Multi-scale heart rate dynamics detected by phase-rectified signal averaging predicts mortality after acute myocardial infarction.

AIMS: Acceleration and deceleration capacity (AC and DC) for beat-to-beat short-term heart rate dynamics are powerful predictors of mortality after acute myocardial infarction (AMI). We examined if AC and DC for minute-order long-term heart rate dynamics also have independent predictive value. METHODS AND RESULTS: We studied 24-hr Holter electrcardiograms in 708 post-AMI patients who were followed up for up to 30 months thereafter. Acceleration capacity and DC was calculated with the time scales of T (window size defining heart rate) and s (wavelet scale) from 1 to 500 s and compared their prognostic values with conventional measures (AC(conv) and DC(conv)) that were calculated with (T,s) = [1,2 (beat)]. During the follow-up, 47 patients died. Both increased AC(conv) and decreased DC(conv) predicted mortality (C statistic, 0.792 and 0.797). Concordantly, sharp peaks of C statistics were observed at (T,s) = [2,7 (sec)] for both increased AC and decreased DC (0.762 and 0.768), but there were larger peaks of C statistics at around [30,60 (sec)] for both (0.783 and 0.796). The C statistic was greater for DC than AC at (30,60) (P = 0.0012). Deceleration capacity at (30,60) was a significant predictor even after adjusted for AC(conv) (P = 0.020) and DC(conv) (P = 0.028), but the predictive power of AC at (30,60) was no longer significant. CONCLUSION: A decrease in DC for minute-order long-term heart rate dynamics is a strong predictor for post-AMI mortality and the predictive power is independent of AC(conv) and DC(conv) for beat-to-beat short-term heart rate dynamics.

Reactivation of immune responses against Mycobacterium tuberculosis by boosting with the CpG oligomer in aged mice primarily vaccinated with Mycobacterium bovis BCG.

BACKGROUND: Mycobacterium bovis bacillus Calmette Guérin (BCG) vaccine, which has been inoculated to more than one billion people world-wide, has significant effect in preventing tuberculous meningitis and miliary tuberculosis (TB) in neonate and early childhood. However, BCG fails to adequately protect against pulmonary TB and reactivation of latent infections in adults. To overcome this problem, adequate booster is urgently desired in adult who received prior BCG vaccination, and appropriate animal models that substitute human cases would be highly valuable for further experimentation. FINDINGS: The booster effect of the synthesized CpG oligomer (Oligo-B) on aged mice which had been primarily vaccinated with BCG at the age of 4-week old. The specific Th1 type reaction, production of interferon-γ, in response to TB antigens, purified protein derivatives (PPD) and protection against challenge with Mycobacterium tuberculosis (MTB) H37Rv decreased with increasing age and were not observed in 89-week old mice. In order to rejuvenate the Th1 type response against PPD and protection activity against MTB infection, Oligo-B, which is known to augment Th1 responses, was administered as a booster to 81-90-week old mice (late 50's in human equivalent) vaccinated with BCG at 4-week old. The boosting with Oligo-B increased the number of CD4+ CD44high CD62Lhigh, central memory type T cell. Furthermore, the Oligo-B boosting rejuvenated the ability of mice to protect against infection with MTB H37Rv. CONCLUSIONS: Th1-adjuvant CpG oligo DNA, such as Oligo-B, may be a promising booster when coupled with BCG priming.

Cardiac ß-adrenergic receptor density and myocardial systolic function in the remote noninfarcted region after prior myocardial infarction with left ventricular remodelling.

PURPOSE: After myocardial infarction (MI), left ventricular (LV) remodelling is observed in noninfarcted LV myocardium. LV remodelling is closely associated with systolic heart failure. Since myocardial dysfunction is related to the downregulation of cardiac postsynaptic beta-adrenergic receptors (ß-AR), we hypothesized that a reduction in ß-AR density may be manifested in the remote noninfarcted region and such reduction may be related to myocardial systolic dysfunction. Accordingly, we assessed ß-AR density with a focus on the remote noninfarcted region. METHODS: Cardiac PET was performed in 15 patients with a prior MI and 10 age-matched healthy controls using (11)C-CGP 12177, a radioligand for ß-receptors. The maximum number of available specific (11)C-CGP 12177 binding sites per gram of tissue was calculated in regions of interest using an established graphical method. LV regional systolic function was assessed based on peak systolic myocardial strain on the LV wall in the longitudinal direction using two-dimensional ultrasound speckle tracking imaging. LV volumes and LV ejection fraction (EF) were also measured. RESULTS: The LV end-diastolic volume index was significantly larger in patients than in controls (67.8 ± 16.9 vs. 49.1 ± 12.3 ml/m(2), p < 0.01). Significant differences in ß-AR density were observed among three areas: the apical area in controls (where the lowest ß-AR density was observed), the remote noninfarcted region of patients and LVEF ≥ 55 %, and the remote noninfarcted region of patients and LVEF <55 % (5.8 ± 2.1 vs. 4.2 ± 0.7 vs. 3.3 ± 0.7 pmol/ml, p < 0.01, ANOVA). Peak systolic myocardial strain was significantly reduced in the remote noninfarcted LV wall in patients with a prior anterior wall MI compared with that in the corresponding wall in controls (-15.5 ± 2.5 vs. -20.1 ± 2.2 %, p < 0.001). A similar finding was also observed in patients with a prior inferior wall MI. CONCLUSION: In the remote noninfarcted region in patients, ß-AR downregulation was observed, which was related to deterioration of local myocardial systolic function.

Nonlinear measures of heart rate variability and mortality risk in hemodialysis patients.

BACKGROUND AND OBJECTIVES: Nonlinear measures of heart rate variability (HRV) have gained recent interest as powerful risk predictors in various clinical settings. This study examined whether they improve risk stratification in hemodialysis patients. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: To assess heart rate turbulence, deceleration capacity, fractal scaling exponent (α(1)), and other conventional HRV measures, 281 hemodialysis patients underwent 24-hour electrocardiography between January 2002 and May 2004 and were subsequently followed up. RESULTS: During a median 87-month follow-up, 77 patients (27%) died. Age, left ventricular ejection fraction, serum albumin, C-reactive protein, and calcium × phosphate independently predicted mortality. Whereas all nonlinear HRV measures predicted mortality, only decreased scaling exponent α(1) remained significant after adjusting for clinical risk factors (hazard ratio per a 0.25 decrement, 1.46; 95% confidence interval [95% CI], 1.16-1.85). The inclusion of α(1) into a prediction model composed of clinical risk factors increased the C statistic from 0.84 to 0.87 (P=0.03), with 50.8% (95% CI, 20.2-83.7) continuous net reclassification improvement for 5-year mortality. The predictive power of α(1) showed an interaction with age (P=0.02) and was particularly strong in patients aged <70 years (n=208; hazard ratio, 1.87; 95% CI, 1.38-2.53), among whom α(1) increased the C statistic from 0.85 to 0.89 (P=0.01), with a 93.1% (95% CI, 59.3-142.0) continuous net reclassification improvement. CONCLUSIONS: Scaling exponent α(1) that reflects fractal organization of short-term HRV improves risk stratification for mortality when added to the prediction model by conventional risk factors in hemodialysis patients, particularly those aged <70 years.