Prognostic value of cardiac sympathetic nerve activity evaluated by [123I]m-iodobenzylguanidine imaging in patients with ST-segment elevation myocardial infarction

Effects of mineralocorticoid receptor antagonist eplerenone on cardiac sympathetic nerve activity and left ventricular remodeling after reperfusion therapy in patients with first ST-segment elevation myocardial infarction

PURPOSE

The activation of the renin-angiotensin-aldosterone system prevents the uptake of norepinephrine and promotes structural remodeling of the heart. The mineralocorticoid receptor antagonist (MRA) eplerenone prevents left ventricular (LV) remodeling in patients with acute myocardial infarction, but its influence on cardiac sympathetic nerve activity (CSNA) has not been determined.

METHODS

We retrospectively evaluated the first ST-segment elevation myocardial infarction (STEMI) patients in our database who underwent 123I-metaiodobenzylguanidine (MIBG) scintigraphy 3 weeks after admission. Eighty-four STEMI patients after primary coronary angioplasty were selected, and used propensity score matching to compare patients who treated with MRA (N = 42), and those who did not (N = 42). The LV end-diastolic volume, end-systolic volume, and ejection fraction were determined by echocardiography, and plasma procollagen type III amino terminal peptide (PIIINP) was measured before and 3 weeks after treatment. The delayed total defect score (TDS), delayed heart/mediastinum count (H/M) ratio, and washout rate (WR) were determined using 123I-MIBG scintigraphy after 3 weeks.

RESULTS

Following primary angioplasty, age, gender, risk factors, culprit coronary artery, peak serum creatine phosphokinase concentration, and recanalization time were similar in the two groups. However, the MRA group showed significantly lower TDS and WR values (TDS: 22.8 ± 8.1 vs 32.2 ± 11.5, P < 0.005; WR: 31.1 ± 9.0% vs 42.7 ± 9.9%, P < 0.001) and a significantly higher H/M ratio (2.23 ± 0.41 vs 2.03 ± 0.36, P < 0.05) than the non-MRA group. The degree of change in LV parameters, and PIIINP were more favorable in the MRA group than in the non-MRA group. Moreover, multiple linear regression analyses revealed that both WR and not MRA treatment were significant predictor for LV remodeling, along with PIIINP concentrations.

CONCLUSION

Administration of eplerenone improves CSNA and prevents LV remodeling in patients with a first STEMI.

Assessment of therapeutic effects of statin on cardiac sympathetic nerve activity after reperfusion therapy in patients with first ST-segment elevation myocardial infarction and normal low-density lipoprotein cholesterol

BACKGROUND

Statin treatment reduces enhanced cardiac sympathetic nerve activity (CSNA) in patients with heart disease, and reduces adverse cardiac events in patients with coronary artery disease.

METHODS

We retrospectively evaluated the first ST-segment elevation myocardial infarction (STEMI) patients and low-density lipoprotein cholesterol < 120 mg/dL in our database who underwent 123I-metaiodobenzylguanidine (MIBG) scintigraphy 3 weeks after admission. Sixty STEMI patients after primary coronary angioplasty were selected, and used propensity score matching to compare patients treated with strong statin (n = 30), and those who did not (n = 30). Moreover, echocardiographic left ventricular (LV) parameters were determined, and plasma procollagen type III amino terminal peptide (PIIINP) was also measured before and 3 weeks after treatment.

RESULTS

Following primary angioplasty, age, gender, risk factors, culprit coronary artery, peak serum creatine phosphokinase concentration, and recanalization time were similar in the two groups. However, the statin group showed significantly lower delayed total defect score and washout rate evaluated by 123I-MIBG scintigraphy (22.4 ± 8.1 vs. 29.6 ± 10.5; P < 0.01, and 30.4 ± 8.9% vs. 40.1 ± 11.4%; P < 0.005, respectively) and higher delayed heart/mediastinum count ratio (2.17 ± 0.38 vs. 1.96 ± 0.30, P < 0.05) compared with the non-statin group. Moreover, the degree of change in LV parameters and PIIINP was more favorable in the statin group than in the non-statin group.

CONCLUSIONS

Administration of statin improves CSNA after reperfusion therapy in patients with first STEMI.

Feasibility of myocardial PET imaging using a benzylguanidine analog: meta-(3-[18F]fluoropropyl)benzylguanidine ([18F]mFPBG)

INTRODUCTION

Global and regional sympathetic activity in the heart can be evaluated using [¹²³I]meta-iodobenzylguanidine ([¹²³I]mIBG) imaging. However, [¹²³I]mIBG is associated with low image spatial resolution and sensitivity in cardiac imaging. We investigated the capability of an F-18-labeled mIBG derivative, meta-(3-[¹⁸F]fluoropropyl)benzylguanidine ([¹⁸F]mFPBG), for identifying ischemic and viable myocardium in a rat model of myocardial infarction.

MATERIALS AND METHODS

The ex vivo biodistribution and in vivo metabolic stability of [¹⁸F]mFPBG were investigated in Sprague-Dawley rats. Selective cardiac adrenergic activation was confirmed via a blocking experiment involving pretreatment with desipramine (2 mg kg^-1), followed by the administration of [¹⁸F]mFPBG. Imaging properties of [¹⁸F]mFPBG were compared with those of traditional cardiac imaging radiotracers ([¹²³I]mIBG and [^99mTc]MIBI) in a rat model of myocardial infarction. Non-invasive image-based measurements of infarct sizes were then compared with histological findings by using Bland-Altman analysis.

RESULTS

The differences in infarct sizes determined using histological analysis and [¹⁸F]mFPBG PET were -2.55 ± 4.99% (range: -12.33 to 7.22), -2.35 ± 3.32% (range: -8.87 to 4.16), and -3.15 ± 6.16% (range: -15.24 to 8.93) at 5, 20, and 40 min, respectively. Furthermore, [¹⁸F]mFPBG PET was superior to traditional imaging methods in assessing the degree of ischemia in areas of myocardial infarction, as well as the actual infarct size.

CONCLUSION

Compared to [¹²³I]mIBG, [¹⁸F]mFPBG showed improved spatial resolution and sensitivity in a rat model of myocardial infarction. This result suggested that [¹⁸F]mFPBG is a promising cardiac PET imaging agent for potential diagnostic application in PET cardiology.

Area at risk can be assessed by iodine-123-meta-iodobenzylguanidine single-photon emission computed tomography after myocardial infarction: a prospective study

BACKGROUND

Myocardial salvage is an important surrogate endpoint to estimate the impact of treatments in patients with ST-segment elevation myocardial infarction (STEMI).

AIM

The aim of this study was to evaluate the correlation between cardiac sympathetic denervation area assessed by single-photon emission computed tomography (SPECT) using iodine-123-meta-iodobenzylguanidine (I-MIBG) and myocardial area at risk (AAR) assessed by cardiac magnetic resonance (CMR) (gold standard).

PATIENTS AND METHODS

A total of 35 postprimary reperfusion STEMI patients were enrolled prospectively to undergo SPECT using I-MIBG (evaluates cardiac sympathetic denervation) and thallium-201 (evaluates myocardial necrosis), and to undergo CMR imaging using T2-weighted spin-echo turbo inversion recovery for AAR and postgadolinium T1-weighted phase sensitive inversion recovery for scar assessment.

RESULTS

I-MIBG imaging showed a wider denervated area (51.1±16.0% of left ventricular area) in comparison with the necrosis area on thallium-201 imaging (16.1±14.4% of left ventricular area, P<0.0001). CMR and SPECT provided similar evaluation of the transmural necrosis (P=0.10) with a good correlation (R=0.86, P<0.0001). AAR on CMR was not different compared with the denervated area (P=0.23) and was adequately correlated (R=0.56, P=0.0002). Myocardial salvage evaluated by SPECT imaging (mismatch denervated but viable myocardium) was significantly higher than by CMR (P=0.02).

CONCLUSION

In patients with STEMI, I-MIBG SPECT, assessing cardiac sympathetic denervation may precisely evaluate the AAR, providing an alternative to CMR for AAR assessment.

Ganglionic GFAP + glial Gq-GPCR signaling enhances heart functions in vivo

The sympathetic nervous system (SNS) accelerates heart rate, increases cardiac contractility, and constricts resistance vessels. The activity of SNS efferent nerves is generated by a complex neural network containing neurons and glia. Gq G protein-coupled receptor (Gq-GPCR) signaling in glial fibrillary acidic protein-expressing (GFAP⁺) glia in the central nervous system supports neuronal function and regulates neuronal activity. It is unclear how Gq-GPCR signaling in GFAP⁺ glia affects the activity of sympathetic neurons or contributes to SNS-regulated cardiovascular functions. In this study, we investigated whether Gq-GPCR activation in GFAP⁺ glia modulates the regulatory effect of the SNS on the heart; transgenic mice expressing Gq-coupled DREADD (designer receptors exclusively activated by designer drugs) (hM3Dq) selectively in GFAP⁺ glia were used to address this question in vivo. We found that acute Gq-GPCR activation in peripheral GFAP⁺ glia significantly accelerated heart rate and increased left ventricle contraction. Pharmacological experiments suggest that the glial-induced cardiac changes were due to Gq-GPCR activation in satellite glial cells within the sympathetic ganglion; this activation led to increased norepinephrine (NE) release and beta-1 adrenergic receptor activation within the heart. Chronic glial Gq-GPCR activation led to hypotension in female Gfap-hM3Dq mice. This study provides direct evidence that Gq-GPCR activation in peripheral GFAP⁺ glia regulates cardiovascular functions in vivo.

Comparative effects of long-acting and short-acting loop diuretics on cardiac sympathetic nerve activity in patients with chronic heart failure

Objective

Short-acting loop diuretics are known to enhance cardiac sympathetic nerve activity (CSNA) in patients with chronic heart failure (CHF). The effects of two loop diuretics—long-acting azosemide and short-acting furosemide—on CSNA were evaluated using ¹²³I-metaiodobenzylguanidine (MIBG) scintigraphy in patients with CHF.

Methods

The present study was a subanalysis of our previously published study, which had reported that serial ¹²³I-MIBG studies were the most useful prognostic indicator in patients with CHF. Patients with CHF (n=208, left ventricular ejection fraction <45%) but no history of cardiac events for at least 5 months prior to the study were identified according to their histories of acute decompensated heart failure requiring hospitalisation. Patients underwent ¹²³I-MIBG scintigraphy immediately before hospital discharge and at a 6-month follow-up. The delayed % denervation, delayed heart/mediastinum count (H/M) ratio and washout rate (WR) were determined using ¹²³I-MIBG scintigraphy. A total of 108 patients were selected, and propensity score matching was used to compare patients treated with either oral azosemide (n=54) or furosemide (n=54).

Results

After treatment, ¹²³I-MIBG scintigraphic parameters improved in both groups. However, the degree of change in % denervation was −13.8±10.5 in the azosemide group and −5.7±12.7 in the furosemide group (p<0.01), the change in H/M ratio was 0.20±0.16 in the azosemide group and 0.06±0.19 in the furosemide group (p<0.01), and the change in WR was −11.3±9.2% in the azosemide group and −3.0±12.7% in the furosemide group (p<0.01). Moreover, multivariate analysis showed an independent and significant positive relationship between furosemide and δ-WR from hospital discharge to 6 months after treatment in patients with CHF (p=0.001).

Conclusions

These findings indicate that azosemide suppresses CSNA compared with furosemide in patients with CHF.

Trial registration number

UMIN000000626 (UMIN-CTR Clinical Trial).

Prognostic Significance of Neuroadrenergic Dysfunction for Cardiovascular Events in Patients With Acute Myocardial Infarction

BACKGROUND

The dysregulation of systemic blood pressure (BP) variation or cardiac neuroadrenergic dysfunction is associated with adverse cardiovascular events. We aimed to clarify the prognostic significance of neuroadrenergic dysfunction for cardiovascular events in patients with acute myocardial infarction (AMI).

METHODS AND RESULTS

We enrolled 63 AMI patients (mean age, 67±12 years) underwent ambulatory BP monitoring (ABPM) and cardiac iodine-(123)metaiodobenzylguanidine (MIBG) imaging within 4 weeks after AMI onset. We analyzed the circadian BP pattern and heart-to-mediastinum (H/M) MIBG uptake ratio. All the patients were followed for 2 years. The study endpoint was a composite of major adverse cardiovascular events, including all-cause death, MI, coronary revascularization except for the MI culprit lesion, and stroke. Patients with a non-dipper pattern (n=29) or an H/M ratio <1.96 (n=28) had a worse prognosis than those with either a dipper pattern (n=34) or an H/M ratio ≥1.96 (n=35; log-rank, P=0.013 and 0.010, respectively). Patients with both a non-dipper pattern and an H/M ratio <1.96 (n=12) had a significantly worse prognosis than did the other patients (P=0.0020).

CONCLUSIONS

Dysregulation of BP variation and cardiac MIBG uptake were associated with cardiovascular events following AMI. Examining ABPM with MIBG imaging may potentially improve risk stratification in these patients.

Selective improvement in Seattle Heart Failure Model risk stratification using iodine-123 meta-iodobenzylguanidine imaging

BACKGROUND

The Seattle Heart Failure Model (SHFM) is a multivariable model that uses demographic and clinical markers to predict survival in patients with heart failure. Inappropriate activation of the sympathetic nervous system, which contributes to the progression of heart failure and increased mortality, can be assessed using iodine-123 meta-iodobenzylguanidine (MIBG) cardiac imaging. This study investigated the incremental value of MIBG cardiac imaging when added to the SHFM for prediction of all-cause mortality.

METHODS

Survival data from 961 NYHA II-III subjects in the ADMIRE-HFX trial were included in this analysis. The predictive value of the SHFM alone and in combination with MIBG heart-to-mediastinum ratio (H/M) was compared for all-cause mortality (101 deaths during a median follow-up of 2 years).

RESULTS

The addition of H/M to the SHFM in a Cox model significantly improved risk prediction (P < .0001), with a greater utility in higher risk SHFM patients. The observed 2-year mortality in the highest-risk SHFM subjects (rounded SHFM score of 1) was 24%, but varied from 46% with H/M <1.2 to 0% with H/M >1.8. Net reclassification improvement was 22.7% (P < .001), with 14.9% of subjects who died reclassified into a higher risk category than suggested by SHFM score alone (P = .01) and 7.9% of subjects who survived reclassified into a lower risk category (P < .0001). The 2-year integrated discrimination improvement (+4.14%, P < .0001) and the 1-year area under the receiver-operator characteristic curve (+0.04, P = .026) both showed significant improvement for the combined model with H/M compared to the SHFM alone.

CONCLUSION

The addition of MIBG imaging to the SHFM improves risk stratification, especially in higher risk patients. MIBG may have clinical utility in higher risk patients who are being considered for devices such as ICD, CRT-D, LVAD, and cardiac transplantation.