The significance of heart rate turbulence in predicting major cardiovascular events in patients after myocardial infarction treated invasively.

INTRODUCTION: The role of heart rate turbulence (HRT) related to baroreflex sensitivity in predicting mortality after myocardial infarction (MI) has been confirmed by several investigators. However, the significance of HRT in predicting major adverse cardiovascular events (MACE) following acute MI is unknown. PURPOSE: To analyze the prognostic value of HRT and other independent risk factors associated with autonomic regulation of MACE. METHODS: HRT was assessed based on 24-hour Holter recordings in 500 patients (pts) with acute MI treated invasively (352 M, aged 60.58 years). Turbulence onset (TO,%), slope (TS, ms/RR interval) and timing (TT) were calculated. TO ≥ 0, TS ≤ 2.5 and TT ≥ 10 were considered abnormal; classic and own categories were defined. Time domain heart rate variability (HRV) parameters were also calculated. Within 30.1 ± 15.1 months of follow-up, MACE occurred in 116 pts. RESULTS: Abnormal TO, TS, and TT were significantly more frequent in patients with MACE (P < 0.05 for each parameter, classic and own categories). In long-term follow-up, the largest differences in MACE were observed in patients with own category comprising abnormal TO, TS, and TT. Combining HRT parameters with SDNN (total HRV index) augmented their predictive value. Independent risk factors for MACE were TT, SDNN and rMSSD (a parasympathetic activity index) (HR 2.44, 1.71 and 1.69 respectively; P < 0.05). CONCLUSION: Abnormal HRT distinguishes patients at risk of MACE after MI. Own category encompassing three abnormal HRT parameters best differentiates patients at risk of MACE. Turbulence timing is a strong independent risk factor for MACE following MI.

Heart rate turbulence for prediction of heart transplantation and mortality in chronic heart failure.

BACKGROUND: Previous studies have shown conflicting results about the value of heart rate turbulence (HRT) for risk stratification of patients (pts) with chronic heart failure (CHF). We prospectively evaluated the relation between HRT and progression toward end-stage heart failure or all-cause mortality in patients with CHF. METHODS: HRT was assessed from 24-hour Holter recordings in 110 pts with CHF (54 in NYHA class II, 56 in class III-IV; left ventricular ejection fraction (LVEF) 30%+/- 10%) on optimal pharmacotherapy and quantified as turbulence onset (TO,%), turbulence slope (TS, ms/RR interval), and turbulence timing (beginning of RR sequence for calculation of TS, TT). TO > or = 0%, TS < or = 2.5 ms/RR, and TT >10 were considered abnormal. End point was development of end-stage CHF requiring heart transplantation (OHT) or all-cause mortality. RESULTS: During a follow-up of 5.8 +/- 1.3 years, 24 pts died and 10 required OHT. TO, TS, TT, and both (TO and TS) were abnormal in 35%, 50%, 30%, and 25% of all patients, respectively. Patients with at least one relatively preserved HRT parameter (TO, TS, or TT) (n = 98) had 5-year event-free rate of 83% compared to 33% of those in whom all three parameters were abnormal (n = 12). In multivariate Cox regression analysis, the most powerful predictor of end point events was heart rate variability (SDNN < 70 ms, hazard ratio (HR) 9.41, P < 0.001), followed by LVEF < or = 35% (HR 6.23), TT > or = 10 (HR 3.14), and TO > or = 0 (HR 2.54, P < 0.05). CONCLUSION: In patients with CHF on optimal pharmacotherapy, HRT can help to predict those at risk for progression toward OHT or death of all causes.

Sleep apnoea as a predictor of mid- and long-term outcome in patients undergoing cardiac resynchronization therapy.

AIMS: To assess the impact of baseline apnoea-hypopnoea index (AHI) on mid-term outcome and its change after 6 months of cardiac resynchronization therapy (CRT) on remote outcome. METHODS AND RESULTS: In 71 patients with CRT devices, Holter-derived AHI was assessed before and 6 months after the procedure. Baseline AHI >20 was considered abnormal. After 6 months of CRT, a 50% decrease of baseline AHI was considered significant and stratified patients into AHI dippers and non-dippers, except those who preserved normal AHI. Prognostic value of baseline AHI and its change were assessed in relation to mortality and major cardiac events (MACE). More patients with an abnormal AHI died during 6 months follow-up (P = 0.02), especially due to sudden cardiac death. MACE-rate was insignificantly higher in abnormal AHI patients. Significantly higher mortality (P = 0.001), especially due to heart failure progression and higher MACE-rate (P < 0.001) during further observation were observed in AHI non-dippers. In multivariate analysis, the absence of AHI reduction was an independent predictor of mortality [hazard ratio (HR) 6.56, P = 0.015)] and MACE (HR 6.05, P = 0.002). CONCLUSIONS: Abnormal baseline AHI identifies patients prone to death during mid-term observation. Lack of AHI reduction after 6 months of CRT is an independent risk factor of death and MACE during further follow-up.

Effects of cardiac resynchronization therapy on heart rate turbulence.

BACKGROUND: Cardiac resynchronization therapy (CRT) improves the clinical status of patients with heart failure (HF), though its effects on heart rate turbulence (HRT) are unknown. METHODS: We measured HRT indices in 58 recipients of CRT systems (mean age = 56 +/- 9 years, 41 men) in New York Heart Association HF functional class III-IV, and with a left ventricular (LV) ejection fraction < or =35%. At 6 months of follow-up, 42 patients were responders and 13 nonresponders to CRT, and three patients died suddenly. The HRT indices turbulence onset (TO%) and turbulence slope (TS ms/RR interval) were calculated from digital 24-hour electrocardiogram before and after 6 months of CRT. TO > or = 0% and TS < or = 2.5 ms/RR interval were considered abnormal. RESULTS: Mean TO in the entire population was 0.4 +/- 1.5 before CRT, and decreased to -0.8 +/- 7.0 during the 6 months of CRT (ns). TS increased significantly from 2.0 +/- 1.7 at baseline, to 3.9 +/- 3.1 (P < 0.05), and a significantly lower proportion of patients had abnormal HRT indices at 6 months. In contrast to the significant increase observed in responders, not significant change in TS was observed among the nonresponders. CONCLUSIONS: During 6 months of CRT, improvements in HRT indices and a decrease in the proportion of patients with abnormal HRT were observed. CRT may have beneficial effects on baroreflex sensitivity.

Gender-dependent profile of heart rate turbulence parameters in patients after acute myocardial infarction treated invasively.

BACKGROUND AND AIM: The aim of this study was to determine whether gender is related to differences in heart rate turbulence (HRT) parameters and the authors' own predefined HRT categories comprising turbulence timing (TT) in patients at the early stage of acute myocardial infarction (AMI) treated invasively. METHODS: We analysed 489 consecutive patients (147 females and 342 males, aged 63.9 ± 11.7 years) with AMI admitted to our department and treated invasively on admission to the hospital. On the fifth day after MI 24-h digital Holter recordings were performed to assess HRT, and the following HRT parameters were calculated in all patients using the HRTView pro-gram: turbulence onset (TO, %), slope (TS, ms/RR interval), and TT. The following values of HRT parameters were considered abnormal: TO ≥ 0, TS ≤ 2.5, and TT ≥ 10. Based on the abovementioned parameters, the authors defined their own HRT categories (A, B, C): A - comprising three normal parameters, B - one abnormal parameter, C - three abnormal parameters. RESULTS: TT was significantly later in women than in men: 7.5 ± 3.1 vs. 6.8 ± 3.1 (p < 0.05), respectively. When analysing the authors' own predefined HRT categories, significant differences between women and men were present in the occurrence of the category C, including all three abnormal HRT parameters: TO, TS, and TT. CONCLUSIONS: In women worse TT was present and all three abnormal HRT parameters occurred more frequently. HRT in women after AMI is profoundly altered compared to in men. This indicates greater autonomic dysfunction and higher risk for sudden cardiac death in women after AMI.

Fragmentation of the QRS complex in patients with acute coronary syndrome treated invasively.

BACKGROUND: Previous studies showed that the presence of fragmented QRS (f-QRS) in patients with acute coronary syndrome (ACS), who underwent complete revascularisation, is associated with worse prognosis and the possibility of arrhythmia occurrence. AIM: To assess the prognostic value of f-QRS in patients with ACS and complete revascularisation, in the context of cardiac ar-rhythmias. METHODS: We analysed 124 consecutive patients (66.1% males; mean age 62.38 ± 11.0 years) with ACS (STEMI 49%) treated invasively. Based on electrocardiogram (ECG) record, performed during the admission to the clinic, after the complete revascularisation (TIMI = 3) and during discharging from hospital (4th-5th days after ACS), we classified QRS as f-QRS based on generally accepted criteria (QRS < 120 ms, which included an additional R wave [R']) or notching in the nadir of the S wave, or > 1 R' (fragmentation) in two contiguous leads, corresponding to a major coronary artery territory. 24-h Holter ECG recording was performed on the fifth day after ACS to assess the frequency of conduction disturbances and others arrhythmias. RESULTS: There were no statistically significant differences between patients with and without f-QRS during hospitalisation. In the patients with f-QRS there were no statistically significant conduction disturbances and other arrhythmias compared to patients without f-QRS at discharge. CONCLUSIONS: In the patients with ACS, who underwent successful revascularisation (TIMI = 3), the presence of f-QRS is not correlated with a higher incidence of arrhythmias compared to patients without f-QRS in short-term follow-up.

Microvolt T-wave alternans and other noninvasive predictors of serious arrhythmic events in patients with an implanted cardioverter-defibrillator.

BACKGROUND: Prediction of recurrent malignant ventricular tachyarrhythmias after insertion of a implantable cardioverter-defibrillator (ICD) is challenging. Microvolt T-wave alternans (MTWA) seems to be a promising marker of such events in ICD recipients. AIM: To assess prognostic significance of MTWA and other noninvasive parameters in the prediction of major arrhythmic events after ICD implantation. METHODS: This prospective study included 155 patients (121 male, age 59 ± 11 years) in whom ICD was implanted for secondary prevention of a sudden cardiac death. In all patients, clinical evaluation along with estimation of ejection fraction, MTWA measurement using the HearTwave Cambridge Heart system, and determination of the corrected QT interval (QTc) and QT dispersion (QTd) based on resting ECG were performed 3 days before ICD implantation. Using 24-h Holter monitoring, cardiac arrhythmias, QT interval, QT dynamicity, QT variability (QTSD) and heart rate variability (HRV) time domain parameters were determined. MTWA results were categorised, based on the accepted criteria, as positive, negative or indeterminate. In further analyses, positive and indeterminate MTWA results were grouped together as abnormal or non-negative tests [MTWA+], while negative MTWA results were considered normal [MTWA-]. During the follow-up (mean duration 21.6 ± 11.6 months), major arrhythmic cardiac events (MACE), defined as death and/or the need for ablation and/or heart transplantation due to malignant ventricular tachyarrhythmias, were recorded. RESULTS: During the follow-up, MACE occurred in 17 (11%) patients. Abnormal MTWA before ICD implantation was found significantly more frequently in patients with MACE as compared to patients without MACE. Multivariate Cox regression analysis identified abnormal MTWA and QTSD as independent risk factors for MACE, with hazard ratios of 10.82 (95% CI 9.76-11.88; p〈 0.05) and 1.08 (95% CI 1.05-1.08), respectively. Significant differences in MACE-free survival rate with regard to MTWA results (abnormal vs normal MTWA) were shown during the follow-up (p〈 0.001). The negative predictive value of normal MTWA for MACE was 98.6%. When both MTWA and QTSD were combined, the positive predictive value increased to 35%, with a sensitivity of 82% and specificity of 81%. The probability of MACE with normal results of both these tests was 2.3%. CONCLUSIONS: Abnormal MTWA is a strong independent predictor of MACE in ICD recipients, and QTSD is a weaker predictor. In the prediction of MACE after ICD implantation, the highest predictive value was noted for abnormal MTWA combined with QTSD. Normal values of these two parameters were associated with a low probability of MACE. These results suggest that standardised MTWA evaluation can be useful for risk stratification in the clinical practice.