Haruhiko Abe

Ritsuko Kohno

Yasushi Oginosawa

Journal of Arrhythmia

Abe, Haruhiko

Kohno, Ritsuko

Oginosawa, Yasushi

Elsevier - Publisher Connector 

Journal of Arrhythmia 29 (2013) 37–38Contents lists available at SciVerse ScienceDirectJournal of Arrhythmia1880-42
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DOI ojournal homepage: www.elsevier.com/locate/joaEditorial CommentsReﬂex syncope during a hot bath as a speciﬁc cause of drowning
in JapanOut-of-hospital cardiac arrest is a leading cause of death in
Japan and other industrialized countries [1,2]. In 2005, the Fire
and Disaster Management Agency of Japan launched the All-Japan
Utstein Registry—a prospective, nationwide, population-based
study of out-of-hospital cardiac arrest [3]. The annual incidence
of out-of-hospital cardiac arrest and the number of events
with cardiac causes increased gradually from 56,412 in 2005 to
63,296 in 2008. The incidence of out-of-hospital cardiac
arrest was highest in the elderly, reaching 71% in individuals
470 years of age, and more than half of the overall population
was male.
There was a signiﬁcantly higher incidence of out-of-hospital
cardiac arrests in the winter season, particularly in January and
December, than in other months of the year. This ﬁnding was
consistent from year to year and at all ages. The Fire and Disaster
Management Agency of Japan indicates that the incidence of out-
of-hospital cardiac arrest is as follows: (a) more common on
Sundays and Mondays than on other days of the week, and
(b) more common during early morning and evening hours than
at other times of the day. The monthly and weekly distributions of
the incidence of out-of-hospital cardiac arrest in populations of
individuals o69 years of age (individuals of working age) are
similar to those of all-age populations. In contrast, the daily
distributions of the incidence of out-of-hospital cardiac arrest in
the working population show a single peak in the early morning
hours. One of the possible explanations for this difference in the
daily distributions between working populations and elderly
Japanese might be syncope during bathing in Japan.
Between 1989 and 1993, approximately 10% of sudden deaths
in Japan conﬁrmed by the Tokyo Medical Examiner’s Ofﬁce
occurred at home during hot baths in a deep bathtub. The
reported risk of sudden death is 10-fold higher during bathing
than during sleep in the elderly Japanese people [4]. One of the
causes of drowning during immersion in hot water may be
syncope due to a precipitous decrease in blood pressure [4,5]. A
low external temperature in the winter season increases sympa-
thetic nerve tone and catecholamine release, which increase heart
rate, vascular resistance, ventricular contractility, and blood
pressure [6,7]. A rapid increase in body temperature by bathing
causes a precipitous fall in blood pressure and syncope within the
bathtub.
Most Japanese individuals take a deep hot bath each evening
because most homes are not as well insulated as those in Western76/$ - see front matter & 2012 Japanese Heart Rhythm Society. Published by E
x.doi.org/10.1016/j.joa.2012.10.002
f original article: http://dx.doi.org/10.1016/j.joa.2012.10.001.countries and central heating is uncommon. The deeper bathtub,
higher temperature, and longer spent time in the hot bath,
particularly in the winter season, are characteristic in Japan.
The temperature difference between inside and outside the
bathtub or bathroom is considerable in the winter season,
which might precipitate hypotension, bradycardia, and loss of
consciousness.
In elderly individuals, blood pressure and heart rate begin to
rise immediately upon immersion in a hot tub and decrease
after approximately 4 min [4]. These changes are associated
with a temporary decrease in sympathetic activity without
compensatory suppression of the parasympathetic tone, resulting
in hypotension- and bradycardia-induced syncope. In addition,
in contrast to young persons, older individuals have difﬁculty
maintaining homeostasis during immersion in a deep hot
bath because of the autonomic nervous system’s inability to
respond in a sufﬁciently vigorous manner to cardiovascular stress
[4,8]. Parasympathetic activity is depressed, and sympathetic
activity may decrease rather than increase at a time when
vasoconstriction is required to maintain blood pressure.
Hypotension, bradycardia, loss of consciousness, and death by
drowning may ultimately result from this transient autonomic
imbalance [4,5,8]. Thus, a putative explanation for the blunted
evening peak in the younger sample set might be the higher
incidence of domestic drowning in hot baths among elderly
individuals [4,5].
In this issue, Nakao et al. [9] report a case involving the
collection of direct evidence of reﬂex syncope due to a marked
cardioinhibitory response (possibly associated with hypotension)
during bathing by the use of an implantable loop recorder in a
young man who had previously successfully recovered from an
out-of-hospital cardiac arrest in the same situation. This patient
was successfully treated with pacemaker implantation and did
not experience any further symptoms during bathing. Thus,
drowning—due to reﬂex bradycardia, hypotension, and syncope
during hot bathing—as a cause of out-of-hospital cardiac arrest
may not be uncommon in Japan.References
[1] ECC committee. Subcommittees and task forces of the american heart
association. American heart association guidelines for cardiopulmonary resus-
citation and emergency cardiovascular care. Circulation 2005;112(Suppl.
24):IV1-203.
[2] Kitamura T, Iwami T, Kawamura T, et al. Nationwide public access deﬁbrilla-
tion in Japan. N Engl J Med 2010;362:994–1004.lsevier B.V. All rights reserved.
Editorial Comments / Journal of Arrhythmia 29 (2013) 37–3838[3] Kitamura T, Iwami T, Kawamura T, et al. Implementation working
group for the all-Japan Utstein registry of the ﬁre and disaster management
agency. Nationwide public-access deﬁbrillation in Japan. N Engl J Med
2010;362:994–1004.
[4] Nishiyama C, Iwami T, Nichol G, et al. Association of out-of-hospital cardiac
arrest with prior activity and ambient temperature. Resuscitation
2011;82:1008–12.
[5] Nagasawa Y, Komori S, Sato M, et al. Effects of hot bath immersion on
autonomic activity and hemodynamics: comparison of the elderly patient and
the healthy young. Jpn Circ J 2001;65:587–92.
[6] Millar-Craig MW, Bishop CN, Raftery EB. Circadian variation of blood pressure.
Lancet 1978;1(8068):795–7.
[7] Toﬂer GH, Brezinski D, Schafer AI, et al. Concurrent morning increase in
platelet aggregability and the risk of myocardial infarction and sudden cardiac
death. N Engl J Med 1987;316:1514–8.
[8] Chiba T, Yamauchi M, Nishida N, et al. Risk factors of sudden death
in the Japanese hot bath in the senior population. Forensic Sci Int
2005;149:151–8.
[9] Nakao M, Kobayashi S, Nakamura D, et al. Usefulness of implantable loop
recorder in a patient with syncope during bathing. J Arrhythmia 2013;29:
37–39, in press.Haruhiko Abe n
Department of Heart Rhythm Management,
Division of Cardiology,
University of Occupational and Environmental Health, Japan,
1-1, Iseigaoka Yahatanishi-ku, Kitakyushu 807-8555, Japan
E-mail address: haru-abe@med.uoeh-u.ac.jpRitsuko Kohno, Yasushi Oginosawa
Second Department of Internal Medicine, Division of Cardiology,
University of Occupational and Environmental Health, Japan
Available online 22 November 2012n Corresponding author. Tel.: þ81 93 691 7514; fax: þ81 93 691 7547.


Reflex syncope during a hot bath as a specific cause of drowning in Japan 

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Reflex syncope during a hot bath as a specific cause of drowning in Japan

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Reflex syncope during a hot bath as a specific cause of drowning in Japan

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