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

Morten Smerup; Mads Damkjær; Emil Toft Brøndum; Ulrik T. Baandrup; Steen Buus Kristiansen; Hans Nygaard; Jonas Amstrup Funder; 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 Smerup, Mads Damkjær, Emil Toft Brøndum, Ulrik T. Baandrup, Steen Buus Kristiansen, Hans Nygaard, Jonas Amstrup Funder, 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

13 Citations (Scopus)

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.

Original language	English
Journal	The Journal of Experimental Biology
Volume	219
Issue number	3
Pages (from-to)	457-463
Number of pages	7
ISSN	0022-0949
DOIs	https://doi.org/10.1242/jeb.132753
Publication status	Published - 1 Feb 2016

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Smerup, M., Damkjær, M., Brøndum, E. T., Baandrup, U. T., Kristiansen, S. B., Nygaard, H., Funder, J. A., 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. The Journal of Experimental Biology, 219(3), 457-463. https://doi.org/10.1242/jeb.132753

Smerup, M, Damkjær, M, Brøndum, ET, Baandrup, UT, Kristiansen, SB, Nygaard, H, Funder, JA, 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', The Journal of Experimental Biology, vol. 219, no. 3, pp. 457-463. 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.",

author = "Morten Smerup and Mads Damkj{\ae}r and Br{\o}ndum, {Emil Toft} and Baandrup, {Ulrik T.} and Kristiansen, {Steen Buus} and Hans Nygaard and Funder, {Jonas Amstrup} 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",

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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

AU - Damkjær, Mads

AU - Brøndum, Emil Toft

AU - Baandrup, Ulrik T.

AU - Kristiansen, Steen Buus

AU - Nygaard, Hans

AU - Funder, Jonas Amstrup

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 - 2016/2/1

Y1 - 2016/2/1

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.

U2 - 10.1242/jeb.132753

DO - 10.1242/jeb.132753

M3 - Journal article

C2 - 26643090

SN - 0022-0949

VL - 219

SP - 457

EP - 463

JO - The Journal of Experimental Biology

JF - The Journal of Experimental Biology

IS - 3

ER -

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

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