Hypercapnia Attenuates Ventricular Ectopy during Wakefulness in a Young Man with Heart Failure
Bibliographic record
Abstract
Ventricular premature beats (VPBs) are common in heart failure (HF). Patients with HF often exhibit oscillations in breathing pattern (or Cheyne‐Stokes Respiration, CSR) that lead to increased VPBs during the hyperpneic phase. In such patients, CO 2 inhalation during sleep eliminates CSR and reduces VPB prevalence. Whether this VPB‐lowering effect of CO 2 occurs in awake HF patients without CSR remains unexplored. In a young CSR‐free HF patient (26 years; LVEF=20%; BMI=30 kg·m −2 ) with mild obstructive sleep apnea (AHI=17 events/h) and frequent ectopy, we compared the incidence of VPBs during: 1) resting breathing; 2) volitional hyperventilation; 3) and at standardized intervals (quartiles) during two CO 2 rebreathing tests with end‐tidal O 2 tension (P ET O 2 ) maintained at either 50 mmHg (hypercapnic‐hypoxia) or 150 mmHg (hypercapnic‐hyperoxia). Breath‐by‐breath ventilation, P ET O 2 , and P ET CO 2 were measured by flowmeter and rapid gas analyzer and ECG and O 2 saturation were monitored continuously. At rest (P ET CO 2 =39 mmHg) and during hyperventilation (P ET CO 2 =28 mmHg), VPBs occurred with 15% and 12% of all heart beats, respectively. With hyperoxic CO 2 rebreathing (P ET O 2 =148mmHg), as P ET CO 2 increased from 40, 46, 52, 57 mmHg in the first through fourth quartile, VPB incidence decreased from 11% to 6%, 3%, and 0%, respectively. Hypoxic rebreathing (P ET O 2 =51mmHg) showed a similar trend: VPB incidence fell from 9% at a P ET CO 2 of 40 mmHg to 0% at 46 mmHg and remained at 0% thereafter. The hypercapnia‐induced reduction in VPB frequency was not dependent on heightened ventilation: VPBs were evident during volitional hyperventilation (12%) but not during the CO 2 rebreathing quartiles with matched ventilation (0% for both hypoxia and hyperoxia). Furthermore, blood O 2 also did not appear to modulate this response: VPB incidence at rest (15%) was similar to both hypoxic (11%; O 2 saturation=86%) and hyperoxic (13%; O 2 saturation=99%) CO 2 rebreathing quartiles with matched ventilation (~9 L·min −1 ) and P ET CO 2 (~39 mmHg). These observations suggest that in HF, acute hypercapnia attenuates ventricular ectopy. The mechanism appears to be unrelated to increased respiratory or sympathetic drive, myocardial stretch accompanying large tidal volumes, or altered O 2 availability. How hypercapnia exerts anti‐arrhythmic effects remain uncertain; we hypothesize that CO 2 mediated increases in coronary flow may be involved. Support or Funding Information Experiments were funded by a Project Grant from the Canadian Institutes of Health Research (PJT 159491).
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 |
| 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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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".