Changes in diastolic time with various pharmacologic agents: implication for myocardial perfusion.

Area of Science:

• Cardiology
• Pharmacology
• Physiology

Background:

• Diastolic time (DT) is crucial for coronary blood flow, particularly in conditions like coronary artery disease and left ventricular hypertrophy.
• Percent diastole (%D), calculated as (RR-QS2)/RR * 100, is a key indicator of diastolic function and varies nonlinearly with heart rate (HR).

Purpose of the Study:

• To investigate the effects of common cardioactive agents on percent diastole (%D) in normal subjects.
• To determine whether these drugs influence %D by altering heart rate (HR) or electromechanical systole (QS2).

Main Methods:

• Five groups of normal subjects received different cardioactive agents: propranolol, dobutamine, Cedilanid-D, isoproterenol, and lidocaine.
• Measurements included RR interval (cycle length) and QS2 (electromechanical systole) to calculate %D.
• Statistical analysis was performed to assess significant changes in %D.

Main Results:

• Propranolol and Cedilanid-D significantly increased %D by slowing HR and/or shortening QS2.
• Dobutamine increased %D primarily by shortening QS2.
• Isoproterenol significantly decreased %D despite shortening QS2 due to increased HR.
• Lidocaine had no significant effect on %D.

Conclusions:

• Cardiovascular drugs can significantly impact the relative duration of diastole (%D) through effects on heart rate and/or systolic duration.
• These findings have potential clinical implications for managing patients with conditions where diastolic filling is critical for coronary perfusion.