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Mechanism of the bradycardia during coronary angiography
Insights
Coronary angiography dye can cause bradycardia (slow heart rate) through direct effects on heart pacemakers and reflex vagal responses. Atropine administration helped differentiate these mechanisms in patients with different coronary artery anatomy.
Area of Science:
- Cardiology
- Vascular Medicine
- Electrophysiology
Background:
- Bradycardia during coronary angiography can stem from direct dye effects or vagal reflexes.
- Patient anatomy, specifically the origin of nodal arteries, influences these responses.
Purpose of the Study:
- To investigate the mechanisms of bradycardia during coronary angiography.
- To differentiate between direct dye effects and reflex vagal influences on heart rate based on coronary artery anatomy.
Main Methods:
- Classified 15 patients into Type A (both nodal arteries from RCA) and Type B (AV nodal artery from RCA) anatomy.
- Recorded heart rates during coronary angiography before and after selective right coronary artery atropine infusion.
Main Results:
- Type A patients: Sinus bradycardia from RCA injection involved direct and reflex effects; from LCA injection, it was purely reflex and blocked by atropine.
- Type B patients: RCA injection caused reflex sinus bradycardia; atropine induced junctional rhythm, indicating direct junctional pacemaker suppression.
Conclusions:
- Angiographic dye reduces heart rate via direct pacemaker effects and reflex vagal suppression.
- Coronary artery anatomy dictates the interplay of direct and reflex mechanisms causing bradycardia during angiography.
Abstract:
Bradycardia occurring during coronary angiography may be due to the direct effect of dye or to reflex vagal effects on pacemaker centers. Fifteen patients were classified according to the origin of the sinus nodal and atrioventricular nodal arteries. In patients with type A anatomy, both the sinus and the atrioventricular nodal arteries arose from the right coronary artery. In those with type B anatomy, only the atrioventricular nodal artery arose from the right coronary artery. Heart rate recordings were made during coronary angiography before and after selective infusion of atropine (0.2mg) into the right coronary artery. In type A patients, the sinus bradycardia observed during right coronary dye injection was caused by a combination of both direct and reflex effects on pacemaker tissue. Sinus bradycardia occurring with left coronary dye injections was entirely reflex in nature and was completely blocked with right coronary arterial injection of atropine. In type B patients, sinus bradycardia with right coronary dye injections was produced by reflex suppression of the sinus pacemaker. A junctional rhythm was consistently produced after administration of atropine. Junctional bradycardia in type B patients was caused by direct suppression of the junctional pacemaker. Thus, angiographic dye appears to decrease heart rate by a direct effect on pacemaker tissue and by reflex vagal suppression of the sinus pacemaker.