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Brain & Heart RDN guided by novel blood pressure responses

rate decreased after selective ablation guided by these BP that need to be ablated. RNS can assist interventionalists
patterns. in identifying inappropriate sites with dominantly
Renal nerves regulate the arterial BP and functions parasympathetic fibers and performing more accurate
of the cardiovascular system mainly via two reflexes. ablation. Therefore, RNS prior to ablation is advisable
Efferent renal nerves play an important role in modulating and considerable in clinical settings. Additionally, RNS
renal vascular resistance, renin release, and sodium/ can screen hypertensive with more drop sites, for which
water reabsorption . Afferent renal nerves were RDN may not be suitable, and serve a similar role in
[21]
proven to be directly and rapidly involved in regulating the treatment of hypertension, like electrophysiological
systemic sympathetic activity and vascular tension by examination in patients with arrhythmias.
the cardiovascular regulatory nuclear mass, such as the Previous studies have also confirmed that destroying
rostral ventrolateral medulla and paraventricular nucleus the sites with elevated BP caused by RNS can result in a
of the hypothalamus . In gross anatomy, renal nerves significant drop in postoperative BP [14,19,26] . Further in this
[22]
are composed of complicated neural networks along the study, BP reduction was observed early and continued
renal artery ; thus, it is not easy to empirically judge to 6 – 12 months postoperatively after ablation in these
[23]
the position of nerves. In this study, five BP responses sites of drop first and then rising (type 2). However, SBP
supported diverse renal nerves, including pressor and elevation during repeated stimulation after ablation
depressor fibers, co-existing and gather . Therefore, it had a similar reduction but a greater standard deviation
[10]
is necessary to identify the appropriate nerve innervation (7.4 ± 14.2 mmHg vs. 7.2 ± 9.3 mmHg) compared to the
sites via the autonomic nerve response caused by RNS, sites with type 1 (Figure 3). The destruction of partial
which has proven feasible and safe in animal and human “depressor fibers” may play a role in the instability of
studies [24,25] . SBP change. Thus, sites with type 2 should be the inferior
The intraoperative BP responses for detecting the renal candidates for ablation. In addition, an ABP reduction of
nerves still need a detailed evaluation, although previous 13.8/9.6 mmHg in this study with lower baseline BP and
studies pointed out that BP response to the RNS rise or fewer ablation sites seems more significant than that of
[6]
drop. Based on the complex anatomy basis that different 9.0/6.0 mmHg in the SPYRAL HTN-ON-MED trial .
fibers interweaved and distributed in a network [15,23] , renal Moreover, another anatomy-based RDN trial, including
nerves under stimulation or ablation may have different similar mildly resistant hypertension, showed a smaller
functional fibers, not just one. Therefore, five types of BP decrease (7.0/2.8 mmHg) in ABP during 6 months of
[2]
responses, including bidirectional successive changes in follow-up . We observed the rapid ABP drop for 5 –
this study, were reasonable theoretically and also observed 7 days. It may be associated with the selective and effective
in an animal study by our team . Meanwhile, similar destruction of afferent renal nerves. Selecting the proper
[18]
proportions of BP response types were also observed in ablative sites may guarantee the efficacy of RDN, and
this study. Unlike collecting all the data on SBP to show further research is needed for clarification.
the trend of BP fluctuation in the animal study, a simple Similar to ABP, the average heart rate was also reduced
method using just several specific values to identify the during the follow-up period. A recent study has also
type of BP response is more convenient and practicable in revealed that a higher baseline heart rate (approximately
clinical settings. It can assist the interventionalist in quickly >70 bpm) in patients with hypertension had a significant
judging the pattern of BP response during the procedure. reduction in heart rate after RDN . Likewise, two studies
[27]
For the first time, we reported that RNS could evoke found that baseline 24-h ambulatory and office heart
biphasic BP changes (type 2 and type 3) that drop almost rates above 70 bpm could predict greater BP reduction at
[28,29]
preceded an increase in patients with hypertension. It may 3 months . Thus, in this study, a baseline average heart
relate to the simultaneous activation of the different nerve rate of 77 ± 8 bpm may reflect higher sympathetic drive
fibers. Meanwhile, both our study and previous research and be associated with a significant reduction in BP and
found BP decrease could be induced by RNS [12,14,19] . The heart rate after the RDN procedure.
sites with BP drops indicated that nerves around the renal The present study was constrained by some limitations.
artery own parasympathetic properties. Recent research First, the principle (rationale) of regulating different BP
has shown anatomical evidence for parasympathetic responses to RNS by different nerve fibers (pressors and
innervation of the renal vasculature . It is inferable depressors) around renal arteries in this study needs further
[16]
that ablation of these sites with BP drops may result in histological or anatomical evidence. Second, the effect
a BP rise after the RDN procedure. Knowing the sites to of ablating the sites with continuous BP drop responses
avoid ablation is equally important as knowing the sites to RNS was not verified due to ethical considerations.

Volume 1 Issue 2 (2023) 8 https://doi.org/10.36922/bh.0384