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The Open Artery: Electrophysiologic Considerations
1Cardiac Arrhythmia Service, New England Medical Center, Boston, Massachusetts, USA.
Insights
Restoring blood flow in the infarct-related artery after heart attack improves outcomes by reducing dangerous arrhythmias. A patent artery positively impacts electrophysiologic risk factors, suggesting a key role beyond just preserving heart muscle.
Area of Science:
- Cardiology
- Electrophysiology
- Medical Research
Background:
- Prompt opening of the infarct-related artery (IRA) after myocardial infarction (MI) reduces mortality.
- Benefits of IRA recanalization may extend beyond myocardial preservation.
- A patent IRA might favorably modify the post-MI electrophysiologic environment.
Purpose of the Study:
- To review evidence supporting the hypothesis that a patent IRA favorably modifies the post-MI electrophysiologic milieu.
- To investigate the impact of IRA patency on electrophysiologic risk stratification parameters.
Main Methods:
- Review of long-term follow-up data from controlled trials.
- Analysis of studies examining signal-averaged electrocardiogram (SAECG), heart-rate variability (HRV), programmed electrical stimulation (PES), and QT interval dispersion (QTd).
Main Results:
- A patent IRA is associated with reduced incidence of life-threatening ventricular arrhythmias and sudden cardiac death.
- Many studies report a reduction in late potentials on SAECG with IRA patency.
- Improved heart-rate variability and reduced QT interval dispersion are linked to IRA patency.
- High-risk patients show lower inducibility during PES and better response to therapy with a patent IRA.
Conclusions:
- A patent infarct-related artery appears to favorably modulate the post-MI electrophysiologic substrate.
- This modulation may contribute to improved outcomes beyond myocardial salvage.
- Further long-term studies are needed to conclusively demonstrate the benefits.
Abstract:
Prompt opening of the infarct-related artery reduces mortality and subsequent morbid events. Not all benefit of timely thrombolysis or angioplasty appears to be accounted for by myocardial preservation. A favorable modification of the electrophysiologic postinfarction milieu by a patent infarct-related artery has been proposed to help explain this improved outcome. This review investigates the support for such a hypothesis. Long-term follow-up data from controlled trials is scarce but suggests that episodes of life-threatening ventricular arrhythmias and sudden cardiac death are less frequent after thrombolysis with a patent infarct-related artery. The preponderance of data investigate the modification of postinfarction risk stratification parameters, including the signal-averaged electrocardiogram, assessment of heart-rate variability, response to programmed extrastimuli, and dispersion of refractoriness. Reduction of the incidence of late potentials after thrombolysis has been reported by many, but not all, investigators. Differences in signal-averaging technique and timing may help explain the disparity of findings. A patent infarct-related artery is associated with a reduction in late potential incidence. Heart-rate variability, a measure of autonomic balance, appears to be improved in those high-risk patients who receive thrombolysis. Likewise, most investigators reported an association of improved heart-rate variability with a patent infarct-related artery. QT interval dispersion, a measure of ventricular arrhythmic risk, declines as antegrade infarct-related artery flow improves. High-risk patients undergoing programmed extrastimuli have a lower incidence of inducibility and an improved response to pharmacologic therapy after thrombolysis or with a patent infarct-related artery. The mechanisms of arterial flow's modulation of electrophysiologic substrate remains to be elucidated. Long-term follow-up of large post-infarction populations will be necessary to demonstrate benefit conclusively.