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I-123-MIBG cardiac uptake imaging, in familial dilated cardiomyopathy
Elisabete Martins1, Teresa Faria, J Silva-Cardoso
1Faculdade de Medicina do Porto, Serviço de Cardiologia, Hospital de São João, Porto, Portugal. elisabetemartins09@gmail.com
Insights
I-123-metaiodobenzylguanidine (123I-MIBG) cardiac imaging may identify familial dilated cardiomyopathy (DCM) in patients with abnormal heart adrenergic activity. This imaging technique shows promise for evaluating DCM families, even in those with normal echocardiograms.
Area of Science:
- Cardiology
- Nuclear Medicine
- Genetics
Background:
- Myocardial adrenergic activity is significant in heart failure.
- Familial dilated cardiomyopathy (DCM) evaluation lacks specific imaging for adrenergic function.
- I-123-metaiodobenzylguanidine (123I-MIBG) cardiac uptake imaging assesses adrenergic activity.
Purpose of the Study:
- To evaluate cardiac adrenergic activity using 123I-MIBG imaging in a genotyped family with DCM.
- To determine if 123I-MIBG imaging can detect adrenergic abnormalities in DCM carriers.
Main Methods:
- 123I-MIBG cardiac imaging was performed on 11 family members.
- Measurements included heart/mediastinal (H/M) ratio and myocardial washout (MW) rate.
- Visual scoring of 123I-MIBG uptake was used to assess segmental adrenergic activity.
Main Results:
- Patients with DCM and left ventricular enlargement (LVE) showed higher MW rates and lower H/M ratios than controls.
- Abnormal 123I-MIBG scintigrams were observed in DCM and LVE patients.
- One carrier with a normal echocardiogram also had an abnormal 123I-MIBG scan.
Conclusions:
- 123I-MIBG imaging may reveal cardiac adrenergic hyperactivity in DCM patients and gene carriers.
- The method shows potential for evaluating familial DCM, including in individuals with normal echocardiograms.
- Further studies with larger cohorts are needed to confirm these findings.
Unlabelled:
The pathological significance of myocardial adrenergic activity in patients with heart failure is well documented. No previous study has assessed the usefulness of I123-metaiodobenzylguanidine (123I-MIBG) cardiac uptake imaging for the evaluation of familial dilated cardiomyopathy (DCM).
Objective:
To evaluate cardiac adrenergic activity, using 123I-MIBG cardiac uptake imaging, in members of a genotyped family with DCM.
Methods:
Clinical evaluation, 12-lead ECG, 2D echocardiogram, heart rate variability analysis by 24h Holter, plasma B-type natriuretic peptide (BNP) measurements and 123I-MIBG cardiac imaging were performed in all participants. Anterior projection planar images and single photon emission computed tomographies of the thorax were obtained 20 min and 4 hours after the intravenous administration of 370 MBq of 123I-MIBG (early and late images). Heart/mediastinal (H/M) ratio and myocardial washout (MW) rate were obtained based on the anterior planar images. In polar maps, segmental uptake of 123I-MIBG was evaluated using a 4-grade visual score: grade 1 - uptake > 75% of maximum myocardial uptake (MMU); grade 2 - uptake 51-75% of MMU; grade 3 - uptake 26-50% of MMU; grade 4 - uptake < or = 25% of MMU.
Results:
Eleven adults were included: 4 with DCM, 4 with isolated left ventricular enlargement (LVE), and 3 with normal echocardiogram. Patients with DCM and LVE presented higher MW rates, lower H/M ratios and higher visual score grades than those with normal 2D echocardiograms. One patient with a normal echocardiogram but carrying the disease locus also presented an abnormal MIBG cardiac scintigram.
Conclusion:
Patients with the phenotypic expression of the disease (DCM and LVE) and even carriers of the DCM gene with normal echocardiograms may present an abnormal MIBG cardiac scintigram, probably reflecting cardiac adrenergic hyperactivity. If confirmed in larger numbers, this method may be useful for the evaluation of DCM families.
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