The effects of heart rate control in chronic heart failure with reduced ejection fraction

Metabolomics analysis reveals the effects of Salvia Miltiorrhiza Bunge extract on ameliorating acute myocardial ischemia in rats induced by isoproterenol

Salvia miltiorrhiza Bunge (SM) is a widespread herbal therapy for myocardial ischemia (MI). Nevertheless, the therapeutic signaling networks of SM extract on MI is yet unknown. Emerging evidences suggested that alterations in cardiac metabolite influences host metabolism and accelerates MI progression. Herein, we employed an isoproterenol (ISO)-induced acute myocardial ischemia (AMI) rat model to confirm the pharmacological effects of SM extract (0.8, 0.9, 1.8 g/kg/day) via assessment of the histopathological alterations that occur within the heart tissue and associated cytokines; we also examined the underlying SM extract-mediated signaling networks using untargeted metabolomics. The results indicated that 25 compounds with a relative content higher than 1 % in SM aqueous extract were identified using LC-MS/MS analysis, which included salvianolic acid B, lithospermic acid, salvianolic acid A, and caffeic acid as main components. An in vivo experiment showed that pretreatment with SM extract attenuated ISO-induced myocardial injury, shown as decreased myocardial ischemic size, transformed electrocardiographic, histopathological, and serum biochemical aberrations, reduced levels of proinflammatory cytokines, inhibited oxidative stress (OS), and reversed the trepidations of the cardiac tissue metabolic profiles. Metabolomics analysis shows that the levels of 24 differential metabolites (DMs) approached the same value as controls after SM extract therapy, which were primarily involved in histidine; alanine, aspartate, and glutamate; glycerophospholipid; and glycine, serine, and threonine metabolisms through metabolic pathway analysis. Correlation analysis demonstrated that the levels of modulatory effects of SM extract on the inflammation and OS were related to alterations in endogenous metabolites. Overall, SM extract demonstrated significant cardioprotective effects in an ISO-induced AMI rat model, alleviating myocardial injury, inflammation and oxidative stress, with metabolomics analysis indicating potential therapeutic pathways for myocardial ischemia.

Improved Efficiency of Intraventricular Blood Flow Transit Under Cardiac Stress: A 4D Flow Dobutamine CMR Study

Introduction: The effects of heart rate, inotropy, and lusitropy on multidimensional flow patterns and energetics within the human heart remain undefined. Recently, reduced volume and end-diastolic kinetic energy (KE) of the portion of left ventricular (LV) inflow passing directly to outflow, Direct flow (DF), have been shown to reflect inefficient LV pumping and to be a marker of LV dysfunction in heart failure patients. In this study, we hypothesized that increasing heart rate, inotropy, and lusitropy would result in an increased efficiency of intraventricular blood flow transit. Therefore, we sought to investigate LV 4D blood flow patterns and energetics with dobutamine infusion.

Methods: 4D flow and morphological cardiovascular magnetic resonance (CMR) data were acquired in twelve healthy subjects: at rest and with dobutamine infusion to achieve a target heart rate ~60% higher than the resting heart rate. A previously validated method was used for flow analysis: pathlines were emitted from the end-diastolic (ED) LV blood volume and traced forward and backward in time to separate four functional LV flow components. For each flow component, KE/mL blood volume at ED was calculated.

Results: With dobutamine infusion there was an increase in heart rate (64%, p < 0.001), systolic blood pressure (p = 0.02) and stroke volume (p = 0.01). Of the 4D flow parameters, the most efficient flow component (DF), increased its proportion of EDV (p < 0.001). The EDV proportion of Residual volume, the blood residing in the ventricle over at least two cardiac cycles, decreased (p < 0.001). The KE/mL at ED for all flow components increased (p < 0.001). DF had the largest absolute and relative increase while Residual volume had the smallest absolute and relative increase.

Conclusions: This study demonstrates that it is feasible to compare 4D flow patterns within the normal human heart at rest and with stress. At higher heart rate, inotropy and lusitropy, elicited by dobutamine infusion, the efficiency of intraventricular blood flow transit improves, as quantified by an increased relative volume and pre-systolic KE of the most efficient DF component of the LV volume. The change in these markers may allow a novel assessment of LV function and LV dysfunction over a range of stress.

Association of Heart Rate Trajectory Patterns with the Risk of Adverse Outcomes for Acute Heart Failure in a Heart Failure Cohort in Taiwan

BACKGROUND

Heart rate trajectory with multiple heart rate measurements is considered to be a more sensitive predictor of outcomes than single heart rate measurements. The association of heart rate trajectory patterns with acute heart failure outcomes has not been well studied. We examined the association of heart rate trajectory patterns with post-discharge outcomes.

METHODS

This prospective cohort study was based on an acute heart failure registry in Taiwan. A total of 1509 patients were enrolled in the Taiwan Society of Cardiology - Heart Failure with Reduced Ejection Fraction Registry from May 2013 to October 2015. The outcomes were post-discharge all-cause mortality and heart failure re-admission.

RESULTS

Two heart trajectory patterns were identified in group-based trajectory analysis. One started with a higher heart rate and had an increasing trend over 6 months then a subsequent decline (high-increasing-decreasing group; n = 352; 23.9%). The other started with a lower heart rate and had a relatively stable pattern (low-stable group; n = 1121; 76.1%). Compared with those in the low-stable group, patients in the high-increasing-decreasing group had a higher risk of events (all-cause mortality: hazard ratio 3.10 and 95% confidence interval 1.24-7.77; heart failure re-admission: hazard ratio 1.13 and 95% confidence interval 0.55-2.32).

CONCLUSIONS

Patients with a high-increasing-decreasing heart rate trajectory pattern had a higher risk of all-cause mortality than those with a low-stable pattern.

Particulate Matter 2.5 Induced Developmental Cardiotoxicity in Chicken Embryo and Hatchling

Particulate matter poses health risk to developing organisms. To investigate particulate matters with a diameter smaller than 2.5 um (PM2.5)-induced developmental cardiotoxicity, fertile chicken eggs were exposed to PM2.5 via air cell injection at doses of 0.05, 0.2, 0.5, 2, and 5 mg/egg kg. Morphological changes in the embryonic day four (ED4) and hatchling hearts were assessed with histological techniques. Heart rates of hatchling chickens were measured with electrocardiography. The protein expression levels of nuclear factor kappa-light-chain-enhancer of activated B cells p65 (NF-kb p65), inducible nitric oxide synthase (iNOS), and matrix metallopeptidase 9 (MMP9) were assessed with immunohistochemistry or western blotting in hatchling hearts. PM2.5 exposure elevated areas of heart in ED4 embryo, increased heart rate, and thickened right ventricular wall thickness in hatchling chickens. Immunohistochemistry revealed enhanced NF-kb p65 expression in hatchling hearts. Western blotting results indicated that both iNOS and MMP9 expression were enhanced by lower doses of PM2.5 exposure (0.2 and 0.5 mg/kg) but not 2 mg/kg. In summary, developmental exposure to PM2.5 induced developmental cardiotoxicity in chicken embryo and hatchling chickens, which is associated with NF-kb p65, iNOS, and MMP9.

Independent Influence of Blood Pressure on QTc Interval: Results from a General Chinese Population

Aims

We performed the current study primarily to characterize the independent association of blood pressure with heart rate-corrected QT (QTc) interval after adjusting for cardiovascular confounding factors and left ventricular mass (LVM) in a large general population in China.

Methods

All enrolled 10,553 permanent residents with age ≥ 35 years from Liaoning Province were investigated by a questionnaire and then subjected to physical examinations, laboratory analyses, and electrocardiogram (ECG) as well as echocardiogram at the same visit. Multivariate linear and logistic regression analyses were conducted to assess the independent association of blood pressure with QTc interval.

Results

Hypertensive subjects had significantly longer QTc interval and higher prevalence of prolonged QTc interval compared with normotensive ones in all subgroups stratified by gender and left ventricular hypertrophy (LVH) (all Ps ≤ 0.001). Multiple relevant clinical confounding factors and LVM were all adjusted in the multivariate linear and logistic regression analyses. As a result, both systolic blood pressure (SBP) and diastolic blood pressure (DBP) were independently associated with QTc interval (β = 0.12 and 0.16, respectively; Ps < 0.001). Furthermore, as categorical variables, hypertension was independently associated with prolonged QTc interval (OR = 1.71; P < 0.001). Sex-specific analyses revealed that the independent associations were detected in both males and females (all Ps < 0.001).

Conclusions

These key findings of the current study highlighted the fact that hypertension was significantly associated with prolonged QTc interval and the correlations were independent of confounding factors and LVM.

Rate-responsive pacing and atrial high rate episodes in cardiac resynchronization therapy patients: Is low heart rate the key?

BACKGROUND

The role of atrial rate-responsive (RR) pacing in cardiac resynchronization therapy (CRT) is unclear due to the favorable effect of rate lowering in systolic heart failure. Atrial high rate episodes (AHREs) in CRT recipients are particularly worrisome since they cause loss of CRT, beyond representing a stroke risk factor.

HYPOTHESIS

The presence of an association between RR and the incidence of AHREs.

METHODS

Daily remote transmissions from 836 CRT recipients were analyzed. AHREs were classified by duration: ≥15 minutes, ≥5 hours, and ≥ 24 hours. Variables possibly associated to AHREs were included in time-dependent proportional-hazard models, averaging over 30-day periods and adjusting for main baseline variables.

RESULTS

After a median follow-up of 23.9 (12.2-36.0) months, 507 (60.6%) patients experienced at least one 15-minute AHRE. RR function was programmed in 166 (19.8%) patients and was associated with an increased AHRE occurrence rate with hazard ratio (HR) ranging from 1.45 to 1.78 for the 3 cutoffs of episode duration. The negative effect of RR function was not observed in the subset of patients with low mean heart rate (<68 bpm). Higher mean heart rates increased AHRE risk (HR:1.02, P = .01), while CRT amount decreased it (HR:0.98, P < .01). The extent of atrial pacing did not predict AHRE occurrence.

CONCLUSIONS

RR pacing in CRT recipients is associated with increased AHRE occurrence, especially when an average heart rate > 68 bpm is attained.

The effect of ivabradine therapy on heart failure patients with reduced ejection fraction: a systematic review and meta-analysis

Background Ivabradine is currently indicated to lower heart rate in Heart Failure with Reduced Ejection Fraction (HFrEF) patients. However its effect apart from beta-blockers is not clear. Aim of the review To study the additional effect of ivabradine, apart from the effect of beta-blockers, on cardiovascular death, all-cause mortality, hospitalization due to HF and heart rate in HFrEF population. Method Electronic searches were conducted up to June 2016 to include randomized controlled trials where ivabradine was compared to a control group. Relative risks RRs and their 95% confidence intervals (CI 95%) were pooled and the random and fixed effect were used to summarize the results according to heterogeneity levels. Heterogeneity among studies was measured by the I-squared statistic Results Of 1790 studies, seven met the inclusion criteria for the systematic review and meta-analysis. The population consisted of 17,747 patients. Risk of bias was generally high for beta-blocker doses lower than recommended. Interventions lasted 1.5-22.9 months and pooled relative risks RR (95%) for all-cause mortality, cardiovascular death and hospitalization for HF were 0.98 (0.90-1.06); 0.99 (0.91-1.08); and 0.87 (0.68-1.12) respectively. Heart rate (CI 95%) decreased by 8.7 (6.37-11.03) beats per minute with ivabradine compared to the control group. Subgroup analysis by beta-blocker dose showed that for patients on recommended treatment (at least 50% of the beta-blocker target dose), heart rate (CI 95%) decreased by 4.70 (3.67-5.73), whereas for patients not on recommended treatment or with unreported dose, heart rate decreased by 8.60 (8.13-9.08). Conclusion Ivabradine significantly reduced heart rate and its additional effect on heart rate appears to be inversely correlated with the dose of beta-blocker. It showed no significant effect for all-cause mortality, cardiovascular death and hospitalization due to HF. Unreported beta-blocker doses and beta-blocker doses lower than recommended limited the conclusions.