Effects of digitalis intoxication on pacemaker rhythm and synchronization in rabbit sinus node.

Area of Science:

• Cardiology
• Electrophysiology
• Pharmacology

Background:

• Digitalis toxicity can cause severe cardiac arrhythmias.
• Digitalis is known to induce electrical uncoupling in heart tissues.
• Arrhythmias may result from cell-to-cell uncoupling and pacemaker cell desynchronization.

Purpose of the Study:

• To investigate if digitalis-induced arrhythmias in the sinus node are mediated by cell-to-cell uncoupling.
• To examine the effects of ouabain on sinus node pacemaker activity and cell coupling.

Main Methods:

• Intracellular recordings from isolated rabbit sinus node preparations.
• Superfusion of sinus node tissue with ouabain (a digitalis glycoside) at toxic concentrations.
• Utilized whole sinus node and three-compartment bath preparations.

Main Results:

• Ouabain exposure increased spontaneous discharge, conduction delay, pacemaker shifts, and arrhythmias.
• Observed decreased interaction between pacemakers, leading to atrial arrest.
• Demonstrated increased electrical uncoupling and loss of synchrony between pacemaker cells.

Conclusions:

• Digitalis-induced sinus node arrhythmias result from cell-to-cell uncoupling and loss of synchrony.
• The observed arrhythmias are directly linked to impaired electrical communication between pacemaker cells.
• The pattern of arrhythmias can be predicted by the phasic interactions between pacemakers.