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

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.

Prognostic performance of quantitative PET tools for stratification of patients with ischemic cardiomyopathy undergoing myocardial viability assessment

OBJECTIVES

This study was performed to determine the prognostic performance of quantitative PET tools in the stratification of patients with ischemic cardiomyopathy undergoing myocardial viability assessment.

METHODS

We applied four different quantitative tools to 104 consecutive patients with coronary artery disease and previous myocardial infarction who had undergone rest Rb/gated F-fluorodeoxyglucose (FDG) PET, to assess myocardial viability for potential revascularization. One of these tools was based on the FDG study alone and the other three tools assessed the extent of match/mismatch defects using FDG in comparison with a perfusion reference database. The four quantitative tools used in this research to define viability were (i) FDG alone, which calculates the percentage of left ventricular myocardium (LVM) that is above the 50% of the maximum LVM FDG counts, (ii) low flow match/mismatch, which determines the area with a 5% increase in normalized FDG counts in relation to defined resting perfusion defects as compared with a reference database, (iii) all regions match/mismatch, which computes the area with a 10% increase in normalized FDG counts in relation to the left ventricle resting perfusion distribution, and (iv) percentage max FDG match/mismatch, which defines the area with FDG uptake greater than 60% of the maximum LVM FDG counts within defined perfusion defects as determined by the reference database. The primary endpoint for this analysis was cardiac death.

RESULTS

During the follow-up period (22+/-14 months), 19 patients (18%) died; in 17 of these the cause of death was cardiac. Using univariate analysis, none of the methods were predictive of cardiac death. Receiver operating characteristic analysis defined the optimal thresholds for the extent of myocardial viability for the four tools in the prediction of cardiac death: FDG alone=20%, low flow match/mismatch=15%, all regions match/mismatch=35%, and percentage max FDG match/mismatch=20%. A censored survival analysis using a Kaplan-Meier method showed a statistically significant difference between patients with cardiac death and those with no cardiac death using only the low flow match/mismatch (hazard ratio=0.29, P=0.01) and percentage max FDG match/mismatch criteria (hazard ratio=0.23, P=0.005) tools.

CONCLUSION

The low flow match/mismatch and percentage max FDG match/mismatch quantitative PET tools are useful for prognostic stratification of patients with ischemic cardiomyopathy undergoing myocardial viability assessment.

CT of Cardiac Function

Multidetector computed tomography (MDCT) can play a role in diagnosis of coronary artery disease and in the assessment of left ventricle (LV) and right ventricle global function, with initial good correlation results with standard modalities. With the latest scanners, regional LV contractility with both qualitative and quantitative assessment has become possible. MDCT function evaluation by specific postprocessing software can be performed considering simultaneously different parameters plus the subjective visual perception of anomalies on 2-dimensional and 3-dimensional cine-loop models. MDCT's ability to make high-resolution 3-dimensional reconstructions throughout the cardiac cycle allows this imaging modality to evaluate both coronary and LV anatomy and morphology, and also LV functional parameters. The ability to provide functional information of the right ventricle represents another important application of MDCT both in patients with acute pulmonary embolism and with congenital cardiovascular disease. Initial results on accuracy are promising and the clinical applicability of MDCT should rapidly increase.

Incremental prognostic value of combined perfusion and function assessment during myocardial gated SPECT in patients aged 75 years or older

BACKGROUND

Perfusion and functional data obtained during gated single photon emission computed tomography (SPECT) have proven prognostic value in the middle-aged patient population. The aim of this study was to investigate whether perfusion and functional cardiac gated SPECT data have prognostic value in patients aged 75 years or older.

METHODS AND RESULTS

We studied clinical and gated SPECT predictors of cardiac and all-cause death in 294 patients aged 75 years or older with known or suspected coronary artery disease who were referred for tetrofosmin cardiac gated SPECT imaging. Summed perfusion scores were calculated in a 17-segment model by use of commercially available software (4D-MSPECT). Left ventricular functional data were calculated by use of QGS gated SPECT software. The median age of the study population was 78 years (range, 75-91 years). There were 160 men (54%) and 134 women (46%). During a median follow-up of 25.9 months (range, 1.8-36 months), 47 patients (16%) died (27 cardiac deaths). In a multivariate Cox proportional hazards regression analysis, the summed rest score (chi2 gain = 8.0, P = .009), transient ischemic dilatation index (chi2 gain = 6.3, P = .012), and resting left ventricular ejection fraction (chi2 gain = 7.0, P = .030) were independent predictors of all-cause death. The summed rest score (chi2 gain = 8.2, P = .004) and resting end-systolic volume (chi2 gain = 13.7, P = .005) were independent predictors of cardiac death.

CONCLUSIONS

This study showed that gated SPECT left ventricular functional data assessed during myocardial gated SPECT provide independent and incremental information above clinical and perfusion SPECT data for the prediction of cardiac and all-cause death in patients aged 75 years or older referred for myocardial SPECT imaging.

[Myocardial perfusion (SPECT) in patients with non-Q-wave myocardial infarction]

BACKGROUND AND OBJECTIVE

The denomination non-Q-wave myocardial infarction ranges from small infarcts without scintigraphic abnormalities to severe and extensive necrosis with scintigraphic criteria of transmurality. The aim of the present study was to evaluate the severity and localization of necrosis in patients with non-Q-wave myocardial infarct, by myocardial perfusion single photon emission computed tomography (SPECT).

PATIENTS AND METHOD

We evaluated 206 patients with non-Q-wave myocardial infarct consecutively studied by myocardial perfusion 99mTc-tetrofosmin SPECT. Severity and localization of perfusion defects at stress and rest were analyzed.

RESULTS

Rest SPECT was normal in 53 patients (26%) and in 41 patients (20%) at least one segment with scintigraphic criteria of transmurality (uptake absence) was observed. Perfusion defects were more frequently localized in inferior and lateral regions. Stress-rest reversibility in peri-infarct regions was observed in 68.9% of patients, and reversibility at a distance was observed in 30% of patients.

CONCLUSIONS

Myocardial perfusion SPECT is a useful technique for the evaluation of the localization, extension and transmurality of non-Q-wave myocardial infarction, and the residual peri-infarction ischemia and ischemia at a distance of the necrosis.

Incremental prognostic value of left ventricular function by myocardial ECG-gated FDG PET imaging in patients with ischemic cardiomyopathy

BACKGROUND

The purpose of this study was to determine the independent value of left ventricular (LV) functional parameters derived from gated fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) to predict prognosis in patients with ischemic cardiomyopathy undergoing myocardial viability assessment.

METHODS AND RESULTS

We studied 90 consecutive patients with coronary artery disease and low LV ejection fraction (26% +/- 7%) undergoing gated FDG PET to assess myocardial viability for potential revascularization. The primary endpoint for this analysis was the occurrence of cardiac death, myocardial infarction, or worsening heart failure (HF) to New York Heart Association class IV. During follow-up (22 +/- 14 months), 21 patients had an event (17 died, 4 had myocardial infarctions, and 4 had worsening HF). On Cox regression analysis, the event-free survival rate at 2 years was lower for patients with an end-diastolic volume (EDV) of 260 mL or greater (relative risk, 2.7; P = .014), end-systolic volume (ESV) of 200 mL or greater (relative risk, 2.5; P = .021), and LV mass of 143 g or greater (relative risk, 1.6; P = .009). In a risk-adjusted model, EDV (chi 2 = 68, P < .0001) and ESV (chi 2 = 75, P = .035) added a significant amount in the estimation of events over the perfusion-FDG mismatch pattern (chi 2 = 40, P < .001). In a stratified Cox model, patients with PET mismatch, LV ejection fraction lower than 25%, and EDV of 260 mL or greater had the lowest survival rate (P = .006). These patients showed an apparent survival benefit with revascularization but without an improvement in HF symptoms.

CONCLUSION

LV functional parameters determined by gated FDG PET have incremental prognostic value over viability information in patients with ischemic cardiomyopathy. Our data suggest that patients with residual viability and advanced cardiac remodeling are at high clinical risk. In these patients the apparent survival benefit of revascularization may not be associated with a measurable improvement in HF symptoms.

Prognostic validation of a 17-segment score derived from a 20-segment score for myocardial perfusion SPECT interpretation

BACKGROUND

Recently, a 17-segment model of the left ventricle has been recommended as an optimally weighted approach for interpreting myocardial perfusion single photon emission computed tomography (SPECT). Methods to convert databases from previous 20- to new 17-segment data and criteria for abnormality for the 17-segment scores are needed.

METHODS AND RESULTS

Initially, for derivation of the conversion algorithm, 65 patients were studied (algorithm population) (pilot group, n = 28; validation group, n = 37). Three conversion algorithms were derived: algorithm 1, which used mid, distal, and apical scores; algorithm 2, which used distal and apical scores alone; and algorithm 3, which used maximal scores of the distal septal, lateral, and apical segments in the 20-segment model for 3 corresponding segments of the 17-segment model. The prognosis population comprised 16,020 consecutive patients (mean age, 65 +/- 12 years; 41% women) who had exercise or vasodilator stress technetium 99m sestamibi myocardial perfusion SPECT and were followed up for 2.1 +/- 0.8 years. In this population, 17-segment scores were derived from 20-segment scores by use of algorithm 2, which demonstrated the best agreement with expert 17-segment reading in the algorithm population. The prognostic value of the 20- and 17-segment scores was compared by converting the respective summed scores into percent myocardium abnormal. Conversion algorithm 2 was found to be highly concordant with expert visual analysis by the 17-segment model (r = 0.982; kappa = 0.866) in the algorithm population. In the prognosis population, 456 cardiac deaths occurred during follow-up. When the conversion algorithm was applied, extent and severity of perfusion defects were nearly identical by 20- and derived 17-segment scores. The receiver operating characteristic curve areas by 20- and 17-segment perfusion scores were identical for predicting cardiac death (both 0.77 +/- 0.02, P = not significant). The optimal prognostic cutoff value for either 20- or derived 17-segment models was confirmed to be 5% myocardium abnormal, corresponding to a summed stress score greater than 3. Of note, the 17-segment model demonstrated a trend toward fewer mildly abnormal scans and more normal and severely abnormal scans.

CONCLUSION

An algorithm for conversion of 20-segment perfusion scores to 17-segment scores has been developed that is highly concordant with expert visual analysis by the 17-segment model and provides nearly identical prognostic information. This conversion model may provide a mechanism for comparison of studies analyzed by the 17-segment system with previous studies analyzed by the 20-segment approach.

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.

[Evolution of systolic function and myocardial perfusion, evaluated by gated-SPECT, in the first year after acute myocardial infarction]

INTRODUCTION AND OBJECTIVES

Systolic function and myocardial perfusion are evaluated before hospital discharge and can change during follow-up. The purpose of this study was to evaluate these parameters by gated-SPECT in the first year after acute myocardial infarction.

PATIENTS AND METHOD

We studied 74 consecutive patients with a first uncomplicated acute myocardial infarction (49 infero-lateral and 25 anterior) by stress-rest 99mTc-tetrofosmin and rest-gated-SPECT before hospital discharge (6-8 days after admission) and one year after myocardial infarction.

RESULTS

The ejection fraction (EF) increased > 5% in 51% of infero-lateral infarcts and 28% of non-revascularized anterior infarcts. EF increased significantly (48.4 8% to 54.6 8.7%; p < 0.0001, mean difference: 6.2; 95% IC, 2.8-9.5) and systolic volume decreased (51.3 19.2 ml to 44.3 19.4 ml; p = 0.001; mean diff.: 7.67; 95% IC, 1.5-13.8) in infero-lateral infarctions. The rest perfusion index in the necrotic region improved (2.3 0.57 to 2.17 0.58; p = 0.004; mean diff.: 0.18; 95% IC, 0.003-0.36) in infero-lateral infarcts and the ischemia index remained unchanged between the first and second studies.

CONCLUSIONS

Left ventricular systolic function can change during the first year of evolution, a significant improvement being seen in infero-lateral infarctions. The ejection fraction increased > 5% in half of these patients, as opposed to only a quarter of anterior infarctions. This improvement was associated to increased myocardial perfusion at rest.

[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.

Validation of quantitative gated single photon emission computed tomography and an automated scoring system for the assessment of regional left ventricular systolic function

Despite its ability to quantify regional perfusion and function, there is no established method for quantification of regional perfusion and function by myocardial gated single photon emission computed tomography (SPECT). The aim of this study was to establish a quantitative index for regional perfusion and systolic function assessment using gated SPECT. Myocardial SPECT was performed at rest using (99m)Tc sestamibi with 8-frame gating in 62 consecutive patients. In addition to computation of left ventricular ejection fraction (LVEF), a new computerized method for quantifying, displaying and automatically grading regional data was developed. Regional function was quantified as wall motion, regional EF, and imaged based, count based, and normalized per cent wall thickenings (%WTs). Regional perfusion was assessed as a relative per cent peak count. Data were displayed on a 25-segmented polar map and automatically graded with a 5-point scale, and then summed scores were calculated. These quantitative parameters were compared to data from radionuclide ventriculography (RNV) and contrast left ventriculography. Gated SPECT had high reproducibilities for calculating global and regional ejection fractions and %WT indices (r=0.811-0.984, P<0.0001), but measurement of wall motion was less reproducible (r=0.555, SEE=7.9, P<0.011). LVEF estimated by gated SPECT and summed perfusion scores correlated closely (P<0.0001) with angiographic LVEF. Among the summed function indices that correlated closely with LVEF, normalized %WT had the closest correlations with LVEF estimated by RNV (r=0.657, P<0.0001) and by gated SPECT (r=0.778, P<0.0001). Assessment by visual reviewing of cine-mode playback or by normalized %WT had greater overall sensitivity, specificity, and positive and negative predictive values for detecting impaired regional function among the functional parameters: 71%, 79%, 63% and 84% for cine format analysis, and 78%, 73%, 59% and 87% for normalized %WT, respectively. Thus, besides LVEF, quantitative gated SPECT can provide reproducible and reliable quantitative data on regional perfusion and function. Automated summed scores obtained by gated SPECT can reflect integrated abnormalities of regional perfusion and function of the left ventricle. Both visual analyses by cine-mode display and a functional map of normalized wall thickening have greater diagnostic values for detecting regional function deficit related to coronary artery disease.