Remote Ischemic Conditioning for Acute Ischemic Stroke: The RICAIS Randomized Clinical Trial

Abstract

Aims: Preclinical studies have shown that remote ischemic conditioning (RIC) has a neuroprotective effect; however, the findings of clinical studies are inconsistent. This study aimed to show the effect of RIC on acute ischemic stroke while considering its severity at baseline.

Methods: We enrolled 79 patients with ischemic stroke who had National Institute of Health Stroke Scale (NIHSS) scores of 5–20 within 48 h after stroke onset and randomized them into the RIC [n = 43] and control groups [n = 36]. The intervention was performed using an inflatable cuff on one lower extremity. In the RIC group, each treatment consisted of four cycles of 5 min cuff inflation and deflation. The treatment was repeated once daily for at least three days. Based on the NIHSS score, the patients were divided into three groups: mild (NIHSS 5–9), moderate (NIHSS 10–14), and severe (NIHSS 15–20). The primary outcome was a good functional outcome at 90 days, defined as a modified Rankin Scale score of 0–1 in the mild group, 0–2 in the moderate group, and 0–3 in the severe group.

Results: Among the 79 patients (mean age, 65.0 years, 40 women), 7 (16.3%) in the RIC group and 8 (22.2%) in the control group had good functional outcomes (odds ratio, 0.73 [95% confidence interval, 0.29-1.82];P = 0.502). The incidences of major adverse cardiovascular events, aspiration pneumonia, and serious adverse events were similar in both the groups.

Conclusion: Although this study may have been underpowered, RIC initiated within 48 h of stroke onset did not seem to improve the functional outcomes in acute ischemic stroke.

Introduction

Remote ischemic conditioning (RIC), a brief period of ischemia-reperfusion in the limb, is an inexpensive, well-tolerated, and universally applicable intervention that has been shown to have a protective effect against ischemic injury in target organs such as the heart, brain, and kidney in preclinical studies ¹⁾ . In rodent brain ischemia models, pre-RIC, per-RIC, and post-RIC have been shown to mitigate ischemic injury ²⁾ . Although the precise protective mechanisms remain unclear, three pathways have been proposed: humoral factors, neuron-mediated responses, and immunomodulatory factors ¹⁾ . Using a murine model of middle cerebral artery occlusion, we demonstrated that RIC augmented collateral circulation during vessel occlusion ³⁾ . The protective effect of RIC is equal to or greater than that of hypothermia treatment ⁴⁾ .

However, the findings of clinical studies are inconsistent. Two large-scale randomized controlled trials, The Remote Ischemic Conditioning for Acute Moderate Ischemic Stroke (RICAMIS) ⁵⁾ trial and the Remote Ischemic Conditioning in Patients with Acute Stroke Trial (RESIST) ⁶⁾ , have been published. In the RICAMIS trial, which included 1893 patients with acute ischemic stroke enrolled within 48 h of stroke onset, RIC improved functional outcomes. In contrast, in the RESIST trial, which included 902 patients with acute stroke, RIC initiated within 4 hours of symptom onset did not improve functional outcomes. Previous studies have reported conflicting findings ^{7 - 12)} .

One of the reasons for these conflicting results is the predefined functional outcome as the primary outcome, regardless of the variable initial severity ¹³⁾ . Initial stroke severity greatly influences the functional outcomes, although previous studies on RIC usually defined the primary outcome as a modified Rankin Scale (mRS) score of 0 or 1. Even recirculation intervention barely achieved an mRS score of 0 or 1 in patients with an initial stroke severity of moderate or severe symptoms. In this study, we set good functional outcomes considering initial stroke severity, so that approximately 35% of control patients achieved good functional outcomes, and aimed to prove that RIC showed a protective effect in patients with acute ischemic stroke. The protocol for this study has been previously published ¹³⁾ .

Aim

This randomized controlled study aimed to clarify the effect of RIC on acute ischemic stroke considering its severity at baseline.

Methods

Study Design

The Remote Ischemic Conditioning for Acute Ischemic Stroke (RICAIS) study was a multicenter, open-label, blinded-end point, randomized clinical trial that assessed the efficacy of RIC for at least three consecutive days in patients with acute ischemic stroke within 48 h of symptom onset. The protocol paper has been published ¹³⁾ . The first phase of this trial was conducted at a single center, Tokyo Women’s Medical University, as a pilot study of 12 patients, and the second phase was conducted at 13 medical sites in Japan ( Supplemental Table 1 ) . The trial protocol was approved by the Ethics Committee of Tokyo Women’s Medical University and other participating hospitals. Signed informed consent was obtained from patients or their legally authorized representatives. This trial has been registered in the UMIN Clinical Trial Registry (https://www.umin.ac.jp/:UMIN000046225).

Supplemental Table 1. Recruitment by sites in RICAIS trial.

Inclusion sites	Number of patients recruited
Department of Neurology, Tokyo Women’s Medical University	39
Department of Neurology, Iwate Prefectural Central Hospital	13
Department of Neurology, Toda Chuo general Hospital	11
Department of Neurology, Saitama Red Cross Hospital	5
Department of Neurology, Nippon Medical School	3
Department of Neurology, Osaka General Medical Center	2
Department of Stroke and Cerebrovascular Medicine, Kyorin University	2
Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University	1
Department of Neurology, The Jikei University School of Medicine	1
Department of Stroke Medicine, National Hospital Organization, Osaka National Hospital	1
Department of Neurology, Showa General Hospital	1

Patients

Adults aged ≥ 18 years were invited to participate if they had a clinical ischemic stroke with onset in the past 48 h and National Institute of Health Stroke Scale (NIHSS) scores of 5–20 at the time of randomization. Eligible patients had been functioning independently in the community before a stroke (modified Rankin Scale [mRS] scores 0–1; range 0 [no symptoms] to 6 [death]). Brain magnetic resonance imaging was performed on admission to identify patients with ischemic stroke and major vessel lesions. Patients who received intravenous thrombolysis or other endovascular therapies were enrolled at an interval of at least 12 h. The key exclusion criteria were as follows: uncontrolled severe hypertension (systolic blood pressure ≥ 180 mmHg), any contraindication for RIC (e.g., arteriosclerosis obliterans, foot gangrene), very mild (NIHSS score ≤ 4), or very severe symptoms (NIHSS score ≥ 21).

Randomization and Blinding

Eligible patients were randomly assigned to the RIC or control group using a web-based procedure. The participants were assigned in a 1:1 ratio to the RIC or sham group. The patients were divided into three groups (mild, moderate, or severe) according to their baseline NIHSS scores: 5–9, mild; 10–14, moderate; and 15–20, severe. Randomization was stratified according to age, sex, stroke center, and stroke severity (mild, moderate, or severe).

Procedures

A manual blood pressure cuff was placed around the lower leg or thigh on the unaffected side. The intervention (RIC) group received four cycles of 5 min of blood pressure cuff inflation, followed by 5 min of reperfusion. Cuff inflation was set at 200 or 50 mmHg above the systolic blood pressure. If the patient could not tolerate this pressure, the cuff pressure was reduced to 180 mm Hg. This procedure was performed once daily after enrollment for a minimum of three consecutive days and a maximum of seven days. Discomfort and pain were assessed using a verbal rating scale, ranging from 0 to 4 (0 = no pain; 1, mild pain; 2, moderate pain; 3, severe pain, and 4 = very severe pain) ¹³⁾ . Neurologic status, measured using the NIHSS, was assessed at baseline, 3 days, 7 days, and 1 month after discharge. Follow-up data were collected 90 days after randomization.

Outcomes

The primary endpoint was a good functional outcome 90 days after stroke onset, with target mRS scores of 0–1, 0–2, and 0–3 in the mild, moderate, and severe groups, respectively. The mRS scores were determined at the time of the clinical visit or by a structured telephone interviewer by various assessors blinded to the allocation results.

The secondary outcomes were the proportion of patients with good functional outcomes in each group; change in NIHSS score from baseline to day 7; incidence of major adverse cardiovascular events (MACE), aspiration pneumonia, and all-cause mortality within 90 days after stroke onset; frequency of discomfort and pain in the leg; and proportion of patients with an mRS score of 0–1, 0-2, and 0-3.

Any serious adverse events were defined as those that were fatal or life-threatening, that resulted in disability, that required hospitalization or extension of hospital stay, or that were judged as significant hazards that required medical or surgical interventions.

Sample Size Calculation

An effect corresponding to a 15% increase in the functional outcomes was assumed. Based on previous findings, we hypothesized that the rate of good functional outcomes was 35% in the control group and 50% in the RIC group. A sample size of 334 patients was required, with 80% power at a 5% significance level.

Statistical Analysis

All statistical analyses were conducted using the JMP 17 Pro software program (SAS Institute, Cary, NC, USA) and Stata 18.0 (StataCorp LLC, College Station, TX, USA). The difference in the proportion between the RIC and control groups in the primary outcome and good functional outcome was evaluated using the chi-squared test. Using the ordinal logistic regression model, common odds ratio and 95% confidence intervals (CI) were calculated, and a P-value ＜0.05 was considered statistically significant. Differences in proportions between the RIC and control groups in secondary outcomes, incidence of MACE, aspiration pneumonia, and all-cause mortality were evaluated using the chi-square test. The change in NIHSS score from enrollment to day 7 was assessed using the t-test.

Results

Before reaching the planned sample size of 344, the steering committee discontinued enrollment because of slow recruitment and funding cessation on February 28, 2024. As a result, a total of 79 patients were enrolled in the study ( Fig.1 ) . They were assigned to the RIC group (N = 43) or the control group (N = 36). The patients’ background characteristics are shown in Table 1 . The mean age (±standard deviation [SD]) was 71.9±12.6 years. Approximately 70 % were male, and the mean NIHSS score (±SD) was 9.0±4.0. In terms of stroke severity, the number of patients in the mild (NIHSS scores 5–9), moderate (NIHSS scores 10–14), and severe (NIHSS scores 15–20) groups were 51, 10, and 18, respectively. Of the patients, 25.3% and 16.5% received alteplase and endovascular treatment, respectively, before enrollment. Major vessel lesions were present in 35.4% of the patients. Among the 79 patients, 23, 20, 9, 18, and 9 had cardiac embolism, atherosclerotic brain infarction, small vessel disease, other etiology, and unknown etiology, respectively. In the RIC group (N = 43), most patients (N = 39) received RIC for the first 3 days, the remaining four patients received intervention for 7 days.

Fig.1.

Patient flow chart

Table 1. Baseline characteristics.

Characteristics	Total (N = 79)	RIC (N = 43)	Control (N = 36)	P
Age, years	71.9±12.6	70.9±12.7	73.1±12.6	0.427
Sex, male %	69.6	69.8	69.4	0.975
Body mass index	23.1±3.8	22.4±4.5	23.9±2.8	0.099
Hypertension, %	65.9	55.8	66.7	0.325
SBP, mmHg	147.8±23.0	146.4±24.9	149.4±20.9	0.564
DBP, mmHg	85.2±16.6	85.5±18.0	84.9±15.0	0.879
Diabetes mellitus, %	25.3	23.3	27.8	0.645
FBS, mg/dl	131.8±45.8	131.3±39.2	132.4±53.1	0.913
Dyslipidemia, %	48.1	41.9	55.6	0.225
LDLC, mg/dl	115.3±40.0	113.1±40.1	117.9±40.2	0.608
HDLC, mg/dl	54.8±16.5	53.6±17.1	56.4±15.9	0.477
TG, mg/dl	118.3±61.6	117.8±66.7	118.9±55.9	0.939
Chronic kidney disease, %	41.8	46.5	36.1	0.351
eGFR	61.5±23.9	62.3±24.1	60.6±23.8	0.765
Atrial fibrillation, %	21.5	23.3	19.4	0.681
Current smoker, none/current/past	28/30/21	11/16/15	15/14/6	0.135
A history of stroke or TIA, %	11.4	14.0	8.3	0.434
A history of coronary artery disease, %	6.3	7.0	5.6	0.796
premorbid mRS 0/1	65/14	34/9	31/5	0.414
NIHSS	9.0±4.0	9.2±4.3	8.6±3.7	0.517
stroke subtype, CE/ATBI/SVD/Other/Unknown	23/20/9/18/9	13/11/6/10/3	7/12/3/8/6	0.482
Location of ischemic infarction, Anterior/Posterior	68/11	36/7	32/4	0.509
stroke severity, mild/mod/severe	51/10/18	27/7/9	24/3/9	0.558
Presence of major vessel occlusive lesion	35.4	34.9	36.1	0.910
Intravenous thrombolysis	25.3	27.9	22.2	0.563
Thrombectomy	16.5	20.9	11.1	0.241
interval from onset to randomization, 12-24 h/ 24-48 h	24/55	12/31	11/25	0.796
RIC intervention days, 3 days/ 4-7 days	39/4	39/4	n.e.	n.e.

Abbreviations: ATBI, atherothrombotic brain infarction; CE, cardioembolism; DBP, diastolic blood pressure; eGFR, estimated glomerular filtration rate; FBS, fasting blood sugar; HDLC, high-density lipoprotein cholesterol; LDLC, low-density lipoprotein cholesterol; mRS, modified Rankin scale; NIHSS, National Institute of Health Stroke Scale; RIC, remote ischemic conditioning; SBP, systolic blood pressure; SVD, small vessel disease; TG, triglyceride; TIA, transient ischemic attack

Good functional outcomes, defined as mRS scores at 90 days of 0–1 for mild, 0–2 for moderate, and 0–3 for severe groups, were achieved in 7 (16.3%) of 43 patients in the RIC group and 8 (22.2%) of 36 patients in the control group ( Table 2 ) . No significant differences were observed between the two groups. Regarding secondary outcomes, the rates of good functional outcomes in the RIC and control groups were 16.3% and 19.4% in the mild group, 22.2% and 22.2% in the moderate group, and 0% and 0% in the severe group. No differences were observed among the mild, moderate, and severe groups. The distribution of mRS scores in the RIC and control groups at 90 days is shown in Fig.2 . The median mRS scores were 3 (interquartile range [IQR] 2–4) and 4 (IQR 2–4). RIC was not associated with a significant shift toward better functional outcomes (adjusted common odds ratio, 1.600 [95% CI, 0.700 to 3.653]).

Table 2. Primary and secondary outcome.

	Group, No, (%)
	RIC (N = 43)	Control (N = 36)	Treatment effect metric	Treatment difference	(95% CI)		P value
Primary outcome
(mRS 0-1 at mild gorup, mRS 0-2 at moderate group, mRS 0-3 at severe group	7 (16.3)	8 (22.2)	RR	0.733	0.294	1.825	0.502
Secondary outcome
mRS 0-1 in total	7 (16.3)	7 (19.4)	RR	0.837	0.324	2.164	0.714
mRS 0-2 in total	14 (32.6)	11 (30.6)	RR	1.066	0.554	2.049	0.849
mRS 0-3 in total	25 (58.1)	16 (44.4)	RR	1.308	0.839	2.041	0.225
mRS 0-1 in mild group	5/27 (18.5)	6/24 (25.0)	RR	0.741	0.259	2.121	0.574
mRS 0-2 in moderate group	2/9(22.2)	2/9 (22.2)	RR	1.000	0.178	5.632	1.000
mRS 0-3 in severe group	0/7 (0)	0/3 (0)	RR	NA			NA
Change in NIHSS sciore at Day 7 from baseline (mean)	-1 (-3, 0)	-1 (-2, 0)	MD	-1.132	-2.719	0.455	0.920
MACE	3 (7.0)	2 (5.6)	RR	1.256	0.222	7.109	0.796
Aspiration Pneumonia	5 (11.6)	3 (8.3)	RR	1.395	0.358	5.443	0.629
Death within 90 d	0 (0)	4 (11.1)	RR	NA			NA

Abbreviations: mRS, modified Rankin scale; MACE, major cardiovascular events; NIHSS, National Institute of Health Stroke Scale; RIC, remote ischemic conditioning; RR, risk ratio; MD, mean difference. treatment effect is presented as RR or MD (95% CI) of RIC vs. control group, analyzed by chi-square test for risk ratio and t-test for mean difference.

Fig.2.

Distribution of the modified Rankin Scale scores at 90 days

Changes in NIHSS scores from baseline to day 7 were similar –1 (IQR –3 to 0) and –1 (IQR –2 to 0) in the RIC and control groups, respectively. The incidences of MACE and aspiration pneumonia were similar between the two groups. All-cause death was observed in 0 and 4 patients (ventricular tachycardia, cancer, suicide, and unknown causes) in the RIC and control groups, respectively.

The incidence of serious adverse events such as recurrent ischemic stroke, intracerebral hemorrhage, ventricular fibrillation, sick sinus syndrome, suicide, new-onset malignant neoplasm, and gastrointestinal bleeding were similar in both groups ( Supplemental Table 2 ) .

Supplemental Table 2. Serious Adverse Events by Randomized Groups.

Characteristics	RIC (N = 43)	Control (N = 36)	P
Recurrent ischemic stroke	2	2	0.855
Intracerebral hemorrhage	1	0	0.357
Ventricular fibrillation	0	1	0.271
Sick sinus syndrome	1	0	0.357
Suicide	0	1	0.271
Malignant neoplasm	0	1	0.271
Gastrointestinal bleeding	3	0	0.106

We conducted an exploratory subgroup analysis due to the small sample size. Age, sex, presence of diabetes mellitus, interval between onset and intervention, presence of recirculation therapy before enrollment, and presence of major vessel occlusive lesions did not appear to affect the primary outcome ( Fig.3 ) . The percentage of patients with good functional outcomes for each subtype of ischemic stroke was also similar between the RIC and control groups.

Fig.3.

CI indicates the confidence interval

In RIC-associated adverse events, six of 43 patients (14%) complained of leg pains (2 and 4 patients for verbal rating scales 1 and 2, respectively) that required changes in limb location or cuff pressure, but no serious adverse events occurred.

Discussion

In this study, RIC initiated within 48 h after stroke onset and performed once daily for ≥ 3 days did not significantly improve the functional outcomes at 90 days in patients with acute ischemic stroke. However, this study was underpowered to detect modest treatment effects and could not draw definitive conclusions. Regarding secondary outcomes, RIC did not change the NIHSS score during the first week and did not influence the incidence of MACE and aspiration pneumonia. All-cause mortality tended to be low in the RIC group; however, this effect seemed incidental because the etiology of all-cause death in the control group was not related to brain injury. In the exploratory analysis, RIC did not improve outcomes in the mild, moderate, and severe groups; patients older or younger than 80 years; patients with and without recirculation therapy; or those with and without major artery lesions.

One of the reasons for the discrepancy between preclinical and clinical studies is the variability in the severity of the ischemic insult at enrollment. Although ischemic insult and the period can be controlled in experimental models, the degree of ischemia and the presence of recirculation differ in each patient. In this study, we prioritized the severity of baseline neurological signs that markedly influenced the long-term functional outcomes at enrollment. We defined good functional outcomes separately in mild (NIHSS scores 5–9), moderate (NIHSS scores 10–14), and severe (NIHSS scores 15–20) groups so that 35% of patients in the control group could attain good functional outcomes ¹³⁾ . Based on the results of RECAST-2 study showing about 10% increase in good functional outcomes in RIC group ⁹⁾ , we expected a 15% increase in good outcomes by defining the outcomes separately in mild, moderate, and severe symptom groups. However, the RICAMIS study later showed a 7% increase in good functional outcomes in the RIC group ⁵⁾ . As a result, the assumption of a 15% increase in this study might be too high. Furthermore, the absence of good functional outcomes in the severe group in both arms would indicate a ceiling effect and which might conceal modest treatment effects.

Our results suggest that RIC is ineffective for brain protection in older adult patients with stroke, as several previous studies have shown ^{6 , 9 , 10)} . In an experimental model, RIC exhibited a protective effect at similar levels of hypothermia, which is the most effective strategy for brain protection in young animals, mainly through the augmentation of collateral circulation ⁴⁾ . However, the recruitment of collateral circulation requires the preservation of endothelial function ¹⁴⁾ , which is often impaired by aging and the presence of vascular risk factors ¹⁵⁾ such as hypertension ¹⁶⁾ and diabetes ¹⁷⁾ . Aging and the presence of vascular risk factors usually observed in patients with stroke may hamper the beneficial effects of RIC. The protocols of the RICAMIS trial ⁵⁾ and our study were similar, as both studies enrolled patients with moderate symptoms within 48 hours after onset. However, the RICAMIS trial showed a positive effect of RIC, whereas our study found no beneficial effects. Differences in the percentages of mRS scores 0–1 at 90 days (62.0% and 19.4% in the control group of RICAMIS and our study, respectively), age (65 years and 72 years in RICAMIS and our study, respectively), and intervention cycles (twice daily for 14 days and once daily for 3 days in RICAMIS and our study, respectively) may explain these inconsistent results. Therefore, the current results apply to the specific protocol tested in this study and do not exclude the potential benefits of more intensive or prolonged RIC strategies.

This study is associated with several limitations. The number of enrollments did not reach the expected sample size. However, based on the present results, obtaining a beneficial effect of RIC in the current protocol seems challenging, even when the sample size is doubled or doubled. The percentage of patients with good functional outcomes was remarkably lower than expected based on previous findings. The period of RIC intervention in this study was three days in most cases, which might be less than that in previous studies reporting the positive effects of RIC ⁵⁾ . The definition of a favorable functional outcome used in this study was determined from previous studies, but it was not fully validated for each participating site.

Conclusions

RIC initiated within 48 h after the onset of ischemic stroke and continued for three days did not seem to show a beneficial effect. Further clinical studies are needed to clarify the types and conditions of stroke that can benefit from RIC.

Acknowledgements

We thank Nouvelle Place Inc. (Toranomon 33 Mori Building 10F, 3-8-21, Toranomon, Minato-ku, Tokyo, Japan) for the web-based procedures and data management.

Grant Support

The study was supported by the Mihara cerebrovascular Disorders Research promotion Fund.

Conflict of Interest

Kazuo Kitagawa disclosed honoraria in Daiichi Sankyo and Eisai. Ryosuke Doijiri has received lecture fees from Daiichi Sankyo Co. Ltd., Medtronic, and Abbott. Yasuyuki Iguchi has received speaker honoraria from Abbvie, Alexion, Amgen Biogen, Bristol Myers Squibb, Chugai, CSL-Behring, Daiichi-Sankyo, Eisai, Fujimoto Pharma, JB, Mitsubishi-Tanabe, Novartis, Otsuka, Pfizer, Sumitomo Dainippon, and Takeda, and his research is supported from Böehringer-Ingelheim, Fujimoto Pharma, Chugai, JB, Daiichi-Sankyo, Mitsubishi-Tanabe, Medical Concierge Co.,Ltd., NAGATANIEN Co., Ltd.,Shionogi, and Otsuka. Kazumi Kimura received speaker honoraria from Daiichi Sankyo Co. Ltd. and Bristol-Myers Squibb.., Medtronic Japan Co. Ltd., and Medica Line Co. Ltd. Takanari Kitazono disclosed honoraria in Daiichi Sankyo.