Reproducibility of methods for assessing baroreflex sensitivity and temporal QT variability in end-stage renal disease and healthy subjects

Abstract

Spontaneous baroreflex sensitivity (BRS), the reflex heart rate modulation in response to blood pressure changes (predominantly an index of cardiac vagal activity) and temporal QT variability (an index of myocardial repolarization) have been demonstrated to convey important prognostic information. The information about reproducibility of BRS and temporal QT variability is limited and there is lack of information regarding patients with cardiovascular diseases. We investigated reproducibility of spontaneous BRS using the sequence technique and temporal QT variability index (QTVI) in terms of intra-, interexaminer and within-subject variability in end-stage renal disease patients (ESRD, n=17, age 55+/-14 years) and healthy subjects (HS, n=29, age 32+/-12 years, P<0.01). ECG and blood pressure (Portapres) were recorded on two separate days and BRS and QTVI were evaluated by two independent examiners. The mean heart rate was similar in ESRD patients in comparison to healthy controls, whereas the mean arterial pressure was 13 % higher in ESRD patients (P<0.01). Spontaneous BRS was 62% lower (P<0.01) and QTVI was 41% higher in ESRD patients (P<0.01) compared to healthy subjects, respectively. Coefficient of variation (CV) of within-subject reproducibility of BRS and QTVI measurements was moderate (BRS: 33 % for ESRD, 27% for HS; QTVI: 40% for ESRD, 18% for HS). The 95% limit of within-subject reproducibility of BRS measurements was 3.8 ms/mm Hg for ESRD patients and 8.1 ms/mm Hg for healthy subjects; whereas the 95% limit of reproducibility of within-subject reproducibility of QTVI measurements was 0.73 for ESRD patients and 0.55 for healthy subjects. Concordance correlation coefficients of within-subject variability of BRS and QTVI were between 0.74 and 0.83 in both groups. CV of intra- and inter-examiner reproducibility of BRS and QTVI measurements in both groups ranged between 1 and 11%. In conclusion, the intra- and inter-examiner reproducibility/agreement of BRS and QTVI were high, whereas the within-subject reproducibility of these two methods was moderate, in both ESRD patients and healthy subjects. Thus, small differences in BRS and QTVI in longitudinal/interventional studies should be interpreted with caution.

Baroreflex sensitivity measured by spectral and sequence analysis in cerebrovascular disease

“…However, in patient groups with known impairment of the baroreflex such as heart failure and end stage renal failure, BRS derived by both the sequence and the spectral methods have been shown to be less reproducible than has been demonstrated in studies of healthy individuals [7,11]. Patients with cerebrovascular disease have BRS values similar to these subjects and thus the measurement of BRS may not be as reproducible as predicted by the studies in healthy individuals.…”

“…This difference in methodology may explain the poor reproducibility seen by Davies et al Indeed, when we assessed our reproduc- Spectral analysis is presented as total power (Spectral BRS) and its low frequency (LF) and high frequency (HF) components, sequence analysis is presented as all sequences and its up sequence and low sequence components ibility using just a single 5-minute recording at each visit, we found the method to be much less reproducible with CVs of 35.7% for spectral and 42.4% for sequence analysis. Gao et al [11] assessed the reproducibility of BRS by sequence analysis in subjects with end-stage renal disease at two visits at a mean of 7 days apart. They found reproducibility in this patient group to be almost as good as for their healthy control group (CV 33% cf 27%), and similar to those described in stroke patients in the current study.…”

Assesment of Autonomic Function in Slow Coronary Flow using Heart Rate Variability and Heart Rate Turbulence

“…Increased sympathetic or decreased parasympathetic nervous system activity predisposes patients with Coronary Heart Disease (CHD) to ventricular tachycardia, ventricular fibrillation, sudden cardiac death [9,10] and increased mortality [11]. Decreased vagal activity and increased sympathetic activity, both of which are risk factors predicting death was found in both healthy adults and adults with exit cardiovascular disease [22][23][24][25][26][27]. Heart Rate Turbulence (HRT) and Heart Rate Variability (HRV) are a comprehensive evaluation of cardiac autonomic reflexes [13].…”

Real-time multichannel system for beat-to-beat QT interval variability

“…First, most if not all require that the operator actively perform certain functions, for example that he or she manually choose the onset and offset of an initial QT interval template. This step of human intervention is both time and labor consuming, and affects reproducibility (12). Second, the majority of these existing programs also allow for QTV analyses in only one single channel at a time (i.e., usually in limb lead II or limb lead I), and not in multiple channels simultaneously.…”