Reduced diurnal variation of heart rate is associated with increased plasma B-type natriuretic peptide level in patients with atrial fibrillation.

BACKGROUND: The plasma B-type natriuretic peptide (BNP) level has been shown to be increased in patients with chronic atrial fibrillation (AF) independent of left ventricular ejection fraction (LVEF). The purpose of this study is to evaluate the relationship between the plasma BNP level and heart rate variation in patients with AF. HYPOTHESIS: The plasma BNP level is associated with heart rate variation in patients with AF. METHODS: A total of 102 patients with AF and preserved LVEF were included from 2 hospitals. The ambulatory electrocardiographic recording and measurement of plasma BNP levels were performed simultaneously. Echo-Doppler parameters were measured as the average of 10 consecutive cardiac cycles. RESULTS: A difference in the mean heart rate between night and day (DIFF) and the standard deviation of the 5-miniute mean R-R interval (SDARR) were significantly associated with log-transformed BNP levels (r = -0.411, P < 0.001 and r = -0.243, P = 0.049, respectively). In echocardiography, the ratio of E velocity to early diastolic velocity, which reflects left ventricular (LV) filling pressure, was significantly correlated with the DIFF and SDARR, along with the log-transformed BNP level. Stepwise multiple linear regression analysis revealed that the DIFF and age were independent factors related with the BNP level (P < 0.01). CONCLUSIONS: The reduced diurnal variation of heart rate was significantly associated with increased BNP, which is linked to LV diastolic dysfunction in patients with AF.

Intermittent arm ischemia induces vasodilatation of the contralateral upper limb.

Intermittent arm ischemia before percutaneous coronary intervention induces remote ischemic preconditioning (RIPC) and attenuates myocardial injury in patients with myocardial infarction. Several studies have shown that intermittent arm ischemia increases coronary flow and is related to autonomic nerve system. The aim of this study was to determine whether intermittent arm ischemia induces vasodilatation of other arteries and to assess changes in the autonomic nerve system during intermittent arm ischemia in humans. We measured change in the right brachial artery diameter during intermittent left arm ischemia through three cycles of 5-min inflation (200 mmHg) and 5-min deflation of a blood-pressure cuff using a 10-MHz linear array transducer probe in 20 healthy volunteers. We simultaneously performed power spectral analysis of heart rate. Ischemia-reperfusion of the left arm significantly dilated the right brachial artery time-dependently, resulting in a 3.2 ± 0.4% increase after the 3rd cycle. In the power spectral analysis of heart rate, the high-frequency domain (HF), which is a marker of parasympathetic activity, was significantly higher after the 3rd cycle of ischemia-reperfusion than baseline HF (P = 0.02). Intermittent arm ischemia was accompanied by vasodilatation of another artery and enhancement of parasympathetic activity. Those effects may play an important role in the mechanism of RIPC.

Abnormal transmural repolarization process in patients with Brugada syndrome.

BACKGROUND: Repolarization abnormality, especially during bradycardia, might be critical for initiation of ventricular fibrillation (VF) in patients with Brugada syndrome (BrS), but the contribution of the rate-dependent repolarization dynamics to the occurrence of VF is still unknown. OBJECTIVE: The aim of our study was to determine the differences in rate-dependent repolarization dynamics between BrS with and without spontaneous VF and between BrS with and without SCN5A mutation. METHODS: The subjects were 37 BrS patients with VF (VF(+) group: 10 male subjects) and without VF (VF(-) group: 27 male subjects) and 20 control subjects. Genetic analysis of SCN5A was performed in all 37 BrS patients. The relationships between QT, QTp, Tp-e, and RR intervals were obtained from Holter recordings as first linear regression lines, and the slopes of QT/RR, QTp/RR, and Tp-e/RR linear regression lines as the sensitivity of rate-dependent repolarization dynamics were compared. RESULTS: QT/RR and Tp-e/RR slopes showed loss of a rate-dependent property in the VF(+) group compared with those in the VF(-) and control groups. There was no significant difference in QTp/RR slope among the VF(+), VF(-) and control groups. The Tp-e interval had a negative correlation with the RR interval in the VF(+) group and a positive correlation with the RR interval in the VF(-) and control groups. There was no significant difference in QT/RR, QTp/RR, and Tp-e/RR slopes between BrS patients with SCN5A mutation and those without SCN5A mutation. CONCLUSIONS: Loss of rate-dependent QT dynamics may be associated with occurrence of VF in BrS.

Nicorandil reduces the incidence of minor cardiac marker elevation after coronary stenting.

BACKGROUND: Minor cardiac marker elevation after percutaneous coronary intervention has long-term prognostic significance. We examined whether nicorandil, a nicotinamide-nitrate ester, reduces the incidence of minor cardiac marker elevation after coronary stenting. METHODS: Patients (n=192) undergoing coronary stenting were randomly assigned to receive nicorandil (nicorandil group, n=91) or vehicle (control group, n=101). Nicorandil (2 mug/kg/min, intravenously) was administered immediately after the patients were transferred into the catheterization laboratory and continued for 6 h. We measured the serum concentrations of creatine kinase isoenzyme MB (CK-MB) before, immediately after, and 6, 12, and 24 h after the procedure, and those of cardiac troponin T (cTnT) 24 h after the procedure. RESULTS: There was no significant difference in clinical background between the 2 groups. The nicorandil group showed a significantly lower incidence of CK-MB elevation (>1x upper limit of control range, 20 IU/l) than the control group (8.8% vs 21.8%, p<0.05). The levels of serum CK-MB in the nicorandil group were significantly lower than those in the control group (13.4+/-5.7 vs 16.5+/-9.7 IU/l, p<0.01). Similarly, the nicorandil group showed a significantly lower incidence of cTnT elevation [>1x (0.1 ng/ml) or >2x (0.2 ng/ml)] upper limit of control range than the control group (14.3% vs 26.7%, p<0.05, or 7.7% vs 17.8%, p<0.05). Serum cTnT levels were also significantly lower in the nicorandil group than in the control group (0.05+/-0.10 vs 0.15+/-0.36 ng/ml, p<0.05). CONCLUSIONS: The results demonstrated that nicorandil reduces minor cardiac marker elevation after coronary stenting.

Intense response of heart rate with pronounced suppression of high-frequency power of heart rate variability to early morning exercise with high-intensity load.

Autonomic nerve activity shows circadian variation. Therefore, we put forward the hypothesis that the responses of heart rate (HR) and high-frequency (HF) power of HR variability to exercise would be different between early morning and daytime exercise. We performed ergometer constant load exercise tests [50 watts (low), 100 watts (high load)] in the early morning and during the day in 6 healthy volunteers. The HR response was fitted to an exponential hyperbolic sine function: HR= alpha*e(-beta*t) *sinh(omega*t)+gamma. In this equation, the beta/omega ratio was inversely correlated with the intensity of the HR response. HF power was determined using a recently developed algorithm with high time-resolution power. There were no significant differences in HR, HF power or systolic blood pressure (BP) pressure before exercise between early morning and daytime exercise with either the 50 or 100 watt loads. During exercise, there were no significant differences in maximal HR or maximal systolic BP between early morning and daytime exercise with either 50 or 100 watt loads. For high-load exercise, the beta/omega ratio was significantly lower in early morning exercise (mean +/- SD, 0.945 +/- 0.02) than in daytime exercise (0.987 +/- 0.03). Similarly, for 100 watt exercise, HF power of HR variability was significantly lower in early morning exercise (0.94 +/- 0.52 msec/Hz 1/2) than in daytime exercise (1.26 +/- 0.74 msec/Hz 1/2). In conclusion, the present study demonstrated that a lower beta/omega ratio in the HR response was associated with lower HF power of HR variability in early morning high-load exercise compared to that in daytime exercise, indicating that the heart rate responded more intensely to early morning exercise than to daytime exercise with a high load due, at least partly, to pronounced suppression of parasympathetic nerve activity.