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Substance P for evaluation of coronary endothelial function after cardiac transplantation
S S Kushwaha1, D C Crossman, M Bustami
1Department of Cardiology, Harefield Hospital, Middlesex, England.
Insights
Substance P effectively dilates coronary arteries in heart transplant recipients, showing preserved endothelial function. This vasodilator may be a valuable tool for assessing coronary health in these patients.
Area of Science:
- Cardiology
- Vascular Biology
- Pharmacology
Background:
- Endothelial dysfunction is a concern in cardiac transplant recipients.
- Substance P is an endothelium-dependent vasodilator with potential diagnostic applications.
Purpose of the Study:
- To evaluate the effect of substance P on coronary artery diameter in cardiac transplant recipients.
- To assess coronary endothelial function using substance P in this patient population.
Main Methods:
- Intracoronary infusion of substance P and isosorbide dinitrate in 12 cardiac transplant recipients.
- Measurement of coronary artery diameter changes in response to increasing doses of substance P.
- Comparison of maximal vasodilation induced by substance P and isosorbide dinitrate.
Main Results:
- Substance P produced dose-dependent vasodilation of coronary arteries.
- Maximal vasodilation with substance P was comparable to isosorbide dinitrate.
- Half maximal dilation was achieved at 1.4 to 2.8 pmol/min of substance P.
Conclusions:
- Coronary endothelial function is preserved in cardiac transplant recipients with normal coronary arteries.
- Substance P is a potential agent for assessing endothelial function in these patients.
Abstract:
The endothelium-dependent vasodilator substance P dilates normal and diseased coronary vessels in humans in vivo and produces a maximal response similar to that seen with intracoronary isosorbide dinitrate. Twelve cardiac transplant recipients underwent intracoronary infusion of substance P after routine annual investigations. All patients were well, with no evidence of rejection and with angiographically normal coronary arteries. Substance P was infused at 2 ml/min for 2 min into the coronary artery, starting at a dose of 1.4 pmol/min and increasing by doubling increments, and followed by isosorbide dinitrate (1 mg/min) infused over 2 min. Coronary artery diameter was measured in 23 vessel segments from 12 transplant recipients. The following doses were infused: saline solution (1 ml/min), substance P (0.7 [three patients], 1.4, 2.8, 5.6, 11.2, 22.4 pmol/min) and isosorbide dinitrate (1 mg/min). The mean percent increase in diameter (+/- SEM) in response to increasing doses of substance P was as follows: 0, 6.5 +/- 2.9%, 10.9 +/- 2.9%, 12.1 +/- 2.9%, 16.5 +/- 2.6%, 19.2 +/- 3.1% and 25.8 +/- 2.2%, respectively. Half maximal dilation was produced with 1.4 to 2.8 pmol/min of substance P; the maximal response (mean percent diameter change) was 22 +/- 2.5%. This was not significantly different from that achieved with isosorbide dinitrate. It is concluded that coronary endothelial function as assessed by response to substance P is preserved in cardiac transplant recipients with angiographically normal coronary arteries. Substance P may be a suitable agent for testing endothelial function in these patients.