Sympathetic stimulation using the cold pressor test increases coronary collateral flow

Background: Little is known about the vasomotor function of human coronary collateral vessels. The purpose of this study was to examine collateral flo w under a strong sympathetic stimulus (cold pressor test, CPT). Methods: In 30 patients (62 +/- 12 years) with coronary artery disease, two subsequent coronary artery occlusions were performed with random CPT durin g one of them. Two minutes before and during the 1 minute-occlusion, the pa tient's hand was immerged in ice water. For the calculation of a perfusion pressure-independent collateral flow index (CFI), the aortic (P-ao), the ce ntral venous (CVP) and the coronary wedge pressure (P-occl) were measured: CFI = (P-occl- CvP) / (P-ao - CVP). Results: CPT lead to an increase in P-ao from 98 +/- 14 to 105 +/- 15 mm Hg (p = 0.002). Without and with CPT, CFI increased during occlusion from 14% +/- 10% to 16% +/- 10% (p = 0.03) and from 17% +/- 9% to 19% +/- 9% (p = 0 .006), respectively, relative to normal flow. During CPT, CFI was significa ntly higher at the beginning as well as at the end of the occlusion compare d to identical instants without CPT. CFI at the end of the control occlusio n did not differ significantly from the CFI at the beginning of occlusion w ith CPT. Conclusions: During balloon occlusion, collateral flow increased due to col lateral recruitment independent of external sympathetic stimulation. Sympat hetic stimulation using CPT additionally augmented collateral flow. The col lateral-flow-increasing effect of CPT is comparable to the recruitment effe ct of the occlusion itself. This may reflect a coronary collateral vasodila tion mediated by the sympathetic nervous system.