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 non-invasively 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 physiological 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, and acute (0–24 hours), sub-acute (24 hours – 2 months), and longer-term (2 – 12 months) AEs were recorded.

RESULTS: 129 patients met criteria for flow-limiting arterial steno-occlusion. Blood pressure did not change (p>0.40) with hypercapnia. EtCO₂ (baseline:36.5±4.5 mmHg, hypercapnia:42.5±3.8 mmHg) and SaO₂ (baseline:97.5±1.8%, hypercapnia:99.4±0.8%) increased (p<0.001), paralleling hypercapnic-hyperoxic physiology. No acute ischemic adverse events were noted. One sub-acute and four long-term neurological events were noted, within expected range for this population.

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

ABBREVIATIONS: CVR = cerebrovascular reactivity, MRI = magnetic resonance imaging, EtCO₂ = end-tidal carbon dioxide, SaO₂ = arterial oxygen saturation, BOLD = blood oxygenation level-dependent, AE = adverse event, SAE = serious adverse event