What is the best contrast injection protocol for 64-row multi-detector cardiac computed tomography?

Prevalence and characteristics of intramural coronary artery in hypertrophic obstructive cardiomyopathy: a coronary computed tomography and invasive angiography study

Background

The prevalence and morphologic characteristics of intramural coronary artery (ICA) in patients with hypertrophic obstructive cardiomyopathy (HOCM) have yet to be fully illuminated. Our study aimed to investigate the prevalence and morphologic characteristics of ICA in patients with HOCM using coronary computed tomography (CT) angiography and invasive coronary angiography.

Methods

Patients with a diagnosis of HOCM who were admitted for selective myectomy in Fuwai Hospital were prospectively enrolled between September 2015 and June 2019. Both preoperative coronary CT and invasive angiography were scheduled for all participants.

Results

Coronary CT angiography detected ICA in 106 (23.3%) out of 455 patients. Dynamic compression of coronary arteries was observed in 87 patients (19.1%) by invasive coronary angiography. We found ICA covered with complete myocardial encasement in 98 patients (92.5%), with deep myocardial bridging (MB) observed most frequently (P=0.005). All patients with dynamic compression of coronary arteries had ICA. Dynamic luminal reduction ≥50% was present in 77 (16.9%) of the study participants. Pearson's correlation analysis revealed that the length and degree of dynamic compression were significantly related with MB length and depth (Pearson's correlation r=0.241, 0.581, 0.316, and 0.209; P=0.014, <0.001, 0.002, and 0.032, respectively).

Conclusions

Patients with HOCM commonly present with ICA and it can be visualized well by coronary CT angiography. Deep or extensive MB is more likely to produce coronary artery dynamic compression. Preoperative identification of this congenital coronary artery variant may be helpful for surgical planning.

Multimodality cardiac computed tomography angiography and magnetic resonance with clinical-grade scanners provide robust assessment of cardiac morphology and function in rabbits

Background

Non-invasive computer tomography (CT)- and magnetic resonance (MR)-based cardiac imaging still remains challenging in rodents. To investigate the robustness of non-invasive multimodality cardiac imaging in rabbits using clinical-grade CT and MR scanners.

Methods

A total of 16 rabbits (2.7-4.0 kg) serially underwent cardiac-gated imaging using a clinical-grade 256-row CT and a 1.5 Tesla MR-scanner at baseline and at 4-month follow-up (16±1 weeks). Image analysis included image quality (5-grade scale), left ventricular (LV) volumes, LV stroke volume, LV diameters, LV wall thickness and ejection fraction (LVEF).

Results

Cardiac MR (CMR) and CT angiography (CTA) provide images with an overall good image quality (excellent or good quality: CMR 82% vs. CTA 78%, P=0.68). Linear regression analysis demonstrated a good correlation of all diameters (diam.) and volumes (vol.) as assessed by CTA and CMR (diam.: r=0.9, 95% CI: 0.8-0.9; vol.: r=0.8, 95% CI: 0.6-0.9; P<0.0001 for both). CTA-based volumetric analysis revealed slightly higher LVEF values as compared to CMR (CTA: 64%±1%, CMR: 59%±1%, P=0.002). Analysis of inter-/intra-observer agreement demonstrated excellent agreements for diameters (CMR: 98.5%/98.7%; CTA: 98.2%/97.4%) and volumes (CMR: 99.9%/98.8%; CTA 98.7%/98.7%). Finally, serial CMR- and CTA-based assessment of cardiac diameters and volumes delivered excellent intersession agreements of baseline versus follow-up data (diam.: CMR: r=0.89; CTA: r=0.92; vol.: CMR: r=0.87; CTA: r=0.96, P<0.0001 for all).

Conclusions

Multimodality non-invasive assessment of cardiac function and aortic hemodynamics is feasible and robust in rabbits using clinical-grade and MR and CT scanners. These imaging modalities could improve serial cardiac assessment for disease monitoring in preclinical settings.

Combined prospectively electrocardiography- and respiratory-triggered sequential cardiac computed tomography in free-breathing children: success rate and image quality

BACKGROUND

Combined prospectively electrocardiography (ECG)- and respiratory-triggered sequential cardiac computed tomography (CT) has not been evaluated in free-breathing children.

OBJECTIVE

To evaluate the success rate and image quality of combined prospectively ECG- and respiratory-triggered sequential cardiac CT in free-breathing children.

MATERIALS AND METHODS

Image quality of combined prospectively ECG- and respiratory-triggered sequential cardiac CT in 870 children (≤5 years of age) was evaluated in terms of severe motion (maximal distance ≥2 mm) and band artifacts (maximal attenuation difference ≥100 Hounsfield units). The success rate of the scan mode was calculated. The causes of failed cases were assessed. Patient-related, radiation and image quality parameters were compared between success and failure groups.

RESULTS

Severe motion artifacts were observed in 10.6% (92/870) of patients due to cardiac phase error in 17 (18.5%), patient motion in 12 (13.0%), and unknown causes in 63 (68.5%). Severe band artifacts were seen in 13.2% (115/870) of patients. Combined prospectively ECG- and respiratory-triggered sequential cardiac CT was successfully performed in 78.5% (683/870) of patients, while it failed in 21.5% (187/870). All the evaluated patient-related, radiation and image quality parameters were significantly different (P≤0.001) between success and failure groups except effective dose (P>0.05).

CONCLUSION

Additional prospective respiratory triggering can reduce motion artifacts in prospectively ECG-triggered sequential cardiac CT in free-breathing children.

Myocardial Assessment with Cardiac CT: Ischemic Heart Disease and Beyond

PURPOSE OF REVIEW

The aim of this review is to highlight recent advancements, current trends, and the expanding role for cardiac CT (CCT) in the evaluation of ischemic heart disease, nonischemic cardiomyopathies, and some specific congenital myocardial disease states.

RECENT FINDINGS

CCT is a highly versatile imaging modality for the assessment of numerous cardiovascular disease states. Coronary CT angiography (CCTA) is now a well-established first-line imaging modality for the exclusion of significant coronary artery disease (CAD); however, CCTA has modest positive predictive value and specificity for diagnosing obstructive CAD in addition to limited capability to evaluate myocardial tissue characteristics.

SUMMARY

CTP, when combined with CCTA, presents the potential for full functional and anatomic assessment with a single modality. CCT is a useful adjunct in select patients to both TTE and CMR in the evaluation of ventricular volumes and systolic function. Newer applications, such as dynamic CTP and DECT, are promising diagnostic tools offering the possibility of more quantitative assessment of ischemia. The superior spatial resolution and volumetric acquisition of CCT has an important role in the diagnosis of other nonischemic causes of cardiomyopathies.

The effect of four-phasic versus three-phasic contrast media injection protocols on extravasation rate in coronary CT angiography: a randomized controlled trial

Objectives

Contrast media (CM) extravasation is a well-known complication of CT angiography (CTA). Our prospective randomized control study aimed to assess whether a four-phasic CM administration protocol reduces the risk of extravasation compared to the routinely used three-phasic protocol in coronary CTA.

Methods

Patients referred to coronary CTA due to suspected coronary artery disease were included in the study. All patients received 400 mg/ml iomeprol CM injected with dual-syringe automated injector. Patients were randomized into a three-phasic injection-protocol group, with a CM bolus of 85 ml followed by 40 ml of 75%:25% saline/CM mixture and 30 ml saline chaser bolus; and a four-phasic injection-protocol group, with a saline pacer bolus of 10 ml injected at a lower flow rate before the three-phasic protocol.

Results

2,445 consecutive patients were enrolled (mean age 60.6 ± 12.1 years; females 43.6%). Overall rate of extravasation was 0.9% (23/2,445): 1.4% (17/1,229) in the three-phasic group and 0.5% (6/1,216) in the four-phasic group (p = 0.034).

Conclusions

Four-phasic CM administration protocol is easy to implement in the clinical routine at no extra cost. The extravasation rate is reduced by 65% with the application of the four-phasic protocol compared to the three-phasic protocol in coronary CTA.

Key Points

• Four-phasic CM injection-protocol reduces extravasation rate by 65% compared to three-phasic.

• The saline pacer bolus substantially reduces the risk of CM extravasation.

• The implementation of four-phasic injection-protocol is at no cost.

Practical considerations for optimizing cardiac computed tomography protocols for comprehensive acquisition prior to transcatheter aortic valve replacement

Transcatheter aortic valve replacement (TAVR) is performed frequently in patients with severe, symptomatic aortic stenosis who are at high risk or inoperable for open surgical aortic valve replacement. Computed tomography angiography (CTA) has become the gold standard imaging modality for pre-TAVR cardiac anatomic and vascular access assessment. Traditionally, cardiac CTA has been most frequently used for assessment of coronary artery stenosis, and scanning protocols have generally been tailored for this purpose. Pre-TAVR CTA has different goals than coronary CTA and the high prevalence of chronic kidney disease in the TAVR patient population creates a particular need to optimize protocols for a reduction in iodinated contrast volume. This document reviews details which allow the physician to tailor CTA examinations to maximize image quality and minimize harm, while factoring in multiple patient and scanner variables which must be considered in customizing a pre-TAVR protocol.

Current utilization of cardiac computed tomography in mainland China: A national survey

BACKGROUND

Surveys that describe the utilization of cardiac CT are available for the United States, Germany, and Taiwan, but not mainland China.

OBJECTIVES

To analyze the clinical utilization of cardiac CT in mainland China.

METHODS

A 25-item questionnaire was created and 240 tertiary hospitals were randomly selected to participate. Survey data were collected and confirmed by email as well as phone interviews.

RESULTS

In total, 237 (99%) hospitals consented to this survey, but 85 were excluded because of lack of cardiac CT patient volume or advanced technology. Finally, 152 (64%) questionnaires were available for analysis. Median patient volume was 1,037 patients (range: 150-8,072) annually. The most common clinical indications for coronary CT angiography were exclusion of coronary artery disease in patients with low to intermediate pretest likelihood, asymptomatic individuals with cardiovascular risk factors, and follow-up after coronary bypass grafting. The median heart rate threshold for beta blocker administration was >70 beats/min; most centers (86%) used sublingual nitroglycerin. Prospectively ECG triggered acquisition was the predominant technique in 44% of hospitals. Most (59%) providers adjusted the tube current to the body mass, but few (16%) adjusted the contrast injection rate. Per case, the mean examination duration was 14.2 min; post-processing time 13.6 min; and reporting time 18.0 min.

CONCLUSIONS

Cardiac CT is widely established in clinical practice in mainland China but there is a need for more uniform standards regarding performance and clinical utilization.

The 9p21 locus is associated with coronary artery disease and cardiovascular events in the presence (but not in the absence) of coronary calcification

Variants at the 9p21 locus have been associated with coronary artery disease (CAD); coronary artery calcification (CAC) is related to CAD and other cardiovascular events. To determine the association of the 9p21 locus with CAD in the presence and absence of CAC, 4 groups were enrolled in a case-control study, including 527 CAD patients without CAC, 692 CAD patients with CAC, 585 individuals with simple CAC but no CAD, and 725 healthy controls. The rs1333049 representing the locus was associated with CAD in the presence of CAC (odds ratio = 1.38 in allelic analysis, 95%CI, 1.19–1.60, P<0.001), but not in the absence of CAC. Additionally, rs1333049 was not associated with simple CAC or CAC severity/extent in CAD patients with CAC. 849 CAD patients undergoing revascularization (660 with CAC and 189 without CAC) were enrolled in a cohort study to test its association with cardiovascular events in CAD patients with and without CAC in a 3-year follow-up. rs1333049 was significantly associated with the incidence of cardiovascular events in non-target vessels in patients with CAC (hazard ratio = 1.44, 95%CI, 1.08–1.91, P = 0.012), but not in those without CAC. The variants at the 9p21 locus were related to CAD and post-revascularization events only in the presence of CAC, suggesting that they may confer risk of calcification-related coronary atherosclerosis.

Common genetic variants of MGP are associated with calcification on the arterial wall but not with calcification present in the atherosclerotic plaques

BACKGROUND

Two endophenotypes of arterial calcification, calcification on arterial wall and calcification in atherosclerotic plaques, are associated with different types of cardiovascular events. Mgp-deficient mice showed matrix Gla protein (MGP) is strongly associated with calcification on arterial wall without atherosclerotic plaques, and MGP variants were not significantly associated with myocardial infarction. MGP may play different roles in the 2 endophenotypes.

METHODS AND RESULTS

We analyzed the associations of MGP variants rs4236, rs1800801, and rs1800802 with the 2 endophenotypes determined by multidetector computed tomography angiography. A total of 585 with calcification on coronary artery wall, 675 with calcification in coronary atherosclerotic plaques, 454 with calcification on aortic wall, and 725 controls were enrolled. After Bonferroni correction, rs4236 and rs1800801 were still associated with calcification on arterial wall, the odds ratios were 0.708 (95% confidence interval, 0.540-0.928) for rs4236 and 0.652 (95% confidence interval, 0.479-0.888) for rs1800801 in coronary artery wall calcification, and 0.699 (95% confidence interval, 0.525-0.931) for rs4236 and 0.650 (95% confidence interval, 0.467-0.905) for rs1800801 in aortic wall calcification, respectively. The variants were correlated with calcification severity by ln(CAC Agatston score+1) in coronary artery wall calcification but not in atherosclerotic plaque calcification. In accordance with their associations with calcification on arterial wall, rs4236C and rs1800801A were associated with higher MGP plasma levels, whereas rs1800802C was associated with lower MGP levels in normal controls. Because of the role of calcification in plaque vulnerability, their associations with acute myocardial infarction were also determined in 771 controls and 752 patients, no association was found.

CONCLUSIONS

MGP genetic variants showed association with calcification on arterial wall but not with calcification in atherosclerotic plaques.

Promoter variants of VTN are associated with vascular disease

BACKGROUND

Vitronectin is involved in the whole process of atherosclerosis. Our aim is to determine the association of VTN functional promoter variants with different types of vascular disease, and conclude the roles of vitronectin involved in vascular disease.

METHODS

Gel shift assays and luciferase reporter assays were used to determine the impact of variants on promoter activity. The correlation of plasma vitronectin levels with the variant was assessed in normal controls. The association of the variant with vascular disease was determined in 3 case-control studies.

RESULTS

A strong linkage disequilibrium was found between rs2227721 and rs2227720 in VTN promoter in Chinese (r(2)=1.0). Both variants resulted in a decreased transcription activity, and rs2227721 decreased the binding efficiency of transcription factor YY1 to the region. The rs2227721 was correlated with plasma vitronectin levels in normal controls (r=-0.207, P=0.028). The rs2227721 was associated with susceptibility of vascular disease; the odds ratios among subjects carrying rs2227721-T allele were 1.298 (95% Confidence Interval-CI, 1.033-1.631) for non-MI CAD (P<0.05), 1.346 (95% CI, 1.068-1.695) for chronic MI (P<0.05), 1.486 (95% CI, 1.145-1.928) for acute MI (P<0.001), and 1.619 (95% CI, 1.108-2.366) for deep venous thrombosis (P<0.05).

CONCLUSION

VTN promoter haplotype would be a novel genetic marker for vascular disease.

Right heart on multidetector CT

Right ventricular function plays an integral role in the pathogenesis and outcome of many cardiovascular diseases. Imaging the right ventricle has long been a challenge because of its complex geometry. In recent years there has been a tremendous expansion in multidetector row CT (MDCT) and its cardiac applications. By judicious modification of contrast medium protocol, it is possible to achieve good opacification of the right-sided cardiac chambers, thereby paving the way for exploring the overshadowed right heart. This article will describe the key features of right heart anatomy, review MDCT acquisition techniques, elaborate the various morphological and functional information that can be obtained, and illustrate some important clinical conditions associated with an abnormal right heart.

VKORC1 rs2359612C allele is associated with increased risk of coronary artery disease in the presence of coronary calcification

VKORC1 genetic polymorphisms affect warfarin dose response, aortic calcification, and the susceptibility of coronary artery disease as shown in our previous study. Little is known regarding the association of VKORC1 polymorphisms with coronary artery calcification (CAC) and the role of CAC in the association with coronary artery disease (CAD). Due to a natural haplotype block in the VKORC1 gene in Chinese, polymorphism rs2359612 was analyzed in a case-control study and a prospective study. The case-control study included 464 CAD patients with non-calcified plaque (NCP), 562 CAD patients with mixed calcified plaque (MCP), 492 subjects with calcified plaque (CP), and 521 controls. The rs2359612C was only associated with increased risk of MCP, the CAD in the presence of CAC; the odds ratio was 1.397 (95 % CI 1.008-1.937, P < 0.05), which was replicated in the second independent population. On the contrary, a negative correlation was observed between rs2359612 and log-transformed Agatston score, and rs2359612 was negatively associated with the number of calcified vessels. Moreover, in a prospective study including 849 CAD patients undergoing revascularization, rs2359612C predicted a higher incidence of cardiovascular events in MCP subgroup; the relative risk was 1.435 (95 % CI 1.008-2.041, P = 0.045), which was not observed in the NCP subgroup. We conclude that the rs2359612C was associated with a higher risk of CAD in the presence of CAC and a higher incidence of cardiovascular events in CAD patients with CAC, but a lower coronary calcification. VKORC1 polymorphisms may be associated with the endophenotype of CAD, calcification-related atherosclerosis.

Coronary enhancement for prospective ECG-gated single R-R axial 320-MDCT angiography: comparison of 60- and 80-mL iopamidol 370 injection

OBJECTIVE

The objective of our study was to evaluate the difference in coronary enhancement provided by 60 versus 80 mL of contrast medium (370 mg I/mL) for prospectively ECG-gated single-heartbeat axial 320-MDCT.

MATERIALS AND METHODS

We retrospectively evaluated 108 consecutive 320-MDCT angiography studies. Group 1 (n = 36) received 60 mL of an iodinated contrast medium and group 2 (n = 72), 80 mL. All patients were imaged with a standardized protocol: iopamidol 370 followed by 40 mL of saline, both administered at a rate of 6 mL/s. Two imagers subjectively assessed image quality throughout the coronary arteries. Region-of-interest attenuation (HU) measurements were performed in the aorta plus the proximal and distal coronary arteries.

RESULTS

Subjective analysis of all coronary segments showed slightly better image quality for group 2. Patients in group 1 had significantly (p < 0.05) lower mean attenuation values for the individual coronary vessels. Nevertheless, 96.7% of all coronary segments in the group 1 patients had an attenuation of greater than 300 HU; when analysis was limited to group 1 patients with a body mass index of greater than 30, 92.8% of the segments were more than 300 HU, and all segments measured more than 250 HU.

CONCLUSION

An injection protocol based on 60 mL of iopamidol (370 mg I/mL) for prospectively ECG-gated wide-area detector single-heartbeat coronary CT angiography (CTA) has less coronary enhancement than a protocol based on 80 mL. However, using 60 mL, more than 96% of coronary segments had sufficient enhancement (i.e., > 300 HU), supporting the general use of 60-mL protocols for clinical wide-area detector coronary CTA.

Dual-enhanced cardiac CT for detection of left atrial appendage thrombus in patients with stroke: a prospective comparison study with transesophageal echocardiography

BACKGROUND AND PURPOSE

A noninvasive method with high reliability and accuracy comparable to transesophageal echocardiography for identification of left atrial appendage thrombus would be of significant clinical value. The aim of this study was to assess the diagnostic performance of a dual-enhanced cardiac CT protocol for detection of left atrial appendage thrombi and for differentiation between thrombus and circulatory stasis in patients with stroke.

METHODS

We studied 83 consecutive patients with stroke (56 men and 27 women; mean age, 62.6 years) who had high risk factors for thrombus formation and had undergone both dual-source CT and transesophageal echocardiography within a 3-day period. CT was performed with prospective electrocardiographic gating, and scanning began 180 seconds after the test bolus.

RESULTS

Among the 83 patients, a total of 13 thrombi combined with spontaneous echo contrast and 14 spontaneous echo contrasts were detected by transesophageal echocardiography. All 13 thrombi combined with spontaneous echo contrast were correctly diagnosed on CT. Using transesophageal echocardiography as the reference standard, the overall sensitivity and specificity of CT for the detection of thrombi and circulatory stasis in the left atrial appendage were 96% (95% CI, 78% to 99%), and 100% (95% CI, 92% to 100%), respectively. On CT, the mean left atrial appendage/ascending aorta Hounsfield unit ratios were significantly different between thrombus and circulatory stasis (0.15 Hounsfield unit versus 0.27 Hounsfield unit, P=0.001). The mean effective radiation dose was 3.11 mSv.

CONCLUSIONS

Dual-enhanced cardiac CT with prospective electrocardiographic gating is a noninvasive and sensitive modality for detecting left atrial appendage thrombus with an acceptable radiation dose.

Cardiothoracic CT angiography: current contrast medium delivery strategies

OBJECTIVE

Over the last decade, rapid technologic evolution in CT has resulted in improved spatial and temporal resolution and acquisition speed, enabling cardiothoracic CT angiography to become a viable and effective noninvasive alternative in the diagnostic algorithm. These new technologic advances have imposed new challenges for the optimization of contrast medium delivery and image acquisition strategies.

CONCLUSION

Thorough understanding of contrast medium dynamics is essential for the design of effective acquisition and injection protocols. This article provides an overview of the fundamentals affecting contrast enhancement, emphasizing the modifications to contrast material delivery protocols required to optimize cardiothoracic CT angiography.

ASCI 2010 contrast media guideline for cardiac imaging: a report of the Asian Society of Cardiovascular Imaging cardiac computed tomography and cardiac magnetic resonance imaging guideline working group

The use of contrast media for cardiac imaging becomes increasing as the widespread of cardiac CT and cardiac MR. A radiologist needs to carefully consider the indication and the injection protocol of contrast media to be used as well as the possibility of adverse effect. There are several guidelines for contrast media in western countries. However, these are focusing the adverse effect of contrast media. The Asian Society of Cardiovascular Imaging, the only society dedicated to cardiovascular imaging in Asia, formed a Working Group and created a guideline, which summarizes the integrated knowledge of contrast media for cardiac imaging. In cardiac imaging, coronary artery evaluation is feasible by non-contrast MR angiography, which can be an alternative examination in high risk patients for the use of iodine contrast media. Furthermore, the body habitus of Asian patients is usually smaller than that of their western counterparts. This necessitates modifications in the injection protocol and in the formula for calculation of estimated glomerular filtration rate. This guideline provided fundamental information for the use of contrast media for Asian patients in cardiac imaging.