Effect of an increase in coronary perfusion on transmural ventricular repolarization
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Published on: June 28, 2019
1Department of Cardiology, Renji Hospital, Medical School of Shanghai Jiaotong University, Shanghai, China.
Insights
Increased coronary blood flow prolongs ventricular repolarization duration, measured by activation-recovery interval (ARI). This effect, linked to nitric oxide, impacts cardiac electrophysiology.
Area of Science:
- Cardiology
- Physiology
- Electrophysiology
Background:
- Ventricular repolarization is crucial for cardiac electrical stability.
- The influence of altered coronary flow on repolarization dynamics remains incompletely understood.
- Nitric oxide is implicated in regulating coronary blood flow and cardiac function.
Purpose of the Study:
- To investigate the impact of increased coronary blood flow on transmural ventricular repolarization.
- To determine the role of nitric oxide in mediating flow-induced changes in repolarization.
Main Methods:
- Six pentobarbital-anesthetized sheep underwent coronary flow augmentation via left circumflex coronary artery (LCX) blood injection.
- Unipolar electrocardiograms were recorded from epicardial, mid-myocardial, and endocardial layers.
- Activation-recovery interval (ARI) was measured to assess ventricular repolarization duration.
Main Results:
- Increased coronary flow significantly prolonged ARI across all ventricular layers: epicardium (34±16 ms), mid-myocardium (28±18 ms), and endocardium (25±13 ms).
- Pretreatment with nitro-L-arginine, a nitric synthase inhibitor, attenuated the ARI prolongation.
- These findings suggest a role for nitric oxide in the observed electrophysiological changes.
Conclusions:
- Elevated coronary blood flow lengthens the duration of transmural ventricular repolarization.
- The effects of increased coronary flow on repolarization appear to be mediated by nitric oxide derived from the coronary endothelium.
Abstract:
The effect of increased coronary flow on transmural ventricular repolarization was investigated in six pentobabital-anesthetized sheep. Fresh blood at 10 ml/min was injected into the left circumflex coronary artery (LCX) in addition to the normal coronary flow. Unipolar electrocardiograms were simultaneously registered from epicardium, mid-myocardium and endocardium with fine plunge needles. Activation-recovery interval (ARI) was measured from the unipolar electrocardiograms and was used for estimating the ventricular repolarization duration. It was found that intracoronary blood injection (n=3) prolonged ARI in the epicardium, mid-myocardium and endocardium by an average of 34 +/- 16, 28 +/- 18 and 25 +/- 13 ms, respectively (p<0.01). Pretreatment with nitro-L-arginine (n=3), a nitric synthase inhibitor, diminished the flow-induced ARI prolongation across the ventricular wall. In conclusion, an increase in coronary flow lengthens the duration of transmural ventricular repolarization. These effects appear to be mediated by nitric oxide from the coronary endothelium.
