Prognostic value of myocardial MIBG scintigraphy findings in patients with cardiomyopathy--importance of background correction for quantification of MIBG activity

Late gadolinium enhancement on cardiac magnetic resonance combined with 123I- metaiodobenzylguanidine scintigraphy strongly predicts long-term clinical outcome in patients with dilated cardiomyopathy

Late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) is limited in its ability to detect diffuse interstitial fibrosis, which is commonly found in idiopathic dilated cardiomyopathy (DCM). On the other hand, Washout rate (WR) by cardiac ¹²³I- metaiodobenzylguanidine (¹²³I-MIBG) scintigraphy which evaluates cardiac sympathetic nervous function, is a useful tool for predicting the prognosis in DCM. We investigated the predictive value of the combination of two different types of examinations, LGE on CMR and WR by ¹²³I-MIBG scintigraphy for outcomes in DCM compared with LGE alone. One-hundred forty-eight DCM patients underwent CMR and ¹²³I-MIBG scintigraphy. Patients were divided into 4 groups according to the presence or absence of LGE and WR cut-off value of 45% for predicting prognosis based on receiver operating characteristic curve analysis. Cardiac deaths, re-hospitalization for heart failure, implantation of a left ventricular assist device, and life-threatening ventricular arrhythmias were defined as clinical events. Forty-two DCM patients reached the clinical events during the median follow-up for 9.1 years (interquartile range, 8.0–9.2 years).Multivariable Cox regression analysis identified WR≥45%+LGE positive group as an independent predictor of cardiac events (HR 3.18, 95%CI 1.36–7.45, p = 0.008). Notably, there was no significance in the cardiac event-free survival rate between the WR<45%+LGE positive and WR≥45%+LGE negative groups (p = 0.89). The combination of WR by ¹²³I-MIBG scintigraphy and LGE on CMR, which evaluate different type of cardiac deterioration, serves as a stronger predictor of long-term outcomes in DCM patients than LGE alone.

Adaptive servo-ventilation therapy improves cardiac sympathetic nerve activity, cardiac function, exercise capacity, and symptom in patients with chronic heart failure and Cheyne-Stokes respiration

PURPOSE

Adaptive servo-ventilation (ASV) therapy has been reported to be effective for improving central sleep apnea (CSA) and chronic heart failure (CHF). The purpose of this study was to clarify whether ASV is effective for CSA, cardiac sympathetic nerve activity (CSNA), cardiac symptoms/function, and exercise capacity in CHF patients with CSA and Cheyne-Stokes respiration (CSR-CSA).

METHODS

In this study, 31 CHF patients with CSR-CSA and a left ventricular ejection fraction (LVEF) ≤ 40% were randomized into an ASV group and a conservative therapy (non-ASV) group for 6 month. Nuclear imagings with 123I-Metaiodobenzylguanidine (MIBG) and 99mTc-Sestamibi were performed. Exercise capacity using a specific activity scale (SAS) and the New York Heart Association (NYHA) class were evaluated. CSNA was evaluated by 123I-MIBG imaging, with the delayed heart/mediastinum activity ratio (H/M), delayed total defect score (TDS), and washout rate (WR).

RESULTS

The ASV group had significantly better (P < .05) results than the non-ASV group with respect to the changes of AHI (-20.8 ± 14.6 vs -0.5 ± 8.1), TDS (-7.9 ± 4.3 vs 1.4 ± 6.0), and H/M(0.16 ± 0.16 vs -0.04 ± 0.10) on 123I-MIBG imaging, as well as the changes of LVEF (5.3 ± 3.9% vs 0.7 ± 32.6%), SAS (1.6 ± 1.4 vs 0.3 ± 0.7), and NYHA class (2.2 ± 0.4 vs 2.7 ± 0.5) after 6-month therapy.

CONCLUSIONS

Performing ASV for 6 months achieved improvement of CSR-CSA, CSNA, cardiac symptoms/function, and exercise capacity in CHF patients with CSR-CSA.

Prognostic Value of Lymphocyte G Protein-Coupled Receptor Kinase-2 Protein Levels in Patients With Heart Failure

RATIONALE

Sympathetic nervous system hyperactivity is associated with poor prognosis in patients with heart failure (HF), yet routine assessment of sympathetic nervous system activation is not recommended for clinical practice. Myocardial G protein-coupled receptor kinase-2 (GRK2) is upregulated in HF patients, causing dysfunctional β-adrenergic receptor signaling. Importantly, myocardial GRK2 levels correlate with levels found in peripheral lymphocytes of HF patients.

OBJECTIVE

The independent prognostic value of blood GRK2 measurements in HF patients has never been investigated; thus, the purpose of this study was to evaluate whether lymphocyte GRK2 levels predict clinical outcome in HF patients.

METHODS AND RESULTS

We prospectively studied 257 HF patients with mean left ventricular ejection fraction of 31.4±8.5%. At the time of enrollment, plasma norepinephrine, serum NT-proBNP, and lymphocyte GRK2 levels, as well as clinical and instrumental variables were measured. The prognostic value of GRK2 to predict cardiovascular (CV) death and all-cause mortality was assessed using the Cox proportional hazard model including demographic, clinical, instrumental, and laboratory data. Over a mean follow-up period of 37.5±20.2 months (range, 3-60 months), there were 102 CV deaths. Age, left ventricular ejection fraction, New York Heart Association class, chronic obstructive pulmonary disease, chronic kidney disease, N-terminal-pro brain natriuretic peptide, and lymphocyte GRK2 protein levels were independent predictors of CV mortality in HF patients. GRK2 levels showed an additional prognostic and clinical value over demographic and clinical variables. The independent prognostic value of lymphocyte GRK2 levels was also confirmed for all-cause mortality.

CONCLUSIONS

Lymphocyte GRK2 protein levels can independently predict prognosis in patients with HF.

[Validation of an optimal analysis method and reproducibility to calculate the heart-to-mediastinum ratio and washout rate in the iodine-123-labeled metaiodobenzylguanidine myocardial scintigraphy]

PURPOSE

The aim of this study was to investigate an appropriate analysis method and multicenter reproducibility of heart-to-mediastinum ratio (H/M) and washout rate (WR) in iodine-123-labeled metaiodobenzylguanidine (123I-MIBG) myocardial scintigraphy with a phantom.

METHODS

We evaluated the optimal region of interest (ROI) setting method about the mediastinum and heart by varying the position and shape of the ROI. The mathematical method was changed to a combination of decay time correction (DTC) and background correction (BC). We evaluated the reproducibility of the H/M and WR between institutions.

RESULT

H/M decreased to 23.49% and WR increased to 20.68% by changing the mediastinum ROI position from upper to lower. H/M increased to 26.03% by changing the heart ROI position from base to apex. H/M decreased to 38.36% with BC, and WR was reduced up to 48.51% with DTC. Reproducibility of the H/M and WR between institutions was improved by performing optimization of the ROI setting and unification of the mathematical method.

DISCUSSION

The position of the mediastinum ROI should be set on the upper mediastinum. The position of the heart ROI should be set on the apex of the heart. WR should be calculated with DTC and BC. Our results suggest that the reproducibility of the H/M and WR between institutions was improved by performing optimization of the ROI setting and unification of the mathematical method.

Usefulness of cardiac iodine-123 meta-iodobenzylguanidine imaging to improve prognostic power of Seattle heart failure model in patients with chronic heart failure

The Seattle Heart Failure Model (SHFM) is a validated prediction model that estimates the mortality in patients with chronic heart failure (CHF) using commonly obtained information, including clinical data, laboratory test results, medication use, and device implantation. In addition, cardiac iodine-123 meta-iodobenzylguanidine (MIBG) imaging provides prognostic information for patients with CHF. However, the long-term predictive value of combining the SHFM and cardiac MIBG imaging in patients with CHF has not been elucidated. To prospectively investigate whether cardiac iodine-123 MIBG imaging provides additional prognostic value to the SHFM in patients with CHF, we studied 106 outpatients with CHF who had radionuclide left ventricular ejection fraction < 40% (30 ± 8%). The SHFM score was obtained at enrollment, and the cardiac MIBG washout rate (WR) was calculated from anterior chest images obtained at 20 and 200 minutes after isotope injection. During a mean follow-up of 6.8 ± 3.5 years (range 0 to 13), 32 of 106 patients died from cardiac causes. A multivariate Cox analysis revealed that the WR (p = 0.0002) and SHFM score (p = 0.0091) were independent predictors of cardiac death. Kaplan-Meier analysis showed that patients with an abnormal WR (> 27%) had a significantly greater risk of cardiac death than did those with a normal WR for both those with a SHFM score of ≥ 1 (relative risk 3.3, 95% confidence interval 1.2 to 9.7, p = 0.01) and a SHFM score of ≤ 0 (relative risk 3.4, 95% confidence interval 1.2 to 9.6, p = 0.004). In conclusion, the cardiac MIBG WR provided additional prognostic information to the SHFM score for patients with CHF.

Norepinephrine spillover during exercise as a novel parameter to evaluate the severity of heart failure

BACKGROUND

The washout rate (WR) of (123)I-metaiodobenzylguanidine (MIBG) is now widely used for assessing the severity of heart failure. Although the WR of MIBG is usually measured at rest, the assessment of WR of MIBG during exercise might have a different clinical relevance. In this study, we measured the WR rate of MIBG during low-grade exercise and studied the clinical importance of this novel index.

METHODS

Twenty-four patients with dilated cardiomyopathy (DCM) were enrolled in this study. Planar images were obtained 20 minutes after MIBG injection (first image) and after 270 minutes (second image); the third image was obtained after 15 minutes of low-grade (10 W) bicycle ergometer exercise (300 minutes after MIBG injection). The decay of the specific counts was calculated from the first two images. The estimated third counts were calculated from the resting decay and were compared with the actual third counts.

RESULTS

In the receiver operating characteristic (ROC) curve analysis, we set a 10% decrease from the estimated counts as a cut-off value for severe heart failure (New York Heart Association [NYHA] Class IIm or worse). In 15 patients, the actual third count value was within 10% of the estimated count (N-group). In nine patients, the WR during exercise was high, and the actual third count values showed more than a 10% decrease from the estimated count value (H-group). In the H-group, 78% of the patients were in NYHA class IIm or III. In contrast, in the N-group, no patient had NYHA class III, and only 20% of the patients were in class IIm. The brain natriuretic peptide (BNP) level was significantly higher in the H-group than in the N-group (525 ± 263 pg/mL vs 176 ± 144 pg/mL; P < .01). No significant differences were observed in heart/mediastinal (H/M) activity ratio, the regular WR, and left ventricular ejection fraction values between the two groups.

CONCLUSIONS

The WR of MIBG during exercise may be an independent prediction variable, with a clinical relevance different from that of the WR at rest. This measurement could be used as a new index for assessing the severity of heart failure.

Iodine-123 metaiodobenzylguanidine imaging and carbon-11 hydroxyephedrine positron emission tomography compared in patients with left ventricular dysfunction

BACKGROUND

Although both (123)I-metaiodobenzylguanidine ((123)I-MIBG) imaging and (11)C-hydroxyephedrine ((11)C-HED) positron emission tomography (PET) are used for assessing cardiac sympathetic innervation, their relationship remains unknown. The aims were to determine whether (123)I-MIBG parameters such as heart-to-mediastinum ratio (H/M) are associated with quantitative measures by (11)C-HED PET and to compare image quality, defect size, and location between (123)I-MIBG single-photon emission computed tomography (SPECT) and (11)C-HED PET.

METHODS AND RESULTS

Twenty-one patients (mean left ventricular ejection fraction, 39 ± 15%) underwent (123)I-MIBG imaging and (11)C-HED PET. Early (15-minute), late (3-hour) H/M, and washout rate (WR) were calculated for (123)I-MIBG. Myocardial retention and WR was calculated for (11)C-HED. Using a polar map approach, defect was defined as the area with relative activity <60% of the maximum. Both the early (r=0.76) and late (r=0.84) (123)I-MIBG H/M were correlated with (11)C-HED retention. (123)I-MIBG WR was correlated with (11)C-HED WR (r=0.57). Defect size could not be measured in 3 patients because of poor quality (123)I-MIBG SPECT, whereas (11)C-HED defect was measurable in all patients. Although defect size measured by early or late (123)I-MIBG SPECT was closely correlated with that by (11)C-HED PET (early: r=0.94; late: r=0.88), the late (123)I-MIBG overestimated defect size particularly in the inferior and septal regions.

CONCLUSIONS

(123)I-MIBG H/M gives a reliable estimate of cardiac sympathetic innervation as measured by (11)C-HED PET. Furthermore, despite the close correlation in defect size, (11)C-HED PET appears to be more suitable for assessing regional abnormalities than does (123)I-MIBG SPECT.

Cardiac sympathetic activity is associated with inflammation and neurohumoral activation in patients with idiopathic dilated cardiomyopathy

BACKGROUND

Idiopathic dilated cardiomyopathy (IDC) is characterized by sympathetic nervous overactivity, inflammation and neurohumoral activation; however, their interrelationships are poorly understood.

METHODS AND RESULTS

We studied 99 patients with IDC (age 54 +/- 1 years, left ventricular ejection fraction (EF) 40 +/- 1%, maximum oxygen uptake (VO(2)max) 20 +/- 1 ml kg(-1) min(-2), mean +/- SEM) by using (123)I-metaiodobenzylguanidine (MIBG) imaging. MIBG washout and MIBG heart/mediastinum (H/M)-ratio at 4 h postinjection were calculated. In addition, the plasma levels of interleukin (IL)-6 and N-terminal B-type natriuretic peptide (NT-proBNP) were measured. MIBG washout and MIBG H/M ratio had a significant correlation with IL-6 (r = 0.42, P<0.001 and r = -0.31, P<0.01) and NT-proBNP (r = 0.48, P<0.001 and r = -0.40, P<0.001). During a median follow-up of 4.1 years, 20 patients (20%) had an adverse cardiac event (death, heart transplantation or application of biventricular pacemaker or implantable cardioverter-defibrillator). In these patients, MIBG washout was higher (53 +/- 4 versus 40 +/- 2%, P = 0.01) and H/M ratio lower (1.38 +/- 0.04 versus 1.51 +/- 0.02, P = 0.01) than in patients without an event.

CONCLUSIONS

In dilated cardiomyopathy, myocardial sympathetic innervation and activity are related to inflammation and neurohumoral activation. These relationships are at least partly independent of left ventricular function and exercise capacity.

Impact of mediastinal, liver and lung (123)I-metaiodobenzylguanidine ( (123)I-MIBG) washout on calculated (123)I-MIBG myocardial washout

PURPOSE

In planar (123)I-metaiodobenzylguanidine ((123)I-MIBG) myocardial imaging mediastinum (M) activity is often used as a background correction in calculating "washout" (WO). However, the most likely sources for counts that might produce errors in estimating myocardial (Myo) activity are lung (Lu) and liver (Li), which typically have higher counts/pixel (cpp) than M. The present study investigated the relationship between changes in Lu, Li and Myo activity between early and late planar (123)I-MIBG images, with comparison to M as the best estimator of non-specific background activity.

METHODS

Studies on 98 subjects with both early (e) and late (l) planar (123)I-MIBG images were analysed. There were 68 subjects with chronic heart failure (CHF), 14 with hypertension (HTN) but no known heart disease and 16 controls (C). For each image, regions of interest (ROIs) were drawn: an irregular whole Myo, Lu, upper M and Li. For each ROI, WO was calculated as [(cpp(e)-cpp(l:decay corrected))/cpp(e)]x100%.

RESULTS

Multivariable forward stepwise regression analysis showed that overall a significant proportion of the variation in Myo WO could be explained by a model containing M WO and Lu WO (37%, p < 0.001). Only in controls was M WO the sole variable explaining a significant proportion of the variation in Myo WO (27%, p = 0.023).

CONCLUSION

Although increased Myo WO in CHF subjects reflects disease severity, part of the count differences measured on planar (123)I-MIBG myocardial images likely reflects changes in the adjacent and surrounding Lu tissue. The results for the controls suggest that this is the only group where a mediastinum correction alone may be appropriate for cardiac WO calculations.

Cardiac iodine-123 metaiodobenzylguanidine imaging predicts sudden cardiac death independently of left ventricular ejection fraction in patients with chronic heart failure and left ventricular systolic dysfunction: results from a comparative study with signal-averaged electrocardiogram, heart rate variability, and QT dispersion

OBJECTIVES

We prospectively compared the predictive value of cardiac iodine-123 metaiodobenzylguanidine (MIBG) imaging for sudden cardiac death (SCD) with that of the signal-averaged electrocardiogram (SAECG), heart rate variability (HRV), and QT dispersion in patients with chronic heart failure (CHF).

BACKGROUND

Cardiac MIBG imaging predicts prognosis of CHF patients. However, the long-term predictive value of MIBG imaging for SCD in this population remains to be elucidated.

METHODS

At entry, cardiac MIBG imaging, SAECG, 24-h Holter monitoring, and standard 12-lead electrocardiography (ECG) were performed in 106 consecutive stable CHF outpatients with a radionuclide left ventricular ejection fraction (LVEF) <40%. The cardiac MIBG washout rate (WR) was obtained from MIBG imaging. Furthermore, the time and frequency domain HRV parameters were calculated from 24-h Holter recordings, and QT dispersion was measured from the 12-lead ECG.

RESULTS

During a follow-up period of 65 +/- 31 months, 18 of 106 patients died suddenly. A multivariate Cox analysis revealed that WR and LVEF were significantly and independently associated with SCD, whereas the SAECG, HRV parameters, or QT dispersion were not. Patients with an abnormal WR (>27%) had a significantly higher risk of SCD (adjusted hazard ratio: 4.79, 95% confidence interval: 1.55 to 14.76). Even when confined to the patients with LVEF >35%, SCD was significantly more frequently observed in the patients with than without an abnormal WR (p = 0.02).

CONCLUSIONS

Cardiac MIBG WR, but not SAECG, HRV, or QT dispersion, is a powerful predictor of SCD in patients with mild-to-moderate CHF, independently of LVEF.

Effectiveness of nocturnal home oxygen therapy to improve exercise capacity, cardiac function and cardiac sympathetic nerve activity in patients with chronic heart failure and central sleep apnea

BACKGROUND

Central sleep apnea, often found in patients with chronic heart failure (CHF), has a high risk of poor prognosis.

METHODS AND RESULTS

This study involved 20 patients with CHF (left ventricular ejection fraction (LVEF) <45%, M/F =19/1, age 65+/-10 years) and an apnea-hypopnea index (AHI) >5 times/h who were divided into 2 groups: 10 patients treated with nocturnal home oxygen therapy (HOT) and 10 patients without HOT (non-HOT). All patients had dilated cardiomyopathy and underwent overnight polysomnography, cardiopulmonary exercise testing, and nuclear cardiac examinations to evaluate AHI, exercise capacity according to the specific activity scale and oxygen uptake at anaerobic threshold and peak exercise (peak VO(2)). Cardiac function according to (99m)Tc-MIBI QGS, and the total defect score (TDS), H/M ratio and the washout rate (WR) on (123)I-metaiodobenzylguanidine (MIBG) imaging were calculated for all patients. As compared with the non-HOT group, the HOT group demonstrated a greater reduction in AHI (26.1+/-9.1 to 5.1+/-3.4), (123)I-MIBG TDS (31+/-8 to 25+/-9), and (123)I-MIBG WR (48+/-8% to 41+/-5%) and a greater increase in the specific activity scale (4.0+/-0.9 to 5.8+/-1.2 Mets), peak VO(2) (16.0+/-3.8 to 18.3+/-4.7 ml . min(-1) . kg(-1)), and LVEF (27+/-9% to 37+/-10%).

CONCLUSIONS

HOT improves exercise capacity, cardiac function, and cardiac sympathetic nerve activity in patients with CHF and central sleep apnea.

Beneficial effect of perindopril on cardiac sympathetic nerve activity and brain natriuretic peptide in patients with chronic heart failure: comparison with enalapril

BACKGROUND

In patients with chronic heart failure (CHF), it remains unclear whether perindopril is more cardioprotective than enalapril.

METHODS AND RESULTS

Forty-five stable CHF outpatients undergoing conventional therapy including enalapril therapy were randomized to 2 groups [group I (n=24): continuous enalapril treatment; group II (n=21): enalapril was changed to perindopril]. Cardiac sympathetic nerve activity was evaluated using cardiac 123I-metaiodobenzylguanidine (MIBG) scintigraphy, hemodynamic parameters and neurohumoral factors before and 6 months after treatment. There was no difference in baseline characteristics between the 2 groups. In group I, there were no changes in MIBG parameters, left ventricular ejection fraction (LVEF) or plasma level of brain natriuretic peptide (BNP). In contrast, in group II the delayed heart/mediastinum count ratio was significantly increased (2.0+/-0.07 vs 2.15+/-0.07, p=0.013) and the washout rate was significantly decreased (33.0+/-1.4 vs 30.5+/-1.2, p=0.030) after 6 months compared with the baseline value. In addition, LVEF was significantly increased and the plasma BNP level was significantly decreased.

CONCLUSION

These findings suggest that for the treatment of CHF, perindopril is superior to enalapril with respect of cardiac sympathetic nerve activity and BNP.

Neuronal imaging using SPECT

(123)I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy is one of only a few methods available for objective evaluation of cardiac sympathetic function at the clinical level. Disorders of cardiac sympathetic function play an important role in various heart diseases, and MIBG provides an abundance of useful information for the evaluation of severity, prognosis and therapeutic effects; this is particularly useful in cases of heart failure, ischaemic heart disease and arrhythmic disease. On the other hand, the quantitative indices for MIBG differ between institutions, and evidence has not been sufficiently well established for MIBG scintigraphy when compared with myocardial perfusion imaging in ischaemic heart diseases. In consideration of these difficulties, this review provides fundamental information regarding MIBG, its usefulness for various diseases and future difficulties.

Neuronal imaging using SPECT

BACKGROUND

123I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy is one of only a few methods available for objective evaluation of cardiac sympathetic function at a clinical level. Disorders in cardiac sympathetic function play an important role in various heart diseases, and MIBG provides an abundance of useful information for evaluation of disease severity, prognosis, and therapeutic effects; this information is of particular value in patients with heart failure, ischemic heart diseases, or arrhythmic disorders. On the other hand, the quantitative indices for MIBG differ between institutions, and evidence has not been sufficiently well established for MIBG, compared with myocardial perfusion imaging, in ischemic heart diseases.

REVIEW

In view of these difficulties, this review provides fundamental information regarding MIBG, its usefulness for various diseases and future difficulties.

Assessment of central chemosensitivity and cardiac sympathetic nerve activity using I-123 MIBG imaging in central sleep apnea syndrome in patients with dilated cardiomyopathy

OBJECTIVE

Iodine-123 MIBG imaging has been used to study cardiac sympathetic function in various cardiac diseases. Central sleep apnea syndrome (CSAS) occurs frequently in patients with chronic heart failure (CHF) and is reported to be associated with a poor prognosis. One of the mechanisms of its poor prognosis may be related to impaired cardiac sympathetic activity. However, the relationship between chemosensitivity to carbon dioxide, which is reported to correlate with the severity of CSAS, and cardiac sympathetic activity has not been investigated. Therefore, this study was undertaken to assess cardiac sympathetic function and chemosensitivity to carbon dioxide in CHF patients.

METHODS

The oxygen desaturation index (ODI) was evaluated in 21 patients with dilated cardiomyopathy (male/female: 19/2, LVEF < 45%, 65 +/- 12 yr). Patients with an ODI > 5 times/h underwent polysomnography. Patients with an apnea hypopnea index > 15/h but without evidence of obstructive apnea were defined as having CSAS. Early (15 min) and delayed (4 hr) planar MIBG images were obtained from these patients. The mean counts in the whole heart and the mediastinum were obtained. The heart-to-mediastinum count ratio of the delayed image (H/M) and the corrected myocardial washout rate (WR) were also calculated. The central chemoreflex was assessed with the rebreathing method using a hypercapnic gas mixture (7% CO2 and 93% O2).

RESULTS

Ten of the 21 patients had CSAS. The H/M ratio was similar in patients both with and without CSAS (1.57 +/- 0.18 vs. 1.59 +/- 0.14, p = 0.82). However, the WR was higher in patients with CSAS than in patients without CSAS (40 +/- 8% vs. 30 +/- 12%, p < 0.05). ODI significantly correlated with central chemosensitivity to carbon dioxide. Moreover, there was a highly significant correlation between WR and central chemosensitivity (r = 0.65, p < 0.05). However, there was no correlation between ODI and the WR (r = 0.36, p = 0.11).

CONCLUSIONS

Cardiac sympathetic nerve activity in patients with CHF and CSAS is impaired. However, central sleep apnea might not directly increase cardiac sympathetic nerve activity. We suggest that central chemosensitivity, which is considered to be one of the mechanisms of CSAS, is correlated with cardiac sympathetic nerve activity.

Importance of renal function on prognostic value of cardiac iodine-123 metaiodobenzylguanidine scintigraphy

OBJECTIVE

Cardiac iodine-123 metaiodobenzylguanidine (MIBG) can be used to evaluate cardiac sympathetic nerve function and is useful for assessing the prognosis of patients with heart disease. Renal impairment in heart failure patients has been recognized as an independent risk factor for morbidity and mortality, and has been observed as abnormal uptake and washout of cardiac MIBG imaging. The purpose of this study was to evaluate the prognostic value of cardiac MIBG imaging in heart disease patients with a glomerular filtration rate (GFR) either > or = 60 ml/min/1.73 m2 or < 60 ml/min/1.73 m2.

METHODS

Heart disease patients (n: 135, male/female: 87/48, mean age: 63 years, coronary artery disease/dilated cardiomyopathy/myocarditis: 41/62/32, mean left ventricular ejection fraction: 51%, GFR > or = 60 ml/min/1.73 m2/ GFR < 60 ml/min/1.73 m2: 103/32) underwent cardiac MIBG imaging and were followed-up for 2.7 years. GFR was calculated by the Modification of Diet in Renal Disease (MDRD) equation. Cardiac MIBG imaging was obtained 15 min and 4 h after isotope injection. The parameters analyzed for cardiac MIBG imaging were the heart-to-mediastinum ratio (H/M) on the delayed planar image and the cardiac washout rate.

RESULTS

Cardiac death was observed in 9 of 103 patients (9%) with a GFR > or = 60 ml/min/1.73 m2 and in 6 of 32 patients (19%) with a GFR < 60 ml/min/1.73 m2. The mortality ratio tended to be higher in patients with a GFR < 60 ml/min/1.73 m2 than in patients with a GFR > or = 60 ml/min/1.73 m2 (p = 0.10 with Kaplan-Meier survival curves). In patients with a GFR > or = 60 ml/min/1.73 m2, Cox regression analysis showed that a delayed H/M < 146% was the most powerful predictor for cardiac death (Hazard ratio: 6.9, p = 0.014). However, in patients with a GFR < 60 ml/min/1.73 m2, the utility of cardiac MIBG imaging could not be proved.

CONCLUSIONS

A delayed H/M is a powerful predictor of cardiac death if the GFR is 60 ml/min/1.73 m2 or more.

Usefulness of123I-metaiodobenzylguanidine myocardial scintigraphy in the prediction of cardiac events in patients with cardiomyopathy showing stabilization of symptoms or preserved cardiac function

OBJECTIVE

It is not rare for patients with cardiomyopathy to be asymptomatic for long periods or to show improved cardiac function following various medical interventions. Conversely, cardiac events sometimes occur in those patients, requiring close observation. We assessed the usefulness of 123I-metaiodobenzylguanidine myocardial scintigraphy (MIBG) to predict the occurrence of cardiac events in patients with stable cardiomyopathy.

METHODS

The subjects comprised 74 outpatients with stable cardiomyopathy. MIBG was performed calculate the extent score, severity score, washout rate (WR), and heart-to-mediastinum ratio. At about the same time, the left ventricular ejection fraction (LVEF) by echocardiography and the plasma brain natriuretic peptide were measured. The mean observation period extended for 741+/-437 days with an end point of cardiac events (cardiac death, heart failure requiring hospitalization, and arrhythmias requiring hospitalization).

RESULTS

During the mean follow-up period, 15 cardiac events occurred. Results of multivariate analysis revealed that LVEF was the most powerful predictor of cardiac events (0.006, p < 0.01). However, WR was the only significant predictor of hard events such as cardiac death (1.171, p < 0.001) and cardiac events in the group of patients who preserved cardiac function with LVEF 0.4 or higher (1.079, p < 0.05).

CONCLUSION

Combined use of LVEF and WR is useful to predict the occurrence of cardiac events in patients with stable cardiomyopathy.