Comparison of technetium Tc 99m hexamethylpropyleneamine oxime single-photon emission tomograph with stump pressure during the balloon occlusion test of the internal carotid artery

Abstract

Background and purpose: Measuring blood pressure (stump pressure) in the distal internal carotid artery during occlusion of the internal carotid artery is reportedly a reliable safety index with which to predict ischemia following permanent occlusion of the internal carotid artery. We compared the stump pressure during occlusion of the internal carotid artery with single-photon emission CT (SPECT) using technetium Tc 99m hexamethylpropyleneamine oxime (HMPAO).

Methods: Twenty-seven patients underwent the balloon occlusion test. After occlusion of the internal carotid artery was performed by a balloon catheter, technetium Tc 99m HMPAO was injected, and then the balloon remained inflated for 15 minutes. The stump pressure was continuously monitored for those 15 minutes. After the balloon catheter was deflated and removed, SPECT was performed. Sixty-four symmetric pairs of regions of interest were set on both sides of the cerebral hemisphere. The radioactivity count ratio (L/n ratio) of the occluded side to the contralateral normal side was calculated. We defined hypoperfusion as an area with an L/n ratio <0.8. The minimum mean stump pressure (minMSP) during the balloon occlusion test and the pressure ratio of the minMSP to the mean systemic pressure were compared with the hypoperfusion area on SPECT.

Results: The number of regions of interest with hypoperfusion was significantly (P < .001) greater in patients with a minMSP <40 mm Hg (mean [+/-SD] = 31.5 +/- 13.7) than in patients with a minMSP > or =40 mm Hg (5.1 +/- 4.0). The number of regions of interest with hypoperfusion was also significantly (P < .001) greater in patients with a pressure ratio <0.5 (26.7 +/- 15.8) than in patients with a pressure ratio > or =0.5 (4.5 +/- 3.5).

Conclusion: The minMSP during the balloon test occlusion reflects the extent of the hypoperfused area measured by SPECT using technetium Tc 99m HMPAO.

Fig 1.

Graph shows the relationship between the minimum mean stump pressure and number of regions of interest (ROIs) with hypoperfusion. There was a significant correlation (P < .005 by Spearman rank correlation).

Fig 2.

Graph shows that the number of regions of interest (ROIs) with hypoperfusion was significantly (P < .001 by Mann–Whitney U test) greater in patients with a minMSP <40 mm Hg (31.5 ± 13.7) than in patients with minMSP ≥40 mm Hg (5.1 ± 4.0).

Fig 3.

In a 73-year-old man with hypopharyngeal carcinoma on the left side, the minMSP was 30 mm Hg during balloon test occlusion of the left internal carotid artery. SPECT using technetium Tc 99m HMPAO showed hypoperfusion of the cerebral hemisphere on the left side.

Fig 4.

In a 64-year-old man with meningioma invading the left internal carotid artery, the MSP was 64 mm Hg during balloon test occlusion of the left internal carotid artery. SPECT using technetium Tc 99m HMPAO showed no hypoperfusion areas of the cerebral hemisphere on the left side.

Fig 5.

Graph shows the relationship between the number of regions of interest (ROIs) with hypoperfusion and the pressure ratio of the minMSP to the minimum mean systemic pressure.

Fig 6.

Graph shows that the number of regions of interest (ROIs) with hypoperfusion was significantly (P < .001 by Mann–Whitney U test) greater in patients with a pressure ratio <0.5 (26.7 ± 15.8) than in patients with a pressure ratio ≥0.5 (4.5 ± 3.5)

Fig 7.

Graph shows the relationship between the minMSP and the mean L/n ratio (the radioactivity count of the occluded side / the radioactivity count of the contralateral normal side). There was a significant positive relationship (linear regression analysis; y = mean L/n ratio, x = minMSP; y = 0.71 + 0.005x; r = 0.497, P = .0084).