Pharmacologic Stress Myocardial Perfusion Imaging Research Articles

Relationship between heart rate response and cardiac innervation in patients with suspected or known coronary artery disease

BackgroundChronotropic response to pharmacological stress test is blunted in patients with autonomic neuropathy. The relationship between heart rate (HR) changes during pharmacological stress test and cardiac autonomic dysfunction has not been fully investigated. We assessed the potential interplay between HR response (HRR) and myocardial innervation in patients with suspected or known coronary artery disease (CAD). Methods and ResultsWe studied 71 patients with suspected or known CAD referred to pharmacological stress myocardial perfusion imaging and 123I metaiodobenzylguanidine (123I-MIBG) cardiac scintigraphy. HRR was calculated as the maximum percent change from baseline according to the formula: (peak HR − rest HR)/rest HR × 100. 123I-MIBG heart-to-mediastinum (H/M) ratio was calculated and a late H/M ratio < 1.6 was considered abnormal. HRR progressively decreased with decreasing late H/M ratio (P for trend = 0.02) and a significant correlation between HRR and late H/M ratio (P = 0.03) was observed. The addition of HRR to a model including age, diabetes, known CAD, left ventricular ejection fraction, and stress-induced ischemia added incremental value in predicting an abnormal late H/M ratio, increasing the global chi-square from 8.09 to 13.8 (P = 0.02). ConclusionsThe relationship between HRR and cardiac sympathetic innervation in patients with suspected or known CAD confirms a strong interplay between cardiac response to stress tests and cardiac autonomic activation. This finding suggests that HRR may be used as a surrogate for assessing cardiac sympathetic function.

Selective Adenosine A2A Agonists May Change Myocardial Perfusion Imaging.

In recent years, the requirement for pharmacological stress myocardial perfusion imaging (SPECT) has increased, and adenosine stress testing is now the mainstream. Selective adenosine A2A receptor agonists will be applied clinically in the future. By selectively activating only A2A receptors, it can reduce complications such as bronchospasm, hypotension, and bradycardia, which have been problems with adenosine stress tests. In addition, since this drug can be administered in bolus injection, it has the advantage of being able to perform the test at one root.

Reducing radiation dose from myocardial perfusion imaging in subjects with complex congenital heart disease

IntroductionThe prevalence of defects and effective radiation dose from various myocardial perfusion imaging (MPI) strategies in congenital heart disease (CHD) is unknown. MethodsWe studied 75 subjects with complex CHD (ages 5 to 80 years) referred for MPI between 2002 and 2015. A rest and exercise or pharmacologic stress MPI was performed using 99mTechnetium sestamibi, 82rubidium or 13N-ammonia, and Sodium iodide SPECT (single-photon emission computed tomography), SPECT/CT or Cadmium zinc telluride (CZT) SPECT or PET (positron emission tomography)/CT scanners. Deidentified images were interpreted semi-quantitatively in three batches: stress only MPI, stress/rest MPI, and stress/rest MPI with taking into account a history of ventricular septal defect repair. Effective radiation dose was estimated for stress/rest MPI and predicted for 1-day stress-first (normal stress scans), and for 2-day stress/rest MPI (abnormal stress scans). ResultsThe median age was 18.6 years. The most common type of CHD was transposition of the great arteries (63%). Rest/stress MPI was abnormal in 43% of subjects and 25% of the abnormal scans demonstrated reversible defects. Of the subjects with abnormal MPI, 33% had significant underlying anatomic coronary artery obstruction. Estimated mean effective radiation dose ranged from 2.1 ± 0.6 mSv for 13N-ammonia PET/CT to 12.5 ± 0.9 mSv for SPECT/CT. Predicted effective radiation dose was significantly lower for stress-first MPI and for 2-day stress/rest protocols. ConclusionsDue to the relatively high prevalence of abnormal stress MPI, tailored protocols with a stress-first MPI as well as the use of 2-day protocols and advanced imaging technologies including CZT SPECT, novel image reconstruction software, and PET MPI could substantially reduce radiation dose in complex CHD.

Significance of New, Isolated T-wave Inversion in Multiple Electrocardiogram Leads with Regadenoson Injection in Patients with Normal Myocardial Perfusion Imaging

The pharmacologic (regadenoson) stress myocardial perfusion imaging (MPI) is used widely in patients who cannot exercise for detecting coronary artery disease (CAD). The interpretation of these studies depends primarily on the imaging results because the sensitivity of electrocardiograms (ECG) in this setting is poor. Prior study showed that effects of regadenoson on ST-segment occurred infrequently and had low sensitivity for detecting CAD. The significance of T-wave inversion in multiple ECG leads without ST-segment depression with regadenoson injection in patients with normal MPI is described and reported. ECGs were reviewed retrospectively in 64 patients who had regadenoson MPI and coronary angiography for evaluation of CAD from June 1, 2016 to August 31, 2018. Five cases were identified with new, isolated T-wave inversion in multiple ECG leads. All five cases had new and isolated T-wave inversion in multiple leads without ST segment depression with regadenoson injection and normal MPI. At coronary angiography, three of the five cases showed obstructive coronary artery disease who received coronary percutaneous intervention. One case had nonobstructive coronary artery disease and one had a normal coronary artery. Despite nonspecific ST-T changes on baseline ECGs and normal MPI in all patients, three of five cases had obstructive CAD by coronary angiography. New, isolated T-wave inversion in multiple ECG leads with regadenoson injection were observed in our patients with normal MPI. These ECG findings may be associated with false negative MPI. Therefore, careful observation and scrutiny of all ECG changes, especially new, isolated T-wave inversion in multiple ECG leads during regadenoson MPI is advisable to identify potential obstructive CAD despite normal MPI findings.

Randomized Comparison of Clinical Effectiveness of Pharmacologic SPECT and PET MPI in Symptomatic CAD Patients

ObjectivesThis study compared the clinical effectiveness of pharmacologic stress myocardial perfusion imaging (MPI) plus positron emission tomography (PET) with single-photon emission computed tomography (SPECT) in patients with known coronary artery disease (CAD) presenting with symptoms suggestive of ischemia. BackgroundAlthough PET MPI has been shown to have higher diagnostic accuracy in detecting hemodynamically significant CAD than SPECT MPI, whether this impacts downstream management has not been formally evaluated in randomized trials. MethodsThis study consisted of a single-center trial in which patients with known CAD and suspected ischemia were randomized to undergo PET or attenuation-corrected SPECT MPI between June 2009 and September 2013. Post-test management was at the discretion of the referring physician, and patients were followed for 12 months. The primary endpoint was diagnostic failure, defined as unnecessary angiography (absence of ≥50% stenosis in ≥1 vessel) or additional noninvasive testing within 60 days of the MPI. Secondary endpoints were post-test escalation of antianginal therapy, referral for angiography, coronary revascularization, and health status at 3, 6, and 12 months. ResultsA total of 322 patients with an evaluable MPI were randomized (n = 161 in each group). At baseline, 88.8% of patients were receiving aspirin therapy, 76.7% were taking beta-blockers, and 77.3% were taking statin therapy. Diagnostic failure within 60 days occurred in only 7 patients (2.2%) (3 [1.9%] in the PET group and 4 [2.5%] in the SPECT group; p = 0.70). There were no significant differences between the 2 groups in subsequent rates of coronary angiography, coronary revascularization, or health status at 3, 6, and 12 months of follow-up (all p values ≥0.20); however, when subjects were stratified by findings on MPI in a post hoc analysis, those with high-risk MPI on PET testing had higher rates of angiography and revascularization on follow-up than those who had SPECT MPI, whereas those undergoing low-risk PET studies had lower rates of both procedures than those undergoing SPECT (interaction between randomized modality ∗high-risk MPI for 12-month catheterization [p = 0.001] and 12-month revascularization [p = 0.09]). ConclusionsIn this contemporary cohort of symptomatic CAD patients who were optimally medically managed, there were no discernible differences in rates of diagnostic failure at 60 days, subsequent coronary angiography, revascularization, or patient health status at 1 year between patients evaluated by pharmacologic PET compared with those evaluated by SPECT MPI. Downstream invasive testing rates with PET MPI were more consistent with high-risk features than those with SPECT MPI. (Effectiveness Study of Single Photon Emission Computed Tomography [SPECT] Versus Positron Emission Tomography [PET] Myocardial Perfusion Imaging; NCT00976053)

Abstract 119: Quality of Life Outcomes in Patients With Known Coronary Artery Disease Presenting With Suspected Ischemia Randomized to Pharmacologic Stress Myocardial Perfusion Imaging With Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET)

Introduction: In patients with suspected ischemia, myocardial perfusion imaging (MPI) with PET has been shown to provide greater diagnostic accuracy and improved risk stratification over SPECT MPI. As such, PET MPI could lead to improved post-test management, which could impact subsequent patient health status (symptoms, function and quality of life). We compared the health status outcomes for patients undergoing stress MPI for suspected ischemia using PET vs SPECT. Methods: At a single health system, patients with CAD and suspected ischemia were randomized to PET or SPECT MPI from 6/2009-9/2013. Post-test management was at the discretion of the referring physician. The Seattle Angina Questionnaire (SAQ) was prospectively collected at baseline, 1, 3, 6 and 12 months, and the Angina Frequency (AF), Physical Limitations (PL), and Quality of Life (QL) domain scores were compared between MPI modalities using linear repeated measures model. Results: Among 322 patients with CAD randomized to PET vs. SPECT (n=161 in each group, mean age 66.3 ± 9.7 years, 64.9% men, 27.6% with diabetes, 14.0% with ischemia (≥10% myocardium)), all SAQ domains increased significantly from baseline with the largest changes observed within the first 1 month after MPI (Figure). However, the changes in SAQ domain scores were similar between the imaging modalities (SAQ AF: p=0.70, SAQ PL: p=0.07, SAQ QL: p=0.20). Conclusions: In symptomatic patients with CAD undergoing stress MPI, health status improved significantly over a year of follow-up. Although PET MPI more accurately details the ischemia, use of this imaging modality did not translate into improved health status over time.

Can Stress-induced Phase Change be Observed on 99mTc Pharmacological Stress Myocardial Perfusion Imaging?

Can Stress-induced Phase Change be Observed on ^99mTc Pharmacological Stress Myocardial Perfusion Imaging?

Estimation of myocardial flow reserve utilizing an ultrafast cardiac SPECT: Comparison with coronary angiography, fractional flow reserve, and the SYNTAX score

BackgroundQuantitative assessment of myocardial flow reserve (MFR) by single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) is challenging but may facilitate evaluation of multi-vessel coronary artery disease (CAD). MethodsWe enrolled 153 patients with suspected or known CAD, referred for pharmacological stress MPI. They underwent a 99mTc-perfusion stress/rest SPECT with an ultrafast cadmium-zinc-telluride (CZT) camera. Dynamic data were acquired and time-activity curves fitted to a 1-tissue compartment analysis with input function. K1 was assigned for stress and rest data. The MFR index (MFRi) was calculated as K1 stress/K1 at-rest. The findings were validated by invasive coronary angiography in 69 consecutive patients. ResultsThe global MFRi was 1.46 (1.16–1.76), 1.33 (1.12–1.54), and 1.18 (1.01–1.35), for 1-vessel disease (VD), 2-VD, and 3-VD, respectively. In the 3-VD, global MFRi was lower than that in 0-VD (1.63 [1.22–2.04], P<0.0001) and 1-VD (P=0.003). Multivariate logistic regression analysis for 3-VD showed significant associations with smoking history (odds ratio [OR]: 4.4 [0.4–8.4]), left ventricular ejection fraction (OR: 61.6 [57.5–66.0]), and global MFRi (OR: 119.6 [111.5–127.7], P=0.002). A cut-off value of 1.3 yielded 93.3% sensitivity and 75.9% specificity for diagnosing 3-VD. Fractional flow reserve positively correlated with regional MFRi (r=0.62, P=0.008), and the SYNTAX score correlated negatively with global MFRi (r=0.567, P=0.0003). ConclusionWe developed and validated a clinically available method for MFR quantification by dynamic 99mTc-perfusion SPECT utilizing a CZT camera, which improves the detectability of multi-vessel CAD.

10 Real-world evidence of the safety of pharmacologic stress in myocardial perfusion imaging

Introduction Myocardial perfusion imaging (MPI) is increasingly used as recommended by NICE for patients with a 30–60% estimated likelihood of coronary artery disease. We aimed to investigate the safety of drugs used in patients undergoing pharmacologic stress MPI. Methods A 9-month (May 2015–Feb 2016) retrospective study to investigate the incidence of adverse effects (AE) in patients undergoing pharmacologic stress MPI. We employ standardised protocols (Tc-99m) using 4 agents: dipyridamole, regadenoson, adenosine and dobutamine. Clinical data including AEs were collected from cardiobase. Descriptive analysis and frequencies were calculated. AE in MPI were compared to those occurring in 50 patients who underwent conventional exercise tolerance testing (ETT) using chi-squared test. Findings Of the 360 patients (mean age 67 years [SD 11]; 196 men, 164 women), who had pharmacologic stress agent administered, 166 (46%) became symptomatic: dyspnoea (24.7%), chest discomfort (12.8%), flushing (10%), chest pain (3.6%), cough (3.3%), nausea (2.8%), pain elsewhere (2.5%), dizziness (2.5%), vasovagal reaction (2.2%), wheeze (1.9%), headache (1.9%), vomiting (0.8%), abdominal discomfort (0.8%). The commonest symptom was chest discomfort for dobutamine but dyspnoea for all the other agents. Adenosine had the highest incidence of AE (76%). No significant complications were recorded that required hospital admission. When compared with ETT there was no significant difference of adverse effects (MPI 166/360 [44%], ETT 29/50 [58%]; p=0.12). Conclusions This real-world data show that pharmacologic stress MPI is safe when clinical protocols are followed. Technician (physicist)-led testing could be an alternative in busy cardiac units where medical staffing are not always available.

Regadenoson-induced coronary vasospasm resulting in severe reversible perfusion defects and transient ischemic dilation on SPECT stress myocardial perfusion imaging

A 58-year-old woman with hypertension and diabetes presented to the emergency department with exertional right-sided chest pain. Her cardiac biomarkers were negative and her electrocardiogram demonstrated no significant abnormalities. She subsequently underwent pharmacologic stress myocardial perfusion imaging using regadenoson. Her electrocardiogram demonstrated no significant ischemic changes and she only complained of dyspnea following regadenoson infusion. Perfusion images were acquired using the GE millennium MC scanner and processed using Xpress3 cardiac wide beam reconstruction software (UltraSPECT, Ltd.) at an xeleris functional imaging workstation. Review of the rotating raw data revealed breast attenuation artifact but no significant patient motion. Her perfusion imaging revealed a severe defect in the mid-to-distal inferolateral wall that was mostly reversible suggestive of significant ischemia. In addition, there was pronounced dilation of the left ventricle with stress (Figure 1). The patient underwent cardiac catheterization which demonstrated no obstructive coronary artery disease (Figures 2, 3). Upon further analysis of the patient’s history, she had apparently been diagnosed with Prinzmetal angina in the past and had undergone cardiac catheterization eight years prior for similar symptoms and this was normal as well. She was subsequently discharged on appropriate pharmacotherapy and was asymptomatic. Multiple reports have demonstrated coronary vasospasm after use of adenosine for stress testing. However, there is a limited data available in reference to regadenoson, which is a selective A2A adenosine receptor agonist. Recent emerging data demonstrate, however, that regadenoson may also lead to vasospasm as it has similar pharmacologic properties. Our case illustrates severely abnormal myocardial perfusion imaging with reversible regional ischemia and transient ischemic dilation with no obstructive coronary artery disease likely due to regadenoson-induced coronary vasospasm. Therefore, vasospastic heart disease is a potential confounding factor to consider in the interpretation of regadenoson stress MPI and may be clinically relevant in the management of patients with conflicting anatomic and perfusion findings.

Coronary artery disease screening and prognosis in incident dialysis patients

Guidelines have recommended that physicians screen for coronary artery disease (CAD) at the initiation of dialysis. The purpose of this study was to examine the effects of CAD screening at the initiation of dialysis on prognosis after starting dialysis This retrospective cohort study involved 224 consecutive incident dialysis patients without advanced cardiac disease. Pharmacological stress myocardial perfusion imaging (MPI) was performed to routinely screen incident dialysis patients within 3 months of starting dialysis therapy. The influence of MPI on prognosis after starting dialysis was explored by the propensity score adjustment method. The study outcome was defined as all-cause mortality and cardiac death. Of the 224 patients, 164 (73.2 %) underwent MPI screening at initiation of dialysis. During the median follow-up period of 5.5 years, 77 patients died, among whom 17 (22.1 %) cardiac deaths were observed. The patients who received MPI had a significantly higher survival rate for all-cause mortality and cardiac death compared with the patients without MPI (log-rank test, p < 0.001, p = 0.021, respectively). In multiple Cox regression analysis, MPI screening continued to have a statistically significant negative association with all-cause mortality after adjusting for confounding variables (hazard ratio 0.581, p = 0.034) and propensity score (hazard ratio 0.568, p = 0.025). MPI CAD screening at dialysis initiation could improve prognosis after starting dialysis.

Cardiovascular outcomes after pharmacologic stress myocardial perfusion imaging

While pharmacologic stress single photon emission computed tomography myocardial perfusion imaging (SPECT-MPI) is used for noninvasive evaluation of patients who are unable to perform treadmill exercise, its impact on net reclassification improvement (NRI) of prognosis is unknown. We evaluated the prognostic value of pharmacologic stress MPI for prediction of cardiovascular death or non-fatal myocardial infarction (MI) within 1 year at a single-center, university-based laboratory. We examined continuous and categorical NRI of pharmacologic SPECT-MPI for prediction of outcomes beyond clinical factors alone. Six thousand two hundred forty patients (median age 66 years [IQR 56-74], 3466 men) were studied and followed for 5963 person-years. SPECT-MPI variables associated with increased risk of cardiovascular death or non-fatal MI included summed stress score, stress ST-shift, and post-stress resting left ventricular ejection fraction ≤50%. Compared to a clinical model which included age, sex, cardiovascular disease, risk factors, and medications, model χ(2) (210.5 vs. 281.9, P < .001) and c-statistic (0.74 vs. 0.78, P < .001) were significantly increased by addition of SPECT-MPI predictors (summed stress score, stress ST-shift and stress resting left ventricular ejection fraction). SPECT-MPI predictors increased continuous NRI by 49.4% (P < .001), reclassifying 66.5% of patients as lower risk and 32.8% as higher risk of cardiovascular death or non-fatal MI. Addition of MPI predictors to clinical factors using risk categories, defined as <1%, 1% to 3%, and >3% annualized risk of cardiovascular death or non-fatal MI, yielded a 15.0% improvement in NRI (95% CI 7.6%-27.6%, P < .001). Pharmacologic stress MPI substantially improved net reclassification of cardiovascular death or MI risk beyond that afforded by clinical factors.

GW26-e2979 Side Effects of Adenosine Triphosphate Stress in Pharmacological Stress Myocardial Perfusion Imaging

GW26-e2979 Side Effects of Adenosine Triphosphate Stress in Pharmacological Stress Myocardial Perfusion Imaging

Cardiovascular risk stratification in diabetic patients following stress single-photon emission-computed tomography myocardial perfusion imaging: The impact of achieved exercise level

BackgroundPrevious studies have demonstrated that diabetic patients undergoing exercise stress single-photon emission-computed tomography (SPECT) myocardial perfusion imaging (MPI) have significantly lower cardiac events when compared to the diabetic patients undergoing pharmacologic stress SPECT MPI across all perfusion categories. However, there are limited data on the level of exercise achieved during exercise SPECT MPI among diabetic patients and its impact on cardiovascular outcomes. MethodsWe retrospectively analyzed 14,849 consecutive patients (3,654 diabetics and 11,195 non-diabetics) undergoing exercise stress, combined exercise and pharmacologic stress, and pharmacologic stress SPECT MPI from 1996 to 2005 at a single tertiary care center. Diabetic and non-diabetic patients were categorized into 3 groups based on the metabolic equivalents (METs) achieved: ≥5 METs, <5 METs, and pharmacologic stress groups. All studies were interpreted using the 17-segment ASNC model. The presence, extent, severity of perfusion defects were calculated using the summed stress score (SSS), and patients were classified into normal (SSS < 4), mildly abnormal (SSS 4-8), and moderate-severely abnormal (SSS > 8) categories. Annualized event rates (AER) for the composite end point of non-fatal myocardial infarction and cardiac death were calculated over a mean follow-up period of 2.4 ± 1.4 years with a maximum of 6 years. ResultsIn moderate-severe perfusion abnormality (SSS > 8) category, diabetic patients who were able to achieve ≥5 METs had significantly lower AER compared to diabetic patients who were unable to achieve ≥5 METs (3% vs 5.5%, P = .04), and non-diabetic patients unable to achieve ≥5 METs (3% vs 4.8%, P < .001). Diabetic patients who achieved a high workload of ≥10 METs had a very low AER of 0.9%. Diabetic patients, who attempted exercise but were unable to achieve ≥5 METs, still had significantly lower AER than diabetics undergoing pharmacologic stress MPI across all perfusion categories [1.5% vs 3.2%, P = .006 (SSS < 4); 2.5% vs 4.9%, P = .032 (SSS 4-8); 5.5% vs 10.3%, P = .003 (SSS > 8)]. After adjustment for cardiovascular risk factors, the percentage decrease in cardiac event rate for every 1-MET increment in exercise capacity was 10% in the overall cohort, 12% in diabetic group, and 8% in non-diabetic group. ConclusionsDespite significant perfusion defects, diabetic patients who achieve ≥5 METs during stress SPECT MPI have significantly reduced risk for future cardiac events. Diabetic patients who achieve ≥10 METs have a very low annualized event rate. These findings support that exercise capacity obtained during SPECT MPI is a surrogate for outcomes among diabetic patients undergoing nuclear stress testing.

Regadenoson use in patients with chronic obstructive pulmonary disease: the state of current knowledge

Stress testing is challenging in patients with chronic obstructive pulmonary disease (COPD). Functional capacity is generally decreased in this patient population, limiting patients’ ability to achieve physiologic stress through exercise. Additionally, due to emphysematous changes, COPD patients tend to have poor acoustic windows that impair the quality and therefore diagnostic accuracy of stress echocardiography techniques. Pharmacologic stress myocardial perfusion imaging (MPI) testing is also problematic, particularly due to the concern for adenosine-induced bronchoconstriction with conventional vasodilator stress agents. Regadenoson, a selective A2A adenosine receptor agonist, has gained popularity due to its ease of administration and improved patient experience in the general population. The literature describing the experience with regadenoson in COPD patients, though limited, is rapidly growing and reassuring. This review summarizes the pharmacology and clinical application of this novel stress agent and presents the available data on the safety and tolerability of its use in COPD patients.

Risk stratification among diabetic patients undergoing stress myocardial perfusion imaging

BackgroundPrevious studies have suggested that diabetic patients undergoing single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) are at greater risk for cardiac events than non-diabetic patients with both normal and abnormal imaging results. However, the impact of stress modality on outcomes in this patient group has not been examined. MethodsThe data on all patients undergoing exercise stress or vasodilator stress SPECT MPI from 1996 to 2005 were reviewed. After excluding patients based on our predefined criteria, we subcategorized the study population into diabetic patients and non-diabetic patients. Among the diabetic patients, we identified patients with known coronary artery disease (CAD) and no known CAD. All studies were interpreted using the 17-segment ASNC model. The presence, extent, and severity of perfusion defects were calculated using the summed stress score (SSS), and patients were classified into normal (SSS < 4), mildly abnormal (SSS 4-8), and moderate-severely abnormal (SSS > 8) categories. The annualized cardiac event rate including cardiac death and non-fatal myocardial infarction was calculated over a mean follow-up period of 2.4 ± 1.4 years with a maximum of 6 years. ResultsThe cardiac event rate was statistically significantly lower in diabetic patients undergoing exercise stress MPI when compared to the diabetic patients undergoing pharmacological stress MPI across all three perfusion categories (1.3% vs 3.4%, 2.3% vs 5.7%, 4.2% vs 10.7%, respectively). Diabetic patients with no known CAD, who underwent exercise stress MPI had significantly lower cardiac events across all three perfusion categories as compared to the remainder of the diabetic population. Ability to perform exercise stress test was the strongest multivariate predictor of favorable outcome, whereas ejection fraction < 50%, abnormal perfusion imaging on SPECT MPI, and increasing age stood out as independent predictors of adverse outcome in the diabetic patients. Within the abnormal perfusion category, the annualized cardiac event rate among patients undergoing exercise stress SPECT MPI was not statistically different between the diabetic and non-diabetic cohorts. ConclusionDiabetic patients undergoing exercise SPECT MPI have a significantly better prognosis than those undergoing pharmacological stress, more similar to patients without diabetes. In patients with diabetes exercise stress test MPI identifies low risk patients and provides precise risk stratification.

Reclassification of Cardiovascular Risk in Patients With Normal Myocardial Perfusion Imaging Using Heart Rate Response to Vasodilator Stress

Previous studies have shown that patients with normal vasodilator myocardial perfusion imaging (MPI) findings remain at a greater risk of future cardiac events than patients with normal exercise MPI findings. The aim was to assess improvement in risk classification provided by the heart rate response (HRR) in patients with normal vasodilator MPI findings when added to traditional risk stratification. We retrospectively studied 2,000 patients with normal regadenoson or adenosine MPI findings. Risk stratification was performed using Adult Treatment Panel III framework. Patients were stratified by HRR (percentage of increase from baseline) into tertiles specific to each vasodilator. All-cause mortality and cardiac death/nonfatal myocardial infarction (MI) ≤2 years from the index MPI were recorded. During follow-up, 11.8% patients died and 2.7% patients experienced cardiac death/nonfatal MI in the adenosine and regadenoson groups, respectively. The patients who died had a greater Framingham risk score (12 ± 4 vs 11 ± 4, p= 0.009) and lower HRR (22± 16 vs 32 ± 21, p <0.0001). In an adjusted Cox model, the lowest tertile HRR was associated with an increased risk of mortality (hazard ratio 2.1) and cardiac death/nonfatal MI (hazard ratio 2.9; p <0.01). Patients in the highest HRR tertile, irrespective of the Adult Treatment Panel III category, were at low risk. When added to the Adult Treatment Panel III categories, the HRR resulted in net reclassification improvement in mortality of 18% and cardiac death/nonfatal MI of 22%. In conclusion, a blunted HRR to vasodilator stress was independently associated with an increased risk of cardiac events and overall mortality in patients with normal vasodilator MPI findings. The HRR correctly reclassified a substantial proportion of these patients in addition to the traditional risk classification models and identified patients with normal vasodilator MPI findings, who had a truly low risk of events.

The Central Role of the Nurse in Process Improvement Relating to Pharmacologic Stress Testing

Pharmacologic stress myocardial perfusion imaging is a noninvasive method for evaluating coronary artery disease in patients unable to exercise sufficiently to achieve a heart rate high enough to facilitate satisfactory imaging. The nuclear cardiology nurse is an invaluable member of the laboratory team that performs these tests. In this specialist role, the nurse must have a thorough knowledge of the different pharmacologic stress agents (dipyridamole, adenosine, regadenoson, and dobutamine) that can be used. This should comprise an understanding of their mechanisms of action, contraindications, drug-drug interactions, adverse effects, and administration protocols. By drawing on this knowledge, the nurse is able to verify that the right agent has been selected for each patient based on his/her medical history. The nurse also can help patients follow pretest instructions (such as withholding caffeine and certain medications) by explaining that the measures are necessary for a safe and successful procedure and that violation may result in test cancellation or postponement. On the day of the stress test, the nurse has an important role in safeguarding the patient as well as providing support and reassurance throughout the different stages of the examination. Responsibilities include explaining the entire procedure to the patients, notably, what they will be asked to do, the effect of the stress agent, the timing of each step, the adverse effects that they may experience, how any adverse events will be managed, and the importance of remaining still during imaging. This central role of the nuclear cardiology nurse in overseeing the practical aspects of the pharmacologic stress test has important implications in terms of optimizing the productivity and efficiency of their noninvasive cardiology laboratory and nuclear medicine department.

515 Early and late cardiovascular outcomes of pharmacologic stress myocardial perfusion imaging (MPI)

515 Early and late cardiovascular outcomes of pharmacologic stress myocardial perfusion imaging (MPI)

Safety of adenosine pharmacologic stress myocardial perfusion imaging in orthotopic cardiac transplant recipients: a single center experience of 102 transplant patients

Denervation super-sensitivity to adenosine is well described in cardiac transplant (CT) patients particularly early after transplant. The safety and hemodynamic effects of adenosine SPECT (A-SPECT) has not been described in a large series of CT patients. Single center retrospective study of 102 CT patients undergoing A-SPECT were compared to an age-gender matched patients in a 2:1 fashion who underwent A-SPECT in the same time period. Multivariate logistic regression model were used to identify independent predictors of advanced AV block. The average time from CT to A-SPECT was 8.5±4.5years. Average age was 57years with 80% males. In comparison to the control group, adenosine infusion was associated with a higher incidence of sinus pause (4.9% vs. 0%), 2nd (11.8% vs. 4.9%) and 3rd degree AVB (2.9% vs. 0%) in CT patients (all P<0.05). Prior use of aspirin and baseline 1st degree AVB were significant independent predictors of adenosine induced AVB. Baseline right or left bundle branch block, beta-blockers, calcium blockers or digoxin were not associated with occurrence of AVB. Only 1.9% of A-SPECT studies were terminated due to bradyarrythmia with 1 patient requiring aminophylline. There were no significant immediate or long term adverse events in these patients. Adenosine pharmacologic stress is associated with a higher incidence of AVB and sinus pause in CT patients reflecting persistence of super sensitivity late after CT. Nevertheless these bradyarrythmias are transient without any sequelae suggesting that A-SPECT can be performed safely in CT patients.