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Cardiac adrenergic innervation within the first 3 months after acute myocardial infarction
Insights
Cardiac adrenergic re-innervation after myocardial infarction is a slow process. This study found no evidence of nerve regrowth in the first three months post-infarction, despite improved heart muscle blood flow.
Area of Science:
- Cardiology
- Nuclear Medicine
- Physiology
Background:
- Myocardial infarction (MI) causes adrenergic denervation.
- Cardiac adrenergic re-innervation post-MI is poorly understood.
- Understanding re-innervation is crucial for recovery after heart attack.
Purpose of the Study:
- To investigate cardiac adrenergic innervation and myocardial perfusion changes in early convalescence after acute MI.
- To determine the extent and time scale of adrenergic re-innervation within 3 months post-MI.
Main Methods:
- 15 men underwent imaging 1 week and 3 months after acute MI.
- Single-photon emission computed tomographic imaging used I123-metaiodobentzylguanidine (MIBG) for adrenergic nerves and Tc99m-sestamibi (MIBI) for perfusion.
- Defect size defined as regional uptake <=30% of maximal myocardial activity.
Main Results:
- The size of the MIBG defect (adrenergic denervation) remained unchanged (approx. 30-31%) between 1 week and 3 months post-MI.
- MIBG activity in infarct and peri-infarct zones showed no significant change.
- The size of the MIBI defect (impaired perfusion) significantly decreased, indicating improved myocardial perfusion.
Conclusions:
- Cardiac adrenergic re-innervation is a slow process.
- No evidence of adrenergic re-innervation was found in the first 3 months after acute MI.
- Improved myocardial perfusion does not correlate with early adrenergic re-innervation.
Abstract:
It is widely accepted that myocardial infarction results in adrenergic denervation of the infarcted and peri-infarcted myocardium. On the contrary, the concept of re-innervation of adrenergic nerve fibres is less well established. Although there is evidence of partial re-innervation occuring several months after myocardial infarction, the extent and time scale of re-innervation are only poorly known. In this study we investigated changes in cardiac adrenergic innervation and myocardial perfusion during the early convalescence period (the first 3 months) after an acute myocardial infarction. Single-photon emission computed tomographic imaging was conducted in 15 men 1 week and 3 months after an acute myocardial infarction with I123-metaiodobentzylguanidine (MIBG) and Tc99m-sestamibi (MIBI) to determine the extent of adrenergic denervation and impaired perfusion, respectively. A MIBG and MIBI defect was determined as regional uptake