Safety of dipyridamole testing in patients with cerebrovascular disease

The safety of carotid stenosis during vasodilator pharmacologic stress testing

BACKGROUND

While thousands of patients undergo stress testing annually, the risk of exercise and pharmacologic stress in patients with carotid artery disease has not been fully defined but is of concern as patients are at risk for cerebrovascular accidents and transient ischemic attacks.

METHODS

All patients with either ultrasound or CTA evaluation of their carotid arteries from over a 10 year period who underwent stress testing within 180 days without intervening carotid intervention were reviewed for any adverse events within 24 hours of their stress test. The primary end point was any cerebrovascular event or syncope while the secondary endpoints included death, myocardial infarction, urgent angiography, urgent revascularization, or exaggerated hemodynamic response (systolic BP drop > 20 mmHg or systolic BP > 180 mmHg at peak stress). Patients were stratified into categories based on their level of carotid disease. Patients with severe carotid stenosis were propensity matched to those with mild or no stenosis.

RESULTS

A total of 4457 patients underwent carotid ultrasound, 10,644 CTA, and 16,011 had stress testing during this time period with 514 having both a carotid evaluation and a stress test within 6 months. After propensity matching, 62 patients with severe carotid stenosis were matched to 170 patients with mild or no carotid stenosis. Incidentally, all patients with severe carotid stenosis underwent pharmacologic stress. There were no primary endpoints and only three secondary endpoints in two patients in the mild or no carotid stenosis group. The proportion of exaggerated hemodynamic response to stress was similar in both groups-21.0% in the carotid stenosis group vs 31.2% without (P = .17) having a significant drop in systolic BP, and 3.2% vs 4.7% (P = 1.0) having a significantly elevated systolic BP.

CONCLUSION

In this study cohort there were few primary and secondary outcome events with no events occurring in patients with significant carotid stenosis. Additionally, there was no difference in exaggerated hemodynamic responses. While these results suggest that stress testing entails no demonstrable increased risk in patients with significant carotid stenosis, continued care should be taken given the limitations of the small size of this study.

Cerebrovascular steal phenomenon in a patient undergoing dipyridamole nuclear perfusion cardiac imaging

Transient ischemic neurological deficits following intravenous dipyridamole administration during pharmacological cardiac stress test are seldom reported, but there can be serious vascular complications. We report a case of a 58-year-old Caucasian male who developed expressive aphasia after dipyridamole infusion during an elective dipyridamole-technetium cardiac stress test performed for chest pain. Computed tomography angiogram of the neck revealed a known total occlusion of the right internal carotid artery and 50% stenosis of the left internal carotid artery. The patient's aphasia spontaneously resolved within 24 h. In this paper, we report a unique case in which the administration of intravenous dipyridamole precipitated transient ischemic attack in a patient with stable asymptomatic bilateral carotid artery disease and prior carotid endarterectomy. We also discuss the intracerebral vascular steal phenomenon as a possible pathophysiological mechanism in this patient.

Dipyridamole modulated Tc-99m sestamibi lung SPECT in small cell lung cancer

PURPOSE

In this study, the authors wanted to determine whether dipyridamole-modulated MIBI (dipyridamole-MIBI) could enhance the prediction of the response to chemotherapy in patients with small cell lung cancer.

METHODS

Twenty-seven patients with biopsy-proved small cell lung cancer (25 men, 2 women; mean age, 61 +/- 7 years) underwent dipyridamole-MIBI SPECT 3 to 7 days before starting chemotherapy (80 mg/m2 etoposide and 80 mg/m2 cisplatin every 3 or 4 weeks for at least two cycles). Tomographic images before and after dipyridamole (0.84 mg/kg) were acquired 1 hour after injection of 370 (10 mCi) and 1,110 (30 mCi) MBq MIBI, respectively. The response to chemotherapy was grouped as specified as complete response (CR), partial (PR), no change (NC), or progressive disease (PD), according to the change in tumor size on chest roentgenography and CT. Patients showing CR and PR were classified as responders, and those who showed NC and PD were considered nonresponders.

RESULTS

Among the 27 patients, 22 were responders (3 CR, 19 PR) and 5 were nonresponders (3 NC, 2 PD). The tumor-to-normal lung ratio (T:NL) of responders was significantly higher than that of nonresponders. The diagnostic accuracy of the T:NL ratio to differentiate responders and nonresponders was 33.3%, with a cutoff value of 2.5, which was significantly improved to 77.8% when an increased T:NL ratio after dipyridamole was assigned to a nonresponder. Furthermore, all patients with CR showed diminished T:NL ratios after dipyridamole, and all patients with NR showed an increased T:NL ratio after dipyridamole.

CONCLUSION

Dipyridamole-MIBI SPECT could enhance the prediction of response to chemotherapy in patients with small cell lung cancer.