Cardiac metaiodobenzylguanidine uptake in patients with moderate chronic heart failure: relationship with peak oxygen uptake and prognosis

Prognostic value of myocardial 123I-metaiodobenzylguanidine (MIBG) parameters in patients with heart failure: a systematic review

AIMS

To derive a more precise estimate of the prognostic significance of myocardial 123I-metaiodobenzylguanidine (MIBG) parameters [early heart mediastinal ratio (H/M), late H/M, and myocardial washout] in heart failure (HF).

METHODS AND RESULTS

Eighteen studies with a total of 1755 patients, stratifying survival, and cardiac events in patients with HF by MIBG, were eligible for analysis. The pooled hazard ratio (HR) estimates for cardiac death and cardiac events associated with washout showed no significant heterogeneity and were 1.72 [95%CI (confidence interval), 1.72-2.52; P = 0.006] and 1.08 (95%CI: 1.03-1.12; P < 0.001), respectively. The pooled HR estimates for cardiac death and cardiac events associated with early H/M and late H/M showed significant heterogeneity (I2 > or = 75%). Limiting the pooling to the qualitative best three studies rendered I2 insignificant (I2 = 0) and resulted in a pooled HR of late H/M for cardiac death of 1.82 (95%CI: 0.80-4.12; P = 0.15) and for cardiac events of 1.98 (95%CI: 1.57-2.50; P < 0.001).

CONCLUSION

Our results indicate that patients with HF and decreased late H/M or increased myocardial MIBG washout have a worse prognosis compared with those with normal semi-quantitative myocardial MIBG parameters.

Age-related decrease in cardiopulmonary adrenergic neuronal function in children as assessed by I-123 metaiodobenzylguanidine imaging

BACKGROUND

Radioiodinated metaiodobenzylguanidine (MIBG) imaging has been used to evaluate adrenergic nerve activity in different organs. Cardiac and pulmonary MIBG uptake is important in predicting the prognosis of certain cardiopulmonary diseases. It has been reported that cardiac MIBG uptake decreases with age and is significantly lower in the elderly. However, there has been no systemic study on age-related changes in cardiac and pulmonary MIBG uptake in children. This study was undertaken to determine the changes in MIBG uptake in the developing heart and lung in children and adolescents.

METHODS AND RESULTS

MIBG scans of 44 children (16 female and 28 male; age range, 2 months to 19 years) without abnormal uptake were selected from a large pool of patients with whole-body MIBG imaging performed for evaluation of neuroblastoma. All of the selected subjects had a normal physiologic distribution of MIBG and no history of heart or lung diseases. The patients were divided into 4 groups by age: group 1, 0 to 24 months; group 2, 25 to 48 months; group 3, 49 to 72 months; and group 4, 73 months or greater. Cardiac and pulmonary MIBG uptake values (expressed as heart-to-mediastinum [H/M] ratio and lung-to-mediastinum [L/M] ratio, respectively) were determined and compared among the 4 groups. H/M and L/M ratios were noted to decrease with age. The mean H/M and L/M ratios were in group 1, 4.13 +/- 0.66 and 1.53 +/- 0.18, respectively; in group 2, 3.46 +/- 0.71 and 1.26 +/- 0.18, respectively; in group 3, 3.19 +/- 0.94 and 1.13 +/- 0.17, respectively; and in group 4, 2.84 +/- 0.48 and 1.14 +/- 0.14, respectively. There was a significant inverse correlation between H/M ratio and age (r = 0.711, P < .001) as well as between L/M ratio and age (r = 0.718, P < .001).

CONCLUSION

Cardiac and pulmonary MIBG uptake is inversely related to age in children.

I-123-mIBG myocardial imaging for assessment of risk for a major cardiac event in heart failure patients: insights from a retrospective European multicenter study

PURPOSE

Single-center experiences have shown that myocardial meta-iodobenzylguanidine (mIBG) uptake has prognostic value in heart failure (HF) patients. To verify these observations using a rigorous clinical trial methodology, a retrospective review and prospective quantitative reanalysis was performed on a series of cardiac (123)I-mIBG scans acquired during a 10-year period at six centers in Europe.

METHODS

(123)I-mIBG scans obtained on 290 HF patients [(262 with left ventricular ejection fraction (LVEF) < 50%)] from 1993 to 2002 were reanalyzed using a standardized methodology to determine the heart-to-mediastinum ratio (H/M) on delayed planar images. All image results were verified by three independent reviewers. Major cardiac events [MCEs; cardiac death, cardiac transplant, potentially fatal arrhythmia (including implantable cardioverter-defibrillator discharge)] during 24-month follow-up were confirmed by an adjudication committee.

RESULTS

MCEs occurred in 67 patients (26%): mean H/M ratio was 1.51 +/- 0.30 for the MCE group and 1.97 +/- 0.54 for the non-MCE group (p < 0.001). Two-year event-free survival using an optimum H/M ratio threshold of 1.75 was 62% for H/M ratio less than 1.75, 95% for H/M ratio greater than or equal to 1.75 (p < 0.0001). Logistic regression showed H/M ratio and LVEF as the only significant predictors of MCE. Using the lower and upper H/M quartiles of 1.45 and 2.17 as high- and very low-risk thresholds, 2-year event-free survival rates were 52% and 98%, respectively. Among patients with LVEF < or = 35% and H/M > or = 1.75 (n = 73), there were nine MCEs because of progressive HF and only one because of an arrhythmia.

CONCLUSION

Application of a clinical trial methodology via the retrospective reanalysis of (123)I-mIBG images confirms the previously reported prognostic value of this method in HF patients, including potential identification of a quantitative threshold for low risk for cardiac mortality and potentially fatal ventricular arrhythmias.

Variations in 123I-metaiodobenzylguanidine (MIBG) late heart mediastinal ratios in chronic heart failure: a need for standardisation and validation

Background

There is lack of validation and standardisation of acquisition parameters for myocardial ¹²³I-metaiodobenzylguanidine (MIBG). This lack of standardisation hampers large scale implementation of ¹²³I-MIBG parameters in the evaluation of patients with chronic heart failure (CHF).

Methods

In a retrospective multi-centre study ¹²³I-MIBG planar scintigrams obtained on 290 CHF patients (82% male; 58% dilated cardiomyopathy; New York Heart Association [NYHA classification] > I) were reanalysed to determine the late heart-to-mediastinum ratio (H/M).

Results

There was a large variation in acquisition parameters. Multivariate forward stepwise regression showed that a significant proportion (31%, p < 0.001) of the variation in late H/M could be explained by a model containing patient-related variables and acquisition parameters. Left ventricular ejection fraction (p < 0.001), type of collimation (p < 0.001), acquisition duration (p = 0.001), NYHA class (p = 0.028) and age (p = 0.034) were independent predictors of late H/M.

Conclusions

Acquisitions parameters are independent contributors to the variation of semi-quantitative measurements of cardiac ¹²³I-MIBG uptake. Improved standardisation of cardiac ¹²³I-MIBG imaging parameters would contribute to increased clinical applicability for this procedure.

Improvement in cardiac adrenergic function post biventricular pacing for heart failure

AIMS

We investigated whether biventricular (BiV) pacing favourably affects cardiac sympathetic activity in heart failure (HF).

METHODS AND RESULTS

In 10 HF patients treated with BiV pacing, we assessed cardiac sympathetic activity by metaiodobenzylguanidine ((123)I-MIBG) imaging. Patients were randomized in a double-blinded crossover fashion, for two weeks of either inactivation of BiV pacing or BiV pacing, with crossover to the alternate group for a further two weeks. After randomization blocks, cardiac (123)I-MIBG imaging and a 6 min walk test were performed. BiV pacing was associated with significant improvements in cardiac (123)I-MIBG uptake reflected by increases in early (BiV 1.71 +/- 0.09 vs. non-BiV 1.63 +/- 0.06, P = 0.03) and late (at 4 h) heart to mediastinal ratio of uptake (BiV 1.54 +/- 0.08 vs. non-BiV 1.45 +/- 0.06, P = 0.03). Additionally, pulmonary (123)I-MIBG uptake, measured as lung to mediastinal ratio, significantly improved (P = 0.009). Six-minute walk and systolic blood pressure tended to improve with BiV vs. non-BiV pacing (P = 0.09).

CONCLUSION

In patients with stable HF, BiV pacing is associated with long-term improvements in cardiac sympathetic nerve activity, as reflected by improvements in cardiac (123)I-MIBG uptake. This is a potential mechanism for morbidity and mortality benefits observed in larger studies.

Prediction of sudden death in patients with mild-to-moderate chronic heart failure by using cardiac iodine-123 metaiodobenzylguanidine imaging

OBJECTIVE

To evaluate the usefulness of cardiac iodine-123 (123I) metaiodobenzylguanidine (MIBG) imaging as a predictor of sudden death in patients with chronic heart failure (CHF).

DESIGN AND SETTING

Prospective cohort study in a tertiary referral centre.

PATIENTS

97 outpatients with CHF with a radionuclide left ventricular ejection fraction <40% (mean (SD) 29% (7.5%)).

INTERVENTIONS

At study entry, cardiac I-123 MIBG imaging was performed. The cardiac MIBG heart-to-mediastinum ratio (H/M) and washout rate (WR) were obtained from MIBG imaging.

MAIN OUTCOME MEASURES

Patients were assigned to two groups based upon 27% of WR, which was the mean (2SD) control WR. 48 of 97 patients with CHF had abnormal WR (> or =27%), whereas the remaining 49 patients had normal WR (<27%). All the study patients were then followed up.

RESULTS

During the mean (SD) follow-up period of 65 (29) months, 12 (25%) patients in the abnormal WR group and 2 (4%) patients in the normal WR group died suddenly. Kaplan-Meier analysis revealed that sudden death was more often observed in patients with abnormal WR than those with normal WR (p = 0.001). On Cox regression analysis, MIBG WR, H/M on the delayed image and H/M on the early image were significantly associated with sudden death.

CONCLUSION

Cardiac MIBG imaging would be useful for predicting sudden death in patients with CHF.

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.

The relationship between variables of 123-I-metaiodobenzylguanidine cardiac imaging and clinical status of the patients with diastolic heart failure

BACKGROUND

The status of cardiac sympathetic nerve activity in patients with diastolic heart failure has not been fully understood. 123-I-metaiodobenzylguanidine cardiac images are valuable for evaluating cardiac sympathetic nerve activity.

METHODS

We obtained 123-I-metaiodobenzylguanidine cardiac images from 34 consecutive patients with moderate heart failure and an ejection fraction of > or = 45%.

RESULTS

The decay-corrected washout rate of 123-I-metaiodobenzylguanidine correlated with each plasma concentration of brain natriuretic peptide (standardized correlation coefficient=0.305, p<0.05), New York Heart Association functional class (standardized correlation coefficient=0.364, p<0.02), and exercise capacity (standardized correlation coefficient=-0.388, p<0.04). A multiple regression analysis revealed that the washout rate independently predicted plasma concentration of brain natriuretic peptide (standardized regression coefficient=0.367, p<0.02). In a univariate regression, the washout rate did not significantly correlate with the presence of ischemic heart disease (p=0.254); in a multivariate regression, the presence of ischemic heart disease did not predict the washout rate. For the 14 patients with sinus rhythm, there was a marginal negative correlation between the E/A velocity ratio of the transmitral flow and washout rate (standardized correlation coefficient=-0.518, p<0.07).

CONCLUSIONS

In diastolic heart failure, cardiac sympathetic nerve activity increases proportionally to severity of the disease.

The effect of beta-adrenergic receptor antagonism in cardiac sympathetic neuronal remodeling in patients with heart failure

BACKGROUND

beta-adrenergic receptor antagonism with drugs like carvedilol slows the progression of heart failure by an undefined mechanism. (123)I-metaiodobenzylguanidine (MIBG) is an analog of norepinephrine used to study cardiac sympathetic function.

METHODS AND RESULTS

In this double-blind randomized, placebo-controlled study, we used MIBG imaging to evaluate the effect of carvedilol (n=15) or placebo (n=7) on neuronal norepinephrine reuptake in patients with heart failure due to idiopathic dilated cardiomyopathy, with LVEF less than 35% and functional class II or III. The drug was begun at 6.25 mg b.i.d. and titrated up to 25 mg t.i.d, as tolerated. Thorax planar scintigraphy images were obtained 15 min (Initial) and 4 h (Late) after MIBG injection at baseline (t(0)) as well as 2 months (t(1)) and 6 months (t(2)) after drug initiation. The multifarious statistical technique of profile analysis was applied and p< or =0.05 was considered significant. The heart/mediastinum MIBG uptake (H/M ratio) was calculated from these images. On the Initial images, the H/M ratio was 1.64+/-0.24 (t(0)), 1.71+/-0.21 (t(1)), and 1.87+/-0.34 (t(2)) in the carvedilol group and 1.68+/-0.42 (t(0)), 1.81+/-0.45 (t(1)), and 1.69+/-0.44 (t(2)) in controls (p=0.0455). On the Late images, the H/M ratio was 1.39+/-0.24 (t(0)), 1.53+/-0.23 (t(1)), and 1.64+/-0.36 (t(2)) in the carvedilol group, and 1.49+/-0.45 (t(0)), 1.53+/-0.47 (t(1)), and 1.47+/-0.41 (t(2)) in controls (p=0.0513).

CONCLUSION

Compared with placebo, the addition of carvedilol to existing heart failure treatment incites the reverse remodeling of cardiac sympathetic nervous system function.

Cardiac resynchronization induces favorable neurohumoral changes

AIM

The aim of this article is to examine whether cardiac resynchronization therapy (CRT) induces improvements in the neurohumoral system.

METHODS AND RESULTS

Thirteen patients with HF (left ventricular (LV) ejection fraction <35%) were included. Before and after 6 months of CRT, myocardial (123)I-metaiodobenzylguanidine ((123)I-MIBG) uptake indices, used as an index of neural norepinephrine reuptake and retention, and brain natriuretic peptide (BNP) levels, used as an index of LV end-diastolic pressure, NYHA classification and echocardiographic indices were assessed. Six months of CRT resulted in significant improvement in (1) NYHA classification and reduction in QRS width (P < 0.001), (2) decrease of LV end-diastolic diameter (P = 0.005), LV end-systolic diameter (P = 0.005), septal to lateral delay (P = 0.01) and mitral regurgitation (MR, P = 0.04), (3) delayed (123)I-MIBG heart/mediastinum ratios improved (P = 0.03) and (123)I-MIBG washout decreased (P = 0.001), and (4) BNP levels decreased (P = 0.001).

CONCLUSIONS

Parallel to significant functional improvement and echocardiographic reverse remodeling and resynchronization, our data indicate that CRT induces favorable changes in the neurohumoral system.

Prognostic value of iodine-123-metaiodobenzylguanidine myocardial uptake and heart rate variability in chronic congestive heart failure secondary to ischemic or idiopathic dilated cardiomyopathy

Autonomic nervous system dysfunction is common in congestive heart failure (CHF) and is believed to predispose patients to an increased risk of death. This study aimed to assess the prognostic significance of heart rate variability (HRV) measurements in conjunction with scintigraphic imaging using metaiodobenzylguanidine (MIBG) labeled with iodine-123 (I-123-MIBG), which detects abnormalities in autonomic nervous activity, in patients with stable CHF during optimal medical treatment. The study population included 52 patients (56 +/- 12 years of age) with a mean left ventricular ejection fraction of 31 +/- 12%. All underwent I-123-MIBG scanning and 24-hour ambulatory electrocardiographic monitoring for the analysis of HRV on entrance into the study. The heart/mediastinum MIBG uptake ratio was calculated. HRV analysis included the assessment of time- and frequency-domain variables. During the 2-year follow-up, 14 patients (27%) died. MIBG uptake at 1 hour was less (1.39 +/- 0.10) in nonsurvivors than in survivors (1.50 +/- 0.16; p = 0.013). In univariate Cox regression analysis, MIBG uptake was a significant prognostic factor (p = 0.038, hazard ratio [HR] 0.017, 95% confidence interval [CI] 0.00 to 0.79). Time- and frequency-domain variables were similar in survivors and nonsurvivors. However, high-frequency power was associated with an increased risk for sudden death (HR 0.310, 95% CI 0.101 to 0.954, p = 0.041) but not with all-cause mortality. In conclusion, cardiac I-123-MIBG imaging identifies patients with CHF at high risk of dying and may be a more reliable predictor of overall mortality than HRV.

Cardiac metaiodobenzylguanidine activity can predict the long-term efficacy of angiotensin-converting enzyme inhibitors and/or beta-adrenoceptor blockers in patients with heart failure

PURPOSE

Although the benefits of treatment with angiotensin-converting enzyme (ACE) inhibitors and beta-blockers are well known, no method has as yet been established to predict the efficacy of drug therapy. This study tested whether cardiac 123I-metaiodobenzylguanidine (MIBG) activity is of prognostic value and can predict the improvement in heart failure patients resulting from treatment with ACE inhibitors and/or beta-blockers.

METHODS

Following quantification of the heart-to-mediastinum ratio (HMR) of MIBG activity, 88 patients with heart failure who were treated with ACE inhibitors and/or beta-blockers (treated group) and 79 patients with heart failure who were treated conventionally without the aforementioned agents, and who served as controls, were followed up for 43 months with a primary endpoint of cardiac death.

RESULTS

The treated group had a significantly lower prevalence of cardiac death and a significantly lower mortality at 5 years compared with the control group (15% vs 37% and 21% vs 42%, p<0.05, respectively). Multivariate analysis revealed that significant predictors were HMR, age, nitrate use and ventricular tachycardia for the treated group, and HMR, nitrate use and NYHA class for the control group. The drug treatment significantly reduced mortality from 36% to 12% when HMR was 1.53 or more and from 53% to 37% when HMR was less than 1.53. The reduction in risk of mortality within 5 years in patients without a severe MIBG defect (67%) was twice that in patients with such a defect (32%) (p<0.05).

CONCLUSION

The reduction in mortality risk achieved by using ACE inhibitors and/or beta-blockers is associated with the severity of impairment of cardiac MIBG uptake. Cardiac MIBG activity can consequently be of long-term prognostic value in predicting the effectiveness of such treatment in patients with heart failure.

Cardiac neurotransmission SPECT imaging

The sympathetic nervous system has great influence on cardiovascular physiology. Cardiac neurotransmission single photon emission computed tomography (SPECT) imaging allows in vivo noninvasive assessment of presynaptic reuptake and storage of neurotransmitters, which offers characterization of the cardiac neuronal function in different diseases of the heart and other altered metabolic or functional conditions. Therefore assessment of the integrity of cardiac sympathetic innervation may help in the diagnosis of these disorders, as well as in prognostication, and will result in better therapy and outcome. At present, the most widely available SPECT tracer by which to assess cardiac neurotransmission is metaiodobenzylguanidine labeled with iodine 123. This article focuses on reviewing the characteristics of cardiac SPECT imaging with I-123 metaiodobenzylguanidine and its role in the assessment of pathophysiologic changes during relevant clinical conditions.

Altered Effects of Angiotensin II Type 1 and Type 2 Receptor Blockers on Cardiac Norepinephrine Release and Inotropic Responses During Cardiac Sympathetic Nerve Stimulation in Aorto-Caval Shunt Rats

BACKGROUND

Inhibition of the sympathetic nervous and renin - angiotensin systems has become an important strategy in the treatment of chronic heart failure. However, direct evidence of how inhibition of the renin - angiotensin system alters sympathetic activity in a diseased heart is lacking.

METHODS AND RESULTS

Four weeks after abdominal aorto-caval (AV) shunting or sham operation in rats, the hearts were retrogradely perfused in vivo and the left ventricles contracted isovolumetrically at 300 beats/min. Sympathetic nerve stimulation (SNS) was performed in the baseline state and repeated with an infusion of the angiotensin II (A-II) type 1 receptor (AT(1)-R) blocker, losartan, the A-II type 2 receptor (AT(2)-R) blocker, PD123319, or A-II. Norepinephrine (NE) overflow and left ventricular (LV) inotropic responses during baseline SNS were lower in the AV shunt rats. Losartan did not change the NE overflow or the LV inotropic responses to SNS in the sham rats, but did increase them in the AV shunt rats. PD123319 changed neither parameter in the sham rats, but decreased both in the AV shunt rats. A-II enhanced the NE overflow but attenuated the LV inotropic responses to SNS in the sham rats, but attenuated both in the AV shunt rats.

CONCLUSIONS

The effects of A-II via the AT(1)-R and AT(2)-R on the adrenergic drive in the heart were altered significantly in volume overload hypertrophy induced by AV shunting.

Sympathetic nervous system function as measured by I-123 metaiodobenzylguanidine predicts transplant-free survival in heart failure patients with idiopathic dilated cardiomyopathy

BACKGROUND

Heightened activity of the sympathetic nervous system in heart failure patients is a major contributor to disease progression and death. I-123 metaiodobenzylguanidine (MIBG) provides an accurate, noninvasive method to assess cardiac sympathetic nerve activity.

METHODS

Thirty-seven patients with New York Heart Association class II, III, or IV heart failure underwent baseline measurement of I-123 MIBG heart-to-mediastinum ratios, maximum oxygen consumption, radionuclide left ventricular ejection fraction, and plasma norepinephrine levels. Patients were followed 48.8+/-8.6 months to endpoints of cardiac death or transplantation. The heart-to-mediastinum ratio of I-123 MIBG activity measured 15 minutes after injection was the only independent predictor of transplant-free survival (P<.0001). I-123 MIBG imaging at 15 minutes identified patients with subsequent cardiac transplantation or death with a sensitivity of 92% and specificity of 72%, whereas the corresponding values for maximum oxygen consumption were 75% and 56%. By Kaplan-Meier survival analysis, the time to a cardiac endpoint was significantly shorter in patients with a 15-minute I-123 MIBG heart-to-mediastinum ratio below the group mean ratio of 1.536, compared with patients with a preserved I-123 MIBG ratio. Maximum oxygen consumption was not predictive of time to cardiac transplant or death.

CONCLUSIONS

In this study of patients with congestive heart failure resulting from dilated cardiomyopathy, a 15-minute heart-to-mediastinum ratio of I-123 MIBG activity provided more accurate prediction of cardiac transplantation or death than other standard clinical tests.

Scatter correction by two-window method standardizes cardiac I-123 MIBG uptake in various gamma camera systems

Heart to mediastinum count ratio (H/M) has been commonly utilized as an indicator of myocardial I-123 MIBG uptake. However, normal ranges of H/M were markedly different among various gamma camera systems. The purpose of this study was to clarify whether scatter correction by two-window method standardizes H/M among various gamma camera systems.

METHODS

Scatter uncorrected and corrected MIBG imaging was acquired in phantom and human studies in combination with low energy high-resolution collimator (LEHR) and medium energy collimator (MEC). For scatter correction, energy window width of 159 keV +/- 10% was applied to main window imaging and 193 keV +/- 9.5% was applied to upper window imaging for scatter correction.

RESULTS

In phantom study, a significant difference was observed in uncorrected H/M among three gamma camera systems using LEHR or MEC (2.09 +/- 0.06 vs. 2.58 +/- 0.03 in GCA7200 camera, 2.00 +/- 0.07 vs. 2.42 +/- 0.06 in DS7 camera and 2.16 +/- 0.04 vs. 2.67 +/- 0.07 in Vertex plus camera). However, there was no significant difference in corrected H/M among the three gamma camera systems, either with LEHR or MEC (2.70 +/- 0.07 vs. 2.69 +/- 0.07 in GCA7200 camera, 2.66 +/- 0.08 vs. 2.61 +/- 0.05 in DS7 camera and 2.66 +/- 0.05 vs. 2.61 +/- 0.05 in Vertex plus camera). In human study, uncorrected H/M in DS7 camera with LEHC was significantly lower than that in GCA7200 camera with MEC (1.60 +/- 0.37 vs. 1.85 +/- 0.54, N = 14). In contrast, the difference was insignificant in corrected H/M (2.12 +/- 0.59 vs. 2.16 +/- 0.68). There was a very excellent correlation in corrected H/M between DS7 and GCA7200 cameras (r = 0.991, p < 0.001).

CONCLUSION

This study demonstrated that scatter correction by the two-window method standardizes the H/M in MIBG scintigraphy either with LEHR or MEC. Scatter corrected H/M can be applied to measure a standardized parameter of MIBG uptake in human clinical studies using various gamma camera systems.

Technetium 99m-labeled tetrofosmin and iodine 123-labeled metaiodobenzylguanidine scintigraphy in the assessment of transmyocardial laser revascularization

OBJECTIVE

Transmyocardial laser revascularization is a new technique that improves symptoms in patients with refractory angina not amenable to conventional revascularization. The aim of this study was to assess whether transmyocardial laser revascularization produces changes in innervation, perfusion scintigraphy, or both that could explain the benefit to patients.

METHODS

Sixteen patients (12 men and 4 women; mean age, 60 +/- 8 years) with coronary artery disease were studied. Transmyocardial laser revascularization was performed in 39 myocardial areas supplied by a stenotic vessel. A technetium 99m-labeled tetrofosmin stress-rest tomographic scan and iodine 123-labeled metaiodobenzylguanidine planar scans were performed before and after transmyocardial laser revascularization (3 and 12 months later) to evaluate myocardial perfusion and innervation. Stress and rest perfusion images were quantified on a polar map. Ischemia uptake was also defined as the difference between rest and stress uptake for each area. Innervation planar images were visually analyzed and semiquantified.

RESULTS

A significant decrease in angina class from baseline was observed at 3, 6, and 12 months after transmyocardial laser revascularization (P <.005). A significant decrease in ischemia uptake was also found between the pre-transmyocardial laser revascularization and the post-transmyocardial laser revascularization studies in treated areas (P <.001). A significant improvement in stress myocardial perfusion at 3 and 12 months after transmyocardial laser revascularization was only found in treated areas that were considered ischemic in the pre-transmyocardial laser revascularization study (P <.05). At 3 months, a significant myocardial innervation worsening was observed in treated areas (P <.001), with partial recovery at 12 months (P <.05).

CONCLUSION

The transmyocardial laser revascularization mechanism involves both perfusion improvement and denervation, mainly at 3 months, that partially recovered at 12 months.

Relation of cardiac sympathetic innervation to proinflammatory cytokine levels in patients with heart failure secondary to idiopathic dilated cardiomyopathy

Experimental studies have shown that cytokine production by the heart may be regulated by sympathetic nervous system stimulation of cardiac beta-adrenergic receptors. Proinflammatory cytokine levels are increased in heart failure, whereas cardiac fixation of 123-I-metaiodobenzylguanidine (MIBG) has been used to study myocardial adrenergic innervation. This study was designed to assess the relation between cardiac MIBG uptake and circulating levels of proinflammatory cytokines in patients with idiopathic dilated cardiomyopathy (IDC). Forty-seven patients (12 women; mean age 56.5 +/- 9 years) with angiographically proved IDC, in New York Heart Association functional classes II to III, and who had left ventricular ejection fraction 30.6 +/- 9.5%, and 20 healthy controls were studied with planar MIBG. The early (10 minutes) and late (4 hours) heart to mediastinum uptake ratio and washout were calculated. Circulating plasma levels of interleukins (IL)-1 and IL-6, tumor necrosis factor-alpha, and solube receptors of TNF (sTNFR) I and II were measured. The patient group had significantly lower values of MIBG uptake at 10 minutes (p <0.001) and 4 hours (p <0.001) and higher washout (p <0.001) than the controls. Late MIBG uptake was significantly correlated with New York Heart Association class (r = -0.42, p = 0.02), left ventricular ejection fraction (r = 0.34, p = 0.01), left ventricular systolic wall stress (r = -0.40, p = 0.05), oxygen consumption at peak exercise (r = 0.32, p = 0.03), IL-1 (r = -0.55, p <0.001), TNF (r = -0.33, p = 0.02), and sTNFRII (r = -0.44, p = 0.001). Multivariate linear regression analysis revealed that MIBG at 4 hours was independently associated with IL-1 levels (p <0.001). Thus, reduced cardiac sympathetic innervation in heart failure is associated with elevated levels of inflammatory cytokines, suggesting that it has a potential inflammatory effect via modulation of the cardiac production of these cytokines.

Comparison of the prognostic value of cardiac iodine-123 metaiodobenzylguanidine imaging and heart rate variability in patients with chronic heart failure: a prospective study

OBJECTIVES

We sought to prospectively compare the prognostic value of cardiac iodine-123 (I-123) metaiodobenzylguanidine (MIBG) imaging with that of heart rate variability (HRV) in patients with mild-to-moderate chronic heart failure (HF).

BACKGROUND

Cardiac I-123 MIBG imaging, which reflects cardiac adrenergic nerve activity, provides prognostic information on chronic HF patients. Reduced HRV, indicating derangement in cardiac autonomic control, was also reported to be associated with a poor prognosis in chronic HF patients.

METHODS

At study entry, I-123 MIBG imaging and 24-h Holter monitoring were performed in 65 chronic HF outpatients with a radionuclide left ventricular ejection fraction <40%. The cardiac MIBG heart to mediastinum ratio (H/M) and washout rate (WR) were obtained from MIBG imaging. The time and frequency domain parameters of HRV were calculated from 24-h Holter recordings.

RESULTS

At a mean follow-up of 34 +/- 19 months, WR (p < 0.0001), H/M on the delayed image (p = 0.01), and normalized very-low-frequency power (n-VLFP) (p = 0.047) showed a significant association with the cardiac events (sudden death in 3 and hospitalization for worsening chronic HF in 10 patients) on univariate analysis. Multivariate analysis revealed that WR was the only independent predictor of cardiac events, although the predictive accuracy for the combination of abnormal WR and n-VLFP significantly increased, compared with that for abnormal WR (82% vs. 66%, p < 0.05).

CONCLUSIONS

Cardiac MIBG WR has a higher prognostic value than HRV parameters in patients with chronic HF. The combination of abnormal WR and n-VLFP would be useful to identify chronic HF patients at a higher risk of cardiac events.

Clinical Value of Iodine-123 Beta-Methyliodophenyl Pentadecanoic Acid (BMIPP) Myocardial Single Photon Emission Computed Tomography for Predicting Cardiac Death Among Patients With Chronic Heart Failure

In the present study, the effectiveness of 123I-beta-methyliodophenyl pentadecanoic acid (BMIPP) single photon emission computed tomography (SPECT) for predicting cardiac death of patients with chronic heart failure was evaluated. Abnormalities of fatty acid metabolism are found in patients with chronic heart failure and BMIPP was developed as a tracer for scintigraphic assessment of myocardial fatty acid utilization. The study group comprised 74 patients with chronic heart failure with a left ventricular ejection fraction (LVEF) <45% on left ventriculography or radionuclide angiocardiography. They underwent both 201Tl SPECT and BMIPP SPECT. The uptake of tracer was scored semiquantitatively from 0 (normal) to 4 (defect) in 20 segments and a total defect score (TDS) for all 20 segments was calculated. On planar images the mediastinum to heart count ratio (H/M) was calculated for the BMIPP and Tl studies, and the H/M(BMIPP):H/M(Tl) (H/M(BMIPP) divided by H/M(Tl)) was also calculated. The mean follow-up period was 660 days and there were 17 cases of cardiac death. Multivariate analysis identified H/M(BMIPP):H/M(Tl) (p<0.05) and LVEF (p<0.05) as independent predictors of cardiac death. The receiver-operating characteristic curve of H/M(BMIPP):H/M (Tl) was situated to the left relative to LVEF. Analysis of the myocardial metabolism by BMIPP SPECT can predict the high-risk patients with chronic heart failure.

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

OBJECTIVE

To assess the prognostic value of I-123 metaiodobenzylguanidine (MIBG) scintigraphy findings, and establish the most appropriate method for calculating myocardial MIBG activity in patients with left ventricular dysfunction due to cardiomyopathy (CM).

METHODS

Predictors of cardiac death related to progressive heart failure (HF) were examined in 150 patients with CM (80 patients with idiopathic CM and 70 patients with ischemic CM). All patients underwent MIBG scintigraphy at rest and other hemodynamic studies when their clinical status was stable. MIBG scintigrams were obtained 15 minutes and 4 hours after the injection of the isotope. The parameters for quantification of myocardial MIBG activity were heart/mediastinal activity ratio (H/M) and myocardial washout rate (WR). The WR was calculated with and without background (BG) correction.

RESULTS

The WR showed better correlation with plasma norepinephrine and left ventricular ejection fraction after BG correction. During a mean follow-up period of 33 +/- 9 (7 to 54) months, 12 patients died due to HF; 7 patients due to progressive HF and 5 patients due to sudden cardiac death. Cox regression analysis indicated, the H/M and the WR with and withoutBG correction, were significant predictors of cardiac death (Wald chi-squared value: H/M [ 15 min] = 9.7, H/M [4 hr] = 19.5, WR with BG correction = 29.9, WR without BG correction = 12.6). WR prognostic value was better after BG correction, and a high WR with BG correction was the only independent predictor of cardiac death (relative risk [RR] = 1.174, p < 0.0001).

CONCLUSIONS

Accelerated WR is a powerful predictor of the patient's prognosis and BG correction is essential for calculating WR.

Cardiac 123 I-MIBG imaging and clinical variables in risk stratification in patients with heart failure treated with beta blockers

Both myocardial m-[123I]iodobenzylguanidine (123I-MIBG) uptake and plasma norepinephrine are markers of sympathetic activation in heart failure and have been shown to portend a poorer prognosis. However, these observations were noted before treatment with beta blockers became part of standard clinical practice. Fifty-eight patients with chronic heart failure (New York Heart Association functional class II and III, ejection fraction <35%; 53% ischaemic cardiomyopathy) were prospectively studied with a mean follow-up of 36 months. During the observational period, 17 patients (29.3%) had a predefined event (death and heart transplantation). All prognostic parameters were obtained before beta blocker therapy was initiated. In both uni- and multivariate analysis, the heart-mediastinum ratio of 123I-MIBG uptake did not correlate with cardiovascular mortality. In the multivariate Cox regression analysis, plasma norepinephrine, peak oxygen consumption, end-diastolic volume as measured by echocardiography and exercise performance during bicycling and walking had prognostic significance in patients with heart failure treated with beta blockers in addition to angiotensin-converting enzyme inhibitors.

Prognostic value of repeated 123I-metaiodobenzylguanidine imaging in patients with dilated cardiomyopathy with congestive heart failure before and after optimized treatments--comparison with neurohumoral factors

The present study was undertaken to assess whether repeated measurement of cardiac 123I-metaiodobenzylguanidine (MIBG) imaging parameters before and after optimized treatments is useful for predicting the prognosis of patients with congestive heart failure (CHF) resulting from dilated cardiomyopathy (DCM). The subjects were 85 consecutive patients with DCM who had a left ventricular ejection fraction (LVEF) of less than 45%. The MIBG and the concentrations of neurohumoral factors were measured at baseline and after 6 months of optimized treatments. Cox proportional hazards analysis was performed to assess the various parameters before and after treatment. Twenty-three patients had a cardiac event (12 died; 11 hospitalized) during a mean follow-up period of 2 years. Although there was no difference between the baseline heart to mediastinum (H/M) ratio measured by MIBG between survivors and nonsurvivors, the H/M ratio was significantly decreased in nonsurvivors after 6 months. Multivariate analysis revealed that a high plasma concentration of brain natriuretic peptide level after 6 months (p=0.0049) and absolute changes in the H/M ratio (p=0.0046) were independent predictors of mortality. Comparison of the H/M ratio on MIBG imaging before and after optimized additional treatment provided useful information for predicting mortality and was independent of clinical and neurohumoral factors previously shown to be associated with poor prognosis in patients with DCM.

Myocardial contractile reserve under low doses of dobutamine and improvement of left ventricular ejection fraction with treatment by carvedilol

To examine the ability of myocardial contractile reserve (MCR) assessment to predict the improvement of left ventricular ejection fraction with treatment by carvedilol, a prospective study was undertaken in 85 patients with chronic heart failure and left ventricular ejection fraction < 45%. Low dose dobutamine echocardiography (DSE), a 6-min walk test and measured brain natriuretic peptide (BNP) were assessed in all the patients. Patients were separated into two groups. Group A were patients without any myocardial reserve and group B patients with a myocardial contractile reserve defined as an increment of more than 20% of the resting left ventricular ejection fraction during dobutamine infusion. The two groups differed for percentage of ischemic cardiomyopathy (67.8 in group A vs. 29.7% in group B P = 0.028), 6-min walk test performance (respectively, 343 vs. 415 meters P < 0.05) and BNP plasma levels (respectively, 184.5 vs. 70.1 P < 0.02) but not for left ventricular ejection fraction or NYHA class. During DSE, MCR and heart rate variation was higher in group B than in group A. At the end of the follow up, LVEF increased and NYHA class decreased in group B but not in group A. In multivariate analysis the existence of MCR could predict the improvement of LVEF with treatment by carvedilol. In our study, studying MCR could help to predict patients who will improve their LVEF with carvedilol prior to the administration of the treatment.

Prognostic significance of cardiac (123)I metaiodobenzylguanidine imaging for mortality and morbidity in patients with chronic heart failure: a prospective study

OBJECTIVE

To determine whether cardiac iodine-123 metaiodobenzylguanidine ((123)I MIBG) imaging is useful in predicting the prognosis of patients with chronic heart failure.

DESIGN

Cardiac (123)I MIBG imaging was done on entry to the study. The cardiac MIBG washout rate was calculated from anterior chest view images obtained 20 and 200 minutes after injection of the isotope. Study patients were divided into two groups with washout rates above and below 27% (the mean value + 2 SD obtained in 20 normal subjects), and were then followed up.

SETTING

Tertiary referral centre.

PATIENTS

79 patients with chronic heart failure in whom the left ventricular ejection fraction was less than 40%.

RESULTS

There were 37 patients in group 1 (washout rate of >/= 27%) and 42 in group 2 (< 27%). During a follow up period of between 1 and 52 months, eight patients died suddenly and five died of worsening heart failure in group 1, while none died in group 2; 13 patients in group 1 and four in group 2 were admitted to hospital for progressive heart failure. Kaplan-Meier analysis showed that group 1 had a significantly higher mortality and morbidity (p = 0.001 and p < 0.001, respectively) than group 2.

CONCLUSIONS

Cardiac (123)I MIBG washout rate seems to be a good predictor of prognosis in patients with chronic heart failure.

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.

Relationship between cardiac metaiodobenzylguanidine uptake and hemodynamic, functional and neurohormonal parameters in patients with heart failure

BACKGROUND

Sympathetic activation plays a pivotal role in heart failure attributing to the disease process and symptoms of the patient. Myocardial sympathetic activity can be visualized using radioiodinated metaiodobenzylguanidine 123I-MIBG, a structural analogue of norepinephrine (NE).

AIM OF THE STUDY

We investigated whether a relation exists between myocardial MIBG uptake and different functional, hemodynamic and neurohormonal parameters in patients with chronic heart failure.

METHODS AND RESULTS

The study comprised 52 patients with stable congestive heart failure functional class II or III and left ventricular ejection fractions of <35%. The heart/mediastinum ratio (H/M ratio) was calculated to quantify myocardial MIBG uptake. A significant correlation was found between peak oxygen consumption and maximal exercise duration as exercise parameters and H/M ratio of MIBG (R, respectively, 0.36 and 0.4, P<0.05). From all other measured parameters, only plasma NE showed a significant correlation with the H/M ratio of MIBG.

CONCLUSION

Cardiac sympathetic activity, as measured by myocardial MIBG uptake, is correlated with peak exercise parameters.

Comparative left ventricular functional and neurohumoral effects of chronic treatment with carvedilol versus metoprolol in patients with dilated cardiomyopathy

The efficacy of treating dilated cardiomyopathy with metoprolol was compared with that of carvedilol. Metoprolol was administered to 29 patients, and carvedilol to 62. Patients who could not be dosed with up to 40 mg daily of metoprolol or 20 mg daily of carvedilol were defined as intolerant. As well as the tolerability of these beta-blockers, the effects on left ventricular end-diastolic dimension (LVDd), fractional shortening (FS), plasma atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) concentrations, the delayed heart and mediastinum (H/M) ratio determined from metaiodobenzylguanidine imaging were compared. Drug intolerance occurred in 24% of patients in the metoprolol group and 19% in the carvedilol group. Among the drug-tolerant patients, LVDd, FS and plasma BNP concentration improved in both groups and to the same degree. Only 25% of drug-tolerant patients in the metoprolol group had a delayed H/M ratio below 1.9 compared with 57% in the carvedilol group. Both metoprolol and carvedilol, when tolerated, improve cardiac function and neurohumoral factors to the same degree. However, carvedilol is preferable to metoprolol for patients with a low delayed H/M ratio.

The role of neuronal and extraneuronal plasma membrane transporters in the inactivation of peripheral catecholamines

Catecholamines are translocated across plasma membranes by transporters that belong to two large families with mainly neuronal or extraneuronal locations. In mammals, neuronal uptake of catecholamines involves the dopamine transporter (DAT) at dopaminergic neurons and the norepinephrine transporter (NET) at noradrenergic neurons. Extraneuronal uptake of catecholamines is mediated by organic cation transporters (OCTs), including the classic corticosterone-sensitive extraneuronal monoamine transporter. Catecholamine transporters function as part of uptake and metabolizing systems primarily responsible for inactivation of transmitter released by neurons. Additionally, the neuronal catecholamine transporters, recycle catecholamines for rerelease, thereby reducing requirements for transmitter synthesis. In a broader sense, catecholamine transporters function as part of integrated systems where catecholamine synthesis, release, uptake, and metabolism are regulated in a coordinated fashion in response to the demands placed on the system. Location is also important to function. Neuronal transporters are essential for rapid termination of the signal in neuronal-effector organ transmission, whereas non-neuronal transporters are more important for limiting the spread of the signal and for clearance of catecholamines from the bloodstream. Besides their presynaptic locations, NET and DAT are also present at several extraneuronal locations, including syncytiotrophoblasts of the placenta and endothelial cells of the lung (NET), stomach and pancreas (DAT). The extraneuronal monoamine transporter shows a broad tissue distribution, whereas the other two non-neuronal catecholamine transporters (OCT1 and OCT2) are mainly localized to the liver, kidney, and intestine. Altered function of peripheral catecholamine transporters may be involved in disturbances of the autonomic nervous system, such as occurs in congestive heart failure and hypernoradrenergic hypertension. Peripheral catecholamine transporters provide important targets for clinical imaging of sympathetic nerves and diagnostic localization and treatment of neuroendocrine tumors, such as neuroblastomas and pheochromocytomas.

Impaired cardiac adrenergic innervation assessed by MIBG imaging as a predictor of treatment response in childhood dilated cardiomyopathy

OBJECTIVE

To evaluate the prognostic value of metaiodobenzylguanidine (MIBG) imaging in childhood cardiomyopathy.

DESIGN

Prospective cohort study.

SETTING

Tertiary referral centre.

PATIENTS

40 children (21 boys, 19 girls; mean (SD) age, 7.0 (5.6) years) with heart failure resulting from idiopathic dilated cardiomyopathy (n = 23) or various other disorders (n = 17).

METHODS

At the initial examination, cardiac (123)I-MIBG uptake and release, circulating noradrenaline (norepinephrine) concentration, x ray cardiothoracic ratio, and echocardiographic variables were recorded. Cardiac MIBG uptake was obtained by measuring the heart to mediastinum activity ratio on the planar image obtained four hours after MIBG injection. MIBG washout rate was evaluated using relative decrease in cardiac activity measured at 20 minutes and four hours. Patients were treated with angiotensin converting enzyme inhibitors, diuretics, and digitalis, and were followed up for 12 (10) months. Fifteen patients did not respond to medical treatment (12 heart transplants; three deaths), and 25 did respond (improved or stable).

RESULTS

Cardiac MIBG uptake was positively correlated with x ray cardiothoracic index (r = 0.55, p = 0.0008) and echocardiographic left ventricular fractional shortening (r = 0.68, p < 0.0001). Among all the clinical and laboratory variables tested, multivariate discriminant analysis showed that the only independent predictor of an unfavourable outcome was a low MIBG uptake (p < 0.001). Survival curves had a mean threshold value of 1.54 for MIBG uptake.

CONCLUSIONS

Impaired cardiac adrenergic innervation is strongly related to adverse outcome in children with dilated cardiomyopathy, independently of the aetiology. MIBG imaging may help to stratify risk in such patients.

Prognostic value of iodine-123-metaiodobenzylguanidine imaging and cardiac natriuretic peptide levels in patients with left ventricular dysfunction resulting from cardiomyopathy

This study assessed the prognostic value of Iodine-123-metaiodobenzylguanidine (MIBG) imaging and of the plasma level of cardiac natriuretic peptides in patients with left ventricular dysfunction resulting from cardiomyopathy. Predictors of cardiac death or hospitalization related to progressive heart failure were examined in 171 patients with chronic heart failure (96 patients with idiopathic cardiomyopathy and 75 patients with ischemic cardiomyopathy). All patients underwent MIBG imaging at rest and other hemodynamic studies. During a mean (+/-SD) follow-up period of 27+/-11 months, 11 patients died from heart failure and 16 required hospitalization. High MIBG washout was an independent predictor of cardiac death (relative risk [RR] = 1.158, p<0.0001) whereas the plasma level of brain natriuretic peptide (BNP: relative risk [RR] = 1.005, p<0.0001) and high MIBG washout (relative risk [RR] = 1.094, p<0.0001) were predictors of progressive heart failure (ie, combined cardiac death and hospitalization). Accelerated myocardial adrenergic nerve activity as assessed by MIBG imaging and the plasma levels of BNP are powerful predictors of the patient's prognosis.

Improvement in left ventricular function in response to carvedilol is accompanied by attenuation of neurohumoral activation in patients with dilated cardiomyopathy

BACKGROUND

We sought to evaluate whether improvement in ejection fraction (EF) with carvedilol therapy is accompanied by improvement in neurohumoral factors.

METHODS AND RESULTS

Forty-two patients with dilated cardiomyopathy were given carvedilol for 3 to 5 months. Changes in EF, plasma atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and norepinephrine levels were determined. Iodine-123 metaiodobenzylguanidine (MIBG) images were also obtained before and after carvedilol therapy. Myocardial uptake of MIBG was calculated as the heart to mediastinal activity ratio (H/M). Storage and release of MIBG was calculated as percent myocardial MIBG washout rate (WR). We divided patients into 2 groups: 27 responders whose EF increased by more than 5% and 15 nonresponders whose EF increased by 5% or less. EF of responders increased by 15 +/- 5% and that of nonresponders by 1 +/- 4%. Although MIBG image-derived indexes of nonresponders remained unchanged, the delayed H/M (1.91 +/- 0.34 v 2.24 +/- 0.53, P < .01) and WR (49 +/- 11 v 39 +/- 9%, P < .01) of responders improved, respectively. The plasma ANP (51 +/- 50 v 27 +/- 24 pg/mL, P < .01) and BNP (194 +/- 197 v 49 +/- 62 pg/mL, P < .01) levels of responders decreased. The degree of changes in the plasma BNP level correlated with changes in EF (r = -.698, P < .01).

CONCLUSION

The improvement in EF with carvedilol therapy was proved to be accompanied by an improvement in neurohumoral factors.