Cardiovascular Imaging Research at the Crossroads

Patterns of stress testing and diagnostic catheterization after coronary stenting in 250 350 medicare beneficiaries

BACKGROUND

Patterns of noninvasive stress test (ST) and invasive coronary angiography (CA) utilization after percutaneous coronary intervention (PCI) are not well described in older populations.

METHODS AND RESULTS

We linked National Cardiovascular Data Registry CathPCI Registry data with longitudinal Medicare claims data for 250 350 patients undergoing PCI from 2005 to 2007 and described subsequent testing and outcomes. Between 60 days post-PCI and end of follow-up (median 24 months), 49% (n=122 894) received ST first, 10% (n=25 512) underwent invasive CA first, and 41% (n=101 944) had no testing. Several clinical risk factors at time of index PCI were associated with decreased likelihood of downstream testing (ST or CA, P<0.05 for all), including older age (hazard ratio [HR] 0.784 per 10-year increase), male sex (HR 0.946), heart failure (HR 0.925), diabetes mellitus (HR 0.954), smoking (HR 0.804), and renal failure (HR 0.880). Fifteen percent of patients with ST first proceeded to subsequent CA within 90 days of testing (n=18 472/122 894) [corrected]; of these, 48% (n=8831) underwent revascularization within 90 days, compared with 53% (n=13 316) of CA first patients (P<0.0001).

CONCLUSIONS

In this descriptive analysis, ST and invasive CA were common in older patients after PCI. Paradoxically, patients with higher risk features at baseline were less likely to undergo post-PCI testing. The revascularization yield was low on patients referred for ST after PCI, with only 7% [corrected] undergoing revascularization within 90 days.

Coronary CT angiography after stress testing: an efficient use of resources? Implications of the Advanced Cardiovascular Imaging Consortium (ACIC) results

Coronary CT angiography (CCTA) has matured to be a fast noninvasive imaging test in the evaluation of coronary artery disease (CAD). It has demonstrated excellent accuracy for defining the presence and the severity of luminal coronary artery stenoses and is probably the best noninvasive test to reliably exclude atherosclerotic coronary disease. Furthermore, accumulating CCTA data indicate that it can identify individuals at risk for all-cause mortality. It is also well known that despite the wealth of data regarding diagnostic and prognostic values of stress testing in CAD, up to 10% of stress imaging studies are considered inconclusive, leading to subsequent invasive coronary angiography for definitive diagnosis often with negative results. Moreover, recent data indicate that up to 30 % of patients undergoing angiography have no significant CAD despite a majority of them having had a prior stress test. Whether CCTA can serve as a cost-effective methodology to invasive angiography has been a source of active research. In this context, we will discuss the implications of the recently published data from the Advanced Cardiovascular Imaging Consortium registry looking at the use of CCTA after stress testing in Michigan.

Single-centre survey of the application of cardiovascular magnetic resonance in clinical routine

AIMS

Awareness of cardiovascular magnetic resonance (CMR) is growing due to increasing evidence for providing relevant functional and morphologic information. This single-centre survey aimed at providing descriptive data about the clinical application and potential impact of CMR.

METHODS AND RESULTS

All 2598 clinically indicated CMR exams were prospectively registered during 1 year in one single centre. Detailed data of the individual patient and procedural information of each exam were collected. In a simulation of CMR-based clinical decision-making in a subgroup of 250 cases, the influence of CMR on further diagnostic testing and answering the clinical question was estimated. Inflammatory (31%) and coronary (28%) heart disease were the most frequent indications. The exams were fast (98% < 60 min), robust (0.4% non-diagnostic image quality), and mostly used contrast media (76%). Anxiolytic sedation was required to overcome claustrophobia in 3.8%. Two per cent of all exams were terminated prematurely. No severe adverse events occurred. All moderate adverse events (0.5%) were associated with stress medication (1.7% of all stress tests) or contrast media (0.15% of all contrast enhanced studies). In the simulation, CMR influenced the individual selection of diagnostic testing and provided valuable information to establish or exclude a diagnosis.

CONCLUSION

This single-centre experience demonstrated a versatile application of CMR at reasonable time expense, safety, and robustness. The simulation of CMR-based decision-making indicated that CMR may influence patient management.

Rationale, design, and goals of the Advanced Cardiovascular Imaging Consortium (ACIC): A Blue Cross Blue Shield of Michigan collaborative quality improvement project

BACKGROUND

Coronary computed tomography angiography (CCTA) is an emerging noninvasive anatomical method for evaluation of patients with suspected coronary artery disease (CAD). Multicenter clinical registries are key to efforts to establish the role of CCTA in CAD diagnosis and management. The Advanced Cardiovascular Imaging Consortium (ACIC) is a statewide, multicenter collaborative quality initiative with the intent to establish quality and appropriate use of CCTA in Michigan.

METHODS

The ACIC is sponsored by the Blue Cross Blue Shield of Michigan/Blue Care Network, and its 47 sites include imaging centers that offer CCTA and meet established structure and process standards for participation. Patients enrolled include those with suspected ischemia with or without known CAD, and individuals across the entire spectrum of CAD risk. Patient demographics, history, CCTA scan-related data and findings, and 90-day follow-up data are entered prospectively into a centralized database with strict validation tools and processes. Collaborative quality initiatives include radiation dose reduction and appropriate CCTA use by education and feedback to participating sites and referring physicians.

CONCLUSIONS

Across a wide range of institutions, the ACIC permits evaluation of "real-world" utilization and effectiveness of CCTA and examines an alternative, nontraditional approach to utilization management wherein physicians and payers collaborate to address the growing problem of cardiac imaging overutilization.

Nomograms for estimating coronary artery disease prognosis with gated stress myocardial perfusion SPECT

BACKGROUND

Nomograms can be useful tools for estimating coronary artery disease (CAD) risk. We sought to devise risk-based nomograms for stress myocardial perfusion SPECT to include measures of % ischemic myocardium and left ventricular function.

METHODS

A total of 4,575 patients were consecutively and prospectively enrolled in the Myoview Prognosis Registry. Multivariable Cox proportional hazards model were employed to estimate CAD death or MI. Nomograms were devised from the results of the Cox models.

RESULTS

CAD death or MI rates worsened in a gradient manner by the % ischemic myocardium. Higher risk patients were those with a rest and/or post-stress LVEF ≤ 45%. A nomogram was developed to estimate 2-year CAD death or MI-free survival for exercising and pharmacologic stress patients by their post-stress LVEF and % ischemic myocardium MPS results. Patients undergoing pharmacologic stress with a rest and/or post-stress LVEF ≤ 45% with high risk ischemic findings had the lowest CAD death or MI event-free survival. For exercising patients with a preserved resting LVEF > 45%, 2-year CAD death or MI event-free survival ranged from 99.4% to 89% for 0% to ≥20% ischemic myocardium. Those at highest risk included patients undergoing pharmacologic stress with depressed LVEF. For pharmacologic stress patients with a resting LVEF ≤45%, 2-year CAD death or MI event-free survival ranged from 89% to 48% for 0% to ≥20% ischemic myocardium. For pharmacologic stress patients with a post-stress LVEF ≤ 45%, 2-year CAD death or MI event-free survival ranged from 88% to 46% for 0% to ≥20% ischemic myocardium. A validation cohort revealed moderate-strong correlation between observed and predicted survival (r = 0.71). Average discordance between observed and predicted survival was ≤2% but was greater for higher risk patients with lower predicted survival estimates.

CONCLUSIONS

Risk-based nomograms estimating important CAD outcomes may serve as a clinically useful tool to target therapeutic intervention for high risk patient subsets.

Nuclear medicine at a crossroads

The growth of molecular imaging heightens the promise of clinical nuclear medicine as a tool for individualization of patient care and for improvement of health-care outcomes. Together with greater use of integrated structure-function imaging, clinical nuclear medicine reaches beyond traditional specialty borders into diagnostic radiology and oncology. Yet, there are concerns about the future of nuclear medicine, including progressively declining reimbursement, the competitive advantages of diagnostic radiology, limited translation of research accomplishments to clinical diagnostic imaging and patient care, and an insufficient pool of incoming highly qualified nuclear medicine clinicians. Thus, nuclear medicine views itself as being at a critical crossroads. What will be important is for nuclear medicine to be positioned as the quintessential molecular imaging modality more centrally within medical imaging and for the integration of nuclear medicine with primary care specialties to be driven more by patient needs than by specialty needs. In this way, the full potential of nuclear medicine as an effective and efficient tool for improving patient outcomes can be realized.

Generating evidence for clinical benefit of PET/CT in diagnosing cancer patients

For diagnostic methods such as PET/CT, not only diagnostic accuracy but also clinical benefit must be demonstrated. However, there is a lack of consensus about how to approach this task. Here we consider 6 clinical scenarios to review some basic approaches to demonstrating the clinical benefit of PET/CT in cancer patients: replacement of an invasive procedure, improved accuracy of initial diagnosis, improved accuracy of staging for curative versus palliative treatment, improved accuracy of staging for radiation versus chemotherapy, response evaluation, and acceleration of clinical decisions. We also develop some guidelines for the evaluation of clinical benefit. First, it should be clarified whether there is a direct benefit of the use of PET/CT or an indirect benefit because of improved diagnostic accuracy. If there is an indirect benefit, then decision modeling should be used initially to assess the benefit expected from the use of PET/CT. Only if decision modeling does not allow definitive conclusions should randomized controlled trials be planned.

Comparative Effectiveness of Exercise Electrocardiography With or Without Myocardial Perfusion Single Photon Emission Computed Tomography in Women With Suspected Coronary Artery Disease

Background—

There is a paucity of randomized trials regarding diagnostic testing in women with suspected coronary artery disease (CAD). It remains unclear whether the addition of myocardial perfusion imaging (MPI) to the standard ECG exercise treadmill test (ETT) provides incremental information to improve clinical decision making in women with suspected CAD.

Methods and Results—

We randomized symptomatic women with suspected CAD, an interpretable ECG, and ≥5 metabolic equivalents on the Duke Activity Status Index to 1 of 2 diagnostic strategies: ETT or exercise MPI. The primary end point was 2-year incidence of major adverse cardiac events, defined as CAD death or hospitalization for an acute coronary syndrome or heart failure. A total of 824 women were randomized to ETT or exercise MPI. For women randomized to ETT, ECG results were normal in 64%, indeterminate in 16%, and abnormal in 20%. By comparison, the exercise MPI results were normal in 91%, mildly abnormal in 3%, and moderate to severely abnormal in 6%. At 2 years, there was no difference in major adverse cardiac events (98.0% for ETT and 97.7% for MPI; P =0.59). Compared with ETT, index testing costs were higher for exercise MPI ( P <0.001), whereas downstream procedural costs were slightly lower ( P =0.0008). Overall, the cumulative diagnostic cost savings was 48% for ETT compared with exercise MPI ( P <0.001).

Conclusions—

In low-risk, exercising women, a diagnostic strategy that uses ETT versus exercise MPI yields similar 2-year posttest outcomes while providing significant diagnostic cost savings. The ETT with selective follow-up testing should be considered as the initial diagnostic strategy in symptomatic women with suspected CAD.

Clinical Trial Registration—

http://www.clinicaltrials.gov . Unique identifier: NCT00282711.

Cardiac PET imaging for the detection and monitoring of coronary artery disease and microvascular health

Positron emission tomography (PET) myocardial perfusion imaging in concert with tracer-kinetic modeling affords the assessment of regional myocardial blood flow (MBF) of the left ventricle in absolute terms (milliliters per gram per minute). Assessment of MBF both at rest and during various forms of vasomotor stress provides insight into early and subclinical abnormalities in coronary arterial vascular function and/or structure, noninvasively. The noninvasive evaluation and quantification of MBF and myocardial flow reserve (MFR) extend the scope of conventional myocardial perfusion imaging from detection of end-stage, advanced, and flow-limiting, epicardial coronary artery disease (CAD) to early stages of atherosclerosis or microvascular dysfunction. Recent studies have shown that impaired hyperemic MBF or MFR with PET, with or without accompanying CAD, is predictive of increased relative risk of death or progression of heart failure. Quantitative approaches that measure MBF with PET identify multivessel CAD and offer the opportunity to monitor responses to lifestyle and/or risk factor modification and to therapeutic interventions. Whether improvement or normalization of hyperemic MBF and/or the MFR will translate to improvement in long-term cardiovascular outcome remains clinically untested. In the meantime, absolute measures of MBF with PET can be used as a surrogate marker for coronary vascular health, and to monitor therapeutic interventions. Although the assessment of myocardial perfusion with PET has become an indispensable tool in cardiac research, it remains underutilized in clinical practice. Individualized, image-guided cardiovascular therapy may likely change this paradigm in the near future.

Current challenges and future directions in cardiac imaging

Imaging is one of the most important accomplishments of medicine during the last 1000 years. The contribution of modern imaging to progress in the delivery of health care is unquestioned. However, we need to refine our use of imaging, limiting its use to those occasions when it can contribute directly or indirectly to improving and lengthening the lives of patients. Technology prowess in imaging alone is not sufficient to deliver value to individuals or to society. Continued investment in imaging technology requires critical appraisal of its use in clinical decision making and patient outcomes.

Temporal trends in compliance with appropriateness criteria for stress single-photon emission computed tomography sestamibi studies in an academic medical center

BACKGROUND

The purpose of this study was to apply published appropriateness criteria for single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) in a single academic medical center to determine if the percentage of inappropriate studies was changing over time. In a previous study, we applied the American College of Cardiology Foundation/American Society of Nuclear Cardiology (ASNC) appropriateness criteria for stress SPECT MPI and reported that 14% of stress SPECT studies were performed for inappropriate reasons.

METHODS

Using similar methodology, we retrospectively examined 284 patients who underwent stress SPECT MPI in October 2006 and compared the findings to the previous cohort of 284 patients who underwent stress SPECT MPI in May 2005.

RESULTS

The indications for testing in the 2 cohorts were very similar. The overall level of agreement in characterizing categories of appropriateness between 2 experienced cardiovascular nurse abstractors was good (kappa = 0.68), which represented an improvement from our previous study (kappa = 0.56). There was a significant change between May 2005 and October 2006 in the overall classification of categories for appropriateness (P = .024 by chi(2) statistic). There were modest, but insignificant, increases in the number of patients who were unclassified (15% in the current study vs 11% previously), appropriate (66% vs 64%), and uncertain (12% vs 11%). Only 7% of the studies in the current study were inappropriate, which represented a significant (P = .004) decrease from the 14% reported in the 2005 cohort.

CONCLUSIONS

In the absence of any specific intervention, there was a significant change in the overall classification of SPECT appropriateness in an academic medical center over 17 months. The only significant difference in individual categories was a decrease in inappropriate studies. Additional measurements over time will be required to determine if this trend is sustainable or generalizable.