Cardiac sympathetic dysfunction contributes to left ventricular remodelling after acute myocardial infarction

Abstract

To investigate the role of the cardiac sympathetic nervous system in left ventricular remodelling, 50 patients with first-time acute myocardial infarction (AMI) and patency of the infarct-related artery after reperfusion underwent quantitative iodine-123 metaiodobenzylguanidine (MIBG) imaging at 4 days and 4 weeks (n=42), and quantitative technetium-99m tetrofosmin imaging at 2 days after AMI. They also underwent both ventriculography and coronary angiography on admission and about 4 weeks after AMI. On the basis of left ventricular end-systolic volume (LVESV), patients were divided into two groups. Patients with LVESV dilatation (n=20) had a significantly lower ejection fraction (P<0.003) and a significantly higher severity score of 99mTc-tetrofosmin (P<0.04), and total severity (P<0.01), delta extent (P<0.007) and delta severity (P<0.0008) scores of MIBG than patients without LVESV dilatation (n=30). delta severity score of MIBG was directly correlated with change in LVESV at 4 weeks (r=0.63, P<0.0001). Stepwise linear discriminant function analysis showed that delta severity score of MIBG (P<0.0002) was the only discriminator of LVESV dilatation. Patients with LVESV dilatation had higher regional washout rates in both the infarct and the non-infarct zones than patients without such dilatation. Furthermore, no MIBG parameters changed significantly between 4 days and 4 weeks after AMI. In reperfused AMI, delta severity score of MIBG was related to the degree of ventricular dilatation and was the only powerful discriminator of ventricular dilatation. These results suggest that cardiac sympathetic nervous abnormality might contribute to left ventricular remodelling in reperfused AMI. MIBG imaging may allow identification of reperfused AMI patients at high risk for left ventricular remodelling.

Multiparametric Molecular Imaging Provides Mechanistic Insights into Sympathetic Innervation Impairment in the Viable Infarct Border Zone

“…Our study confirms prior experimental and clinical work, which showed impaired sympathetic innervation in the viable infarct border zone that has electrophysiologic implications and contributes to ventricular arrhythmia (3,7,13). Integrated analysis of PET and MR imaging also shows that an innervation/perfusion mismatch after myocardial infarction is associated with altered regional contractility and wall strain despite preserved perfusion and viability.…”

“…High sensitivity of nerve terminals to ischemic damage leads to impaired innervation in the infarct region but also in the viable border zone (4). A detailed understanding of the pathophysiology of poorly innervated but viable myocardium is important, because it may precede arrhythmia or contractile failure and hence may be useful for guidance of preventive therapy (5)(6)(7).…”

Brain Natriuretic Peptide (BNP) Level is Closely Related to the Extent of Left Ventricular Sympathetic Overactivity in Chronic Ischemic Heart Failure

“…In vivo, sympathetic nervous stimulation can induce BNP gene expression (11). In addition, angiotensin II, which can activate the sympathetic nervous system, also induced BNP gene expression in human atrial muscle preparations (25) (1)(2)(3)(4), hypertensive myocardial hypertrophy (13), or acute coronary syndrome (16), which have been shown to have enhanced cardiac sympathetic activity. In contrast, intravenous infusion of BNP was shown to have a sympathoinhibitory effect in both normal subjects and heart failure patients (7).…”

“…Therefore, it is expected that BNP can provide an easy method for the early detection of heart failure and for assessing the severity of heart failure and the effectiveness of treatment. Recently, it has been shown that BNP release can be induced by sympathetic nervous activation (11) (2,3,(12)(13)(14)(15)(16)(17)(18). Using MIBG imaging, it is easy to assess regional efferent sympathetic neuronal function in the human left ventricle of patients suffering from various heart diseases (16)(17)(18).…”

Cardiac autonomic imaging with SPECT tracers

“…123 I-mIBG imaging can also shed light on the effect of sympathetic alteration on post-MI LV remodeling. Sakata et al 146 found that after a first MI, despite a patent infarct coronary artery, the presence of a high severity score correlated with LV end-systolic volume dilatation.…”