Radionuclide viability testing: should it affect treatment strategy in patients with cardiomyopathy and significant coronary artery disease?

Left ventricular dyssynchrony assessment by phase analysis from gated PET-FDG scans

BACKGROUND

The outcome of patients with severe ischaemic left ventricular (LV) dysfunction is determined by the extent of myocardial viability and the presence of LV dyssynchrony. We aimed at assessing both parameters from the same imaging method, i.e. gated positron emission tomography (PET) F18-fluorodeoxyglucose (FDG) scans.

METHODS

Phase analysis from Emory Cardiac Toolbox was applied on gated PET-FDG scans to assess histogram bandwidth and standard deviation (SD) as a measure of LV dyssynchrony in 30 heart failure patients (mean ejection fraction: 30.2% ± 13.8%) referred for the evaluation of myocardial viability. Cut-off values from single-photon emission computed tomography myocardial perfusion imaging (SPECT-MPI) best predicting cardiac resynchronization therapy (CRT) response served as standard of reference (bandwidth < 135°; phase SD < 43°). Severe LV dyssynchrony was diagnosed if both SPECT-MPI values were above these limits. Intraclass correlation and clinical agreement in detection of severe LV dyssynchrony by PET vs SPECT were assessed.

RESULTS

There was a significant correlation between PET-FDG and SPECT-MPI for bandwidth (r = 0.88, P < .001) and phase SD (r = 0.88, P < .001) resulting in an excellent clinical agreement between the two methods of 93%.

CONCLUSIONS

Accurate LV dyssynchrony assessment by phase analysis of gated PET-FDG scans is feasible, allowing assessing myocardial viability and severe LV dyssynchrony in one scan.

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

OBJECTIVES

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

PATIENTS AND METHODS

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

RESULT

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

CONCLUSIONS

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

Severe Left Ventricular Dyssynchrony Is Associated With Poor Prognosis in Patients With Moderate Systolic Heart Failure Undergoing Coronary Artery Bypass Grafting

OBJECTIVES

The objective of the present study was to assess the relationship between the presence of left ventricular (LV) dyssynchrony and clinical outcome in patients with moderate systolic heart failure undergoing coronary artery bypass graft (CABG) surgery.

BACKGROUND

The presence of LV dyssynchrony is associated with poor prognosis in patients with LV dysfunction.

METHODS

The study consisted of 215 consecutive patients with ischemic cardiomyopathy and dyspnea (age 65 +/- 9 years, 81% male) undergoing CABG. Dyssynchrony was calculated by tissue Doppler imaging from regional time intervals in basal LV segments before and 1 month after CABG. Myocardial viability was assessed using single-photon emission computed tomography (SPECT) before CABG.

RESULTS

Twenty-five patients (11.6%) died within 30 days (in-hospital mortality) of CABG. The presence of pre-CABG dyssynchrony > or =119 ms had the highest predictive accuracy for in-hospital mortality, with a sensitivity of 84% and a specificity of 71%. During the median follow-up period of 359 days (interquartile range 219 to 561), an additional 19 patients (10.3%) died and 34 patients (18.5%) were hospitalized for worsening heart failure. At Cox regression analysis, post-CABG dyssynchrony > or =72 ms and > or =5 viable segments were identified as independent predictors of clinical events, with a hazard ratio (HR) of 5.02, 95% confidence interval (CI) 2.57 to 10.02 (p < 0.001), and an HR of 0.63, 95% CI 0.55 to 0.75 (p < 0.001), respectively. Patients without post-CABG dyssynchrony and with viable myocardium had excellent prognosis compared with patients with severe post-CABG dyssynchrony and nonviable myocardium (event rate 3% vs. 64%; p < 0.001).

CONCLUSIONS

The presence of severe LV dyssynchrony is associated with poor clinical outcomes despite revascularization. These results advocate a routine assessment of both LV dyssynchrony and viability to predict outcome in systolic heart failure patients undergoing CABG surgery.

Effect of exercise training on ventricular function, dyssynchrony, resting myocardial perfusion, and clinical outcomes in patients with heart failure: a nuclear ancillary study of Heart Failure and A Controlled Trial Investigating Outcomes of Exercise TraiNing (HF-ACTION); design and rationale

BACKGROUND

Technetium Tc 99m gated single photon emission computed tomography (SPECT) has become the cornerstone of noninvasive risk stratification in patients with ischemic heart disease, but its role in patients with heart failure is not as well established.

STUDY DESIGN

This study is a substudy of the Heart Failure and A Controlled Trial Investigating Outcomes of Exercise TraiNing (HF-ACTION) trial--a National Institutes of Health/National Heart, Lung, and Blood Institute-funded randomized controlled trial--designed to evaluate the role of exercise training in patients with heart failure due to left ventricular dysfunction. For this substudy, a total of 300 patients distributed on an approximately 1:1 basis between the exercise training and usual care arms of HF-ACTION will undergo resting technetium Tc 99m gated SPECT at baseline and 12 months to compare changes in left ventricular function with exercise training. These changes, along with baseline data, will be correlated with changes in exercise parameters, inflammatory markers, and clinical outcomes: death, cardiovascular hospitalization, and quality of life scores. In a subset of patients, first-pass radionuclide ventriculography will be obtained to assess the relationship between ventricular dyssynchrony, ejection fraction, changes in exercise parameters, and outcomes.

CONCLUSION

The role of nuclear imaging in patients with heart failure remains poorly defined. This substudy aims to harness the power of a large heart failure trial (HF-ACTION) to further delineate the utility of technetium Tc 99m gated SPECT imaging and first-pass radionuclide ventriculography for predicting important clinical outcomes in this population.

Mortality risk associated with ejection fraction differs across resting nuclear perfusion findings

BACKGROUND

Left ventricular ejection fraction (LVEF) is a significant predictor of morbidity and death. The nuclear summed rest score (SRS) measures myocardial perfusion defects and provides prognostic information, but its effects on long-term outcomes are not fully established. Moreover, information regarding the potential interaction between these 2 covariates is limited. The purpose of this study was to determine whether the mortality risk associated with LVEF is the same across all values of SRS in a population undergoing evaluation for ischemic heart disease.

METHODS AND RESULTS

We examined 3,187 patients who underwent cardiac catheterization and perfusion single photon emission computed tomography imaging with a maximum follow-up of 8.1 years and median follow-up of 3.1 years. Cox proportional hazards modeling showed that increasing nuclear SRS and decreasing LVEF were independently associated with a higher long-term mortality rate, with a clinically significant interaction between them (P = .032). Patients with a normal LVEF and a high SRS (greater perfusion abnormality) have a prognosis similar to those with a reduced LVEF.

CONCLUSIONS

Resting perfusion studies provide prognostic information for long-term survival and significantly impact the interpretation of mortality risk associated with changes in LVEF. Patient prognostication, risk stratification, and future research using these variables should take this interaction into account.

Revascularization for heart failure

Coronary artery disease is the most common underlying cause of heart failure, yet there is little consensus on the role of revascularization in the management of patients with ischemic cardiomyopathy. The concept of recovery of dysfunctional but viable myocardium forms the pathophysiologic basis for the benefit of revascularization. Data from observational studies suggest that patients with coronary disease and left ventricular dysfunction may have improved outcomes after surgical revascularization or percutaneous coronary intervention (PCI) compared to medical treatment. Viability testing may be useful in selecting a population of patients who will receive differential benefit. In the clinical management of patients with heart failure, clinicians face challenging decisions about whether to recommend revascularization especially in patients who do not have angina. As data from randomized trials are awaited, PCI and coronary artery bypass grafting may be considered as complimentary revascularization approaches. Registry data suggest a benefit of coronary artery bypass grafting over PCI in patients with reduced ejection fraction; however, in patients with focal disease and comorbidities including previous surgery, PCI is reasonable, especially if complete revascularization is possible.

Revascularization in Severe Left Ventricular Dysfunction

Revascularization is a treatment option for moderate-to-severe ischemic cardiomyopathy. Limitations of the current literature, lack of completed randomized trials, and higher periprocedural risks create significant uncertainty about the optimal treatment strategy. This review focuses on the available literature describing the effect of revascularization on outcome and the role of noninvasive viability testing. It attempts to identify a subset of patients likely to benefit from therapy.

Relationship of myocardial perfusion imaging findings to outcome of patients with heart failure and suspected ischemic heart disease

BACKGROUND

We retrospectively identified heart failure patients with suspected ischemic heart disease who underwent myocardial perfusion imaging (MPI) to examine the relationship of MPI findings to subsequent patient outcomes.

METHODS

The study group consisted of 336 patients with heart failure, left ventricular ejection fraction <45%, and suspected ischemic heart disease who underwent MPI during the period of January 1991 to December 31, 1997. Patients were divided in 3 subgroups: group A (n = 137), large fixed perfusion defects; group B (n = 77), large reversible perfusion defects; and group C (n=122), absence of a large reversible or fixed perfusion defect.

RESULTS

Overall, the 5-year mortality rate was high at 49.2% +/- 3.1%. Mortality was significantly different (P =.009) among the 3 subgroups. Groups A and B had a similar 5-year mortality rates >50%. Group C had a relatively better, but still substantial 5-year mortality rate of 40%. The overall revascularization rate was low (9.7% in 5 years).

CONCLUSION

These results indicate a high 5-year mortality rate in patients with large myocardial perfusion defects (fixed or reversible) and presumably an ischemic etiology for their heart failure. Patients with no large or absent perfusion defects had more favorable survival outcomes.

Clinical characteristics and referral pattern of patients with left ventricular dysfunction and significant coronary artery disease undergoing radionuclide imaging

BACKGROUND

Many observational studies that predict patient outcomes have examined the use of myocardial perfusion imaging results. However, a referral pattern for radionuclide testing could bias these analyses and should be determined. These patients may also differ with regard to the extent of coronary artery disease (CAD). All of these differences must be incorporated into proper outcomes examinations. We sought to identify the nuclear perfusion imaging referral pattern for patients with left ventricular (LV) dysfunction and significant CAD.

METHODS AND RESULTS

Patients with LV dysfunction and CAD (n = 2951) meeting our inclusion criteria were compared by receipt or absence of radionuclide perfusion testing within 6 months before or after angiography. Pearson chi2 and Kruskal-Wallis analyses were used to examine differences in baseline characteristics and catheterization results, whereas logistic regression modeling was applied to predict nuclear imaging referral before and after catheterization. Precatheterization nuclear cohort patients were more likely to be minority patients (odds ratio [OR], 1.34; P =.0083) with previous cardiac revascularization (OR, 2.27; P =.0001), Charlson comorbidity index greater than 1 (OR, 1.146; P =.0091), and heart failure symptoms (OR, 1.62; P =.0001) than those without imaging. They were less likely to have a myocardial infarction (OR, 0.464; P =.0001). After catheterization, the nuclear patients were more likely to have had congestive heart failure (OR, 1.452; P =.0019), a myocardial infarction (OR, 1.353; P =.0371), an ejection fraction lower than 30% (OR, 1.058; P =.0002), and prior revascularization (OR, 1.880; P =.0001). In addition, they had fewer diseased vessels (OR, 0.731; P =.0001).

CONCLUSIONS

Bias exists in nuclear referral for patients with LV dysfunction and significant CAD and must be considered when interpreting observational studies on this topic.