The thick left ventricular wall of the giraffe heart normalises wall tension, but limits stroke volume and cardiac output

Morten Holdgaard Smerup; Mads Damkjær; Emil Brøndum; Ulrik T. Baandrup; Steen Buus Kristiansen; Hans Nygaard; Christian Aalkjær; Cathrine Sauer; Rasmus Buchanan; Mads Frost Bertelsen; Kristine Hovkjær Østergaard; Carsten Grøndahl; Geoffrey Candy; J Michael Hasenkam; Niels H Secher; Peter Bie; Tobias Wang

doi:10.1242/jeb.132753

The thick left ventricular wall of the giraffe heart normalises wall tension, but limits stroke volume and cardiac output

Morten Holdgaard Smerup, Mads Damkjær, Emil Brøndum, Ulrik T. Baandrup, Steen Buus Kristiansen, Hans Nygaard, Christian Aalkjær, Cathrine Sauer, Rasmus Buchanan, Mads Frost Bertelsen, Kristine Hovkjær Østergaard, Carsten Grøndahl, Geoffrey Candy, J Michael Hasenkam, Niels H Secher, Peter Bie, Tobias Wang

Publikation: Bidrag til tidsskrift/Konferencebidrag i tidsskrift /Bidrag til avis › Tidsskriftartikel › Forskning › peer review

Abstract

Giraffes - the tallest extant animals on Earth - are renowned for their high central arterial blood pressure, which is necessary to secure brain perfusion. Arterial pressure may exceed 300 mmHg and has historically been attributed to an exceptionally large heart. Recently, this has been refuted by several studies demonstrating that the mass of giraffe heart is similar to that of other mammals when expressed relative to body mass. It thus remains unexplained how the normal-sized giraffe heart generates such massive arterial pressures. We hypothesized that giraffe hearts have a small intraventricular cavity and a relatively thick ventricular wall, allowing for generation of high arterial pressures at normal left ventricular wall tension. In nine anaesthetized giraffes (495±38 kg), we determined in vivo ventricular dimensions using echocardiography along with intraventricular and aortic pressures to calculate left ventricular wall stress. Cardiac output was also determined by inert gas rebreathing to provide an additional and independent estimate of stroke volume. Echocardiography and inert gas-rebreathing yielded similar cardiac outputs of 16.1±2.5 and 16.4±1.4 l min ^-1, respectively. End-diastolic and end-systolic volumes were 521±61 ml and 228±42 ml, respectively, yielding an ejection fraction of 56±4% and a stroke volume of 0.59 ml kg ^-1. Left ventricular circumferential wall stress was 7.83±1.76 kPa. We conclude that, relative to body mass, a small left ventricular cavity and a low stroke volume characterizes the giraffe heart. The adaptations result in typical mammalian left ventricular wall tensions, but produce a lowered cardiac output.

Originalsprog	Engelsk
Tidsskrift	Journal of Experimental Biology
Vol/bind	49
Nummer	3
Sider (fra-til)	457-63
Antal sider	7
ISSN	0022-0949
DOI	https://doi.org/10.1242/jeb.132753
Status	Udgivet - 2016

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Smerup, M. H., Damkjær, M., Brøndum, E., Baandrup, U. T., Kristiansen, S. B., Nygaard, H., Aalkjær, C., Sauer, C., Buchanan, R., Bertelsen, M. F., Østergaard, K. H., Grøndahl, C., Candy, G., Hasenkam, J. M., Secher, N. H., Bie, P., & Wang, T. (2016). The thick left ventricular wall of the giraffe heart normalises wall tension, but limits stroke volume and cardiac output. Journal of Experimental Biology, 49(3), 457-63. https://doi.org/10.1242/jeb.132753

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title = "The thick left ventricular wall of the giraffe heart normalises wall tension, but limits stroke volume and cardiac output",

abstract = "Giraffes - the tallest extant animals on Earth - are renowned for their high central arterial blood pressure, which is necessary to secure brain perfusion. Arterial pressure may exceed 300 mmHg and has historically been attributed to an exceptionally large heart. Recently, this has been refuted by several studies demonstrating that the mass of giraffe heart is similar to that of other mammals when expressed relative to body mass. It thus remains unexplained how the normal-sized giraffe heart generates such massive arterial pressures. We hypothesized that giraffe hearts have a small intraventricular cavity and a relatively thick ventricular wall, allowing for generation of high arterial pressures at normal left ventricular wall tension. In nine anaesthetized giraffes (495±38 kg), we determined in vivo ventricular dimensions using echocardiography along with intraventricular and aortic pressures to calculate left ventricular wall stress. Cardiac output was also determined by inert gas rebreathing to provide an additional and independent estimate of stroke volume. Echocardiography and inert gas-rebreathing yielded similar cardiac outputs of 16.1±2.5 and 16.4±1.4 l min -1, respectively. End-diastolic and end-systolic volumes were 521±61 ml and 228±42 ml, respectively, yielding an ejection fraction of 56±4% and a stroke volume of 0.59 ml kg -1. Left ventricular circumferential wall stress was 7.83±1.76 kPa. We conclude that, relative to body mass, a small left ventricular cavity and a low stroke volume characterizes the giraffe heart. The adaptations result in typical mammalian left ventricular wall tensions, but produce a lowered cardiac output.",

keywords = "Cardiac output, Echocardiography, End diastolic volume, Left ventricle, Stroke volume",

author = "Smerup, {Morten Holdgaard} and Mads Damkj{\ae}r and Emil Br{\o}ndum and Baandrup, {Ulrik T.} and Kristiansen, {Steen Buus} and Hans Nygaard and Christian Aalkj{\ae}r and Cathrine Sauer and Rasmus Buchanan and Bertelsen, {Mads Frost} and {\O}stergaard, {Kristine Hovkj{\ae}r} and Carsten Gr{\o}ndahl and Geoffrey Candy and Hasenkam, {J Michael} and Secher, {Niels H} and Peter Bie and Tobias Wang",

note = "{\textcopyright} 2015. Published by The Company of Biologists Ltd.",

year = "2016",

doi = "10.1242/jeb.132753",

language = "English",

volume = "49",

pages = "457--63",

journal = "Journal of Experimental Biology",

issn = "0022-0949",

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Smerup, MH, Damkjær, M, Brøndum, E, Baandrup, UT, Kristiansen, SB , Nygaard, H , Aalkjær, C, Sauer, C, Buchanan, R, Bertelsen, MF, Østergaard, KH, Grøndahl, C, Candy, G, Hasenkam, JM, Secher, NH, Bie, P & Wang, T 2016, 'The thick left ventricular wall of the giraffe heart normalises wall tension, but limits stroke volume and cardiac output', Journal of Experimental Biology, bind 49, nr. 3, s. 457-63. https://doi.org/10.1242/jeb.132753

The thick left ventricular wall of the giraffe heart normalises wall tension, but limits stroke volume and cardiac output. / Smerup, Morten Holdgaard; Damkjær, Mads; Brøndum, Emil et al.
I: Journal of Experimental Biology, Bind 49, Nr. 3, 2016, s. 457-63.

Publikation: Bidrag til tidsskrift/Konferencebidrag i tidsskrift /Bidrag til avis › Tidsskriftartikel › Forskning › peer review

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T1 - The thick left ventricular wall of the giraffe heart normalises wall tension, but limits stroke volume and cardiac output

AU - Smerup, Morten Holdgaard

AU - Damkjær, Mads

AU - Brøndum, Emil

AU - Baandrup, Ulrik T.

AU - Kristiansen, Steen Buus

AU - Nygaard, Hans

AU - Aalkjær, Christian

AU - Sauer, Cathrine

AU - Buchanan, Rasmus

AU - Bertelsen, Mads Frost

AU - Østergaard, Kristine Hovkjær

AU - Grøndahl, Carsten

AU - Candy, Geoffrey

AU - Hasenkam, J Michael

AU - Secher, Niels H

AU - Bie, Peter

AU - Wang, Tobias

PY - 2016

Y1 - 2016

N2 - Giraffes - the tallest extant animals on Earth - are renowned for their high central arterial blood pressure, which is necessary to secure brain perfusion. Arterial pressure may exceed 300 mmHg and has historically been attributed to an exceptionally large heart. Recently, this has been refuted by several studies demonstrating that the mass of giraffe heart is similar to that of other mammals when expressed relative to body mass. It thus remains unexplained how the normal-sized giraffe heart generates such massive arterial pressures. We hypothesized that giraffe hearts have a small intraventricular cavity and a relatively thick ventricular wall, allowing for generation of high arterial pressures at normal left ventricular wall tension. In nine anaesthetized giraffes (495±38 kg), we determined in vivo ventricular dimensions using echocardiography along with intraventricular and aortic pressures to calculate left ventricular wall stress. Cardiac output was also determined by inert gas rebreathing to provide an additional and independent estimate of stroke volume. Echocardiography and inert gas-rebreathing yielded similar cardiac outputs of 16.1±2.5 and 16.4±1.4 l min -1, respectively. End-diastolic and end-systolic volumes were 521±61 ml and 228±42 ml, respectively, yielding an ejection fraction of 56±4% and a stroke volume of 0.59 ml kg -1. Left ventricular circumferential wall stress was 7.83±1.76 kPa. We conclude that, relative to body mass, a small left ventricular cavity and a low stroke volume characterizes the giraffe heart. The adaptations result in typical mammalian left ventricular wall tensions, but produce a lowered cardiac output.

AB - Giraffes - the tallest extant animals on Earth - are renowned for their high central arterial blood pressure, which is necessary to secure brain perfusion. Arterial pressure may exceed 300 mmHg and has historically been attributed to an exceptionally large heart. Recently, this has been refuted by several studies demonstrating that the mass of giraffe heart is similar to that of other mammals when expressed relative to body mass. It thus remains unexplained how the normal-sized giraffe heart generates such massive arterial pressures. We hypothesized that giraffe hearts have a small intraventricular cavity and a relatively thick ventricular wall, allowing for generation of high arterial pressures at normal left ventricular wall tension. In nine anaesthetized giraffes (495±38 kg), we determined in vivo ventricular dimensions using echocardiography along with intraventricular and aortic pressures to calculate left ventricular wall stress. Cardiac output was also determined by inert gas rebreathing to provide an additional and independent estimate of stroke volume. Echocardiography and inert gas-rebreathing yielded similar cardiac outputs of 16.1±2.5 and 16.4±1.4 l min -1, respectively. End-diastolic and end-systolic volumes were 521±61 ml and 228±42 ml, respectively, yielding an ejection fraction of 56±4% and a stroke volume of 0.59 ml kg -1. Left ventricular circumferential wall stress was 7.83±1.76 kPa. We conclude that, relative to body mass, a small left ventricular cavity and a low stroke volume characterizes the giraffe heart. The adaptations result in typical mammalian left ventricular wall tensions, but produce a lowered cardiac output.

KW - Cardiac output

KW - Echocardiography

KW - End diastolic volume

KW - Left ventricle

KW - Stroke volume

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DO - 10.1242/jeb.132753

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SN - 0022-0949

VL - 49

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EP - 463

JO - Journal of Experimental Biology

JF - Journal of Experimental Biology

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ER -

The thick left ventricular wall of the giraffe heart normalises wall tension, but limits stroke volume and cardiac output

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