Optimal medical therapy with or without percutaneous coronary intervention to reduce ischemic burden: results from the Clinical Outcomes Utilizing Revascularization and Aggressive Drug Evaluation (COURAGE) trial nuclear substudy

Eighth Annual Mario S. Verani, MD Memorial Lecture: Nuclear cardiology in the era of multimodality cardiac imaging: Can we survive?

Nuclear cardiology is the best noninvasive imaging method for measuring myocardial blood flow to diagnose coronary artery disease, assess the risk for adverse cardiac events, and identify long-term cardiac outcome. Our strengths include: reliance on physiology rather than anatomic definition; standardized and efficient techniques that can be performed in large hospitals and academic centers and in small hospitals and outpatient offices; a large body of evidence-based supporting clinical data; and profitability. We have defined training; committed to quality improvement through development of guidelines and appropriateness criteria; certified physicians and accredited laboratories; and implemented a strong payer advocacy program. Despite success, we find ourselves under attack for not being relevant within the new paradigm of atherosclerosis, being complacent, being used inappropriately, and exposing patients to radiation. We are facing cuts in reimbursement that will make it nearly impossible to provide services. By failing to develop new radiotracers and techniques, we find ourselves measuring only myocardial perfusion. Advances in echocardiography, cardiovascular magnetic resonance imaging, and computed tomography are providing alternative robust methods and redefining available options for noninvasive cardiovascular imaging. Given the attacks on nuclear cardiology and the existence of alternative methods, we have the option of becoming defensive and protective of our turf, or embracing the opportunity to build on our accomplishments and redefine the new practice of noninvasive cardiovascular imaging. It is in the best interest of nuclear cardiology and patients to pursue the latter course.

The present state of coronary computed tomography angiography a process in evolution

In the past 5 years since the introduction of 64-detector row cardiac computed tomography angiography (CCTA), there has been an exponential growth in the quantity of scientific evidence to support the feasibility of its use in the clinical evaluation of individuals with suspected coronary artery disease (CAD). Since then, there has been considerable debate as to where CCTA precisely fits in the algorithm of evaluation of individuals with suspected CAD. Proponents of CCTA contend that the quality and scope of the available evidence to date support the replacement of conventional methods of CAD evaluation by CCTA, whereas critics assert that clinical use of CCTA is not yet adequately proven and should be restricted, if used at all. Coincident with the scientific debate underlying the clinical utility of CCTA, there has developed a perception by many that the rate of growth in cardiac imaging is disproportionately high and unsustainable. In this respect, all noninvasive imaging modalities and, in particular, more newly introduced ones, have undergone a higher level of scrutiny for demonstration of clinical and economic effectiveness. We herein describe the latest available published evidence supporting the potential clinical and cost efficiency of CCTA, drawing attention not only to the significance but also the limitations of such studies. These points may trigger discussion as to what future studies will be both necessary and feasible for determining the exact role of CCTA in the workup of patients with suspected CAD.

Current concepts of integrated coronary physiology in the catheterization laboratory

Over the last 15 years, the use of invasive coronary physiology in the catheterization laboratory has demonstrated favorable outcomes for decision making in patients with intermediate single-vessel stenoses, complex bifurcation and ostial branch stenoses, multivessel coronary artery disease, and left main stenoses. A recent large multicenter study (FAME [FFR versus Angiography for Multivessel Evaluation]) found that a physiologically-guided approach was superior to the standard angiographically-guided approach for percutaneous revascularization in patients with multivessel coronary artery disease. This review addresses selected pertinent concepts and studies supporting the integration of coronary physiology in the catheterization laboratory for optimal patient outcomes.

Improved quantification and normal limits for myocardial perfusion stress-rest change

We aimed to improve the quantification of myocardial perfusion stress-rest changes in myocardial perfusion SPECT (MPS) studies for the optimal automatic detection of ischemia and coronary artery disease (CAD).

METHODS

Rest-stress (99m)Tc MPS studies (997 cases; 651 consecutive cases with correlating angiography and 346 cases with less than 5% likelihood (low likelihood [LLK]) of CAD) were analyzed. Normal limits for stress-rest changes were derived from additional LLK patients (40 women, 40 men). We computed the global stress-rest change (C-SR) by integrating direct stress-rest changes for each polar map pixel. Additionally, stress-rest change and total perfusion deficit (TPD) at stress were combined in 1 variable (C-TPD) for the optimal detection of CAD.

RESULTS

The area under the receiver-operating-characteristic curve (AUC) for C-SR (0.92) was larger than that for stress TPD-rest TPD (0.88) for the identification of stenosis of 70% or more (P < 0.0001). AUC (0.94) and sensitivity (90%) for C-TPD were higher than those for stress TPD (0.91 and 83%, respectively) (P < 0.0001), whereas specificity remained the same (81%).

CONCLUSION

C-SR and C-TPD provide higher diagnostic performance than difference between stress and rest TPD or stress hypoperfusion analysis.

Management of stable coronary artery disease

Results of two randomised controlled trials for the management of mild-to-moderate chronic stable coronary artery disease (Clinical Outcomes Utilizing Revascularization and Aggressive drug Evaluation [COURAGE] and Bypass Angioplasty Revascularization Investigation type-2 Diabetes [BARI-2D]) have stimulated a vigorous debate about whether an initial strategy of revascularisation or a conservative approach with drugs is most effective. The conclusions of these two trials were clear: for some patients randomly assigned after angiography to revascularisation or pharmacological therapy, rates of death and myocardial infarction did not differ between the two strategies. What remains unresolved is how to generalise these data to patients without angiography, the role of stress testing, and the preferred approach to patients with relevant ischaemia on stress testing. This Review draws attention to the controversial issues in both management approaches, analyses the strengths and limitations of recent trials, and proposes a treatment algorithm that is applicable to daily clinical practice. Findings suggest that the severity of anginal symptoms and the extent of ischaemia in stress testing could help to identify patients who are at increased risk and who might benefit from an early invasive strategy. On the basis of the data and considerations presented, a strategy of initial optimum pharmacological therapy or direct invasive management can be tailored to an individual's circumstances and preferences.

Incremental value of adenosine-induced stress myocardial perfusion imaging with dual-source CT at cardiac CT angiography

PURPOSE

First, to assess the feasibility of a protocol involving stress-induced perfusion evaluated at computed tomography (CT) combined with cardiac CT angiography in a single examination and second, to assess the incremental value of perfusion imaging over cardiac CT angiography in a dual-source technique for the detection of obstructive coronary artery disease (CAD) in a high-risk population.

MATERIALS AND METHODS

Institutional review board approval and informed patient consent were obtained before patient enrollment in the study. The study was HIPAA compliant. Thirty-five patients at high risk for CAD were prospectively enrolled for evaluation of the feasibility of CT perfusion imaging. All patients underwent retrospectively electrocardiographically gated (helical) adenosine stress CT perfusion imaging followed by prospectively electrocardiographically gated (axial) rest myocardial CT perfusion imaging. Analysis was performed in three steps: (a)Coronary arterial stenoses were scored for severity and reader confidence at cardiac CT angiography, (b)myocardial perfusion defects were identified and scored for severity and reversibility at CT perfusion imaging, and (c)coronary stenosis severity was reclassified according to perfusion findings at combined cardiac CT angiography and CT perfusion imaging. The sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) of cardiac CT angiography before and after CT perfusion analysis were calculated.

RESULTS

With use of a reference standard of greater than 50% stenosis at invasive angiography, all parameters of diagnostic accuracy increased after CT perfusion analysis: Sensitivity increased from 83% to 91%; specificity, from 71% to 91%; PPV, from 66% to 86%; and NPV, from 87% to 93%. The area under the receiver operating characteristic curve increased significantly, from 0.77 to 0.90 (P < .005).

CONCLUSION

A combination protocol involving adenosine perfusion CT imaging and cardiac CT angiography in a dual-source technique is feasible, and CT perfusion adds incremental value to cardiac CT angiography in the detection of significant CAD.

The evolving roles of nuclear cardiology

The use of cardiac imaging modalities has grown steadily, and cardiac nuclear studies constitute a large part of this number. Nuclear Cardiology is often mistakenly considered a synonym of myocardial perfusion imaging (MPI), but has broader applications, including metabolic imaging, innervation imaging, among other technologies. MPI has been a powerful diagnostic and prognostic tool in the assessment of patients for known or suspected CAD for decades, and is now increasingly used for the evaluation of the anti-ischemic effects of various therapies, according to changes in left ventricular perfusion defect size defined by sequential MPI. Neuronal dysfunction identified with iodine-123-metaiodobenzylguanidine may give information on prognosis in different disease conditions, such as after myocardial infarction, in diabetes and dilated cardiomyopathy. Molecular imaging may identify the predominant cellular population in the atherosclerotic plaque and help predict the likelihood of clinical events. Therefore, although its usefulness is well established, Nuclear Cardiology remains a moving science, whose roles keep in pace with evolving clinical needs and expectations.

Chronic coronary artery disease: diagnosis and management

Coronary artery disease (CAD) is the single most common cause of death in the developed world, responsible for about 1 in every 5 deaths. The morbidity, mortality, and socioeconomic importance of this disease make timely accurate diagnosis and cost-effective management of CAD of the utmost importance. This comprehensive review of the literature highlights key elements in the diagnosis, risk stratification, and management strategies of patients with chronic CAD. Relevant articles were identified by searching the PubMed database for the following terms: chronic coronary artery disease or stable angina. Novel imaging modalities, pharmacological treatment, and invasive (percutaneous and surgical) interventions have revolutionized the current treatment of patients with chronic CAD. Medical treatment remains the cornerstone of management, but revascularization continues to play an important role. In the current economic climate and with health care reform very much on the horizon, the issue of appropriate use of revascularization is important, and the indications for revascularization, in addition to the relative benefits and risks of a percutaneous vs a surgical approach, are discussed.

[Management of ischemic heart disease in the elderly]

Clinical features of ischemic heart disease in the elderly are different from those in non-elderly patients. The prevalence of female patients, hypertension and co-morbidity was higher in the elderly than in non-elderly patients. Atypical clinical presentation should be taken into consideration, particularly in patients with acute coronary syndrome, because early initiation of coronary reperfusion therapy reduces mortality significantly in elderly patients. In chronic stable angina, risk stratification of patients using stress myocardial perfusion imaging plays an important clinical role. The management of coronary risk factors to prevent cardiovascular events is of utmost importance in the elderly since the mortality of acute myocardial infarction is very high. Among classical risk factors, beneficial effects of the management of blood pressure on hypertensive and/or diabetic patients are enormous. Recent development of percutaneous coronary intervention facilitated coronary revascularization to reduce ischemic burden even in patients aged 80 years or older due to the low invasiveness of the procedure. However, cardiac surgery is still regarded as the first option for the elderly ith associated aortic stenosis, diffuse 3-vessel coronary artery disease, or distal left main trunk disease.

Does myocardial perfusion scintigraphy predict improvement in symptoms and exercise capacity following successful elective percutaneous coronary intervention?

BACKGROUND

Elective percutaneous coronary intervention (PCI) without inducible ischaemia may not be beneficial. We investigated the prevalence of inducible hypoperfusion using myocardial perfusion scintigraphy (MPS) in patients undergoing PCI, and its ability to predict functional outcome.

METHODS AND RESULTS

One hundred and twenty-three patients listed for elective PCI underwent MPS, using treadmill exercise where possible. Seventy-seven patients (63%) described chest pain in daily life. Seventy-four of 103 (72%) exercise ECG tests were positive. Ninety-one (74%) had inducible hypoperfusion on MPS (extensive in 25; 20%). Interventionalists were blinded to the scintigraphic results, and PCI was performed as planned. Six months later, Seattle Angina Questionnaire physical limitation score had improved from 66 to 76 (P < 0.0001), and peak treadmill workload from 7.2 +/- 2.3 to 9.0 +/- 2.7 METS (P < 0.0001). Sex, limiting chest pain on baseline exercise testing, and MPS summed difference score (SDS) were independent predictors of improvement. Patients with both limiting chest pain and SDS > or = 7 demonstrated an increase of 3.3 +/- 1.8 METS, compared with approximately 1.5 METS for other subgroups (P < 0.05).

CONCLUSIONS

Many patients undergoing elective PCI in a UK centre have little or no evidence of inducible hypoperfusion. The combination of limiting chest pain during exercise testing and significant inducible hypoperfusion on MPS predicts a large increase in exercise capacity after PCI.

Impact of an initial strategy of medical therapy without percutaneous coronary intervention in high-risk patients from the Clinical Outcomes Utilizing Revascularization and Aggressive DruG Evaluation (COURAGE) trial

We explored the safety and quality-of-life consequences of treating patients with stable coronary disease and high-risk features initially with optimal medical therapy (OMT) alone compared to OMT plus percutaneous coronary intervention. This was a post hoc analysis of Clinical Outcomes Utilizing Revascularization and Aggressive DruG Evaluation (COURAGE) trial patients. We defined high risk as the onset of Canadian Cardiovascular Society class III angina within 2 months or stabilized acute coronary syndrome within 2 weeks of enrollment. The primary end point was death or myocardial infarction after 4.6 years. Of the 2,287 patients enrolled in the COURAGE trial, 264 (12%) were high risk and had a relative risk of 1.56 for death or myocardial infarction (p = 0.0008) compared to those with non-high-risk features. A total of 35 primary events occurred in the OMT group and 32 in the percutaneous coronary intervention plus OMT group (hazard ratio 1.11, 95% confidence interval 0.69 to 1.79; p = 0.68). No significant difference was found in the prevalence of angina between the 2 groups at 1 year. During the first year of follow-up, 30% of the OMT patients crossed over to the revascularization group. In conclusion, an initial strategy of OMT alone for high-risk patients in the COURAGE trial did not result in increased death or myocardial infarction at 4.6 years or worse angina at 1 year, but it was associated with a high rate of crossover to revascularization.

Risk assessment and predictive value of coronary artery disease testing

This review highlights and compares risk assessment, predictive accuracy, and economic outcomes for 3 commonly applied cardiac imaging procedures: stress myocardial perfusion SPECT or PET and coronary CT angiography (CCTA). This review highlights an expansive evidence base for stress myocardial perfusion imaging and reveals a decided advantage for higher-risk patients, notably those who have established coronary artery disease (CAD). It is likely that the use of CCTA will continue to expand, particularly for patients with more atypical symptoms and patients with a lower likelihood of CAD. Despite a high level of evidence, comparative research is not available across modalities that could definitively drive utilization of cardiac imaging modalities.

Achieving an exercise workload of > or = 10 metabolic equivalents predicts a very low risk of inducible ischemia: does myocardial perfusion imaging have a role?

OBJECTIVES

We sought to identify prospectively the prevalence of significant ischemia (> or =10% of the left ventricle [LV]) on exercise single-photon emission computed tomography (SPECT) imaging relative to workload achieved in consecutive patients referred for myocardial perfusion imaging (MPI).

BACKGROUND

High exercise capacity is a strong predictor of a good prognosis, and the role of MPI in patients achieving high workloads is questionable.

METHODS

Prospective analysis was performed on 1,056 consecutive patients who underwent quantitative exercise gated (99m)Tc-SPECT MPI, of whom 974 attained > or =85% of their maximum age-predicted heart rate. These patients were further divided on the basis of attained exercise workload (<7, 7 to 9, or > or =10 metabolic equivalents [METs]) and were compared for exercise test and imaging outcomes, particularly the prevalence of > or =10% LV ischemia. Individuals reaching > or =10 METs but <85% maximum age-predicted heart rate were also assessed.

RESULTS

Of these 974 subjects, 473 (48.6%) achieved > or =10 METs. This subgroup had a very low prevalence of significant ischemia (2 of 473, 0.4%). Those attaining <7 METs had an 18-fold higher prevalence (7.1%, p < 0.001). Of the 430 patients reaching > or =10 METs without exercise ST-segment depression, none had > or =10% LV ischemia. In contrast, the prevalence of > or =10% LV ischemia was highest in the patients achieving <10 METs with ST-segment depression (14 of 70, 19.4%).

CONCLUSIONS

In this referral cohort of patients with an intermediate-to-high clinical risk of coronary artery disease, achieving > or =10 METs with no ischemic ST-segment depression was associated with a 0% prevalence of significant ischemia. Elimination of MPI in such patients, who represented 31% (430 of 1,396) of all patients undergoing exercise SPECT in this laboratory, could provide substantial cost-savings.

Review article: Coronary artery stenoses: detection and revascularization in renal disease

Cardiovascular events are markedly elevated in those with all degrees of renal impairment compared to the general population. There are well established guidelines in the general population for the management of coronary artery disease, however, similar guidelines have not been established in the renal population. This review examines the current published work on the detection of coronary artery stenoses in addition to summarizing the outcomes of revascularization in patients with kidney disease. Testing for coronary artery disease in the renal population most commonly occurs in dialysis patients as part of their assessment for renal transplantation. While a positive myocardial stress test for the detection of significant coronary artery stenoses is associated with an increased risk of cardiac events, there is no clear information currently showing that cardiovascular testing itself reduces the rate of adverse cardiac events after transplantation. Revascularization of coronary artery stenoses is associated with higher morbidity and mortality in all groups with kidney disease than in the general population, with the exception of renal transplant recipients where the mortality is likely to be similar to that of the general population. There appears to be a benefit in coronary artery bypass surgery compared to percutaneous intervention in those on dialysis and after renal transplant. Currently, there is little data to support coronary artery intervention prior to transplantation in those with asymptomatic coronary artery disease.

Coronary CT angiography and myocardial perfusion imaging to detect flow-limiting stenoses: a potential gatekeeper for coronary revascularization?

AIMS

To evaluate the diagnostic accuracy of a combined non-invasive assessment of coronary artery disease with coronary CT angiography (CTA) and myocardial perfusion imaging (MPI) for the detection of flow-limiting coronary stenoses and its potential as a gatekeeper for invasive examination and treatment.

METHODS AND RESULTS

In 78 patients (mean age 65 +/- 9 years) referred for coronary angiography (CA), additional CTA and MPI (using single-photon emission-computed tomography) were performed and the findings not communicated. Detection of flow-limiting stenoses (justifying revascularization) by the combination of CTA and MPI (CTA/MPI) was compared with the combination of quantitative coronary angiography (QCA) plus MPI (QCA/MPI), which served as standard of reference. The findings of both combinations were related to the treatment strategy (revascularization vs. medical treatment) chosen in the catheterization laboratory based on the CA findings. Sensitivity, specificity, positive and negative predictive value, and accuracy of CTA/MPI for the detection of flow-limiting coronary stenoses were 100% each. More than half of revascularization procedures (21/40, 53%) was performed in patients without flow-limiting stenoses and 76% (47/62) of revascularized vessels were not associated with ischaemia on MPI.

CONCLUSION

The combined non-invasive approach CTA/MPI has an excellent accuracy to detect flow-limiting coronary stenoses compared with QCA/MPI and its use as a gatekeeper appears to make a substantial part of revascularization procedures redundant.