Assessment of nonlinear heart rate dynamics after beating-heart revascularization

Effects of Water-Based Exercise on Patients Older than 60 Years Undergoing Cardiac Rehabilitation after Coronary Intervention

Cardiac rehabilitation (CR) plays a crucial role in managing patients who have undergone coronary intervention (CI) following acute myocardial infarction. While water-based exercise is gaining recognition as an exercise modality in this patient population, its impact on the subgroup of older adults remains unexplored. In this post hoc analysis, we investigated the effects of water-based exercise on adults older than 60 years undergoing CR after CI, comparing it to land-based exercise and a control group. In total, 45 patients aged over 60 participated in 14-day exercise programs, featuring two daily 30-min sessions. We assessed exercise capacity (VO2peak), vascular function (flow-mediated vasodilation (FMD)), heart rate variability (HRV), and blood markers (Interleukins 6, 8, and 10, P-Selectin, ICAM, and High-sensitivity CRP) before and after CR. VO2peak in the water-based group improved significantly after CR in comparison with the land-based group: 1.35 kg/mL/min (95% CI [0.20-2.50], p = 0.022). The significant difference between water-based and land-based groups was observed in several HRV parameters: Total power -1129.20 ms2 (95% CI [-1951.92--306.49], p = 0.008); peak LF 0.04 Hz (95% CI [0.00-0.08], p = 0.036); SD1 -9.02 millisecond (95% CI [-16.86--1.18], p = 0.025); and SD2 -19.71 ms (95% CI [-35.08--4.34], p = 0.013). FMD and blood markers did not vary significantly based on the exercise group. These findings suggest that short-term water-based CR may have potential as an alternative to traditional land-based CR, improving VO2peak and cardiorespiratory fitness among adults over 60 years undergoing CR after CI.

Heart Rate Variability and Its Role in Predicting Atrial Fibrillation in Patients Undergoing Coronary Artery Bypass Graft

Background

An association between heart rate variability (HRV) and cardiac events in certain diseases has been demonstrated. However, the association with new-onset atrial fibrillation (AF) after coronary artery bypass grafting (CABG) is still controversial. This study aimed to investigate the association between HRV and new-onset AF in patients undergoing CABG during a 6-month follow-up.

Methods

This prospective study included 119 consecutive patients who underwent off-pump CABG. All patients were assessed using 24-hour Holter recordings 2 days before CABG and 1 week, 3 months, and 6 months postoperatively. HRV was analyzed, and AF was detected from its recordings.

Main results

In patients undergoing CABG, NYHA III increased the AF rate 7 days postoperatively, and advanced age and diabetes were associated with AF 6 months postoperatively. A reduction in time-domain measurements before surgery was significantly associated with a higher risk of developing AF seven days postoperatively; no association between preoperative HRV and AF was found at six months. Reduced preoperative HRV (SDNN (standard deviation of all normal-to-normal intervals [) < 50 ms) was an independent predictor of AF at 3 (AUC = 0.65) and 6 months (AUC = 0.62) following surgery.

Conclusion

A reduction in the time domain measurements before CABG was associated with a higher risk of new-onset AF at 7 days postoperatively but not at 6 months. An SDNN <50 ms was a weak independent predictor of a higher incidence of AF at 3 and 6 months post-surgery.

Cardiac autonomic regulation and PR interval determination for enhanced atrial fibrillation risk prediction after cardiac surgery

BACKGROUND

Changes in cardiac autonomic regulation and P-wave characteristics are associated with the occurrence of atrial fibrillation. The purpose of this study was to evaluate whether combined preoperative non-invasive determination of cardiac autonomic regulation and PR interval allows for the identification of patients at risk of new-onset atrial fibrillation after cardiac surgery.

METHODS

RR, PR and QT intervals, and linear and non-linear heart rate variability parameters from 20 min high-resolution electrocardiographic recordings were determined one day before surgery in 150 patients on chronic beta blockers undergoing elective coronary artery bypass grafting, aortic valve replacement, or both, electively.

RESULTS

Thirty-one patients (21%) developed postoperative atrial fibrillation. In the atrial fibrillation group, more arterial hypertension, a greater age, a higher EuroSCORE II, a higher heart rate variability index (pNN50: 9 ± 20 vs. 4 ± 10, p = 0.050), a short PR interval (156 ± 23 vs. 173 ± 31 ms; p = 0.011), and a reduced short-term scaling exponent of the detrended fluctuation analysis (DFA1, 0.96 ± 0.36 vs. 1.11 ± 0.30 ms; p = 0.032) were found compared to the sinus rhythm group. Logistic regression modeling confirmed PR interval, DFA1 and age as the strongest preoperative predictors of postoperative atrial fibrillation (area under the receiver operating characteristic curve = 0.804).

CONCLUSIONS

Patients developing atrial fibrillation after cardiac surgery presented with severe cardiac autonomic derangement and a short PR interval preoperatively. The observed state characterizes both altered heart rate regulation and arrhythmic substrate and is strongly related to an increased risk of postoperative atrial fibrillation.

Comparative study of short-term cardiovascular autonomic control in cardiac surgery patients who underwent coronary artery bypass grafting or correction of valvular heart disease

Introduction: Our aim was to perform a comparative study of short-term cardiovascular autonomic control in cardiac surgery patients who underwent coronary artery bypass grafting (CABG) or surgical correction of valvular heart disease (SCVHD ). Methods: The synchronous 15 minutes records of heart rate variability (HRV) and finger's photoplethysmographic waveform variability (PPGV) were performed in 42 cardiac surgery patients (12 women) aged 61.8 ± 8.6 years (mean ± standard deviation), who underwent CABG, and 36 patients (16 women) aged 54.2 ± 14.9 years, who underwent SCVHD , before surgery and in 5-7 days after surgery. Conventional time and frequency domain measures of HRV and index S of synchronization between the slow oscillations in PPGV and HRV were analyzed. We also calculated personal dynamics of these indices after surgery. Results: We found no differences (Р > 0.05) in all studied autonomic indices (preoperative and post-surgery) between studied patients' groups, except for the preoperative heart rate, which was higher in patients who underwent SCVHD (P = 0.013). We have shown a pronounced preoperative and post-surgery variability (magnitude of inter-quartile ranges) of all autonomic indices in studied patients. In the cluster analysis based on cardiovascular autonomic indices (preoperative and post-surgery), we divided all patients into two clusters (38 and 40 subjects) which did not differ in all clinical characteristics (except for the preoperative hematocrit, P = 0.038), index S, and all post-surgery HRV indices. First cluster (38 patients) had higher preoperative values of the HR, TP, HF, and HF%, and lower preoperative values of the LF% and LF/HF. Conclusion: The variability of cardiovascular autonomic indices in on-pump cardiac surgery patients (two characteristic clusters were identified based on preoperative indices) was not associated with their clinical characteristics and features of surgical procedure (including cardioplegia).

Severe Cardiac Autonomic Derangement and Altered Ventricular Repolarization Pave the Way to Postoperative Atrial Fibrillation

OBJECTIVE

Postoperative atrial fibrillation (POAF) is a frequent complication after heart surgery. It has been shown that cardiac autonomic derangement plays a significant role in the genesis of atrial fibrillation (AF) and that AF might also be promoted by altered repolarization. Thus, the aim of our study was to determine the levels of cardiac autonomic modulation and repolarization properties in patients developing POAF.

METHODS

Seventy-nine patients scheduled for aortic and/or coronary artery bypass grafting surgery with cardiopulmonary bypass were enrolled prospectively. High-resolution 20-minute electrocardiogram recordings were obtained day before surgery to determine P, PR, QT, and QTc intervals, as well as linear (time and frequency domain) and nonlinear heart rate variability parameters (fractal dimension and detrended fluctuation analysis). QTc interval was calculated using Framingham correction.

RESULTS

Twenty-nine patients developed POAF (AF group), and 50 did not (non-AF group). Groups were similar regarding demographics, surgery type, and perioperative characteristics, except for older age in the AF group. QT and QTc intervals (Framingham) were longer in the AF group [442 (44) vs 422 (28) milliseconds, P = 0.018; and 448 (44) vs 431 (24) milliseconds, P = 0.031 and P = 0.019, respectively]. Time domain heart rate variability parameter PNN50 (percentage of pairs of adjacent NN intervals differing >50 milliseconds) was higher [14% (21%) vs 8% (16%), P = 0.015], and nonlinear parameter detrended fluctuation analysis α2 was lower in the AF group [0.81 (0.21) vs 0.91 (0.20), P = 0.031].

CONCLUSIONS

Profound cardiac autonomic derangement, suggestive of parasympathetic excessive modulation, exists preoperatively in patients inclined to POAF after cardiac surgery, whereby parameters PNN50 and α2 differentiated the AF from the non-AF group. Prolonged QTc intervals are associated with an increased risk of POAF.

Influence of bilevel positive airway pressure on autonomic tone in hospitalized patients with decompensated heart failure

[Purpose] This study evaluated the effect of Bilevel Positive Airway (BiPAP) on the autonomic control of heart rate, assessed by heart rate variability (HRV), in patients hospitalized with decompensated heart failure. [Subjects and Methods] This prospective cross-sectional study included 20 subjects (age: 69±8 years, 12 male, left ventricular ejection fraction: 36 ±8%) diagnosed with heart failure who were admitted to a semi-intensive care unit with acute decompensation. Date was collected for HRV analysis during: 10 minutes spontaneous breathing in the resting supine position; 30 minutes breathing with BiPAP application (inspiratory pressure = 20 cmH2O and expiratory pressure = 10 cmH2O); and 10 minutes immediately after removal of BiPAP, during the return to spontaneous breathing. [Results] Significantly higher values for indices representative of increased parasympathetic activity were found in the time and frequency domains as well as in nonlinear Poincaré analysis during and after BiPAP in comparison to baseline. Linear HRV analysis: standard deviation of the average of all R-R intervals in milliseconds = 30.99±4.4 pre, 40.3±6.2 during, and 53.3±12.5 post BiPAP. Non-linear HRV analysis: standard deviations parallel in milliseconds = 8.31±4.3 pre, 12.9±5.8 during, and 22.8 ±6.3 post BiPAP. [Conclusion] The present findings demonstrate that BiPAP enhances vagal tone in patients with heart failure, which is beneficial for patients suffering from acute decompensation.

Multifractality in heartbeat dynamics in patients undergoing beating-heart myocardial revascularization

BACKGROUND

The multifractal approach of HRV analysis offers new insight into the mechanisms of autonomic modulation of the diseased hearts and has a potential to depict subtle changes in cardiac autonomic nervous control not revealed by conventional linear and non-linear analyses in various conditions like heart failure or stable angina pectoris. The aim of this study was to employ the multifractality approach in cardiac surgery patients and evaluate the multifractality before and after beating-heart myocardial revascularization (off-pump CABG).

METHODS

Twenty-four hour Holter recordings were performed pre- and postoperatively in 60 patients undergoing off-pump CABG. Selected conventional time- and frequency-domain linear HRV indices were calculated from the 24h and 5 min ECG segments, and preselected multifractal parameters τ(q=2), τ(q=3), h_top and Δh were determined for daytime (12:00-18:00) and nighttime (00:00-06:00) periods of the ECG recordings using Ivanov's method. Mean differences over time were tested using paired-samples t-test and exact Wilcoxon matched-pairs test. The results are reported as mean ± SD and median with interquartile range. A p value of <0.05 was considered statistically significant.

RESULTS

All selected conventional linear HRV parameters decreased significantly after off pump CABG (p from <0.001-0.015). Preoperatively, multifractal parameter τ(q=2) was -0.60 ± 0.12 and -0.54 ± 0.12, τ(q=3) -0.52 ± 0.18 and -0.49 ± 0.17, h_top 0.20 ± 0.07 and 0.15 ± 0.07 and Δh 0.31 ± 0.14 and 0.17 ± 0.14 for daytime and nighttime periods, respectively. Postoperatively, τ(q=2) and τ(q=3) were significantly higher for daytime (-0.49 ± 0.15, p<0.001 and -0.43 ± 0.23, p=0.015), whereas h_top and Δh were significantly higher for both daytime and nighttime (0.25 ± 0.07, p<0.001 and 0.19 ± 0.06, p=0.002 for h_top and 0.41 ± 0.20, p=0.003 and 0.31 ± 0.19, p < 0.001 for Δh, respectively). All pre- and postoperative parameters, except τ(q=2) and τ(q=3) preoperatively, were significantly lower for nighttime as compared to daytime periods.

CONCLUSIONS

A significant breakdown of multifractal complexity and anti-correlation behavior with a significant sympathetic overdrive and a concomitant parasympathetic withdrawal occurs after off-pump CABG. The circadian pattern of multifractality regains its day-night variation in the first week after the surgical procedure.