Spinal cord stimulation in angina pectoris. Studies on mechanisms and comparison with coronary artery bypass grafting

Abstract

Spinal Cord Stimulation (SCS) has been used in the treatment of refractoryangina pectoris since 1985 with favourable clinical results. Many reports have demonstrated ananti-ischaemic effect of the treatment but the underlying mechanism have not yet been elucidated.Ten patients were examined during atrial pacing and SCS in order to studythe effects on sympathetic activity. Sympathetic activity was measured with the isotopedilution technique. No effects on cardiac sympathetic were seen either by pacing or SCS. General sympathetic activity increased during pacing (47%, p=0.02) and this increase was attenuated (18%, p=0.02) when SCS was introduced. Effects on coronary flow velocity were examined in eight patients with coronary artery disease. A doppler guidewire was placed in a coronary artery and the patients were paced to angina and then SCS was introduced. The flow velocity increased during pacing (mean increase 53%, p<0.02). No effects on flow velocity were seen when SCS was introduced.Thus, it does not seem that the anti-ischaemic effects of SCS are secondary to modulation of cardiac sympathetic activity or increases in coronary flow velocity. The effects on generalsympathetic activity might be secondary to a decrease in ischaemia and pain or a primary effectof the treatment.104 patients with no proven prognostic benefit from CABG and with an increased surgical riskwere randomised between SCS and CABG. After 6 months both groups had adequate and similar symptom relief (p<0.0001). The CABG group had increased exercise capacity(p=0.02) and less ST-segment depression (p=0.005) at follow up compared to the SCS group.This difference might be explained by the fact that the SCS treatment was discontinued at followup. On an intention-to treat-basis, the mortality and cerebrovascular morbidity were lower in theSCS group (p=0.02; 0.03, respectively). These results indicate that SCS may be a therapeuticalternative to CABG in selected patient groups.These patients were subjected to a 24-hour ECG monitoring. This was performed withoutongoing stimulation in the SCS group, in order to study possible long-term effects of thetreatment. The number and duration of ischemic episodes decreased in the CABG group ascompared to the SCS group (p<0.05). The number of anginal attacks decreased in both groups (p<0.0001). There was a trend towards decrease in HRV in the CABG group. Thus, there are no indications of any long-term effects on ischemia of SCS. Furthermore, these results might indicate possible independent long-term analgesic effects of SCS even in patients treated forangina pectoris.