Comparative Studies on Temperature Effects upon the Electrocardiogram in some Vertebrates

Biörck, Gunnar; Johansson, Bengt W.

doi:10.1111/j.1748-1716.1955.tb01245.x

Cited by 38 publications

(26 citation statements)

References 8 publications

(3 reference statements)

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“…The means of the QRSn-amplitude did not show any significant maximum at a certain temperature. However, about half of the dogs in both Group A and Group B showed the typical pattern described by us (18,19). The maximum of the QRS amplitude was found to be at temperatures around 30°C.…”

Section: Resultsmentioning

confidence: 93%

Circulatory and Electrocardiographic Observations in Hypothermic Dogs treated with Phenylephrin

Johansson¹,

Hæger²,

Wallgren³

1961

Cardiology

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Section: Resultsmentioning

confidence: 93%

Circulatory and Electrocardiographic Observations in Hypothermic Dogs treated with Phenylephrin

Johansson¹,

Hæger²,

Wallgren³

1961

Cardiology

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“…The hibernator's heart has a relatively steep T wave at normal temperature. 23 Under certain conditions it may be described as a "T complex," based on its similarity to the QRS complex, rather than a T wave. 22,23 Alternatively, a T wave may be virtually lacking (see Figure 6 in Dawe and Morrison 22 and Figure 4 in Biürck and Johansson 23 ).…”

Section: Other Factors Relevant To Avoiding Arrhythmias: Future Researchmentioning

confidence: 99%

The hidden secrets of the hibernator’s heart may protect against arrhythmias

Heyden

Opthof

2005

Heart Rhythm

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In this issue of Heart Rhythm, Fedorov et al 1 describe the activation pattern and other electrophysiologic features of the heart of Citellus undulatus (also known as Spermophilus undulatus), the Siberian ground squirrel, both in summer active and in winter hibernating animals at temperatures varying from 3°C to 37°C and compared those with data in the rabbit heart as a nonhibernating species. The summary of the data can be simple. There is a substantial decrease in conduction velocity from 70 -80 cm/s in the Siberian ground squirrel at 37°C to 5-10 cm/s at 3°C. However, the conduction patterns remain normal and do not show areas of substantial conduction block, which might herald arrhythmias. Interestingly, conduction velocity was significantly higher in hearts obtained from winter hibernating animals than from summer active animals at both 37°C and 3°C. Data at such low temperatures cannot be obtained from the hearts in nonhibernating species such as the rabbit in the present study, but also not in man, because their hearts become quiescent or develop ventricular fibrillation at temperatures below 20°C. 1,2 Moreover, the authors show that there is an up-regulation of connexin43 (Cx43) in working ventricular myocardium of hibernating animals, in line with previous research, 3 and an appearance of connexin45 (Cx45) in working ventricular myocardium, although the expression of the latter normally is restricted to the conduction system. 4 This study underscores the presence of differences not only between hibernating and nonhibernating species but also between hibernating and nonhibernating individuals of the same species, with all the interesting implications for regulatory mechanisms. Physiologic background and implicationsWe would like to point out first that hypothermia impairs conduction velocity by a combined effect on the underlying membrane currents and on gap junctions. The conductance of gap junctions is reduced by about 70% when the temperature drops from normal to 0°C at least in cell pairs of neonatal rat heart. 5 Whether the inward Na ϩ current is operational at temperatures well below 10°C is questionable because it is seriously impaired at much smaller drops in temperature than those observed in hibernators. 6,7 Liu et al 8 reported that the L-type Ca 2ϩ current virtually disappears at 10°C in rat ventricular myocytes, although rat ventricle is relatively resistant against low temperature compared with other mammals. In contrast, the L-type Ca 2ϩ current has the same amplitude in hedgehog papillary muscle in the temperature range from 10°C to 35°C. 8 It is not possible to decide whether conduction remains intact, although impaired, in hibernators at temperatures well below 10°C because their membrane currents are relatively resistant against low temperature or because their gap junctions function better at low temperature compared with nonhibernators. Of note, in this study arrhythmias did not develop despite conduction velocities of 5 cm/s in the hearts from summer active animals at 3°C and conduc...

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“…One of the remaining differ ences, however, is the vulnerability of the human heart to ventri cular fibrillation at low body temperature (below 25cC), while that of the hedgehog seems to behave nicely all the way down. A closer scrutiny of the electrocardiogram of the hedgehog neverthe less reveals a zone between 15 and 22°C, where some disturbances are observed (1). There is therefore reason to compare the electro cardiograms of man and hedgehog in hypothermia as one way of approach to the safe-guarding mechanisms of the hibernators heart.…”

mentioning

confidence: 99%

“…During some years of experimental studies preparing for sur gery in hypothermia in humans, vve have been interested in the safe-guarding mechanisms of hibernators (1,2), who-as is well known-can survive for months with a body temperature of only a few centigrades above U°C, and yet wake up to a perfectly normal behaviour in a couple of hours. Our present experience with surgical closure of atrial septal defects in hypothermia, with exclusion of the circulation through the heart for several minutes (3,4), enables us to compare the electrocardiograms of man and hedgehog in conditions of low temperature and anoxia.…”

mentioning

confidence: 99%

The Influence of Anoxia on the Hypothermic Electrocardiogram of Hedgehog and Man

Biörck¹,

Johansson²

1957

Cardiology

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Comparative Studies on Temperature Effects upon the Electrocardiogram in some Vertebrates

Cited by 38 publications

References 8 publications

Circulatory and Electrocardiographic Observations in Hypothermic Dogs treated with Phenylephrin

Circulatory and Electrocardiographic Observations in Hypothermic Dogs treated with Phenylephrin

The hidden secrets of the hibernator’s heart may protect against arrhythmias

The Influence of Anoxia on the Hypothermic Electrocardiogram of Hedgehog and Man

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