Andrew J. Marshall

Highly accurate coronary angiography with submillimetre, 16 slice computed tomography

Objective: To assess submillimetre coronary computed tomographic angiography (CTA) in comparison with invasive quantitative coronary angiography as the gold standard and to examine the effect of significant coronary artery calcification (CAC), which is known to impede lumen visualisation, on the accuracy of the examination. Methods: After invasive coronary angiography, 58 patients underwent coronary imaging with a GE Lightspeed 16 computed tomography (CT) system. CAC was quantified after an ECG triggered acquisition with a low tube current. Coronary CTA was performed with retrospective ECG gating and a 16 × 0.63 mm collimation and was reconstructed with an effective 65–250 ms temporal resolution. All 13 major coronary artery segments were evaluated for the presence of ⩾ 50% stenosis, and compared with the gold standard. Results: One patient moved and could not be evaluated. All segments (except occluded segments) were evaluated for 57 patients. Overall the accuracy of coronary CTA for detection of ⩾ 50% stenosis was: sensitivity 83%, specificity 97%, positive predictive value 80%, and negative predictive value 97%. The number of diseased coronary arteries was correctly diagnosed in 34 of 38 (89%) patients overall. Altogether 21 of 57 (37%) patients had a CAC score ⩾ 400, which was predefined as representing significant CAC. Excluding these patients from the analysis improved the accuracy of coronary CTA to a sensitivity of 89%, specificity 98%, positive predictive value 79%, and negative predictive value 99%. Conclusions: Non-invasive coronary angiography with submillimetre CT is reliable and accurate. It appears that a subgroup of patients may be selected based on CAC score in whom the investigation has even higher accuracy. Coronary CTA has reached the stage where it should be considered for a clinical role. Further research is required to define this role.

Three dimensional volume quantification of aortic valve calcification using multislice computed tomography

Objective: To assess a new multislice computed tomography (CT) technique for three dimensional quantification of aortic valve calcification volume (3D AVCV) and to study the relation between stenosis and calcification of the aortic valve. Methods: 50 patients with echocardiographic calcification of the aortic valve underwent two separate ECG triggered multislice CT for quantification of 3D AVCV. The agreement between the two 3D AVCV scores was assessed and 3D AVCV was compared with echocardiographic markers of severity of aortic stenosis. Results: Overall the level of agreement between the two 3D AVCV scores was excellent (median interscan variability 7.9% (interquartile range 10.1); correlation coefficient, r = 0.99; repeatability coefficient 237.8 mm3 (limits of agreement −393 to 559 mm3)). However, the magnitude of the 3D AVCV did influence the interscan variability. The 3D AVCV correlated closely with the maximal predicted transvalvar gradient (r2 = 0.77) and aortic valve area (r2 = 0.73). Conclusions: Multislice CT provides a technique for quantifying 3D AVCV that has good reproducibility. There is a close non-linear relation between echocardiographic parameters of severity of valve stenosis and 3D AVCV scores.

Multidetector row computed tomography: imaging congenital coronary artery anomalies in adults

The quality of the imaging of the main coronary arteries and side branches provided by multidetector row computed tomography (MDCT) may have importance when assessing congenital coronary artery anomalies. This review discusses the rationale for using MDCT for this indication and examines the advantages and disadvantages of the technique. Examples of MDCT imaging of congenital coronary artery anomalies are presented. These images provide persuasive evidence to support clinical use of MDCT cardiac imaging in the context of suspected congenital coronary artery anomalies as a first line investigation.

Multislice Computed Tomographic Coronary Angiography: Experience in a UK Centre

AIMnTo evaluate the technique of coronary angiography with retrospectively electrocardiogram (ECG)-gated four-slice helical computed tomography (CT).nnnMATERIALS AND METHODSnWithin 1 month of undergoing routine day-case diagnostic coronary angiography, 30 consecutive patients also underwent retrospectively ECG-gated multislice CT coronary angiography. This enabled direct comparison of seven segments of proximal and mid-coronary artery for each patient by two blinded assessors. Each segment of coronary artery from the multislice CT image was evaluated initially for assessability and those segments deemed assessable were subsequently investigated for the presence or absence of a significantly (n=70%) stenotic lesion.nnnRESULTSnOverall 68% of proximal and mid-coronary artery segments were assessable. The sensitivity and specificity of four-slice CT coronary angiography in assessable segments for detecting the presence or absence (n=70%) of stenoses were 72 and 86%, respectively. These results correspond to a positive predictive value of 53% and a 93% negative predictive value. If the 32% of non-assessable segments are added into the calculation then the sensitivity and specificity fall to 49 and 66%, respectively.nnnCONCLUSIONnAlthough multislice CT coronary angiography is a promising technique, the overall assessability and diagnostic accuracy of four-slice CT acquisition is not sufficient to justify routine clinical use. Further, evaluation should investigate the benefit of the reduction in temporal and spatial resolution offered by 16 and 32 slice acquisition.

EVALUATION OF AN ULTRASONICALLY GUIDED VENEPUNCTURE TECHNIQUE FOR THE PLACEMENT OF PERMANENT PACING ELECTRODES

We have evaluated a method of puncturing the subclavian vein in its extrathoracic portion using on ultrasound guidance system. Seventy consecutive patients requiring permanent pacemakers were included in the study. The method was successful in 56 (80%) cases (23 dual chamber systems) and unsuitable or unsuccessful in 14 (20%) cases (2 dual chamber systems). The time taken to achieve a successful cannulation of the vein was similar to that taken with conventional subclavian Venepuncture (average time taken for each Venepuncture WAS 31 seconds, range 5–130 seconds). There was a significant “learning curve” in that nearly all of the unsuccessful cases were in the first half of the series. There were no major complications. Computerized Tomography (CT) confirms that the point of entry into the subclavian vein using this technique lies outside the thoracic cavity, thereby minimizing the risk of pneumothorax. This approach to the subclavian vein is an easy technique to learn, with few immediate complications and there maybe less chance of lead fracture due to subclavian crush in the longer term.

Refined computed tomography of the thoracic aorta: the impact of electrocardiographic assistance.

There have been a number of advances in helical computed tomography (CT) in recent years, which have had a beneficial impact on the quality of imaging of the thoracic aorta. These advances include sub-second gantry rotation, multislice acquisition, and the use of electrocardiographic (ECG) assistance. We examine these techniques with emphasis on the principles behind ECG assistance and its use to reduce aortic motion artefact. We highlight examples of ECG-assisted multislice CT in a spectrum of pathologies of the thoracic aorta.

Impaired left ventricular function has a detrimental effect on image quality in multi-detector row CT coronary angiography

AIMnTo determine whether there is a relationship between left ventricular (LV) haemodynamic parameters, circulation times, and arterial contrast opacification that might affect the image quality of computed tomography (CT) coronary angiography.nnnMETHODSnThirty-six patients were included in the study: 18 with cardiomyopathy (CM) and LV dilatation of suspected ischaemic aetiology [age 57.9+/-13.7 years, range 30-77 years; 14 male, four female; body mass index (BMI)=27.7+/-4.5, range 25.5-31.8] and 18 controls (age 62.3+/-9.4 years, range 47-89 years; 10 male, eight female; BMI 27.8+/-6.6; range 19.2-33.6). Coronary artery image quality was assessed using a three-point visual scale; contrast medium circulation times, aortic root contrast attenuation, and LV functional parameters were studied.nnnRESULTSnVisually reduced contrast opacification impaired image quality more often in the CM group than the control group (27.4 versus 5.1%). A total of 55.6% CM patients had a contrast transit time ranging from 30-75 s; the number of unassessable segments increased with increasing transit time conforming to a fitted quadratic model (R2=0.74). The relationship between LV ejection fraction and contrast attenuation may also conform to a quadratic model (R2=0.71).nnnCONCLUSIONnLV haemodynamics influence coronary artery opacification using cardiac CT, and users imaging this subgroup must do so with the knowledge of this potential pitfall. The results indicate the need for further studies examining CT protocols in this clinical subgroup.

Intramyocardial bridging of the left anterior descending artery: appearance of arterial compression on ECG gated multidetector row CT

A 38 year old man presented with a history of multiple hospital admissions with recurrent exertional related chest pain. On each occasion there was no elevation in cardiac troponin. Exercise stress testing revealed myocardial ischaemic change but coronary angiography failed to demonstrate underlying coronary disease although myocardial bridging of the left anterior descending artery (LAD) was suspected.nnECG gated …

Pacemaker Diagnostics to Determine Treatment and Outcome in Sick Sinus Syndrome with Paroxysmal Atrial Fibrillation

Sequential analysis of pacemaker diagnostics has been used to help manage the treatment and pacemaker program in patients who have sick sinus syndrome with documented paroxysmal atrial fibrillation. One hundred consecutive patients were followed for an average of 18 months. Knowledge of the atrial fibrillation burden led to major changes in medical management for half of the patients and changes to pacemaker programming for all. At the end of the study, 48 patients were free of arrhythmia with pacing although 14 required antiarrhythmic medication. We advocate using pacemaker diagnostics to improve patient management.

Tumor-Like Calcification of the Mitral Annulus: Diagnosis With Multislice Computed Tomography

An 83-year-old woman underwent transthoracic echocardiography (TTE) to assess her left ventricular systolic function. The TTE showed a large, round, echo-dense mass with central echo-lucencies resembling a posterior periannular tumor.nnThere was no associated mitral valvular dysfunction, and left ventricular function was good. Further assessment was performed using electrocardiographic-gated cardiac multislice computed tomography. This demonstrated that the mass seen on TTE was due to gross calcification of the posterior portion of …