a relative delay in MBF recovery compared with cardiac work load.CONCLUSION:The mismatch between a rapid decrease in cardiac workload but preserved hyperaemic response early after cessation of physical exercise suggests an uncoupling of cardiac work and MBF during recovery.

Cadmium zinc telluride (CZT) detectors with linear counting rate response enable count subtraction in sequential scanning. We evaluated whether count subtraction eliminated the need for higher activity doses in the second part of the 1-d stress–rest myocardial perfusion imaging (MPI) protocol. Methods: For 50 patients (mean age ± SD, 66 ± 12 y) with visually abnormal (n = 42) or equivocal (n = 8) adenosine-stress MPI (320 MBq of 99mTc-tetrofosmin) on a CZT camera, rest MPI was performed with a low dose (320 MBq) and repeated after injection of an additional 640 MBq of 99mTc-tetrofosmin to achieve a standard 3-fold increased dose at rest (960 MBq), compared with stress (320 MBq). Low-dose rest myocardial perfusion images were reconstructed after subtracting the background activity of the preceding stress scan. Segmental percentage tracer uptake of the 2 rest myocardial perfusion images (320 vs. 960 MBq) was compared using intraclass correlation and Bland–Altman limits of agreement. Patient- and coronary territory–based clinical agreement was assessed. Results: The standard protocol revealed ischemia in 34 (68%) and a fixed defect in 8 (16%) patients, of whom 33 (97%) and 8 (100%) were correctly identified by low-dose MPI (clinical agreement, 98%). Segmental uptake correlated well between low- and standard-dose rest scans (r = 0.94, P < 0.001; Bland–Altman limits of agreement, −11 to +11%). Defect extent was 14.4% (low-dose) versus 13.1% (standard-dose) at rest (P = not statistically significant) and 26.6% at stress (P < 0.001 vs. rest scans). Conclusion: These promising results suggest that accurate assessment of ischemic myocardial disease is feasible with a low-dose–low-dose 1-d SPECT MPI protocol using a CZT device.

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.

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.

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.

Rationale and Objectives. The aim of this study was to compare the diagnostic accuracy of 64-slice computed tomographic coronary angiography (CTCA) in groups of patients with low, intermediate, and high risk for coronary artery disease (CAD) events.Materials and Methods. The institutional review board approved this study; written informed consent was obtained from all patients. Eighty-eight consecutive patients with suspected CAD (40 women; mean age, 64.3 +/- 9.4 years; range, 39-82) underwent CTCA, calcium scoring, and invasive coronary angiography and were grouped according to their Framingham 10-year risk for hard coronary events into low (<10%), intermediate (10%-20%), and high (>20%) risk categories. Significant stenoses (luminal diameter narrowing >= 50%) were assessed on an intention-to-diagnose-basis; no coronary segment was excluded and nonevaluative segments were rated false positive. To determine differences between groups, Kruskal-Wallis tests were performed for individually determined values of diagnostic performance.Results. Per-patient sensitivity, specificity, negative predictive, and positive predictive values were 90.0%, 79.2%, 95.0%, and 64.3%, respectively, with low (n = 34), 87.5%, 92.3%, 85.7%, and 93.3%, respecitively, with intermediate (n = 29), and 100%, 75.0%, 100%, and 89.5%, respectively, with high risk (n = 25), with a trend toward higher positive predictive value (P =.07). Per-segment negative predictive value was lower with high pretest probability (P <.01). Mean calciumscore units were 90, 220, and 312 (P =.23), and the prevalence of CAD was 29.4%, 55.2%, and 68.0% (P <.01) with low, intermediate, and high risk.Conclusion. Sensitivity and specificity of CTCA are not influenced by the prevalence of CAD, whereas the negative predictive value is lower and the positive predictive value tends to be higher in patients with a high prevalence of CAD.

Optimal atrioventricular delay (AVD) setting for cardiac resynchronisation therapy, i.e. biventricular pacing in patients with heart failure, remains a formidable challenge. Thus, the purpose of this study was to evaluate the effects of different AVD on inter- and intra-ventricular resynchronisation using phase histograms of radionuclide ventriculography (RNV).

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.

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.

PURPOSETo prospectively assess the depiction rate and morphologic features of myocardial bridging (MB) of coronary arteries with 64-section computed tomographic (CT) coronary angiography in comparison to conventional coronary angiography.MATERIALS AND METHODSPatients were simultaneously enrolled in a prospective study comparing CT and conventional coronary angiography, for which ethics committee approval and informed consent were obtained. One hundred patients (38 women, 62 men; mean age, 63.8 years +/- 11.6 [standard deviation]) underwent 64-section CT and conventional coronary angiography. Fifty additional patients (19 women, 31 men; mean age, 59.2 years +/- 13.2) who underwent CT only were also included. CT images were analyzed for the direct signs length, depth, and degree of systolic compression, while conventional angiograms were analyzed for the indirect signs step down-step up phenomenon, milking effect, and systolic compression of the tunneled segment. Statistical analysis was performed with Pearson correlation analysis, the Wilcoxon two-sample test, and Fisher exact tests.RESULTSMB was detected with CT in 26 (26%) of 100 patients and with conventional angiography in 12 patients (12%). Mean tunneled segment length and depth at CT (n = 150) were 24.3 mm +/- 10.0 and 2.6 mm +/- 0.8, respectively. Systolic compression in the 12 patients was 31.3% +/- 11.0 at CT and 28.2% +/- 10.5 at conventional angiography (r = 0.72, P < .001). With CT, a significant correlation was not found between systolic compression and length (r = 0.16, P = .25, n = 150) but was found with depth (r = 0.65, P < .01, n = 150) of the tunneled segment. In 14 patients in whom MB was found at CT but not at conventional angiography, length, depth, and systolic compression were significantly lower than in patients in whom both modalities depicted the anomaly (P < .001, P < .01, and P < .001, respectively).CONCLUSIONThe depiction rate of MB is greater with 64-section CT coronary angiography than with conventional coronary angiography. The degree of systolic compression of MB significantly correlates with tunneled segment depth but not length.

We aimed at assessing stent geometry and in-stent contrast attenuation with 64-slice CT in patients with various coronary stents. Twenty-nine patients (mean age 60 ± 11 years; 24 men) with 50 stents underwent CT within 2 weeks after stent placement. Mean in-stent luminal diameter and reference vessel diameter proximal and distal to the stent were assessed with CT, and compared to quantitative coronary angiography (QCA). Stent length was also compared to the manufacturer’s values. Images were reconstructed using a medium-smooth (B30f) and sharp (B46f) kernel. All 50 stents could be visualized with CT. Mean in-stent luminal diameter was systematically underestimated with CT compared to QCA (1.60 ± 0.39 mm versus 2.49 ± 0.45 mm; P < 0.0001), resulting in a modest correlation of QCA versus CT (r = 0.49; P < 0.0001). Stent length as given by the manufacturer was 18.2 ± 6.2 mm, correlating well with CT (18.5 ± 5.7 mm; r = 0.95; P < 0.0001) and QCA (17.4 ± 5.6 mm; r = 0.87; P < 0.0001). Proximal and distal reference vessel diameters were similar with CT and QCA (P = 0.06 and P = 0.03). B46f kernel images showed higher image noise (P < 0.05) and lower in-stent CT attenuation values (P < 0.001) than images reconstructed with the B30f kernel. 64-slice CT allows measurement of coronary artery in-stent density, and significantly underestimates the true in-stent diameter compared to QCA.