Respiratory modulation of cardiac time intervals.

Area of Science:

• Cardiology
• Physiology

Background:

• Cardiac cycle timing is crucial for cardiovascular function.
• Understanding respiratory influences on cardiac intervals is important for clinical assessment.

Purpose of the Study:

• To investigate the impact of respiration on systolic and diastolic time intervals.
• To examine the relationship between respiratory phases and cardiac timing in healthy individuals.

Main Methods:

• Simultaneous recordings of phonocardiograms, carotid pulse, echocardiograms, and respiratory curves in 25 healthy subjects.
• Assessment of cardiac cycle positioning relative to respiration.
• Analysis of heart rate and cardiac time interval dependency on respiration, with RR interval corrections.

Main Results:

• Heart rate exhibited clear variation across the respiratory cycle.
• Systolic time intervals demonstrated a stronger respiratory dependency than diastolic intervals.
• Inspiration led to decreased left ventricular ejection time and increased pre-ejection and isovolumic contraction times, suggesting increased afterload.

Conclusions:

• Respiratory variations influence both systolic and diastolic cardiac time intervals.
• Inspiratory effects on systolic intervals support the role of afterload in left ventricular systolic function.
• Left ventricular filling time is primarily affected by inspiration, with compensatory increases observed during transitions from expiration to inspiration.