The electrocardiogram of European shrews

Nagel, Anne

doi:10.1016/0300-9629(86)90729-2

Cited by 12 publications

(11 citation statements)

References 18 publications

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“…Not all rodent ECGs, however, exhibit a J‐wave and the Capybara, the largest rodent on earth exemplifies this (Szabuniewicz et al, 2010). Additionally, in other small non‐rodent mammals, such as shrews and bats, J‐wave‐like deflections follow the QRS complex (Currie, 2018; Nagel, 1986). What the animals of these groups share are high heart rates.…”

Section: Introductionmentioning

confidence: 99%

High heart rate associated early repolarization causes J‐waves in both zebra finch and mouse

et al. 2021

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High heart rates are a feature of small endothermic—or warm‐blooded—mammals and birds. In small mammals, the QT interval is short, and local ventricular recordings reveal early repolarization that coincides with the J‐wave on the ECG, a positive deflection following the QRS complex. Early repolarization contributes to short QT‐intervals thereby enabling brief cardiac cycles and high heart rates. We therefore hypothesized high hearts rates associate with early repolarization and J‐waves on the ECG of endothermic birds. We tested this hypothesis by comparing isolated hearts of zebra finches and mice and recorded pseudo‐ECGs and optical action potentials (zebra finch, n = 8; mouse, n = 8). In both species, heart rate exceeded 300 beats per min, and total ventricular activation was fast (QRS < 10 ms). Ventricular activation progressed from the left to the right ventricle in zebra finch, whereas it progressed from apex‐to‐base in mouse. In both species, the early repolarization front followed the activation front, causing a positive J‐wave in the pseudo‐ECG. Inhibition of early repolarization by 4‐aminopyridine reduced J‐wave amplitude in both species. Action potential duration was similar between ventricles in zebra finch, whereas in mouse the left ventricular action potential was longer. Accordingly, late repolarization had opposite directions in zebra finch (left‐right) and mouse (right‐left). This caused a similar direction for the zebra finch J‐wave and T‐wave, whereas in the mouse they were discordant. Our findings demonstrate that early repolarization and the associated J‐wave may have evolved by convergence in association with high heart rates.

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Section: Introductionmentioning

confidence: 99%

High heart rate associated early repolarization causes J‐waves in both zebra finch and mouse

et al. 2021

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“…In human, ectopic pacing of the atria often originates from the pulmonary venous myocardium and this setting requires pulmonary vein isolation by catheter-ablation. While electrocardiograms have been reported for shrews (Morrison et al, 1959, Nagel, 1986, Vornanen, 1989, Jurgens et al, 1996, it is not known whether their extensive pulmonary venous myocardium associates with a propensity to develop atrial arrhythmias.…”

Section: Discussionmentioning

confidence: 99%

“…Whereas in human it takes one minute to circulate the entire blood volume, in a shrew it takes a few seconds (Schmidt-Nielsen, 1984). A key component of the prodigious circulation is the incredibly fast heart rate, which may exceed a thousand beats a minute in the smaller shrew species (Morrison et al, 1959, Nagel, 1986, Vornanen, 1992, Jurgens et al, 1996. In many mammals, a well-developed cardiac conduction system initiates in its sinus node the cardiac impulse that, after a slow propagation through the atrioventricular node, rapidly spreads throughout the ventricles via the His bundle, bundle branches and Purkinje fibers (Davies, 1942, Dobrzynski et al, 2013.…”

Section: Introductionmentioning

confidence: 99%

Anatomy of the Heart with the Highest Heart Rate

Chang

Sheftel

Jensen

2021

Preprint

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Shrews occupy the lower extreme of the seven orders of magnitude mammals range in size. Their hearts are large relative to body weight and heart rate can exceed a thousand beats a minute. To investigate whether cardiac traits that are typical mammalian scale to these extremes, we assessed the heart of three species of shrew (genus Sorex) following the sequential segmental analysis developed for human hearts. Using micro-computed tomography we describe the overall structure and find, in agreement with previous studies, a large and elongate ventricle. The atrial and ventricular septums and the atrioventricular and arterial valves are typically mammalian. The ventricular walls comprise mostly compact myocardium and especially the right ventricle has few trabeculations on the luminal side. A developmental process of compaction is thought to reduce trabeculations in mammals, but in embryonic shrews the volume of trabeculations increase for every gestational stage, only slower than the compact volume. By expression of Hcn4, we identify a sinus node and an atrioventricular conduction axis which is continuous with the ventricular septal crest. Outstanding traits include pulmonary venous sleeve myocardium that reaches farther into the lungs than in any other mammals. Typical proportions of coronary arteries-to-aorta do not scale and the shrew coronary arteries are proportionally enormous, presumably to avoid the high resistance to blood flow of narrow vessels. In conclusion, most cardiac traits do scale to the miniscule shrews. The shrew heart, nevertheless, stands out by its relative size, elongation, proportionally large coronary vessels, and extent of pulmonary venous myocardium.

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“…Not all rodent ECGs, however, exhibit a J-wave and the Capybara, the largest rodent on earth, exemplifies this (Szabuniewicz et al ., 2010). Additionally, in other small non-rodent mammals, such as shrews and bats, J-waves have also been found (Nagel, 1986; Currie, 2018). Despite the difference in phylogenetic origin, these small mammals all share high heart rates that drive the great cardiac output required to sustain their greater mass-specific metabolic rates (Lillywhite, Zippel and Farrell, 1999; Burggren, Farrell and Lillywhite, 2011).…”

Section: Introductionmentioning

confidence: 98%

The mechanism underlying J-waves and T-waves in the electrocardiogram of mice and zebra finches

Offerhaus

Snelderwaard

Faber

et al. 2020

Preprint

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Brief cardiac cycles are required to achieve high heart rates as seen in endothermic animals. A main determinant of the cardiac cycle is the repolarization phase of the cardiac action potential, which is visible in the ECG as a T-wave. In mammals with high heart rates – such as rodents – the repolarization phase is short and the ECG is characterized by a positive deflection following the QRS-complex, the J-wave. It is unclear whether birds with high heart rates show similar ECG characteristics. Here we study cardiac repolarization and the ECG in the zebra finch which has high heart rates. In ex vivo hearts of zebra finch (N=5) and mouse (N=5), pseudo-ECGs and optical action potentials were measured. In both species, total ventricular activation was fast with QRS durations shorter than 10ms. Ventricular activation progressed from the left to the right ventricle in zebra finch whereas the activation pattern was apex-to-base in mouse. In both species, phase 1 early repolarization followed the activation front, causing a positive J-wave in the pseudo-ECG. In zebra finch, late repolarization was directed from the right ventricle to the left ventricle, whereas late repolarization was directed opposite in mouse. Accordingly, on the zebra finch ECG, the J-wave and the T-wave have the same direction, whereas in the mouse the J-wave and the T-wave are discordant. Our findings demonstrate early repolarization and the associated J-wave are not restricted to mammals and that they also occur within birds. Early repolarization may have evolved by convergence in association with high heart rates.Summary statementZebra finches are small birds with high heart rates. Similar to small rodents, the zebra finch ECG contains a J-wave, which is caused by early repolarization

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The electrocardiogram of European shrews

Cited by 12 publications

References 18 publications

High heart rate associated early repolarization causes J‐waves in both zebra finch and mouse

High heart rate associated early repolarization causes J‐waves in both zebra finch and mouse

Anatomy of the Heart with the Highest Heart Rate

The mechanism underlying J-waves and T-waves in the electrocardiogram of mice and zebra finches

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