Prognostic value of exercise 201Tl tomography in patients treated with thrombolytic therapy during acute myocardial infarction

Does Transient Receptor Potential Vanilloid Type 1 Alleviate or Aggravate Pathological Myocardial Hypertrophy?

Transient receptor potential vanilloid type 1 (TRPV1) is a non-selective cation channel, which is involved in the endogenous stress adaptation mechanism for protection of the heart as well as the occurrence and development of some heart diseases. Although the effect of activation of the TRPV1 channel on different types of non-neural cells in the heart remains unclear, most data show that stimulation of sensory nerves expressing TRPV1 or stimulation/overexpression of the TRPV1 channel has a beneficial role in heart disease. Some studies have proven that TRPV1 has an important relationship with pathological myocardial hypertrophy, but the specific mechanism and effect are not clear. In order to help researchers better understand the relationship between TRPV1 and pathological myocardial hypertrophy, this paper aims to summarize the effect of TRPV1 and the related mechanism in the occurrence and development of pathological myocardial hypertrophy from the following three points of view: 1) role of TRPV1 in alleviation of pathological myocardial hypertrophy; 2) role of TRPV1 in aggravation of pathological myocardial hypertrophy; and 3) the point of view of our team of researchers. It is expected that new therapies can provide potential targets for pathological myocardial hypertrophy.

Successful TRPV1 antagonist treatment for cardiac hypertrophy and heart failure in mice

Heart failure is becoming a global epidemic. It exerts a staggering toll on quality of life, and substantial medical and economic impact. In a pre-clinical model of cardiac hypertrophy and heart failure, we were able to overcome loss of heart function by administering the TRPV1 antagonist BCTC (4-(3-Chloro-2-pyridinyl)-N-[4-(1,1-dimethylethyl)phenyl]-1-piperazinecarboxamide). The results presented here identify TRPV1 antagonists as new treatment options for cardiac hypertrophy and heart failure.

Scintigraphic parameters with emphasis on perfusion appraisal in rest 99mTc-sestamibi SPECT in the recovery of myocardial function after thrombolytic therapy in patients with ST elevation myocardial infarction (STEMI)

Introduction: This study was performed to determine the clinical application of rest 99mTc-sestamibi in the assessment of viability and functional improvement of the left ventricle (LV) myocardium in the post-thrombolytic therapy of acute myocardial infarction (AMI). Material and methods: In 37 patients with AMI who received thrombolytic therapy, 2-dimensional (2D) echocardiography, as well as the resting redistribution of 99mTc-sestamibi, was investigated, both within 1 week and 3–5 months after AMI. The predictive capacity of the perfusion percentage for myocardial function recovery was evaluated. Also, the capacities of the possible variables in the prediction of recovery of myocardial function resulting from a change in LV ejection fraction (EF) were evaluated using stepwise multiple regression analysis. Results: Thirty-seven patients (30 men and 7 women; mean age: 58±14 years) with AMI were enrolled in the study. Redistribution was observed in 35 and 50 segments of the initial and follow-up scans, respectively. In addition, 146 segments with reverse redistribution (RR), both in the initial scan (118 segments) and the follow-up scan (86 segments), were also observed. An apparent difference in wall motion scores was seen between the initial and follow-up echocardiographs (p<0.001). Furthermore, using the optimal cut-off point of perfusion percentage in each image set, sensitivity as well as specificity and likelihood ratio (LR) for the improvement of regional wall motion after 3–5 months were defined. Conclusion: These data showed that redistribution and reverse redistribution of 99mTc-sestamibi post thrombolytic therapy can be used as a marker of viability to predict the recovery of segmental wall motion abnormality (stunning), as well as the improvement of segmental perfusion uptake. This study also demonstrates that the resting 99mTc-sestamibi SPECT can be used for an approximate assessment of LV function status and can predict the recovery of jeopardized myocardium function after thrombolytic therapy.

Clinical value of myocardial perfusion scintigraphy as a screening tool in liver transplant candidates

A cardiac evaluation before orthotopic liver transplantation (OLT) is imperative. Previous investigations have demonstrated that mild to moderate reversible perfusion defects on myocardial perfusion scintigraphy (MPS) in general are associated with a low risk for perioperative cardiac events. The objective of this study was to assess any perfusion defects in consecutive patients with chronic liver disease who were undergoing OLT. OLT candidates underwent extensive cardiovascular screening that included, among other methods, MPS. Patients who had no contraindications for surgery and underwent OLT were followed up. The occurrence and risk of complications and mortality were compared in 3 groups of patients: patients with normal MPS results, patients with any reversible defect, and patients with a fixed perfusion defect on MPS. In all, 156 subsequent patients underwent OLT. One or more reversible segmental perfusion defects on MPS were present in 14 patients (<3 segments, n = 12; 3 segments without obstructive coronary artery disease, n = 2). The risk of complications did not differ significantly between patients with normal MPS findings and patients with a reversible perfusion defect (odds ratio = 3.04, 95% confidence interval = 0.65-14.26, P = 0.16), although the study was not sufficiently powered to show a difference. The presence of 1 or more reversible defects on MPS was significantly associated with an increased incidence of all-cause 1-year mortality (hazard ratio = 3.17, 95% confidence interval = 1.02-9.83, P = 0.046). No significant difference in the outcomes of patients with normal MPS findings and patients with a fixed defect on MPS was found; the study was, however, not adequately powered to do so. In conclusion, the results of this small cohort study indicate that patients with mild to moderate reversible perfusion defects on MPS may have inferior survival characteristics in comparison with patients with normal MPS results. A prospective, adequately powered study is required to confirm the results of this study.

[Prognostic value of normal myocardial perfusion scintigraphy with 201Tl in post-acute myocardial infarction]

OBJECTIVE

The purpose of this work has been to determine the prognostic value of normal thallium-201 myocardial perfusion scintigraphy (MPS) in patients who had suffered myocardial infarction in the three months prior to the examination.

MATERIAL AND METHODS

A stress test followed by (201)Tl Gated SPECT was performed. A follow-up was made of 63 patients with normal perfusion scintigraphy. According to the MPS results, the patients were divided into 2 groups. Group I (n=63; 57% males, age 65±12), patients with normal MPS, and group II (n=60; 81% males, age 64±10), patients with abnormal MPS. The appearance of a new infarction or cardiac death occurring during this period (63±3 months) was analyzed. The appearance of events was related with the cardiovascular risk factors, perfusion study and ventricular function.

RESULTS

Five events occurred in group I in 4 patients: 3 new infarctions and 2 cardiac deaths. In group II, there were 18 events in 14 patients: 8 new infarctions and 10 cardiac deaths (p<0,0001). The events were related with age, time from MPS, diabetes, size of perfusion defect and post stress ventricular ejection fraction. Mean survival en group I was 108 months (103-112) and in group II 97 (88-107) (p=0,01).

CONCLUSION

Patients with normal MPS had fewer major events than patients with abnormal MPS. The size of MPS has been related with the appearance of events. A depressed post-stress left ventricular ejection fraction has a poor prognosis.

Quantitative study of cardiac motion estimation and abnormality classification in emission computed tomography

Quantitative description of cardiac motion is desirable to assist in detecting myocardial abnormalities from gated myocardial perfusion (GMP) emission computed tomography (ECT) images. While "optical flow" type of cardiac motion estimation (ME) techniques have been developed in the past, there has been no quantitative evaluation of their performance. Moreover, no investigation has been performed in terms of applying an ME technique to quantify cardiac motion abnormalities. Using the four-dimensional NCAT beating heart phantom with known built-in motion, the current work aimed at addressing the aforementioned two issues. A three-dimensional cardiac ME technique was developed to search for a motion vector field (MVF) that establishes voxel-by-voxel correspondence between two GMP ECT images. The weighted myocardial strain energy served as the constraint in the process to minimize the difference between one intensity image and the MVF warped other. We studied the convergence of the ME technique using different initial estimates and cost functions. The dependence of estimated MVF on the initialization was attributed to the tangential motion that is undetectable while not suppressed by the strain energy constraint. We optimized the strain energy constraint weighting using noise-free phantom images and noisy reconstructed images, the former against the known MVF and the later in the task of regional motion classification. While the results from the above two studies well coincide with each other, we also demonstrated that upon appropriate optimization the ME method has the capability of serving as a computer motion observer in separating simulated noisy reconstructed GMP SPECT images corresponding to hearts with and without regional motion abnormalities.

Long-term prognostic value of early poststress (99m)Tc-tetrofosmin lung uptake during exercise (SPECT) myocardial perfusion imaging

PURPOSE

The aim of this study was to determine the long-term prognostic value of early poststress lung/heart ratio (LHR) of (99m)Tc-tetrofosmin radioactivity.

METHODS

We studied 276 patients (aged 62.2 + or - 8.9 years, 168 men) with stress/rest (99m)Tc-tetrofosmin myocardial gated-SPECT and coronary angiography. To evaluate myocardial ischaemia, we calculated the summed stress score, summed rest score and summed difference score indices. For the eLHR calculation, an anterior image was acquired, 4-6 min after radiotracer injection at stress (eLHR was defined as mean counts per pixel in the lung region of interest divided by the mean counts per pixel in the myocardial region of interest). Cardiovascular death and nonfatal myocardial infarction were considered as hard cardiac events, and late revascularization procedures as soft cardiac events. The Cox proportional hazards model in a stepwise method was used to determine the independent predictors for hard and soft cardiac events.

RESULTS

During the follow-up period hard cardiac events occurred in 28 patients (10.1%) and soft cardiac events in 32 patients (11.6%). Implying multiple Cox regression analysis, eLHR was found to be a significant independent predictor for both soft and hard cardiac events. The hazard ratio (for a 0.1 unit increase) was 4.41 (95% CI 1.52-12.73, p=0.006) for soft cardiac events and 4.22 (95% CI 2.07-8.62, p<0.001) for hard cardiac events. The other significant prognostic factors were use of beta-blockers, the summed stress score and the use of nitrates for soft events, and exercise duration and the summed stress score for hard cardiac events.

CONCLUSION

Early poststress (99m)Tc-tetrofosmin LHR has an independent and powerful value in predicting hard and soft cardiac events.

International variations in the ischemic burden post-acute myocardial infarction: prognostic implications

OBJECTIVES

To determine if there is a variation in the ischemic burden post-acute myocardial infarction (AMI), as assessed by myocardial perfusion imaging (MPI), between different populations in different geographic locations and to see if this variation is associated with different clinical outcomes.

METHODS AND RESULTS

We characterized the MPI findings in 104 stable patients who were hospitalized with AMI at the American University of Beirut Medical Center (AUBMC), a tertiary referral hospital in an East Mediterranean country and we compared them to 126 patients who were enrolled according to a similar protocol in a previous study done at Baylor College of Medicine (BCM), Houston, Texas. There were no differences between the two populations with respect to prevalence of diabetes, hypertension, smoking, the use of thrombolysis, percentage of anterior MIs, Q-wave MIs, and multivessel disease on coronary angiography. However, the quantified ischemic defect size in the BCM population was double that in the AUBMC population (12 +/- 12% vs 6 +/- 8%, P < .01). This was associated with almost doubling of the 1 year event rate of death/myocardial infarction (18.3% vs 10.6%, P = .02) in the BCM population.

CONCLUSION

Our study suggests that the ischemic burden post-AMI, as assessed by MPI, might vary between different populations in different geographic locations. This variation carries important prognostic implications and is associated with different patient outcomes.

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.

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.

An observer study methodology for evaluating detection of motion abnormalities in gated myocardial perfusion SPECT

To address the task of detecting nonischemic motion abnormalities from animated displays of gated myocardial perfusion single photon emission computed tomography data, we performed an observer study to evaluate the difference in detection performance between gating to 8 and 16 frames. Images were created from the NCAT mathematical phantom with a realistic heart simulating hypokinetic motion in the left lateral wall. Realistic noise-free projection data were simulated for both normal and defective hearts to obtain 16 frames for the cardiac cycle. Poisson noise was then simulated for each frame to create 50 realizations of each heart, All datasets were processed in two ways: reconstructed as a 16-frame set, and collapsed to 8 frames and reconstructed. Ten observers viewed the cardiac images animated with a realistic real-time frame rate. Observers trained on 100 images and tested on 100 images, rating their confidence on the presence of a motion defect on a continuous scale. None of the observers showed a significant difference in performance between the two gating methods. The 95% confidence interval on the difference in areas under the ROC curve (Az8 - Az16) was -0.029-0.085. Our test did not find a significant difference in detection performance between 8-frame gating and 16-frame gating. We conclude that, for the task of detecting abnormal motion, increasing the number of gated frames from 8 to 16 offers no apparent advantage.

Prognostic value of quantitative stress myocardial perfusion imaging in unstable angina patients with negative cardiac enzymes and no new ischemic ECG changes

BACKGROUND

Limited data are available on the value of quantitative stress myocardial perfusion imaging (MPI) in patients with unstable angina. In this report we sought to study the long-term prognostic value of quantitative stress MPI in patients hospitalized with unstable angina with no new ischemic electrocardiographic changes and negative cardiac enzymes.

METHODS AND RESULTS

The study population consisted of 136 patients who were hospitalized at the Methodist Hospital, Houston, Tex, with unstable angina and subsequently underwent MPI before discharge. Cox proportional hazards (regression) analysis was performed to identify clinical and MPI predictors of hard cardiac events (death or nonfatal myocardial infarction). During a mean follow-up of 31 +/- 17 months, 20 patients (15%) sustained either cardiac death (n = 12) or nonfatal myocardial infarction (n = 8). The significant multivariate predictors of cardiac events were the total perfusion defect size ( P = .002), the presence of reversible perfusion defects ( P = .01), and the presence of multiple perfusion defects ( P = .03). The perfusion defect size was significantly larger in patients with events than in those without events (21% +/- 20% vs 12% +/- 14%, P = .002). Kaplan-Meier analysis showed that cardiac events were much more likely to develop in patients with defects involving 15% or more of the left ventricle than in those with defects involving less than 15% of the left ventricle ( P = .003).

CONCLUSIONS

In patients hospitalized with unstable angina with no new ischemic electrocardiographic changes and negative cardiac enzymes, quantitative stress MPI provides powerful prognostic information that can be used in the risk stratification of these patients.

Stress echocardiography versus myocardial SPECT for risk stratification of patients with coronary artery disease

PURPOSE OF REVIEW

Diagnostic testing using noninvasive imaging has become an integral part of risk stratification in patients with coronary artery disease. It is important to understand the integral strengths and weaknesses between the different modalities of stress testing and to apply accurately the type of test the clinical scenario demands.

RECENT FINDINGS

There have been tremendous advances made in the field of cardiac imaging. Both myocardial perfusion imaging and stress echocardiographic techniques continue to evolve and play an important role in the assessment of patients with coronary artery disease.

SUMMARY

In this review the authors discuss the relative merits of both stress echocardiography and myocardial single photon emission computed tomographic imaging for diagnosis and risk stratification of patients with coronary artery disease.

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.

Myocardial perfusion scintigraphy: the evidence

This review summarises the evidence for the role of myocardial perfusion scintigraphy (MPS) in patients with known or suspected coronary artery disease. It is the product of a consensus conference organised by the British Cardiac Society, the British Nuclear Cardiology Society and the British Nuclear Medicine Society and is endorsed by the Royal College of Physicians of London and the Royal College of Radiologists. It was used to inform the UK National Institute of Clinical Excellence in their appraisal of MPS in patients with chest pain and myocardial infarction. MPS is a well-established, non-invasive imaging technique with a large body of evidence to support its effectiveness in the diagnosis and management of angina and myocardial infarction. It is more accurate than the exercise ECG in detecting myocardial ischaemia and it is the single most powerful technique for predicting future coronary events. The high diagnostic accuracy of MPS allows reliable risk stratification and guides the selection of patients for further interventions, such as revascularisation. This in turn allows more appropriate utilisation of resources, with the potential for both improved clinical outcomes and greater cost-effectiveness. Evidence from modelling and observational studies supports the enhanced cost-effectiveness associated with MPS use. In patients presenting with stable or acute chest pain, strategies of investigation involving MPS are more cost-effective than those not using the technique. MPS also has particular advantages over alternative techniques in the management of a number of patient subgroups, including women, the elderly and those with diabetes, and its use will have a favourable impact on cost-effectiveness in these groups. MPS is already an integral part of many clinical guidelines for the investigation and management of angina and myocardial infarction. However, the technique is underutilised in the UK, as judged by the inappropriately long waiting times and by comparison with the numbers of revascularisations and coronary angiograms performed. Furthermore, MPS activity levels in this country fall far short of those in comparable European countries, with about half as many scans being undertaken per year. Currently, the number of MPS studies performed annually in the UK is 1,200/million population/year. We estimate the real need to be 4,000/million/year. The current average waiting time is 20 weeks and we recommend that clinically appropriate upper limits of waiting time are 6 weeks for routine studies and 1 week for urgent studies.

[Risk stratification after acute myocardial infarction]

In recent years, the characteristics of patients who suffer acute myocardial infarction without complications during hospitalization have changed. In addition, the range of non-invasive studies available for evaluating left ventricular systolic function, residual myocardial ischemia, and myocardial viability in these patients has improved. Left ventricular systolic function and residual ischemia should be evaluated in all patients before release. The non-invasive technique used (exercise test, echocardiography, nuclear cardiology, magnetic resonance imaging) depends on availability, experience, and results at each institution. Coronary arteriography should be performed in patients with significant ischemia or severe left ventricular systolic dysfunction in non-invasive studies. In these cases coronary angiography must be performed to determine if coronary arteries are suitable for revascularization before performing a test of myocardial viability.

Analysis of referral patterns, predictive accuracy, and impact on patient management of myocardial perfusion imaging in a new nuclear cardiology laboratory

BACKGROUND

Most of the published data on myocardial perfusion imaging (MPI) come from large tertiary-referral medical centers with extensive experience in cardiac imaging as well as a large volume of procedures. Whether the results of MPI remain as reliable in new nuclear cardiology laboratories with smaller volumes of procedures is unknown. The purpose of this study was to analyze the referral patterns, predictive accuracy, and impact of MPI on clinical practice in a newly opened nuclear cardiology laboratory.

METHODS AND RESULTS

We performed a prospective study on all patients referred for MPI at our nuclear cardiology laboratory during its first year of operation. Patients were followed up for 3 months after the MPI study to determine whether they underwent coronary angiography. The study population consisted of 334 patients. Their mean age was 56 +/- 10 years, and 80% were men. Of the patients, 30% were asymptomatic, 29% had angina, and only 6% had recent acute myocardial infarction or unstable angina. Fifty-one patients (fifteen percent) were subsequently referred for coronary angiography. The positive and negative predictive values of MPI were 91% and 86%, respectively. The presence of reversible perfusion defects (P =.02) and the presence of multiple perfusion defects (P =.01) on MPI were the most important determinants of subsequent referral to coronary angiography.

CONCLUSIONS

MPI stress testing retains its high diagnostic accuracy in a new nuclear cardiology laboratory with a relatively small volume of procedures. Furthermore, MPI findings in this population had a strong impact on the clinical practice of the referring physicians in terms of subsequent referral to coronary angiography.

Risk stratification post-myocardial infarction: is early coronary angiography the more effective strategy?

The primary management strategy for the post-myocardial infarction patient continues to be controversial despite published guidelines. In part, this is the consequence of study designs that are not directly applicable to individual patients, but also to the rapidly changing pharmacological and mechanical device armamentarium that rapidly renders clinical trial results obsolete within a few years. This review attempts to highlight those areas where there is consensus as well as to explicate those situations where common clinical practice appears to be in conflict with accepted guidelines.

Risk stratification in patients with remote prior myocardial infarction using rest-stress myocardial perfusion SPECT: prognostic value and impact on referral to early catheterization

BACKGROUND

Little is known about the prognostic value of myocardial perfusion single photon emission computed tomography (SPECT) in patients with remote prior myocardial infarction (MI).

METHODS AND RESULTS

We identified 1413 consecutive patients with remote prior MI who underwent rest-stress myocardial perfusion SPECT. Semiquantitative visual analysis of 20 SPECT segments was used to define the summed stress, rest, and difference scores. The number of non-reversible segments was used as an index of infarct size. During follow-up (>or=1 year), 118 hard events occurred: 64 cardiac deaths (CDs) and 54 recurrent MIs. Annual CD and hard event rates increased significantly as a function of SPECT abnormality. For summed stress scores less than 4, 4 to 8, 9 to 13, and more than 13, the annual CD rates were 0.4%, 0.9%, 1.7%, and 3.5%, respectively (P =.002). Patients with small MI (<4 non-reversible segments) and no or mild ischemia (summed difference score or=4 non-reversible segments) had moderate to high annual CD rates (3.7%-6.6%) regardless of the extent of ischemia. Nuclear testing added incremental prognostic information to pre-scan information. Compared with a strategy in which all patients are referred to catheterization, a strategy that referred only those patients with a risk for CD of greater than 1% by myocardial perfusion SPECT resulted in a 41.6% cost savings.

CONCLUSIONS

Myocardial perfusion SPECT adds incremental value to pre-scan information and is highly predictive and cost-efficient in the risk stratification of patients with remote prior MI. Patients with normal or mildly abnormal scan results or small MI in combination with absent or mild ischemia have a low risk for CD.

Predicting one-year mortality among elderly survivors of hospitalization for an acute myocardial infarction: results from the Cooperative Cardiovascular Project

OBJECTIVES

We sought to develop a model based on information available from the medical record that would accurately stratify elderly patients who survive hospitalization with an acute myocardial infarction (AMI) according to their risk of one-year mortality.

BACKGROUND

Prediction of the risk of mortality among older survivors of an AMI has many uses, yet few studies have determined the prognostic importance of demographic, clinical and functional data that are available on discharge in a population-based sample.

METHODS

In a cohort of patients aged > or = 65 years who survived hospitalization for a confirmed AMI from 1994 to 1995 at acute care, nongovernmental hospitals in the U.S., we developed a parsimonious model to stratify patients by their risk of one-year mortality.

RESULTS

The study sample of 103,164 patients, with a mean age of 76.8 years, had a one-year mortality of 22%. The factors with the strongest association with mortality were older age, urinary incontinence, assisted mobility, presence of heart failure or cardiomegaly any time before discharge, presence of peripheral vascular disease, body mass index <20 kg/m2, renal dysfunction (defined as creatinine >2.5 mg/dl or blood urea nitrogen >40 mg/dl) and left ventricular dysfunction (left ventricular ejection fraction <40%). On the basis of the coefficients in the model, patients were stratified into risk groups ranging from 7% to 49%.

CONCLUSIONS

We demonstrate that a simple risk model can stratify older patients well by their risk of death one year after discharge for AMI.

Prognostic assessment of uncomplicated first myocardial infarction by exercise echocardiography and Tc-99m tetrofosmin gated SPECT

BACKGROUND

We evaluate the prognostic value of stress echo and gated single photon emission computed tomography (SPECT) after a first uncomplicated acute myocardial infarction.

METHODS AND RESULTS

We used predischarge maximal subjective exercise echocardiography and gated SPECT with technetium 99m tetrofosmin to prospectively study 103 patients younger than 70 years with a first acute myocardial infarction. During a 12-month follow-up period, 2 patients died, 9 had heart failure, and 29 had ischemic complications (4 reinfarction and 25 angina). Predictive variables for heart failure in multivariate analysis were ejection fraction evaluated by echocardiography (odds ratio [OR] 8.5, P =.016) or by gated SPECT (OR 10.7, P =.009). Predictive variables for ischemic complications in multivariate analysis were less than 5 metabolic equivalents (METS) in exercise test (OR 5.2, P =.007) and greater than 15% ischemic extent in the polar map (OR 3.6, P =.04) of SPECT.

CONCLUSIONS

Exercise echocardiography and Tc-99m tetrofosmin gated SPECT were predictive for heart failure, but exercise SPECT was the only test with predictive power for ischemic complications.

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

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

Risk stratification after acute myocardial infarction in the reperfusion era

Historically, risk stratification for survivors of acute myocardial infarction (AMI) has centered on 3 principles: assessment of left ventricular function, detection of residual myocardial ischemia, and estimation of the risk for sudden cardiac death. Although these factors still have important prognostic implications for these patients, our ability to predict adverse cardiac events has significantly improved over the last several years. Recent studies have identified powerful predictors of adverse cardiac events available from the patient history, physical examination, initial electrocardiogram, and blood testing early in the evaluation of patients with AMI. Numerous studies performed in patients receiving early reperfusion therapy with either thrombolysis or primary angioplasty have emphasized the importance of a patent infarct related artery for long-term survival. The predictive value of a variety of noninvasive and invasive tests to predict myocardial electrical instability have been under active investigation in patients receiving early reperfusion therapy. The current understanding of the clinically important predictors of clinical outcomes in survivors of AMI is reviewed in this article.

Can dobutamine stress echocardiography predict cardiac events in nonrevascularized diabetic patients following acute myocardial infarction?

STUDY OBJECTIVE

To determine whether the prognostic value of dobutamine stress echocardiography (DSE) performed early after acute myocardial infarction (AMI) is as high in diabetic patients as in nondiabetic patients.

DESIGN

Inception cohort study.

SETTING

Tertiary cardiac referral center.

PATIENTS AND INTERVENTIONS

Three hundred thirty-eight patients (116 diabetic and 222 nondiabetic) who underwent DSE after AMI were followed up for cardiac events.

MEASUREMENTS AND RESULTS

Outcome events were as follows: "hard" events consisted of cardiac death and nonfatal reinfarction, while "all events" included hard events and unstable angina. The mean follow-up duration was 21 +/- 9 months. DSE results were positive in 69 diabetic patients (59.5%) and 129 nondiabetic patients (58.1%; p = 0.817). During the follow-up period, there were 25 cardiac deaths, 16 cases of nonfatal reinfarction, and 55 cases of unstable angina. The Kaplan-Meier life table showed that a positive DSE result was associated with a lower event-free survival rate in nondiabetic but not in diabetic patients in terms of hard and all events. By multivariate analysis, a positive DSE result was the strongest independent predictor of future cardiac events in nondiabetic patients. However, in diabetics, a shorter dobutamine time, rather than a positive DSE result, independently predicted cardiac events.

CONCLUSIONS

Our preliminary data suggest that different DSE variables should be considered when assessing the likelihood of future events in diabetic and nondiabetic patients after AMI. The observation of shorter dobutamine time, instead of DSE positivity, has a higher prognostic value in diabetics. In diabetic patients, the only significant role of DSE positivity is for predicting future unstable angina; however, its predictive value is not as good as in nondiabetic patients.

Diagnostic and Prognostic Use of Stress Echocardiography and Radionuclide Scintigraphy

Stress echocardiography and radionuclide scintigraphy are effective diagnostic and prognostic techniques in patients with known or suspected coronary artery disease (CAD), myocardial infarction (MI), chronic left ventricular dysfunction (LVD), and those undergoing noncardiac surgery. Both are sensitive and specific for the detection and extent of CAD. Negative tests confer a high negative predictive value for cardiac events irrespective of clinical risk. Positive studies confer a high positive predictive value for ischemic events in patients with intermediate to high clinical risk. Both provide incremental diagnostic and prognostic information relative to clinical, resting echocardiographic, and angiographic data. Meta-analysis studies have shown that the diagnostic and prognostic information provided by stress echocardiography is comparable with radionuclide scintigraphic stress tests. Stress echocardiography may be more specific for the detection and extent of CAD, whereas radionuclide scintigraphy may be more sensitive for single-vessel disease. Sensitivities are similar for the detection and extent of disease in patients with multivessel CAD.

Stress myocardial perfusion imaging versus echocardiography for the diagnosis and risk stratification of patients with known or suspected coronary artery disease

Stress perfusion imaging and stress echocardiography (ECHO) are both very useful for assessment of diagnosis and risk stratification of patients with coronary artery disease (CAD). Both techniques have been well validated during exercise and inotropic stress, but coronary vasodilation stress is better used in combination with perfusion imaging. The overall sensitivity for detection of CAD is slightly higher by single photon emission computed tomography (SPECT) than by two-dimensional (2D) ECHO during all stress modalities, whereas the specificity is slightly higher by ECHO, although the differences in general are not statistically significant. SPECT, however, appears to be superior to ECHO in the diagnosis of isolated circumflex stenosis, as well as for the correct identification of multivessel CAD. A substantially greater amount of information is available regarding risk stratification with SPECT than with 2D ECHO. Although the data suggest that both techniques are very useful for risk stratification of patients with stable CAD, after myocardial infarction, and for preoperative risk stratification, the risk for cardiac events is lower in the presence of a normal stress SPECT study than of a normal stress ECHO.

The role of nuclear cardiology in clinical decision making

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

Effects of medical therapy on outcome assessment using exercise thallium-201 single photon emission computed tomography imaging: evidence of a protective effect of beta-blocking antianginal medications

OBJECTIVES

The purpose of this study was to determine whether antianginal medications modify the prognostic significance of exercise single photon emission computed tomography (SPECT) ischemia.

BACKGROUND

Antianginal medications (especially beta-adrenergic blocking agents) limit exercise SPECT ischemia, but it is not known whether such medications also modify the prognostic effect of exercise SPECT ischemia.

METHODS

We included 352 patients with coronary heart disease, who had exercise Tl-201 SPECT and coronary angiography, and who were initially treated medically. Survival Cox models were applied in patients for whom classes of antianginal medications taken at exercise SPECT were the same as those prescribed for follow-up (GI; n = 136), and in patients for whom new classes of antianginal medications, including beta-blockers (GII; n = 79) or not including beta-blockers (GIII; n = 113), were added for follow-up.

RESULTS

During a mean 5.3+/-1.6 years of follow-up, 45 patients had cardiac death or myocardial infarction. Variables reflecting necrosis (irreversible defect extent, left ventricular ejection fraction) and those from coronary angiography provided equivalent prognostic information in the three groups. In contrast, the SPECT variable reflecting ischemia (reversible defect extent), which provided comparable prognostic information in GI (p = 0.005) and GIII (p = 0.004), lost its prognostic significance (p = 0.54) in GII, and was associated with a lower relative risk in GII than in GI or GIII (both p < 0.05).

CONCLUSIONS

In patients with coronary heart disease, the introduction of antianginal medications, when including beta-blockers, appears to have a favorable effect on the deleterious prognostic effect of exercise ischemia.

Quantification of SPECT myocardial perfusion images: methodology and validation of the Yale-CQ method

BACKGROUND

Quantification of single photon emission computed tomography (SPECT) images is important for reproducible and accurate image interpretation. In addition, SPECT quantification provides important prognostic information. The purpose of this study was to validate the Yale circumferential quantification (Yale-CQ) method in phantom studies.

METHODS

Myocardial perfusion defects of varying extent and severities were simulated in a cardiac phantom with fillable defect inserts. Forty-five different phantom configurations simulated 45 different myocardial perfusion defect sizes, ranging from 1.6% to 32% of the cardiac phantom volume. Automatic processing was compared with manual processing in the phantom SPECT studies.

RESULTS

The automatic Yale-CQ algorithm performed well in all phantom studies. Compared with manual processing, the mean absolute error for automatically determined center of short axis slices was 0.27 pixel in the x direction, 0.45 pixel in the y direction, and 0.15 pixel in radius. Quantification of phantom defects with the Yale-CQ method correlated well with actual defect sizes (R = 0.99), but there was a systematic underestimation (mean error = -7.9%). With derived correction factors the overall correlation between 45 phantom defects and actual defect sizes was excellent, and the estimation error was significantly improved (R = 0.98, mean error = -0.82% for manual method and -0.95% for automatic method).

CONCLUSION

The automatic processing algorithm performs well for the phantom studies. Myocardial perfusion abnormalities can be quantified accurately by use of the Yale-CQ method. Quantified SPECT defect size can be expressed as a percentage of the left ventricle.

Prediction of functional recovery and prognosis in patients with acute myocardial infarction by 123I-BMIPP and 201Tl myocardial single photon emission computed tomography: a multicenter trial

123I-BMIPP [15-(p-iodophenyl)-3-(R,S)-methylpentadecanoic acid] was developed for metabolic imaging with SPECT. A multicenter collaborative study was conducted on a large patient series to determine whether 123I-BMIPP and 201Tl myocardial SPECT are of use in predicting the prognosis and ventricular function after acute myocardial infarction (AMI). Patients with uncomplicated first AMI underwent resting 123I-BMIPP and 201Tl myocardial SPECT in the subacute phase after the onset of AMI. Of these, 167 patients who had been followed up for an average of 22 months were retrospectively reviewed to predict serious cardiac events and recurrent ischemia. In addition, the association between changes in radionuclide parameters and recurrent ischemia was investigated in Subgroup A (58 patients) who had repeated SPECT in the chronic phase. Furthermore, prediction of the ejection fraction (EF) was investigated in Subgroup B (94 patients) and Subgroup C (76 patients) in whom left ventriculography was performed at the time of discharge and 90 days or more after the onset, respectively. The prognosis was generally favorable, with 4 cases of cardiac death (2%), 3 of heart failure (2%), 4 of nonfatal reMI (2%), and 25 of recurrent ischemia (15%). The results of Cox multivariate regression analysis revealed a high probability of serious cardiac events in patients who were elderly (p = 0.04), who had 90% or more residual stenosis of the infarct-related artery (p = 0.09), and who had a high BMIPP defect score (p = 0.17). There was a high probability of recurrent ischemia in elderly patients (p = 0.10) who had multi-vessel disease (p = 0.03), but no association was found with radionuclide parameters in the subacute phase. In Subgroup A, however, the probability of recurrent ischemia tended to be high in patients with a large mismatch scorebetween 123I-BMIPP and 201Tl in the subacute to chronic phase. An important observation was that the extent of BMIPP defect was more strongly correlated with EF at the time of discharge and 90 days or more after the onset than the extent of Tl defect (r = -0.60 vs. r = -0.47, and r = -0.53 vs. r = -0.43, respectively). In addition, multiple regression analysis showed that parameters related to the BMIPP defect were also better predictive factors of EF both at the time of discharge and 90 days or more after the onset. In conclusion, resting 123I-BMIPP and 201Tl myocardial SPECT performed in the subacute phase of AMI were shown to be useful in predicting prognosis and ventricular function for patient management.

Prognostic value of myocardial viability and ischemia detected by dobutamine stress echocardiography early after acute myocardial infarction treated with thrombolysis

OBJECTIVES

The aim of the study was to assess the prognostic value of myocardial viability and ischemia detected by dobutamine stress echocardiography (DSE) in patients with acute myocardial infarction (AMI) treated with thrombolysis.

BACKGROUND

DSE can detect myocardial viability and ischemia early after AMI, but the prognostic importance of viability and ischemia in these patients has yet to be assessed.

METHODS

DSE was performed in 152 patients at a mean of 9 +/- 5 days after a first AMI treated with thrombolysis to evaluate myocardial viability and ischemia. The patients were followed up for 15 +/- 19 months.

RESULTS

On the basis of DSE results three groups of patients were identified: group 1 (95 patients, 62.5%) with myocardial viability and ischemia, group 2 with myocardial viability without ischemia (32 patients, 21%) and group 3 (25 patients, 16.5%) with no myocardial viability. During follow-up 10 patients (6.5%) had hard events, 53 (35%) developed unstable angina and 67 (44%) underwent myocardial revascularization. The rate of hard events was 10% in group 1 and 0% in group 2 and 3 patients (p < 0.05 group 1 versus group 2); group 1 patients with viability and ischemia showed a significantly higher rate of recurrence of unstable angina and myocardial revascularization procedures (40% and 60%) compared to group 2 (22% and 16%) and group 3 patients (20% and 20%). Using the Cox multivariate stepwise model, only the extent of ischemic myocardium (hazard ratio (HR) = 21.7, p = 0.02) and angina during DSE (HR = 4.45, p = 0.03) were significant predictors of hard events; an ischemic response to DSE (HR = 2.92, p = 0.001) was the most important predictor of spontaneous events, followed by ST-segment depression during DSE (HR = 1.71, p = 0.04), angina during DSE (HR = 1.53, p = 0.19) and age (HR = 0.96, p = 0.05).

CONCLUSIONS

In patients with a first AMI treated with thrombolysis the presence and extent of myocardial ischemia during DSE is the most important predictor of both hard and spontaneous cardiac events, whereas myocardial viability does not have an independent prognostic value.

Combined assessment of left ventricular function and rest-redistribution regional myocardial thallium-201 activity for prognostic evaluation of patients with chronic coronary artery disease and left ventricular dysfunction

BACKGROUND

This study evaluated the prognostic value of combined assessment of left ventricular (LV) function and regional myocardial thallium activity in patients with nonrecent myocardial infarction and LV dysfunction.

METHODS AND RESULTS

Eighty-two patients with previous myocardial infarction (>8 weeks) and echocardiographic evidence of LV dysfunction underwent thallium-201 rest-redistribution tomography and cardiac catheterization. During the follow-up period (mean 25 months) there were 18 cardiac events (14 deaths and 4 nonfatal myocardial infarctions). Multivariate Cox regression analysis on clinical, angiographic, and thallium variables showed that the number of echocardiographic dysfunctional segments with preserved thallium uptake (> or =50% of peak activity; chi-square 11.03; p<0.005) and age (chi-square 8.12, p<0.01) were predictive of poor outcome. At incremental analysis, combined echocardiographic and thallium data provided significant additional information to clinical, thallium, and LV functional data, increasing global chi-square value from 22.4 to 31.5 (p< 0.01). Similarly, combined data gave additional information after considering clinical, echocardiographic, and LV functional data, increasing global chi-square from 17.8 to 22.3 (p <0.05). Differently, the number of diseased vessels at coronary angiography did not add further prognostic information.

CONCLUSIONS

In patients with previous myocardial infarction and chronic LV dysfunction, the combination of echocardiographic and thallium rest-redistribution imaging data gives prognostic information incremental to those of clinical and LV functional data and to those of each technique considered separately.

Risk assessment using single-photon emission computed tomographic technetium-99m sestamibi imaging

OBJECTIVES

This review summarizes the results of single-photon emission computed tomographic (SPECT) technetium-99m (Tc-99m) tracer imaging in patients with stable symptoms, patients with acute coronary syndromes, patients undergoing major non-cardiac surgery and patients with chest pain in the emergency department.

BACKGROUND

Previous studies have examined the prognostic value of stress thallium imaging in several subsets of patients with ischemic heart disease. At present, >50% of myocardial perfusion studies are performed with technetium-labeled tracers in the United States. Furthermore, there is a shift from diagnostic to the prognostic utility of stress testing. There are important differences between technetium-labeled tracers and thallium-201. It is therefore important to review the prognostic value of technetium-labeled tracers.

METHODS

We analyzed published reports in English on risk assessment using Tc-99m perfusion tracers. Results. The largest experience is in patients with stable symptoms, comprising >12,000 patients in 14 studies. In these patients, normal stress SPECT sestamibi images were associated with an average annual hard event rate of 0.6% (death or nonfatal myocardial infarction [MI]). In contrast, patients with abnormal images had a 12-fold higher event rate (7.4% annually). Both fixed and reversible defects are prognostically important, and quantitative analysis shows increased risk in relation to the severity of the abnormality. These results are similar to those obtained with thallium-201.

CONCLUSIONS

Patients with stable chest pain syndromes and normal stress SPECT sestamibi images have a very low risk of death or nonfatal MI. It is highly unlikely that coronary revascularization can improve survival in such patients. Patients with abnormal images have an intermediate to high risk for future cardiac events, depending on the degree of the abnormality. Further prospective studies comparing aggressive medical therapy with coronary revascularization in these patients are warranted.