Effect of Ca2+ antagonists on mechanical function in the neonatal heart

Area of Science:

• Cardiovascular Physiology
• Neonatal Cardiology
• Pharmacology

Background:

• Verapamil and diltiazem are calcium channel blockers with known effects on cardiac function.
• Understanding age-related differences in drug response is crucial for pediatric pharmacology.

Purpose of the Study:

• To investigate the differential effects of verapamil and diltiazem on neonatal versus adult rabbit heart mechanical function.
• To elucidate age-dependent mechanisms of calcium handling in the heart.

Main Methods:

• Isolated arterially perfused neonatal and adult rabbit hearts were utilized.
• Mechanical function was assessed following administration of verapamil and diltiazem at various concentrations.
• Inotropic responses to staircase stimulation, hyperosmolarity, and paired electrical stimulation were evaluated.

Main Results:

• Neonatal hearts exhibited a significantly greater negative inotropic effect from verapamil and diltiazem compared to adult hearts.
• Resting tension increased in neonatal hearts but not adult hearts at specific drug concentrations.
• Both drugs inhibited staircase inotropy but did not affect hyperosmolarity-induced inotropy in either age group.
• The positive inotropy of paired electrical stimulation was abolished in neonates but not adults.

Conclusions:

• The neonatal heart is more dependent on transsarcolemmal calcium influx for contraction than the adult heart.
• Neonatal cardiac relaxation appears more reliant on transsarcolemmal calcium efflux compared to adult hearts.
• Age-specific differences in calcium handling influence the response to calcium channel blockers.