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Coronary hemodynamics and coronary flow reserve after intracoronary diltiazem in humans
M C Vrolix1, D Sionis, J H Piessens
1Department of Cardiology, University Hospital Gasthuisberg, Leuven, Belgium.
Insights
Diltiazem, a calcium channel blocker, increased coronary artery diameter and blood flow but decreased coronary flow reserve in humans. This effect was more pronounced without nitrate pretreatment.
Area of Science:
- Cardiology
- Pharmacology
- Human Physiology
Background:
- Coronary hemodynamics are crucial for cardiac function.
- Calcium antagonists like diltiazem are used to manage cardiovascular conditions.
- Understanding diltiazem's specific effects on coronary arteries is important for clinical application.
Purpose of the Study:
- To investigate the impact of diltiazem on coronary hemodynamics in humans.
- To assess changes in coronary artery diameter, blood flow, and flow velocity after diltiazem administration.
- To evaluate the influence of nitrate pretreatment on diltiazem's effects.
Main Methods:
- Twenty patients with non-stenotic coronary arteries received an intracoronary diltiazem bolus.
- Patients were pretreated with either placebo or isosorbide dinitrate.
- Coronary artery diameter, blood flow, blood flow velocity, and coronary flow reserve were measured.
Main Results:
- Diltiazem significantly increased epicardial coronary artery diameter and coronary blood flow.
- A slight, non-significant increase in basal coronary blood flow velocity was observed.
- Coronary flow reserve significantly decreased, particularly in patients without nitrate pretreatment.
Conclusions:
- Diltiazem enhances coronary artery diameter and blood flow but reduces coronary flow reserve.
- The reduction in coronary flow reserve may be due to increased baseline flow or decreased maximal flow.
- Nitrate pretreatment may mitigate the reduction in coronary flow reserve caused by diltiazem.
Abstract:
To analyze the effect of the calcium antagonist diltiazem on coronary hemodynamics, epicardial coronary artery diameter, coronary blood flow and coronary blood flow velocity were assessed at baseline and after a 0.5 mg intracoronary bolus of diltiazem in nonstenotic coronary arteries of awake humans. Patients (n = 20) were first randomized to pretreatment with either placebo (n = 10) or isosorbide dinitrate (0.5 microgram/kg/min infusion; n = 10), and coronary flow reserve was measured before and after administration of diltiazem. There were significant increases in epicardial coronary artery diameter (10%; p = 0.0001) and coronary blood flow (30%; p = 0.0001) in all patients after administration of diltiazem. Whereas basal coronary blood flow velocity increased only slightly (7%; p = not significant), there was a significant decrease in coronary flow reserve (10%; p = 0.004). Increases in coronary diameter and blood flow after diltiazem were comparable in patients pretreated with placebo or nitrates. However, the decrease in coronary flow reserve was significant only in patients pretreated with placebo (19%; p = 0.0008). This reduction in coronary flow reserve could be due to "raising the floor" (increased baseline coronary blood flow) or "lowering the ceiling" (reduction of maximal coronary blood flow).