Risk stratification in coronary artery disease: implications for stabilization and prevention

CRAX: A simple cardiovascular risk assessment tool to predict risk of acute myocardial infarction or death

BACKGROUND

Determining the risk of cardiovascular events is essential to optimize patient management.

METHODS AND RESULTS

5842 individuals underwent SPECT myocardial perfusion imaging (MPI) with 4.4 ± 1.2 years of follow-up. Models (the CRAX tool) were derived to predict the cumulative risk of death and acute myocardial infarction (AMI) at 1, 3, and 5 years using clinical and MPI variables. Predictors of AMI and death included age, number of hospitalizations in the 3 years preceding MPI, and left ventricular ejection fraction (LVEF). Additional predictors of death were the use of pharmacological stress, and global stress total perfusion deficit (sTPD), while transient ischemic dilation (TID), and ischemic total perfusion deficit (iTPD) change were predictive of AMI. CRAX predictions were significantly (P < .001) more accurate than clinical variables or MPI results alone, resulting in a significant net reclassification improvement (NRI, 7.5% for AMI, 14.5% death) compared to clinical variables alone. Accuracy for predicting major adverse cardiac events (MACE, comprising all-cause death, AMI, unstable angina, late revascularization) was comparable to that of AMI or death.

CONCLUSIONS

CRAX is a risk assessment tool that predicts the risk of AMI, death, or MACE, and improves prediction compared to clinical variables or MPI results alone.

The Current Status of SPECT or SPECT/CT in South Korea

The first step to nuclear medicine in Korea started with introduction of the gamma camera in 1969. Although planar images with the gamma camera give important functional information, they have the limitations that result from 2-dimensional images. Single-photon emission computed tomography (SPECT) due to its 3-dimensional image acquisition is superior to earlier planar gamma imaging in image resolution and diagnostic accuracy. As demand for a hybrid functional and anatomical imaging device has increased, integrated SPECT/CT systems have been used. In Korea, SPECT/CT was for the first time installed in 2003. SPECT/CT can eliminate many possible pitfalls on SPECT-alone images, making better attenuation correction and thereby improving image quality. Therefore, SPECT/CT is clinically preferred in many hospitals in various aspects. More recently, additional SPECT/CT images taken from the region with equivocal uptake on planar images have been helpful in making precise interpretation as part of their clinical workup in postoperative thyroid cancer patients. SPECT and SPECT/CT have various advantages, but its clinical application has gradually decreased in recent few years. While some researchers investigated the myocardial blood flow with cardiac PET using F-18 FDG or N-13 ammonia, myocardial perfusion SPECT is, at present, the radionuclide imaging study of choice for the risk stratification and guiding therapy in the coronary artery disease patients in Korea. New diagnostic radiopharmaceuticals for AD have received increasing attention; nevertheless, brain SPECT will remain the most reliable modality evaluating cerebral perfusion.

Prediction of cardiovascular events in pre-dialysis chronic kidney disease patients with normal SPECT myocardial perfusion imaging

PURPOSE

Patients with normal stress myocardial perfusion imaging (MPI) results generally have an excellent prognosis with <1% cardiovascular events/year. Chronic kidney disease (CKD) is an established risk factor for cardiovascular events. However, the estimated glomerular filtration rate (eGFR) varies considerably among patients with CKD. We evaluated the prognostic value of eGFR for patients with CKD who did not undergo hemodialysis and had no evidence of coronary artery disease (CAD).

METHODS AND SUBJECTS

Patients with CKD (n=108; 58 males; mean age: 74 years) with no CAD [no previous CAD and normal stress MPI results; summed stress score (SSS) <4] and with no history of hemodialysis were followed-up (mean duration: 24 months). CKD was defined by eGFR of <60 ml/min/1.73 m(2) and/or persistent proteinuria. Cardiovascular events included cardiac death, non-fatal myocardial infarction, and unstable angina.

RESULTS

Cardiovascular events were observed in 8 patients with CKD (7%). The following were determined as significant predictors of these events: age (hazard ratio=1.14; p=0.019), hemoglobin levels (hazard ratio=0.69; p=0.021), eGFR (hazard ratio=0.94; p=0.008), SSS (hazard ratio=2.31; p=0.012), and summed difference score (hazard ratio=2.33; p=0.014).

CONCLUSIONS

Patients with CKD and with no previous CAD and normal stress MPI results (SSS<4) may not exhibit an excellent cardiovascular prognosis. Further, a lower eGFR and stress MPI results may be the predictors of cardiovascular events. Thus, patients with a lower eGFR and/or normal stress MPI results (SSS<4) may require continuous follow-up.

The predictive value of chronic kidney disease for assessing cardiovascular events under consideration of pretest probability for coronary artery disease in patients who underwent stress myocardial perfusion imaging

Pretest probability of coronary artery disease (CAD) facilitates diagnosis and risk stratification of CAD. Stress myocardial perfusion imaging (MPI) and chronic kidney disease (CKD) are established major predictors of cardiovascular events. However, the role of CKD to assess pretest probability of CAD has been unclear. This study evaluates the role of CKD to assess the predictive value of cardiovascular events under consideration of pretest probability in patients who underwent stress MPI. Patients with no history of CAD underwent stress MPI (n = 310; male = 166; age = 70; CKD = 111; low/intermediate/high pretest probability = 17/194/99) and were followed for 24 months. Cardiovascular events included cardiac death and nonfatal acute coronary syndrome. Cardiovascular events occurred in 15 of the 310 patients (4.8 %), but not in those with low pretest probability which included 2 CKD patients. In patients with intermediate to high pretest probability (n = 293), multivariate Cox regression analysis identified only CKD [hazard ratio (HR) = 4.88; P = 0.022) and summed stress score of stress MPI (HR = 1.50; P < 0.001) as independent and significant predictors of cardiovascular events. Cardiovascular events were not observed in patients with low pretest probability. In patients with intermediate to high pretest probability, CKD and stress MPI are independent predictors of cardiovascular events considering the pretest probability of CAD in patients with no history of CAD. In assessing pretest probability of CAD, CKD might be an important factor for assessing future cardiovascular prognosis.

Impact of chronic kidney disease and stress myocardial perfusion imaging as a predictor of cardiovascular events

BACKGROUND

Stress myocardial perfusion imaging (MPI) is an established means of predicting cardiovascular events and is suitable in chronic kidney disease (CKD) patients. We aimed to evaluate the prognostic value of CKD parameters and an abnormal stress MPI for cardiovascular events.

METHODS

A total of 495 patients with suspected coronary artery disease (CAD) or history of CAD including 130 CKD patients not undergoing hemodialysis, underwent stress MPI (313 males, mean age 70 years) and were followed up for 14 months (mean period). CKD was defined as an estimated GFR of <60 ml/min/1.73 m(2) and/or persistent proteinuria. Cardiovascular events were defined as sudden cardiac death, acute coronary syndrome and congestive heart failure requiring hospitalization.

RESULTS

Cardiovascular events occurred in 41 (8.3%) patients. Multivariate Cox regression analysis indicated that CKD [hazard ratio (HR) = 3.76, p < 0.001] and a stress MPI summed difference score (SDS) of ≥2 (HR = 3.78, p < 0.001) were independent predictors of cardiovascular events; CKD plus abnormal stress MPI was also a strong predictor of cardiovascular events (non-CKD and SDS <2 vs. CKD and SDS ≥2, HR = 15.9, p < 0.001).

CONCLUSION

Both CKD and myocardial ischemia detected by stress MPI are independent predictors for cardiovascular events. Coexistence of CKD and myocardial ischemia detected by stress MPI is more useful for short-term risk stratification of cardiovascular events.

Clinical use of nuclear cardiology in the assessment of heart failure

A nuclear cardiology test is the most commonly performed non-invasive cardiac imaging test in patients with heart failure, and it plays a pivotal role in their assessment and management. Quantitative gated single positron emission computed tomography (QGS) is used to assess quantitatively cardiac volume, left ventricular ejection fraction (LVEF), stroke volume, and cardiac diastolic function. Resting and stress myocardial perfusion imaging, with exercise or pharmacologic stress, plays a fundamental role in distinguishing ischemic from non-ischemic etiology of heart failure, and in demonstrating myocardial viability. Diastolic heart failure also termed as heart failure with a preserved LVEF is readily identified by nuclear cardiology techniques and can accurately be estimated by peak filling rate (PFR) and time to PFR. Movement of the left ventricle can also be readily assessed by QGS, with newer techniques such as three-dimensional, wall thickening evaluation aiding its assessment. Myocardial perfusion imaging is also commonly used to identify candidates for implantable cardiac defibrillator and cardiac resynchronization therapies. Neurotransmitter imaging using (123)I-metaiodobenzylguanidine offers prognostic information in patients with heart failure. Metabolism and function in the heart are closely related, and energy substrate metabolism is a potential target of medical therapies to improve cardiac function in patients with heart failure. Cardiac metabolic imaging using (123)I-15-(p-iodophenyl)3-R, S-methylpentadecacoic acid is a commonly used tracer in clinical studies to diagnose metabolic heart failure. Nuclear cardiology tests, including neurotransmitter imaging and metabolic imaging, are now easily preformed with new tracers to refine heart failure diagnosis. Nuclear cardiology studies contribute significantly to guiding management decisions for identifying cardiac risk in patients with heart failure.

The use of perfusion scintigraphy to differentiate proximal right coronary artery stenosis from distal right coronary artery stenosis in patients with inferior left ventricular ischaemia

OBJECTIVE

The identification of patients with a significant proximal right coronary artery (RCA) is of clinical relevance since it may direct diagnostic and therapeutic strategies. This study was performed to determine parameters of (201)Tl RV perfusion SPECT which can be used to discriminate between proximal and distal RCA stenosis in patients with inferior left ventricular (LV) ischaemia. In addition, feasibility and reproducibility of a new semi-quantitative method for the assessment of RV perfusion were evaluated.

METHODS

Inferior LV ischaemia was due to a single distal RCA stenosis in 10 (group I) and proximal RCA stenosis in 27 patients (group II). Twenty patients with normal (201)Tl myocardial perfusion scintigraphy and low likelihood of cardiovascular disease were used as a reference (group III).

RESULTS

RV (201)Tl stress uptake did not differ between the three groups. However, group II showed a significantly higher (201)Tl rest uptake indicating RV redistribution whereas in group I and III tracer washout was shown. Extent and severity of LV inferior ischaemia was not different between groups I and II. RV redistribution has a sensitivity of 0.74, a specificity of 0.80, and an overall agreement of 0.76 for detecting proximal RCA stenosis. The feasibility of the assessment of RV (201)Tl perfusion was 94%. Inter-observer and intra-observer coefficients of variation for RV (201)Tl perfusion assessment were 1.5 and 2.4%, respectively.

CONCLUSION

RV (201)Tl perfusion scintigraphy is feasible and reproducible. RV (201)Tl redistribution can be used to discriminate between proximal and distal RCA stenosis in patients with inferior LV ischaemia.

Selection of patients for myocardial perfusion scintigraphy based on fuzzy sets theory applied to clinical-epidemiological data and treadmill test results

Coronary artery disease (CAD) is a worldwide leading cause of death. The standard method for evaluating critical partial occlusions is coronary arteriography, a catheterization technique which is invasive, time consuming, and costly. There are noninvasive approaches for the early detection of CAD. The basis for the noninvasive diagnosis of CAD has been laid in a sequential analysis of the risk factors, and the results of the treadmill test and myocardial perfusion scintigraphy (MPS). Many investigators have demonstrated that the diagnostic applications of MPS are appropriate for patients who have an intermediate likelihood of disease. Although this information is useful, it is only partially utilized in clinical practice due to the difficulty to properly classify the patients. Since the seminal work of Lotfi Zadeh, fuzzy logic has been applied in numerous areas. In the present study, we proposed and tested a model to select patients for MPS based on fuzzy sets theory. A group of 1053 patients was used to develop the model and another group of 1045 patients was used to test it. Receiver operating characteristic curves were used to compare the performance of the fuzzy model against expert physician opinions, and showed that the performance of the fuzzy model was equal or superior to that of the physicians. Therefore, we conclude that the fuzzy model could be a useful tool to assist the general practitioner in the selection of patients for MPS.

Chest pain from gastroesophageal reflux disease in patients with coronary artery disease

Management of patients with coronary artery disease is a major challenge for physicians, patients, and the healthcare system. Chest pain experienced by patients with coronary disease can be of noncardiac origin, and symptoms frequently related to gastroesophageal etiologies. The distal esophagus and the heart share a common afferent nerve supply, suggesting that location and radiation of perceived pain may be identical. In addition, there is substantial overlap between the prevalence of coronary disease and gastroesophageal reflux disease. Many physicians, including cardiologists, prescribe acid-reducing therapy to coronary patients. However, no prospective, randomized studies to date have evaluated the potential benefit of such treatments to prevent chest pain symptoms for these patients. We review the studies on noncardiac chest pain demonstrating reflux in patients with and without coronary disease. Also, the association of reflux with exertional chest pain and cardiac syndrome X is discussed. A rationale is presented for prevention of noncardiac chest pain in coronary patients, and the potential role of acid-suppressive therapy in managing these patients is discussed.

Prognostic implications of atrial fibrillation in patients undergoing myocardial perfusion single-photon emission computed tomography

OBJECTIVES

The aim of this research was to determine whether presence of atrial fibrillation (AF) provides incremental prognostic information relative to myocardial perfusion single-photon emission computed tomography (MPS) with respect to risk of cardiac death (CD).

BACKGROUND

The prognostic significance of AF in patients undergoing MPS is not known.

METHODS

A total of 16,048 consecutive patients undergoing MPS were followed-up for a mean of 2.21 +/- 1.15 years for the development of CD. Of those, 384 patients (2.4%) had AF. Cox proportional hazards method was used to compare clinical and perfusion data for the prediction of CD in patients with and without AF.

RESULTS

Atrial fibrillation was a significant predictor of CD in patients with normal (1.6% per year vs. 0.4% per year in non-AF patients), mildly abnormal (6.3% per year vs. 1.2% per year), and severely abnormal MPS (6.4% per year vs. 3.7% per year) (p < 0.001 for all). By multivariable analysis, AF patients had worse survival (p = 0.001) even after adjustment for the variables most predictive of CD: age, diabetes, shortness of breath, use of vasodilator stress, rest heart rate, and the nuclear variables. In the 4,239 patients with left ventricular ejection fraction evaluated by gated MPS, AF demonstrated incremental prognostic value not only over clinical and nuclear variables, but also over left ventricular ejection in predicting CD (p = 0.014).

CONCLUSIONS

The presence of AF independently increases the risk of cardiac events over perfusion and function variables in patients undergoing MPS. Patients with AF have a high risk of CD, even when MPS is only mildly abnormal. Whether patients with AF and mildly abnormal MPS constitute a group more deserving of early referral to cardiac catheterization is a question warranting further study.

Role of myocardial perfusion imaging for risk stratification in suspected or known coronary artery disease

Nuclear cardiology is an evolving specialty that has recently benefited from technological and radiopharmaceutical advances. As a result there has been an increase in the accuracy of myocardial perfusion imaging (MPI) with gated single photon emission computed tomography (SPECT) for assessing the diagnosis and prognosis of coronary artery disease. Moreover, ECG gated SPECT allows the simultaneous assessment of both myocardial perfusion and left ventricular function, which provides additional prognostic value. With increasing concern over early detection of coronary artery disease and its effective treatment, myocardial perfusion imaging is ideally placed to provide a full "one stop" functional assessment for any patient, irrespective of their exercise capacity. This applies not only to patients with chest pain but also to those with myocardial infarction, revascularisation, and heart failure, and those being assessed for non-cardiac surgery. The focus of this review is the use of myocardial perfusion imaging in risk stratification for coronary artery disease.

Principal uses of myocardial perfusion scintigraphy in the management of patients with known or suspected coronary artery disease

The use of myocardial perfusion single photon emission computed tomography (SPECT) has undergone considerable expansion and evolution over the past 2 decades. Although myocardial perfusion imaging was first conceived as a noninvasive diagnostic tool for determining the presence or absence of coronary artery disease, its prognostic value is now well established. Thus, identification of patients at risk for future cardiac events has become a primary objective in the noninvasive evaluation of patients with chest pain syndromes and among patients with known coronary artery disease. In particular, the ability of myocardial perfusion SPECT to identify patients at low (< 1%), intermediate (1% to 5%) or high (> 5%) risk for future cardiac events is essential to patient management decisions. Moreover, previous studies have conclusively shown the incremental prognostic value of myocardial perfusion SPECT over clinical and treadmill exercise data in predicting future cardiac events. This report addresses the current role and new developments, with respect to the use of myocardial perfusion imaging, in determining patient risk for cardiac events and the cost-effective integration of such information into patient management decisions.

Evaluation of chest pain in patients with low to intermediate pretest probability of coronary artery disease by electron beam computed tomography

Despite its limited sensitivity and specificity in patients with low to intermediate probability of coronary artery disease (CAD), exercise treadmill testing (ETT) is frequently used as the initial test for investigation of chest pain. Although myocardial perfusion imaging is a significantly more accurate test, its added cost to ETT is considerable. The cost of a non-contrast electron beam computed tomography (EBCT) scan is comparable to that of ETT and the calcium score (CS) correlates closely with the volume of atherosclerotic plaque. Therefore, we tested the hypothesis that EBCT might be an effective and cost-beneficial technique for the identification of angiographically obstructive CAD (> or = 50% stenosis) in patients with low to intermediate pretest probability of disease. We calculated the theoretic cost of attaining a diagnosis of CAD based on a Bayesian model that utilizes published sensitivity and specificity levels for ETT, EBCT, and stress myocardial perfusion imaging. We then submitted a cohort of 207 patients with low to intermediate probability of disease both to EBCT and ETT in random order, and estimated the cost of achieving a correct diagnosis by either route based on the number of expected further tests. An EBCT calcium score of 150 was chosen as a cut-point with a sensitivity of 74% and a specificity of 89% for the presence of obstructive CAD. The theoretic Bayesian model predicted substantial cost savings when EBCT was used as the initial test instead of ETT, with decreasing benefit as the prevalence of disease increased (44% saving at 0% prevalence; 15% saving at 100% prevalence). In the patient cohort, the diagnostic pathway starting with EBCT provided a 45% to 65% cost saving over the ETT pathway. We conclude that in patients with low to intermediate pretest probability of disease, a pathway based on EBCT as the initial test to investigate presence of obstructive CAD provides a substantial cost benefit over a pathway based on ETT. Such cost advantages decrease as the prevalence of disease increases.

The role of nuclear cardiology in clinical decision making

This review suggests that the field of nuclear cardiology is alive, well, and thriving, providing relevant information that aids in everyday clinical decision making for nuclear medicine and referring physicians alike. Despite the competition from other modalities, the clinically appropriate applications of nuclear cardiology techniques are likely to increase. The foundation of this optimism is based on the vast amount of data documenting cost-effective clinical applications for diagnosis, risk stratification, and assessing therapy in both chronic and acute coronary artery disease (CAD), the powerful objective quantitative analysis of perfusion and function provided by the technique, and the increasing general availability of the approach.