Gated cardiac blood pool studies in atrial fibrillation: role of cycle length windowing

Myocardial perfusion imaging with retrospective gating and integrated correction of attenuation, scatter, respiration, motion, and arrhythmia

BACKGROUND

Absolute quantitative myocardial perfusion SPECT requires addressing of aleatory and epistemic uncertainties in conjunction with providing image quality sufficient for lesion detection and characterization. Iterative reconstruction methods enable the mitigation of the root causes of image degradation. This study aimed to determine the feasibility of a new SPECT/CT method with integrated corrections attempting to enable absolute quantitative cardiac imaging (xSPECT Cardiac; xSC).

METHODS

We compared images of prototype xSC and conventional SPECT (Flash3DTM) acquired at rest from 56 patients aged 71 ± 12 y with suspected coronary heart disease. The xSC prototype comprised list-mode acquisitions with continuous rotation and subsequent iterative reconstructions with retrospective electrocardiography (ECG) gating. Besides accurate image formation modeling, patient-specific CT-based attenuation and energy window-based scatter correction, additionally we applied mitigation for patient and organ motion between views (inter-view), and within views (intra-view) for both the gated and ungated reconstruction. We then assessed image quality, semiquantitative regional values, and left ventricular function in the images.

RESULTS

The quality of all xSC images was acceptable for clinical purposes. A polar map showed more uniform distribution for xSC compared with Flash3D, while lower apical count and higher defect contrast of myocardial infarction (p = 0.0004) were observed on xSC images. Wall motion, 16-gate volume curve, and ejection fraction were at least acceptable, with indication of improvements. The clinical prospectively gated method rejected beats ≥20% in 6 patients, whereas retrospective gating used an average of 98% beats, excluding 2% of beats. We used the list-mode data to create a product equivalent prospectively gated dataset. The dataset showed that the xSC method generated 18% higher count data and images with less noise, with comparable functional variables of volume and LVEF (p = ns).

CONCLUSIONS

Quantitative myocardial perfusion imaging with the list-mode-based prototype xSPECT Cardiac is feasible, resulting in images of at least acceptable image quality.

Cardiac Imaging to Assess Left Ventricular Systolic Function in Atrial Fibrillation

The validity and reproducibility of systolic function assessment in patients with atrial fibrillation (AF) using cardiac magnetic resonance, echocardiography, nuclear imaging and computed tomography is unknown. A prospectively-registered systematic review was performed, including 24 published studies with patients in AF at the time of imaging and reporting validity or reproducibility data on left ventricular systolic parameters (PROSPERO: CRD42018091674). Data extraction and risk of bias were performed by 2 investigators independently and synthesized qualitatively. In 3 cardiac magnetic resonance studies (40 AF patients), left ventricular ejection fraction and stroke volume measurements correlated highly with catheter angiography (r ≥0.85), and intra- and/or interobserver variability were low. From 3 nuclear studies (171 AF patients), there were no external validation assessments but intra and/or interobserver and intersession variability were low. In 18 echocardiography studies (2,566 AF patients), 2 studies showed high external validity of global longitudinal strain and tissue Doppler s' with angiography-derived dP/dt (r ≥0.88). Global longitudinal strain and myocardial performance index were both associated with adverse cardiovascular events. Reproducibility of echocardiography was better when selecting an index-beat (where 2 preceding R-to-R intervals are similar) compared to averaging of consecutive beats. There were no studies relating to computed tomography. Most studies were small and biased by selection of patients with good quality images, limiting clinical extrapolation of results. The validity of systolic function measurements in patients with AF remains unclear due to the paucity of good-quality data.

Interassay reproducibility of myocardial perfusion gated SPECT in patients with atrial fibrillation

AIM

The aim of this study was to assess interassay reproducibility of myocardial perfusion gated-SPECT for calculation of end-diastolic volume (EDV), end-systolic volume (ESV), and left ventricular ejection fraction (LVEF) in patients with atrial fibrillation (AF).

METHODS

One hundred and fifteen consecutive patients with AF from three participating hospitals (mean age 68.9 years, 39 women) were included in the study. All patients underwent two image gated acquisitions at rest with a 30 minute interval between them. Quantitative data were obtained using the QGS and ECT software algorithms.

RESULTS

Heart rate was similar in both studies: 74.94 +/- 15.2 vs 73.03 +/- 15.57. QGS yielded an LVEF of 54.4%/53.8%, an EDV of 100 mL/101.5 mL, and an ESV of 51 mL/52.3 mL; and ECT showed an LVEF of 63.6%/62.9%, an EDV of 125.8 mL/127.4 mL and ESV of 54.1 mL/56.3 mL. Correlation between the two acquisitions was high (>0.948) for both methods for LVEF, EDV and ESV. Regression and Bland-Altman graphics showed a good agreement between all parameters. Interassay variation coefficients for each method (QGS/ECT) were 5.29% vs 4.83% for LVEF, 4.94% vs 5.17% for EDV, and 9.94% vs 12.78% for ESV.

CONCLUSIONS

Interassay reproducibility of LVEF and EDV with gated-SPECT in patients with AF is good, whereas for ESV it is suboptimal, particularly when ESV is small.

Atrial fibrillation is associated with an increased risk for mortality and heart failure progression in patients with asymptomatic and symptomatic left ventricular systolic dysfunction: a retrospective analysis of the SOLVD trials. Studies of Left Ventricular Dysfunction

OBJECTIVE

This study undertook to determine if the presence of atrial fibrillation in patients with asymptomatic and symptomatic left ventricular dysfunction was associated with increased mortality and, if so, whether the increase could be attributed to progressive heart failure or arrhythmic death.

BACKGROUND

Atrial fibrillation is a common condition in heart failure with the potential to impact hemodynamics and progression of left ventricular systolic dysfunction as well as the electrophysiologic substrate for arrhythmias. The available data do not conclusively define the effect of atrial fibrillation on prognosis in heart failure.

METHODS

A retrospective analysis of the Studies of Left Ventricular Dysfunction Prevention and Treatment Trials was conducted that compared patients with atrial fibrillation to those in sinus rhythm at baseline for the risk of all-cause mortality, progressive pump-failure death and arrhythmic death.

RESULTS

The patients with atrial fibrillation at baseline, compared to those in sinus rhythm, had greater all-cause mortality (34% vs. 23%, p < 0.001), death attributed to pump-failure (16.7% vs. 9.4%, p < 0.001) and were more likely to reach the composite end point of death or hospitalization for heart failure (45% vs. 33%, p < 0.001), but there was no significant difference between the groups in arrhythmic deaths. After multivariate analysis, atrial fibrillation remained significantly associated with all-cause mortality (relative risk [RR] 1.34, 95% confidence interval [CI] 1.12 to 1.62, p=0.002), progressive pump-failure death (RR 1.42, 95% CI 1.09 to 1.85, p=0.01), the composite end point of death or hospitalization for heart failure (RR 1.26, 95% CI 1.03 to 1.42, p=0.02), but not arrhythmic death (RR 1.13; 95% CI 0.75 to 1.71; p=0.55).

CONCLUSIONS

The presence of atrial fibrillation in patients with asymptomatic and symptomatic left ventricular systolic dysfunction is associated with an increased risk for all-cause mortality, largely explained by an increased risk for pump-failure death. These data suggest that atrial fibrillation is associated with progression of left ventricular systolic dysfunction.