Early dipyridamole (99m)Tc-sestamibi single photon emission computed tomographic imaging 2 to 4 days after acute myocardial infarction predicts in-hospital and postdischarge cardiac events: comparison with submaximal exercise imaging

Risk stratification with vasodilator stress SPECT myocardial perfusion imaging in patients with elevated cardiac biomarkers

BACKGROUND

Although the diagnostic accuracy and prognostic utility of vasodilator stress MPI have been well established in the non-acute setting, the efficacy of all of the vasodilator stressors in risk stratifying post-MI patients as well as the evaluation of cardiac troponin elevation of unclear etiology is not established. Accordingly, the aim of the present study was to investigate the prognostic efficacy of vasodilator stress MPI in the setting of elevated cardiac troponin to accurately risk stratify these higher-risk patients.

METHODS

All patients from two tertiary centers, from 1/1/2010 through 12/31/2012, with elevated cardiac biomarkers within < 7 days and undergoing stress SPECT MPI testing were studied. Results of stress MPI were scored using a 17-segment model based on semiquantitative scoring as normal or abnormal (mild, moderate, or severe) using a total perfusion defect (TPD) of 0%, 1-10%, 10-20%, and > 20%. Mortality data through the year 2014 were obtained from the National Death Index, and survival analyses were performed. The primary endpoint was all-cause mortality with the secondary endpoint being cardiac mortality.

RESULTS

A total of 503 patients were followed for an average of 33.6 ± 16.2 months, with a mean age of 69.3 years; 53.7% male; and a majority (88.7%) of them undergoing vasodilator stress. A significant increase in all-cause mortality was seen based on the severity of TPD results for all vasodilators (P < .0001) and regadenoson (P < .0001). Similar prognostic ability was seen for all-cause mortality. This association was maintained even after adjustment for cardiac risk factors, previous coronary disease, and troponin quartiles. MPI results (stress TPD and LVEF) added to traditional cardiac risk factors, and troponin values resulted in a significant incremental increase in the ability to predict all-cause and cardiac mortality, and stress TPD remained independently predictive for both all-cause and cardiac mortality in a multivariate model.

CONCLUSION

Vasodilator stress (including regadenoson) MPI effectively risk stratifies patients with recently elevated cardiac biomarkers, with the increasing risk of mortality with the increasing severity of perfusion defects. It provides incremental prognostic value, in addition to clinical factors and degree of troponin elevation.

Impact of the Charlson Comorbidity Index score on risk prediction by single-photon emission computed tomography myocardial perfusion imaging following myocardial infarction

Background

Comorbidity is common among patients with myocardial infarction (MI). We examined whether comorbidity level modified the single-photon emission computed tomography myocardial perfusion imaging (SPECT MPI)-based prediction of 5-year risk of MI and all-cause death in patients with MI.

Methods

This cohort study included patients with prior MI having a SPECT MPI at Aarhus University Hospital, Denmark, 1999–2011. Using nationwide registries, we obtained information on comorbidity levels (low, moderate, and severe) and outcomes. We computed risk and hazard ratios (HRs) with 95% confidence intervals (CIs) for MI and all-cause death, comparing normal (no defects) versus abnormal scan (reversible and/or fixed defects) using Cox regression adjusting for sex, age, and comorbidity level.

Results

We identified 1,192 patients with MI before SPECT MPI. The 5-year risk for patients with normal versus abnormal scans were 11.7% versus 18.3% for MI, and 8.0% versus 13.2% for all-cause death, respectively. The overall 5-year adjusted HR (aHR) of MI was 1.56 (95% CI: 1.09–2.21), 1.33 (95% CI: 0.82–2.15) with low comorbidity, 1.39 (95% CI: 0.68–2.83) with moderate comorbidity, and 2.53 (95% CI: 1.14–5.62) with severe comorbidity. Similarly, the 5-year aHR for all-cause death was 1.39 (95% CI: 0.90–2.14) overall; 2.33 (95% CI: 0.79–6.84) with low comorbidity, 2.05 (95% CI: 0.69–6.06) with moderate comorbidity, and 1.07 (95% CI: 0.64–1.80) with severe comorbidity.

Conclusion

We conclude that comorbidity level may modify the 5-year risk prediction associated with an abnormal SPECT MPI scan in patients with previous MI.

Six-Year Prognostic Value of Microvascular Obstruction After Reperfused ST-Elevation Myocardial Infarction as Assessed by Contrast-Enhanced Cardiovascular Magnetic Resonance

Although recent studies showed the prognostic value of cardiac magnetic resonance (CMR) parameters especially microvascular obstruction (MO) after reperfused ST-elevation myocardial infarction (STEMI), a study assessing their prognostic significance for long-term follow-up is missing so far. The objective of this study was to determine the prognostic impact of MO on long-term prognosis after reperfused first STEMI in a setting allocating CMR-assessed parameters to hard clinical events only. In 249 patients, CMR was performed after reperfused STEMI, and hereby, left ventricular ejection fraction (LVEF), infarct size (IS), and the amount of MO were quantified. Follow-up (median 6.0 years) was obtained regarding occurrence of major adverse cardiac events (MACE). MACE occurred more often in patients showing presence of MO (MO vs no MO: n = 61 [54%] vs n = 12 [9%], p <0.0001). By multivariate analysis, the extent of MO remained the strongest predictor (p <0.001) for occurrence of MACE and provided incremental prognostic value over clinical variables and LVEF (p = 0.028, c-index increase from 0.723 to 0.817). In conclusion, CMR-assessed MO proves predictive for assessment of 6-year prognosis in patients after reperfused first STEMI and provides incremental prognostic information over clinical variables and LVEF in a setting based on hard end points.

99mTc tetrofosmin myocardial perfusion scintigraphy in CAD. Performance with early and standard delayed acquisition and fractional flow reserve

AIM

Early stress imaging (15 min after injection of the radiopharmaceutical) in 99mTc tetrofosmin myocardial perfusion scintigraphy (MPS) has been shown feasible in comparison to standard imaging after 45 minutes, but the effects on image quality and diagnostic accuracy ask for further evaluation.

PATIENTS, METHODS

97 patients (61 men, 36 women, age 69 ± 11 years) underwent both early (EA) and standard (SA) acquisition (after 14 ± 4 min and 43 ± 6 min, respectively) using 99mTc tetrofosmin gated SPECT with iterative reconstruction. Sub-diaphragmatic tracer activity and image quality was scored in a 4-point scale by blinded observers. Semiquantitative myocardial perfusion analysis was performed on a 17-segment model using standard cardiac quantification SPECT software (4 DM-SPECT). Stenoses of indeterminate haemodynamic significance were validated by measurement of fractional flow reserve (FFR).

RESULTS

Extra-cardiac tracer activity was more commonly found in EA (43%) than in SA (38%), but without any diagnostic impact in > 95% of the patients. The mean summed stress score was significantly higher for early than standard imaging (6.4 ± 6.3 vs. 5.6 ± 6.1, p = 0.009). The amount of ischaemic area was not significantly different (EA: 9.1 ± 6.7 % vs. SA: 7.8 ± 6.9 %). The mean stress ejection fraction was 52 ± 11% (EA) compared to 55 ± 11 % (SA) (p = ns). FFR was inversely related to SDS at early (r = -0.704, p < 0.05) and standard (r = -0.678, p < 0.05) acquisition. All patients with a FFR < 0.8 (considered as hemodynamically significant stenoses) revealed a positive scan.

CONCLUSION

Stress 99mTc tetrofosmin MPS with early acquisition is feasible and at least equally accurate when iterative reconstruction is applied.

Exercise training early after acute myocardial infarction reduces stress-induced hypoperfusion and improves left ventricular function

PURPOSE

Exercise training might exert its beneficial effects on myocardial perfusion by inducing coronary vascular adaptations or enhancing collateralization. We evaluated whether long-term exercise-based cardiac rehabilitation started early after ST-elevation acute myocardial infarction (STEMI) improves myocardial perfusion and left ventricular (LV) function.

METHODS

Forty-six patients with recent STEMI and residual inducible hypoperfusion were randomized into two groups: 25 enrolled in a 6-month outpatient exercise-based cardiac rehabilitation programme (group T) and 21 discharged with generic instructions for maintaining physical activity and correct lifestyle (group C). All patients underwent cardiopulmonary exercise test and dipyridamole rest gated myocardial perfusion single photon emission computed tomography within 1 week after STEMI and at 6-month follow-up.

RESULTS

At follow-up, group T showed an improvement in peak oxygen consumption, oxygen pulse and in the slope of increase in ventilation over carbon dioxide output (all p < 0.01) associated with a reduction of stress-induced hypoperfusion (p < 0.01) and an improvement in resting and post-stress wall motion score indexes (both p < 0.01), resting and post-stress wall thickening score indexes (both p < 0.05) and resting and post-stress LV ejection fraction (both p < 0.05). On the contrary, no changes in cardiopulmonary indexes, myocardial perfusion and LV function parameters were observed in group C at follow-up.

CONCLUSION

Exercise training started early after STEMI reduces stress-induced hypoperfusion and improves LV function and contractility. Exercise-induced changes in myocardial perfusion and function were associated with the absence of unfavourable LV remodelling and with an improvement of cardiovascular functional capacity.

Computed tomography imaging in myocardial infarction

Over recent decades, noninvasive imaging has become well established in the diagnostic work-up of patients suffering from myocardial infarction. It provides insights into the individual patient's prognosis and guides therapeutic decisions. MRI has long been considered the standard of reference in the noninvasive imaging of myocardial infarction. Only recently have different multidetector-row spiral computed tomography (MDCT) techniques successfully been evaluated for the visualization of myocardial infarction. This article describes different concepts of cardiac MDCT imaging in acute and chronic myocardial infarction. MDCT assessment of myocardial edema, myocardial perfusion and delayed myocardial contrast enhancement are introduced, with the latter evolving as key concept of viability imaging by means of MDCT. The current status of MDCT in the diagnostic work-up of myocardial infarction is reviewed.

[Impact of myocardial perfusion gated-SPECT on the decision to perform coronary angiography in patients with left ventricular dysfunction of ischemic origin]

OBJECTIVES

The aim of this study was to analyze how the myocardial perfusion gated-SPECT (Single Photon Emission Computed Tomography) influences the practice of a coronary angiography in patients with ischemic cardiomyopathy (IM).

PATIENTS AND METHODS

A total of 120 consecutive patients (mean age: 64.9±11.5 years, 25 female) with IM (left ventricular ejection fraction ≤40%) and without previous coronary angiography were evaluated by myocardial perfusion gated-SPECT (96 stress-rest and 24 only at rest). The ventricular ejection fraction (EF) was obtained at rest by gated-SPECT in all patients. The ischemic origin of the systolic dysfunction was established by means of coronary angiography in 64 patients and by previous myocardial infarction in the rest. Gated-SPECT results of these 64 patients were compared with those of 56 patients in whom coronary angiography had not been indicated.

RESULT

Scintigraphic myocardial ischemia (HR: 5.2; CI 95%: 2.68 to 10.35) in patients who were able to perform the stress-rest test) and who had severely impaired EF (<30%) (HR: 0.9; CI 95%: 0.89 to 0.99) were the best independent predictors of coronary angiography. On the contrary, scintigraphic criteria of viability were not a determinant, from the statistical point of view, of coronary angiography in this series.

CONCLUSIONS

In patients with IM, demonstration of ischemia and severe reduction of the EF, but not detection of viable myocardium, prompted the performance of coronary angiography.

Cardiac imaging after myocardial infarction

After myocardial infarction, optimal clinical management depends critically on cardiac imaging. Remodelling and heart failure, presence of inducible ischaemia, presence of dysfunctional viable myocardium, future risk of adverse events including risk of ventricular arrhythmias, need for anticoagulation, and other questions should be addressed by cardiac imaging. Strengths and weaknesses, recent developments, choice, and timing of the different non-invasive techniques are reviewed for this frequent clinical scenario.

Perspectives of nuclear diagnostic imaging in diabetic cardiomyopathy

Diabetic cardiomyopathy is a ventricular dysfunction in the absence of coronary artery disease, valvular or hypertensive heart disease. The mechanisms underlying diabetic cardiomyopathy may involve metabolic disturbances, myocardial fibrosis, small vessel disease, microcirculation abnormalities, cardiac autonomic neuropathy and insulin resistance. Diagnostic problems emerge because no specific disease pattern characterizes the disease and because there may be coexistence in diabetes of coronary artery disease and hypertension as independent but compounding causes of biochemical, anatomical and functional alterations impairing cardiac function. In this paper we will review the role of nuclear imaging today, concentrating on the diagnostic capabilities of radionuclide ventriculography, to study the effect of insulin resistance and, more extensively, gated-single photon emission computed tomography with Tc-99m labelled agents. A broad analysis will be dedicated to: 1) positron emission tomography using perfusion agents, with the potential to quantify resting and stress blood flow and coronary flow reserve; 2) radionuclide procedures evaluating aerobic and anaerobic cardiac metabolism; and 3) cardiac neurotransmission imaging, studying the autonomic neuropathy.

Early prediction of 30-day mortality after Q-wave myocardial infarction by echocardiographic assessment of left ventricular function--a pilot investigation

BACKGROUND

The GUSTO angiographic substudy demonstrated that left ventricular function measured 90 min after thrombolytic therapy was given had important prognostic implications at 30 days in patients with an acute myocardial infarction (MI).

HYPOTHESIS

Thirty-day prognosis after Q-wave MI can be determined by early echocardiographic assessment of left ventricular function.

METHODS

Using transthoracic echocardiography, semiquantitative ejection fraction and wall motion score index was assessed prospectively in 201 consecutive patients within 24 h following Q-wave MI. Independent experts blinded to the patient's status performed the echocardiographic assessment. All patients received standard medical care as dictated by the attending cardiologist.

RESULTS

Of the 201 patients, 24 (11.9%) died within 30 days, with 70% of the deaths occurring within 10 days after the infarction. Three deaths occurred in the 120 patients with an ejection fraction > or = 45% (2.5% mortality rate). In contrast, 21 deaths occurred among the 81 patients with an ejection fraction <45% (25.9% mortality rate) p = 0.0003. Two of the three patients who died in the high ejection fraction group died as a result of intracerebral hemorrhage from thrombolytic therapy. Ejection fraction was lower in nonsurvivors (32.3+/-10.3 vs. 46.3+/-13%) than in survivors, p < 0.0002. Wall motion score index (WMSI) of < 1.4 was associated with a 2.9% 30-day mortality (two deaths in 76 patients); WMSI of > or = 1.4 was associated with a 17.6% 30-day mortality (22 deaths in 125 patients), p = 0.0007. Average WMSI was higher in the nonsurvivors (1.95+/-0.5) than in survivors (1.52+/-0.45), p = 0.00001.

CONCLUSIONS

Echocardiographic assessment of left ventricular function during the first 24 h after an acute Q-wave MI can be performed in all patients regardless of stability. High-risk patients are identified early in the hospital course, with relative ease, at no risk and at an acceptable cost. An ejection fraction < 45% or WMSI > or = 1.4 identifies patients who are at a high risk of dying within 30 days. These are the patients who may benefit most from aggressive medical therapy and early angiography to assess coronary pathology.

Cardiac radionuclide imaging in stable coronary artery disease and acute coronary syndromes

INTRODUCTION

The increasing number of available cardiac imaging techniques has made the investigation of coronary artery disease (CAD) more complex. Appropriate patient referral depends on an understanding of the pre-test likelihood of CAD and the information provided by each test.

SOURCES OF DATA

This article describes myocardial perfusion scintigraphy (MPS) and summarizes evidence for its role in stable CAD and acute coronary syndromes with particular reference to current guidelines.

AREAS OF AGREEMENT

MPS has been extensively validated for the cost-effective diagnosis and prognosis of functionally significant CAD in both the acute and chronic settings. Its use is emphasized in the current NICE, national and international guidelines.

AREAS OF CONTROVERSY

Although normal MPS is associated with good outcomes, assessments of subclinical atherosclerosis such as coronary artery calcium scoring and computed tomography coronary angiography (CTA) demonstrate that non-flow-limiting CAD remains prognostically important.

GROWING POINTS

Technological developments, such as attenuation correction to improve diagnostic accuracy or analysis of left ventricular phase to detect dyssynchrony, carry the possibility of increasing the information that can be usefully gained from a single MPS study.

AREAS TIMELY FOR DEVELOPING RESEARCH

Of particular importance will be the role of MPS in an integrated imaging strategy that involves both anatomical and functional cardiac assessments. The use of hybrid technology that combines techniques such as MPS and CTA into a single imaging unit requires careful consideration with regard to diagnostic usefulness and cost-effectiveness.

EANM/ESC guidelines for radionuclide imaging of cardiac function

Radionuclide imaging of cardiac function represents a number of well-validated techniques for accurate determination of right (RV) and left ventricular (LV) ejection fraction (EF) and LV volumes. These first European guidelines give recommendations for how and when to use first-pass and equilibrium radionuclide ventriculography, gated myocardial perfusion scintigraphy, gated PET, and studies with non-imaging devices for the evaluation of cardiac function. The items covered are presented in 11 sections: clinical indications, radiopharmaceuticals and dosimetry, study acquisition, RV EF, LV EF, LV volumes, LV regional function, LV diastolic function, reports and image display and reference values from the literature of RVEF, LVEF and LV volumes. If specific recommendations given cannot be based on evidence from original, scientific studies, referral is given to "prevailing or general consensus". The guidelines are designed to assist in the practice of referral to, performance, interpretation and reporting of nuclear cardiology studies for the evaluation of cardiac performance.

Adenosine single photon emission computed tomography for assessing risk after myocardial infarction: recent developments

PURPOSE OF REVIEW

While the prognostic power of adenosine single photon emission computed tomography myocardial perfusion imaging has been validated in multiple patient populations including those with known or suspected coronary artery disease, the utility of this modality in assessing risk after an acute myocardial infarction in the primary angioplasty era is still a topic of debate.

RECENT FINDINGS

The INSPIRE trial showed that early adenosine single photon emission computed tomography myocardial perfusion imaging is capable of identifying low-risk patients for early hospital discharge after acute myocardial infarction. This novel study demonstrated that intensive medical therapy is a reasonable strategy in low, intermediate, and high-risk post-myocardial infarction patients with preserved left ventricular function.

SUMMARY

The INSPIRE trial established the role for early adenosine single photon emission computed tomography myocardial perfusion imaging as a tool for risk stratification in stable patients after an acute myocardial infarction and provided evidence that intensive medical therapy is comparable to coronary revascularization in suppressing ischemia and presumably improving cardiac outcomes. It remains to be seen whether these new findings will alter current American College of Cardiology/American Heart Association guidelines, which emphasize a primary role of coronary revascularization in acute coronary syndromes.

Cardiac 82Rubidium PET/CT: initial European experience

PURPOSE

Myocardial perfusion with PET/CT has advantages over conventional SPECT. We describe our initial European experience using (82)Rubidium-PET/CT, as part of a clinical myocardial perfusion service.

METHODS

We studied the first 100 patients (64 male; 36 female, mean age = 60: SD +/-12.5y, mean body mass index = 30: SD +/-6.9kg/m( 2 )) who underwent (82)Rubidium cardiac PET/CT in our institution. Thirty patients had recently undergone coronary angiography. Patients underwent imaging during adenosine infusion and at rest. Images were acquired over 5 minutes using a GE-PET/CT instrument. Image quality was described as good, adequate or inadequate. Images were reported patient-by-patient by a minimum of five nuclear medicine physicians. A segment-by-segment analysis (17-segment model) was also performed.

RESULTS

Image quality was good in 77%, adequate 23% and inadequate 0%. There was no statistical difference in image quality between obese and non-obese patients (Fisher's exact test, p = 0.2864). 59% had normal perfusion studies, 29% had inducible ischaemia, 12% had myocardial infarction (11% with super added ischaemia). There was reduced (82)Rubidium uptake in 132/1700 segments during stress. There was reduced (82)Rubidium uptake at rest in 42/1700 segments. The (82)Rubidium PET/CT findings were consistent with the angiographic findings in 28/30 cases.

CONCLUSION

We show that, even from initial use of (82)Rubidium, it is possible to perform myocardial perfusion studies quickly with good image quality, even in the obese. The PET findings correlated well in the third of the cases where angiography was available. As such, (82)Rubidium cardiac PET/CT is likely to be an exciting addition to the European nuclear physician/ cardiologist's radionuclide imaging arsenal.

Cardiovascular Molecular Imaging

The goal of this review is to highlight how molecular imaging will impact the management and improved understanding of the major cardiovascular diseases that have substantial clinical impact and research interest. These topics include atherosclerosis, myocardial ischemia, myocardial viability, heart failure, gene therapy, and stem cell transplantation. Traditional methods of evaluation for these diseases will be presented first, followed by methods that incorporate conventional and molecular imaging approaches.

Safety and diagnostic accuracy of stress cardiac magnetic resonance imaging vs exercise tolerance testing early after acute ST elevation myocardial infarction

OBJECTIVE

To determine the safety and diagnostic accuracy of adenosine-stress cardiac magnetic resonance (CMR) perfusion imaging early after acute ST elevation myocardial infarction (STEMI) compared with standard exercise tolerance testing (ETT).

DESIGN AND SETTING

Cross sectional observational study in a university teaching hospital.

PATIENTS

35 patients admitted with first acute STEMI.

INTERVENTIONS

All patients underwent a CMR imaging protocol which included rest and adenosine-stress perfusion, viability, and cardiac functional assessment. All patients also had an ETT (modified Bruce protocol) and x ray coronary angiography.

MAIN OUTCOME MEASURES

Safety and diagnostic accuracy of adenosine-stress perfusion CMR vs ETT early after STEMI in identifying patients with significant coronary stenosis (>or=70%) and the need for coronary revascularisation. Also, to determine if CMR can distinguish between ischaemia in the peri-infarct zone and ischaemia in remote myocardium.

RESULTS

CMR imaging was well tolerated (all patients completed the protocol) and no complications occurred. CMR was more sensitive (86% vs 48%, p = 0.0074) and more specific than ETT (100% vs 50%, p<0.0001) for detecting significant coronary stenosis, and more sensitive for predicting revascularisation (94% vs 56%, p = 0.039). Inducible ischaemia in the infarct related artery territory was seen in 21 of 35 patients and was associated with smaller infarct size and less transmurality of infarction.

CONCLUSIONS

Adenosine-stress CMR imaging is safe early after acute STEMI and identifies patients with significant coronary stenosis more accurately than ETT.

A Multinational Study to Establish the Value of Early Adenosine Technetium-99m Sestamibi Myocardial Perfusion Imaging in Identifying a Low-Risk Group for Early Hospital Discharge After Acute Myocardial Infarction

OBJECTIVES

The purpose of this study was to determine whether gated adenosine Tc-99m sestamibi single-photon emission computed tomography (ADSPECT) could accurately define risk and thereby guide therapeutic decision making in stable survivors of acute myocardial infarction (AMI).

BACKGROUND

Controversy continues as to the role of noninvasive stress imaging in stratifying risk early after AMI.

METHODS

The INSPIRE (Adenosine Sestamibi Post-Infarction Evaluation) trial is a prospective multicenter trial which enrolled 728 clinically stable survivors of AMI who had gated ADSPECT within 10 days of hospital admission and subsequent 1-year follow-up. Event rates were assessed within prospectively defined INSPIRE risk groups based on the adenosine-induced left ventricular perfusion defect size, extent of ischemia, and ejection fraction.

RESULTS

Total cardiac events/death and reinfarction significantly increased within each INSPIRE risk group from low (5.4%, 1.8%), to intermediate (14%, 9.2%), to high (18.6%, 11.6%) (p < 0.01). Event rates at 1 year were lowest in patients with the smallest perfusion defects but progressively increased when defect size exceeded 20% (p < 0.0001). The perfusion results significantly improved risk stratification beyond that provided by clinical and ejection fraction variables. The low-risk INSPIRE group, comprising one-third of all enrolled patients, had a shorter hospital stay with lower associated costs compared with the higher-risk groups (p < 0.001).

CONCLUSIONS

Gated ADSPECT performed early after AMI can accurately identify a sizeable low-risk group who have a <2% death and reinfarction rate at 1 year. Identifying these low-risk patients for early hospital discharge may improve utilization of health care resources at considerable cost savings.

Fractional Flow Reserve of Infarct-Related Arteries Identifies Reversible Defects on Noninvasive Myocardial Perfusion Imaging Early After Myocardial Infarction

OBJECTIVES

We hypothesized that fractional flow reserve (FFR) of an infarct-related artery (IRA) early after myocardial infarction (MI) identifies inducible ischemia on noninvasive imaging.

BACKGROUND

Early after MI, IRAs frequently have angiographically indeterminant lesions. Whether FFR can detect reversible perfusion defects early after MI when dynamic microvascular abnormalities are present is not known.

METHODS

Rest and dipyridamole (DP)-stress 99mTc sestamibi single-photon emission computed tomography (SPECT) were performed in 48 patients 3.7 +/- 1.3 days after MI, with 23 patients undergoing concurrent myocardial contrast echocardiography (MCE). Angiography, FFR, and percutaneous coronary intervention (PCI) of the IRA (as necessary) were subsequently performed. Follow-up SPECT was performed 11 weeks after PCI to identify true reversibility on baseline SPECT.

RESULTS

The sensitivity, specificity, positive and negative predictive value, and concordance of FFR < or =0.75 for detecting reversibility on SPECT were 88%, 50%, 68%, 89%, and 71% (chi-square <0.001), respectively; which improved to 88%, 93%, 88%, 93%, and 91% (chi-square <0.001), respectively, for the detection of true reversibility. The corresponding values of FFR < or =0.75 for detecting reversibility on DP-MCE were 90%, 100%, 100%, 75%, and 93% (chi-square <0.001), respectively, and on either SPECT or MCE were 88%, 93%, 91%, 91%, and 91% (chi-square <0.001), respectively. The optimal FFR value for discriminating inducible ischemia on noninvasive imaging was 0.78.

CONCLUSIONS

Fractional flow reserve of the IRA accurately identifies reversibility on noninvasive imaging early after MI. These findings support the utility of FFR early after MI.

Depressed heart rate response to vasodilator stress for myocardial SPECT predicts mortality in patients after myocardial infarction

BACKGROUND

As heart rate (HR) response during vasodilator stress myocardial perfusion studies can be a marker of HR variability, we investigated its prognostic value in patients after myocardial infarction (MI).

METHODS

Subjects were 147 survivors of MI who underwent vasodilator stress thallium-201 scintigraphy. HR response was measured as peak to basal (P/B) ratios during vasodilator infusion. End points for survival analysis were all-cause deaths, non-fatal recurrent MI, and soft events.

RESULTS

HR response was significantly depressed in the post-MI patients compared to controls (p<0.0005). HR response correlated to LVEF (r=0.37, p<0.0001) and summed stress scores (r=-0.18, p<0.05), but not with antianginal medication. During 58+/-30 mo of follow-up, there were 15 deaths, 7 recurrent MI, and 11 soft events. Low HR response, old age, low LVEF, and high difference score were significant univariate risk factors for death. Multivariate analysis identified low HR response (p=0.03), high stress score (p=0.02), and low LVEF (p=0.05) as independent predictors of mortality. The predictive value of HR response was incremental to that offered by other variables (p=0.02).

CONCLUSIONS

HR response, readily attained during vasodilator stress myocardial perfusion studies, may provide useful additional prognostic information in post-MI patients.

Correspondence between left ventricular 17 myocardial segments and coronary arteries

AIMS

The last guidelines recommend a standardized 17-segment model for tomographic imaging of the left ventricle. The aim of this study is to analyse the correspondence of the 17 left ventricular segments with each coronary artery by myocardial perfusion SPECT studies.

METHODS AND RESULTS

Fifty patients selected for percutaneous revascularization of one coronary artery [24 left anterior descending (LAD), 15 right coronary artery (RCA), and 11 left circumflex (LCX)] were included. The (99m)Tc-labelled compound was injected immediately after the inflation of the balloon during percutaneous coronary angioplasty. At least 90 s of complete occlusion time was required. Maximal contour of regions of hypoperfusion corresponding to each coronary artery occlusion were delineated over the polar map of 17 segments. Nine segments corresponded to only one coronary artery: eight to LAD (basal anterior, basal anteroseptal, mid-anterior, mid-anteroseptal, apical anterior, apical septal, apical lateral, and apex) and one to LCX (basal anterolateral). Basal inferoseptal, mid-inferoseptal, and apical inferior segments could correspond to LAD or RCA. Basal inferior, basal inferolateral, mid-inferior, and mid-inferolateral segments could correspond to RCA or LCX, whereas the mid-anterolateral segment could correspond to LAD or LCX.

CONCLUSION

The most specific segments (anterior, anteroseptal, and all apical segments except the infero-apical) correspond to LAD but no segment can be exclusively attributed to the RCA. Inferoseptal segments can be attributed to LAD or RCA, inferior and inferolateral segments to RCA or LCX, and mid-anterolateral segment to LAD or LCX.

Prognostic value of adenosine Tl-201 myocardial perfusion imaging after acute myocardial infarction: results of a prospective clinical trial

BACKGROUND

We have previously shown in retrospective studies that adenosine myocardial perfusion imaging (MPI) done after acute myocardial infarction (AMI) can effectively predict the risk of future cardiac events in these patients. The objective of this study was to validate these observations in a prospective clinical trial.

METHODS AND RESULTS

One hundred twenty-six stable patients underwent quantitative adenosine MPI at a mean of 4.5 +/- 2.9 days after AMI. On the basis of the MPI results, they were divided into 3 risk groups: low risk (< 20% perfusion defect), intermediate risk (> or = 20% perfusion defect with < 10% ischemia), and high risk (> or = 20% perfusion defect with > 10% ischemia). The patients were followed up for 11 +/- 5 months for the occurrence of cardiac events: death, myocardial infarction, unstable angina, or congestive heart failure. The actual event rates correlated very well with the prespecified risk groups (19% for the low-risk group, 28% for the intermediate-risk group, and 78% for the high-risk group; P < .001). The significant multivariate predictors for events were female gender (relative risk [RR], 2.90; P = .002), left ventricular ejection fraction (RR, 1.34; P = .04), and ischemic defect size (RR, 1.46; P = .001), with a global chi2 value of 26.7.

CONCLUSION

This study demonstrates, in a prospectively designed clinical trial, that quantitative adenosine MPI performed soon after AMI can effectively predict the risk of future cardiac events. These findings are currently being validated in an ongoing, large, multicenter, international clinical trial.

Coronary artery disease is common in nonuremic, asymptomatic type 1 diabetic islet transplant candidates

OBJECTIVE

Coronary artery disease (CAD) is the most common cause of death in patients with type 1 diabetes. Asymptomatic CAD is common in uremic diabetic patients, but its prevalence in nonuremic type 1 diabetic patients is unknown. The prevalence of CAD was determined by coronary angiography and the performance of noninvasive cardiac investigation evaluated in type 1 diabetic islet transplant (ITX) candidates with preserved renal function.

RESEARCH DESIGN AND METHODS

A total of 60 consecutive type 1 diabetic ITX candidates (average age 46 years [mean 24-64], 23 men, and 47% ever smokers) underwent coronary angiography, electrocardiographic stress testing (EST), and myocardial perfusion imaging (MPI) in a prospective cohort study. CAD was indicated on angiography by the presence of stenoses >50%. Models to predict CAD were examined by logistic regression.

RESULTS

Most subjects (53 of 60) had no history or symptoms of CAD; 23 (43%) of these asymptomatic subjects had stenoses >50%. CAD was associated with age, duration of diabetes, hypertension, and smoking. Although specific, EST and MPI were not sensitive as predictors of CAD on angiography (specificity 0.97 and 0.93, sensitivity 0.17 and 0.04, respectively) but helped identify two of three subjects requiring revascularization. EST and MPI did not enhance logistic regression models. A clinical algorithm to identify low-risk subjects who may not require angiography was highly sensitive but was applicable only to a minority (n = 8, sensitivity 1.0, specificity 0.27, negative predictive value 1.0).

CONCLUSIONS

Nonuremic type 1 diabetic patients with hypoglycemic unawareness and/or metabolic lability referred for ITX are at high risk for asymptomatic CAD despite negative noninvasive investigations. Aggressive management of cardiovascular risk factors and further investigation into optimal cardiac risk stratification in type 1 diabetes are warranted.

[Value of gated SPECT myocardial perfusion imaging for individual cardiac risk assessment]

Myocardial perfusion imaging enables not only accurate diagnosis of disease but also entails prognostic value. Myocardial perfusion SPECT contributes to assessment of future cardiac events independently of other clinical parameters. A normal stress myocardial perfusion scan is associated with a favorable prognosis independent of history, symptoms, and exercise electrocardiography test variables. Cardiac risk and benefit from invasive therapeutic strategies increase in relation to the severity of the abnormality of perfusion and function assessed by gated myocardial perfusion SPECT. Thus, stress myocardial perfusion imaging may serve as a gatekeeper for referral to coronary angiography enabling effective risk stratification in patients with suspected or documented coronary artery disease.

Prognostic value of stress Tc-99m tetrofosmin SPECT in patients with previous myocardial infarction: impact of scintigraphic extent of coronary artery disease

BACKGROUND

Our objective was to assess the prognostic value of the scintigraphic extent of coronary artery disease on stress technetium 99m tetrofosmin single photon emission computed tomography in patients with previous myocardial infarction.

METHODS AND RESULTS

We studied 383 patients (280 men and 103 women; mean age, 60 +/- 11 years) more than 3 months after an acute myocardial infarction by exercise bicycle or dobutamine (up to 40 mug . kg -1 . min -1 ) stress Tc-99m tetrofosmin myocardial perfusion tomography. Stress images were acquired 1 hour after stress, and rest images were acquired 24 hours after stress testing. An abnormal study was defined as one demonstrating a reversible or fixed perfusion abnormality. Myocardial segments were assigned to corresponding coronary arteries as follows: the apex, anterior wall, and anterior septum were assigned to the left anterior descending coronary artery; the posterolateral wall was assigned to the left circumflex artery; and the basal posterior septum and inferior wall were assigned to the right coronary artery. During a mean follow-up of 4.3 +/- 2.1 years, 48 cardiac events occurred (36 cardiac deaths and 12 nonfatal myocardial infarctions). Myocardial perfusion was normal in 51 patients, abnormal in a single-vessel distribution in 170 patients, and abnormal in a multivessel distribution in 162 patients. The annual cardiac event rates in these groups were 0.4%, 2.6%, and 4%, respectively. In a multivariate analysis model, independent predictors of cardiac events were diabetes mellitus (odds ratio [OR], 2.3; 95% confidence interval [CI], 1.4-4.5), history of congestive heart failure (OR, 2.7; 95% CI, 1.4-4), age (OR, 1.05; 95% CI, 1.01-1.08), and scintigraphic extent of coronary artery disease (OR, 4.2; 95% CI, 1.8-9.1).

CONCLUSION

Stress Tc-99m tetrofosmin myocardial perfusion imaging provides independent prognostic information for the risk stratification of patients with previous myocardial infarction. The event rate is directly related to the scintigraphic extent of coronary artery disease. Patients with normal perfusion have an excellent event-free survival rate.

Adenosine sestamibi SPECT post-infarction evaluation (INSPIRE) trial: A randomized, prospective multicenter trial evaluating the role of adenosine Tc-99m sestamibi SPECT for assessing risk and therapeutic outcomes in survivors of acute myocardial infarction

BACKGROUND

Preliminary studies indicate that adenosine myocardial perfusion single photon tomography (SPECT) can safely and accurately stratify patients into low and high risk groups early after acute myocardial infarction (AMI).

METHODS AND RESULTS

INSPIRE is a prospective, randomized multicenter trial which enrolled 728 clinically stable survivors of AMI. Following baseline adenosine sestamibi gated SPECT, patients were classified as low, intermediate or high risk based on the quantified total and ischemic left ventricular (LV) perfusion defect size (PDS). A subset of high risk patients with a LV ejection fraction > or =35% were randomized to a strategy of either intensive medical therapy or coronary revascularization. Adenosine SPECT was repeated at 6-8 weeks to determine the relative effects of anti-ischemic therapies on total and ischemic PDS (primary endpoint). All patients were followed for one year. The baseline demographic, clinical and scintigraphic characteristics of the study population are presented. Adenosine SPECT was performed within 1 day of admission in 12% of patients and in 64% by Day 4.

CONCLUSION

The unique study design features of INSPIRE will further clarify the role of adenosine sestamibi SPECT in defining initial patient risk after AMI and in monitoring the benefits of intensive anti-ischemic therapies.

Stress radionuclide myocardial perfusion imaging detects more residual ischemia than stress echocardiography following acute myocardial infarction

OBJECTIVES

This investigation sought to compare the abilities of stress radionuclide myocardial perfusion imaging and stress echocardiography to detect residual ischemia in patients following acute myocardial infarction (MI).

BACKGROUND

Stress radionuclide myocardial perfusion imaging and stress echocardiography are both commonly used to assess patients (patients.) in the immediate post MI period. However, the relative value of these techniques in identifying post MI ischemia remains unclear.

METHODS

Eighteen patients. underwent both dipyridamole radionuclide perfusion imaging and dobutamine stress echocardiography on the same day or on consecutive days, 3-7 days following uncomplicated acute MI. Pts. who had an acute percutaneous intervention were excluded. Images were reviewed with clinical information available, but blinded to the opposing modality, for perfusion defects, wall motion abnormalities (WMA), and evidence of ischemia (reversible defect(s) on perfusion imaging, worsening WMA on stress echocardiography). Of the 18 patients, 11 subsequently underwent cardiac catheterization.

RESULTS

Perfusion imaging identified defects in 16 (89%) patients, of whom 15 (83% of total) were found to be ischemic. Stress echocardiography identified a fixed wall motion abnormality in 17 (94%) and ischemia in 8 (44%, p < 0.05 compared with perfusion imaging ischemia). Among 11 patients who underwent catheterization, there was a trend towards perfusion imaging identifying more ischemia in the territory of an obstructed (> or = 70%) vessel--100% (11/11) vs. 64% (7/11) for stress echocardiography (p = 0.09).

CONCLUSION

In the immediate post-infarction period, dipyridamole stress radionuclide myocardial perfusion imaging more often shows evidence of residual ischemia than dobutamine stress echocardiography.