SummaryAnalysis of short-term (5-minute) heart rate variability (HRV) may provide useful information about autonomic nervous control of the cardiovascular system. The aim of the present study was to evaluate the association between the results of treadmill exercise testing (TET) and short-term (5-minute) HRV. Patients undertaking TET were anteriorly evaluated with short-term (5-minute) HRV over time (SDNN, RMSSD, NN50 count, pNN50) and frequency (LF, HF, total power) domains. Among 414 patients, 32 individuals (7.7%; 14 men) had nondiagnostic results. The nondiagnostic group had older age, higher body mass index, more hypertension, lower SDNN, lower LF, and higher HF than the negative group. After adjustment for potential confounders, SDNN (OR 0.94, 95% CI 0.91-0.97; P = 0.01), RMSSD (OR 0.96, 95% CI 0.93-0.99; P = 0.02), NN50 count (OR 0.98, 95% CI 0.97-1.00; P = 0.04) and LF (OR 0.96, 95% CI 0.96-0.99; P = 0.03) were negatively related to nondiagnostic results, and HF showed a positive effect (OR 1.04, 95% CI 1.01-1.05; P = 0.02). No HRV indices were significantly associated with positive results. Our study suggested that cardiac autonomic indices derived from short-term HRV recordings might predict nondiagnostic results of TET. (Int Heart J 2010; 51: 105-110) Key words: Heart rate variability, Treadmill exercise test, Nondiagnostic H eart rate variability (HRV) represents one of the most promising quantitative markers of autonomic activity. 1) HRV in the time and frequency domains is a noninvasive, convenient tool for evaluation of autonomic nervous physiology.2) Time domain analysis estimates the variation of differences between successive RR intervals through indices developed by statistical methods. Frequency domain analysis estimates respiratory-dependent high frequency and low frequency power through spectral analysis. High frequency power is considered to be mediated mainly by vagal activity, while low frequency power has been suggested as predominantly sympathetic modulation.3,4) The most commonly used frequency domains include LF, low frequency power; HF, high frequency power; and total power. Short-term (5-minute) recording is a reliable tool to obtain these HRV measures.
2)Exercise electrocardiography is one of the most frequent noninvasive modalities used to assess patients with suspected or proven cardiovascular disease.5) Meta-analysis of 147 consecutively published studies involving 24,074 patients who underwent both standard exercise testing and coronary angiography revealed a wide variability and modest acceptability in sensitivity and specificity (mean sensitivity was 68%, with a standard deviation of 16%; mean specificity was 77%, with a standard deviation of 17%).
6,7)Although the modest sensitivity of exercise electrocardiography is generally less than the sensitivity of imaging procedures, such as single-photon emission computed tomography imaging of myocardial perfusion and positronemission tomography, 8) exercise testing is still widely available and relatively low-cost. The interpr...