Prevalence and predictors of mechanical dyssynchrony as defined by phase analysis in patients with left ventricular dysfunction undergoing gated SPECT myocardial perfusion imaging

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.

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.

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.

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.

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.

Association between non-perfusion parameters and presence of ischemia in gated-SPECT myocardial perfusion imaging studies

BACKGROUND

Combined assessment of perfusion and function improves diagnostic and prognostic power of gated-SPECT in patients with coronary artery disease. The aim of this study was to investigate whether the presence of stress-induced ischemia is associated with abnormal resting left ventricular (LV) function and intraventricular dyssynchrony.

METHODS AND RESULTS

Gated-SPECT myocardial perfusion imaging (MPI) at rest and 15 min post-stress was performed in 101 patients, who were divided into three groups: those with stress-induced ischemia (Group 1, n = 58), those with normal scans (Group 2, n = 28), and those with scar but no ischemia (Group 3, n = 15). More extensive perfusion defects were found in patients of Groups 1 and 3 [Summed stress score (SSS): 13 ± 8 and 21 ± 9, respectively]. In Group 2, the mean SSS was 1.5. The mean change in LV ejection fraction (LVEF at stress - LVEF at rest) was higher in Group 1 v. Group 2 patients: -5.54% ± 6.24% vs -2.46% ± 5.56%, p = 0.02. Group 3 patients also had higher values, similar to Group 1: -6.47% ± 8.82%. Patients with ischemia had almost 50% higher end-diastolic volumes than patients with normal MPI. Similarly, end-systolic volumes were almost twice as high in this group (p < 0.0001). In addition, the histogram bandwidth, a measure of intraventricular dyssynchrony, was greater in Group 1.

CONCLUSIONS

Baseline differences in left ventricular volumes and degree of dyssynchrony are associated with inducible ischemia on stress testing in a gated-SPECT MPI. Stress-induced ischemia increases the degree of intraventricular dyssynchrony.

Is there an association between hibernating myocardium and left ventricular mechanical dyssynchrony in patients with myocardial infarction?

OBJECTIVE

Left ventricular mechanical dyssynchrony (LVMD) is an important factor in the prognosis of patients with myocardial infarction (MI). The aim of this study is to identify the influencing factors of LVMD in MI patients by radionuclide myocardial imaging.

SUBJECTS AND METHODS

This study consisted of 91 patients who had a history of definite prior MI and underwent both technetium-99m methoxyisobutylisonitrile (99mTc-MIBI) gated single photon emission tomography (SPET) myocardial perfusion imaging (MPI) and 18F-FDG positron emission tomography (PET) myocardial metabolic imaging. Left ventricular (LV) functional and LVMD parameters were measured from gated SPET MPI, while myocardial viability was assessed by the integral quantitative analysis of SPET MPI and 18F-FDG PET. Left ventricular MD was defined as >mean+2SD of phase bandwidth (PBW) in the control group.

RESULTS

Left ventricular MD was present in 37/91 (40.7%) MI patients. Hibernating myocardium (SPET/PET mismatch) and scar in patients with LVMD were significantly higher than those without LVMD (15.24±11.26% vs 4.89±5.41%, P<0.001; 11.11±9.42% vs 4.72±5.71%, P<0.001; respectively). PBW correlated with hibernating myocardium and scar (r=0.542, 0.469, P<0.001; respectively). The multivariate logistic regression analysis showed that hibernating myocardium was an independent factor of LVMD in MI patients (OR=1.110, P=0.009), and >6.5% hibernating myocardium as a threshold can be used to better discriminate LVMD. In addition, the improvement of PBW (ΔPBW) after CABG at a median follow-up time of 6 months was related with the amount of hibernating myocardium.

CONCLUSION

Myocardial infarction patients with LVMD show significantly more segments of larger amounts of hibernating myocardium and scars as compared to those without LVMD. Hibernating myocardium is independently associated with LVMD in MI patients.

Yield of left ventricular dyssynchrony by gated SPECT MPI in patients with heart failure prior to implantable cardioverter-defibrillator or cardiac resynchronization therapy with a defibrillator: Characteristics and prediction of cardiac outcome

BACKGROUND

Mechanical left ventricular dyssynchrony (MLVD) might contribute in the therapeutic decision-making in patients with heart failure (HF) prior to cardiac resynchronization therapy (CRT). Our aim was to assess MLVD in patients with HF prior to implantable cardioverter-defibrillator (ICD) compared to patients with CRT-D.

METHODS

In a prospective study, patients with LVEF ≤ 35% who were scheduled for ICD or CRT-D, underwent gated SPECT myocardial perfusion imaging with technetium 99m sestamibi within 3 months prior procedure. MLVD was measured by phase analysis.

RESULTS

The study cohort consisted of 143 patients, 71 with ICD and 72 with CRT-D. Age 68.3 ± 11 and LVEF 24 ± 6%. Phase standard deviation (SD) was 62.5 ± 18 and 59.7 ± 20 (P = NS), respectively. During follow-up of 23.7 ± 12.1 months, there were 10 vs 14 cardiac death in ICD and CRT-D, respectively (P = NS), hospitalization for HF, in 34 vs 53 (P < .001). In multivariate analysis, Phase SD was the independent predictor for cardiac death [HR 2.66 (95% CI 1.046-6.768), P = .04]. Kaplan-Meier curves of phase SD of 60° significantly identified ICD patients with and without cardiac deaths and hospitalization for HF exacerbation.

CONCLUSIONS

MLVD by phase SD can identify patients with cardiac events and predict cardiac death in patients treated with ICD.

Left ventricular scar impact on left ventricular synchronization parameters and outcomes of cardiac resynchronization therapy

BACKGROUND

Left ventricular scar, including global scar and lateral wall, plays an important role in predicting response to cardiac resynchronization therapy (CRT).

MATERIALS AND METHODS

Thirty patients underwent CRT implantation. Assessment of left ventricular (LV) dyssynchrony was done through Gated SPECT LV phase analysis. Pre-implantation cardiac magnetic resonance (CMR) with late gadolinium enhancement technique to examine LV scar burden. Echocardiographic examination of LV end-systolic volume (LVES) prior to CRT and 6 months later.

RESULTS

Thirty patients received CRT (mean age 58.7±9.0, 24 males). Reverse LV remodeling (decline ≥15% from baseline VES) was documented in 19 patients. Temporal changes in LV dyssynchrony parameters were correlated to LV reverse remodeling. Applying ROC for predicting CRT non-response showed a cutoff 36.5% of global LV scar burden had a sensitivity of 81.8% and specificity of 68.4%. A cutoff for lateral wall scar burden 40.5% of whole lateral wall had a sensitivity of 72.7% and specificity of 68.4%.

CONCLUSION

Reverse LV remodeling is associated with temporal improvements in LV dyssynchrony parameters. LV scar had an unfavorable impact on CRT response. Both global and lateral wall scar burden could predict CRT nonresponse status.

Prevalence and predictors of left intraventricular dyssynchrony determined by phase analysis in patients undergoing gatedSPECT myocardial perfusion imaging

Left ventricular dyssynchrony (LVD) is an independent predictor of adverse cardiovascular events, death, and progression to heart failure. Myocardial perfusion imaging (MPI) with ECG-gated single-photon emission computed tomography (SPECT) can be used to diagnose LVD rapidly and automatically using phase analysis (PA). The objective of this study was to evaluate the prevalence and predictors of LVD in patients undergoing MPI. Clinical, electrocardiographic, and scintigraphic data from 1000 patients who underwent MPI with ECG-gated SPECT over a period of 1 year were analyzed retrospectively. TheEmoryCardiac Toolboxsoftware was used for PA, and LVD was diagnosed based on the following criteria: standard deviation of LV phase distribution ≥43° and/or phase histogram ≥140° in the resting and/or stress phase of the examination. Several variables were evaluated using univariate and multivariate analyses. The prevalence of LVD in the study population was 6.5 %, and the average age was 63.6 ± 12 years. The variables significantly associated with LVD were male gender, obesity, hypertension, diabetes, dyslipidemia, coronary artery disease (CAD), QRS interval ≥120 ms, LV dysfunction, and myocardial perfusion defects (especially fixed defects) on MPI. Although the PA parameters were greater at rest, both phases could be used for diagnosis. Multivariate analysis revealed that the variables significantly associated with LVD were male sex, obesity, history of CAD, and QRS interval ≥120 ms. The overall prevalence of LVD was 6.5 % in patients undergoing MPI in this study, and it reached 42 % in the presence of certain risk factors.

Nuclear Image-Guided Approaches for Cardiac Resynchronization Therapy (CRT)

Cardiac resynchronization therapy (CRT) is a standard treatment for patients with heart failure. However, 30-40 % of the patients having CRT do not respond to CRT with improved clinical symptom and cardiac functions. It is important for CRT response that left ventricular (LV) lead is placed away from scar and at or near the site of the latest mechanical activation. Nuclear image-guided approaches for CRT have shown significant clinical value to assess LV myocardial viability and mechanical dyssynchrony, recommend the optimal LV lead position, and navigate the LV lead to the target coronary venous site. All these techniques, once validated and implemented, should impact the current clinical practice.

Prognostic value of left ventricular dyssynchrony by myocardial perfusion-gated SPECT in patients with normal and abnormal left ventricular functions

BACKGROUND

Left ventricular (LV) dyssynchrony by phase analysis has been studied by myocardial perfusion imaging (MPI)-gated SPECT in patients with LV dysfunction in various clinical settings. We aimed to investigate the routine use of phase analysis with gated SPECT for predicting cardiac outcome.

METHODS

Patients referred to a tertiary medical center in 2010-2011 prospectively underwent a gated SPECT and phase analysis, and follow-up for cardiac events. The values of clinical variables, MPI, LV function, and LV dyssynchrony in predicting cardiac events were tested by univariate and multivariate analyses.

RESULTS

The study group included 787 patients (66.5 ± 11 years, 81% men) followed for a mean duration of 18.3 ± 6.2 months. There were 45 (6%) cardiac events defined as composite endpoint; cardiac death occurred in 26 patients, and the rest had new-onset or worsening heart failure and life-threatening arrhythmias. In multivariate analysis, it was shown that NYHA class, diabetes mellitus, and LVEF <50% were the independent predictors for composite endpoint. However, the independent predictors for cardiac mortality were NYHA class (for each increment in class) and phase standard deviation (SD) (for each 10° increment).

CONCLUSION

Gated SPECT with phase analysis for the assessment of LV dyssynchrony can successfully predict cardiac death together with NYHA class, in patients with LV dysfunction.

Update on cardiac imaging techniques 2012

Cardiac imaging is one of the basic pillars of modern cardiology. The potential list of scenarios where cardiac imaging techniques can provide relevant information is simply endless so it is impossible to include all relevant new features of cardiac imaging published in the literature in 2012 in the limited format of a single article. We summarize the year's most relevant news on cardiac imaging, highlighting the ongoing development of myocardial deformation and 3-dimensional echocardiography techniques and the increasing use of magnetic resonance imaging and computed tomography in daily clinical practice.

Gated SPECT myocardial perfusion imaging, intraventricular synchronism, and cardiac events in heart failure

PURPOSE

The purpose of this study was to evaluate the ability of rest gated SPECT myocardial perfusion imaging (MPI) and intraventricular synchronism, to identify heart failure (HF) patients most likely to experience cardiac events.

METHODS

We studied 165 patients with left ventricular ejection fraction of less than 40%, who were divided in 2 groups according to the diagnosis of coronary artery disease (group 1: 136 patients) or not (group 2: 29 patients). All underwent a rest gated SPECT MPI.

RESULTS

In 160 patients, the MPI was abnormal. Mean summed rest score was 17 ± 6 (group 1) versus 10 ± 6 (group 2), P < 0.0001. Mean volumes showed a marked ventricular dilation, slightly higher among nonischemic. The mean value of the phase-derived SD was 70 ± 19 (group 1) versus 59 ± 21 degrees (group 2), P = 0.016. The histogram bandwidth showed no significant differences. Forty-four (39%) of 114 patients showed some kind of event during the follow-up. The more frequent events were HF progression (13%) and acute coronary syndrome (11%). The highest odds ratios for prediction of events were 1.91 (phase SD), 1.66 (etiology), and 1.55 (summed rest score), although the association was not significant.

CONCLUSIONS

A rest gated SPECT is a valid approach to identify HF patients most likely to experience cardiac events.

Sites of latest mechanical activation as assessed by SPECT myocardial perfusion imaging in ischemic and dilated cardiomyopathy patients with LBBB

OBJECTIVE

Sites of latest mechanical activation (SOLA) have been recognized as optimal left-ventricular (LV) lead positions for cardiac resynchronization therapy (CRT). This study was aimed to investigate SOLA in ischemic cardiomyopathy (ICM) and dilated cardiomyopathy (DCM) patients with left bundle branch block (LBBB).

METHODS

Sixty-four consecutive LBBB patients (47 DCM, 17 ICM), who met the standard indications for CRT and underwent resting SPECT myocardial perfusion imaging (MPI), were selected. Phase analysis was used to assess LV dyssynchrony and SOLA. The Emory Cardiac Toolbox was used to measure perfusion defects. LV dyssynchrony and SOLA were compared between the DCM patients with wide (≥150 ms) and moderate (120-150 ms) QRS durations (QRSd). The relationship between SOLA and perfusion defects was analyzed in the ICM patients.

RESULTS

The DCM patients with wide QRSd had significantly more LV dyssynchrony than those with moderate QRSd. Lateral SOLA were significantly more frequent in the DCM patients with wide QRSd than those with moderate QRSd (96% vs. 62%, p = 0.010). In the ICM patients, SOLA were either in the scar segments (82%) or in the segments immediately adjacent to the scar segments (18%), regardless of QRSd.

CONCLUSION

Lateral SOLA were more frequent in the DCM patients with wide QRSd than those with moderate QRSd. Such relationship was not observed in the ICM patients, where SOLA were associated with scar location rather than QRSd. These findings support the use of SPECT MPI to aid the selection of potential CRT responders and guide LV lead placement.

Prognostic value of left ventricular mechanical dyssynchrony by phase analysis in patients with non-ischemic cardiomyopathy with ejection fraction 35-50% and QRS < 150 ms

BACKGROUND

Left ventricular mechanical dyssynchrony (LVMD) by phase analysis of gated single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) is a useful tool for predicting response to cardiac resynchronization therapy and has prognostic value. While most of the studies were done on patients with ischemic cardiomyopathy or those with LV ejection fraction (EF) < 35%, there are little data on the prognostic value of LVMD in patients with non-ischemic cardiomyopathy (NICM), particularly those with mildly decreased systolic function and narrow or intermediate QRS duration.

METHODS AND RESULTS

From the stress SPECT-MPI database at Cleveland Clinic, we identified 324 consecutive patients (mean age 62 ± 13 years, 62% male, 36% diabetics) with NICM, LVEF 35-50% (median [Q1,Q3] 45 [41,49]), and QRS < 150 ms (13% with QRS 120-149 ms). LVMD was determined from gated stress images and expressed as phase standard deviation (SD) and histogram BW (% R-R cycle). For easier graphical illustration, patients were divided into tertiles of LVMD. All-cause death was the primary endpoint and determined using the Social Security Death Index. Cox proportional hazard model was performed to determine the independent predictive value of LVMD, and next Cox models for incremental value. After a mean follow-up time of 1,689 days, 86 (26.5%) of patients died. These patients were older, had more diabetes, more use of diuretics, with wider QRS duration, and with a trend for higher phase SD and BW. After adjusting for age, hypertension, diabetes, aspirin, beta-blockers, diuretics, QRS, and EF, phase SD was an independent predictor of all-cause mortality with hazard ratio [95% CI] 1.97 [1.06,3.66] for the highest tertile, and added incremental prognostic value (P = .025). Similar findings were obtained using histogram BW.

CONCLUSION

In patients with NICM, EF 35-50%, and QRS < 150 ms, increased LVMD on peak stress SPECT was an independent predictor of all-cause mortality. The utility and applicability of such findings in clinical practice need further evaluation in larger and prospective studies.

Impact of myocardial viability assessed by myocardial perfusion imaging on ventricular tachyarrhythmias in cardiac resynchronization therapy

BACKGROUND

The presence of myocardial fibrosis is associated with ventricular tachyarrhythmia (VT) occurrence irrespective of cardiomyopathy etiology. The aim of our study was to evaluate the impact of global and regional viability on VTs in patients undergoing cardiac resynchronization therapy (CRT).

METHODS

Fifty-seven patients with advanced heart failure (age 62.3 ± 10.2; 38 men; 24 ischemic etiology) were evaluated using single-photon emission computed tomography myocardial perfusion imaging before CRT defibrillator device implantation. Global myocardial viability was determined by the number of viable segments in a 20-segment model. Regional viability was calculated as the mean tracer activity in the corresponding segments at left ventricular (LV) lead position. LV lead segments were determined at implant venography using 2 projections (left anterior oblique 30 and right anterior oblique 30) of coronary sinus tributaries. Patients were followed 30 (24-34) months for the occurrence of VTs.

RESULTS

VTs were registered in 18 patients (31.6%). Patients without VTs had significantly more viable segments (17.6 ± 2.35 vs 14.2 ± 4.0; P = .002) and higher regional myocardial viability at LV lead position (66.1% ± 10.3% vs 54.8% ± 11.4% of tracer activity; P = .001) than those with VTs. In multivariate logistic regression models, the number of viable segments (OR = 0.66; 95% confidence interval (CI) 0.53-0.85; P = .001) and regional viability (OR = 0.90; 95% CI 0.85-0.97; P = .003) were the only independent predictors of VT occurrence.

CONCLUSION

Global and regional myocardial viability are independently related to the occurrence of VTs in patients after CRT.

Left ventricular mechanical dyssynchrony in patients with impaired left ventricular function undergoing gated SPECT myocardial perfusion imaging

INTRODUCTION

Gated SPECT myocardial perfusion imaging (MPI) has been used to quantify mechanical dyssynchrony. Mechanical dyssynchrony appears to be related to response to cardiac resynchronization therapy.

OBJECTIVE

To evaluate the presence and predictors of mechanical dyssynchrony in patients with impaired left ventricular function (LVEF) ≤50%.

METHODS

The study included 143 consecutive patients referred for gated SPECT MPI with LVEF ≤50%. Gated SPECT MPI was performed according to a stress/rest protocol acquiring images with Tc 99m-tetrofosmin. Emory Cardiac Toolbox software was used for phase analysis and a standard deviation (SD) ≥43° was considered to indicate mechanical dyssynchrony.

RESULTS

Mechanical dyssynchrony was present in 53.1% of the patients. Its predictors were diabetes (OR 2.0, p≤0.05), summed stress score (OR 1.1, p≤0.0005), summed rest score (OR 1.1, p≤0.0001), end-diastolic volume (OR 1.0, p≤0.0001), LVEF (OR 0.9, p≤0.0001), LVEF ≤35% (OR 3.1, p≤0.005) and LVEF ≤35% and QRS ≥120 ms (OR 3.5, p≤0.05). In this study QRS width and QRS ≥120 ms were not predictors of mechanical dyssynchrony.

CONCLUSIONS

Myocardial perfusion imaging can be used to assess mechanical dyssynchrony. In patients with impaired ventricular function mechanical dyssynchrony was highly prevalent and was related to parameters of left ventricular function and perfusion.

Association between left ventricular mechanical dyssynchrony with myocardial perfusion and functional parameters in patients with left bundle branch block

OBJECTIVE

To identify predictors of left ventricular mechanical dyssynchrony (LVMD) in patients with known left bundle branch block (LBBB) using gated single-photon emission computed tomography (SPECT) phase analysis.

METHODS

81 patients (74% male, 70 ± 10 years) with LBBB and suspected or known coronary artery disease underwent ECG-gated myocardial perfusion SPECT. LV perfusion and functional parameters were measured, and phase analysis was performed to quantify LV-dyssynchrony.

RESULTS

35/81 patients (42%) had prior myocardial infarction (MI), and the mean left ventricular ejection fraction (LVEF) was 49% ± 16%. LVMD was present in 58/81 (72%) patients. The summed thickening score (STS) (P < .001; odds ratio 1.22) emerged as independent predictor for the presence of LVMD in a multivariate regression model. In addition, prior MI, low LVEF, summed stress score, summed rest score, summed motion score, and LAD rest extent were identified as predictors of LVMD in a univariate model. Clinical baseline characteristics, cardiac risk factors, and QRS duration (P = .051) had no influence on the presence of LVMD.

CONCLUSION

In patients with LBBB, the occurrence of LVMD as assessed by gated SPECT phase analysis is mainly influenced by reduced myocardial contractility as expressed by the STS. Proper discrimination between LVMD arising from known electrical conduction delay as opposed to areas of MI causing reduced regional contractility seems to be mandatory for therapy planning in patients with LVMD.

Effect of tracer dose on left ventricular mechanical dyssynchrony indices by phase analysis of gated single photon emission computed tomography myocardial perfusion imaging

BACKGROUND

There are limited data on the effect of tracer dose on the reproducibility and accuracy of left ventricular (LV) mechanical dyssynchrony indices by phase analysis of gated single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI).

METHODS AND RESULTS

We measured LV dyssynchrony in 54 patients with normal LV ejection and perfusion (group 1) and 54 age and gender matched patients with LV ejection <35% (group 2) using phase analysis of gated SPECT MPI from stress (high dose) and rest (low dose) studies with 2 software programs: Corridor4DM (4DM) and Emory Cardiac Toolbox (ECTb). Although the correlation between rest- and stress-derived standard deviation was good (R = 0.76, P < .0001, with both software programs), there was considerable variability between the measurements (P < .0001 by paired t test). In addition, the rest standard deviation was significantly higher than stress in group 1 (10.2° ± 4.6° vs 6.1° ± 2.5°, and 12.2° ± 6.4° vs 7.9° ± 4.6°, with 4DM and ECTb, respectively, P < .0001 for both) and group 2 patients (44.0° ± 18.0° vs 35.9° ± 21.0° and 47.3° ± 19.2° vs 38.8° ± 19.8°, with 4DM and ECTb, P = .03 and .02, respectively). Similarly, the rest standard deviations were higher than the stress values irrespective of the type of stress test (i.e., exercise vs pharmacological), and the body mass index. Finally, using rest-derived dyssynchrony indices was associated with 9%-13% and 22%-26% false positive rate of significant mechanical dyssynchrony using different cut-off values for groups 1 and 2, respectively.

CONCLUSION

LV mechanical dyssynchrony indices by phase analysis have more variation and are significantly higher if derived from rest gated SPECT images obtained with low-dose tracer.

SPECT myocardial perfusion imaging for the assessment of left ventricular mechanical dyssynchrony

Phase analysis of gated single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) is an evolving technique for measuring LV mechanical dyssynchrony. Since its inception in 2005, it has undergone considerable technical development and clinical evaluation. This article reviews the background, the technical and clinical characteristics, and evolving clinical applications of phase analysis of gated SPECT MPI in patients requiring cardiac resynchronization therapy or implantable cardioverter defibrillator therapy and in assessing LV diastolic dyssynchrony.