Abstract 14818: Hyperactivity of Cardiac Sympathetic Nerve in the Remote Normal Region in Patients with a Prior Myocardial Infarction with Left Ventricular Remodeling
Left ventricular (LV) remodeling is observed in the remote normal region in the left ventricles after myocardial infarction (MI) and is closely involved in systolic heart failure. β-blocker administration improves the prognosis of patients with an MI. Accordingly, we assessed the mechanism of these issues from the viewpoint of cardiac sympathetic nerve function in such a region in 16 patients with a prior myocardial infarction using positron emission tomography (PET) and radiolabelled catecholamine analogue C11-hydroxyephedrine (HED) as a marker for neuronal catecholamine uptake function. HED retention index was determined by normalizing myocardial tracer activity from 30 to 40 minutes to the integral of the C11 activity input function. Cardiac presynaptic catecholamine uptake is known to depend on myocardial blood flow (MBF). Thus, we quantitatively measured regional MBF using PET with N13-ammonia on the same day. LV volumes were also determined using echocardiography. This study protocol was also performed in 10 healthy volunteers served as normal controls.
Results: LV end-diastolic volume index was significantly larger in patients with a prior MI than in normal controls (69.6±15.9 vs 47.2±13.4 ml/m2 p<0.01). Apparent LV remodeling was observed in patients with a prior MI. In normal controls, MBF and HED retention index were largest in the LV anterior wall. MBF was significantly less in the remote normal region in patients with a prior MI compared with that in the anterior wall in normal controls (0.76±0.14 vs 0.88±0.13 ml/g/min, p<0.05). The retention index of HED (8.06±1.22 vs 7.03±1.12%/min, p<0.01) and the retention index corrected by the MBF in the corresponding area (10.8±1.7 vs 8.1±0.9%/min/MBF, p<0.001) were significantly higher in the remote normal region than in the anterior wall of normal controls.
Conclusion: A greater amount of sympathetic presynaptic catecholamine uptake is observed in the remote normal region in patients with a prior MI. This finding suggests that hyperactivity of myocardial sympathetic nerve in the remote normal region of patients with a prior MI and LV remodeling is related to the pathophysiology of systolic heart failure after MI.
- © 2011 by American Heart Association, Inc.