A. Moelker

Computed tomography versus exercise electrocardiography in patients with stable chest complaints: real-world experiences from a fast-track chest pain clinic

Objective: To compare the diagnostic performance of CT angiography (CTA) and exercise electrocardiography (XECG) in a symptomatic population with a low–intermediate prevalence of coronary artery disease (CAD). Design: Prospective registry. Setting: Tertiary university hospital. Patients: 471 consecutive ambulatory patients with stable chest pain complaints, mean (SD) age 56 (10), female 227 (48%), pre-test probability for significant CAD >5%. Intervention: All patients were intended to undergo both 64-slice, dual-source CTA and an XECG. Clinically driven quantitative catheter angiography was performed in 98 patients. Main outcome measures: Feasibility and interpretability of, and association between, CTA and XECG, and their diagnostic performance with invasive coronary angiography as reference. Results: CTA and XECG could not be performed in 16 (3.4%) vs 48 (10.2%, p<0.001), and produced non-diagnostic results in 3 (0.7%) vs 140 (33%, p<0.001). CTA showed ⩾1 coronary stenosis (⩾50%) in 140 patients (30%), XECG was abnormal in 93 patients (33%). Results by CTA and XECG matched for 185 patients (68%, p = 0.63). Catheter angiography showed obstructive CAD in 57/98 patients (58%). Sensitivity, specificity, positive and negative predictive value of CTA to identify patients with ⩾50% stenosis was 96%, 37%, 67% and 88%, respectively; compared with XECG: 71%, 76%, 80% and 66%, respectively. Quantitative CTA slightly overestimated diameter stenosis: 6 (21)% (R = 0.71), compared with QCA. Of the 312 patients (66%) with a negative CTA, 44 (14%) had a positive XECG, but only 2/17 who underwent catheter angiography had significant CAD. Conclusion: CTA is feasible and diagnostic in more patients than XECG. For interpretable studies, CTA has a higher sensitivity, but lower specificity for detection of CAD.

Labelling of mammalian cells for visualisation by MRI

Through labelling of cells with magnetic contrast agents it is possible to follow the fate of transplanted cells in vivo with magnetic resonance imaging (MRI) as has been demonstrated in animal studies as well as in a clinical setting. A large variety of labelling strategies are available that allow for prolonged and sensitive detection of the labelled cells with MRI. The various protocols each harbour specific advantages and disadvantages. In choosing a particular labelling strategy it is also important to ascertain that the labelling procedure does not negatively influence cell functionality, for which a large variety of assays are available. In order to overcome the challenges still faced in fully exploiting the benefits of in vivo cell tracking by MRI a good understanding and standardisation of the procedures and assays used will be crucial.

‘Prognostic implications of non-culprit plaques in acute coronary syndrome: non-invasive assessment with coronary CT angiography’

Aims Non-culprit plaques are responsible for a substantial number of future events in patients with acute coronary syndrome (ACS). In this study, we evaluated the prognostic implications of non-culprit plaques seen on coronary computed tomography angiography (CTA) in patients with ACS. Methods and results Coronary CTA was performed in 169 patients (mean 59 ± 11 years, 129 males) admitted with ACS. Data sets were assessed for the presence of obstructive non-culprit plaques (>50% luminal narrowing), segment involvement score, and quantitative measures of plaque burden, after censoring initial culprit plaques. Follow-up was performed for the occurrence of major adverse cardiovascular events (MACEs) unrelated to the initial culprit plaque; cardiac death, second ACS, or coronary revascularization after 90 days. After a median follow-up of 4.8 (IQR 2.6–6.6) years, MACE occurred in 36 (24%) patients: 6 cardiac deaths, 16 second ACS, and 14 coronary revascularizations. Dyslipidaemia (hazard ratio [HR] 3.1 [95% confidence interval 1.5–6.6]) and diabetes mellitus (HR 4.8 [2.3–10.3]) were univariable clinical predictors of MACE. Patients with remaining obstructive non-culprit plaques (HR 3.66 [1.52–8.80]) and higher plaque burden index (HR 1.22 [1.01–1.48]) had a more risk of MACE. In multivariate analysis, with diabetes, dyslipidaemia, and plaque burden index, obstructive non-culprit plaques (HR 3.76 [1.28–11.09]) remained an independent predictor of MACE. Conclusion Almost a quarter of the study population experienced a new event arising from a non-culprit plaque during a follow-up of almost 5 years. ACS patients with remaining obstructive non-culprit plaques or high plaque burden have an increased risk of future MACE.

First-line evaluation of coronary artery disease with coronary calcium scanning or exercise electrocardiography

BACKGROUND Although conventional (CAG) and computed tomography angiography (CTA) are reliable diagnostic modalities for exclusion of obstructive coronary artery disease (CAD), they are costly and with considerable exposure to radiation and contrast media. We compared the accuracy of coronary calcium scanning (CCS) and exercise electrocardiography (X-ECG) as less expensive and non-invasive means to rule out obstructive CAD. METHODS In a rapid-access chest pain clinic, 791 consecutive patients with stable chest pain were planned to undergo X-ECG and dual-source CTA with CCS. According to the Duke pre-test probability of CAD patients were classified as low (<30%), intermediate (30-70%) or high risk (>70%). Angiographic obstructive CAD (>50% stenosis by CAG or CTA) was found in 210/791 (27%) patients, CAG overruling any CTA results. RESULTS Obstructive CAD was found in 12/281 (4%) patients with no coronary calcium and in 73/319 (23%) with a normal X-ECG (p<0.001). No coronary calcium was associated with a substantially lower likelihood ratio compared to X-ECG; 0.11, 0.13 and 0.13 vs. 0.93, 0.55 and 0.46 in the low, intermediate and high risk group. In low risk patients a negative calcium score reduced the likelihood of obstructive CAD to less than 5%, removing the need for further diagnostic work-up. CCS could be performed in 754/756 (100%) patients, while X-ECG was diagnostic in 448/756 (59%) patients (p<0.001). CONCLUSIONS In real-world patients with stable chest pain CCS is a reliable initial test to rule out obstructive CAD and can be performed in virtually all patients.

Ventricular function and cardiac reserve in contemporary Fontan patients

BACKGROUND/OBJECTIVE Total cavopulmonary connection (TCPC) has been the preferred treatment for patients with univentricular hearts. Current TCPC-techniques are the intra-atrial lateral tunnel (ILT) and the extracardiac conduit (ECC). We aimed to determine ventricular function during rest and stress, and to compare results for both techniques and for left (LV) versus right ventricular (RV) dominance. METHODS 99 patients, aged 12.5 ± 4.0 years underwent echocardiography and magnetic resonance imaging (MRI), and 69 patients underwent stress MRI. RESULTS Echocardiography showed impaired systolic and diastolic function. MRI parameters were comparable between ILT and ECC at rest. During dobutamine there was a decrease in end-diastolic volume (EDVi) (91 ± 21 vs. 80 ± 20 ml/m(2) p<0.001). Ejection fraction (EF) and cardiac index (CI) during dobutamine were lower for ILT patients (59 ± 11 (ILT) vs. 64 ± 7% (ECC), p=0.027 and 4.2 ± 1.0 (ILT) vs. 4.9 ± 1.0L/min/m(2) (ECC), p=0.006), whereas other parameters were comparable. TEI-index was higher in ILT-patients (0.72 ± 0.27 (ILT) vs. 0.56 ± 0.22 (ECC), p=0.002). Diastolic function was frequently impaired in patients with a dominant RV (67% (RV) vs. 39% (LV), p=0.011). Patients with dominant LVs had smaller end-systolic volume (ESVi) (40 ± 13 (LV) vs. 47 ± 16 (RV) ml/m(2), p=0.030) and higher EF (55 ± 8 (LV) vs. 49 ± 9 ml/m(2) (RV), p=0.001) and contractility (2.3 ± 0.8 (LV) vs. 1.9 ± 0.7 mmHg/ml/m(2) (RV), p=0.050) during rest and higher EF during dobutamine (63 ± 8 (LV) vs. 58 ± 10 ml/m(2) (RV), p=0.043). CONCLUSION Ventricular function is relatively well preserved in modern-day Fontan patients. With dobutamine stress there is a decrease in EDVi. ECC patients have higher CI and EF during stress. Patients with a dominant RV have lower systolic, including impaired contractility, and diastolic function.

Different Algorithms for Quantitative Analysis of Myocardial Infarction with DE MRI. Comparison with Autopsy Specimen Measurements.

RATIONALE AND OBJECTIVES To compare two semiautomated methods for measurement of infarcted myocardium area on delayed contrast enhanced magnetic resonance imaging, with histopathology findings as standard of reference. MATERIALS AND METHODS Percentage area of myocardial infarction was measured in 10 Yorkshire landrace pigs manually and using two semiautomated methods. The first (standard deviation method) used two operator-selected regions of interest (ROIs) and nine different cutoff values (one to nine times the standard deviation of signal intensity in normal myocardium) to identify infarction. The second (threshold method) used threshold values based on percentages of maximum signal intensity to identify infarction. Results were compared with histopathology findings. RESULTS Difference between percentage area of infarction obtained with standard deviation method and autopsy specimens was in the range: -13.5% to +13.2%. With threshold method (thresholds from 30% to 90% of signal intensity), difference was -15% to +23%. Manual contouring underestimated infarcted area by 2% comparing to autopsy results. The best agreement between histopathology and semi-automated software was achieved for 4 standard deviations with standard deviation method: difference -0.45%, and for a percentage threshold of 70% (difference +0.67%) with threshold method. However, with standard deviation method, there was statistically significant difference between ROIs based on their location in viable myocardium: mean difference 1.7 ± 4%, P < .0001. CONCLUSION Semiautomated measurement of myocardial infarcted area on delayed enhanced magnetic resonance images performs well compared to autopsy. The threshold method, based on percentages of maximum signal intensity is preferable over standard deviation method, which is more susceptible to variability from location of ROIs within viable myocardium.

Impact of contrast material volume on quantitative assessment of reperfused acute myocardial infarction using delayed-enhancement 64-slice CT: experience in a porcine model

PurposeOur purpose in this study was to compare the impact of contrast material volume in delayed-enhancement computer tomography (CT) imaging for assessing acute reperfused myocardial infarction.Materials and methodsIn five domestic pigs (20–30 kg), the circumflex coronary artery (CX) was balloon-occluded for 2 h followed by reperfusion. After 5 days, CT imaging was performed after intravenous administration of iodinated contrast material (Iomeprol 400mgI/ml; Bracco, Italy). A 64-slice multidetector CT (MDCT) (Sensation 64, Siemens) scanner was used for imaging, with standard angiography characteristics. Three scans were performed: first, coronary angiography at first pass with 1.25 gI/kg of contrast material (ART); and remaining delayed-enhancement (DE1–DE2) 15 min after administration of 1.25 (DE1) and 15 min after additional administration of 2.50 gI/kg (=total 3.75 gI/kg — DE2). Mean heart rate decreased to 51±9 bpm after intravenous administration of Zatebradine (10 mg/kg). Data sets were reconstructed during the end-diastolic phase of the cardiac cycle. Areas of infarction-enhanced (DE), no-reflow (no-reflow) and remote myocardial [remote left ventricle (LV)] were manually contoured. CT attenuation values (Hounsfield units) were measured using five regions of interest: DE, no-reflow, remote LV, left ventricular cavity (lumen LV) and in air. Differences, correlations, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated.ResultsWe found significant differences between the attenuation of DE, no-reflow and remote LV (p<0.001). DE and no-reflow size were assessed accurately with DEMDCT. In particular, SNR and CNR showed higher values in DE2 (∼6.0 and 3.5, respectively; r2=0.90) vs. DE1 (∼4.0 and 2.2, respectively; r2=0.85).ConclusionsThe increase of contrast material volume determines a significant improvement in myocardial infarction image quality with DE-MDCT.RiassuntoObiettivoObiettivo di questo lavoro è stato valutare l’impatto del volume di agente di contrasto nella tecnica delayed-enhancement (DE) con apparecchiatura per la tomografia computerizzata (TC) a 64 strati (MSTC), per la valutazione quantitativa dell’infarto miocardico acuto riperfuso.Materiali e metodiIn 5 maiali domestici, il ramo circonflesso dell’arteria coronarica sinistra è stato occluso mediante pallone e sottoposta a riperfusione a distanza di 2 h. Dopo 5 giorni, sono state eseguite le scansioni MSTC mediante tecnica standard con mezzo di contrasto (MdC). La prima (ART), al primo passaggio di 1,25 gI/kg di agente di contrasto iodato; le rimanenti (DE1 e DE2), con tecnica Delayed-Enhancement: DE1 eseguita 15 min dopo somministrazione di 1.25gI/kg; DE2 eseguita 15 min dopo somministrazione aggiuntiva di 2,50 gI/kg (MdC totale=3,75 gI/kg). La frequenza cardiaca media è stata ridotta a 51±9 battiti per minuto (bpm) mediante somministrazione di zatebradina EV (10 mg/kg). I data-set sono stati ricostruiti durante la fase tele-diastolica del ciclo cardiaco. Sono state definite manualmente l’area di miocardio necrotico vascolarizzato (DE), devascolarizzato (no-reflow) e di miocardio sano (ventricolo sinistro [LV] remoto). I valori di attenuazione TC sono stati misurati in cinque regioni d’interesse posizionate nelle zone di DE, no-reflow, LV remoto, cavità ventricolare sinistra (LV lume) e in aria. In seguito sono state valutate le differenze, le correlazioni, i rapporti segnale/rumore (S/R) e contrasto (C/R).RisultatiSignificative differenze sono state riscontrate tra i valori di attenuazione TC dell’area DE, no-reflow e LV remoto (p<0,001). Le scansioni DE-MSTC permettono una miglior visualizzazione e caratterizzazione dell’area DE e no-reflow. In particolare, i valori di S/N e C/N risultano essere maggiori in DE2 (∼6,0 e 3,5, rispettivamente; r2=0,90) vs DE1 (∼4,0 e 2,2, rispettivamente; r2=0,85).ConclusioniL’aumento del volume di agente di contrasto determina una migliore qualità delle immagini dell’infarto miocardico con DE-MSTC.

Impact of tube current in the quantitative assessment of acute reperfused myocardial infarction with 64-slice delayed-enhancement CT: a porcine model

PurposeThis study evaluated the impact of tube current (mAs) in delayed-enhancement computed tomography (CT) imaging for assessing acute reperfused myocardial infarction in a porcine model.Materials and methodsIn five domestic pigs (mean weight 24 kg), the circumflex coronary artery was balloon-occluded for 2 h and then reperfused. After 5 days, CT imaging was performed following administration of iodinated contrast material. A 64-slice CT system was used to perform first-pass coronary angiography with a tube current of 15 mAs/kg [Arterial Phase (ART)] followed by two delayed-enhancement (DE) scans 15 min after contrast material administration, with a tube current of 15 mAs/kg and 37.5 mAs/kg, respectively (DE1 and DE2). The mean heart rate decreased to 51±9 beats/min after administration of zatebradine (10 mg/kg IV). The data set was reconstructed during the end-diastolic phase of the cardiac cycle. Areas with DE, no reflow and remote myocardium [remote left ventricular (LV)] were calculated. CT values expressed in Hounsfield units (HU) were measured using five regions of interest (ROI): DE, no reflow, remote LV, LV cavity (LV lumen) and in air, respectively. Differences, correlations, image quality [signal-to-noise ratio (SNR)] and contrast resolution [contrast-to-noise ratio (CNR)] were calculated.ResultsSignificant differences were found between attenuation of areas of DE, no reflow and remote LV (p<0.001) within the different scans. There was a fair correlation between DE and no-reflow attenuation (r=0.6; p<0.001). In DE1 vs. DE2, areas of DE and no reflow were not significantly different (p>0.05). The SNR and CNR were not significantly different in DE1 vs. DE2 (p>0.05).ConclusionsTube current does not significantly affect infarction area, image quality or contrast resolution of DE imaging with CT.RiassuntoObiettivoObiettivo del nostro lavoro è stato valutare l’impatto della corrente del tubo (mAs) nella tecnica di tomografia computerizzata in delayed-enhancement (DE-CT), utilizzata per la valutazione quantitativa dell’infarto miocardico acuto riperfuso in un modello animale porcino.Materiali e metodiIn 5 maiali domestici (peso medio 24 kg), il ramo circonflesso dell’arteria coronarica sinistra è stato occluso mediante pallone e sottoposto a riperfusione a distanza di 2 h. Dopo 5 giorni, le scansioni di tomografia computerizzata (TC) sono state eseguite previa somministrazione di agente di contrasto iodato ev. Le scansioni sono state eseguite mediante TC a 64-strati: la prima, angiografia-coronarica convenzionale di primo passaggio, eseguita ad una corrente del tubo di 15 mAs/kg (ART); le restanti due scansioni DE-CT eseguite 15 min dopo somministrazione di agente di contrasto iodato, ad una corrente del tubo di 15 mAs/kg e 37,5 mAs/kg, rispettivamente (DE1 e DE2). La frequenza cardiaca media è stata ridotta a 51±9 battiti per minuto (bpm) mediante somministrazione di zatebradina (10 mg/kg ev). I dataset sono stati ricostruiti durante la fase tele-diastolica del ciclo cardiaco. Sono state calcolate le aree di delayed-enhancement (miocardio infartuato, DE), No-Reflow (miocardio infartuato con ostruzione microvascolare, No-Reflow), e miocardio normale (LV Remoto). I valori di attenuazione TC (espressi in unità Hounsfield [UH]) sono stati misurati in cinque regioni d’interesse: DE, No-Reflow, LV Remoto, cavità ventricolare sinistra (LV Lume) e in aria, rispettivamente. Sono state valutate le differenze, le correlazioni, la qualità d’immagine (come rapporto segnale rumore, S/N) e la risoluzione di contrasto (come rapporto contrasto rumore, C/N).RisultatiSignificative differenze sono state trovate tra le attenuazioni dell’area DE, No-Reflow e LV Remoto, in ogni protocollo di scansione (p<0,001). Una buona correlazione è stata trovata tra le attenuazioni di DE e No-Reflow (r=0,6; p<0,001). In DE1 vs. DE2, non sono state trovate significative differenze tra l’area DE e No-Reflow (p>0,05), ed i valori di S/N e C/N (p>0,05).ConclusioniNell’imaging DE eseguito mediante TC, la corrente del tubo non influenza significativamente le dimensioni dell’area di infarto, la qualità d’immagine e la risoluzione di contrasto.