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Abstract
Background and Objectives
Ventricular arrhythmia is an important cause of death in patients suffering with idiopathic dilated cardiomyopathy (IDCM). The decreased uptake or increased "washout" of 123I-metaiodobenzylguanidine (MIBG)-derived radioactivity is associated with a worse prognosis or severe disease in patients with cardiac diseases.
Subjects and Methods
Forty patients (28 men, mean age: 56.5±13.0 years) with angiographically proven IDCM were studied and divided into 2 groups: the patients with clinically documented ventricular tachycardia (VT) and IDCM (group A; 17 patients), and the patients without VT, but with IDCM (group B; 23 patients). The normal control group (7 men, mean age 62.4±7.9) was compared theses patients. 123I-MIBG was evaluated by the early (15 min) and delayed (3hours) uptake, the heart to mediastinum uptake (H/M) ratio and the global and regional washout ratio (WOR) that was defined as the [early H uptake-delayed H uptake]/early H uptake. The clinical variables, echocardiographic parameters and 123I-MIBG-derived parameters were compared among three groups.
Results
There were no significant differences in age and the echocardiographic parameters between the groups A and B. A significant negative correlation was present between the early inferior wall H/M ratio and the LVEDD (Spearman's correlation, r=-0.412, p=0.08), and the early inferior H/M ratio and the LVESD (Spearman's correlation, r=-0.463, p=0.03). Only the delayed lateral wall uptake was significantly lower in group A than that in group B (23.3±5.3 versus 27.8±8.4, respectively p=0.042). The regional WOR was not statically different among the three groups.
Figures and Tables
Fig. 1
Correlation between left ventricular (LV) function and early inferior wall H/M ratio. There was positive correlation between early inferior wall H/M ratio and LV ejection fraction (EF), and negative correlation is shown between LV end-diastolic dimension (LVEDD), LV end-systolic dimension (LVESD) and early inferior wall H/M ratio. VT: ventricular tachycardia, H/M: heart to mediastinum uptake.
Fig. 2
Difference of 123I- Metaiodobenzylguanidine (123I-MIBG) finding in a control patient and a patient with idiopathic dilated cardiomyopathy (IDCM). Compared with early and delayed 123I-MIBG uptake in control (2.04 and 2.34 respectively), idiopathic dilated cardiomyopathy (IDCM) patient showed diminished early and delayed 123I-MIBG uptake (1.50 and 1.31 respectively), and an increase of washout rate (arrowhead) (0.13 vs 0.41 respectively).
Fig. 3
Example of mismatch between 123I-metaiodobenzylguanidine (123I-MIBG) and 99mTc-methoxy isobutyl isonitrile (99mTc-MIBI) single photon emission computed tomography (SPECT). Compared with the 99mTc-MIBI, 123I-MIBG SPECT shows more extensive uptake defect in inferior and lateral wall especially in delayed image (arrowhead). That means sympathetic denervation is more severe or extensive than the degree of myocardial dysfunction.
Table 1
Clinical characteristics of the study patients
Values are mean±SD. *p<0.05, between control and IDCM VT (+), †p<0.05, between control and IDCM VT (-), ‡p<0.05, between IDCM VT (+) and IDCM VT (-), §p<0.05, among three groups. IDCM: idiopathic dilated cardiomyopathy, LVEF: left ventricular ejection fraction, EF: ejection fraction, LVEDD: left ventricular enddiastolic dimension, LVESD: LV end-systolic dimension, ACEI: angiotensin converting enzyme inhibitor, ARB: angiotensin converting enzyme receptor blocker, VT: ventricular tachycardia, HR: heart rate, SBP: systolic blood pressure, DBP: diastolic blood pressure, SD: standard deviations
Table 2
Global and regional 123I-MIBG uptake at early and delayed phase according to the presence of VT
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