Table 1.

Recent Studies on the Relationship of HRV and Cerebral Stroke

Author, (Year)	Population	Study Design	HRV Measurement	Outcomes Evaluation	Results
Wang et al18 (2024)	191 patients with mechanical thrombectomy treated after acute ischemic stroke 58.6% male Mean age 65.5 years 51 (26.7%) died at 3-month follow-up	Retrospective cohort study	The initial 72 h of hourly heart rate information after MT therapy was acquired. HRV using 2 statistical methodologies, ie SD and CV were calculated.	All-cause mortality at 3-month. Change in mRS score at 14-day and 3-month	Increased mean heart rate per 10-bpm, heart rate SD and CV per 5-unit were all associated with the increased risk of mortality
Wu MJ et al17 (2024)	58 patients with ischemic stroke 56.9% male Mean age 70 years	Prospective cohort study	The frequency-domain HRV parameters included TP, LF, HF, LF/HF ratio, and LF%. A time-domain HRV parameter, the RR mean was also examined.	The behavioral functional outcome was represented by a mRS score at 3-month.	The median of RR mean, alongside specific clinical factors and neurological function at admission, may serve as potential prognostic indicators for 3-month outcome in ischemic stroke.
Dimova V et al19 (2024)	42 acute stroke patients. 16 women Mean age 66 years 20 matched controls. 10 women Mean age 60.7 years	Prospective study	HRV was assessed at rest, in a supine position and individual breathing rhythmus for 5 min. The VC, RMSSD, LF, and HF, frequency bands were used.	Acute stroke lesions were marked on diffusion-weighted images employing MRIcroN and co-registered to a T1-weighted structural volume-dataset.	The results suggest that HRV alteration after acute stroke might be due to affecting resting-state brain networks.
Nelde A et al20 (2024)	1755 stroke patients with 96 SAP. 960 males Mean age 73.8 years	Retrospective cohort study	HRV parameters were SDNN, RMSSD, LF, HF, LF/HF.	Based on HRV and other large-scale clinical data warehouses to predict SAP using automated machine learning.	HRV along with HR and blood pressure metrics during the first 48 h after admission exhibited distinct differences between patients with SAP diagnosis and those without.
Filchenko I et al21 (2023)	359 acute ischemic stroke patients with 20% developed a future CCVE. 129 females Mean age 67.1 years	Prospective longitudinal observational cohort study	HRV-parameters were represented in 3 main domains: the time domain was represented by rrHRV, SDNN, SDSD, TI, RMSSD, and pNN50. The frequency domain was represented by nuLf power, nuHF power, nuLF/nuHf ratio, LF power, HF power and VLF power. Lastly, non-linear measurements were represented by SD1 and SD2 from Poincaré plots, SD1/SD2 ratio, DFA1, DFA2 and ApEn.	The main outcome of the study was a composite of fatal and non-fatal future CCVE that included ischemic or hemorrhagic stroke, transient ischemic attack, myocardial infarction, unplanned hospitalization for unstable angina or heart failure and urgent revascularization.	High blood pressure variability, high nocturnal HRV and endothelial function contribute to the risk for future CCVE after stroke.
Qu Y et al22 (2023)	466 patients with acute stroke, of which 224 underwent IVT (48.1%), and 242 did not (51.9%) IVT group:182 male, mean age 57.95 years Non-IVT group: 210 male, mean age 57.41 years.	Prospectively study.	In the time domain, the RMSSD was analyzed. In the frequency domain, LF, HF, TP were analyzed.	A modified Rankin scale score ≥2 at 90 days was defined as an unfavorable outcome.	Lower HRV values at 1 to 3 and 7 to 10 days after stroke were independently associated with unfavorable outcomes in patients with acute ischemic stroke after IVT, and addition of heart rate variability parameters to conventional risk factors significantly improved the predictive ability of 3‐month unfavorable outcomes.
Qu Y et al23 (2023)	122 patients with ICH and 122 age- and sex-matched volunteers were included. 90 male Mean age 54.7 years	Prospective study	Time domain (SDNN, CV) and frequency domain (TP, VLF, LF, HF, LF%, HF%, LF/HF) indices were calculated.	A modified Rankin Scale score ≥ 3 at 3 months was defined as a poor outcome.	The time domain and absolute frequency domain HRV parameters (total power, LF, and HF) in the ICH group were significantly decreased within 7 days and 10–14 days. And LF% and HF% measured at 10–14 days were independently associated with 3-month outcomes.
Tian Y et al24 (2023)	4676 acute ischemic stroke patients.	A multicenter prospective observational clinical cohort study.	HRVs were generated from ECG recordings in participants who received 24-h Holter monitoring within 7 days of hospitalization. Two most commonly time-domain HRV indicators were used including SDNN and RMSSD.	All neuroimaging markers of CSVD, including WMH, EPVS, lacunes, CMBs, and BA, were analyzed according to a 3.0 Tesla MRI.	Decreased HRV parameters, including RMSSD and SDNN, were partly associated with the presence, severity, and imaging markers of CSVD.
Tian Y et al25 (2023)	A total of 5743 participants 3316 males Mean age 62.0 years	A prospective multiple -centers study.	HRV parameters were SDNN, a time-domain HRV parameter, calculated by the standard deviation of all normal N–N intervals (R-R intervals) over 24 h in milliseconds (ms).	The primary outcome was recurrent stroke (including recurrent ischemic stroke and recurrent hemorrhagic stroke) at 1-year follow-up.	The combination of HRV and ABCD2 score might efficiently stratify the risk of 1-year recurrent stroke After MS/TIA. Moreover, lower SDNN was independently related to recurrent stroke in patients with MS/TIA, Especially for those with low-to-moderate traditional vascular risk factors.
Aftyka J et al16 (2023)	59 patients with AIS 58% were females Mean age 65.6 ± 13.2 years	Retrospective study	Night HRV was analyzed from the nocturnal ECG recordings from 10 p.m. to 6 a.m data from 24 h Holter ECG during hospitalization. They employed an original and innovative non-linear measure was to analyze HRV, which was based on symbolic dynamics consisting of comparing the “length of the longest words”.	The mRS score was assessed for 3 months follow-up.	Results showed the non-linear, symbolic method for HRV analysis could be as a predictor of prolonged hospitalization and increased risk of clinical progression in AIS.
Nelde A et al12 (2023)	287 stroke patients 45.6% female Mean age 74.5 years	Retrospectively observational cohort study	HR was calculated as the number of beats per minute. Five HRV measures were considered in this study: SDNN, RMSSD, LF, HF, and LF/HF.	The short-term unfavorable functional outcome after stroke indicated through mRS score of > 2 at discharge.	The examined HRV parameters were not associated with the outcomes after stroke at discharge.
Von Rennenberg R et al26 (2021)	308 patients with AIS 37% female Median age 69 years	Prospective study	HRV parameters were assessed during the in-hospital stay using a 10-min section of each patient’s ECG recording at day and nighttime, calculating time and frequency domain HRV parameters.	Endpoint of recurrent stroke, myocardial infarction or death of any cause and the respective individual events were assessed 12 months after the index stroke. Patients’ functional outcome was measured by mRS at 12 months.	HRV did not predict recurrent vascular events or functional outcome in patients with AIS.

Abbreviations: AIS, acute ischemic stroke; CCVE, cerebro-cardiovascular events; CV, coefficient of variation; CSVD, cerebral small vessel disease; HF, high frequency; ICH, intracerebral hemorrhage; IVT (intravenous thrombolysis); LF, low frequency; mRS, modified Rankin Scale; RMSSD (root mean square of successive differences); SAP, stroke-associated pneumonia; SD, standard deviation; TP, total power.