Table 1 Overview of the characteristics of the studies included in the systematic review.

From: Heart rate variability alterations in takotsubo syndrome and related association with psychological factors: a systematic review and meta-analysis

Study

TS: N, (mean age ± SD); N females (f)

Controls: N, (mean age ± SD); N females (f)

Controls’ diagnosis

Assessment (time)

HRV outcome measures

Psychological outcome measures

Significant findings

NOS score

Akashi et al., 2007*42

10 (70.1 ± 13.7); 8 f.

10 (70.0 ± 6.1); not defined

HV

2 ± 1 days after admission (0 months) and 3.0 ± 0.2 months after discharge (3 months)

Mean RR; SDNN; SDANN; pNN50; RMSSD; LF; HF; TF; LF/HF

None

SDNN: TS 0 months < HV (p = 0.007); TS 0 months < TS 3 months (p = 0.01)

SDANN: TS 0 months < HV (p = 0.01); TS 0 months < TS 3 months (p = 0.03)

TF: TS 0 months < HV (p = 0.005)

LF: TS 0 months < HV (p = 0.01); TS 3 months < HV (p = 0.02)

LF/HF: TS 3 months < HV (p = 0.006)

9

Bonnemeier et al., 2010**45

27 (68.6 ± 11); 26 f.

10 (64.5 ± 8); 10 f.

MB

Third day after hospital admission

Mean RR; SDNN; SDANN; RMSSD; LF; HF; LF/HF; 1/f PLS; ApEn; AC; DC

None

SDANN: TS > MB (p = 0.029)

LF: TS < MB (p = 0.028)

HF: TS > MB (p = 0.034)

LF/HF: TS < MB (p = 0.031)

1/f PLS: TS < MB (p = 0.008)

ApEn: TS > MB (p = 0.009)

AC: TS < MB (p = 0.005)

DC: TS > MB (p = 0.004)

7

Collste et al., 2014*48

22 (63.2); 21 f.

22 (63.6); 21 f.

HV

6 months after the acute event

SDNN; SDANN

Mental Stress Test

SDNN pre-stress Δ: TS > HV (p = 0.002)

7

Krstacic et al., 2012*41

25 (60.2 ± 8.3); 25 f.

50 (63.1 ± 7.2); 50 f.

HV

T1: hospital admission

T2: after few days when patients have already received beta blockers treatment

T3: at hospital discharge

Mean RR; SDNN; SDANN; LF; HF; LF/HF; H; DFA α1; DFA α2; ApEn

None

Mean RR: TS-T1 < HV (p < 0.05)

SDNN: TS-T1 < HV (p < 0.05); TS-T2 < TS-T3 (p < 0.05)

SDANN: TS-T1 < HV (p < 0.05); TS-T2 < TS-T3 (p < 0.05)

LF: TS-T1 > HV (p < 0.05); TS-T2 > TS-T3 (p < 0.05)

HF: TS-T1 < HV (p < 0.05); TS-T2 < TS-T3 (p < 0.05)

LF/HF: TS-T1 > HV (p < 0.01); TS-T2 > TS-T3 (p < 0.01)

H: TS-T1 < HV (p < 0.001); TS-T2 < TS-T3(p < 0.001)

DFA α1: TS-T1 > HV (p < 0.001); TS-T2 > TS-T3 (p < 0.001)

DFA α2: TS-T1 > HV (p < 0.05); TS-T2 > TS-T3 (p < 0.01)

ApEn: TS-T1 < HV (p < 0.001); TS-T2 < TS-T3 (p < 0.001)

8

Lazzeroni et al., 2022*46

10 (69 ± 7); 9 f.

9 (72 ± 7); 8 f.

HV

12–24 months following the acute TS episode

SDNN; pNN50; RMSSD; VLF; LF; HF; LF/HF; SamEn; FD

16PF; AAQ-II; STAI; BDI-II; COPE

SDNN: TS < HV (p = 0.048)

pNN50: TS < HV (p = 0.003)

RMSSD: TS < HV (p = 0.015)

HF: TS < HV (p = 0.030)

LF/HF: TS > HV (p = 0.012)

FD: TS > HV (p = 0.013)

8

Mayer et al., 2016**50

26 (64.9 ± 13.5); 26 f.

Normative data

–

Median time from the TS event to the time of investigation: 17.5 months

SDNN; SDANN; RMSSD

HADS; ESS; FSS; TICS; FPI-R; MOCA; Five point test; Stroop Task

Only descriptive data

2

Norcliffe-Kaufmann et al., 2016*47

10 (61.7 ± 11.7); 10 f.

10 (age not reported); 10 f.

HV

Mean time from the TS event to the time of investigation: 42.1 months

SDNN; pNN50; RMSSD; LF; HF

STAI; Somatic vigilance scale; Stroop Task; Event recall

SDNN: TS < HV (p = 0.035)

pNN50: TS < HV (p = 0.014)

RMSSD: TS < HV (p = 0.031)

HF: TS < HV (p = 0.079)

7

Ortak et al., 2009**43

39 (67.8 ± 10.5); 38 f.

Same group at different times

–

T1: day 1 after admission

T2: day 2 after admission

T3: day 3 after admission

T4: 3 months after hospitalization

Mean RR; SDNN; SDNNi; SDANN; RMSSD; TI

None

SDNN: TS-T1 < TS-T3 (p = 0.041); TS-T1 < TS-T4 (p = 0.002)

SDNNi: TS-T1 < TS-T3 (p = 0.050); TS-T1 < TS-T4 (p = 0.003)

SDANN: TS-T1 < TS-T3 (p = 0.005); TS-T1 < TS-T4 (p < 0.001)

RMSSD: TS-T1 < TS-T3 (p = 0.048); TS-T1 < TS-T4 (p = 0.050)

TI: TS-T1 < TS-T4 (p = 0.020)

3

Waldenborg et al., 2011**44

13 (70); 13 f.

Same group at different times

–

T1: within 3 days following symptom presentation

T2: after 3 months

Mean RR; SDNN; SDANN; TINN; pNN50; SDSD; RMSSD; VLF; LF; HF; TF

PTSS-10; MADRS-S

SDNN: TS-T1 < TS-T2 (p = 0.008)

SDANN: TS-T1 < TS-T2 (p = 0.008)

3

Watson et al., 2022***49

12 (67.3 ± 2.9); 12 f.

12 (66.2 ± 2.5); 12 f.

CP

Three registrations during experimental task in a follow-up visit (no time specified)

T1: baseline condition

T2: hyperventilation condition

T3: 5 min after

SDNN

Hyperventilation induced anxiety

SDNN: increased in response to hyperventilation (p < 0.001) but no differences between cases and controls

7

  1. * = Case–control study; ** = Prospective study; *** = Randomised cross-over trial; 16PF, 16 personality factors – C form; AAQ-II, acceptance and action questionnaire-II; AC, acceleration capacity; ApEn, approximate entropy; BDI-II, Beck depression inventory-II; COPE, coping orientations to problems experienced; CP, Patients seen by the cardiology service for investigation of chest pain or palpitations but free of significant cardiac pathology; DC, deceleration capacity; DFA, detrended fluctuation analysis; ESS, Epworth sleepiness scale; FD, fractal dimension; FPI, Freiburg personality inventory-R; FSS, fatigue severity scale; H, Hurst exponent; HADS, hospital anxiety and depression scale; HF, high frequency; HV, healthy volunteers; LF, low frequency; LF/HF, ratio between LF and HF; MADRS-S, Montgomery-Åsberg depression rating scale, self rated version; MB, midventricular ballooning; MOCA, Montreal cognitive assessment; PLS, power law slope; pNN50 = percentage differences between adjacent normal RR intervals exceeding 50 ms; PTSS-10, post-traumatic stress syndrome 10-questions inventory; RMSSD, root-mean-square successive difference between adjacent normal NN intervals; RR, time duration between two consecutive R waves of the ECG; SDANN, standard deviation of the average normal RR intervals for every 5 min of ECG recording; SDNN, standard deviation of normal RR intervals in ECG recording; SDNNi, mean standard deviation of RR intervals for all 5 min segments; SDSD, mean of standard deviations of normal RR intervals for all 5-min segments; STAI, , state-trait anxiety inventory; TF, total frequency; TI, triangular index; TICS, Trier inventory for chronic stress; TINN, baseline width of the minimum square difference triangular interpolation of the highest peak of the histogram of NN intervals; VLF, very low frequency.
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