Prognostic implications of stress modality on mortality risk and cause of death in patients undergoing office-based SPECT myocardial perfusion imaging

Comparative predictors of mortality among patients referred for stress single-photon emission computed tomography versus positron emission tomography myocardial perfusion imaging

BACKGROUND

There is currently little information regarding the usage and comparative predictors of mortality among patients referred for single-photon emission computed tomography (SPECT) versus positron emission tomography (PET) myocardial perfusion imaging (MPI) within multimodality imaging laboratories.

METHODS

We compared the clinical characteristics and mortality outcomes among 15,718 patients referred for SPECT-MPI and 6202 patients referred for PET-MPI between 2008 and 2017.

RESULTS

Approximately two-thirds of MPI studies were performed using SPECT-MPI. The PET-MPI group was substantially older and included more patients with known coronary artery disease (CAD), hypertension, diabetes, and myocardial ischemia. The annualized mortality rate was also higher in the PET-MPI group, and this difference persisted after propensity matching 3615 SPECT-MPI and 3615 PET-MPI patients to have similar clinical profiles. Among the SPECT-MPI patients, the most potent predictor of mortality was exercise ability and performance, including consideration of patients' mode of stress testing and exercise duration. Among the PET-MPI patients, myocardial flow reserve (MFR) was the most potent predictor of mortality.

CONCLUSIONS

In our real-world setting, PET-MPI was more commonly employed among older patients with more cardiac risk factors than SPECT-MPI patients. The most potent predictors of mortality in our SPECT and PET-MPI groups were variables exclusive to each test: exercise ability/capacity for SPECT-MPI patients and MFR for PET-MPI patients.

Economic and healthcare resource utilization assessments of PET imaging in Coronary Artery Disease diagnosis: a systematic review and discussion of opportunities for future economic evaluations

AIMS

This systematic literature review (SLR) consolidated economic and healthcare resource utilization (HCRU) evidence for positron emission tomography (PET) and single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) to inform future economic evaluations.

MATERIALS AND METHODS

An electronic search was conducted in MEDLINE, Embase, and Cochrane databases from 2012-2022. Economic and HCRU studies in adults who underwent PET- or SPECT-MPI for coronary artery disease (CAD) diagnosis were eligible. A qualitative methodological assessment of existing economic evaluations, HCRU, and downstream cardiac outcomes was completed. Exploratory meta-analyses of clinical outcomes were performed.

RESULTS

The search yielded 13,439 results, with 71 records included. Economic evaluations and comparative clinical trials were limited in number and outcome types (HCRU, downstream cardiac outcomes, and diagnostic performance) assessed. No studies included all outcome types and only one economic evaluation linked diagnostic performance to HCRU. The meta-analyses of comparative studies demonstrated significantly higher rates of early- and late-invasive coronary angiography and revascularization for PET- compared to SPECT-MPI; however, the rate of repeat testing was lower with PET-MPI. The rate of acute myocardial infarction was lower, albeit non-significant with PET- vs. SPECT-MPI.

LIMITATIONS AND CONCLUSIONS

This SLR identified economic and HCRU evaluations following PET- and SPECT-MPI for CAD diagnosis and determined that existing studies do not capture all pertinent outcome parameters or link diagnostic performance to downstream HCRU and cardiac outcomes, thus, resulting in simplified assessments of CAD burden. A limitation of this work relates to heterogeneity in study designs, patient populations, and follow-up times of existing studies. Resultingly, it was challenging to pool data in meta-analyses. Overall, this work provides a foundation for the development of comprehensive economic models for PET- and SPECT-MPI in CAD diagnosis, which should link diagnostic outcomes to HCRU and downstream cardiac events to capture the full CAD scope.

Comparison of coronary artery calcium scores among patients referred for cardiac imaging tests

BACKGROUND

While coronary artery calcium (CAC) can now be evaluated by multiple imaging modalities, there is presently scant study regarding how CAC scores may vary among populations of varying clinical risk.

METHODS

We evaluated the distribution of CAC scores among three patient groups: 18,941 referred for CAC scanning, 5101 referred for diagnostic coronary CT angiography (CCTA), and 3307 referred for diagnostic positron emission tomography (PET) myocardial perfusion imaging (MPI). We assessed the relationship between CAC score and myocardial ischemia, obstructive coronary artery disease (CAD), and all-cause mortality across imaging modalities.

RESULTS

Within each age group, the frequency of CAC abnormalities were relatively similar across testing modalities, despite an annualized mortality rate which varied from 0.5%/year among CAC patients to 3.8%/year among PET-MPI patients (p < 0.001). Among CCTA and PET-MPI patients, a zero CAC score was common, occurring in ~70% of patients <50 years, ~40% of patients 50-59 years, and ~ 25% of patients 60-69 years. Among CCTA patients, zero CAC was associated with a normal coronary angiogram with high frequency, ranging from 92.2% among patients <50 years to 87.9% among patients ≥70 years. Among PET-MPI patients, zero CAC was associated with a very low frequency of inducible ischemia across all age groups, ranging from 1.5% among patients <50 years to 0.9% among patients ≥70 years.

CONCLUSIONS

In our study, relatively similar CAC scores were noted among patients varying markedly in mortality risk. Clinically, zero CAC scores predicted both a low likelihood of obstructive CAD and inducible myocardial ischemia in all age groups and were observed with high frequency across diagnostic testing modalities.

Impact of change of ischemic burden on the outcomes of ESRD patients awaiting kidney transplantation

BACKGROUND

In asymptomatic patients with end-stage renal disease (ESRD) wait-listed for kidney transplantation (KT), it is unclear whether a change in ischemic burden on serial surveillance SPECT myocardial perfusion imaging (MPI) impacts outcome.

METHODS AND RESULTS

In a retrospective cohort of 700 asymptomatic KT candidates with ≥ 2 sequential SPECT-MPI studies, we defined a significant change in ischemic burden between MPIs as ΔSDS of ≥ 2 points. Patients were followed for mean 19 ± 12 months after MPI2 for cardiac death or myocardial infarction. Between MPIs, 29 (4%) subjects received coronary revascularization which was associated with a greater incidence of reduction in ischemic burden on MPI2 (31% vs. 17%, P = 0.049). Among 514 patients with no ischemia on MPI1 (SDS ≤ 1), 15% had new ischemia on MPI2 which was associated with increased MACE (adjusted HR 1.75; CI 1.02-3.01; P = 0.041). Among 186 patients with ischemia on MPI1 (SDS ≥ 2), 66% had improvement of ischemic burden on MPI2 which was associated with significantly lower MACE (adjusted HR 0.46; CI 0.25-0.82; P = 0.009). There was no significant interaction between coronary revascularization and improvement in ischemic burden impacting outcome (interaction P = 0.845).

CONCLUSION

Among KT candidates who underwent serial MPI for CAD surveillance, new ischemia was associated with increased MACE risk. Improvement in ischemic burden was associated with lower MACE risk irrespective of coronary revascularization status.

Cardiology and lifestyle medicine

Poor lifestyle habits, such as physical inactivity and poor diets, are highly prevalent within society and even more so among patients with chronic disease. The need to stem poor lifestyle habits has led to the development of a new field of Lifestyle Medicine, whose mission is to prevent, treat, and even reverse chronic diseases through lifestyle interventions. Three fields within Cardiology relate to this mission: Cardiac Rehabilitation, Preventive Cardiology, and Behavioral Cardiology. Each of these three fields have contributed substantially to the reduction of cardiovascular disease (CVD) morbidity and mortality. The historic contributions of these three cardiac fields are reviewed as well as the challenges each of these fields has faced in optimizing the application of lifestyle medicine practices. A shared agenda between Cardiology and the American College of Lifestyle Medicine could further the utilization of behavioral interventions. This review suggests seven steps that could be shared by these organizations and other medical societies. First, there is a need to develop and promulgate the assessment of lifestyle factors as "vital signs" during patient visits. Second, developing a strong partnership between the fields of Cardiology and Physiatry could improve important aspects of cardiac care, including a potential redesign of cardiac stress testing. Third, behavioral evaluations should be optimized at patients' entrée points into medical care since these may be considered "windows of opportunity". Fourth, there is a need to broaden cardiac rehabilitation into inexpensive programs and make this program eligible for patients with risk factors but no known CVD. Fifth, lifestyle medicine education should be integrated into the core competencies for relevant specialties. Sixth, there is a need for inter-societal advocacy to promote lifestyle medicine practices. Seventh, the well-being effects of healthy lifestyle behaviors, such as their impact on one's sense of vitality, should be emphasized.

Assessment of lifestyle-related risk factors enhances the effectiveness of cardiac stress testing

Cardiac stress tests have been widely utilized since the 1960s for the diagnostic and prognostic assessment of patients with suspected coronary artery disease (CAD). Clinical risk is primarily based on assessing the presence and magnitude of inducible myocardial ischemia. However, the primary factors driving mortality risk have changed over recent decades. Factors such as typical angina and inducible ischemia have decreased, whereas the percentage of patients with diabetes, obesity and hypertension have increased. There has also been a marked temporal increase in the percentage of patients who require pharmacologic testing due to inability to perform treadmill exercise at the time of cardiac stress testing and this need has emerged as the most potent predictor of mortality risk in contemporary stress test populations. However, the long-term clinical risk posed by the inability to perform exercise and concomitant CAD risk factors are rarely reflected in the assessment of patients' prognostic risk in cardiac stress test reports. In this review, we suggest that the clinical utility of present-day cardiac stress testing can be improved by developing a more comprehensive assessment that integrates and reports all factors which modulate patients' long-term clinical risk following stress testing. This should include assessment of patients' CAD risk factors, physical activity habits and mobility risks, identification of the reasons why patients could not exercise at the time of cardiac stress testing. In addition, the assessment of four core non-aerobic functional parameters should be considered among patients who cannot exercise: assessment of gait speed, handgrip strength, lower extremity strength, and standing balance.

Musculoskeletal exercise: Its role in promoting health and longevity

Resistance training (RT) is an often ignored but essential component of physical health.. The functioning of the musculoskeletal system declines with age, resulting in sarcopenia, loss of muscle strength and power, decrease in muscle flexibility and balance. Other pertinent age-related changes include decline in basal metabolic rate, increase in fat mass, and decrease in bone mineral density. Such primary aging can be accentuated by the concomitant presence of comorbid conditions, such as insulin resistance and diabetes, obesity, inflammatory conditions, and physical inactivity (PI). The latter is often promoted by the presence of musculoskeletal conditions, such as osteoarthritis, back pain, and osteoporosis, which are quite common in society. RT can diminish long-term joint stress, "resist" age-related physiological deterioration and improve health outcomes through its ability to increase muscle strength and mass, balance the distribution of forces within a joint, increase basal metabolic rate and bone density, reduce body fat and cardiac risk factors, enhance endothelial function, and promote cognitive function and psychological well-being. Accordingly, health providers should screen for PI, lack of RT, and mobility risks using short screening questions, and employ simple functional tests, when indicated, to evaluate patients for impairment in gait, muscle strength, flexibility, and balance. This review also provides general principles for initiating and conducting RT and provides general and specific examples of resistance training programs, which should be individualized for patients through the evaluation and guidance by appropriate health providers, physical therapists, and certified trainers.

The prognostic and diagnostic implications of surveillance serial myocardial perfusion imaging in asymptomatic renal transplant candidates

BACKGROUND

The utility of serial SPECT myocardial perfusion imaging (MPI) for CAD surveillance in asymptomatic ESRD patients awaiting kidney transplantation (KT) is uncertain.

METHODS AND RESULTS

We retrospectively investigated 700 asymptomatic KT candidates with ≥ 2 pre-transplant SPECT-MPIs (mean interval, 20 ± 13 months). Worsening MPI was defined as total perfusion deficit increase (ΔTPD) > 5%. High clinical risk was defined as ≥ 3 AHA/ACC KT risk factors. The primary outcome was major adverse cardiac events (MACE) of cardiac death or myocardial infarction. The initial MPI was normal in 462 (66%) subjects. On repeat MPI, ΔTPD > 5% was observed in 82 (12%) subjects, and the incidence increased with increasing time gap between MPIs (P = .006). During a mean follow-up of 16 ± 8 months, there were 119 (17%) MACEs. In the entire cohort, ΔTPD > 5% was not significantly associated with MACE (HR = 1.38; P = .210). ΔTPD > 5% was associated with increased MACE rate among patients with normal initial MPI (HR = 2.30; P = .005), but not among those with abnormal initial MPI (P = .260). There was a significant interaction between ΔTPD > 5% and initial MPI normalcy status in predicting MACE (interaction P = .018), such that the predictive value of ΔTPD is dependent on the initial MPI normalcy. Among subjects with normal initial MPI, ΔTPD > 5% was significantly associated with MACE only if the sum of KT risk factors was ≥ 3 (HR = 2.26; P = .016). Among 123 patients who underwent coronary angiography, ΔTPD > 5% was associated with a higher prevalence of obstructive CAD when the initial MPI was normal and the sum of KT risk factors was ≥ 3.

CONCLUSION

Among patients with ESRD waitlisted for KT, new/worsening MPI abnormalities are expected. On serial surveillance, ΔTPD > 5% is associated with MACE and obstructive CAD among those with a normal initial MPI and ≥ 3 AHA/ACC KT risk factors.

The prevalence and predictors of inducible myocardial ischemia among patients referred for radionuclide stress testing

BACKGROUND

The frequency of inducible myocardial ischemia has declined in contemporary stress test cohorts, suggesting a need to re-evaluate its optimal use. To-date, however, a comprehensive analysis of the most potent predictors of myocardial ischemia among cardiac stress test patients has not been conducted.

METHODS

We assessed 27,615 patients referred for stress-rest SPECT myocardial perfusion imaging between January 1, 2004 and December 31, 2017. Chi-square analysis was used to ascertain the most potent predictors of ischemia.

RESULTS

Among our cohort, CAD status (presence/absence of known CAD), rest left ventricular ejection fraction (LVEF), and typical angina were the most potent predictors of ischemia. The frequency of ischemia was only 6.6% among patients with an LVEF > 55% but 38.1% for patients with LVEF < 45% (P < 0.001). The frequency of myocardial ischemia was fourfold higher among patients with known CAD vs no known CAD (28.0% vs 6.5%, P < 0.001) and approximately threefold higher among patients with typical angina vs patients with atypical symptoms (P < 0.001).

CONCLUSIONS

The frequency of myocardial ischemia varies markedly according to the common clinical parameters and is particularly high among patients with known CAD, low LVEF, and typical angina. These observations may be used to develop more cost-effective strategies for referring patients for cardiac stress testing.

Cardiac imaging for the assessment of patients being evaluated for liver transplantation

Cardiac risk assessment prior to liver transplantation has become widely accepted. With the emergence of nonalcoholic steatohepatitis among the leading causes of end-stage liver disease and the steady rise of the age of liver transplant recipients, the burden of cardiovascular diseases has markedly increased in this population. Selecting appropriate liver transplant candidates is crucial due to the increasing demand for scarce donor organs. The use of noninvasive cardiac imaging for pre-operative assessment of the cardiovascular status of liver transplant recipients has been on the rise, yet the optimal assessment strategy remains an area of active debate. In this review, we examine the relevant literature pertaining to the diagnostic and prognostic applications of noninvasive cardiac imaging in this population. We also propose a simple literature-based evaluation algorithm for CAD surveillance in liver transplant candidates.

Cardiac imaging for the assessment of patients being evaluated for kidney transplantation

Cardiac risk assessment before kidney transplantation has become widely accepted. However, the optimal patient selection and screening tool for cardiac assessment remain controversial. Clinicians face several challenges in this process, including the ever-growing pre-transplant population, aging transplant candidates, increasing prevalence of coronary artery disease, and scarcity of donor organs. Optimizing the cardiovascular risk profile in kidney transplant candidates is necessary to better appropriate limited donor organs and improve patient outcomes. Increasing waiting times from the initial evaluation for transplant candidacy to the actual transplant raises questions regarding re-testing and re-stratification of risk. In this review, we summarize and discuss the current literature on cardiac evaluation prior to kidney transplantation. We also propose simple evidence-based evaluation algorithms for initial and follow-up CAD surveillance in patients being wait-listed for kidney transplantation.

Mortality risk among patients undergoing exercise versus pharmacologic myocardial perfusion imaging: A propensity-based comparison

BACKGROUND

The increased risk associated with pharmacologic versus exercise testing is obscured by the higher prevalence of clinical risk factors among pharmacologic patients. Thus, we assessed comparative mortality in a large risk factor-matched group of exercise versus pharmacologic patients undergoing stress/rest SPECT myocardial perfusion imaging (MPI).

METHODS

39,179 patients undergoing stress/rest SPECT-MPI were followed for 13.3 ± 5.0 years for all-cause mortality (ACM). We applied propensity-matching to create pharmacologic and exercise groups with similar risk profiles.

RESULTS

In comparison to exercise patients, pharmacologic patients had an increased risk-adjusted hazard ratio for ACM for each level of ischemia: increased by 3.8-fold (95%CI 3.5-4.1) among nonischemic patients, 2.5-fold (95%CI 2.0-3.2) among mildly ischemic patients, and 2.6-fold (95%CI 2.1-3.3) among moderate/severe ischemic patients. Similar findings were observed among a propensity-matched cohort of 10,113 exercise and 10,113 pharmacologic patients as well as in an additional cohort that also excluded patients with noncardiac co-morbidities.

CONCLUSIONS

Patients requiring pharmacologic stress testing manifest substantially heightened clinical risk at each level of myocardial ischemia and even when myocardial ischemia is absent. These findings suggest the need to study the pathophysiological drivers of increased risk in association with pharmacologic testing and to convey this risk in clinical reports.

The prognostic implications of ST-segment and T-wave abnormalities in patients undergoing regadenoson stress SPECT myocardial perfusion imaging

BACKGROUND

The prognostic implications of ST-segment and T-wave (ST/T) abnormalities in patients undergoing stress SPECT-myocardial perfusion imaging (MPI) are not well defined.

METHODS AND RESULTS

This was a single-center, retrospective cohort study of consecutive patients who underwent regadenoson stress SPECT-MPI. Patients with baseline electrocardiogram (ECG) abnormalities that impede ST/T analysis or those with known coronary artery disease were excluded. Patients were categorized as having primary ST abnormalities, secondary ST/T abnormalities due to ventricular hypertrophy or right bundle branch block, T-wave abnormalities, or normal ECG. The primary outcome was major adverse cardiovascular events (MACE) defined as the composite of cardiac death or myocardial infarction. Among 6,059 subjects, 1912 (32%) had baseline ST/T abnormalities. During a mean follow-up of 2.3 ± 1.9 years, the incidence of MACE was significantly higher among patients with secondary ST/T abnormalities compared to those with normal ECG (HR 2.05; 95% confidence interval [CI], 1.04-4.05; P = 0.039). No significant difference in MACE was observed among patients with primary ST abnormalities (HR 1.64; CI 0.87-3.06; P = 0.124) or T-wave abnormalities (HR 1.15; CI 0.62-2.16; P = 0.658) compared with patients who had normal ECG. Among patients with secondary ST/T changes, abnormal MPI was not associated with a significant increase in MACE rates compared to normal MPI (HR 1.18; CI 0.31-4.58; P = 0.808). However, abnormal MPI was associated with higher MACE rates among patients with primary ST abnormalities (HR 4.50; CI 1.44-14.10; P = 0.005) and T-wave abnormalities (HR 3.74; CI 1.20-11.68; P = 0.015). Similarly, myocardial ischemia on regadenoson stress SPECT-MPI was not associated with a significant increase in MACE rates in patients with secondary ST/T abnormalities (HR 1.45; CI 0.38-5.61; P = 0.588), while it was associated with a higher incidence of MACE in patients with primary ST abnormalities (HR 3.012; CI 0.95-9.53; P = 0.049) and T-wave abnormalities (HR 5.06; CI 1.60-15.96; P = 0.002).

CONCLUSION

While patients with secondary ST/T abnormalities had significantly higher MACE risk, abnormal MPI or presence of myocardial ischemia on regadenoson SPECT-MPI in this group does not add prognostic information. Patients with primary ST abnormalities and T-wave abnormalities do not seem to have a significantly higher MACE risk compared to those with normal ECG; however, abnormal MPI or presence of myocardial ischemia, in these groups, correlates with higher MACE rates.

Synergistic Assessment of Mortality Risk According to Body Mass Index and Exercise Ability and Capacity in Patients Referred for Radionuclide Stress Testing

OBJECTIVE

To determine the interrelationship between body mass index (BMI), mode of stress testing (exercise or pharmacological), exercise capacity, and all-cause mortality in patients referred for stress-rest single photon emission computed tomography myocardial perfusion imaging.

PATIENTS AND METHODS

We evaluated all-cause mortality in 21,638 patients undergoing stress-rest single photon emission computed tomography myocardial perfusion imaging between January 2, 1991, and December 31, 2012. Patients were divided into exercise and pharmacologically tested groups and 9 BMI categories. The median follow-up was 12.8 years (range, 5.0-26.8 years).

RESULTS

In exercise patients, mortality was increased with both low and high BMI vs patients with a normal referent BMI of 22.5 to 24.9 kg/m². In pharmacologically tested patients, only low BMI, but not high BMI, was associated with increased mortality vs normal BMI. When exercise and pharmacologically tested groups were compared directly, pharmacologically tested patients manifested a marked increase in mortality risk vs exercise patients within each BMI category, ranging from an approximately 4-fold increase in mortality in those with normal or high BMI to a 12.3-fold increase in those with low BMI values. Similar findings were observed in a cohort of 4804 exercise and 4804 pharmacologically tested patients matched to have similar age and coronary artery disease risk factor profiles. In exercise patients, further risk stratification was achieved when considering both BMI and metabolic equivalent tasks of achieved exercise.

CONCLUSION

The combined assessment of BMI and exercise ability and capacity provides synergistic and marked risk stratification of future mortality risk in patients referred for radionuclide stress testing, providing considerable insights into the "obesity paradox" that is observed in populations referred for stress testing.

The prognostic value of regadenoson SPECT myocardial perfusion imaging: The largest cohort to date

BACKGROUND

Data on the prognostic value of regadenoson SPECT myocardial perfusion imaging (MPI) is limited and based on small cohorts.

METHODS AND RESULTS

We conducted a single-center, retrospective cohort study of 10,275 consecutive patients who underwent regadenoson SPECT-MPI. Among the study subjects, 28.7% had abnormal MPI and 25.5% had myocardial ischemia. Patients were followed for a mean of 2.4 ± 2.2 years for major adverse cardiac events (MACE), defined as cardiac death or myocardial infarction. There was a significant stepwise increase in MACE with an increasing burden of perfusion abnormality (P < .001) and myocardial ischemia (P < .001). Abnormal MPI (adjusted HR 1.52; 95% CI 1.21 to 1.91) and myocardial ischemia (adjusted HR 1.53; 95% CI 1.25 to 1.89) were associated with MACE, independent of and incremental to clinical covariates and left ventricular ejection fraction (LVEF). Moreover, post-stress LVEF, LVEF reserve, and left ventricular end-diastolic volume added significant prognostic information. Transient ischemic dilation ≥ 1.31 did not provide incremental prognostic value (adjusted HR 1.02; P = .906).

CONCLUSION

In the largest cohort to date, we demonstrated that the presence and severity of perfusion abnormality and myocardial ischemia on regadenoson stress SPECT-MPI are associated with an independent increase in MACE.

Changing Drivers of Mortality Among Patients Referred for Cardiac Stress Testing

Objective

To identify temporal shifts in coronary artery disease (CAD) risk factor profiles, clinical parameters, and corresponding mortality rates among patients referred for radionuclide stress testing over 22 years.

Patients and Methods

We assessed 39,750 patients with suspected CAD (“diagnostic” patients) and 10,982 patients with known CAD who underwent radionuclide stress testing between January 2, 1991, and December 31, 2012, and were followed up for at least 5 years (median, 12.7 years).

Results

Among both diagnostic patients and those with known CAD, there was a marked temporal decline in typical angina and myocardial ischemia. However, several risk factors for disease progressively increased, including diabetes, obesity, and hypertension. In addition, the need to perform pharmacological testing in lieu of exercise increased markedly between the first and fourth epochs among both diagnostic patients (from 26.5% [1634 of 6176] to 53.0% [5781 of 10,908]; P<.001) and patients with known CAD (from 31.1% [999 of 3213] to 75.5% [1405 of 1860]; P<.001). The net effect of these competing positive and negative risk factor trends was no change in the adjusted annualized rate of mortality over the temporal span in our study, ranging from 1.57% per year in 1991-1995 to 1.76% per year in 2006-2012 among diagnostic patients and from 2.46% per year to 2.75% per year during the same intervals among patients with known CAD.

Conclusion

Our findings suggest a marked contemporary shift in the drivers of all-cause mortality among patients undergoing cardiac stress tests away from such factors as typical angina and inducible myocardial ischemia, which are declining in prevalence, and toward such factors as diabetes and an inability to perform exercise, which are increasing in prevalence.

Association between coronary atherosclerotic burden and all-cause mortality among patients undergoing exercise versus pharmacologic stress-rest SPECT myocardial perfusion imaging

BACKGROUND AND AIMS

Patients with suspected coronary artery disease who undergo stress SPECT myocardial perfusion imaging (MPI) and require pharmacologic stress are at substantially increased mortality risk compared to those who can exercise. However, the mechanisms underlying this increased risk are not well delineated. To test whether increased atherosclerotic burden accounts for this increased risk, we assessed the association between coronary artery calcium (CAC) scores and mortality risk among patients undergoing exercise versus pharmacologic SPECT MPI.

METHODS

We assessed all-cause mortality in 2,151 patients, followed for 12.2 ± 3.4 years, after undergoing stress-rest SPECT-MPI and CAC scanning within 3 months of each other. Patients were divided according to their mode of stress testing (exercise or pharmacologic). We further employed propensity analysis to create a subgroup of exercise and pharmacologic subgroups with comparable age, symptoms, and coronary risk factors.

RESULTS

Despite greater age and worse clinical profiles, pharmacologic and exercise patients had similar CAC scores. However, the hazard ratio (95% CI) for mortality was substantially greater among pharmacologic patients: 2.39 (1.83-3.10). For each level of CAC abnormality, pharmacologic patients had >2-fold increased risk adjusted hazard ratio for all-mortality risk (p < 0.05 for each CAC level). Among propensity-matched exercise versus pharmacologic patients, the same findings were observed.

CONCLUSIONS

Among patients referred for stress-rest SPECT-MPI and CAC scoring, pharmacologic patients have substantially increased mortality risk compared to exercise patients, despite having comparable levels of coronary atherosclerosis.

Differential Impact of Appropriate Use Criteria on the Association between Age and an Abnormal Stress Myocardial Perfusion SPECT

Background

The diagnostic and prognostic value of appropriate use criteria (AUC) for coronary artery disease (CAD) is well established. Whether the diagnostic yield of AUC for predicting CAD is preserved among the elderly is not known.

Methods

We analyzed a multi-site prospective cohort of 1511 consecutive patients (mean age 59 ±13 years, 57% males) who underwent outpatient, community-based SPECT myocardial perfusion imaging (MPI). Appropriateness of the studies was determined based on the 2013 multimodality AUC for detection and risk assessment of stable ischemic heart disease. An abnormal SPECT MPI was defined by either a summed stress score ≥ 4 or a summed difference score ≥ 2.

Results

Abnormal SPECT MPI was present in 190 patients (12.5%), while ischemia on MPI alone was present in 122 (8%). In multivariate logistic regression analysis, age ≥ 60 years, male gender, hypertension, diabetes mellitus, and known CAD were independent predictors of an abnormal SPET MPI, while appropriate indication of testing was not. Age ≥ 60 years was also an independent predictor of inducible myocardial ischemia, while appropriate indication for testing was not. Among elderly (≥ 60 year), regardless of appropriateness of testing, there was no difference in the prevalence of an abnormal SPECT (19% vs. 14%, p=0.14) or prevalence of SPECT ischemia (11% vs. 11%, p=1.00). Among younger patients however, appropriate testing predicted a greater prevalence of an abnormal SPECT (12% vs. 7%, p=0.013).

Conclusion

In this multi-site cohort, testing based on AUC did not discriminate the risk of an abnormal SPECT MPI among the elderly. Caution is advised when relying on AUC for referring elderly patients for SPECT MPI.

Stress Echocardiography Positivity Predicts Cancer Death

BACKGROUND

Stress echocardiography (SE) predicts cardiac death, but an increasing share of cardiac patients eventually die of cancer. The aim of the study was to assess whether SE positivity predicts cancer death.

METHODS AND RESULTS

In a retrospective analysis of prospectively acquired single-center, observational data, we evaluated 4673 consecutive patients who underwent SE from 1983 to 2009. All patients were cancer-free at index SE and were followed up for a median of 131 months (interquartile range 134). We separately analyzed predetermined end points: cardiovascular, cancer, and noncardiovascular, noncancer death, with and without competing risk. SE was positive in 1757 and negative in 2916 patients; 869 cardiovascular, 418 cancer, and 625 noncardiovascular, noncancer deaths were registered. The 25-year mortality was higher in SE-positive than in SE-negative patients, considering cardiovascular (40% versus 31%; P<0.001) and cancer mortality (26% versus 17%; P<0.01). SE positivity was a strong predictor of cancer (cause-specific hazard ratio 1.19; 95% confidence interval, 1.16-1.73; P=0.05) and cardiovascular mortality (1.18; 95% confidence interval, 1.03-1.35; P=0.02). Fine-Gray analysis to account for competing risk gave similar results. Cancer risk diverged after 15 years, whereas differences were already significant at 5 years for cardiovascular risk.

CONCLUSIONS

SE results predict cardiovascular and cancer mortality. SE may act as a proxy of the shared risk factor milieu for cancer or cardiovascular death.

Review of cardiovascular imaging in the journal of nuclear cardiology in 2016: Part 2 of 2-myocardial perfusion imaging

In 2016, the Journal of Nuclear Cardiology published many high-quality articles. Similar to previous years, we will summarize here a selection of the articles that were published in the Journal in 2016 to provide a concise review of the main advancements that have recently occurred in the field. In the first article of this two-part series we focused on publications dealing with positron emission tomography, computed tomography, and magnetic resonance. This review will place emphasis on myocardial perfusion imaging using single-photon emission-computed tomography summarizing advances in the field including in diagnosis, prognosis, and appropriate use.

Non-invasive imaging in cardiology for the generalist

In contrast to invasive techniques, the goal of non-invasive cardiac imaging is to identify or exclude heart disease in response to a patient's clinical history of cardiac localizing symptoms. Imaging also aims to establish the risk of an individual developing future heart disease with a view to preventing major cardiovascular events such as myocardial infarction. As well as a role in risk stratification, non-invasive cardiac imaging also helps with decision making for future medical and procedural interventions. This review outlines the non-invasive imaging modalities available to physicians to identify and risk stratify cardiovascular disease. It discusses the strengths of each imaging technique, in which circumstances it is most useful and its diagnostic accuracy.

Comparison of the current reasons for undergoing pharmacologic stress during echocardiographic and radionuclide stress testing

BACKGROUND

Symptom-limited exercise is the preferred method of cardiac stress testing, but pharmacologic testing has been increasing over time. The exact reasons for pharmacologic stress testing have not been rigorously categorized. Thus, we systematically explored the reasons for pharmacologic stress testing in patients referred for cardiac stress imaging.

METHODS

We studied consecutive patients referred for stress imaging [stress echocardiography or radionuclide myocardial perfusion imaging (MPI)] at Mount Sinai St Luke's hospital between August 2013 and April 2014. Baseline information was obtained using a standardized questionnaire and a trained physician triaged the patient for symptom-limited exercise stress testing or pharmacologic stress testing.

RESULTS

In total, 551(48%) of our entire stress cohort underwent cardiac imaging following initial exercise testing and 589 (52%) underwent imaging with initial pharmacologic stress testing. Deconditioning and inability to walk (primarily due to musculoskeletal conditions) constituted the top two reasons for performing pharmacologic stress, followed by frailty, left bundle branch block (for MPI), resting wall motion abnormality (for echocardiography), and failed exercise attempts. The reasons for performing pharmacologic stress testing were similar in the MPI and echocardiography patients, despite a much higher level of disease acuity in the MPI group.

CONCLUSIONS

We have applied a systematic approach for categorizing the reasons for pharmacologic stress. These reasons are heterogeneous, but similar across MPI and echo stress laboratories.

Stress SPECT Myocardial Perfusion Imaging in End-Stage Renal Disease

PURPOSE OF REVIEW

Patients with end-stage renal disease (ESRD) have an increased risk of cardiovascular morbidity and mortality. Cardiac risk assessment, though challenging, is critical in these high-risk patients, particularly in the pre-transplant population. In this review, we discuss the burden of coronary artery disease in the ESRD population and review the literature on the diagnostic and prognostic performance, clinical value, and future directions of single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) in ESRD patients.

RECENT FINDINGS

Stress myocardial perfusion imaging provides incremental prognostic value to clinical data. The AHA/ACCF consensus statement on the cardiac assessment of kidney transplant candidates provides some guidance on the selection of asymptomatic patients for further non-invasive risk stratification. Additionally, the novel selective A_2A receptor agonist vasodilator stress agent, regadenoson, is safe and effective in ESRD and has recently been approved by the Food and Drug Administration for use in this population. Ancillary stress MPI findings, namely heart rate response to vasodilator stress, can provide incremental risk stratification.

SUMMARY

While myocardial perfusion imaging is widely used as a risk assessment tool, its utilization and clinical implications in the ESRD population are controversial. Though stress SPECT-MPI has imperfect diagnostic accuracy in this specific patient population, it is still a valuable non-invasive modality in cardiovascular risk assessment.

The prognostic value of regadenoson SPECT myocardial perfusion imaging in patients with end-stage renal disease

BACKGROUND

The prognostic value of regadenoson SPECT myocardial perfusion imaging (MPI) has not been specifically studied in patients with end-stage renal disease (ESRD).

METHODS AND RESULTS

We prospectively followed ESRD patients enrolled in the ASSUAGE and ASSUAGE-CKD trials in which they received regadenoson-stress 99mTc-tetrofosmin SPECT-MPI. Images were semiquantitatively analyzed by an investigator blinded to clinical and outcome data. Patients were followed for cardiac death, myocardial infarction (MI), and coronary revascularization (CR). Revascularizations occurring >90 days post-MPI were considered "late" events. Survival analysis was performed using Cox regression models, adjusting for age, gender, diabetes, dyslipidemia, smoking, and known coronary artery disease. We analyzed 303 patients (mean age 54 years; 64% men), who were followed for 35 ± 10 months. Adjusting for clinical covariates, abnormal regadenoson-stress MPI (SSS ≥ 4) was associated with increased risk of the composite of cardiac death or MI (23.9% vs 14.4%; HR 1.88; CI 1.04-3.41; P = .037) and the composite of cardiac death, MI, or late CR (27.3% vs 16.7%; HR 1.80; CI 1.03-3.14; P = .039). Adjusting for clinical covariates, regadenoson-induced myocardial ischemia (SDS ≥ 2) was associated with increased rate of the composite endpoint of cardiac death, MI, or CR (33.3% vs 16.9%; HR 1.97; CI 1.19-3.27; P = .008).

CONCLUSION

Regadenoson-stress SPECT-MPI provides a significant prognostic value in patients with ESRD. ESRD patients with normal SPECT-MPI have relatively high adverse event rates.

The role of pharmacological stress testing in women

Pharmacological stress is an alternative method to dynamic exercise that combined with noninvasive imaging allows the detection of flow-limiting coronary artery disease (CAD). It represents the stress procedure of choice in patients who cannot exercise appropriately. In women, pharmacological stress combined with myocardial perfusion scintigraphy (MPS) has demonstrated to be highly accurate for the detection of obstructive CAD and a valuable tool that helps separate patients at low cardiac risk from those with an adverse prognosis. Pharmacological stress with positron emission tomographic (PET) imaging is increasingly used in the investigation of suspected obstructive CAD; available evidence shows that the diagnostic profile and prognostic value of stress PET imaging is similar to that of stress MPS in women.

Non-invasive assessment of low- and intermediate-risk patients with chest pain

Coronary artery disease (CAD) remains a significant global public health burden despite advancements in prevention and therapeutic strategies. Common non-invasive imaging modalities, anatomic and functional, are available for the assessment of patients with stable chest pain. Exercise electrocardiography is a long-standing method for evaluation for CAD and remains the initial test for the majority of patients who can exercise adequately with a baseline interpretable electrocardiogram. The addition of cardiac imaging to exercise testing provides incremental benefit for accurate diagnosis for CAD and is particularly useful in patients who are unable to exercise adequately and/or have uninterpretable electrocardiograms. Radionuclide myocardial perfusion imaging and echocardiography with exercise or pharmacological stress provide high sensitivity and specificity in the detection and further risk stratification of patients with CAD. Recently, coronary computed tomography angiography has demonstrated its growing role to rule out significant CAD given its high negative predictive value. Although less available, stress cardiac magnetic resonance provides a comprehensive assessment of cardiac structure and function and provides a high diagnostic accuracy in the detection of CAD. The utilization of non-invasive testing is complex due to various advantages and limitations, particularly in the assessment of low- and intermediate-risk patients with chest pain, where no single study is suitable for all patients. This review will describe currently available non-invasive modalities, along with current evidence-based guidelines and appropriate use criteria in the assessment of low- and intermediate-risk patients with suspected, stable CAD.

Appropriate use criteria for SPECT myocardial perfusion imaging: Are they appropriate for women?

BACKGROUND

Several studies have reported that women are more likely to receive inappropriate SPECT myocardial perfusion imaging (MPI), suggesting gender disparity in AUC determination. We investigated the impact of gender on the diagnostic and prognostic utility of AUC.

METHODS AND RESULTS

We analyzed a multi-site prospective cohort of 1511 consecutive patients (43.5% women) who underwent outpatient, community-based SPECT-MPI. Subjects were stratified into gender groups and appropriateness subgroups, and followed for 27 ± 10 months for cardiac death, myocardial infarction, and coronary revascularization. Women were more likely to receive inappropriate MPI (60.7% vs 33.8%, P < .001). Irrespective of appropriateness, women were less likely to have an abnormal MPI (6.1% vs 14.9%, P < .001), even after adjusting for clinical covariates [odds ratio = 0.40 (95% confidence interval = 0.26-0.60), P < .001]. Irrespective of appropriateness, women were at lower risk for MACE (composite of cardiac death, myocardial infarction, or coronary revascularization) after adjusting for clinical and imaging covariates [hazard ratio = 0.49 (95% confidence interval = 0.28-0.86), P = .01]. There was no interaction between gender and appropriateness group as a determinant of abnormal MPI or MACE (interaction P values ≥ .26), indicating that female gender was associated with similar relative risk of an abnormal MPI and MACE irrespective of appropriateness group. Abnormal MPI was similarly predictive of increased hazard of MACE in both genders, regardless of appropriateness (interaction P values ≥ .46).

CONCLUSION

In this multi-site cohort, there was no demonstrable gender-based differential impact of AUC on the diagnostic or prognostic utility of SPECT-MPI. The study validates the methods used in determining risk in the AUC algorithm and endorses the widespread application of AUC in men and women.

Long-Term Risk Assessment After the Performance of Stress Myocardial Perfusion Imaging

Stress-rest myocardial perfusion imaging (MPI) is a potent method for assessing the presence and magnitude of inducible myocardial ischemia. Stress MPI currently faces increased scrutiny for its therapeutic effectiveness because of the emergence of other competing means for assessing clinical risk. New data have examined the usefulness stress-rest-MPI as a predictor for long-term clinical outcomes, in contrast to its traditional role for assessing short-term cardiovascular risk. These data indicates that temporal risk is highly influenced by both the magnitude of ischemia and various baseline clinical factors. An optimized assessment of stress MPI, which includes long-term risk prediction, might improve the potential future clinical effectiveness of this imaging modality.