Phase Analysis of Gated Myocardial Perfusion Single-Photon Emission Computed Tomography Compared With Tissue Doppler Imaging for the Assessment of Left Ventricular Dyssynchrony

SPECT myocardial perfusion imaging for the evaluation of left ventricular mechanical dyssynchrony in obese patients

OBJECTIVE

Left ventricular dyssynchrony (LVD), the loss of coordinated contraction in the left ventricle, is an early sign of heart failure. LVD can be assessed using phase analysis techniques with gated single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI). This study aimed to investigate the impact of obesity on LVD through phase analysis.

METHODS

We retrospectively enrolled 152 obese patients and 80 age- and sex-matched nonobese patients who showed normal myocardial perfusion and normal left ventricular ejection fraction (LVEF) on MPI. Phase standard deviation (PSD) and phase histogram bandwidth (PBW), as phase analysis parameters, were compared between patients with and without obesity.

RESULTS

Although PSD values were within the normal range (cut-off value >23) for both groups, the PSD values of obese patients were higher than those of the nonobese (20.49 ± 8.66 vs. 14.81 ± 4.93; p < 0.05). PBW values of obese patients were statistically significantly higher than those of the nonobese (57.03 ± 23.17 vs. 41.40 ± 9.96; p < 0.05). The PBW values of obese patients exceeded the normal limits (cut-off value >49). A weak positive correlation was observed between body mass index (BMI) and PBW values in obese patients (r = 0.181, p < 0.05). In patients of normal weight, no correlations were found between BMI and phase analysis parameters.

CONCLUSION

LVD may develop in obese patients, even when myocardial perfusion and ejection fraction are preserved. The use of phase analysis with gated SPECT could be an additional finding improving the early detection of left ventricular dyssynchrony in obese patients.

Usefulness of phase analysis on ECG gated single photon emission computed tomography myocardial perfusion imaging

Electrocardiogram (ECG)-gated single photon emission computed tomography myocardial perfusion imaging (GSPECT-MPI) is widely used for assessing coronary artery disease. Phase analysis on GSPECT-MPI can assess left ventricular mechanical dyssynchrony quantitatively on standard GSPECT-MPI alongside myocardial perfusion and function assessment. It has been shown that phase variables by GSPECT-MPI correlate well with tissue Doppler imaging by echocardiography. Main phase variables quantified by GSPECT-MPI are entropy, bandwidth, and phase standard deviation. Although those variables are automatically obtained from several software packages including Quantitative Gated SPECT and Emory Cardiac Toolbox, the methods for their measurement vary in each package. Several studies have shown that phase analysis has predictive value for response to cardiac resynchronization therapy and prognostic value for future adverse cardiac events beyond standard GSPECT-MPI variables. In this review, we summarize the basics of phase analysis on GSPECT-MPI and usefulness of phase analysis in clinical practice.

Left Ventricular Strain from Myocardial Perfusion PET Imaging: Method Development and Comparison to 2-Dimensional Echocardiography

This study aimed to develop a measure of longitudinal, radial, and circumferential myocardial strain at rest and regadenoson during pharmacologic stress using 82Rb PET electrocardiography-gated myocardial perfusion imaging (MPI). Methods: We retrospectively identified 80 patients who underwent rest and regadenoson-stress CT attenuation-corrected 82Rb PET and had a standard resting transthoracic echocardiogram (TTE) with global longitudinal strain (GLS) analysis within 3 mo. A method was developed to compute longitudinal, radial, and circumferential strain from PET MPI at stress and rest. PET MPI-derived strain and left ventricular function were compared with resting TTE measures as the clinical reference standard. Interobserver agreement of PET MPI strain and left ventricular ejection fraction processing was reported. Results: Longitudinal strain assessed with resting TTE GLS showed good correlation with PET MPI at stress (r = 0.68, P < 0.001) and rest (r = 0.58, P < 0.001). Resting TTE GLS also correlated with PET MPI radial strain at stress (r = -0.70, P < 0.001) and rest (r = -0.59, P < 0.001) and circumferential strain at stress (r = 0.67, P < 0.001) and rest (r = 0.69, P < 0.001). The left ventricular ejection fraction showed good correlation between resting TTE and PET MPI at stress (r = 0.83, P < 0.001) and rest (r = 0.80, P < 0.001). Bland-Altman analysis indicated positive bias of TTE GLS compared with PET MPI longitudinal strain at stress (mean difference = 5.1%, 95% CI = [-2.5, 12.7]) and rest (mean difference = 4.2%, 95% CI = [-4.3, 12.8]). Reproducibility of PET MPI longitudinal strain showed good agreement at stress (concordance correlation coefficient = 0.73, P < 0.001) and rest (concordance correlation coefficient = 0.74, P < 0.001), with Bland-Altman analysis showing a small bias in the longitudinal direction at stress (mean difference = -0.2%) and rest (mean difference = -1.0%). Conclusion: Strain measured with PET MPI using an automated technique correlated well with resting GLS strain obtained by TTE, and the measure is reproducible. Strain from PET MPI should be investigated further to establish reference ranges and assess its value in routine clinical practice.

Feasibility of Left Ventricle Lead Implantation in Cardiac Resynchronization Therapy Guided by Gated SPECT and Ventricular Remodeling

BACKGROUND

Cardiac resynchronization therapy (CRT) may benefit patients with advanced heart failure (HF). Abnormal eccentricity index by gated SPECT is related to structural and functional alterations of the left ventricle (LV).

OBJECTIVE

The aim of this study is to evaluate the feasibility of LV lead implantation guided by phase analysis and its relationship to ventricular remodeling.

METHODS

Eighteen patients with indication for CRT underwent myocardial scintigraphy for implant orientation, and eccentricity and ventricular shape parameters were evaluated. P < 0.05 was adopted as statistical significance.

RESULTS

At baseline, most patients were classified as NYHA 3 (n = 12). After CRT, 11 out of 18 patients were reclassified to a lower degree of functional limitation. In addition, patients' quality of life was improved post-CRT. Significant reductions were observed in QRS duration, PR interval, end-diastolic shape index, end-systolic shape index, stroke volume, and myocardial mass post-CRT. The CRT LV lead was positioned concordant, adjacent, and discordant in 11 (61.1%), 5 (27.8%), and 2 (11.1%) patients, respectively. End-systolic and end-diastolic eccentricity demonstrated reverse remodeling post-CRT.

CONCLUSIONS

LV lead implantation in CRT guided by gated SPECT scintigraphy is feasible. The placement of the electrode concordant or adjacent to the last segment to contract was a determinant of reverse remodeling.

Prognostic value of left ventricular mechanical dyssynchrony induced by exercise stress in patients with normal myocardial perfusion single-photon emission computed tomography

BACKGROUND

Left ventricular mechanical dyssynchrony (LVMD) induced by exercise stress was reported to be clinically useful in detecting multivessel coronary artery diseases. The aim of this study was to compare the prognostic value of LVMD induced by pharmacological stress with that induced by exercise stress.

METHODS

We retrospectively examined 918 consecutive patients who underwent exercise (N = 310) or pharmacological stress (N = 608) 99mTc-tetrofosmin single-photon emission computed tomography (SPECT) with normal myocardial perfusion. LVMD was evaluated by phase analysis as the indices of phase bandwidth and phase standard deviation (PSD).

RESULTS

During the follow-up period (2.2 ± 1.9 years), 74 major cardiac events (MCEs) occurred (7 cases of cardiac death, 17 cases of heart failure, and 50 cases of coronary intervention). In global patients, the indices of LVMD on rest images were significantly greater in patients with MCEs (bandwidth (°): 51 ± 31 vs 37 ± 21, P = .001, PSD: 14 ± 9 vs 10 ± 6, P = .001). The exercise stress bandwidth was significantly higher in patients with MCEs (62 ± 37° vs 42 ± 21°, P = .026), as was the pharmacological stress bandwidth (57 ± 35° vs 43 ± 24°, P = .006). Multivariate analysis demonstrated the exercise stress bandwidth to be an independent predictor of MCEs (HR 1.017, CI 1.003 to 1.032, P = .019), but the pharmacological stress bandwidth had no influence on MCEs.

CONCLUSIONS

LVMD induced by exercise stress was an independent predictor of MCEs in patients with normal perfusion SPECT, whereas that induced by pharmacological stress had no association with further events.

Myocardial ischemia and previous infarction contribute to left ventricular dyssynchrony in patients with coronary artery disease

AIMS

The aim of this study was to characterize determinants of left ventricular mechanical dyssynchrony (LVMD) in patients with coronary artery disease (CAD).

METHODS

Medical records and results of myocardial perfusion SPECT/CT studies were evaluated in 326 patients with previously diagnosed CAD. LVMD was assessed with the phase analysis of ECG-gated myocardial SPECT. Dyssynchrony was described with phase histogram bandwidth (PHBW), standard deviation (PHSD) or entropy (PHE) values above limit of the highest normal.

RESULTS

Prevalence of LVMD was 29% in CAD patients. Size of the infarction scar and ischemia extent correlated significantly with PHBW, PHSD and PHE (P < 0.001 for all). Independent predictors of LVMD were myocardial infarction scar (P = 0.004), ischemia extent (P = 0.003), and QRS duration (P = 0.003). Previous percutaneous coronary intervention and coronary artery bypass grafting did not independently predict dyssynchrony.

CONCLUSIONS

Almost one-third of CAD patients had significant LVMD. Dyssynchrony was associated with earlier myocardial infarction and presence of myocardial ischemia. Previous percutaneous coronary intervention and coronary artery bypass grafting did not independently predict dyssynchrony.

IGF-1 is not related to long-term outcome in hyperglycemic acute coronary syndrome patients

PURPOSE

Insulin-like growth factor-1 (IGF-1) has been associated with both protective and detrimental effects on the development of ischemic heart disease. The relationship between IGF-1 levels and major adverse cardiovascular events (MACE) in acute coronary syndrome (ACS) patients remains unclear. This study aimed to investigate the relationship between IGF-1 admission levels in hyperglycemic ACS patients and: (1) MACE over a 5 years follow-up, (2) type 2 diabetes at discharge, and (3) post-ACS myocardial infarct size and dysfunction.

METHODS

This was a post hoc analysis of the BIOMArCS-2 randomized controlled trial. From July 2008 to February 2012, 276 ACS patients with admission plasma glucose level between 140 and 288 mg/dL were included. Records of the composite of all-cause mortality and recurrent non-fatal myocardial infarction were obtained during 5 years follow-up. Venous blood samples were collected on admission. IGF-1 was measured batchwise after study completion. Oral glucose tolerance test was performed to diagnose type 2 diabetes, whereas infarct size and left ventricular function were assessed by myocardial perfusion scintigraphy (MPS) imaging, 6 weeks post-ACS.

RESULTS

Cumulative incidence of MACE was 24% at 5 years follow-up. IGF-1 was not independently associated with MACE (HR:1.00 (95%CI:0.99-1.00), p = 0.29). Seventy-eight patients (28%) had type 2 diabetes at discharge, and the highest quartile of IGF-1 levels was associated with the lowest incidence of diabetes (HR:0.40 (95%CI:0.17-0.95), p = 0.037). IGF-1 levels were not associated with post-ACS myocardial infarct size and dysfunction.

CONCLUSIONS

IGF-1 carries potential for predicting type 2 diabetes, rather than long-term cardiovascular outcomes and post-ACS myocardial infarct size and dysfunction, in hyperglycemic ACS patients.

Gated single-photon emission computed tomography myocardial perfusion imaging phase analysis as an imaging biomarker for mortality prediction in heart failure patients undergoing cardiac resynchronization therapy

OBJECTIVE

Cardiac resynchronization therapy (CRT) reduces morbidity and mortality in heart failure patients. The purpose of this study was to assess the value of gated myocardial perfusion single-photon emission computed tomography (GMPS) phase analysis for predicting survival in heart failure patients undergoing CRT.

METHODS

This retrospective cohort study evaluated heart failure patients who underwent GMPS prior to CRT. Phase histogram bandwidth (PHB) and phase SD (PSD) were calculated using GMPS data. Cox proportional hazards model was used to identify independent predictors of overall survival (OS).

RESULTS

A total of 35 patients (age 65.1 ± 13.3, 27 men and 8 women), who were followed for mean of 4.1 ± 2.9 years, were enrolled in the study. PSD of greater than 45° was found to be an independent predictor of poor OS (hazard ratio = 12.63, P = 0.011) when compared with age (hazard ratio = 1.00, P = 0.922), gender (hazard ratio = 0.31, P = 0.155), NYHA class (hazard ratio = 0.45, P = 0.087), QRS duration greater than 150 ms (hazard ratio = 2.38, P = 0.401), pre-CRT left ventricular ejection fraction (LVEF) (hazard ratio = 0.95, P = 0.175) and etiology of heart failure (hazard ratio = 1.42, P = 0.641). Furthermore, PHB greater than 140° was also found to be an independent predictor of poor OS (hazard ratio = 5.63, P = 0.040) when compared with age, gender, NYHA class, QRS duration greater than 150 ms, pre-CRT LVEF and etiology of heart failure.

CONCLUSIONS

PSD and PHB, measured by GMPS, may serve as biomarkers for the prediction of survival in patients undergoing CRT.

Diastolic dyssynchrony assessment by gated myocardial perfusion-SPECT in subjects who underwent cardiac resynchronization therapy

BACKGROUND

Left ventricular diastolic dyssynchrony (LVDD) can be assessed by gated myocardial perfusion single-photon emission computed tomography (GMP-SPECT). LVDD is an area of interest in subjects who underwent cardiac resynchronization therapy (CRT). The aim of this post hoc analysis was to assess the role of LVDD in subjects with CRT who were followed up at 6-month period.

MATERIAL & METHODS

Left ventricular diastolic dyssynchrony was assessed by GMP-SPECT at baseline and after CRT procedure in 160 subjects from 10 different cardiological centers. CRT procedure was performed as per current guidelines. Outcomes were defined as improvement in ≥1 New York Heart Association (NYHA) class, left ventricular ejection fraction (LVEF) by 5%, and reduction in end-systolic volume (ESV) by 15% and 5% points in Minnesota Living with Heart Failure Questionnaire. LVDD was defined as diastolic phase standard deviation ≥40 ± 14°.

RESULTS

Improvement in NYHA functional class occurred in 105 (65.6%), LVEF in 74 (46.3%), decrease in ESV in 86 (53.8%), and Minnesota score in 85 (53.1%) cases. Baseline LV diastolic standard deviation was 53.53° ± 20.85 and at follow-up 40.44° ± 26.1283; (P < 0.001). LVDD was not associated with improvement in clinical outcomes at follow-up.

CONCLUSION

CRT improves both systolic and diastolic dyssynchrony values at 6-month follow-up. LVDD at baseline is correlated with cardiac functionality at follow-up, but not with overall favorable clinical outcomes.

Left ventricular mechanical dyssynchrony in patients with chest pain and normal epicardial coronary arteries

BACKGROUND

To detect ischemia in patients with angina and normal coronaries frequently represents a complex diagnosis.

METHODS

To investigate whether left ventricular mechanical dyssynchrony by phase analysis contributes in the evaluation of patients with chest pain and normal coronaries, gated-SPECT myocardial perfusion imaging (MPI) at rest and 30 minutes post-stress was performed in 218 patients with normal epicardial coronaries, who were divided into two groups: those with summed difference score (SDS) ≥ 4 (54 patients, Group 1), and those with SDS < 4 (164 patients, Group 2). Intraventricular synchronism-phase standard deviation (PSD) and histogram bandwidth (HBW)-was evaluated by phase analysis.

RESULTS

Women were significantly more frequent in Group 2 (those without ischemia in SPECT MPI): 113 (69%) vs 25 (46%), P = .00001. In males, left ventricular ejection fraction (LVEF) and ventricular volumes were not significantly different between patients with or without ischemia. However, ischemic females showed significantly higher ventricular volumes, minor post-stress LVEF and more negative delta LVEF (- 3.9 vs 0.34, P = .0008) than the non-ischemic ones. There was a significant post-stress increase of PSD and HBW among males, although not among females. According to SSS (≥ 4, with ischemia/necrosis; < 4, without ischemia/necrosis), post-stress PSD and HBW significantly increase both in male and female, and PSD and HBW were significantly higher in females with SSS ≥ 4 compared to those with SSS < 4 (PSD rest: 19.04° vs 11.72°, P < .0001; HBW rest: 58.85° vs 38.21°, P < .0001). PSD and HBW were also higher among males with SSS ≥ 4 compared to those with SSS < 4, although not significantly.

CONCLUSION

Higher ventricular volumes in females and dyssynchrony are associated with inducible ischemia in MPI in patients with chest pain and normal coronaries. Stress-induced ischemia increases degree of dyssynchrony.

Are SPECT MPI measures of dyssynchrony dyssynchronous?

BACKGROUND

Assessment of left ventricular mechanical dyssynchrony (LVMD) from gated SPECT myocardial perfusion imaging (MPI) aims to aid selection of patients for cardiac resynchronization therapy (CRT), using either the standard deviation of left ventricular phase (PSD) ≥ 43° or phase histogram bandwidth (HBW) of > 38° and > 30.6° in males and females, respectively. We observed dyssynchrony parameters might be affected by test type and alignment.

METHODS

We reviewed 242 patients who underwent gated SPECT MPI with use of the Emory Cardiac Toolbox comparing PSD and HBW at rest and stress for Pearson correlation, and substitutability with Bland-Altman analysis.

RESULTS

There is statistically significant difference in the mean PSD and HBW during rest vs stress (33.4 ± 17.4° vs 20.7 ± 13.5° and 97.7 ± 59.6° vs 59.4 ± 45.4°, respectively, P < 0.001). Proper valve plane alignment rendered smaller values (i.e., less dyssynchrony) in both phase SD and HBW (16.8 ± 13.5) vs (22.2 ± 14.7) (P = 0.011), and (47.0 ± 38.2) vs (60.7 ± 48.0) (P = 0.023), respectively.

CONCLUSION

Proper alignment and test type, particularly low-dose rest vs high-dose stress, should be considered when assessing LVMD using SPECT MPI.

Quantitative clinical nuclear cardiology, part 2: Evolving/emerging applications

Quantitative analysis has been applied extensively to image processing and interpretation in nuclear cardiology to improve disease diagnosis and risk stratification. This is Part 2 of a two-part continuing medical education article, which will review the potential clinical role for emerging quantitative analysis tools. The article will describe advanced methods for quantifying dyssynchrony, ventricular function and perfusion, and hybrid imaging analysis. This article discusses evolving methods to measure myocardial blood flow with positron emission tomography and single-photon emission computed tomography. Novel quantitative assessments of myocardial viability, microcalcification and in patients with cardiac sarcoidosis and cardiac amyloidosis will also be described. Lastly, we will review the potential role for artificial intelligence to improve image analysis, disease diagnosis, and risk prediction. The potential clinical role for all these novel techniques will be highlighted as well as methods to optimize their implementation.

Value of intraventricular dyssynchrony assessment by gated-SPECT myocardial perfusion imaging in the management of heart failure patients undergoing cardiac resynchronization therapy (VISION-CRT)

BACKGROUND

Placing the left ventricular (LV) lead in a viable segment with the latest mechanical activation (vSOLA) may be associated with optimal cardiac resynchronization therapy (CRT) response. We assessed the role of gated SPECT myocardial perfusion imaging (gSPECT MPI) in predicting clinical outcomes at 6 months in patients submitted to CRT.

METHODS

Ten centers from 8 countries enrolled 195 consecutive patients. All underwent gSPECT MPI before and 6 months after CRT. The procedure was performed as per current guidelines, the operators being unaware of gSPECT MPI results. Regional LV dyssynchrony (Phase SD) and vSOLA were automatically determined using a 17 segment model. The lead was considered on-target if placed in vSOLA. The primary outcome was improvement in ≥1 of the following: ≥1 NYHA class, left ventricular ejection fraction (LVEF) by ≥5%, reduction in end-systolic volume by ≥15%, and ≥5 points in Minnesota Living With Heart Failure Questionnaire (MLHFQ).

RESULTS

Sixteen patients died before the follow-up gSPECT MPI. The primary outcome occurred in 152 out of 179 (84.9%) cases. Mean change in LV phase standard deviation (PSD) at 6 months was 10.5°. Baseline dyssynchrony was not associated with the primary outcome. However, change in LV PSD from baseline was associated with the primary outcome (OR 1.04, 95% CI 1.01-1.07, P = .007). Change in LV PSD had an AUC of 0.78 (0.66-0.90) for the primary outcome. Improvement in LV PSD of 4° resulted in the highest positive likelihood ratio of 7.4 for a favorable outcome. In 23% of the patients, the CRT lead was placed in the vSOLA, and in 42% in either this segment or in a segment within 10° of it. On-target lead placement was not significantly associated with the primary outcome (OR 1.53, 95% CI 0.71-3.28).

CONCLUSION

LV dyssynchrony improvement by gSPECT MPI, but not on-target lead placement, predicts clinical outcomes in patients undergoing CRT.

Prognostic value of integrative analysis of electrical and mechanical dyssynchrony in patients with acute heart failure

BACKGROUND

Left ventricular mechanical dyssynchrony has been shown to provide significant clinical values for chronic heart failure (HF) and cardiac resynchronization therapy (CRT). The purpose of this study was to evaluate whether electrical dyssynchrony combined with mechanical dyssynchrony has an incremental benefit over electrical dyssynchrony or mechanical dyssynchrony alone to predict clinical events in patients with acute heart failure (AHF).

METHODS

Ninety-six AHF patients who received standard 12-lead ECG, gated single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI), and echocardiography were enrolled. Thirty-two normal subjects were collected as the control group to get the normal database of mechanical dyssynchrony. The end point is the composite of all-cause death and heart transplantation. Electrical dyssynchrony was defined as QRS duration > 120 ms. Mechanical dyssynchrony was defined as > mean + 2 × SD phase standard deviation (PSD) or phase bandwidth (PBW) based on our normal database.

RESULTS

During the follow-up of 28 ± 10 months, complete data were obtained in 92 patients. 26 (28.3%) Patients who reached the end point were classified into the event group. There were no significant differences in PSD or PBW between the event and non-event groups. However, PBW > 77.76° was independently associated with the end point in the univariate and multivariate analysis (hazard ratio 2.92, 95% confidence interval 1.00-8.47, P = .049; hazard ratio 3.89, 95% confidence interval 1.01-14.97, P = .048). The Kaplan-Meier curve with a log-rank test showed that the end point rate was significantly higher in the patients with PBW > 77.76° (log-rank P = .039). Moreover, the ROC curve analysis showed that the area under the curve (AUC) for predicting end point events by the integrative analysis of QRS > 120 ms and PBW > 77.76° was significantly improved compared to QRS duration > 120 ms (AUC: 0.75 vs 0.68, P = .001) or PBW > 77.76° (AUC: 0.75 vs 0.62, P = .049), respectively. The model of combined electrical and mechanical dyssynchrony yielded a further significantly improved risk prediction for adverse events in the global χ2.

CONCLUSIONS

The combination of QRS duration > 120 ms and PBW > 77.76° was an independent predictor of all-cause death and heart transplantation in AHF patients. The integrative analysis of electrical and mechanical dyssynchrony provides incremental prognostic value for clinical use.

Left ventricular end-systolic contractile entropy can predict cardiac prognosis in patients with complete left bundle branch block

BACKGROUND

Several patients with complete left bundle branch block (CLBBB) show left ventricular (LV) dyssynchrony and poor cardiac prognosis. However, the prognostic value of LV end-systolic contractile entropy which was measured by single-photon emission computer tomography (SPECT) has not been elucidated in patients with CLBBB.

METHODS AND RESULTS

We recruited consecutive 115 sinus-rhythm patients with CLBBB who underwent ECG-gated 201TlCl-SPECT. After 30 days of observation, finally 102 patients (75.2 ± 9.5 years, 62 male) were enrolled and observed retrospectively for a median of 671 days. Twenty-five patients fell into major cardiac events. Multivariate Cox regression analysis showed estimated glomerular filtration rate (eGFR) ≤ 39.35 mL/min and entropy ≥ 79% were significant and independent predictors for major cardiac events (hazard ratio: 4.256 and 7.587, P value = 0.006 and < 0.001, respectively). Machine learning (Random Forest method) revealed eGFR and entropy had higher feature importance than other predictors (0.140 and 0.138, respectively). Kaplan-Meyer curve analysis demonstrated that the group with entropy ≥ 79% and eGFR ≤ 39.36 mL/min had the worst cardiac prognosis (Logrank: P = 0.002).

CONCLUSIONS

Left ventricular end-systolic contractile entropy predicts poor cardiac prognosis in patients with CLBBB, which may be more valuable than the other parameters of SPECT.

Left ventricular dyssynchrony and abnormalities in wall motion, assessed by gated-SPECT as ischemic auxiliary markers

INTRODUCTION

Left ventricular dyssynchrony (LVD) quantified by gated myocardial perfusion studies (MPS), through phase analysis (PA), has shown controversial results in myocardial stunning.

OBJECTIVES

Assessment of LVD and regional wall motion abnormalities (RWMA) in normal and ischemic patients.

METHODS

A cohort of 172 patients were studied. Summed Stress Score (SSS), Summed Resting Score (SRS), and Summed Difference Score (SDS) were evaluated. Group 1-patients with normal MPS (N = 133) and Group 2-patients with myocardial ischemia in the MPS (N = 39). LVD was evaluated through PA and RWM by visual analysis.

RESULTS

SSS 0 vs 9.8 ± 3.9 P = .0001; SDS 0 vs 9.8 ± 3.9 P = .0001; SRS 0 vs 0 P = NS, in G1 and G2. Significant differences were found in LVD between G1 and G2, bandwidth 36 ± 14 vs 63 ± 46 P = .0001; standard deviation 16 ± 10 vs 26 ± 15 P = .0001. In G1, 16% had LVD vs RWMA in 0%, P = .0001 and in G2, 59% with LVD vs 33% with RWMA, P = .03. Sensitivity for LVD 59% and for RWMA 33%, P = .03 and specificity for LVD 83% and for RWMA 100%, P = .0001.

CONCLUSION

Ischemic patients have LVD post-stress due to myocardial stunning. LVD measured by PA could be a useful tool to identify ischemia.

Intraventricular synchronism assessment by gated-SPECT myocardial perfusion imaging in cardiac resynchronization therapy. Does cardiomyopathy type influence results?

Purpose

To analyze the evolution post-cardiac resynchronization therapy (CRT) in left ventricular non-compaction (LVNC) cardiomyopathy (CM) patients compared to other types of CM, according to clinical and functional variables, by using gated-SPECT myocardial perfusion imaging (MPI).

Methods

Ninety-three patients (60 ± 11 years, 28% women) referred for pre-CRT assessment were studied and divided into three groups: 1 (non-ischemic CM with LVNC, 11 patients), 2 (ischemic CM, 28 patients), and 3 (non-ischemic CM, 53 patients). All were studied by a ^99mTc-MIBI gated-SPECT MPI at rest pre-CRT implantation and 6 ± 1 months after, including intraventricular dyssynchrony assessment by phase analysis. Quality of life was measured by the Minnesota Living with Heart Failure Questionnaire (MLHFQ).

Results

No differences in sex, atherosclerotic risk factors other than smoking habit, and MLHFQ results were found among groups. LVNC CM patients were younger, with greater QRS width and lower left ventricular ejection fraction (LVEF) at baseline, but the differences were not significant. No significant differences were found at baseline regarding ventricular function, although end-systolic volume was slightly higher in LVNC CM patients. Mean SRS was significantly higher (p < 0.0001) in ischemic patients (14.9) versus non-ischemic ones (8.7 in group 1 and 9 in group 2). At baseline, LVNC CM patients were significantly more dyssynchronous: Their phase standard deviation (PSD) was higher (89.5° ± 14.2°) versus groups 2 (65.2° ± 23.3°) and 3 (69.7° ± 21.7°), p = 0.007. Although the quality of life significantly improved in all groups, non-ischemic patients (with or without LVNC) showed a higher LVEF increase and volumes reduction at 6 months post-CRT. Dyssynchrony reduced post-CRT in all groups. Nevertheless, those more dyssynchronous at baseline (LVNC CM) exhibited the most significant intraventricular synchronism improvement: PSD was reduced from 89.5° ± 14.2° at baseline to 63.7° ± 20.5° post-CRT (p = 0.028). Six months post-CRT, 89% of patients were responders: 11 (100%) of those with LVNC CM, 25 (86%) of those with ischemic CM, and 47 (89%) of patients with non-ischemic CM. No patient with LVNC CM had adverse events during the follow-up.

Conclusion

CRT contributes to a marked improvement in non-ischemic CM patients with non-compaction myocardium. Phase analysis in gated-SPECT MPI is a valuable tool to assess the response to CRT.

Quantitative clinical nuclear cardiology, part 2: Evolving/emerging applications

Quantitative analysis has been applied extensively to image processing and interpretation in nuclear cardiology to improve disease diagnosis and risk stratification. This is Part 2 of a two-part continuing medical education article, which will review the potential clinical role for emerging quantitative analysis tools. The article will describe advanced methods for quantifying dyssynchrony, ventricular function and perfusion, and hybrid imaging analysis. This article discusses evolving methods to measure myocardial blood flow with positron emission tomography and single-photon emission computed tomography. Novel quantitative assessments of myocardial viability, microcalcification and in patients with cardiac sarcoidosis and cardiac amyloidosis will also be described. Lastly, we will review the potential role for artificial intelligence to improve image analysis, disease diagnosis, and risk prediction. The potential clinical role for all these novel techniques will be highlighted as well as methods to optimize their implementation. (J Nucl Cardiol 2020).

Prognostic value of left ventricular mechanical dyssynchrony indices in long-standing type II diabetes mellitus with normal perfusion and left ventricular systolic functions on SPECT-MPI

OBJECTIVE

To test whether phase analysis indices from SPECT-MPI for left ventricular mechanical dyssynchrony (LVMD) are predictors of major adverse cardiac events (MACEs) in long-standing diabetes mellitus (DM).

METHODS

A total of 136 DM patients with normal perfusion and left ventricular systolic functions were followed up for about two years and divided into two groups according to the presence and the absence of MACEs.

RESULT

Thirteen (9.5%) patients experienced MACEs during follow-up. Patients experiencing MACEs showed significantly higher phase standard deviation (PSD) and wider phase bandwidth (PBW) than those who did not. Moreover, both PSD and PBW showed significant correlations (r = 0.25 and 0.27; P < 0.05) with duration of DM. Logistic regression analysis revealed significant associations of DM duration, microvascular complications, and LVMD indices for predicting MACEs. Kaplan-Meier event-free survival analysis revealed significantly higher rate of MACEs (Logrank = 10.02; P = 0.001) in patients with high PSD and wide PBW. An overall fit model consisting of high-PSD and wide-PBW group was improved with the addition of microvascular complications (χ2 = 15.9; P = 0.03) and further by addition of DM duration of ≥ 15 years (χ2 = 24.3; P = 0.007) as variables.

CONCLUSION

LVMD indices are novel prognostic markers in diabetic patients with normal perfusion and left ventricular systolic functions and their increases in magnitudes with DM-duration and in the presence of microvascular complications.

Could myocardial viability be related to left ventricular dyssynchrony? Simultaneous evaluation by gated SPECT-MPI

BACKGROUND

Left ventricular contraction dyssynchrony (LVCD) has been related to induced ischemia and transmural scar but the interplay of myocardial viability and dyssynchrony is unknown. The aim of the present study was to establish the role of dyssynchrony in the context of a viability study performed with nitrate augmentation gated single photon emission computed tomography (GSPECT) myocardial perfusion imaging (MPI).

METHODS

Fifty-four consecutive patients with ischemic dilated cardiomyopathy (IDC) and depressed left ventricular ejection fraction (LVEF) were included. They underwent a two-day rest/nitroglycerine (NTG) study GSPECT MPI to determine the myocardial viability. Patients with a nitrate-induced uptake increase of > 10% vs baseline, in at least, two consecutive dysfunctional segments were considered viable as well as those who showed no improvement in the uptake but the uptake was > 50% on post NTG study. Patients with no nitrate-induced uptake increase of > 10% and the uptake of < 50% were considered non-viable. Perfusion, function and LVCD were compared in 25 viable patients vs 29 non-viable patients at baseline and after NTG administration.

RESULTS

After NTG administration, in the viable group, the LVEF increased (36.44 ± 6.64% vs 39.84 ± 6.39%) and the end-systolic volume decreased significantly (119.28 ± 31.77 mL vs 109.08 ± 33.17 mL) (P < 0.01). These patients also experienced a significant reduction in the LVCD variables: phase standard deviation was reduced in the post NTG study (57.77° ± 19.47° vs 52.02° ± 17.09°) as well as the phase histogram bandwidth (190.20° ± 78.83° vs 178.0° ± 76.14°) (P < 0.05). Functional and LVCD variables remained similar in the non-viable patients (P > 0.05).

CONCLUSION

In patients with IDC and depressed LVEF, the myocardial viability detected by rest/ NTG GSPECT MPI, might determine LVCD improvement.

Prognostic Value of Left Ventricular Dyssynchrony Assessed with Nuclear Cardiology in Patients with Known or Suspected Stable Coronary Artery Disease with Preserved Left Ventricular Ejection Fraction

Left ventricular (LV) mechanical dyssynchrony assessed with phase analysis of electrocardiogram (ECG) -gated single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) is useful for predicting major cardiac events (MCEs) in patients with cardiac dysfunction. However, there is no report on its usefulness in Japanese patients with known or suspected stable coronary artery disease (CAD) with preserved LV ejection fraction (LVEF).We retrospectively investigated 3,374 consecutive patients with known or suspected CAD who underwent rest ²⁰¹Tl and stress ^99mTc-tetrofosmin ECG-gated SPECT MPI and had preserved LVEF (≥ 45%), and followed them up to confirm their prognosis for three years. The composite endpoint was the onset of MCEs consisting of cardiac death, non-fatal myocardial infarction (MI), unstable angina pectoris, and severe heart failure requiring hospitalization. LV mechanical dyssynchrony was evaluated with phase analysis with the Heart Risk View-F software to obtain the phase bandwidth and standard deviation.During the follow-up, 179 patients experienced MCEs: cardiac death (n = 42); non-fatal MI (n = 34); unstable angina pectoris (n = 54); and severe heart failure (n = 49). Results of the multivariate analysis showed age, a history of MI, diabetes mellitus, summed stress score, and stress phase bandwidth to be independent predictors for MCEs. In Kaplan-Meier analysis, prognoses were significantly stratified with the tertiles of stress phase bandwidth.LV mechanical dyssynchrony assessed with ECG-gated SPECT MPI is useful for predicting a prognosis and stratifying the risk of MCEs in Japanese patients with known or suspected stable CAD with preserved LVEF.

Electrical and mechanical dyssynchrony in patients with right bundle branch block

BACKGROUND

Though fairly benign reputation, the right bundle branch block (RBBB) can cause left ventricular mechanical dyssynchrony (LVMD). Still, the relationship between electrical disturbance and LVMD is partly unclear among these patients.

METHODS

Thirty patients with RBBB and 60 matching controls were studied with vector electrocardiography and myocardial perfusion imaging phase analysis. RBBB group was divided into those with and those without LVMD.

RESULTS

Prevalence of LVMD among RBBB patients was 50% and among controls 22%. Odds ratio (OR) for LVMD in patients with RBBB vs controls without RBBB was 3.6 (95% CI 1.4 to 9.3). Ejection fraction (EF), end-systolic volume, the angle between QRS and T vectors, and the QRS angle in the sagittal plane were significantly different between RBBB patients with and without LVMD. The QRS duration was comparable in these groups. EF associated independently with LVMD, explaining 60% of its variation. A cut-off value of EF ≤ 55% detected LVMD in 100% specificity (sensitivity of 47%).

CONCLUSION

Half of the patients with RBBB had LVMD. The OR for LVMD between RBBB and normal ECG was 3.6. It seems that EF, rather than electrical parameters, is the main determinant of LVMD. This information might be useful when evaluating indications for cardiac resynchronization therapy.

The clinical usefulness of phase analysis in detecting coronary artery disease using dipyridamole thallium-201-gated myocardial perfusion imaging with a cadmium-zinc-telluride camera

BACKGROUND

Previous studies have demonstrated left ventricular mechanical dyssynchrony (LVMD) in patients with severe coronary artery disease (CAD) with ≥ 70% stenosis. The aim of this study was to evaluate the clinical usefulness of stress/rest LVMD in the diagnosis of CAD with ≥ 50% stenosis using dipyridamole thallium-201 (Tl-201) myocardial perfusion imaging (MPI) with a cadmium-zinc-telluride camera.

METHODS AND RESULTS

A total of 476 patients without known CAD who underwent dipyridamole Tl-201 MPI and coronary angiography within 6 months were retrospectively reviewed. LVMD parameters including phase standard deviation and phase histogram bandwidth, phase skewness and phase kurtosis, as well as myocardial perfusion and myocardial stunning were assessed in post-stress and rest MPI. Relationships between the presence of CAD on coronary angiography and single photon emission computerized tomography (SPECT) parameters were evaluated. The presence of perfusion abnormalities was the best diagnostic tool in detecting CAD. Although less left ventricular synchrony was observed post-stress in the CAD group compared to the non-CAD group, no significant dyssynchrony was noted.

CONCLUSIONS

The addition of phase analysis to help diagnose CAD in Tl-201-gated SPECT with dipyridamole stress may have limited value in patients with CAD with ≥ 50% stenosis.

Cardiac electrical and mechanical synchrony of super-responders to cardiac resynchronization therapy

BACKGROUND

Super-responders (SRs) to cardiac resynchronization therapy (CRT) regain near-normal or normal cardiac function. The extent of cardiac synchrony of SRs and whether continuous biventricular (BIV) pacing is needed remain unknown. The aim of this study was to evaluate the cardiac electrical and mechanical synchrony of SRs.

METHODS

We retrospectively analyzed CRT recipients between 2008 and 2016 in 2 centers to identify SRs, whose left ventricular (LV) ejection fraction was increased to ≥50% at follow-up. Cardiac synchrony was evaluated in intrinsic and BIV-paced rhythms. Electrical synchrony was estimated by QRS duration and LV mechanical synchrony by single-photon emission computed tomography myocardial perfusion imaging.

RESULTS

Seventeen SRs were included with LV ejection fraction increased from 33.0 ± 4.6% to 59.3 ± 6.3%. The intrinsic QRS duration after super-response was 148.8 ± 30.0 ms, significantly shorter than baseline (174.8 ± 11.9 ms, P = 0.004, t = -3.379) but longer than BIV-paced level (135.5 ± 16.7 ms, P = 0.042, t = 2.211). Intrinsic LV mechanical synchrony significantly improved after super-response (phase standard deviation [PSD], 51.1 ± 16.5° vs. 19.8 ± 8.1°, P < 0.001, t = 5.726; phase histogram bandwidth (PHB), 171.7 ± 64.2° vs. 60.5 ± 22.9°, P < 0.001, t = 5.376) but was inferior to BIV-paced synchrony (PSD, 19.8 ± 8.1° vs. 15.2 ± 6.4°, P = 0.005, t = 3.414; PHB, 60.5 ± 22.9° vs. 46.0 ± 16.3°, P = 0.009, t = 3.136).

CONCLUSIONS

SRs had significant improvements in cardiac electrical and LV mechanical synchrony. Since intrinsic synchrony of SRs was still inferior to BIV-paced rhythm, continued BIV pacing is needed to maintain longstanding and synchronized contraction.

Determination of baseline alveolar mucosa perfusion parameters using laser Doppler flowmetry and tissue spectrophotometry in healthy adults

Objectives: To determine the baseline perfusion parameters of the alveolar mucosa using laser Doppler flowmetry and tissue spectrophotometry (LDF-TS) in healthy adults.Material and methods: Forty-two healthy adult subjects of either sex were tested. The perfusion of the alveolar mucosa was evaluated using a laser Doppler flowmetry and tissue spectrophotometry using O2C 'oxygen to see' device. The measurements encompassed the maxillary and mandibular mucosa at 20 different points.Results: The O2C device is a reliable method for noninvasive measurement of different perfusion parameters of the oral mucosa. The hemoglobin saturation values (So2 in %), as well as relative amount of hemoglobin in arbitrary units (AU) of the maxillary mucosa demonstrated lower values of that in the mandible. The flow value (AU) exhibited a significant difference in the posterior molar region only, while the velocity value (AU) showed a significant difference across all points except for the anterior region.Conclusion: the present study provides a set of brand-new perfusion parameters of the microcirculation of the alveolar mucosa using LDF-TS. The study suggests a variation of the perfusion parameters between the maxilla and the mandible. Differences in the anatomy of the blood supply, the thickness of the mucosa and the cortical bone, may be attributed to this variation. Further studies using different probes and a combination of ultrasonic measurements and SDF imaging will aid in giving a better overview of the perfusion in the oral mucosa.

Evaluation of left ventricular mechanical dyssynchrony with phase analysis in end-stage renal disease patients with normal gated SPECT-MPI

Phase analysis using gated single-photon emission computed tomography myocardial perfusion imaging (SPECT-MPI) is a relatively new tool for the assessment of ventricular synchrony. Hypertension, diabetes, renal diseases, and dyslipidemia may affect the phase parameters though their impact is not well understood. The present study aimed to evaluate the incidence of the left ventricular mechanical dyssynchrony (LVMD) in end-stage renal disease (ESRD) patients with normal gated SPECT-MPI and QRS duration (<120 ms) on electrocardiogram. Data of 129 patients (86 males) referred for gated SPECT-MPI for their pretransplant evaluation with normal gated stress SPECT-MPI (SSS <3 and ejection fraction ≥50%) were included in the study analysis. Documented clinical history along with confounding factors such as hypertension, dyslipidemia, smoking, and alcoholism were evaluated. Left ventricle functional (end-diastolic, end-systolic, and LV myocardial volume) and phase parameters (phase standard deviation [PSD], phase bandwidth [PBW] and entropy) were calculated using the QPS-QGS program. LVMD was noted in 36 (28%) of ESRD patients with normal QRS duration and gated SPECT-MPI. The mean attenuated corrected LV myocardial volume, ejection fraction, mean PSD, and PBW values were 84.3 ± 38.1 ml, 65.3 ± 13.5%, 9.8° ± 3.9°, and 61.4° ± 24.7°, respectively. The LV myocardial volume shows statistically significant correlation with the phase parameters (r = 0.31-0.47; P < 0.001). LVMD is present in a significant number of ESRD patients, and its extent is more with increase in LV myocardial volume. It may have an additional role in risk-stratification for cardiovascular disease in ESRD patients.

Development and validation of a new method to diagnose apical hypertrophic cardiomyopathy by gated single-photon emission computed tomography myocardial perfusion imaging

AIM

The aim of this study is to develop and validate a new method to diagnose apical hypertrophic cardiomyopathy (AHCM) by the integral quantitative analysis of myocardial perfusion and wall thickening from gated single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI).

PATIENTS AND METHODS

Twenty-two consecutive patients, who showed T wave inversion of at least 3 mm in precordial leads and sinus rhythm in ECG, were enrolled. All the patients underwent cardiac magnetic resonance (CMR), gated rest SPECT MPI and echocardiography. According to CMR diagnostic results, 13 patients were categorized as in the AHCM group and the remaining nine patients were categorized as in the non-AHCM group. Operators who were blinded to the CMR diagnosis independently performed the diagnosis by gated SPECT MPI. The regions of interest inside the apical hotspots on the perfusion polar map were drawn and the mean values of wall thickening in the drawn region of interests were calculated. Using MRI diagnosis as the gold standard, AHCM was diagnosed based on receiver operating characteristic analysis of the mean wall thickening in the apical perfusion hotspot. The area under curve, sensitivity, specificity, and accuracy of our method were 0.97, 100%, 89%, and 95%, respectively.

CONCLUSION

Our new method has high sensitivity, specificity, and accuracy against CMR diagnosis. It has great promise to become a clinical tool in the diagnosis of AHCM.

True complete left bundle branch block reveals dyssynchrony evaluated by semiconductor single-photon emission computed tomography

BACKGROUND

Conventional complete left bundle branch block (CLBBB) criteria sometimes result in a false-positive diagnosis that does not represent dyssynchrony. Recently, true CLBBB criteria have been proposed to detect responders to cardiac resynchronization therapy (CRT), although their correlation with severity of dyssynchrony or natural prognosis is unclear.

METHODS

Ninety-four consecutive patients (74 ± 9 years, 63 men) with conventional CLBBB during sinus rhythm underwent semiconductor SPECT. They were divided into two groups: patients with true CLBBB and others. True CLBBB was characterized by the mid-QRS notching/slurring and wide QRS duration (male, ≥140 milliseconds; female, ≥130 milliseconds). Multivariate analysis was performed to detect left ventricular dyssynchrony (LVD), defined as bandwidth ≥145° and/or phase standard deviation (SD) ≥43°. Primary endpoints (hospitalization for heart failure or cardiac death) were evaluated.

RESULTS

True CLBBB had wider bandwidth (145 ± 83° vs 110 ± 64°, P = 0.024) and higher phase SD (48 ± 26° vs 35 ± 19°, P = 0.007). Ejection fraction (EF), end-diastolic volume (EDV), summed rest score (SRS), and the presence of ischemic heart disease (IHD) showed no differences between groups (P = 0.401, 0.591, 0.165, and 0.212, respectively). Multivariate analysis revealed that true CLBBB, EF, and EDV were significant predictors of LVD (odds ratio, 12.6, 0.90, 1.03; P = 0.003, 0.002, 0.022, respectively). At 3-year follow-up (median 667 days), primary endpoints were comparable in both groups (log-rank, P = 0.92).

CONCLUSIONS

Patients with true CLBBB had more severe dyssynchrony on single-photon emission computed tomography than patients with nontrue CLBBB. On the other hand, the two groups showed no differences in EF, EDV, the presence of IHD, hospitalization for heart failure, and cardiac death.

Prognostic value of left ventricular dyssynchrony evaluated by gated myocardial perfusion imaging in patients with chronic kidney disease and normal perfusion defect scores

BACKGROUND

This study aimed to investigate whether indices of left ventricular (LV) dyssynchrony by gated myocardial perfusion SPECT (GMPS) could be useful to predict prognosis in chronic kidney disease (CKD) patients with normal perfusion defect scores.

METHODS

One hundred and sixty-seven CKD patients with normal perfusion defect scores on adenosine-stress 201Tl GMPS and no previous history of overt heart diseases were enrolled. Phase standard deviation (PSD) and bandwidth (BW) were automatically calculated from GMPS. The major adverse cardiac events (MACEs) for a mean of 560 days were defined as sudden cardiac death, fatal arrhythmias, and acute coronary syndrome requiring urgent coronary revascularization. Patients were divided into two groups according to the presence or absence of MACEs.

RESULTS

The MACEs occurred in 12 patients (7.1%). Patients who experienced MACEs showed significantly higher PSD and wider BW than those who did not. In the Kaplan-Meier event-free survival analysis, cardiac event rate was significantly higher in the high-PSD and wide-BW group (n = 81) than in the low-PSD and narrow-BW group (n = 71) (P = .002). The multivariate regression analysis revealed that the PSD was associated with MACEs (odds ratio 1.33, 95% confidence interval 1.05-1.69, P = .01).

CONCLUSION

The LV dyssynchrony indices from GMPS may be novel prognostic predictors in CKD patients with normal perfusion defect scores.

Role of cardiovascular imaging in cardiac resynchronization therapy: a literature review

: Cardiac resynchronization therapy (CRT) is an established treatment in patients with symptomatic drug-refractory heart failure and broad QRS complex on the surface ECG. Despite the presence of either mechanical dyssynchrony or viable myocardium at the site where delivering left ventricular pacing being necessary conditions for a successful CRT, their direct assessment by techniques of cardiovascular imaging, though feasible, is not recommended in clinical practice by the current guidelines. Indeed, even though there is growing body of data providing evidence of the additional value of an image-based approach as compared with routine approach in improving response to CRT, these results should be confirmed in prospective and large multicentre trials before their impact on CRT guidelines is considered.

The role of nuclear medicine in assessments of cardiac dyssynchrony

Radionuclide imaging has an advantage for quantitative analyses of the tracer concentration and its temporal changes. Myocardial perfusion and function have been adapted for synchrony analyses. Extracted parameters have been demonstrated to measure ventricular synchrony and even to predict CRT outcomes. ERNA has the advantages of higher temporal resolution, greater reproducibility, and the volumetric analysis of both ventricles that can be applied for analyses of intraventricular synchrony and interventricular synchrony. Several software packages such as Quantitative Gated SPECT, the Emory Cardiac Toolbox, cardioREPO, and Heart Function View are available to assess the LV dyssynchrony parameters from GSPECT. A count-based method is applied to extract the amplitude and phase from each of the reconstructed GSPECT short-axis datasets throughout the cardiac cycle and then subjected to a Fourier analysis, the results of which are displayed on a polar map and histogram. Some of the parameters such as the bandwidth (expressed as the 95% width of the phase histogram) and the standard deviation of the phase are obtained by the phase histogram to assess the intraventricular synchrony. This review paper focuses on the application of the LV dyssynchrony parameters estimated by cardiac SPECT in patients with a heart disease.

Mechanical dyssynchrony according to validated cut-off values using gated SPECT myocardial perfusion imaging

BACKGROUND

The aim of this study was to establish different degrees of mechanical dyssynchrony according to validated cut-off (CO) values of myocardial perfusion gated SPECT phase analysis parameters (SD, standard deviation; B, bandwidth; S, skewness; K, kurtosis).

METHODS

Using Emory Cardiac Toolbox™, we prospectively analyzed 408 patients (mean age 64.1 years, 26.7% female), divided into a control group of 150 normal subjects and a validation group of 258 patients (left bundle branch block: 17.8%, right bundle branch block: 8.9%. atrial fibrillation: 16.3%, coronary revascularization: 30%, dilated cardiomyopathy: 7.4%. valvulopathies: 2.7%, ischemic test: 45.3%) with ischemic and non-ischemic cardiac diseases, by means of phase analysis.

RESULTS

Agreement of CO values (SD > 18.4°; B > 51°; S ≤ 3.2; K ≤ 9.3) used to discriminate between normal subjects and patients was strong (c-statistic 0.9; 95% CI 0.98-0.99). Four degrees of dyssynchrony were found according to the number of abnormal phase parameters. All patients with mechanical and electrical criteria for cardiac resynchronization therapy (CCRT) (n: 82) had Grade 2 to 4 (two to four abnormal phase parameters). Agreement of CO values (SD > 40.2°; B > 132°; S ≤ 2.3; K ≤ 4.6) used to discriminate between patients with and without CCRT was strong (c-statistic 0.8; 95% CI 0.79-0.87) but 12% of patients with CCRT did not have any of these abnormal phase parameters.

CONCLUSIONS

The discriminatory capacity of gated SPECT phase analysis parameters between normal subjects and patients, and between patients with and without CCRT, is very good, making it possible to define different degrees of mechanical dyssynchrony.

Assessment of dyssynchrony by gated myocardial perfusion imaging does not improve patient management

Clinical trials have demonstrated improved outcomes with cardiac resynchronization therapy in patients with heart failure and electrical evidence of dyssynchrony. There has been intense effort at developing imaging markers of dyssynchrony with the aim of improved risk stratification. However, these efforts have not been fruitful to date. This article discusses mechanisms of cardiac dyssynchrony, reviews clinical data supporting resynchronization therapy, and addresses the lack of convincing evidence to support the use of noninvasive imaging measures of dyssynchrony in improving patient management.

Mechanical dyssynchrony and diastolic dysfunction are common in LVH: a pilot correlation study using Doppler echocardiography and CZT gated-SPECT MPI

Hypertrophic cardiomyopathy (HCM) is an often under-diagnosed cause of left ventricular hypertrophy (LVH). It affects 1/500 of the population, is the most commonly inherited cardiovascular disorder, and can present in apical, concentric, or septal forms. Although most patients are asymptomatic, sudden cardiac death can be the initial presentation of HCM. By retrospectively enrolling patients suspected of having three different types of HCM in the absence of epicardial coronary stenosis, we aimed to examine systolic and diastolic dysfunction and perfusion abnormalities using both Doppler echocardiography and state-of-the-art gated single-photon emission computerized tomography (SPECT) myocardial perfusion imaging (MPI) with a cadmium-zinc-telluride camera and thallium-201. Both regional perfusion and gated SPECT parameters were collected in addition to diastolic parameters from Doppler echocardiography. The results showed that mild ischemia was common in patients suspected of having HCM, with a mean summed stress score of 4.7 ± 4.9 (score 0–4 in 17-segment model). The patients with HCM were associated with discernible left ventricular mechanical dyssynchrony, especially those with the apical form. In addition, diastolic dysfunction was prevalent and early to late ventricular filling velocity ratios were significantly different between groups. By combining gated-MPI and Doppler data, the trivial functional changes in HCM may be identified.

The incidence and outcomes of delayed response to cardiac resynchronization therapy

BACKGROUND

The incidence and clinical outcomes of delayed response to cardiac resynchronization therapy (CRT) have not been well clarified. We aimed to observe the incidence and prognosis of delayed response and to identify its possible mechanisms.

METHODS

A total of 115 CRT patients were retrospectively analyzed in our study. Patients who met the enrollment criteria were divided into two groups: group A, conventional responders who showed response at 1-year follow-up, and group B, delayed responders who showed response after 1-year follow-up. CRT response was defined as an absolute increase of ≥10% in left ventricular ejection fraction.

RESULTS

Fifty-two patients (61 ± 12 years, 37 male) experienced conventional response to CRT and 17 patients (63 ± 11 years, 10 male) experienced delayed response. The mean follow-up time was 5.2 ± 2.4 years. The incidence of delayed response was 14.8% (17/115). All-cause mortality and hospitalization rates for heart failure were similar for delayed and conventional responders. Multivariate logistic regression analysis revealed that scar burden > 35% was an independent predictor of CRT delayed response (odds ratio 8.794, P  =  0.038).

CONCLUSIONS

A significant proportion of patients demonstrated delayed response to CRT. The delayed responders had a good prognosis that was similar to that of conventional responders. More scar burden might be related to the incidence of delayed response.

Development and validation of a phase analysis tool to measure interventricular mechanical dyssynchrony from gated SPECT MPI

OBJECTIVES

The purpose of this study is to develop a right-ventricular (RV) phase analysis tool which when coupled with our left ventricular (LV) phase analysis tool can provide measurement of the interventricular mechanical dyssynchrony from gated SPECT myocardial perfusion imaging (MPI), and validate the tool by electrocardiography (ECG).

METHODS

For each patient, short-axis LV and RV SPECT MPI images were input into an automatic sampling algorithm to generate the 3D maximal count circumferential profiles for both LV and RV in each cardiac frame. Subsequently, the samples of LV and RV were separately used by our phase analysis tool based on the first-harmonic Fourier approximation to calculate the contraction onset for each sample. The difference between contraction onsets of the middle LV free wall and middle LV septal wall represented the LV contraction delay; the difference between contraction onsets of the middle RV free wall and middle RV septal wall represented the RV contraction delay. The difference between the LV and RV contraction delays represented the interventricular contraction delay, which was compared with the interventricular conduction delay classified by ECG to validate the concordance of interventricular mechanical and electrical dyssynchrony. Sixty-one bundle branch block (BBB) patients with ischemic-dilated cardiomyopathy (26, 42.6%) or non-ischemic-dilated cardiomyopathy (35, 57.4%), who underwent 12-lead surface ECG and gated resting Tc-99m sestamibi SPECT, were retrospectively analyzed in this study.

RESULTS

In the 30 patients with left bundle branch block (LBBB) by ECG, there were 27 patients whose LV contracted later than the RV according to SPECT; and in the 31 patients with right bundle branch block (RBBB) by ECG, there were 26 patients whose LV contracted earlier than the RV according to SPECT. In total, an agreement rate of 86.9% (53 of 61) was achieved between SPECT and ECG. The Kappa agreement rate was 73.8% (95% confidence interval 0.57-0.91).

CONCLUSION

The preliminary results showed promise for the measurement of interventricular mechanical dyssynchrony in BBB patients with dilated cardiomyopathy using our phase analysis tool.