Effect of spinal cord stimulation on myocardial blood flow assessed by positron emission tomography in patients with refractory angina pectoris

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Spinal cord stimulation in angina pectoris increases exercise capacity and reduces both anginal attacks and ischemic electrocardiographic signs. This suggests an anti-ischemic action, perhaps through changes in myocardial blood flow. In 9 patients, regional myocardial blood flow was studied with positron emission tomography before and after 6 weeks of spinal cord stimulation, both at rest and during a dipyridamole stress test. Frequency of anginal attacks ana consumption of short-acting nitrates were assessed by patient diaries. Exercise duration and time to angina were measured with treadmill exercise tests. After 6 weeks of stimulation, both frequency of daily anginal attacks and nitrogen consumption decreased (3.7 ± 1.7 vs 1.4 ± 1.0 [p < 0.01] and 2.8 ± 2.2 vs 1.1 ± 1.2 tablets [p = 0.01], respectively); exercise duration and time to angina increased (358 ± 165 vs 493 ± 225 seconds [p < 0.01] and 215 ± 115 vs 349 ± 213 seconds [p = 0.02], respectively); and ST-segment depression during dipyridamole stress testing was reduced (0.17 [0 to 0.5] mV vs 0.09 [0 to 0.2] mV, p = 0.04) (all data mean ± SD). Total resting blood flow remained unchanged (115 ± 29 vs 127 ± 31 ml/min/100 g, p = 0.31), but flow reserve decreased (146 ± 43% vs 122 ± 39%, p = 0.04). The coefficient of variation of flow, representing flow heterogeneity, decreased after treatment, both at rest (20.1 ± 3.8% vs 17.4 ± 2.6%, p = 0.04) and after dipyridamole stress (26.2 ± 4.4% vs 22.9 ± 5.5%, p = 0.02). Thus, spinal cord stimulation is clinically effective due to homogenization of myocardial blood flow. Since flow reserve decreases despite clinical improvement, the dipyridamole effect may be blunted by spinal cord stimulation.