Rationale and design of the ViCTORY (Validation of an Intracycle CT Motion CORrection Algorithm for Diagnostic AccuracY) trial

BACKGROUND

Coronary CT angiography (CTA) has emerged as an effective noninvasive method for direct visualization of the coronary arteries, with high diagnostic performance compared with invasive coronary angiography (ICA). However, coronary CTA is prone to artifacts, including coronary motion, which may reduce its diagnostic performance. Intracycle motion compensation algorithms (MCAs) from a combination of software and hardware techniques now allow for correction of coronary motion, but the diagnostic performance of MCAs compared with traditional coronary CTA reconstruction methods remains unexplored.

METHODS

ViCTORY (Validation of an Intracycle CT Motion CORrection Algorithm for Diagnostic AccuracY) is a prospective international multicenter trial of 218 patients which is designed to evaluate the performance of MCAs for the diagnosis of anatomically obstructive coronary artery disease (CAD) compared with an ICA reference standard, on a per-patient, per-vessel, and per-segment basis. Patients enrolled into ViCTORY will undergo investigational coronary CTA and clinically indicated ICA and will not receive heart rate-lowering medications before coronary CTA. Coronary CTA images will be reconstructed by conventional standard methods as well as by MCAs. Blinded core laboratory interpretation will be performed for coronary CTA and ICA in an intent-to-diagnose fashion.

RESULTS

The primary end point of ViCTORY is the per-patient diagnostic accuracy of MCAs for the diagnosis of anatomically obstructive CAD compared with ICA. Secondary end points will include other per-patient, per-vessel, and per-segment diagnostic performance characteristics, including accuracy, sensitivity, specificity, positive predictive value, and negative predictive value. Other key secondary end points will include diagnostic interpretability, image quality, the upper heart rate threshold of utility of MCAs, and the additive value of MCAs to traditionally reconstructed coronary CTA.

CONCLUSION

ViCTORY will determine whether MCAs improve the diagnosis of obstructive CAD in patients undergoing coronary CTA who are not receiving heart rate-lowering medications.

Aggregate plaque volume by coronary computed tomography angiography is superior and incremental to luminal narrowing for diagnosis of ischemic lesions of intermediate stenosis severity

OBJECTIVES

This study examined the performance of percent aggregate plaque volume (%APV), which represents cumulative plaque volume as a function of total vessel volume, by coronary computed tomography angiography (CTA) for identification of ischemic lesions of intermediate stenosis severity.

BACKGROUND

Coronary lesions of intermediate stenosis demonstrate significant rates of ischemia. Coronary CTA enables quantification of luminal narrowing and %APV.

METHODS

We identified 58 patients with intermediate lesions (30% to 69% diameter stenosis) who underwent invasive angiography and fractional flow reserve. Coronary CTA measures included diameter stenosis, area stenosis, minimal lumen diameter (MLD), minimal lumen area (MLA) and %APV. %APV was defined as the sum of plaque volume divided by the sum of vessel volume from the ostium to the distal portion of the lesion. Fractional flow reserve ≤ 0.80 was considered diagnostic of lesion-specific ischemia. Area under the receiver operating characteristic curve and net reclassification improvement (NRI) were also evaluated.

RESULTS

Twenty-two of 58 lesions (38%) caused ischemia. Compared with nonischemic lesions, ischemic lesions had smaller MLD (1.3 vs. 1.7 mm, p = 0.01), smaller MLA (2.5 vs. 3.8 mm(2), p = 0.01), and greater %APV (48.9% vs. 39.3%, p < 0.0001). Area under the receiver operating characteristic curve was highest for %APV (0.85) compared with diameter stenosis (0.68), area stenosis (0.66), MLD (0.75), or MLA (0.78). Addition of %APV to other measures showed significant reclassification over diameter stenosis (NRI 0.77, p < 0.001), area stenosis (NRI 0.63, p = 0.002), MLD (NRI 0.62, p = 0.001), and MLA (NRI 0.43, p = 0.01).

CONCLUSIONS

Compared with diameter stenosis, area stenosis, MLD, and MLA, %APV by coronary CTA improves identification, discrimination, and reclassification of ischemic lesions of intermediate stenosis severity.

Inducible myocardial ischemia and outcomes in patients with coronary artery disease and left ventricular dysfunction

OBJECTIVES

The study objectives were to test the hypotheses that ischemia during stress testing has prognostic value and identifies those patients with coronary artery disease (CAD) with left ventricular (LV) dysfunction who derive the greatest benefit from coronary artery bypass grafting (CABG) compared with medical therapy.

BACKGROUND

The clinical significance of stress-induced ischemia in patients with CAD and moderately to severely reduced LV ejection fraction (EF) is largely unknown.

METHODS

The STICH (Surgical Treatment for IsChemic Heart Failure) trial randomized patients with CAD and EF ≤35% to CABG or medical therapy. In the current study, we assessed the outcomes of those STICH patients who underwent a radionuclide (RN) stress test or a dobutamine stress echocardiogram (DSE). A test was considered positive for ischemia by RN testing if the summed difference score (difference in tracer activity between stress and rest) was ≥4 or if ≥2 of 16 segments were ischemic during DSE. Clinical endpoints were assessed by intention to treat during a median follow-up of 56 months.

RESULTS

Of the 399 study patients (51 women, mean EF 26 ± 8%), 197 were randomized to CABG and 202 were randomized to medical therapy. Myocardial ischemia was induced during stress testing in 256 patients (64% of the study population). Patients with and without ischemia were similar in age, multivessel CAD, previous myocardial infarction, LV EF, LV volumes, and treatment allocation (all p = NS). There was no difference between patients with and without ischemia in all-cause mortality (hazard ratio: 1.08; 95% confidence interval: 0.77 to 1.50; p = 0.66), cardiovascular mortality, or all-cause mortality plus cardiovascular hospitalization. There was no interaction between ischemia and treatment for any clinical endpoint.

CONCLUSIONS

In CAD with severe LV dysfunction, inducible myocardial ischemia does not identify patients with worse prognosis or those with greater benefit from CABG over optimal medical therapy. (Comparison of Surgical and Medical Treatment for Congestive Heart Failure and Coronary Artery Disease [STICH]; NCT00023595).

Mortality risk as a function of the ratio of pulmonary trunk to ascending aorta diameter in patients with suspected coronary artery disease

Although an increased pulmonary trunk (PT) diameter to ascending aorta (AA) diameter ratio (PT/AA ratio) is associated with pulmonary hypertension, the prognostic utility of this metric remains unexamined. We investigated whether an increase in the PT/AA ratio, as measured using coronary computed tomographic angiography, is associated with the risk of all-cause death. We identified 1,326 consecutive patients (mean age 61 ± 13 years; 60% men) without known coronary artery disease who underwent coronary computed tomographic angiography. Patients with a history of congenital or valvular heart disease or aortic enlargement (≥4 cm) were excluded. The PT and AA diameters were measured at the PT bifurcation level. The patients were categorized by PT/AA deciles, with the ≥90th percentile (PT/AA ratio 0.9) considered elevated. All-cause death associated with a PT/AA ratio <0.9 versus ≥0.9 was evaluated using multivariate Cox proportional hazard models. During 2.9 ± 1.0 years of follow-up, 58 patients died. Patients with a PT/AA ratio ≥0.9 experienced 2.5-fold greater annualized mortality compared to those with <0.9 (3.1% vs 1.3%, p = 0.004). Adjusting for age, gender, heart rate, dyslipidemia, smoking, and coronary artery disease extent, the patients with a PT/AA ratio ≥0.9 experienced a greater mortality risk compared to patients with PT/AA ratio <0.9 (hazard ratio 3.2, 95% confidence interval 1.6 to 6.6, p = 0.001). In the 1,059 patients with left ventricular ejection fraction measurements, a lower left ventricular ejection fraction was observed in the PT/AA ratio ≥0.9 group (p <0.05). In conclusion, incrementally and independent of the traditional coronary artery disease risk factors, an elevated PT/AA ratio was associated with increased mortality risk in patients without known coronary artery disease undergoing coronary computed tomographic angiography.

Initial multicentre experience of high-speed myocardial perfusion imaging: comparison between high-speed and conventional single-photon emission computed tomography with angiographic validation

PURPOSE

High-speed (HS) single-photon emission computed tomography (SPECT) with a recently developed solid-state camera shows comparable myocardial perfusion abnormalities to those seen in conventional SPECT. We aimed to compare HS and conventional SPECT images from multiple centres with coronary angiographic findings.

METHODS

The study included 50 patients who had sequential conventional SPECT and HS SPECT myocardial perfusion studies and coronary angiography within 3 months. Stress and rest perfusion images were visually analysed and scored semiquantitatively using a 17-segment model by two experienced blinded readers. Global and coronary territorial summed stress scores (SSS) and summed rest scores (SRS) were calculated. Global SSS ≥3 or coronary territorial SSS ≥2 was considered abnormal. In addition the total perfusion deficit (TPD) was automatically derived. TPD >5% and coronary territorial TPD ≥3% were defined as abnormal. Coronary angiograms were analysed for site and severity of coronary stenosis; ≥50% was considered significant.

RESULTS

Of the 50 patients, 13 (26%) had no stenosis, 22 (44%) had single-vessel disease, 6 (12%) had double-vessel disease and 9 (18%) had triple-vessel disease. There was a good linear correlation between the visual global SSS and SRS (Spearman's ρ 0.897 and 0.866, respectively; p < 0.001). In relation to coronary angiography, the sensitivities, specificities and accuracies of HS SPECT and conventional SPECT by visual assessment were 92% (35/38), 83% (10/12) and 90% (45/50) vs. 84% (32/38), 50% (6/12) and 76% (38/50), respectively (p < 0.001). The sensitivities, specificities and accuracies of HS SPECT and conventional SPECT in relation to automated TPD assessment were 89% (31/35), 57% (8/14) and 80% (39/49) vs. 86% (31/36), 77% (10/13) and 84% (41/49), respectively.

CONCLUSION

HS SPECT allows fast acquisition of myocardial perfusion images that correlate well with angiographic findings with overall accuracy by visual assessment better than conventional SPECT. Further assessment in a larger patient population may be needed to confirm this observation.

Impact of family history of coronary artery disease in young individuals (from the CONFIRM registry)

Although family history (FH) of coronary artery disease (CAD) is considered a risk factor for future cardiovascular events, the prevalence, extent, severity, and prognosis of young patients with FH of CAD have been inadequately studied. From 27,125 consecutive patients who underwent coronary computed tomographic angiography, 6,308 young patients (men aged <55 years and women aged <65 years) without known CAD were identified. Obstructive CAD was defined as >50% stenosis in a coronary artery >2 mm diameter. Risk-adjusted logistic regression, Kaplan-Meier, and Cox proportional-hazards models were used to compare patients with and without FH of CAD. Compared with subjects without FH of CAD, those with FH of CAD (FH+) had higher prevalences of any CAD (40% vs 30%, p <0.001) and obstructive CAD (11% vs 7%, p <0.001), with multivariate odds of FH+ increasing the likelihood of obstructive CAD by 71% (p <0.001). After a mean follow-up period of 2 ± 1 years (42 myocardial infarctions and 39 all-cause deaths), FH+ patients experienced higher annual rates of myocardial infarction (0.5% vs 0.2%, log-rank p = 0.001), with a positive FH the strongest predictor of myocardial infarction (hazard ratio 2.6, 95% confidence interval 1.4 to 4.8, p = 0.002). In conclusion, young FH+ patients have higher presence, extent, and severity of CAD, which are associated with increased risk for myocardial infarction. Compared with other clinical CAD risk factors, positive FH in young patients is the strongest clinical predictor of future unheralded myocardial infarction.

Prognostic utility of coronary computed tomographic angiography

Coronary computed tomographic angiography (CCTA) employing CT scanners of 64-detector rows or greater represents a noninvasive method that enables accurate detection and exclusion of anatomically obstructive coronary artery disease (CAD), providing excellent diagnostic information when compared to invasive angiography. There are numerous potential advantages of CCTA beyond simply luminal stenosis assessment including quantification of atherosclerotic plaque volume as well as assessment of plaque composition, extent, location and distribution. In recent years, an array of studies has evaluated the prognostic utility of CCTA findings of CAD for the prediction of major adverse cardiac events, all-cause death and plaque instability. This prognostic information enhances risk stratification and, if properly acted upon, may improve medical therapy and/or behavioral changes that may enhance event-free survival. The goal of the present article is to summarize the current status of the prognostic utility of CCTA findings of CAD.

Mortality rates in smokers and nonsmokers in the presence or absence of coronary artery calcification

OBJECTIVES

The aim of this study was to further explore the interplay between smoking status, coronary artery calcium (CAC), and all-cause mortality.

BACKGROUND

Prior studies have not directly compared the relative prognostic impact of CAC in smokers versus nonsmokers. In particular, although a calcium score of zero (CAC = 0) is a known favorable prognostic marker, whether smokers with CAC = 0 have as good a prognosis as nonsmokers with CAC = 0 is unknown. Given that computed tomography (CT) screening for lung cancer appears effective in smokers, the relative prognostic implications of visualizing any CAC versus no CAC on such screening also deserve study.

METHODS

Our study cohort consisted of 44,042 asymptomatic individuals referred for noncontrast cardiac CT (age 54 ± 11 years, 54% men). Subjects were followed for a mean of 5.6 years. The primary endpoint was all-cause mortality.

RESULTS

Approximately 14% (n = 6,020) of subjects were active smokers at enrollment. There were 901 deaths (2.05%) overall, with increased mortality in smokers versus nonsmokers (4.3% vs. 1.7%, p < 0.0001). Smoking remained a risk factor for mortality across increasing strata of CAC scores (1 to 100, 101 to 400, and >400). At each stratum of elevated CAC score, mortality in smokers was consistently higher than mortality in nonsmokers from the CAC stratum above. In multivariable analysis within these strata, we found mortality hazard ratios of 3.8 (95% confidence interval [CI]: 2.8 to 5.2), 3.5 (95% CI: 2.6 to 4.9), and 2.7 (95% CI: 2.1 to 3.5), respectively, in smokers compared with nonsmokers. However, among the 19,898 individuals with CAC = 0, the mortality hazard ratio for smokers without CAC was 3.6 (95% CI: 2.3 to 5.7), compared with nonsmokers without CAC.

CONCLUSIONS

Smoking is a risk factor for death across the entire spectrum of subclinical coronary atherosclerosis. Smokers with any CAC had significantly higher mortality than smokers without CAC, a finding with implications for smokers undergoing lung cancer CT-based screening. However, the absence of CAC might not be as useful a "negative risk factor" in active smokers, because this group has mortality rates similar to nonsmokers with mild-to-moderate atherosclerosis.

Relationship of epicardial fat volume to coronary plaque, severe coronary stenosis, and high-risk coronary plaque features assessed by coronary CT angiography

BACKGROUND

Associations of epicardial fat volume (EFV) measured on noncontrast cardiac CT (NCT) include coronary plaque, myocardial ischemia, and adverse cardiac events.

OBJECTIVES

This study aimed to define the relationship of EFV to coronary plaque type, severe coronary stenosis, and the presence of high-risk plaque features (HRPFs).

METHODS

We retrospectively evaluated 402 consecutive patients, with no prior history of coronary artery disease, who underwent same day NCT and coronary CT angiography (CTA). EFV was measured on NCT with the use of validated, semiautomated software. The coronary arteries were evaluated for coronary plaque type (calcified [CP], noncalcified [NCP], or partially calcified [PCP]) and coronary stenosis severity ≥70% with the use of coronary CTA. For patients with NCP and PCP, 2 high-risk plaque features were evaluated: low-attenuation plaque and positive remodeling.

RESULTS

There were 402 patients with a median age of 66 years (range, 23-92 years) of whom 226 (56%) were men. The EFV was greater in patients with CP (112 ± 55 cm(3) vs 89 ± 39 cm(3)), PCP (110 ± 57 cm(3) vs 98 ± 45 cm(3)), and NCP (115 ± 44 cm(3) vs EFV 100 ± 52 cm(3)). In the 192 patients with PCP or NCP, on multivariable analysis, after adjusting for conventional cardiovascular risk factors, EFV was an independent predictor of ≥70% coronary artery stenosis (odds ratio [OR], 3.0; 95% CI, 1.3-6.6; P = 0.008), any high-risk plaque features (OR, 1.7; 95% CI, 0.9-3.4; P = 0.04), and low attention plaque (OR, 2.4; 95% CI, 1.1-5.1; P = 0.02) but not of positive remodeling.

CONCLUSIONS

EFV is greater in patients with CP, PCP, and NCP. In patients with NCP and PCP, EFV is significantly associated with severe coronary stenosis, high-risk plaque features, and low attenuation plaque.

Relationship of low- and high-density lipoproteins to coronary artery plaque composition by CT angiography

BACKGROUND

The association between lipoprotein levels and coronary plaque composition is not well understood.

OBJECTIVE

The aim of this prospective international multicenter study of statin-naive individuals was to evaluate the association of low-density lipoprotein (LDL), high-density lipoprotein (HDL), and total cholesterol (TC) to coronary plaque composition by coronary computed tomographic angiography (CTA).

METHODS

We studied 4575 individuals without known coronary artery disease not taking statin medications who underwent coronary CTA. Comparisons were made between those with high versus low LDL, HDL, TC, and non-HDL. We assessed the relationship of lipoproteins and plaques of specific composition (noncalcified [NCP], partially calcified [PCP], or calcified [CP] plaque).

RESULTS

Mean age was 57 ± 11 years (55% men). In univariable analyses, high LDL, low HDL, high TC, and high non-HDL were each associated with increased prevalence of NCPs, PCPs, and CPs (P < 0.05 for all). In multivariable analyses, high non-HDL was associated with the presence of NCP (odds ratio, 1.47; 95% CI, 1.22-1.78: P < 0.001). In the further subanalysis, a weak relationship between the highest group of non HDL (≥190 mg/dL) and the presence of CP was also noted (odds ratio, 1.33; 95% CI, 1.01-1.76; P = 0.04). Further, high non-HDL was associated with increasing numbers of segments with NCP (β coefficient, 0.043; 95% CI, 0.021-0.065; P < 0.001) but not segments with PCP or CP.

CONCLUSION

NCP presence and extent are associated with high non-HDL. These results suggest a relationship between lipid profile and plaque composition.

Multisoftware reproducibility study of stress and rest myocardial blood flow assessed with 3D dynamic PET/CT and a 1-tissue-compartment model of 82Rb kinetics

Routine quantification of myocardial blood flow (MBF) requires robust and reproducible processing of dynamic image series. The goal of this study was to evaluate the reproducibility of 3 highly automated software programs commonly used for absolute MBF and flow reserve (stress/rest MBF) assessment with (82)Rb PET imaging.

METHODS

Dynamic rest and stress (82)Rb PET scans were selected in 30 sequential patient studies performed at 3 separate institutions using 3 different 3-dimensional PET/CT scanners. All 90 scans were processed with 3 different MBF quantification programs, using the same 1-tissue-compartment model. Global (left ventricle) and regional (left anterior descending, left circumflex, and right coronary arteries) MBF and flow reserve were compared among programs using correlation and Bland-Altman analyses.

RESULTS

All scans were processed successfully by the 3 programs, with minimal operator interactions. Global and regional correlations of MBF and flow reserve all had an R(2) of at least 0.92. There was no significant difference in flow values at rest (P = 0.68), stress (P = 0.14), or reserve (P = 0.35) among the 3 programs. Bland-Altman coefficients of reproducibility (1.96 × SD) averaged 0.26 for MBF and 0.29 for flow reserve differences among programs. Average pairwise differences were all less than 10%, indicating good reproducibility for MBF quantification. Global and regional SD from the line of perfect agreement averaged 0.15 and 0.17 mL/min/g, respectively, for MBF, compared with 0.22 and 0.26, respectively, for flow reserve.

CONCLUSION

The 1-tissue-compartment model of (82)Rb tracer kinetics is a reproducible method for quantification of MBF and flow reserve with 3-dimensional PET/CT imaging.

Usefulness of coronary computed tomography angiography to predict mortality and myocardial infarction among Caucasian, African and East Asian ethnicities (from the CONFIRM [Coronary CT Angiography Evaluation for Clinical Outcomes: An International Multicenter] Registry)

Studies examining coronary computed tomographic angiography (CCTA) have demonstrated increased mortality related to coronary artery disease (CAD) severity but are limited to relatively nondiverse ethnic populations. The aim of this study was to evaluate the prognostic significance of CAD on CCTA according to ethnicity for patients without previous CAD in a prospective international CCTA registry of 11 sites (7 countries) who underwent 64-slice CCTA from 2005 to 2010. CAD was defined as any coronary artery atherosclerosis and obstructive CAD as ≥50% stenosis. All-cause mortality and nonfatal myocardial infarction (MI) were assessed by ethnicity using Kaplan-Meier and Cox proportional hazards, controlling for baseline risk factors, medications, and revascularization. A total of 16,451 patients of mean age 58 years (55% men) were followed over a median of 2.0 years (interquartile range 1.4 to 3.2). Patients were 60.1% Caucasian, 34.4% East Asian, and 5.5% African. Death or MI occurred in 0.5% (38 of 7,109) among patients with no CAD, 1.6% (91 of 5,600) among those with nonobstructive CAD, and 3.8% (142 of 3,742) among those with ≥50% stenosis (p <0.001 among all groups). The annualized incidence of death or MI comparing obstructive to no obstructive CAD among Caucasians was 2.2% versus 0.7% (adjusted hazard ratio [aHR] 2.77, 95% confidence interval [CI] 1.73 to 4.43, p <0.001), among Africans 4.8% versus 1.1% (aHR 6.25, 95% CI 1.12 to 34.97, p = 0.037), and among East Asians 0.8% versus 0.1% (aHR 4.84, 95% CI 2.24 to 10.9, p <0.001). Compared to other ethnicities, East Asians had fewer than expected events (aHR 0.25, 95% CI 0.16 to 0.38, p <0.001). In conclusion, the presence and severity of CAD visualized by CCTA predict death or MI across 3 large ethnicities, whereas normal results on CCTA identify patients at very low risk.

Whole-heart coronary MRA with 100% respiratory gating efficiency: self-navigated three-dimensional retrospective image-based motion correction (TRIM)

PURPOSE

To develop a three-dimensional retrospective image-based motion correction technique for whole-heart coronary MRA with self-navigation that eliminates both the need to setup a diaphragm navigator and gate the acquisition.

METHODS

The proposed technique uses one-dimensional self-navigation to track the superior-inferior translation of the heart, with which the acquired three-dimensional radial k-space data is segmented into different respiratory bins. Respiratory motion is then estimated in image space using an affine transform model and subsequently this information is used to perform efficient motion correction in k-space. The performance of the proposed technique on healthy volunteers is compared with the conventional navigator gating approach as well as data binning using diaphragm navigator.

RESULTS

The proposed method is able to reduce the imaging time to 7.1±0.5 min from 13.9±2.6 min with conventional navigator gating. The scan setup time is reduced as well due to the elimination of the navigator. The proposed method yields excellent image quality comparable with either conventional navigator gating or the navigator binning approach.

CONCLUSION

We have developed a new respiratory motion correction technique for coronary MRA that enables 1 mm(3) isotropic resolution and whole-heart coverage with 7 min of scan time. Further tests on patient population are needed to determine its clinical usage.

Myocardial perfusion imaging with PET

PET-myocardial perfusion imaging (MPI) allows accurate measurement of myocardial perfusion, absolute myocardial blood flow and function at stress and rest in a single study session performed in approximately 30 min. Various PET tracers are available for MPI, and rubidium-82 or nitrogen-13-ammonia is most commonly used. In addition, a new fluorine-18-based PET-MPI tracer is currently being evaluated. Relative quantification of PET perfusion images shows very high diagnostic accuracy for detection of obstructive coronary artery disease. Dynamic myocardial blood flow analysis has demonstrated additional prognostic value beyond relative perfusion imaging. Patient radiation dose can be reduced and image quality can be improved with latest advances in PET/CT equipment. Simultaneous assessment of both anatomy and perfusion by hybrid PET/CT can result in improved diagnostic accuracy. Compared with SPECT-MPI, PET-MPI provides higher diagnostic accuracy, using lower radiation doses during a shorter examination time period for the detection of coronary artery disease.

Myocardial perfusion imaging with a solid-state camera: simulation of a very low dose imaging protocol

High-sensitivity dedicated cardiac camera systems provide an opportunity to lower the injected doses for SPECT myocardial perfusion imaging (MPI), but the exact limits for lowering doses have not been determined. List-mode data acquisition allows for reconstruction of various fractions of acquired counts, enabling a simulation of gradually lower administered dose. We aimed to determine the feasibility of very low dose MPI by exploring the minimal count level in the myocardium required for accurate MPI.

METHODS

Seventy-nine patients were studied (mean body mass index, 30.0 ± 6.6; range, 20.2-54.0 kg/m(2)) who underwent 1-d standard-dose (99m)Tc-sestamibi exercise or adenosine rest-stress MPI for clinical indications using a cadmium-zinc-telluride dedicated cardiac camera. The imaging time was 14 min, with averaged 803 ± 200 MBq (21.7 ± 5.4 mCi) of (99m)Tc injected at stress. To simulate clinical scans with a lower dose at that imaging time we reframed the list-mode raw data. Accordingly, 6 stress-equivalent datasets were reconstructed containing various count fractions of the original scan. Automated quantitative perfusion and gated SPECT software was used to quantify total perfusion deficit (TPD) and ejection fraction for all 553 datasets (7 × 79). The minimal acceptable left ventricular region counts were determined on the basis of a previous report with repeatability of same-day, same-injection Anger camera studies. Pearson correlation coefficients and the SD of differences in TPD for all scans were calculated.

RESULTS

The correlations of quantitative perfusion and function analysis were excellent for both global and regional analysis between original scans and all simulated low-count scans (all r ≥ 0.95, P < 0.0001). The minimal acceptable counts were determined to be 1.0 million for the left ventricular region. At this count level, the SD of differences was 1.7% for TPD and 4.2% for ejection fraction. This count level would correspond to a 92.5-MBq (2.5-mCi) injected dose for the 14-min acquisition or 125.8-MBq (3.4-mCi) injected dose for the 10-min acquisition.

CONCLUSION

1.0 million counts appear to be sufficient to produce myocardial images that agree well with 8.0-million-count images on quantitative perfusion and function parameters. With a dedicated cardiac camera, these images can be obtained over 10 min with an effective radiation dose of less than 1 mSv without significant sacrifice of accuracy.

Prognostic value of stress myocardial perfusion positron emission tomography: results from a multicenter observational registry

OBJECTIVES

The primary objective of this multicenter registry was to study the prognostic value of positron emission tomography (PET) myocardial perfusion imaging (MPI) and the improved classification of risk in a large cohort of patients with suspected or known coronary artery disease (CAD).

BACKGROUND

Limited prognostic data are available for MPI with PET.

METHODS

A total of 7,061 patients from 4 centers underwent a clinically indicated rest/stress rubidium-82 PET MPI, with a median follow-up of 2.2 years. The primary outcome of this study was cardiac death (n = 169), and the secondary outcome was all-cause death (n = 570). Net reclassification improvement (NRI) and integrated discrimination analyses were performed.

RESULTS

Risk-adjusted hazard of cardiac death increased with each 10% myocardium abnormal with mildly, moderately, or severely abnormal stress PET (hazard ratio [HR]: 2.3 [95% CI: 1.4 to 3.8; p = 0.001], HR: 4.2 [95% CI: 2.3 to 7.5; p < 0.001], and HR: 4.9 [95% CI: 2.5 to 9.6; p < 0.0001], respectively [normal MPI: referent]). Addition of percent myocardium ischemic and percent myocardium scarred to clinical information (age, female sex, body mass index, history of hypertension, diabetes, dyslipidemia, smoking, angina, beta-blocker use, prior revascularization, and resting heart rate) improved the model performance (C-statistic 0.805 [95% CI: 0.772 to 0.838] to 0.839 [95% CI: 0.809 to 0.869]) and risk reclassification for cardiac death (NRI 0.116 [95% CI: 0.021 to 0.210]), with smaller improvements in risk assessment for all-cause death.

CONCLUSIONS

In patients with known or suspected CAD, the extent and severity of ischemia and scar on PET MPI provided powerful and incremental risk estimates of cardiac death and all-cause death compared with traditional coronary risk factors.

Comparison of fully automated computer analysis and visual scoring for detection of coronary artery disease from myocardial perfusion SPECT in a large population

We compared the performance of fully automated quantification of attenuation-corrected (AC) and noncorrected (NC) myocardial perfusion SPECT (MPS) with the corresponding performance of experienced readers for detection of coronary artery disease (CAD).

METHODS

Rest-stress (99m)Tc-sestamibi MPS studies (n = 995; 650 consecutive cases with coronary angiography and 345 with likelihood of CAD < 5%) were obtained by MPS with AC. The total perfusion deficit (TPD) for AC and NC data was compared with the visual summed stress and rest scores of 2 experienced readers. Visual reads were performed in 4 consecutive steps with the following information progressively revealed: NC data, AC + NC data, computer results, and all clinical information.

RESULTS

The diagnostic accuracy of TPD for detection of CAD was similar to both readers (NC: 82% vs. 84%; AC: 86% vs. 85%-87%; P = not significant) with the exception of the second reader when clinical information was used (89%, P < 0.05). The receiver-operating-characteristic area under the curve (ROC AUC) for TPD was significantly better than visual reads for NC (0.91 vs. 0.87 and 0.89, P < 0.01) and AC (0.92 vs. 0.90, P < 0.01), and it was comparable to visual reads incorporating all clinical information. The per-vessel accuracy of TPD was superior to one reader for NC (81% vs. 77%, P < 0.05) and AC (83% vs. 78%, P < 0.05) and equivalent to the second reader (NC, 79%; and AC, 81%). The per-vessel ROC AUC for NC (0.83) and AC (0.84) for TPD was better than that for the first reader (0.78-0.80, P < 0.01) and comparable to that of the second reader (0.82-0.84, P = not significant) for all steps.

CONCLUSION

For detection of ≥70% stenoses based on angiographic criteria, a fully automated computer analysis of NC and AC MPS data is equivalent for per-patient and can be superior for per-vessel analysis, when compared with expert analysis.