The impact of viability assessment using myocardial perfusion imaging on patient management and outcome

Efficacy of revascularization in CTO patients based on hibernating myocardium therapy

BACKGROUND

The effectiveness of percutaneous coronary intervention (PCI) for chronic total occlusion (CTO) is still uncertain, especially for patients with ischemic left ventricular dysfunction. This study aimed to assess hibernating myocardium (HM), as determined by single-photon emission computed tomography (SPECT) and 18F-FDG positron emission tomography (PET), and to compare the benefits of PCI and optimal medical therapy (OMT).

METHODS

A retrospective study collected data from 332 patients with CTO and ischemic left ventricular dysfunction. The study compared patients who underwent PCI or OMT via propensity score matching (PSM) analysis which was performed with a 1:2 matching protocol using the nearest neighbour matching algorithm. The primary endpoint of the study was the occurrence of major adverse cardiac events (MACE), defined as a composite of cardiac death, readmission for worsening heart failure (WHF), revascularization and myocardial infarction (MI).

RESULTS

After PSM, there were a total of 246 individuals in the PCI and OMT groups. Following Cox regression, hibernating myocardium/total perfusion defect (HM/TPD) was identified as an independent risk factor (hazard ratio (HR): 1.03, 95% confidence interval (CI): 1.008-1.052, p = .007). The cut-off value of HM/TPD was 38%. The results of the subgroup analysis suggest that for patients with HM/TPD >38%, the OMT group had a greater risk of MACE (p = .035). A sensitivity analysis restricting patients with single-vessel CTO lesions, HM/TPD remained an independent predictor (HR 1.025, 95% CI 1.008-1.043, p = .005).

CONCLUSION

HM/TPD is an independent predictor of MACE, and for patients with HM/TPD > 38%, CTO-PCI had a lower risk of MACE compared with OMT. However, further validation is still needed through large-scale studies.

Hot spot imaging in cardiovascular diseases: an information statement from SNMMI, ASNC, and EANM

This information statement from the Society of Nuclear Medicine and Molecular Imaging, American Society of Nuclear Cardiology, and European Association of Nuclear Medicine describes the performance, interpretation, and reporting of hot spot imaging in nuclear cardiology. The field of nuclear cardiology has historically focused on cold spot imaging for the interpretation of myocardial ischemia and infarction. Hot spot imaging has been an important part of nuclear medicine, particularly for oncology or infection indications, and the use of hot spot imaging in nuclear cardiology continues to expand. This document focuses on image acquisition and processing, methods of quantification, indications, protocols, and reporting of hot spot imaging. Indications discussed include myocardial viability, myocardial inflammation, device or valve infection, large vessel vasculitis, valve calcification and vulnerable plaques, and cardiac amyloidosis. This document contextualizes the foundations of image quantification and highlights reporting in each indication for the cardiac nuclear imager.

The prognostic value of left ventricular mechanical dyssynchrony using gated myocardial perfusion imaging in patients with end-stage renal disease

BACKGROUND

Prior studies show that left ventricular mechanical dyssynchrony (LVD), measured by gated SPECT myocardial perfusion imaging (MPI), identifies patients with end-stage renal disease (ESRD) at higher risk for all-cause mortality but these were in small number of patients. We sought to assess the interaction between LVD and LV perfusion pattern in risk-stratification of a large sample size of patients with ESRD.

METHODS

From the renal transplantation database maintained at the University of Alabama at Birmingham, we identified consecutive patients with ESRD who had gated SPECT MPI between 2003 and 2007. MPIs were reprocessed to derive LV ejection fraction (EF), perfusion defect size, and LVD [phase bandwidth (BW) and phase standard deviation (SD)]. The primary end-point was all-cause mortality, which was prospectively collected and verified against the social security death index database.

RESULTS

There were 828 patients aged 52.6 ± 0.36 years (45% were women and 60% had diabetes mellitus). The LVEF was 54.8 ± 0.4% and the perfusion pattern was abnormal in 334 patients (41%). During a follow-up period of 61 ± 0.9 months, 230 patients (28%) received renal transplants and 290 patients (35%) died. The phase BW (73.1 ± 2.6° vs 66.3 ± 1.8°, P = .02) and SD (25.2 ± 0.8° vs 23.4 ± 0.5°, P = .06) were greater in patients who died than those who survived indicating greater dyssynchrony. Patients with phase BW >56° or SD ≥21° (median values) had worse 5-year survival (64% vs 72%, and 66% vs 71%, log-rank P = .005 and P = .07, respectively). After adjusting for demographics, co-morbidities, LVEF, and perfusion pattern, phase BW was associated with worse outcome (hazard ratio 1.289 95% CI 1.010-1.644, P = .04).

CONCLUSIONS

LVD by phase analysis of gated SPECT MPI provides prognostic value in ESRD beyond myocardial perfusion and EF.

Identification of therapeutic benefit from revascularization in patients with left ventricular systolic dysfunction: inducible ischemia versus hibernating myocardium

BACKGROUND

Although the recent surgical treatment of ischemic heart failure substudy reported that revascularization of viable myocardium did not improve survival, these results were limited by the viability imaging technique used and the lack of inducible ischemia information. We examined the relative impact of stress-rest rubidium-82/F-18 fluorodeoxyglucose positron emission tomography identified ischemia, scar, and hibernating myocardium on the survival benefit associated with revascularization in patients with systolic dysfunction.

METHODS AND RESULTS

The extent of perfusion defects and metabolism-perfusion mismatch was measured with an automated quantitative method in 648 consecutive patients (age, 65±12 years; 23% women; mean left ventricular ejection fraction, 31±12%) undergoing positron emission tomography. Follow-up time began at 92 days (to avoid waiting-time bias); deaths before 92 days were excluded from the analysis. During a mean follow-up of 2.8±1.2 years, 165 deaths (27.5%) occurred. Cox proportional hazards modeling was used to adjust for potential confounders, including a propensity score to adjust for nonrandomized treatment allocation. Early revascularization was performed within 92 days of positron emission tomography in 199 patients (33%). Hibernating myocardium, ischemic myocardium, and scarred myocardium were associated with all-cause death (P=0.0015, 0.0038, and 0.0010, respectively). An interaction between treatment and hibernating myocardium was present such that early revascularization in the setting of significant hibernating myocardium was associated with improved survival compared with medical therapy, especially when the extent of viability exceeded 10% of the myocardium.

CONCLUSIONS

Among patients with ischemic cardiomyopathy, hibernating, but not ischemic, myocardium identifies which patients may accrue a survival benefit with revascularization versus medical therapy.

Comparison of the prognostic value of normal regadenoson with normal adenosine myocardial perfusion imaging with propensity score matching

OBJECTIVES

The aim of this study was to test the hypothesis that patients with normal regadenoson myocardial perfusion imaging (MPI) have a low rate of cardiac events, similar to patients with normal adenosine MPI.

BACKGROUND

Regadenoson, a new selective adenosine A(2A) receptor agonist, is now a widely used stress agent for MPI. The low rate of cardiac events in patients with normal adenosine MPI is well-documented, but the prognostic implications of a normal regadenoson MPI have not been examined and compared with those with adenosine.

METHODS

Data on primary composite endpoint (cardiac death, myocardial infarction, and coronary revascularization) were collected for 2,000 patients (1,000 regadenoson, and 1,000 adenosine stress) with normal myocardial perfusion and left ventricular ejection fraction referred for vasodilator MPI. In addition, propensity scores were used to assemble a balanced cohort of 505 pairs of patients who were balanced on 36 baseline characteristics.

RESULTS

The primary endpoint occurred in 21 (2.1%; 1.1%/year) patients in the regadenoson group and 33 (3.3%; 1.7%/year) patients in the adenosine group (hazard ratio [HR] for regadenoson vs. adenosine: 0.62; 95% confidence interval [CI]: 0.36 to 1.08; p = 0.090). In the propensity-matched pairs, the primary endpoint occurred in 7 (1.4%; 0.7%/year) patients in the regadenoson group and 13 (2.6%; 1.3%/year) patients in the adenosine group (matched HR: 0.58; 95% CI: 0.23 to 1.48; p = 0.257). Cardiac deaths were infrequent in the entire sample and in the propensity-matched groups; the cardiac death rate was 0.9%/year and 1.15%/year in the regadenoson and adenosine groups (HR: 0.77; 95% CI: 0.42 to 1.43; p = 0.404) in the pre-match sample and 0.5%/year and 0.7%/year in the matched groups, respectively (HR: 0.83; 95% CI: 0.25 to 2.73; p = 0.763).

CONCLUSIONS

Major cardiac events are infrequent in patients with normal regadenoson MPI. These findings provide assurance that normal MPI using a simpler stress protocol with regadenoson provides prognostic data similar to normal adenosine MPI.

[Myocardial perfusion scintigraphy - short form of the German guideline]

This guideline is a short summary of the guideline for myocardial perfusion scintigraphy published by the Association of the Scientific Medical Societies in Ger-many (AWMF). The purpose of this guideline is to provide practical assistance for indication and examination procedures as well as image analysis and to present the state-of-the-art of myocardial-perfusion-scintigraphy. After a short introduction on the fundamentals of imaging, precise and detailed information is given on the indications, patient preparation, stress testing, radiopharmaceuticals, examination protocols and techniques, radiation exposure, data reconstruction as well as information on visual and quantitative image analysis and interpretation. In addition possible pitfalls, artefacts and key elements of reporting are described.

Contrast-enhanced cardiac magnetic resonance imaging

Cardiac magnetic resonance (CMR) imaging has significantly evolved in the past decade and is well established in the evaluation of coronary artery disease (CAD). The evaluation of cardiac anatomy and contractility by high-resolution CMR can be improved by using intravenous administration of gadolinium-based contrast agents. Delayed enhancement CMR imaging has become the gold standard for quantification of myocardial viability in CAD. Contrast-enhanced CMR imaging may circumvent the need for endomyocardial biopsy or localize the involved regions, thereby improving the diagnostic yield of this invasive procedure. The application of contrast-enhanced CMR as an advanced imaging technique for ischemic and nonischemic diseases is reviewed.

A blunted heart rate response to regadenoson is an independent prognostic indicator in patients undergoing myocardial perfusion imaging

BACKGROUND

Regadenoson myocardial perfusion imaging (MPI) is a useful method for risk assessment. We hypothesized that the heart rate response (HRR) to regadenoson carries incremental prognostic information to that derived from perfusion pattern and left ventricular (LV) ejection fraction (EF).

METHODS AND RESULTS

The study population included 1,156 (60 ± 13 years, 46% women, 40% diabetes mellitus, 53% chronic kidney disease) patients. During a follow-up period of 22 ± 5 months, 103 patients died (9%). Independent determinants of the HRR included age, gender, race, diabetes mellitus, coronary revascularization, LVEF, use of insulin and aldosterone antagonists. Decreasing HRR was associated with stepwise increase in mortality (log-rank P < .0001). In a Cox proportional model for mortality that adjusted for age, gender, diabetes mellitus, renal disease, and MPI findings, HRR in the lowest quartile was independently associated with fivefold increase in mortality compared to the highest quartile [HR 5.2, 95% CI 2.3-12.0, P < .0001]. Patients with a normal HRR had a relatively low annualized total mortality despite the presence of risk factors. The addition of HRR to traditional MPI findings had a net reclassification improvement of 15%, P = .02.

CONCLUSION

A blunted HRR to regadenoson is an independent predictor of poor outcome, adds incremental value to MPI, and helps in better risk stratification.

The prognostic value of the heart rate response to adenosine in relation to diabetes mellitus and chronic kidney disease

BACKGROUND

Myocardial perfusion imaging (MPI) is a useful method for risk assessment in patients with diabetes mellitus (DM) and chronic kidney disease (CKD), but these patients have a residual risk that is not accounted for by MPI. The objective of this study is to determine whether the heart rate response (HRR) to adenosine has an incremental prognostic value to MPI in high-risk patients.

METHODS

The study group included 879 (age 61 ± 13 years, 48% women, 58% white, 40% DM, 49% CKD) consecutive patients who underwent adenosine MPI. Chronic kidney disease was defined as an estimated glomerular filtration rate <60 mL/min per 1.73 m(2) or dialysis replacement therapy. An HRR <10% (change from baseline) was considered blunted. The outcome of interest was overall mortality.

RESULTS

During a follow-up period of 40 ± 14 months, 212 patients (24%) died. Patients with DM (23.4% ± 16.3% vs 29.4% ± 21.4%, P < .0001) and CKD (22.7% ± 17.6% vs 30.5% ± 20.4%, P < .0001) had lower HRR as compared with patients without DM and CKD, respectively. A blunted HRR was associated with increased mortality in the overall population and in those with DM and CKD and helped in risk stratification when added to traditional MPI findings. In a Cox regression model, a blunted HRR was the strongest predictor of mortality (hazard ratio 2.8, P < .0001) and provided additional prognostic data to MPI (hazard ratio 1.9, P < .0001) after controlling for age, gender, race, history of myocardial infarction, DM, CKD, β-blocker use, and presence of chest pain.

CONCLUSIONS

A blunted HRR to adenosine is an independent predictor of poor outcome, adds incremental value to MPI, and helps in better risk stratification in high-risk patient groups.

Myocardial viability and survival in ischemic left ventricular dysfunction

BACKGROUND

The assessment of myocardial viability has been used to identify patients with coronary artery disease and left ventricular dysfunction in whom coronary-artery bypass grafting (CABG) will provide a survival benefit. However, the efficacy of this approach is uncertain.

METHODS

In a substudy of patients with coronary artery disease and left ventricular dysfunction who were enrolled in a randomized trial of medical therapy with or without CABG, we used single-photon-emission computed tomography (SPECT), dobutamine echocardiography, or both to assess myocardial viability on the basis of prespecified thresholds.

RESULTS

Among the 1212 patients enrolled in the randomized trial, 601 underwent assessment of myocardial viability. Of these patients, we randomly assigned 298 to receive medical therapy plus CABG and 303 to receive medical therapy alone. A total of 178 of 487 patients with viable myocardium (37%) and 58 of 114 patients without viable myocardium (51%) died (hazard ratio for death among patients with viable myocardium, 0.64; 95% confidence interval [CI], 0.48 to 0.86; P=0.003). However, after adjustment for other baseline variables, this association with mortality was not significant (P=0.21). There was no significant interaction between viability status and treatment assignment with respect to mortality (P=0.53).

CONCLUSIONS

The presence of viable myocardium was associated with a greater likelihood of survival in patients with coronary artery disease and left ventricular dysfunction, but this relationship was not significant after adjustment for other baseline variables. The assessment of myocardial viability did not identify patients with a differential survival benefit from CABG, as compared with medical therapy alone. (Funded by the National Heart, Lung, and Blood Institute; STICH ClinicalTrials.gov number, NCT00023595.).

Safety of regadenoson in patients with end-stage liver disease

BACKGROUND

Regadenoson is a selective A(2A) receptor agonist that is used for vasodilator stress myocardial perfusion imaging (MPI). Since the drug is partially metabolized by the liver, its safety in patients with end-stage liver disease (ESLD) needs to be determined.

METHODS AND RESULTS

We studied 168 consecutive patients with ESLD who had regadenoson stress gated single photon emission computed tomography MPI between January 2008 and March 2010 before planned orthotopic liver transplantation and compared the hemodynamic responses and safety profile to 168 control patients. There were 72 women (43%) in ESLD versus 87 (52%) in the control group (P = .1). The patients with ESLD were younger (58 ± 7 vs 62 ± 12 years, P = .0002), but more likely to be Caucasians (P = .002). The MPI images were normal in 161 patients (96%) in each group. The left ventricular ejection fraction was 72 ± 10% in ESLD and 66 ± 11% in the control patients (P = .0001). The heart rate increase in response to regadenoson was lower in patients with ESLD than in the control group (16 ± 11 vs 23 ± 16 bpm, P = .0001), but the changes in systolic and diastolic blood pressures were similar (-9 ± 12 vs -11 ± 14 mmHg and -6 ± 8 vs -7 ± 10 mmHg, respectively, P = NS). There were no deaths or medication-related adverse events that required hospitalization in either group within 30 days of the study.

CONCLUSION

This is the first study to document the tolerability and safety profile of regadenoson in patients with ESLD.

Impact of left ventricular dyssynchrony by phase analysis on cardiovascular outcomes in patients with end-stage renal disease

BACKGROUND

Cardiovascular disease is the leading cause of mortality in patients with end-stage renal disease (ESRD). While left ventricular (LV) perfusion pattern and ejection fraction (EF) are important determinant of outcome, the prognostic importance of LV dyssynchrony, which can also be assessed by gated SPECT myocardial perfusion imaging (MPI), has not been well studied in this population.

METHODS AND RESULTS

The indices of LV mechanical dyssynchrony were measured by automated analysis of gated SPECT MPI in patients with ESRD who were evaluated for transplantation at our institution (2001-2004) and who had coronary angiography within 6 months of the evaluation. All-cause mortality data were prospectively collected and verified against the social security death index database. The study population consisted of 144 ESRD patients aged 53 ± 9 years. 35% were women and 63% had diabetes mellitus. The LVEF was 48 ± 12%. They were followed-up for 41 ± 28 months during which time 55 (38%) died prior to renal transplantation. An abnormal QRS duration was not predictive of worse outcomes (log-rank P = .9). The median phase bandwidth (BW) was 62° (inter-quartile range 47-98°) and standard deviation (SD) was 23° (inter-quartile range 15-35°). Patients with a BW above the median had worse survival (log-rank P = .017) and there was a trend toward worse survival in those with a SD above the median (log-rank P = .096). A 2-year mortality was higher in those with BW ≥ 62° in the entire cohort, and in the subsets of patients with normal LVEF (log-rank P = .001), coronary artery disease by angiography, increased LV mass index, QRS <110 ms, and perfusion defect size <20% of the LV.

CONCLUSIONS

LV mechanical dyssynchrony by phase analysis is a predictor of mortality in patients with ESRD. It may have a role in risk-stratifying patients and should be incorporated in future studies using gated MPI.

Left ventricular mechanical dyssynchrony by phase analysis of gated single photon emission computed tomography in end-stage renal disease

The presence and degree of left ventricular (LV) dyssynchrony in patients with end-stage renal disease (ESRD) has not been well studied. We hypothesized that these patients would be more likely to have mechanical dyssynchrony than a control cohort. The indexes of LV mechanical dyssynchrony were measured by automated analysis of gated single photon emission computed tomography myocardial perfusion imaging in 290 patients with ESRD and 109 control patients. Only patients with normal myocardial perfusion imaging findings and a narrow QRS duration were included. The following variables were derived: LV ejection fraction (EF), volume, mass, and 2 indexes of dyssynchrony, the standard deviation and bandwidth. The standard deviation and bandwidth were significantly greater in those with ESRD (23° ± 13° vs 15° ± 6° and 65° ± 40° vs 42° ± 14°, respectively, p <0.001 for each). The LV volumes and LV mass were significantly lower and LVEF significantly greater in the control group than in the patients with ESRD (p <0.001 for each). The subgroup of 217 patients with ESRD and normal LVEF also had a significantly greater standard deviation and bandwidth than did the control group (21° ± 12° and 57° ± 35°, p <0.001 for each). However, their values were lower than those of the 73 patients with ESRD and a LVEF <50% (30° ± 13° and 90° ± 45°, p <0.001 for each). Finally, 25 patients (9%) with ESRD and none of the control group had a standard deviation >43° (p = 0.01). In conclusion, patients with ESRD had significantly more mechanical dyssynchrony than did the control group, even in absence of electrical dyssynchrony and abnormal LV perfusion or function.