Washout Rate Of MIBG Research Articles

MYOCARDIAL PERFUSION AND NEUROTROPIC SINGLE-PHOTON EMISSION COMPUTED TOMOGRAPHY FEATURES IN PATIENTS WITH PRIMARY PULMONARY HYPERTENSION

Objective.To compare cardiac123I-MIBG and99m Tc-MIBI single-photon emission computed tomography (SPECT) data in patients with primary pulmonary hypertension (PPH).Material and methods.The study included 22 patients with confirmed diagnosis of PPH, with clinical status assessment, Holter ECG monitoring and rest cardiac ultrasound (US) data. All patients, as well as a group of healthy volunteers (n=20) underwent myocardial perfusion SPECT with99mTc-MIBI at rest and after treadmill exercise test, and myocardial neurotropic SPECT with123I-MIBG, performed in 15 min (early phase) and 4 hours (delayed phase) after MIBG administration. LV perfusion abnormalities were evaluated using standard SSS and SDS parameters, RV was assessed visually, RV/LV and IVS/LW uptake ratios were calculated. Global sympathetic activity (SA) was assessed with delayed heart/mediastinum ratio (H/Md) and MIBG Washout Rate in 4 hours (WR). Regional SA abnormalities were assessed using early Summed MIBG Score (SMSe). MIBG RV/LV and LV IVS/LW uptake ratios were calculated. All parameters were compared with normal database (n=20).Results.The values of a number of myocardial SPECT parameters, both perfusion (SSS, RV/LVMIBI, IVS/LWMIBI) and neurotropic (H/Md, WR, SMSe, IVS/LWMIBG), were significantly worse in PPH patients compared to the control group (all p<0.05). Perfusion SPECT showed no significant (SDS>4) transient LV ischemia in all patients, but in 77% of cases IVS perfusion was stably impaired, causing overall SSS=7 (6–10), presumably due to IVS compression by dilated RV. MIBI RV/LV ratio was 0.61±0.02, indicating that RV was clearly visible, with inhomogeneous MIBI uptake in all cases, but without reliable perfusion defects. Values of H/Mdwere 1.84±0.18, WR: 27±8%, with no reliable correlations with perfusion parameters. Regional SA defects also were located in IVS predominately, causing SMSemean value of 8 (6–10) and IVS/LW of 0.69±0.09, both parameters correlated with SSS (r=0.44, p=0.04 and r=-0.48, p=0.02, respectively). All parameters, except RV/LVMIBG, had reliable correlations with systolic pulmonary artery pressure assessed by cardiac US, especially RV/LVMIBI(r=0.64, p<0.01), WR (r=0.55, p=0.01) and IVS/LWMIBG(r=-0.49, p=0.02).Conclusion.Combination of myocardial neurotropic and perfusion SPECT has a certain diagnostic value in patients with PPH, since MIBG SPECT reflects SA downregulating, and MIBI SPECT reveals specific microcirculatory abnormalities in these patients, both possibly caused by myocardial pressure overload and responsible for angina-like symptoms.

Transcatheter Aortic Valve Implantation Improves Cardiac Sympathetic Nerve Activity on 123I-Metaiodobenzylguanidine Myocardial Scintigraphy in Severe Aortic Valve Stenosis.

There is a consensus that overactivation of the cardiac sympathetic nervous system (CSN) proportionately increases the severity of heart failure and is accompanied by worse prognosis. Because it is unknown whether patients with aortic valve stenosis (AS) have similar CSN activation, we investigated the effect of transcatheter aortic valve implantation (TAVI).Methods and Results:We enrolled 31 consecutive patients with AS treated by TAVI. 123I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy was performed at baseline and at 2 weeks after TAVI. At baseline, the early heart-mediastinum ratio (H/M) was within normal limits (3.0±0.5), but the delayed H/M was low (2.6±0.6) and the washout rate (WR) was high (34±13%). WR negatively correlated with aortic valve area (r=-0.389, P<0.01) and cardiac output (r=-0.595, P<0.01) and positively correlated with norepinephrine (r=0.519, P<0.01) and log NT-proBNP level (r=0.613, P<0.01). After TAVI, there were significant decreases in the norepinephrine level (366±179 ng/mL vs. 276±125 ng/mL, P<0.01) and WR (34±13 vs. 26±11%, P<0.01). The WR of MIBG was a useful marker of CSN activity and severity of AS. Immediate improvement of CSN activity after TAVI implied that AS hemodynamics per se enhanced CSN.

Prediction of sudden cardiac death in patients with chronic heart failure by regional washout rate in cardiac MIBG SPECT imaging

BackgroundThe sympathetic nervous system provides an important trigger for major arrhythmic events through regional heterogeneity of sympathetic activity, which could be evaluated by SPECT imaging as the regional MIBG washout rate (WR). There is little information available on the prognostic value of regional WR in SPECT imaging for the prediction of sudden cardiac death (SCD) in patients with chronic heart failure (CHF). MethodsWe studied 73 CHF outpatients with LVEF < 40%. At study entry, the regional WR was measured in 17 segments on the polar map. We defined abnormal regional WR as both the regional WR range (maximum − minimum regional WR) and maximum regional WR > mean value + 2SD obtained in 15 normal controls. ResultsDuring a mean follow-up of 7.5 ± 4.1 years, 15 of 73 patients had SCD. The abnormal regional WR and abnormal global WR on planar images were significantly and independently associated with SCD. Patients with both the abnormal regional WR and global WR had a significantly higher risk of SCD than those with none of these criteria. ConclusionsThe analysis of regional MIBG WR on SPECT imaging provides additional prognostic value to global WR on planar images for SCD prediction in CHF patients.

Myocardial (123)I-MIBG Uptake and Cardiovascular Autonomic Function in Parkinson's Disease.

Introduction. Patients with Parkinson's disease (PD) showed reduced myocardial 123I-MIBG uptake, which may affect autonomic regulation. We investigated correlation between MIBC accumulation and cardiovascular autonomic function in PD. Methods. We performed myocardial MIBG scintigraphy, heart rate variability (HRV) analysis, and the head-up tilt test (HUT) in 50 PD patients (66.4 ± 7.8 years; duration 5.5 ± 5.9 years). Autonomic function tests were also performed in 50 healthy controls (66.5 ± 8.9 years). As HRV parameters, a high-frequency power (HF, 0.15–0.4 Hz), a low-frequency power (LF, 0.04–0.15 Hz), and LF/HF ratio were used. Results. Our PD patients had a significant reduction in LF and HF compared with the controls (P = 0.005 and P = 0.01). In HUT, systolic and diastolic blood pressure falls in the PD group were significantly greater than those in the controls (P = 0.02 and P = 0.02). The washout rate of MIBG was negatively correlated with blood pressure changes during HUT. Conclusion. Our PD patients showed reduced HRV, blood pressure dysregulation, and reduced MIBG accumulation, which was correlated with blood pressure dysregulation. Orthostatic hypotension in PD may be mainly caused by sympathetic postganglionic degeneration.

Cardiac sympathetic imaging withmIBG in cirrhosis and portal hypertension: relation to autonomic and cardiac function

Autonomic and cardiac dysfunction is frequent in cirrhosis and includes increased sympathetic nervous activity, impaired heart rate variability (HRV), and baroreflex sensitivity (BRS). Quantified (123)I-metaiodobenzylguanidine (mIBG) scintigraphy reflects cardiac noradrenaline uptake, and in patients with cardiac failure it predicts outcome. In this study, we aimed to investigate cardiac sympathetic neuronal function in cirrhosis by mIBG scintigraphy in relation to cardiovascular function. Ten patients with alcoholic cirrhosis and 10 age- and sex-matched healthy controls participated in the study. Heart/mediastinum (H/M) ratios of mIBG uptake were calculated 15 and 230 min after intravenous injection of mIBG. Furthermore, washout rate (WOR) of mIBG was calculated. The patients underwent a liver vein catheterization with determination of splanchnic and systemic hemodynamics and measurement of HRV and BRS. mIBG-scintigraphy revealed significantly increased WOR in patients with cirrhosis compared with controls (P < 0.005), whereas H/M uptakes were equal in the groups. Forty percent of the patients had reduced uptake of mIBG in the infero-lateral segment of the left ventricle. WOR correlated significantly with central circulation time, an estimate of central hypovolemia (r = -0.64, P < 0.05) and frequency-corrected QT(F) interval (r = 0.71, P = 0.01). Patients with cirrhosis had significantly decreased HRV and BRS correlating with indicators of abnormal cathecholamine uptake by mIBG although the catecholamine level was normal in the patients. In conclusion, in alcoholic cirrhosis, mIBG scintigraphy reveals autonomic dysfunction and impaired myocardial distribution of sympathetic nervous activity. It is associated to indicators of central hypovolemia, QT interval, and decreased HRV and BRS. Measurement of myocardial catecholamine uptake by mIBG may add important information on autonomic and cardiac dysfunction in cirrhosis.

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

BackgroundThe washout rate (WR) of 123I-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. MethodsTwenty-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. ResultsIn 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. ConclusionsThe 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.

Scintigraphic studies on the etiology of Ampulla Cardiomyopathy

Although there are many reports on Ampulla Cardiomyopathy, its etiologic mechanisms are not well known. Etiology of Ampulla Cardiomyopathy was investigated by myocardial scintigraphy with various nuclear tracers. In nine patients with Ampulla Cardiomyopathy, myocardial scintigraphy was performed at acute, subacute and chronic phases. Total defect score (TDS) of tallium-201 (Tl) or technetrium-99m sestamibi (MIBI) myocardial perfusion and iodine-123-beta-methyl-p-iodophenyl penta-decanoic acid (BMIPP) scintigraphies was calculated. Cardio-mediastinal ratio (H/M) and washout rate (WR) of early and delayed images of iodine-123-meta-iodobenzylguanidine (MIBG) scintigraphy were also calculated. The patients in whom TDS of myocardial perfusion scintigraphy at acute phase was 0, were classified into group N (n = 5) and those with TDS > or = 1 into group D (n = 4). TDS of BMIPP at acute, subacute and chronic phases was higher in D than in N; 28.8 +/- 10.3 vs. 7.2 4.7 (p = 0.0039), 15.5 +/- 2.1 vs. 1.0 +/- 0.8 (p < 0.0001) and 2.7 +/- 1.2 vs. 0 (p = 0.05), respectively. WR of MIBG at acute phase was also higher in D (50.3 +/- 5.7% vs. 36.6 +/- 10.5%, p = 0.05). H/M (dH/M) on the delayed images and WR at chronic phase were not different between the two groups. H/M (eH/M) on the early images was lower in D. Blood noradrenaLine (ng/ml) at acute phase was higher in D than in N (1.21 +/- 0.55 vs. 0.45 +/- 0.33, p < 0.05). Left ventricular ejection fraction (LVEF) was decreased in both at acute phase but it was lower in D than in N (48.1 +/- 3.7% vs. 69.9 +/- 9.7%, p < 0.05) at subacute phase. These findings suggest that the etiology of Ampulla Cardiomyopathy is neurologically stunned myocardium induced by coronary microcirculatory disorder. Due to the significant amount of time that was necessary for normalization of wall motion in the D group, myocardial scintigraphy is believed to be also useful in assessment of severity.

Prognostic value of 123I-metaiodobenzylguanidine in patients with various heart diseases

It has been reported that (123)I-metaiodobenzylguanidine (MIBG) scintigraphy can predict the poor prognosis in patients with dilated cardiomyopathy (DCM). However, the prognostic significance of MIBG is still unknown in patients with other heart diseases. In this study, we compared the prognosis and MIBG findings in various heart diseases. Consecutive 565 patients undergoing MIBG scintigraphy were enrolled (392 men, 52 +/- 16 years). Indications were that 127 had ischemic heart disease (IHD), 120 DCM, 101 hypertrophic cardiomyopathy (HCM), 21 hypertensive heart disease (HHD), 58 volume-load valvular disease (VVD), 38 pressure-load valvular disease (PVD), and 101 ventricular tachycardia or fibrillation (VTF). Heart-to-mediastinum ratio (H/M) and washout rate (WR) of MIBG were evaluated. Cardiac events were defined as sudden cardiac death, heart failure, and acute ischemic event (follow-up, 22.7 +/- 17.0 months). A total of 106 cardiac events including 40 cardiac deaths occurred. Cox hazard model analysis showed that in the IHD, HCM, and DCM groups, H/M and WR were associated with cardiac death, but not in the HHD, PVD, VVD, or VTF groups. Only death and congestive heart failure (CHF) episodes were related to H/M and WR. On the other hand, fatal arrhythmia, myocardial infarction, or angina pectoris were not related to H/M and WR. The data indicated that WR or H/M may predict death and CHF but does not predict fatal arrhythmia or acute ischemic event. MIBG WR and H/M were associated with heart failure, sudden death, and cardiac death events, and were useful to predict the prognosis in DCM, HCM, and IHD. In contrast, fatal arrhythmia events were not associated with MIBG indices, and thus it does not appear to be useful in predicting cardiac events in patients with VTF.

Dilated cardiomyopathy relieved as a result of β-blocker therapy: A case report—key points in assessment of prognosis based on MIBG myocardial scintigraphy and BNP levels

A 48-year-old male patient was admitted to our hospital with dyspnea accompanied by orthopnea. Chest x-rays showed a cardiothoracic ratio of 68% and pulmonary congestion. He was diagnosed with dilated cardiomyopathy. Beta-Blocker (carvedilol) therapy was initiated on Day 22 of the disease using a small initial dose. He was followed up based on BNP levels and MIBG scintigraphy. The H/M ratio and MIBG washout rate were 1.98 and 33.4%, respectively, on Day 20 and 2.15 and 28.1%, respectively, on Day 72. The patient was discharged on Day 72 when congestive heart failure improved. Relatively high BNP levels were observed for 1 month after starting treatment with a beta-blocker. Plasma BNP levels were still as high when his heart failure was improved. BNP is useful as a convenient indicator for the severity of cardiac diseases. MIBG scintigraphy may be used thereafter to evaluate the severity in greater detail and more precisely determine the prognosis.

Iodine 123‐metaiodobenzylguanidine imaging reflect generalized sympathetic activation in patients with left ventricular dysfunction

Iodine 123-metaiodobenzylguanidine (MIBG) imaging has been used to assess cardiac sympathetic nerve abnormalities. To determine the role of MIBG imaging as a measure of generalized sympathetic nerve activity, MIBG imaging was evaluated with muscle sympathetic nerve activity (MSNA) and plasma norepinephrine (noradrenaline) level in patients with old myocardial infarction. Myocardial MIBG scintigraphy, MSNA and plasma norepinephrine measurement were performed within 3 days in 35 patients with old myocardial infarction. Patients were divided into three groups according to their ejection fraction (EF); preserved (EF > or = 50%, 12 patients), intermediate (35% < EF < 50%, 13 patients), or depressed (EF < or = 35%, 10 patients). The heart to mediastinum (H/M) ratio was obtained 4 h after tracer injection from the chest anterior view image. MIBG washout rate was calculated from the early and delayed images. MSNA was recorded by microneurography. Plasma norepinephrine level had weak negative correlations with early H/M ratio (r = 0.37, P<0.05) and delayed H/M ratio (r = 0.33, P<0.05), and a positive correlation with MIBG washout rate (r = 0.54, P<0.01). MSNA had weak negative correlations with early H/M ratio (r = 0.51, P<0.05) and delayed H/M ratio (r = 0.52, P<0.05). However, a strong correlation was found between MSNA and MIBG washout rate (r = 0.88, P<0.001). Despite no significant differences in plasma norepinephrine level and H/M ratio, patients with intermediate and depressed EF had higher MIBG washout rate and MSNA compared with those with preserved EF. Increased in cardiac sympathetic nerve activity was associated with augmented sympathetic outflow of the skeletal muscle and hence, MIBG washout rate allow the assessment of general sympathetic nerve activity.

Prognostic Value of I-123 Metaiodobenzylguanidine Imaging in Vasospastic Angina Without Significant Coronary Stenosis

Myocardial imaging is widely used to detect coronary artery disease and to assess its prognosis. In vasospastic angina (VA), cardiac imaging can provide information on disease activity, which is related to cardiac events. The aim of this study was to clarify whether exercise thallium-201 imaging (Tl-SPECT) and 123I-metaiodobenzylguanidine imaging (MIBG) have prognostic value for patients with VA, but without significant coronary artery stenosis. One hundred and 5 patients who showed acetylcholine-induced coronary spasm, normal left ventricular function and no significant stenosis (<50%) underwent both symptom-limited Tl-SPECT and MIBG within 1 month. All patients were prescribed calcium antagonist during the follow-up period (mean 4.7 years). Exercise-induced ischemia was detected by Tl-SPECT in 53 patients and multivessel coronary spasm by coronary angiography in 33 patients. During the follow-up period, 1 patient died suddenly and another died of acute myocardial infarction (MI). Two patients developed nonfatal acute MI and 7 patients underwent emergency coronary angiography because of unstable angina. According to the baseline characteristics, VA with cardiac events showed a significantly higher heart-to-mediastinum ratio (H/M ratio) and a significantly lower MIBG washout rate than those without cardiac events (p<0.03 and p<0.02, respectively). Among 8 clinical variables, including coronary risk factors, exercise parameters and exercise-induced ischemia on Tl-SPECT and the MIBG delayed H/M ratio and washout rate, univariate Cox proportional hazard regression analysis showed that the high H/M ratio and reduced washout rate of MIBG were significant predictors of future cardiac events (relative risk (RR) =4, confidence interval (CI) =1.21-13.29, p<0.02 for H/M ratio and RR 0.92, CI 0.85-0.99, p<0.02 for washout rate). However, exercise-induced ischemia did not show any statistical significance. By multivariate Cox proportional hazard regression analysis, a reduced MIBG washout rate was the only significant predictor of future cardiac events (odds ratio =0.90, CI =0.82-1.00, p<0.04). MIBG imaging can identify high-risk patients, even among those with VA who were previously regarded as low risk. This result strongly supports the idea that cardiac sympathetic dysfunction contributes to coronary artery spasm leading to cardiac events.

Corrected QT Dispersion and Cardiac Sympathetic Function in Patients With Obstructive Sleep Apnea-Hypopnea Syndrome

Hypoxemia increases corrected QT dispersion (QTcD), which is the difference between the maximum and minimum QT intervals and is a strong risk factor for cardiovascular mortality. The aim of this study was to investigate the QTcD in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS), and the relationship between the QTcD and (123)I-metaiodobenzylguanidine (MIBG) cardiac imaging, which reflects cardiac sympathetic activity. A university hospital. Forty-eight OSAHS patients without cardiac diseases (mean [+/- SD] age, 45.9 +/- 10.8 years; apnea-hypopnea index [AHI] 51.9 +/- 18.5 events per hour) who underwent polysomnography before treatment and on the first night of nasal continuous positive airway pressure (nCPAP) treatment. Before and after nCPAP treatment was started, we measured the QTcD with computer software, before, during, and after sleep, as well as the washout rate of the MIBG administered for cardiac imaging. As a control, QTcD was also measured in the morning from 26 healthy subjects. Before treatment, the mean QTcD during sleep (65.0 +/- 14.6 ms) was greater than that before sleep (57.0 +/- 13.5 ms; p < 0.0001). Meanwhile, after 1 night of nCPAP therapy, the QTcD during sleep (50.6 +/- 11.4 ms) decreased from that before treatment (p < 0.0001) and was smaller than the QTcD before sleep (56.2 +/- 13.3 ms; p = 0.003). Before treatment, the QTcD during sleep correlated with the AHI (r = 0.38; p = 0.009) and the percentage of time that SaO(2) was < 90% (SaO(2) < 90% time) [r = 0.34; p = 0.018]. The QTcD did not correlate with the body mass index or the washout rate of MIBG. However, the washout rate of MIBG correlated with the AHI and the SaO(2) < 90% time. Nocturnal QTcD is increased in OSAHS patients but is decreased by nCPAP therapy independently of cardiac sympathetic function.

Relationship between cardiac 123I-metaiodobenzylguanidine imaging and the transcardiac gradient of neurohumoral factors in patients with dilated cardiomyopathy.

Cardiac sympathetic nervous function is altered in congestive heart failure (CHF) and the uptake and washout rate of cardiac 123I-metaiodobenzylguanidine (MIBG) are useful markers for evaluating the severity of it. To assess what parameters predict decreased uptake or increased washout rate of MIBG, the concentrations of neurohumoral factor in both the aorta (Ao) and coronary sinus (CS) were measured, as well as hemodynamic parameters by catheterization, in patients with dilated cardiomyopathy (DCM). MIBG imaging was performed within 1 week of cardiac catheterization. Regarding MIBG parameters, the correlation with the transcardiac gradient of norepinephrine (NE), brain natriuretic peptide (BNP) and hemodynamics was investigated. Stepwise multivariate regression analysis was used to determine which variables closely correlated with cardiac MIBG parameters. There was a significant increase in the NE level between the Ao (446 pg/ml) and the CS (727 pg/ml). According to stepwise multivariate regression analysis, the heart/mediastinum (H/M) ratio independently correlated with the transcardiac gradient of BNP (r=-0.480, p<0.01), and the washout rate independently correlated with the transcardiac gradient of NE (r=0.481, p<0.01). These findings indicate that the H/M ratio may reflect the transcardiac gradient of BNP, which implies the degree of left ventricular dysfunction and/or damage and the washout rate may reflect altered cardiac sympathetic nerve terminal in DCM patients with CHF, suggesting that both the H/M ratio and washout rate provide important information about the failing ventricle.

Evaluation of regional cardiac sympathetic innervation in congenital long QT syndrome using 123I-MIBG scintigraphy.

The aim of this study was to determine whether sympathetic imbalance in congenital long QT syndrome (LQTS) can be identified by cardiac sympathetic neuronal dysinnervation. 123I-metaiodobenzylguanidine (MIBG) is a tracer of the norepinephrine analogue which reflects the regional innervation and norepinephrine kinetics in cardiac sympathetic nerves. Sixteen patients with LQTS, who were members of 12 families, and 7 normal controls underwent MIBG scintigraphy. Myocardial SPET and planar images were obtained 15 min and 4 h after the injection of MIBG in each patient. The relative regional uptake (RRU) and regional washout rate (rWR) of MIBG at 4 h in each of nine regions were compared with those in the control group. The heat-to-mediastinum ratio (H/M) and global washout rate (GWR) were also calculated. The RRU, rWR, H/M and GWR showed no significant difference between LQTS patients and normal controls. Furthermore, the RRU in 96% of all regions in LQTS was within the mean +/- 2 standard deviations of that in the control group. Patients with LQTS have normal cardiac sympathetic innervation, as assessed by MIBG. The sympathetic imbalance hypothesis is unlikely to be attributed to an abnormal distribution and different regional norepinephrine kinetics of cardiac sympathetic nerves.

981-48 Washout Rate of Cardiac 123I-Metaiodobenzylguanidine Reflects Cardiac Chronotropic Reserve and Exercise Capacity In Patients with Chronic Heart Failure

The reduced reserve of cardiac sympathetic nerve activity is one of the important factors determining the exercise capacity in patients with chronic heart failure (CHF). Recently, 123I-metaiodobenzylguanidine (MIBG). a norepinephrine analogue, has been used to evaluate the integrity of sympathetic efferent innervation. However, little is known whether MIBG imaging reflects exercise capacity and cardiac sympathetic nerve reserve in patients with CHF. The purpose ofthis study was to examine the correlation between quantitative markers of MIBG cardiac imaging and exercise performance in patients with CHF. Twenty-one patients with CHF (NYHA I-III) underwent MIBG cardiac scintigraphy and a symptom-limited exercise using a multistage sitting ergometer. Planar images were obtained in anterior view of the chest 15 minutes and 4 hours after injection of MIBG. The heart to mediastinum uptake ratio (HIM) on the image 4 hours after MIBG injection and the washout rate of cardiac MIBG from 15 minutes to 4 hours (WR) were assessed as markers of sympathetic nerve activity. H/M significantly correlated with % fractional shortening (r = 0.71, p &lt; 0.001) obtained by echocardiography and the plasma level of noradrenaline (r = 0.59, p &lt; 0.01) at rest, but not with the maximal work load, peak heart rates and the increase in heart rates during exercise. On the other hand, WR significantly correlated with the maximal work load (r = 0.70, p &lt; 0.001). peak heart rates (r = 0.51, p &lt; 0.05) and the increase in heart rates during exercise (r = 0.57, p &lt; 0.01). Thus, H/M reflects cardiac dysfunction and sympathetic activity at resting state, whereas WR reflects cardiac chronotropic reserve and exercise capacity. It is, therefore, indicated that we need to take into consideration not only the myocardial uptake but also the washout rate of MIBG for monitoring sympathetic nerve activity in patients with CHF.