Ventricular sensory endings mediate reflex bradycardia during coronary arteriography in humans

Abstract

It has been suggested that the response to the intracoronary injection of radiographic contrast is reflex in origin and results from stimulation of ventricular sensory endings. Cardiac transplantation results in denervation of the ventricles, and thus, may interrupt the afferent limb of this reflex. In contrast, the recipient sinus node and atrial remnant remain innervated, leaving the efferent cardiac limb of this reflex intact. We hypothesized that if contrast-induced reflex bradycardia and hypotension occurred from stimulation of ventricular chemosensitive endings, then this response would be abolished after cardiac transplantation. To test this hypothesis, we determined the changes in recipient (innervated) and donor (denervated) sinus-node rates (SNR) and mean arterial pressure during selective right (RCA) and left coronary artery (LCA) injection during arteriography in cardiac transplant patients and in patients with intact cardiac innervation. An increase in the recipient SNR was observed in cardiac transplant patients during left and right coronary injections (LCA, 6.6 +/- 1.7 beats/min; RCA, 2.4 +/- 1.4 beats/min) compared with a decrease in the control subjects (LCA, -15.3 +/- 2.3 beats/min; RCA, -6.9 +/- 1.9 beats/min; p less than 0.05 vs. control). This occurred despite significant and comparable decreases in mean arterial pressure in cardiac transplant patients (LCA, -12.7 +/- 2.3 mm Hg; RCA, -11.4 +/- 2.2 mm Hg) and control subjects (LCA, -18.7 +/- 1.7 mm Hg; RCA, -10.7 +/- 1.6 mm Hg). The donor SNR slowed for LCA injection (-5.4 +/- 2.1 beats/min, p less than 0.05) and RCA injection (-3.0 +/- 1.7 beats/min), which, for the LCA, was less than the slowing of control subjects (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)