James Stirrup

A single, comprehensive non-invasive cardiovascular assessment in pulmonary arterial hypertension: combined computed tomography pulmonary and coronary angiography.

BACKGROUND Comprehensive assessment of pulmonary arterial hypertension (PAH) should identify structural causes and subsequent cardiopulmonary consequences of PAH. This currently requires the use of several imaging modalities. Computed tomography (CT) is routinely used for pulmonary angiography (CTPA). Our aim was to assess whether combined pulmonary and coronary angiography (CTPCA) using ECG-gated, multi-detector CT (MDCT) would allow satisfactory pulmonary angiography, coronary angiography and ventriculography to be combined into a single acquisition using a single imaging modality. METHODS We assessed CTPCA in 30 consecutive adult patients (mean age 41+/-11 years) with a diagnosis of PAH. In addition to the standard assessment of lung parenchyma and pulmonary vasculature, we assessed the ability of CT to satisfactorily visualise coronary vessels and biventricular function. Functional analysis included: end-diastolic volume (EDV), end-systolic volume (EDV), stroke volume (SV) and ejection fraction (EF) and mass and these parameters were correlated with same day cardiovascular magnetic resonance (CMR). RESULTS Lung parenchyma, pulmonary and coronary vessels were fully visualised in all cases. Ventriculography correlated well with same day CMR (RVEDV r=0.94, +19.5+/-49.2 ml, RVESV r=0.93, +11.1+/-46.4 ml, RVSV r=0.60, +8.5+/-41.6 ml, RVEF r=0.77, -0.5+/-21.3% and RV mass r=0.73, -17.3+/-60.4 g, LVEDV r=0.68, +12.2+/-110 ml, LVESV r=0.69, +7.5+/-59.7 ml, LVSV r=0.54, +2.5+/-40.6 ml, LVEF r=0.73, -1.9+/-20.8% and LV mass r=0.87, -20.5+/-22.5 g (all p<0.001)). Associated congenital cardiovascular malformations were characterised in 22/30 cases. CONCLUSIONS A CTPCA protocol allows safe, fast, comprehensive, non-invasive assessment of the possible anatomical causes and cardiopulmonary sequelae of PAH in adult patients, demonstrating congenital heart abnormalities, coronary artery disease and cardiac function.

Attenuation of Adenosine-Induced Myocardial Perfusion Heterogeneity by Atenolol and Other Cardioselective β-Adrenoceptor Blockers: A Crossover Myocardial Perfusion Imaging Study

Little is known about the effect of chronic β-blockade on adenosine actions. We sought to investigate the effect of oral β-blockers on the presence, extent, and severity of myocardial perfusion abnormality induced by adenosine in patients with coronary artery disease. Methods: In this crossover study, 45 male patients with coronary artery disease on β-blocker therapy with atenolol, bisoprolol, or metoprolol underwent adenosine myocardial perfusion imaging both on and off β-blockade in a random order on separate days. Myocardial perfusion was assessed both qualitatively and quantitatively. Hemodynamic response, image analysis, and sensitivity for the detection of coronary stenosis (≥50% luminal diameter reduction on x-ray coronary angiography) were compared between the on and off β-blocker studies. Results: Rate pressure product both at baseline and at peak adenosine infusion decreased by 23% ± 15% and 21% ± 18%, respectively, after β-blockade (P < 0.001 for all). The median (interquartile range) summed difference score, a measure of defect reversibility, and quantitative defect size were both significantly lower after β-blockade (median, 7.0 [interquartile range, 2.0–9.5] vs. median, 5.0 [interquartile range, 0–8.0], P = 0.002; and quantitative defect size, 18% [interquartile range, 9%−34%] vs. quantitative defect size, 6% [interquartile range, 0%−19%], P < 0.001, respectively). The overall sensitivity for the detection of coronary stenosis decreased from 0.76 (95% confidence interval, 0.65–0.88) to 0.58 (95% confidence interval, 0.45–0.71) after β-blockade (P = 0.03). Conclusion: β-blockade causes a small but significant reduction in the extent and severity of perfusion abnormality by adenosine. This may reduce the diagnostic sensitivity of adenosine myocardial perfusion imaging for the detection of flow-limiting coronary stenosis.

Comparison of 64-slice cardiac computed tomography with myocardial perfusion scintigraphy for assessment of global and regional myocardial function and infarction in patients with low to intermediate likelihood of coronary artery disease

Background. Cardiac computed tomography (CCT) has the potential to assess both coronary anatomy and ventricular function in a single study. We examined the agreement between CCT and myocardial perfusion scintigraphy (MPS) for the assessment of global and regional ventricular function.Methods and Results. Research CCT was performed in 52 patients with a low to intermediate likelihood of coronary artery disease referred for MPS. Left ventricular enddiastolic volume, left ventricular end-systolic volume, left ventricular ejection fraction (LVEF), and myocardial wall motion and thickening were compared between techniques. In addition, myocardial contrast attenuation on CCT was compared with radiotracer uptake on MPS. LVEF values agreed well (mean difference, 4.1%; SD, 15.13%), but CCT left ventricular end-diastolic volume was greater compared with MPS (mean difference, 46.0 mL; SD, 33.34 mL) (P<.001). There was moderate agreement for segmental myocardial motion and thickening, with κ values of 0.57 (95% confidence interval, 0.51–0.63) and 0.47 (95% confidence interval, 0.41–0.53), respectively. Seventeen patients had hypoattenuation in at least 1 myocardial segment on CCT. Three of four patients with concomitant abnormalities of wall motion and thickening on CCT had infarction in the same territory on MPS.Conclusions. There was good agreement for LVEF between CCT and MPS but myocardial volumes differed, and these modalities cannot be used interchangeably. Mild abnormalities of regional function are detected more commonly by CCT than by MPS. Myocardial hypoattenuation on CCT is highly specific for myocardial infarction when associated with reduction of systolic wall thickening and regional wall motion abnormality.

64-Channel Cardiac Computed Tomography: Intraobserver and Interobserver Variability (Part 1): Coronary Angiography

Objectives: To assess intraobserver and interobserver variation in computed tomography coronary angiography (CTA) in 3 patient cohorts at very low, low-to-intermediate, and intermediate-to-high likelihood of coronary artery disease (CAD). Methods: One hundred thirty-three patients underwent 64-channel CTA. Coronary arteries were analyzed by 2 experienced blinded observers and reported as having 0%, 1% to 29%, 30% to 49%, 50% to 69%, 70% to 99%, or 100% stenosis. Intraobserver and interobserver agreement was calculated at cohort level and combined. Results: Overall intraobserver and interobserver agreement was good (&kgr; = 0.74 and &kgr; = 0.78, respectively). Segmental agreement for stenoses 50% or greater and 70% or greater was greater than 96%. Disagreements were more likely in the presence of noneccentric calcification for both intraobserver (odds ratio = 0.45 and 0.22) and interobserver (odds ratio = 0.40 and 0.10) measurements. Conclusions: Interobserver and intraobserver variability for the detection of coronary stenoses on CTA is good and justifies routine clinical use. The presence of noneccentric calcium and mixed plaque morphology are important causes of disagreement.

Recommendations for accurate CT diagnosis of suspected acute aortic syndrome (AAS)—on behalf of the British Society of Cardiovascular Imaging (BSCI)/British Society of Cardiovascular CT (BSCCT)

Accurate and timely assessment of suspected acute aortic syndrome is crucial in this life-threatening condition. Imaging with CT plays a central role in the diagnosis to allow expedited management. Diagnosis can be made using locally available expertise with optimized scanning parameters, making full use of recent advances in CT technology. Each imaging centre must optimize their protocols to allow accurate diagnosis, to optimize radiation dose and in particular to reduce the risk of false-positive diagnosis that may simulate disease. This document outlines the principles for the acquisition of motion-free imaging of the aorta in this context.

Implications for single phase prospective CT coronary angiography for the diagnosis of significant coronary stenoses in clinical practice.

BACKGROUND CT coronary angiography (CTA) with 64 slice multi-detector CT (64-MDCT) has assumed an increasing role in clinical practice; however the high radiation dose associated with retrospective ECG-gated CTA has led to suggestions that a low dose prospectively gated strategy may be more appropriate. This study aims to assess the feasibility of this proposed strategy amongst standard referral for CTA in our centre. METHODS We retrospectively analyzed 200 consecutive clinical CTA studies assessing the number of cardiac phases required to allow full diagnostic visualisation of the coronary tree. We assessed whether the pre-test likelihood of coronary disease, heart rate, heart rate variability and range, current beta-blockers use, coronary calcium score, breathing artefact or study quality affected the number of phases required. RESULTS 125/200 patients (62.5%) required only a single phase for full diagnostic visualisation of the coronary tree [most commonly 65% of the R-R interval-109/125 (87.2%)]. A successful diagnostic single cardiac phase was most likely in patients with a low heart rate (Heart rate < 70 bpm OR = 2.64; p = 0.003 and heart rate < 60 bpm OR = 4.81; p < 0.001 respectively) and low likelihood of coronary disease [OR = 1.97 95% CI (1.09, 3.58) p = 0.025]. CONCLUSION High image quality is possible using single phase analysis in those patients with low likelihood of coronary disease, low heart rates and full cooperation with inspiratory breath hold. In patients with HR of <60, prospective ECG-gated acquisitions reduce radiation dose but may be non-diagnostic in as many as one third. Careful patient selection is therefore essential.

Clinical management and short-term cost — 64-slice MDCT vs. myocardial perfusion scintigraphy

There are currently no published studies of the impact of CT coronary angiography (CTA) on patient management or cost when compared with other established imaging techniques. We assessed the short term investigation and treatment costs of CTA compared with myocardial perfusion scintigraphy (MPS) using real clinical scenarios. Clinical information with either their CTA or MPS results were presented to 20 cardiologists in a random order. They decided further investigations and treatment required based on these data. Short term cost was calculated for each imaging strategy. Whilst the total number of further investigations requested did not differ between groups patients undergoing CTA were more likely to be referred for invasive coronary angiography, receive aspirin, statins, ACE inhibitors, β-blockers or clopidogrel. Overall cost and investigation costs were similar between CTA and MPS; however treatment costs were higher with CTA. There are significant differences in further clinical management when using CTA compared with MPS, in particular with greater use of secondary preventative medication.

Defining myocardial infarction by cardiac computed tomography

Cardiac computed tomography (CCT) has been widely validated for the non-invasive diagnosis of coronary artery disease (CAD). Its value as a rule-out test is a function of the excellent and consistently demonstrated negative predictive value of the technique [1–3]. However, a poorer positive predictive value with overestimation of coronary stenoses severity may limit its usefulness in those with established CAD [4]. A wealth of non-coronary information is available from the standard CT coronary angiography (CTA) dataset which may improve the ability of the technique to detect important CAD. Retrospective gating techniques permit functional assessment of the left ventricle which allows a more comprehensive cardiac evaluation [5]. The addition of functional myocardial assessment has proven useful for both myocardial perfusion scintigraphy (MPS) [6] and cardiovascular magnetic resonance imaging (CMR) [7] and it is likely that the same will hold true for CCT. Left ventricular ejection fraction and volumes obtained from CCT-derived data have been compared against transthoracic echocardiography [8], SPECT MPS [8, 9] and CMR [8, 10] with success. In addition to measurement of left ventricular function, assessment of resting myocardial viability is of fundamental value when planning treatment strategy [11, 12]. Progress over the last few years in the detection of myocardial scarring by CCT has been steady. Interest has been focussed mainly in the acute setting, with two techniques for the detection of myocardial infarction (MI) proposed. The first method, underpinning the study in this edition by Mahnken et al. [13], involves evaluation of the pattern of myocardial attenuation on images obtained from the standard CTA dataset. Data acquired during the arterial phase of contrast injection results in contrast enhancement of normal myocardium. Within areas of myocardial scar, altered microvascular kinetics and reduced functional capillary density lead to delayed wash-in of contrast and hence hypoattenuation, with a resultant decrease in mean attenuation compared to healthy myocardium. This phenomenon provides, therefore, a suitable means of identifying MI. Indeed, hypoattenuation corresponding to MI has been identified even on single-slice CT acquisitions [14]. More recently, the presence of segmental hypoattenuation on CCT in patients with MI has been shown to correlate with the likelihood of functional recovery in that segment [15]. However, infarcted segments may be difficult to appreciate, especially where the signalto-noise ratio is low or the infarct size is small. Furthermore, early hypoattenuation may not be specific for known infarction except in the presence of abnormal wall motion and thickening in the same area J. Stirrup (&) S. R. Underwood Department of Nuclear Medicine, Royal Brompton Hospital, Sydney Street, London, SW3 6NP, UK e-mail: j.stirrup@rbht.nhs.uk

Inducible myocardial ischaemia diagnosed using computed tomography dipyridamole stress myocardial perfusion technique

Improved multi‐detector computed tomography (MDCT) temporal and spatial resolution allows for the assessment of coronary artery disease, left ventricular systolic function and resting myocardial perfusion defects with high sensitivity and specificity. Here we present a case using a novel combination technique of cardiac computed tomography scanning with dipyridamole stress for the detection of functionally significant coronary disease, and demonstrate that dipyridamole‐induced myocardial ischaemia is both detectable and quantifiable by cardiac MDCT.

Diagnostic Accuracy of 64-Slice Computed Tomography Coronary Angiography: A Flawed Comparison

We read with interest the recent paper by Meijboom et al. ([1][1]) and the corresponding editorial by Nissen ([2][2]). We wish to make 3 comments. First, as with almost all previous validation studies comparing computed tomography coronary angiography (CTCA) with invasive coronary angiography (ICA