The Effect of Diagnostic Hypercapnic Cerebrovascular Reactivity Imaging on Vital Signs and Acute and Follow-Up Ischemic Adverse Events in Patients with Flow-Limiting Intracranial Arterial Stenosis

BACKGROUND AND PURPOSE: Anatomical imaging is a hallmark for visualizing chronic and acute infarcts but provides incomplete information on stroke risk. Respiratory hypercapnic gas challenges show promise for noninvasively assessing hemodynamic function and mapping cerebrovascular reserve capacity, an indicator of how near parenchyma is to exhausting autoregulatory capacity. However, limited safety information exists for this method in high-risk patients with flow-limiting stenosis. This study reports on the physiologic changes and adverse events (AEs) following diagnostic hypercapnic cerebrovascular reactivity imaging assessments.

MATERIALS AND METHODS: Between January 2011 and May 2024, reactivity scans were performed on 262 patients. In patients with flow-limiting intracranial arterial steno-occlusion (>70%), vital signs were assessed during a twice-repeated three-minute fixed-inspired 5%CO₂/95%O₂ stimulus, with acute (0–24 hours), sub-acute (24 hours–2 months), and longer-term (2–12 months) AEs recorded.

RESULTS: 129 patients met criteria for flow-limiting arterial steno-occlusion. Blood pressure did not change (P > .40) with hypercapnia. End-tidal carbon dioxide (EtCO₂) (baseline: 36.5 ± 4.5 mm Hg, hypercapnia: 42.5 ± 3.8 mm Hg) and arterial oxygen saturation (SaO₂) (baseline: 97.5 ± 1.8%, hypercapnia: 99.4 ± 0.8%) increased (P < .001), paralleling hypercapnic-hyperoxic physiology. No acute ischemic adverse events were noted. One sub-acute and four long-term neurological events were noted within the expected range for this population.

CONCLUSIONS: Findings support the use of hypercapnic reactivity mapping in the setting of flow-limiting cerebrovascular disease.