Browsing by Subject "heart rate"

Now showing 1 - 4 of 4
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    Achieving Guideline-Directed Heart Rate Control Early Posthospitalization
    (Elsevier, 2019) Jungbauer, Carsten; Maier, Lars S.; Emoto, Kikuo; Zirille, Francis M.; Mirro, Michael J.; Medicine, School of Medicine
    Guidelines for the treatment of heart failure (HF) recommend the titration of β blockers (BB) to a target dosage shown to be effective in clinical trials. The benefit of BBs is associated with heart rate (HR) control, with a target resting HR <70 bpm which in clinical trials have been associated with improved clinical outcomes. The primary purpose of this study was to gauge the ability to achieve guideline-directed medical therapy HR control in the early posthospitalization period for HF patients with the wearable cardioverter defibrillator (WCD), assessing whether the WCD could be used to evaluate HR both at rest and during activity to determine if targets were being met and to adequately direct clinical decision making. The WCD platform allows continuous recording of HR. To assess the guideline-directed therapy goals for reduction of resting HR, HR was evaluated both at rest (nighttime: midnight-7 a.m.; daytime: 7 a.m. midnight), and during activity of daily living. HR data during activity of daily living (ADL) and rest were collected from patients with HF that wore the WCD for ≥5 weeks (n = 1,353) between 2015 and 2017. First, 643,891 activity episodes from 1,353 patients were analyzed. Daytime and nighttime resting HRs significantly dropped from beginning to end of WCD use (day: 72.5 bpm vs 69.0 bpm, p <0.0001; night: 68.1 vs 64.3, p <0.0001). However, 43% of patients still had an average daytime resting HR ≥70 bpm during the last week of WCD use. When comparing a patient’s peak activity HR during the first week of WCD use to the last week, there was no difference (93.6 bpm vs 94.1 bpm, p = 0.23). During ADL, 31% of patients had a HR ≥100 bpm, 14% of patients had a HR ≥110 bpm, and 6% had a HR ≥120 bpm. In conclusion, months after hospital discharge, 43% of patients did not meet guideline-directed resting target HR control, indicating they may not have been effectively managed with BB. HR during ADL may have also been higher than preferred. Remote HR monitoring may help physicians to adequately titrate guideline-directed medical therapy, thus improving clinical outcomes in HF patients.
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    Automated Quantitative Analysis of Nerve Fiber Conduction Velocity
    (Office of the Vice Chancellor for Research, 2015-04-17) Haas, Kyle D.; Santa Cruz Chavez, Grace; Schild, John
    The baroreflex (BRX) is essential for reliable autonomic control of arterial blood pressure. Central to BRX function is a rapid, negative feedback control of heart rate. Arterial pressure sensors known as baroreceptors (BR) encode heart rate and blood pressure information into patterns of neural discharge that is conveyed to the central nervous system via a network of sensory afferent nerve fibers. These BR fibers are broadly classified as myelinated A-fibers with diameters in the range of 1-10 μm and unmyelinated Cfibers with diameters typically less than 1 μm. Fiber diameter and conduction velocity are related with the large A-fibers being much faster (> 10 m/sec) than the smaller diameter C-fibers (< 1 m/sec). Recently, our lab has documented an additional phenotype of myelinated BR afferents termed Ah-fibers that are notably present in female; but only rarely observed in male rats. In response to an electrical stimulus, the nerve fibers produce a compound action potential (CAP) that propagates away from the stimulation site. The CAP of each fiber type is observable in the evoked waveform on account of the differing conduction velocities. As Ah-fibers have conduction velocities in the range of 10 m/sec - 2 m/sec, the resulting CAP is clearly separated in time from the faster A-fibers and much slower C-fibers. Root-mean-square analysis of these distinct time segments provides a quantitative measure of the total signal energy from each of the A-, Ah-, and C-type fibers. This project sought to create MATLAB scripts that would import nerve recording files from both male and female rats and automate the energy analysis in an efficient and reliable manner. Doing so not only facilitates the analysis of these large data files, but also reduces the possibility for biases and errors that can occur during a manual measurement of nerve activity.
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    Effect on Mortality of Higher Versus Lower β-Blocker (Metoprolol Succinate or Carvedilol) Dose in Patients With Heart Failure
    (Elsevier, 2018) Ajam, Tarek; Ajam, Samer; Devaraj, Srikant; Fudim, Marat; Kamalesh, Masoor; Medicine, School of Medicine
    This study aimed to compare the effect of β-blocker dose and heart rate (HR) on mortality in patients with heart failure with reduced ejection fraction (HFrEF). The Veteran Affairs databases were queried to identify all patients diagnosed with HFrEF based on International Classification of Diseases Ninth Revision codes from 2007 to 2015 and β-blocker (carvedilol or metoprolol succinate) use. 36,168 patients on low dose β blocker were then matched with 36,168 patients on high dose β-blocker using propensity score matching. The impact of β-blocker dose and HR was assessed on overall mortality using Cox proportional hazard model. After dividing average HR into separate quartiles and adjusting for patient characteristics, high β-blocker dose was associated with lower overall mortality as compared with a low dose of β blocker (hazard ratio 0.75, 95% confidence interval 0.73 to 0.77, p <0.01) independent of the HR achieved. The results held for all 4 quartiles of average HR. A higher β-blocker dose or a lower HR were independently and jointly associated with lower mortality for all quartiles of HR. In conclusion, higher dose of β-blocker therapy and a lower achieved HR were independently associated with a reduction in mortality in HFrEF patients.
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    Role of the Dorsomedial Hypothalamus in Responses Evoked from the Preoptic Area and by Systemic Administration of Interleukin-1β
    (2009-06-23T21:35:36Z) Hunt, Joseph L.; DiMicco, Joseph A.; Cummins, Theodore R.; Rusyniak, Daniel; Vasko, Michael R.
    Recent studies in anesthetized rats suggest that autonomic effects relating to thermoregulation that are evoked from the preoptic area (POA) may be mediated through activation of neurons in the dorsomedial hypothalamus (DMH). Disinhibition of neurons in the DMH produces not only cardiovascular changes but also increases in plasma adrenocorticotropic hormone (ACTH) and locomotor activity mimicking those evoked by microinjection of muscimol, a GABAA receptor agonist and neuronal inhibitor, into the POA. Therefore, I tested the hypothesis that all of these effects evoked from the POA are mediated through neurons in the DMH by assessing the effect of bilateral microinjection of muscimol into the DMH on the changes evoked by microinjection of muscimol into the POA in conscious rats. In addition, I tested the hypothesis that neurons in the DMH mediate a specific response that is thought to signal through the POA, the activation of the HPA axis evoked by systemic administration of the inflammatory cytokine IL-1β. After injection of vehicle into the DMH, injection of muscimol into the POA elicited marked increases in heart rate, arterial pressure, body temperature, plasma ACTH and locomotor activity and also increased Fos expression in the hypothalamic paraventricular nucleus (PVN), a region known to control the release of ACTH from the adenohypophysis, and the raphe pallidus, a medullary region known to mediate POA-evoked sympathetic responses. Prior microinjection of muscimol into the DMH produced a modest depression of baseline heart rate, arterial pressure, and body temperature but completely abolished all changes evoked from the POA. Microinjection of muscimol just anterior to the DMH had no effect on POA-evoked autonomic and neuroendocrine changes. Inhibition of neuronal activity in the DMH only partially attenuated the increased activity of the HPA axis following systemic injections of IL-1β. Thus, neurons in the DMH mediate a diverse array of physiological and behavioral responses elicited from the POA, suggesting that the POA represents an important source of inhibitory tone to key neurons in the DMH. However, it is clear that the inflammatory cytokine IL-1β must employ other pathways that are DMH-, and possibly POA-, independent to activate the HPA axis.