Detection of Right-to-Left Shunts with an Arterial Potentiometric Electrode

Clark, Leland C.; Bargeron, Lionel M.; Lyons, Champ; Bradley, Merrill N.; McArthur, Katrina T.

doi:10.1161/01.cir.22.5.949

Cited by 44 publications

(12 citation statements)

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“…The presence or absence of blood flow between the LAo and RAo through the FoP was determined using a H 2 -electrode technique (Clark et al, 1960;Hicks and Comeau, 1994;Malvin et al, 1995), as previously described (Eme et al, 2009a). Animals were fasted for between 2 and 6 days prior to experimentation and sacrifice.…”

Section: Confirmation Of Chronic Occlusion Of Laomentioning

confidence: 99%

Turning crocodilian hearts into bird hearts: growth rates are similar for alligators with and without right-to-left cardiac shunt

Eme

Gwalthney

Owerkowicz

et al. 2010

Journal of Experimental Biology

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SUMMARYThe functional and possible adaptive significance of non-avian reptiles' dual aortic arch system and the ability of all non-avian reptiles to perform central vascular cardiac shunts have been of great interest to comparative physiologists. The unique cardiac anatomy of crocodilians -a four-chambered heart with the dual aortic arch system -allows for only right-to-left (R-L; pulmonary bypass) cardiac shunt and for surgical elimination of this shunt. Surgical removal of the R-L shunt, by occluding the left aorta (LAo) upstream and downstream of the foramen of Panizza, results in a crocodilian with an obligatory, avian/mammalian central circulation. In this study, R-L cardiac shunt was eliminated in age-matched, female American alligators (Alligator mississippiensis; 5-7 months of age). We tested the hypothesis that surgical elimination of R-L cardiac shunt would impair growth (a readily measured proxy for fitness) compared with sham-operated, age-matched controls, especially in animals subjected to exhaustive exercise. While regular exercise caused a decrease in size (snout-to-vent length, head length and body mass), elimination of the capacity for R-L cardiac shunt did not greatly reduce animal growth, despite a chronic ventricular enlargement in surgically altered juvenile alligators. We speculate that, despite being slightly smaller, alligators with an occluded LAo would have reached sexual maturity in the same breeding season as control alligators. This study suggests that crocodilian R-L cardiac shunt does not provide an adaptive advantage for juvenile alligator growth and supports the logic that cardiac shunts persist in crocodilians because they have not been selected against. Supplementary material available online at

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Section: Confirmation Of Chronic Occlusion Of Laomentioning

confidence: 99%

Turning crocodilian hearts into bird hearts: growth rates are similar for alligators with and without right-to-left cardiac shunt

Eme

Gwalthney

Owerkowicz

et al. 2010

Journal of Experimental Biology

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“…In October to December 2007, alligators were killed (N24), and the presence or absence of communication between the LAo and RAo through the FoP was determined using a H 2 -electrode technique (Clark et al, 1960;Hicks and Comeau, 1994;Malvin et al, 1995). Animals were fasted for between 2 and 6 days before experimentation.…”

Section: Confirmation Of Chronic Surgical Occlusion Of Lao and Intravmentioning

confidence: 99%

“…The H 2 -electrode technique was used to demonstrate flow from the RV to LAo, through the foramen of Panizza and into the RAo (Clark et al, 1960;Hicks and Comeau, 1994;Malvin et al, 1995). Blood flow from both the LV and RV to the RAo was demonstrated for all animals in both groups.…”

Section: Chronic Surgical Occlusion Of Lao -Diving Groupmentioning

confidence: 99%

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Surgical removal of right-to-left cardiac shunt in the American alligator(Alligator mississippiensis) causes ventricular enlargement but does not alter apnoea or metabolism during diving

Eme

Gwalthney

Blank

et al. 2009

Journal of Experimental Biology

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All crocodilians have complete anatomical separation between the right and left ventricles, which is similar to birds and mammals and unlike all other non-avian reptiles. However, the crocodilian heart retains two systemic aortae (left aorta and right aortic arch), a feature that is common to all non-avian reptiles. In crocodilians, the left aorta (LAo) emerges from the right ventricle (RV) alongside the pulmonary artery (PA), and the right aortic arch (RAo) emerges from the left ventricle (LV) (Webb, 1979). This anatomical arrangement results in the capacity for a 'right-to-left' (R-L) cardiac shunt, a 'pulmonary bypass' cardiac shunt, in which a fraction of systemic venous blood recirculates into the systemic arterial circulation (Hicks, 1998).The crocodilian RAo and LAo communicate at two distinct points. As the aortae emerge from the heart, they run side-by-side, sharing a common wall for several centimetres. Near the base of this common wall and just downstream of the aortic valves, there is a small opening called the foramen of Panizza (FoP) (Panizza, 1833), which is of variable calibre and allows for potential blood flow between the RAo and LAo (Grigg and Johansen, 1987;Axelsson et al., 1996;Axelsson and Franklin, 2001). The second point of communication between the aortae is an arterial anastomosis in the abdominal cavity, caudal to the liver. Beyond this anastomosis, the RAo continues as the dorsal aortal, and the LAo becomes the coeliac artery, which gives rise to smaller arteries that supply most of the blood flow to the gastrointestinal tract. Consequently, the LAo is the primary source of blood for the splanchnic circulation, although blood from the RAo can also enter the splanchnic bed via the anastomosis (Axelsson et al., 1991).R-L cardiac shunt has been hypothesised to be important in various activities and physiological functions (Hicks, 1998;Hicks, 2002). For semi-aquatic reptiles like crocodilians, generation of a R-L cardiac shunt has often been observed during breath-holds associated with diving (White, 1969;Grigg and Johansen, 1987;Hicks and Wang, 1996). The reduction in pulmonary blood flow during apnoea has been hypothesised to conserve lung O 2 stores and sequester CO 2 away from the lung, possibly extending aerobic dive times (White, 1978;White, 1985;Grigg and Johansen, 1987). The development of a R-L cardiac shunt also results in arterial desaturation through admixture of venous blood, and the resulting systemic hypoxemia can trigger tissue hypometabolism, which could contribute to the prolongation of aerobic dives (Hicks and Wang, 1999;Platzack and Hicks, 2001).Crocodilians provide an opportunity to investigate experimentally the proximate functions of reptilian cardiac shunting. Their cardiac anatomy lends itself to surgical modification that prevents R-L cardiac shunt while maintaining the integrity of the ventricular chambers, a procedure that is not possible in other reptiles. The purpose of the present study was to test the hypotheses that removal of shunt (occlusion of LAo) woul...

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“…Clark and co-workers 70 have threaded the platinized arterial detecting electrode under fluoroscopic control into the aorta via an exposed radial artery for this procedure. The technic requires that the electrode lie free in the blood stream away from the vessel walls, hence the preference for the aortic detecting site.…”

Section: Ethyl Iodide and Methyl Iodide-ethylmentioning

confidence: 99%

Indicators and Detectors in Circulatory Dilution Studies and Their Application to Organ or Regional Blood-flow Determination

Fox

1962

Circulation Research

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Detection of Right-to-Left Shunts with an Arterial Potentiometric Electrode

Cited by 44 publications

References 1 publication

Turning crocodilian hearts into bird hearts: growth rates are similar for alligators with and without right-to-left cardiac shunt

Turning crocodilian hearts into bird hearts: growth rates are similar for alligators with and without right-to-left cardiac shunt

Surgical removal of right-to-left cardiac shunt in the American alligator(Alligator mississippiensis) causes ventricular enlargement but does not alter apnoea or metabolism during diving

Indicators and Detectors in Circulatory Dilution Studies and Their Application to Organ or Regional Blood-flow Determination

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