Atherosclerosis of radial arterial graft may increase the potential of vessel spasm in coronary bypass surgery

Abstract

RA samples were collected during the procedure (with preopera- tive patient consent) and shipped to the research laboratory in 0.9% saline solution on ice. Intraoperative visual inspection was used to determine the presence or absence of atherosclerotic plaques, which was then confirmed by light microscopic examination of the endothelium in the laboratory. Photographs of normal and sclerotic vessels were taken with a digital camera with a 1:2 macro lens. The arteries were immediately transferred to oxygenated Krebs solu- tion (4°C), and the connective tissue was removed. The smooth muscle strip was carefully dissected and dissociated in an enzyme tube containing collagenase (type F, 1 mg/mL) and elastase (type IV, 0.12 mg/mL). The tissues were incubated with the enzyme in a 37°C bath for 45 minutes and carefully triturated to liberate free smooth muscle cells. Electrophysiologic responses were tested in cells that were phase dense and appeared relaxed. Cell membrane potential was recorded at room temperature with current-clamp mode after a gigaohm seal was obtained. Potassium and calcium currents were also examined with voltage-clamp for kinetic and phar- macologic characterization (data not presented). Acquisition and analysis of data were accomplished with Axopatch 200B and pCLAMP8 software (Axon Instruments, Inc, Foster City, Calif). Results Three atherosclerotic arteries were found among 38 RA samples in the study. These arteries were obtained from patients with no contraindications to coronary artery bypass grafting. Fat plaques and loss of elasticity of arterial wall were used as the diagnostic criteria. The membrane potentials of normal RA range from 30 to 70 mV, compared with 10 to 35 mV in their sclerotic counterparts. The average membrane potentials of normal and atherosclerotic RA tissues were 50.0 7.8 mV (n 4) and 20.3 6.0 mV (n 3, P.05), respectively. One of the sclerotic tissues also exhibited spontaneous spikelike hyperpolar- izations (indicative of sporadic activation of calcium-dependent potassium ion currents); this type of activity was not seen in any of the normal tissues. The membrane potential recordings of both groups are shown in Figure 1.