Effects of Cilostazol and Isosorbide Mononitrate on Cerebral Hemodynamics in the LACI-1 Randomized Controlled Trial

Supplemental Digital Content is available in the text.

C erebral small vessel disease (SVD) is a major cause of stroke and dementia. No specific treatment exists to stop disease progression. 1 SVD is associated with reduced cerebrovascular reactivity (CVR 2 ; the ability of blood vessels to increase blood flow), more pulsatile blood flow, and impaired cerebrospinal fluid (CSF) dynamics. 2,3 Isosorbide mononitrate (ISMN) and cilostazol have pharmacological effects that could improve these cerebrovascular dysfunctions. 1 Cilostazol can reduce stroke recurrence 4 and may reduce cognitive impairment. 5 Glyceryl trinitrate-a shorter-acting nitrate than ISMNimproved cognitive scores in some patients treated early after ischemic stroke. 6 Stroke. 2022;53:29-33. DOI: 10.1161/STROKEAHA.121. 034866 We measured CVR, cerebral blood flow, and CSF dynamics in patients with lacunar stroke randomly assigned to receive ISMN or cilostazol monotherapy, combination therapy, or avoid these medications in the LACI-1 trial (LACunar Intervention-1). 7

METHODS Data Availability Statement
Access requests can be submitted to the corresponding author.

Participants and Assessments
This study was a substudy of the main LACI-1 trial. LACI-1 was a phase IIa, partial factorial, prospective randomized open-label blinded end point trial. Our methods are published. 7 We recruited patients with nondisabling lacunar ischemic stroke.
All participants were scanned at randomization and at week 8 in the cilostazol monotherapy, ISMN monotherapy, and ISMN and cilostazol groups and week 3 in the no-medication group (after which this group commenced cilostazol and ISMN to test the alternative order of starting dual therapy). Medication compliance, side effects, and blood pressure (BP) were also assessed at each visit.
All participants provided written informed consent. Ethical approval was obtained from the Scotland-A Research Ethics Committee (Ref: 15/SS/0154).

Intervention
Participants were randomized to ISMN monotherapy, cilostazol monotherapy, combination ISMN, and cilostazol or no medication. 7 Dose was titrated to ISMN 25 mg BID and cilostazol 100 mg BID. 7 Medication was taken for 8 weeks. Participants were masked to treatment allocation, and investigators assessing outcomes including all image analysis were blinded to treatment allocation. 7

CVR Acquisition
During a 12-minute blood oxygen level-dependent magnetic resonance imaging (MRI) scan, participants alternated between breathing medical air and 6% carbon dioxide (CO 2 ) in air, as is published previously. 8

Pulsatility Acquisition
Our pulsatility method is published previously. 2, 3 We used a 2-dimensional cine phase-contrast sequence to measure flow in the internal carotid and vertebral arteries, superior sagittal, straight, and transverse venous sinuses, and foramen magnum and aqueduct CSF flow.

Image Analysis
We performed CVR analysis by regressing blood oxygen level-dependent signal against end-tidal CO 2 , with CVR expressed as %blood oxygen level-dependent signal change/mm Hg change in end-tidal CO 2 as published previously. 7,8 We extracted regional measurements of CVR in identical regions of the same anatomic structures at the two time points. Image analysis was performed by investigators blinded to treatment allocation.

Statistical Analysis
We used R, version 1.0.143, for statistical analyses. To examine the effect of treatment, 2 separate analyses were done. First, an intention-to-treat analysis (main article) and second, a per-protocol analysis (Supplemental Material) where participants who had stopped taking medication at the time of the follow-up scan were excluded from the treatment groups and analyzed as being in the no-medication group. We used multiple linear regression to assess the effect of treatment groups and being on any versus no medication on changes in white matter (WM) and gray matter CVR, PI, and CSF flow adjusting for age because this is suggested to affect CVR. This analysis was repeated and adjusted for systolic BP in place of age to examine the confounding effect of BP. To assure normality of the residuals and assess heteroscedasticity, we examined QQ plots, histograms of residuals, and plots of residual versus fitted values to examine.
This analysis was repeated and adjusted for systolic BP in place of age to examine the confounding effect of BP. Additional analyses were also performed controlling for systolic BP change in place of age between baseline and follow-up.

RESULTS
Twenty-seven of the 28 participants recruited to LACI-1 consented to the MRI substudy. Full CVR data sets were obtained in 23 participants and full pulsatility data sets in 24 (Supplemental Material). The Figure shows the CON-SORT flowchart.

Pulsatility Change After Treatment
Superior sagittal sinus PI increased with cilostazol alone. Vertebral artery PI decreased with ISMN alone ( Table 2). CSF pulsatility did not change.

DISCUSSION
Over an 8-week period, treatment with ISMN or cilostazol alone, or any drug versus no drug, increased WM but not gray matter CVR. Effects on pulsatility varied: ISMN decreased PI in the vertebral arteries; however, cilostazol increased superior sagittal sinus PI, which could be secondary to cilostazol increasing heart rate. 7 No changes in CSF flow dynamics were detected. Combination therapy did not have the effect of monotherapy although CVR in WM increased in participants taking any versus no medication, which includes those allocated dual therapy. Small numbers in each treatment group and participants finding it difficult to reach maximum dose of both drugs in combination means this is more likely sample size related and the true difference between effects of monotherapy versus combination remains undetermined. Prior studies have measured medication effects on resting cerebral blood flow in similar patient populations. The DANTE study (Discontinuation of Antihypertensives in the Elderly) showed no change in MRI-measured cerebral blood flow after antihypertensive medication withdrawal, compared with continuing antihypertensives. 9 The PRE-SERVE trial (Prevention of Serious Adverse Events Following Angiography) showed no change in MRI-measured cerebral blood flow with more versus less intensive BP lowering in patients with stroke-related moderate-to-severe SVD. 10 Others have demonstrated pravastatin, atorvastatin, perindopril, and vinpocetine all increase transcranial Doppler-measured vasoreactivity. [11][12][13][14][15] The changes in CVR we demonstrated were independent of any change in systolic BP induced by medication, adding further evidence that changes in blood flow and vascular function in older individuals with SVD have a complex relationship with BP. We have previously demonstrated stronger associations of WM than gray matter CVR with SVD. 2 WM may be differentially more impaired in SVD and thus more amenable to a detectable pharmacological improvement.
Lack of improvement in PI could reflect that modification of vascular stiffening requires longer treatment. Cilostazol has previously been shown to decrease PI after 90 days in patients with lacunar infarction. 16

Limitations
The sample is small. However, a primary aim of LACI-1 was to establish feasibility of the drug regimen to inform a larger trial (LACI-2; ISRCTN14911850) and secondarily to gather efficacy and safety data. 7,17 The randomization was imperfect, as in the overall main trial, 7 with the cilostazol-only group being older.

Conclusions
We demonstrated feasibility of cerebrovascular function MRI in a clinical trial of lacunar ischemic stroke and SVD and detected changes in CVR and pulsatility that support the positive modification of cerebrovascular function by existing medications. Larger studies over longer time periods will assess whether these improvements translate into clinical benefits.