Cardiac CT angiography (CTA) and nuclear myocardial perfusion imaging (MPI)-a comparison in detecting significant coronary artery disease

The Role of Cardiac Computed Tomography in Heart Failure

PURPOSE OF REVIEW

Cardiac computed tomography (CT) is becoming a more widely applied tool in the diagnosis and management of a variety of cardiovascular conditions, including heart failure. The aim of this narrative review is to examine the role of cardiac CT in patients with heart failure.

RECENT FINDINGS

Coronary computed tomographic angiography has robust diagnostic accuracy for ruling out coronary artery disease. These data are reflected in updated guidelines from major cardiology organizations. New roles for cardiac CT in myocardial imaging, perfusion scanning, and periprocedural planning, execution, and monitoring are being implemented. Cardiac CT is useful in ruling out coronary artery disease its diagnostic accuracy, accessibility, and safety. It is also intricately linked to invasive cardiac procedures that patients with heart failure routinely undergo.

Diagnostic Accuracy of Noninvasive 64-row Computed Tomographic Coronary Angiography (CCTA) Compared with Myocardial Perfusion Imaging (MPI): The PICTURE Study, A Prospective Multicenter Trial

RATIONALE AND OBJECTIVES

Although multiple studies have shown excellent accuracy statistics for noninvasive angiography by coronary computed tomographic angiography (CCTA), most studies comparing nuclear imaging to CCTA were performed on patients already referred for cardiac catheterization, introducing referral and selection bias. This prospective trial evaluated the diagnostic accuracy of 64-row CCTA to detect obstructive coronary stenosis compared to myocardial perfusion imaging (MPI), using quantitative coronary angiography (QCA) as a reference standard.

MATERIALS AND METHODS

Twelve sites prospectively enrolled 230 patients (49% male, 57.8 years) with chest pain. All patients underwent MPI and CCTA (Lightspeed VCT/Visipaque 320, GE Healthcare, Milwaukee, WI, USA) prior to invasive coronary angiography (ICA). All patients were evaluated, and those found to have either an abnormal MPI or CCTA were clinically referred for ICA. CCTAs were graded on a 15-segment American Heart Association model by three blinded readers for presence of obstructive stenosis (>50% or >70%); MPI was graded by two blinded readers using a 17-segment model for estimation of the % myocardium ischemic or with stress defects. ICAs were independently graded for % stenosis by QCA. The efficacies of MPI and CCTA were assessed including all vessel segments for per-patient and per-vessel analyses.

RESULTS

The prevalence of stenosis ≥50% by ICA was 52.1% (25 of 48). The sensitivity of CCTA was significantly higher than nuclear imaging (92.0% vs 54.5%, P < 0.001), with similar specificity (87.0% vs 78.3%) when obstructive disease was defined as ≥50%. CCTA provided superior sensitivity (92.6% vs 59.3%, P < 0.001) and similar specificity (88.9% vs 81.5%) using QCA stenosis ≥70%. For ≥50% stenosis, the computed tomographic angiography odds ratio for ICA disease was 51.75 (95% CI = 8.50-314.94, P < 0.001). For summed stress score ≥5%, the odds ratio for ICA CAD was 12.73 (95% CI = 2.43-66.55, P < 0.001). Using receiver operating characteristic curve analysis, CCTA was better at classifying obstructive coronary artery disease when compared to MPI (area = 0.85 vs 0.71, P < 0.0001).

CONCLUSIONS

This study represents one of the first prospective multicenter, controlled clinical trials comparing 64-row CCTA to MPI in the same patients, demonstrating superior diagnostic accuracy of CCTA over myocardial perfusion single photon emission computed tomography (MPS) to reliably detect >50% and >70% stenosis in stable chest pain patients.

Assessment of coronary heart disease by CT angiography: current and evolving applications

Computed tomography angiography (CTA) of the heart is a rapidly evolving application for comprehensive assessment of coronary arterial anatomy, myocardial function, perfusion, and myocardial viability. Thus, cardiac CTA is capable of retrieving the most critical information for guiding the management of patients with suspected coronary heart disease (CHD). Ongoing technologic advancements have allowed acquiring such information within minutes, at radiation doses that are lower than those from conventional computed tomography imaging or common nuclear imaging techniques. Cardiac CTA has positioned itself as an imaging modality that may be well suited to fulfill central needs of cardiovascular medicine. This article reviews the evidence for the clinical utility of cardiac CTA in patients with suspected CHD.

Diagnostic performance of stress myocardial perfusion imaging for coronary artery disease: a systematic review and meta-analysis

Objectives

To determine and compare the diagnostic performance of stress myocardial perfusion imaging (MPI) for the diagnosis of obstructive coronary artery disease (CAD), using conventional coronary angiography (CCA) as the reference standard.

Methods

We searched Medline and Embase for literature that evaluated stress MPI for the diagnosis of obstructive CAD using magnetic resonance imaging (MRI), contrast-enhanced echocardiography (ECHO), single-photon emission computed tomography (SPECT) and positron emission tomography (PET).

Results

All pooled analyses were based on random effects models. Articles on MRI yielded a total of 2,970 patients from 28 studies, articles on ECHO yielded a sample size of 795 from 10 studies, articles on SPECT yielded 1,323 from 13 studies. For CAD defined as either at least 50 %, at least 70 % or at least 75 % lumen diameter reduction on CCA, the natural logarithms of the diagnostic odds ratio (lnDOR) for MRI (3.63; 95 % CI 3.26–4.00) was significantly higher compared to that of SPECT (2.76; 95 % CI 2.28–3.25; P = 0.006) and that of ECHO (2.83; 95 % CI 2.29–3.37; P = 0.02). There was no significant difference between the lnDOR of SPECT and ECHO (P = 0.52).

Conclusion

Our results suggest that MRI is superior for the diagnosis of obstructive CAD compared with ECHO and SPECT. ECHO and SPECT demonstrated similar diagnostic performance.

Key Points

• MRI can assess myocardial perfusion.

• MR perfusion diagnoses coronary artery disease better than echocardiography or SPECT.

• Echocardiography and SPECT have similar diagnostic performance.

• MRI can save coronary artery disease patients from more invasive tests.

• MRI and SPECT show evidence of publication bias, implying possible overestimation.

Electronic supplementary material

The online version of this article (doi:10.1007/s00330-012-2434-1) contains supplementary material, which is available to authorized users.

Stress testing and non-invasive coronary angiography in patients with suspected coronary artery disease: time for a new paradigm

Diagnosis and management of coronary artery disease represents major challenges to our health care system, affecting millions of patients each year. Until recently, the diagnosis of coronary artery disease was possible only through cardiac catheterization and invasive coronary angiography. To avoid the risks of an invasive procedure, stress testing is often employed for an initial assessment of patients with suspected coronary artery disease, serving as a gatekeeper for cardiac catheterization. With the emergence of non-invasive coronary angiography, the question arises if such a strategy is still sensible, particularly, in view of only a modest agreement between stress testing results and the presence of coronary artery disease established by cardiac catheterization. Much data in support of the diagnostic accuracy and prognostic value of non-invasive coronary angiography by computed tomography have emerged within the last few years. These data challenge the role of stress testing as the initial imaging modality in patients with suspected coronary artery disease. This article reviews the clinical utility, limitations, as well as the hazards of stress testing compared with non-invasive coronary artery imaging by computed tomography. Finally, the implications of this review are discussed in relation to clinical practice.

Predictive Values of Framingham Risk and Coronary Artery Calcium Scores in the Detection of Obstructive CAD in Patients with Normal SPECT

A subgroup of patients with normal stress myocardial perfusion imaging (MPI) have obstructive coronary artery disease (CAD) on coronary computed tomographic angiography (CCTA). A retrospective study was performed to identify factors associated with obstructive CAD in patients with normal MPI. Bivariate differences between patients with obstructive (>50% stenosis) and nonobstructive (<50% stenosis) CAD were assessed. Of the 105 patients with normal MPI, 42 (40%) had obstructive CAD on CCTA. After a multivariable logistic regression analysis increased Framingham risk scores ([FRS] ≥10%) and coronary artery calcium scores ([CACS] >100 Agatston Units [AU]) were independently associated with obstructive CAD ( P = .006 and P < .0001, respectively). Patients with normal MPI had 13 times and 98 times higher odds of having obstructive CAD if they had a FRS ≥10% versus <10% and CACS >100 AU versus ≤100 AU, respectively. Increased FRS and CACS may stratify patients who may benefit from further evaluation for significant CAD despite normal MPI.

Noninvasive anatomical coronary artery imaging versus myocardial perfusion imaging: which confers superior diagnostic and prognostic information?

Myocardial perfusion imaging (MPI) has been a valuable diagnostic and prognosticating tool for decades, but recently it has been challenged by the growing evidence about either comparable or superior diagnostic and prognostic value of computed tomography (CT)-based anatomical imaging modalities. Although there are some studies suggesting synergy and potential for combined use of these modalities to better diagnose coronary artery disease (CAD), it is important to evaluate these approaches separately, given cost and other restraints. This review compares the noninvasive anatomical imaging modalities of coronary artery calcium scoring and coronary CT angiography to the functional assessment modality of MPI in the diagnosis and prognostication of significant CAD in symptomatic patients. A large number of studies investigating this subject are analyzed with a critical look on the evidence, underlying the strengths and limitations. Although the overall findings of the presented studies are favoring the use of CT-based anatomical imaging modalities over MPI in the diagnosis and prognosticating of CAD, the lack of a high number of large- scale, multicenter randomized controlled studies limits the generalizability of this early evidence. Further studies comparing the short- and long-term clinical outcomes and cost-effectiveness of these tests are required to determine their optimal role in the management of symptomatic patients with suspected CAD.

Decision analytic model for evaluation of suspected coronary disease with stress testing and coronary CT angiography

RATIONALE AND OBJECTIVES

The aim of this study was to apply a decision analytic model for the evaluation of coronary artery disease (CAD) to define the optimal utilization of coronary computed tomographic angiography (cCTA) and stress testing.

MATERIALS AND METHODS

The model tested in this study assumes that CAD is evaluated with a stress test and/or cCTA and that a patient with positive evaluation results undergoes cardiac catheterization. On the basis of values of sensitivity, specificity, and radiation dose from the published literature and test costs from the Medicare fee schedule, a decision tree model was constructed as a function of disease prevalence.

RESULTS

The false-negative rate is lowest when cCTA is used as an isolated test. The false-positive rate is minimized when cCTA is used in combination with stress echocardiography. Effective radiation is minimized by use of stress electrocardiography or stress echocardiography alone or prior to cCTA. When the pretest probability of CAD is low, a strategy that uses stress echocardiography followed by cCTA minimizes the false-positive rate and effective radiation exposure, with relatively low imaging costs and with a false-negative rate only slightly higher than a strategy including stress myocardial scintigraphy. As the pretest probability of CAD increases above 20%, the false-negative rate of stress echocardiography followed by cCTA increases by >5% relative to cCTA alone.

CONCLUSION

Effective radiation dose and imaging costs for the workup of CAD may be minimized by an appropriate combination of stress testing and cCTA. A strategy that uses stress echocardiography followed by cCTA is most appropriate for the evaluation of low-risk patients with CAD with a pretest probability < 20%, while cCTA alone may be more appropriate in intermediate-risk patients.

Responsible use of computed tomography in the evaluation of coronary artery disease and chest pain

Many options are available to clinicians for the noninvasive evaluation of the cardiovascular system and patient concerns about chest discomfort. Cardiac computed tomography (CT) is a rapidly advancing field of noninvasive imaging. Computed tomography incorporates coronary artery calcium scoring, coronary angiography, ventricular functional analysis, and information about noncardiac thoracic anatomy. We searched the PubMed database and Google from inception to September 2009 for resources on the accuracy, risk, and predictive capacity of coronary artery calcium scoring and CT coronary angiography and have reviewed them herein. Cardiac CT provides diagnostic information comparable to echocardiography, nuclear myocardial perfusion imaging, positron emission tomography, and magnetic resonance imaging. A cardiac CT study can be completed in minutes. In patients with a nondiagnostic stress test result, cardiac CT can preclude the need for invasive angiography. Prognostic information portends excellent outcomes in patients with normal study results. Use of cardiac CT can reduce health care costs and length of emergency department stays for patients with chest pain. Cardiac CT examination provides clinically relevant information at a radiation dose similar to well-established technologies, such as nuclear myocardial perfusion imaging. Advances in technique can reduce radiation dose by 90%. With appropriate patient selection, cardiac CT can accurately diagnose heart disease, markedly decrease health care costs, and reliably predict clinical outcomes.

The role of calcium score and CT angiography in the medical management of patients with normal myocardial perfusion imaging

BACKGROUND

Individuals with normal myocardial perfusion imaging (MPI) may still have substantial coronary artery disease (CAD), which would benefit from aggressive medical therapy. The role of coronary artery calcium-score (CAC) and/or coronary CT Angiography (CTA) to identify additional treatment candidates in this population is unknown.

METHODS

Ninety-four patients completed the study protocol and underwent CAC and CTA after MPI.

RESULTS

In 81 patients who had a normal MPI, an algorithm using the clinical predictors, CAC, and then CTA was created to identify candidates for aggressive medical management; 24/81 patients had a high Framingham Risk Score (FRS) or diabetes, and need aggressive medical management, while 6/81 patients had a low FRS and low post-MPI probability of CAD. The use of CAC in 51/81 patients with intermediate clinical predictors would identify 23/51 patients with low risk (CAC < 100) and 11/51 patients (CAC > 400) for aggressive medical management. The remaining 17/51 patients with intermediate CAC scores (100-399) would require CTA, of which, would identify 8/17 additional patients with >50% stenosis for aggressive medical therapy.

CONCLUSION

A stepwise approach including history, CAC and CTA can identify about 50% of the patients with normal MPI who have a higher risk and may benefit from aggressive medical management.

Computer assistance for solving imaging problems

Medical imaging has moved into an era of digital files and processing of images to yield three-dimensional models and reconstructions. This development has opened up opportunities to apply computer techniques in traditional imaging tasks. Two of the most common imaging tasks are those to correct the two-dimensional projection problems of foreshortening of lesions and of vessel overlap. This article explores the use of computers to assist in these tasks, to create databases for guiding decision making, to provide graphics to assist the physician, and to simulate cardiovascular procedures.

Diagnostic and prognostic value of absence of coronary artery calcification

OBJECTIVES

In this study, we systematically assessed the diagnostic and prognostic value of absence of coronary artery calcification (CAC) in asymptomatic and symptomatic individuals.

BACKGROUND

Presence of CAC is a well-established marker of coronary plaque burden and is associated with a higher risk of adverse cardiovascular outcomes. Absence of CAC has been suggested to be associated with a very low risk of significant coronary artery disease, as well as minimal risk of future events.

METHODS

We searched online databases (e.g., PubMed and MEDLINE) for original research articles published in English between January 1990 and March 2008 examining the diagnostic and prognostic utility of CAC.

RESULTS

A systematic review of published articles revealed 49 studies that fulfilled our criteria for inclusion. These included 13 studies assessing the relationship of CAC with adverse cardiovascular outcomes in 64,873 asymptomatic patients. In this cohort, 146 of 25,903 patients without CAC (0.56%) had a cardiovascular event during a mean follow-up period of 51 months. In the 7 studies assessing the prognostic value of CAC in a symptomatic population, 1.80% of patients without CAC had a cardiovascular event. Overall, 18 studies demonstrated that the presence of any CAC had a pooled sensitivity and negative predictive value of 98% and 93%, respectively, for detection of significant coronary artery disease on invasive coronary angiography. In 4,870 individuals undergoing myocardial perfusion and CAC testing, in the absence of CAC, only 6% demonstrated any sign of ischemia. Finally, 3 studies demonstrated that absence of CAC had a negative predictive value of 99% for ruling out acute coronary syndrome.

CONCLUSIONS

On the basis of our review of more than 85,000 patients, we conclude that the absence of CAC is associated with a very low risk of future cardiovascular events, with modest incremental value of other diagnostic tests in this very low-risk group.

Combined assessment of coronary anatomy and myocardial perfusion using multidetector computed tomography for the evaluation of coronary artery disease

Multidetector computed tomography (MDCT) is increasingly used as an alternative to invasive coronary angiography. Although computed tomographic coronary angiography (CTCA) has been validated against invasive coronary angiography and nuclear myocardial perfusion imaging, the potential of MDCT to evaluate perfusion has not been fully explored. We sought to (1) develop a new technique for quantitative assessment of myocardial enhancement based on analysis of MDCT images acquired for CTCA, (2) identify the underlying causes of myocardial hypoenhancement detected by MDCT, and (3) determine the added diagnostic value of the MDCT perfusion index when combined with CTCA. We studied 84 patients undergoing clinical CTCA (64 patients with invasive coronary angiogram and a control group of 20 patients). MDCT perfusion index was calculated from x-ray attenuation measured in 16 myocardial segments. Hypoenhancement was automatically detected using comparisons with the normal range obtained in the control group, and its added value was determined against invasive coronary angiographic findings combined with known previous myocardial infarction. Myocardial hypoenhancement was detected in 29 of 64 patients in 47 vascular territories, of which 36 (77%) were abnormal by the reference technique. Of these 36 abnormalities, 10 (28%) were associated with previous myocardial infarction, whereas 26 (72%) corresponded to significant coronary stenosis. The addition of MDCT perfusion index to CTCA improved its diagnostic accuracy (sensitivity 0.87 to 0.96, accuracy 0.84 to 0.88, despite a decrease in specificity 0.79 to 0.68). In conclusion, myocardial hypoenhancement is a potentially valuable addition to MDCT evaluation of coronary artery disease without additional cost in radiation dose or contrast load.

International, multidisciplinary update of the 2006 Appropriateness Criteria for cardiac computed tomography

BACKGROUND

A multi-society document outlining appropriateness criteria for cardiac CT (CCT) was published in 2006. Since then, CCT has experienced rapid growth in technologic advances and clinical use. We sought to reassess opinion about the appropriate use of CCT among an international group of experts in the field.

METHODS

Seventy-two international experts in the field of CCT independently rated all 39 indications listed in the original 2006 appropriateness statement. Indications were classified as either "appropriate," "uncertain," or "inappropriate" based on an assessment of the clinical balance between risk and benefit to the patient in daily practice. Median rater scores were considered to represent current opinion for each indication and were compared with the original value in the 2006 document.

RESULTS

Survey respondents averaged 5.8+/-4.1 years of CCT experience, with a median total of 1200 contrast-enhanced CCT examinations performed and interpreted. Cardiologists (40; 55.6%) and radiologists (32; 44.4%) were included. Five of 12 previously "uncertain" indications shifted to "appropriate," resulting in a total of 18 "appropriate" of 39 possible indications. Conversely, all previously "appropriate" indications remained so. Among the 14 previously "inappropriate" indications, 10 shifted to "uncertain," none to "appropriate." Overall, 26 of 39 indications showed increased appropriateness scores (range of shift, 1-4 points; median value, 1; interquartile range, 0-2). No significant differences were observed between US and non-US expert respondents or between cardiology and radiology respondents in the overall appropriateness category ratings.

CONCLUSIONS

When compared with the 2006 Appropriateness Criteria, opinion regarding clinical use of CCT has experienced a significant shift toward appropriateness across most indications, similarly judged among international cardiology and radiology experts in the field.

Value of multidetector computed tomography evaluation of myocardial perfusion in the assessment of ischemic heart disease: comparison with nuclear perfusion imaging

MDCT-derived myocardial perfusion has not yet been validated against accepted standards. We developed a technique for quantification of myocardial perfusion from MDCT images and studied its diagnostic value against SPECT myocardial perfusion imaging (MPI). Ninety-eight patients were studied. Abnormal perfusion was detected by comparing normalized segmental x-ray attenuation against values obtained in 20 control subjects. Disagreement with resting MPI was investigated in relationship to MDCT image quality, severity of MPI abnormalities, and stress MPI findings. Resting MPI detected mild or worse abnormalities in 20/78 patients. MDCT detected abnormalities in 15/20 patients (sensitivity of 0.75). Most abnormalities missed by MDCT analysis were graded as mild on MPI. Additional abnormalities found in 16/78 patients were not confirmed on resting MPI (specificity of 0.72). However, 8 of these 16 apparently false positive MDCT perfusion tests had abnormal stress MPI; of these 8 patients, 7 had optimal MDCT image quality, while in 6/8 remaining patients, image quality was suboptimal. When compared with resting MPI, MDCT detected perfusion abnormalities with high accuracy. Moreover, half of MDCT perfusion abnormalities not confirmed by resting MPI were associated with abnormal stress MPI. Importantly, this information can be obtained without additional radiation dose or contrast agent.

Diagnostic performance of 64-multidetector row coronary computed tomographic angiography for evaluation of coronary artery stenosis in individuals without known coronary artery disease: results from the prospective multicenter ACCURACY (Assessment by Coronary Computed Tomographic Angiography of Individuals Undergoing Invasive Coronary Angiography) trial

OBJECTIVES

The purpose of this study was to evaluate the diagnostic accuracy of electrocardiographically gated 64-multidetector row coronary computed tomographic angiography (CCTA) in individuals without known coronary artery disease (CAD).

BACKGROUND

CCTA is a promising method for detection and exclusion of obstructive coronary artery stenosis. To date, no prospective multicenter trial has evaluated the diagnostic accuracy of 64-multidetector row CCTA in populations with intermediate prevalence of CAD.

METHODS

We prospectively evaluated subjects with chest pain at 16 sites who were clinically referred for invasive coronary angiography (ICA). CCTAs were scored by consensus of 3 independent blinded readers. The ICAs were evaluated for coronary stenosis based on quantitative coronary angiography (QCA). No subjects were excluded for baseline coronary artery calcium score or body mass index.

RESULTS

A total of 230 subjects underwent both CCTA and ICA (59.1% male; mean age: 57 +/- 10 years). On a patient-based model, the sensitivity, specificity, and positive and negative predictive values to detect > or =50% or > or =70% stenosis were 95%, 83%, 64%, and 99%, respectively, and 94%, 83%, 48%, 99%, respectively. No differences in sensitivity and specificity were noted for nonobese compared with obese subjects or for heart rates < or =65 beats/min compared with >65 beats/min, whereas calcium scores >400 reduced specificity significantly.

CONCLUSIONS

In this prospective multicenter trial of chest pain patients without known CAD, 64-multidetector row CCTA possesses high diagnostic accuracy for detection of obstructive coronary stenosis at both thresholds of 50% and 70% stenosis. Importantly, the 99% negative predictive value at the patient and vessel level establishes CCTA as an effective noninvasive alternative to ICA to rule out obstructive coronary artery stenosis. (A Study of Computed Tomography [CT] for Evaluation of Coronary Artery Blockages in Typical or Atypical Chest Pain; NCT00348569).

Head-to-head comparison of dobutamine stress echocardiography and cardiac computed tomography for the detection of significant coronary artery disease

OBJECTIVES

Dobutamine stress echocardiography (DSE) and contrast-enhanced electron beam tomography (EBCT) both have the potential to noninvasively detect coronary artery disease (CAD). We compared the accuracy of both methods to detect significant CAD in a direct comparison.

METHODS

79 patients (32 women, 47 men, mean age 62 years) who were admitted for coronary angiography due to suspected CAD were studied. By EBCT coronary calcification (CAC) as well as angiography (CTA) was assessed. Presence of significant CAD was assumed if the calcium score exceeded 400 or the contrast-enhanced images displayed significant lumen reduction. DSE was performed using a standard protocol (5-40 microg/kg/min dobutamine plus 0.25-1.0 mg atropine if necessary). DSE and EBCT were independently evaluated concerning the presence of significant CAD. Results were compared to invasive, quantitative coronary angiography.

RESULTS

6 patients (8%) in DSE and 2 patients (3%) in EBCT were unevaluable for various reasons and therefore excluded from further analysis. In the remaining 71 patients, 33 patients (46%) showed significant CAD. DSE demonstrated a sensitivity of 70% (23/33) and a specificity of 84% (32/38). EBCT showed a sensitivity of 91% (30/33) and a specificity of 74% (28/38). By combining DSE and EBCT sensitivity increased to 97% with a specificity of 63%.

CONCLUSIONS

In a blinded comparison, DSE demonstrated lower sensitivity but higher specificity than EBCT for the detection of significant CAD. Sensitivity was improved by combining both modalities.