High Heart Rate in Pregnancy Is Modulated by Augmented Expression of an Ion Channel, HCN-2, in Pacemaker Tissue
Bibliographic record
Abstract
I t is established that in healthy human pregnancies, there are changes in cardiovascular status, including a significant (≈15%-20%) increase in resting heart rate. 1 Although the underlying mechanisms are not well understood, it has been suggested that this pregnancy-related elevation in heart rate may be mediated by increased efferent activity of and/or sensitivity to sympathetic stimulation, concurrent with decreased sensitivity of the heart to parasympathetic activity.2 This increased sympathetic stimulation may be a reflex response to the pregnancy-related decrease in total peripheral resistance and systemic vascular tone, consistent with the need to maintain arterial blood pressure.3 The elevation in resting heart rate is usually benign, although an increase in the incidence of ventricular arrhythmias may result.At present, both intrinsic (pacemaker activity or automaticity) and extrinsic (eg, adrenergic tone) reflex responses are being considered as proarrhythmic factors; however, there is no consensus concerning the underlying ionic mechanisms. Article see p 2009In this issue of Circulation, researchers in the Fiset laboratory at the Montreal Heart Institute report that in an adult mouse model, pregnancy is associated with a significant and selective upregulation of the so-called funny current (I f ) in the sinoatrial node or primary pacemaker region of the heart.4 The term funny was coined because this current is activated by hyperpolarization, as opposed to depolarization, of membrane potential.I f is modulated, that is, increased or decreased, by the autonomic transmitters norepinephrine and acetylcholine, respectively.5 It is carried mainly by Na + under physiological conditions.6 El Khoury et al 4 report that in pacemaker cells isolated from healthy pregnant adult female mice, I f is increased as a (Circulation.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.003 | 0.003 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".