Effects of E-Cigarette Vapor on Cardiovascular Function in Rats

• The study investigates the effects of chronic exposure to electronic cigarette (e-cig) vapor and traditional cigarette smoke on cardiovascular function.

• Increasing e-cig usage, especially among youths, necessitates understanding its long-term health implications despite being marketed as safer than traditional smoking.

Background and Methodology

Overview of the Study

• The study conducted by Charles River Laboratories and the National Institute of Aging.

• Rats of two age groups (young and old) were exposed to:

  • Purified air (control)

  • E-cigarette vapor with nicotine

  • E-cigarette vapor without nicotine

  • Traditional cigarette smoke

• Duration of exposure was 12 weeks using a nose-only inhalation system.

Measurement Techniques

• Echocardiography: To observe and measure heart function, including:

  • Left ventricular (LV) diastolic internal diameter

  • Systolic internal diameter

  • LV wall thickness (systolic and diastolic)

  • LV fractional shortening (cardiac pumping efficiency)

• Miller Catheter: Used to directly assess heart pressure, measuring:

  • Systolic and diastolic blood pressure

  • Heart rate

  • Maximum slope of LV systolic pressure increment/decrement

  • Tau (LV diastolic function)

• Thermodilation: To determine cardiac output via thermal dilution curves from cold saline injections.

End of Experiment Measurements

• After experiments, rats were euthanized to measure:

  • Body weight

  • Heart weight

  • Left and right ventricle weight

  • Tibial length

  • Postmortem LV volume

Results

Blood Pressure (Figure 1)

• Graph A: Blood pressure significantly increased in young rats exposed to traditional cigarettes compared to air; e-cig exposure (both types) did not significantly increase blood pressure.

• Graph B: No significant difference in blood pressure between air and e-cigarette exposure.

Heart Weight to Body Weight Ratio (Figure 2)

• Graph A: Young rats showed no significant differences among all exposure types.

• Graph B: Old rats exposed to nicotine-containing e-cigs had a higher heart weight to body weight ratio compared to those exposed to air.

Cardiac Function

• Limited significant differences noted in:

  • LV dimensions

  • Wall thickness

  • Cardiac output in both young and old rats across groups.

• E-cigarette without nicotine showed lower LV diastolic internal diameter compared to the cigarette smoke group.

Key Findings

• Young rats showed resilience against e-cig exposure, with no significant changes in cardiac metrics.

• Older rats displayed heart enlargement after exposure to nicotine-containing e-cig vapor, indicating potential long-term damage despite stable heart function.

Discussion and Conclusions

• Youth may not show immediate adverse effects from vaping, suggesting resilience but not guaranteeing safety.

• Older individuals might exhibit higher vulnerability to vaping-related damage, indicating that age factors into health risk assessments.

• Vaping, regarded as safer, can still contribute to cardiovascular risks, advocating for revision of health guidelines especially concerning nicotine exposure.

Quality of the Study

Pros

• Relevant research on e-cig usage impacts, particularly on cardiovascular health.

• Comprehensive assessment including control and varied exposure groups.

• Investigation of aging effects on cardiovascular response.

Cons

• Use of different rat strains raises potential genetic confounding variables.

• Limited twelve-week study duration potentially underestimated long-term effects.

• Lacked gender diversity in subjects, restricting generalizability of findings.

Future Research Directions

• Utilize uniform rat strains across age groups to minimize genetic variability.

• Extend study duration (6 months to 1 year) to observe chronic effects/diseases.

• Include both male and female subjects to assess hormonal impacts on cardiovascular function.