Prognostic implications of myocardial perfusion single-photon emission computed tomography in the elderly

BACKGROUND

The goal of this study was to assess the clinical value of stress myocardial perfusion scintigraphy (MPS) in elderly patients (> or =75 years of age).

METHODS AND RESULTS

We followed up 5200 elderly patients (41% exercise) after dual-isotope MPS over 2.8+/-1.7 years (362 cardiac deaths [CDs], 7.0%, 2.6%/y) and a subset with extended follow-up (684 patients for 6.2+/-2.9 years; 320 all-cause deaths). Survival modeling of CD revealed that both MPS-measured ischemia and fixed defect added incrementally to pre-MPS data in both adenosine and exercise stress patients. Modeling a subset with gated MPS (n=2472) revealed that ejection fraction and perfusion data added incrementally to each other, further enhancing risk stratification. Unadjusted, annualized post-normal MPS CD rate was 1.3% but <1% in patients with normal rest ECG, exercise stress, or age of 75 to 84 years and was 2.3% to 3.7% in patients > or =85 years of age or undergoing pharmacological stress. However, compared with age-matched US population CD rates (75 to 84 years of age, 1.5%; > or =85 years, 4.8%), normal MPS CD rates were approximately one-third lower than the baseline risk of US individuals (both P<0.05). Modeling of all-cause death in 684 patients with extended follow-up revealed that after risk adjustment, an interaction between early treatment and ischemia was present; increasing ischemia was associated with increasing survival with early revascularization, whereas in the setting of little or no ischemia, medical therapy had improved outcomes.

CONCLUSIONS

Stress MPS effectively stratifies CD risk in elderly patients and may identify optimal post-MPS therapy. CD rates after normal MPS are low in all subsets in relative terms compared with the age-matched US population.

The study of myocardial perfusion and coronary anatomy imaging roles in CAD (SPARC): design, rationale, and baseline patient characteristics of a prospective, multicenter observational registry comparing PET, SPECT, and CTA for resource utilization and clinical outcomes

OBJECTIVES

To design a multicenter study comparing the prognostic value and post-test resource utilization of PET, CT Coronary Angiography (CTA), and SPECT in clinical practice.

BACKGROUND

Although PET, CTA, and SPECT are widely used, their relative clinical- and cost-effectiveness are undefined.

METHODS

The Study of Myocardial Perfusion and Coronary Anatomy Imaging Roles in CAD (SPARC) is a prospective, multicenter, observational registry that has enrolled 3019 patients undergoing clinically referred SPECT, PET, and CTA with the goal of comparing posttest resource utilization and comparative prognostic value. Resource utilization assessment will enroll intermediate-high likelihood patients without prior CAD, while prognostic assessment will include both these patients and patients with prior CAD. Secondary analyses include assessments of diagnostic accuracy, cost, and referral to revascularization. Sites recruited into at least two of the three imaging arms. Except for semi-quantitative interpretation, site protocols will be used for all imaging studies and images forwarded to an image repository. Follow-up for catheterization, revascularization, cardiac death, myocardial infarction, all-cause death and medication use changes will be performed at 90-day, 1, and 2 years. Standard statistical methods will be used to risk-adjust results within and between study arms. SPARC will have >85% power (two-sided test, alpha = 0.01) to detect a 5% catheterization rate difference at 90 days between the three arms and >90% power to detect a 2% difference in cardiac death, or nonfatal MI within 2 years of the index test.

Incremental prognostic value of gated Rb-82 positron emission tomography myocardial perfusion imaging over clinical variables and rest LVEF

OBJECTIVES

This investigation sought to study the incremental value of gated rubidium (Rb)-82 positron emission tomography (PET) myocardial perfusion imaging (MPI) over clinical variables for predicting survival and future cardiac events.

BACKGROUND

The prognostic value of Rb-82 PET-MPI and left ventricular ejection fraction (LVEF) reserve (stress minus rest LVEF) is not well defined.

METHODS

1,432 consecutive patients undergoing gated rest/vasodilator stress rubidium-82 PET were followed up for at least 1 year. Of these, rest and peak stress LVEF and LVEF reserve were available in 985 patients. Cardiac events (CE) including cardiac death or nonfatal myocardial infarction and all-cause death were assessed.

RESULTS

Over a mean follow-up of 1.7 +/- 0.7 years, 83 (5.8%) CE and 140 (9.7%) all-cause death were observed. There was an increase in risk for both end points with an increasing percentage of abnormal and ischemic myocardium. With normal, mild, moderate, or severely ischemic scans, the observed annualized rates of CE were 0.7%, 5.5%, 5%, and 11% and of all-cause death were 3.3%, 7.2%, 6.9%, and 12.5%, respectively. In 985 patients with peak stress gated data, the observed annualized rates of CE (2.1% vs. 5.3%, p < 0.001) and all-cause death (4.3% vs. 9.2%, p < 0.001) were higher in patients with an LVEF reserve <0% compared with those with an LVEF reserve >or=0%. On Cox proportional hazards analysis, after consideration of clinical, historical, and rest LVEF information, stress PET results and LVEF reserve yielded incremental prognostic value with respect to both CE and all-cause death.

CONCLUSIONS

Vasodilator stress Rb-82 PET-MPI provides incremental prognostic value to historical/clinical variables and rest LVEF to predict survival free of CE and all-cause death. An increasing percentage of ischemia on PET-MPI is associated with an increase in the risk of CE and all-cause death. Left ventricular ejection fraction reserve provides significant independent and incremental value to Rb-82 MPI for predicting the risk of future adverse events.

Incremental prognostic value of myocardial perfusion imaging in patients referred to stress single-photon emission computed tomography with renal dysfunction

BACKGROUND

Coronary artery disease is the main cause of mortality and morbidity in patients with impaired renal function. The aim of this study was to evaluate the prognostic implications of single-photon emission computed tomography myocardial perfusion imaging (SPECT-MPI) in patients with impaired renal function.

METHODS AND RESULTS

We included 7348 consecutive patients (mean age, 64+/-13 years; 51% men) referred for SPECT-MPI between March 2002 and October 2006. Renal function was estimated using the estimated glomerular filtration rate formula. Patients were followed up for the incidence of all-cause mortality. Patients with decreased glomerular filtration rate were more often older, with higher prevalence of conventional risk factors (P<0.001). After a median follow-up of 2.6 years (25th to 75th percentiles, 1.5 to 3.7), 693 (9.4%) patients died. The risk of death increased with worsening kidney function. At each stage of impaired renal function, patients with abnormal SPECT-MPI had increased hazard of adverse events (P<0.0001). Using Cox proportional hazards analysis, the magnitude of total perfusion deficit and ischemia on MPI were associated with worse outcome after adjusting for confounding variables including glomerular filtration rate and ejection fraction.

CONCLUSIONS

SPECT-MPI adds modest incremental prognostic information to identify patients at higher relative risk of death across a wide spectrum of renal function.

Threshold, incidence, and predictors of prognostically high-risk silent ischemia in asymptomatic patients without prior diagnosis of coronary artery disease

BACKGROUND

Little is known about incidence, threshold, and predictors of prognostically relevant silent ischemia (SI). The aim was to study these three aspects of silent coronary artery disease (CAD).

METHODS

In total, 3,664 consecutive asymptomatic patients without prior diagnosis of CAD undergoing myocardial perfusion SPECT (MPS) were evaluated and followed-up > or = 1 year for Events (HE): cardiac death or myocardial infarction. MPS was interpreted using a 20 segment model to define summed stress, rest, and difference scores (the extent of % myocardium ischemic was derived). Prognostic high-risk ischemia was defined as ischemia consistent with a HE rate > or = 3%.

RESULTS

Overall, > or = 7.5% myocardium ischemic was consistent with high risk. Twenty-one and six percent of patients had ischemia and high-risk ischemia, respectively. Patients with high-risk ischemia had a worse prognosis than patients with less SI, HE rate of 3.1 and 0.4%, respectively, (P = .0001). Sex, age, diabetes, hypertension, abnormal resting ECG, angina, peak heart rate, blood pressure during treadmill testing, ST-depression, and Duke treadmill score were independent predictors of relevant SI.

CONCLUSIONS

In total, > or = 7.5% myocardium ischemic revealed to be consistent with high risk. Six percent of patients had evidence of high-risk SI. Diagnostic scores are provided to most likely identify patients with high-risk SI.

Quantitative assessment of myocardial perfusion abnormality on SPECT myocardial perfusion imaging is more reproducible than expert visual analysis

BACKGROUND

Current guidelines of Food and Drug Administration for the evaluation of SPECT myocardial perfusion imaging (MPI) in clinical trials recommend independent visual interpretation by multiple experts. Few studies have addressed whether quantitative SPECT MPI assessment would be more reproducible for this application.

METHODS AND RESULTS

We studied 31 patients (age 68 +/- 13, 25 male) with abnormal stress MPI who underwent repeat exercise (n = 11) or adenosine (n = 20) MPI within 9-22 months (mean 14.9 +/- 3.8 months) and had no interval revascularization or myocardial infarction and no change in symptoms, stress type, rest or stress ECG, or clinical response to stress on the second study. Visual interpretation per FDA Guidance used 17-segment, 5-point scoring by two independent expert readers with overread of discordance by a third expert, and percent myocardium abnormal was derived from normalized summed scores. The quantitative magnitude of perfusion abnormality was assessed by the total perfusion deficit (TPD), expressing stress, rest, and ischemic perfusion abnormality. High linear correlations were observed between visual and quantitative size of stress, rest, and ischemic defects (R = 0.94, 0.92, 0.84). Correlations of two tests were higher by quantitative than by visual methods for stress (R = 0.97 vs R = 0.91, P = 0.03) and rest defects (R = 0.94 vs R = 0.82, P = 0.03), respectively, and statistically similar for ischemic defects (R = 0.84 vs R = 0.70, P = ns).

CONCLUSIONS

In stable patients having serial SPECT MPI, quantification is more reproducible than visual for magnitude of perfusion abnormality, suggesting its superiority for use in randomized clinical trials and monitoring the effects of therapy in an individual patient.

Interrelation of coronary calcification, myocardial ischemia, and outcomes in patients with intermediate likelihood of coronary artery disease: a combined positron emission tomography/computed tomography study

BACKGROUND

Although the value of coronary artery calcium (CAC) for atherosclerosis screening is gaining acceptance, its efficacy in predicting flow-limiting coronary artery disease remains controversial, and its incremental prognostic value over myocardial perfusion is not well established.

METHODS AND RESULTS

We evaluated 695 consecutive intermediate-risk patients undergoing combined rest-stress rubidium 82 positron emission tomography (PET) perfusion imaging and CAC scoring on a hybrid PET-computed tomography (CT) scanner. The frequency of abnormal scans among patients with a CAC score > or = 400 was higher than that in patients with a CAC score of 1 to 399 (48.5% versus 21.7%, P<0.001). Multivariate logistic regression supported the concept of a threshold CAC score > or = 400 governing this relationship (odds ratio 2.91, P<0.001); however, the frequency of ischemia among patients with no CAC was 16.0%, and its absence only afforded a negative predictive value of 84.0%. Risk-adjusted survival analysis demonstrated a stepwise increase in event rates (death and myocardial infarction) with increasing CAC scores in patients with and without ischemia on PET myocardial perfusion imaging. Among patients with normal PET myocardial perfusion imaging, the annualized event rate in patients with no CAC was lower than in those with a CAC score > or = 1000 (2.6% versus 12.3%, respectively). Likewise, in patients with ischemia on PET myocardial perfusion imaging, the annualized event rate in those with no CAC was lower than among patients with a CAC score > or = 1000 (8.2% versus 22.1%).

CONCLUSIONS

Although increasing CAC content is generally predictive of a higher likelihood of ischemia, its absence does not completely eliminate the possibility of flow-limiting coronary artery disease. Importantly, a stepwise increase occurs in the risk of adverse events with increasing CAC scores in patients with and without ischemia on PET myocardial perfusion imaging.

Added Value of Rest to Stress Study for Recognition of Artifacts in Perfusion Cardiovascular Magnetic Resonance

BACKGROUND

The objective was to determine whether rest perfusion (RP) adds to stress perfusion (SP) and late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR) for detection of impaired coronary flow reserve.

METHODS

We enrolled patients (n=45) referred for myocardial perfusion SPECT (MPS) for adenosine CMR stress. SP, RP and LGE images were obtained with 99mTc sestamibi injection during a single adenosine infusion. Segmental perfusion and confidence scores were recorded for SP-LGE interpreted with and without RP. CMR agreement with MPS was determined.

RESULTS

MPS was normal in 653 and abnormal in 67 segments. SP-LGE CMR interpreted without RP was normal in 407, abnormal in 313 segments, and showed poor agreement with MPS (58%). Two hundred thirty-seven segments were changed to normal using data from RP, improving agreement (87%, p<0.0001). Reader confidence was low in 33 patients with SP-LGE and improved in 26 patients using SP-RP-LGE, where 37/45 were read with high confidence. Artifact was present in 68% of SP CMR and accounted for false positive studies.

CONCLUSION

Agreement between single stress adenosine CMR and MPS is optimized by combining RP, LGE and SP CMR. Addition of RP CMR to SP-LGE CMR improved agreement with MPS and reader confidence. Improved CMR pulse sequences may change the role of rest perfusion data.

Predicting therapeutic benefit from myocardial revascularization procedures: are measurements of both resting left ventricular ejection fraction and stress-induced myocardial ischemia necessary?

BACKGROUND

We hypothesized that ejection fraction (EF) best predicts cardiovascular death but only measures of ischemia predict relative survival benefit from revascularization compared with medical therapy.

METHODS AND RESULTS

We followed up 5366 consecutive patients without prior revascularization who underwent stress electrocardiography-gated myocardial perfusion single photon emission computed tomography (MPS) for 2.8 +/- 1.2 years, during which 146 cardiac deaths occurred (2.7%, 1.0%/y). The treatment received within 60 days after MPS was used to define the subgroups (revascularization in 402 patients, with cardiac death occurring in 6.2%, vs medical therapy in 4964 patients, with cardiac death occurring in 2.4%; P < .0001, chi2 = 18.7). Adjustment for nonrandomized treatment assignment used a propensity score based on logistic regression modeling of referral to revascularization. The percent of myocardium that was ischemic was the most important predictor of revascularization. The overall model (multivariate chi2 = 728, c index = 0.89, P < 10(-5)) was used as a propensity score. Cox proportional hazards analysis, assessing the relationship between MPS results, non-MPS covariates, and cardiac death, revealed that EF was superior to percent ischemic myocardium in the prediction of cardiac death after adjustment for pre-MPS data and the propensity score. However, an interaction between percent ischemic myocardium and revascularization was present such that, irrespective of EF, patients with little or no ischemia had an improved survival rate with medical therapy, whereas with increasing ischemia, progressive improvements in survival rate were noted with revascularization.

CONCLUSIONS

Although EF predicts cardiac death, only inducible ischemia identifies which patients have a short-term benefit from revascularization.

Comparative Use of Radionuclide Stress Testing, Coronary Artery Calcium Scanning, and Noninvasive Coronary Angiography for Diagnostic and Prognostic Cardiac Assessment

Noninvasive cardiac imaging has undergone a recent resurgence with the development of new approaches for imaging coronary atherosclerosis. Non-contrast computed tomography (CT) for imaging the extent of coronary artery calcification (CAC) and contrast CT for noninvasive coronary angiography (CTA) are developments with a growing evidence base regarding risk assessment and the diagnosis of obstructive coronary disease. This review discusses the role of CAC for risk assessment of asymptomatic individuals and for the use of coronary CTA in symptomatic patients. By comparison, gated myocardial perfusion scintigraphy (MPS) is a well-established noninvasive imaging modality that is a core element in evaluation of patients with stable chest pain syndromes. Stress MPS is the most commonly used stress imaging technique for patients with suspected or known coronary disease. In contrast to the nascent evidence noted with coronary CTA, MPS has a robust evidence base, including the support of numerous clinical guidelines. We highlight the current evidence supporting the diagnostic accuracy and risk stratification data for MPS for symptomatic patients with known or suspected coronary artery disease. It is likely that assessing the extent of atherosclerosis using CAC or coronary CTA will become an increasing part of mainstream cardiovascular imaging practices. In some patients, further ischemia testing with MPS will be required. Similarly, in some patients referred for MPS, anatomic definition of atherosclerosis using CAC by CT may be appropriate. Thus, this review also provides a synopsis of the available literature on imaging that integrates both CT and MPS in combined strategies for the assessment of atherosclerotic and obstructive coronary disease burden. We also propose possible risk-based strategies through which imaging might be used to identifying candidates for more intensive prevention and risk factor modification strategies as well as those who would benefit from referral to coronary angiography and revascularization.

Role of nuclear cardiology in advancing cardiac surgery

Cardiac surgeons are commonly faced with issues regarding the balance between the potential risk and the potential benefit of a surgical procedure. Nuclear cardiology procedures [myocardial perfusion SPECT (MPS) and positron emission tomography (PET)] provide the surgeon with objective information that augments standard clinical and angiographic assessments with respect to diagnosis, prognosis, and potential benefit from intervention. Development of the technology and methodology of gated MPS acquisition and interpretation allows assessment of the extent and severity of hypoperfused but viable myocardium, as well as global LVEF and LV volume measurements, diastolic function, and LV geometry. With PET, myocardial metabolism and blood flow reserve can also be measured. This chapter provides insight into the current evidence regarding settings in which nuclear cardiology procedures are helpful to the surgeon in assessment of patients having or being considered for cardiac surgery in the setting of coronary artery disease (CAD). Overall, a risk-benefit approach to MPS results is proposed, with principal focus on identifying patients at risk for major cardiac events who may benefit from a surgical procedure.

Roles of nuclear cardiology, cardiac computed tomography, and cardiac magnetic resonance: Noninvasive risk stratification and a conceptual framework for the selection of noninvasive imaging tests in patients with known or suspected coronary artery disease

This review deals with noninvasive imaging for risk stratification and with a conceptual approach to the selection of noninvasive tests in patients with suspected or known chronic coronary artery disease (CAD). Already widely acknowledged with SPECT, there is an increasing body of literature data demonstrating that CT coronary calcium assessment is also of prognostic value. The amount of coronary atherosclerosis, as can be extrapolated from CT coronary calcium score, has been shown to be highly predictive of cardiac events. The principal difference between myocardial perfusion SPECT (MPS) and CT coronary calcium for prognostic application appears to be that the former is an excellent tool for assessing short-term risk, thus effectively guiding decisions regarding revascularization. In contrast, the atherosclerosis imaging methods are likely to provide greater long-term risk assessment and, thus, are more useful in determination of the need for aggressive medical prevention measures. Although the more recent development of CT coronary angiography is promising for diagnosis, there has been no information to date regarding the prognostic value of the CT angiographic data. Similarly, cardiac MRI has not yet been adequately studied for its prognostic content. The selection of the most appropriate test for a given patient depends on the specific question being asked. In patients with a very low likelihood of CAD, no imaging test may be required. In screening the remaining asymptomatic patients, atherosclerosis imaging may be beneficial. In symptomatic patients, MPS, CT coronary angiography, and cardiac MRI play important roles. We consider it likely that, with an increased emphasis on prevention and a concomitant aging of the population, many forms of noninvasive cardiac imaging will continue to grow, with nuclear cardiology continuing to grow.

Impact of Body Mass Index on Cardiac Mortality in Patients With Known or Suspected Coronary Artery Disease Undergoing Myocardial Perfusion Single-Photon Emission Computed Tomography

OBJECTIVES

The purpose of this study was to assess the relationship between body mass index (BMI) and the prognostic value of myocardial perfusion single-photon emission computed tomography (MPS).

BACKGROUND

The prognostic value of MPS in the obese has not been evaluated.

METHODS

We studied 4,720 patients with and 10,019 patients without known coronary artery disease (CAD) who underwent rest Tl-201/stress Tc-99m sestamibi MPS, including 5,233 gated MPS studies and followed up (mean 2.7 to 3.2 years). Patients were categorized as normal weight (BMI 18.5 to 24.9 kg/m2), overweight (BMI 25.0 to 29.9 kg/m2), or obese (BMI > or =30.0 kg/m2).

RESULTS

Unadjusted annual rates of cardiac death (CD) rose versus stress MPS abnormalities in all weight groups (p < 0.001). Obese or overweight patients with or without known CAD who had normal MPS were at low CD risk (<1%/year), similar to normal weight patients. In CAD, obese and overweight patients with abnormal MPS had lower rates of CD compared with normal weight patients (p < 0.01). In patients with low ejection fraction (EF) by gated MPS, those with normal weight had highest CD rate (p = 0.001). Multivariable models revealed that BMI was not a predictor of CD in suspected CAD patients (hazard ratio [HR] 0.99; 95% confidence interval [CI] 0.95 to 1.02) but was an independent inverse predictor of CD in known CAD patients (HR 0.95; 95% CI 0.92 to 0.98), especially in women, adenosine stress, low EF, or abnormal perfusion.

CONCLUSIONS

Normal MPS was associated with low risk of CD in patients of all weight categories. In patients with known CAD undergoing MPS, obese and overweight patients were at lower risk of CD over three years than normal weight patients.