What is the clinical evidence from this study?

Study design: Other. Population: Heart failure (n=17). Intervention: Volume expansion and hemorrhage vs. Normal sheep. Primary outcome: Change in cardiac sympathetic nerve activity (CSNA) during volume expansion in normal sheep (p=<0.05).

What question did this study set out to answer?

To determine whether selective changes in burst amplitude and frequency drive organ-specific sympathetic responses to blood volume alterations and explain blunted responses in heart failure.

June 17, 2009AJP Regulatory Integrative and Comparative PhysiologyOpen Access

Discharge properties of cardiac and renal sympathetic nerves and their impaired responses to changes in blood volume in heart failure

Q: What are the key findings of this study?

In normal sheep, volume expansion decreased cardiac sympathetic nerve activity by 59%, whereas in sheep with heart failure, volume expansion caused no change in cardiac sympathetic nerve activity.

Q: What question did this study set out to answer?

To determine whether selective changes in burst amplitude and frequency drive organ-specific sympathetic responses to blood volume alterations and explain blunted responses in heart failure.

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Key result

In normal sheep, volume expansion decreased cardiac sympathetic nerve activity by 59%, whereas in sheep with heart failure, volume expansion caused no change in cardiac sympathetic nerve activity.

Why the study?

Does heart failure alter the amplitude and frequency components of cardiac and renal sympathetic nerve activity in response to changes in blood volume?

Population

Adult merino ewes (35-49 kg body wt), normal (n=9) and heart failure induced by rapid ventricular pacing (n=8)

Comparison

Volume expansion and hemorrhage vs Normal sheep vs. Heart failure sheep

Design

Preclinical, randomly allocated basis

Authors

RRRohit RamchandraUniversity of Auckland SHSally G. HoodThe University of Melbourne RFRobert FrithiofUppsala University

Discussion

Member takes

Implication

Should not yet inform HF volume strategies; leaves open whether sympathetic responses differ similarly in patients.

Key Points

To determine whether selective changes in burst amplitude and frequency drive organ-specific sympathetic responses to blood volume alterations and explain blunted responses in heart failure.
Simultaneously recorded cardiac sympathetic nerve activity (CSNA) and renal sympathetic nerve activity (RSNA) in conscious healthy sheep and sheep with rapid ventricular pacing-induced heart failure (n=6).
Assessed changes in burst frequency and amplitude during volume expansion and hemorrhage interventions.
In normal sheep (n=6), volume expansion reduced CSNA (-62 ± 10%, P < 0.05) via decreased burst frequency, and RSNA (-59 ± 10%, P < 0.05) via decreases in both burst frequency and amplitude.
In normal sheep, hemorrhage elevated CSNA (+74 ± 9%, P < 0.05) more than RSNA (+21 ± 5%, P < 0.09) by increasing burst frequency while decreasing burst amplitude.
In heart failure, baseline CSNA burst frequency rose from 26 ± 3 to 75 ± 3 bursts/min while RSNA rose from 63 ± 4 to 79 ± 4 bursts/min; volume expansion caused no change in CSNA and an attenuated fall in RSNA, while hemorrhage produced no significant response in either nerve.

Structured PICO

Does heart failure alter the amplitude and frequency components of cardiac and renal sympathetic nerve activity in response to changes in blood volume?

Population

17 adult female sheep (9 normal, 8 with pacing-induced heart failure) underwent volume expansion and hemorrhage to assess cardiac and renal sympathetic nerve activity.

Intervention

Volume expansion (500 ml Gelofusine infusion) and hemorrhage (500 ml blood removal)

Comparator

Normal sheep vs. Heart failure sheep

Outcome

Changes in cardiac sympathetic nerve activity (CSNA) and renal sympathetic nerve activity (RSNA), including burst frequency and amplitudesurrogate

Main Result

p-value: p=<0.05

Heart failure impairs the normal organ-specific sympathetic nerve activity responses to changes in blood volume, driven by selective alterations in burst amplitude and frequency.

Limitations

Animal model may not perfectly translate to human physiology
Cannot rule out that a Bainbridge reflex response would have been initiated if the infusion rate had been more rapid
Small, non-significant changes in mean arterial pressure may have activated arterial baroreceptor afferents and contributed to the changes
Cannot rule out that a Bainbridge reflex response would have been initiated if the infusion rate of Gelofusine had been more rapid
Cannot rule out the possibility that small, nonsignificant changes in MAP may have activated arterial baroreceptor afferents

Cite This Study

Ramchandra et al. (2009) studied Heart failure (n=17). Volume expansion and hemorrhage vs. Normal sheep was evaluated on Change in cardiac sympathetic nerve activity (CSNA) during volume expansion in normal sheep (p=<0.05). In normal sheep, volume expansion decreased cardiac sympathetic nerve activity by 59%, whereas in sheep with heart failure, volume expansion caused no change in cardiac sympathetic nerve activity.

synapsesocial.com/papers/6a74c88bf2cd31a1fadbe5ff https://doi.org/10.1152/ajpregu.00191.2009

Topics

Heart failure HFrEF treatment

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Discharge properties of cardiac and renal sympathetic nerves and their impaired responses to changes in blood volume in heart failure

Discussion

Member takes

Implication

Key Points

Structured PICO

Main Result

Limitations

Cite This Study

Topics

Discharge properties of cardiac and renal sympathetic nerves and their impaired responses to changes in blood volume in heart failure

Discussion

Member takes

Implication

Key Points

Structured PICO

Main Result

Limitations

Cite This Study

Also Consider

Topics

Also Consider