Related Experiment Videos
Haemodynamic effects on the myocardial blood flow supply/oxygen demand ratio in pacing induced angina pectoris
Insights
In patients with coronary artery disease, the diastolic pressure time index/tension time index (DPTI/TTI) ratio significantly decreases before and during angina. This DPTI/TTI reduction reflects an imbalance in myocardial oxygen supply and demand during angina.
Area of Science:
- Cardiology
- Cardiovascular Physiology
Background:
- Angina pectoris arises from subendocardial oxygen supply-demand imbalance.
- Coronary artery disease (CAD) significantly impacts myocardial oxygenation.
Purpose of the Study:
- To investigate hemodynamic factors contributing to angina in CAD patients.
- To assess the myocardial oxygen supply/demand ratio using DPTI/TTI.
Main Methods:
- Studied 10 CAD patients undergoing progressive pacing.
- Measured myocardial oxygen demand via tension time index (TTI).
- Estimated potential subendocardial flow using diastolic pressure time index (DPTI).
Main Results:
- Increasing pacing rates significantly reduced DPTI and DPTI/TTI (P < 0.001) without altering TTI.
- DPTI/TTI reached minimum values preceding and at angina onset.
- Angina induced significant increases in LVEDP (P < 0.05) and decreases in dP/dt min (P < 0.01), further reducing DPTI/TTI.
Conclusions:
- DPTI/TTI effectively reflects the myocardial blood flow supply/oxygen demand ratio in CAD.
- Hemodynamic changes during angina exacerbate the reduced DPTI/TTI ratio.
Abstract:
Angina pectoris results from an imbalance between oxygen supply and demand in the subendocardium. The haemodynamic effects contributing to this imbalance have been studied in 10 patients with coronary artery disease. Myocardial oxygen demand was estimated from the tension time index (TTI), potential subendocardial flow from a diastolic pressure time index (DPTI), and the oxygen supply/demand ratio from (DPTI/TTI. With progressively increasing pacing rates up until induction of angina, no significant change in TTI was found whereas a significant fall in DPTI and DPTI/TTI occurred (P less than 0.001). During pacing runs with induction of angina DPTI/TTI reached a minimum value 5 s before,and at the onset of angina. No such relationship was seen for TTI or DPTI alone. A significant rise in LVEDP (P less than 0.05) and fall in dP/dt min (P less than 0.01) occurred at angina both contributing to a further reduction in DPTI and DPTI/TTI. Changes in DPTI/TTI may then reflect changes in the myocardial blood flow supply/oxygen demand ratio in the presence of coronary artery disease and haemodynamic changes before and at the induction of angina lead to a further reduction of this ratio.