Postextrasystolic pulsus alternans and heart rate

Area of Science:

• Cardiology
• Physiology

Background:

• Postextrasystolic (PES) pulsus alternans, characterized by alternating systolic blood pressure after premature ventricular contractions, has been observed in heart failure patients.
• Previous studies suggested a relationship between PES alternans and heart rate, but detailed mechanisms remained unclear.

Purpose of the Study:

• To investigate the relationship between heart rate and the occurrence and magnitude of postextrasystolic (PES) pulsus alternans in an acute animal model.
• To identify key physiological variables influencing PES alternans.

Main Methods:

• Acute animal study involving five open-chest dogs.
• Intrinsic heart rate was suppressed using vagal stimulation.
• Right ventricle was paced from 100-200 beats/min with premature ventricular stimuli introduced at 50% of the paced rate.

Main Results:

• PES alternans augmentation was observed up to a heart rate of 120 beats/min.
• Beyond 120 beats/min, the pressure of the second PES beat decreased by approximately 10 Torr for every 10 beats/min increase in rate.
• The duration of systole of the strong PES beat and the rapid diastolic filling rate of the weak PES beat were most closely related to PES alternans.

Conclusions:

• Postextrasystolic pulsus alternans is an inevitable consequence of heart rate and the interplay between ventricular ejection and diastolic filling.
• The manifestation and observation of alternans depend on the specifics of this relationship and the influence of disease states.