Key result
Atrial pacing during critical coronary stenosis decreases myocardial oxygen and raises carbon dioxide by ~40 mmHg.
Why the study?
Does atrial pacing alter regional myocardial gas tensions and blood flow in the presence of a critical coronary stenosis?
Does atrial pacing alter regional myocardial gas tensions and blood flow in the presence of a critical coronary stenosis?
Atrial pacing in the presence of critical coronary stenosis exacerbates subendocardial ischemia due to the failure of myocardial blood flow to increase in deeper myocardial layers to meet increased oxygen demand.
May signal ischemia risk with atrial pacing in stenosis; leaves open human translation and clinical relevance.
Changes in myocardial carbon dioxide (PmCO2) and oxygen tension (PmO2) measured by mass spectrometry have been shown to reflect quantitatively progressive degrees of regional myocardial ischemia associated with stepwise reduction in coronary blood flow. The present study utilized mass spectrometry to assess the severity of regional myocardial ischemia developing during atrial pacing in the presence of a flow-limiting proximal critical coronary artend subendocardial layers was measured by the radioactive microsphere technique. Application of a "critical stenosis" resulted in a 6-mmHg decrease in PmO2 and a 17-mmHg increase in PmCO2 in the region of the myocardium supplied by the stenosed vessel. The addition of atrial pacing resulted in a 3-mmHg further decrease in Pmo2 and a 40-mmHg further increase in PmCO2. In the region of myocardium supplied by the critically stenosed vessel MBF increased in the subepicardial layer, but decreased or remained unchanged in the subendocardial layer. The failure of myocardial blood flow to increase in deeper myocardial layers in response to the increased myocardial oxygen demand of atrial pacing would provide a mechanism for the development of subendocardial ischemia in the presence of a critical coronary stenosis.
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O'Riordan et al. (1977) studied Critical coronary stenosis and regional myocardial ischemia. Atrial pacing vs. Critical stenosis without atrial pacing was evaluated on Regional myocardial gas tensions (PmO2 and PmCO2). Atrial pacing during critical coronary stenosis caused a further 3-mmHg decrease in myocardial oxygen tension and a 40-mmHg increase in carbon dioxide tension.