[Sinus node function of ischemic heart disease patients with chronotropic incompetence]

Area of Science:

• Cardiology
• Electrophysiology
• Internal Medicine

Background:

• Chronotropic incompetence (CI) is defined as an inadequate heart rate (HR) increase during exercise, affecting a significant portion of coronary patients.
• The underlying mechanisms of CI, particularly sinoatrial (SA) node dysfunction, require further elucidation in this population.

Purpose of the Study:

• To investigate the sinoatrial node function in coronary patients exhibiting chronotropic incompetence.
• To determine the electrophysiological basis of CI and its relationship with SA node conduction.
• To evaluate the utility of exercise testing as a screening tool for latent SA node dysfunction.

Main Methods:

• Esophageal atrial stimulation was performed on 256 coronary patients before and after drug-induced autonomic blockade.
• Adjusted sinoatrial node function time and sinoatrial conduction time were measured to assess SA node physiology.
• Exercise testing was utilized to identify patients with chronotropic incompetence (defined as inadequate HR augmentation).

Main Results:

• Forty-five patients (17.6%) demonstrated chronotropic incompetence during exercise testing.
• Electrophysiological studies indicated that abnormal sinoatrial rhythm was the primary determinant of CI in most affected patients.
• Specific electrophysiological parameters showed significant alterations related to SA node function and conduction.

Conclusions:

• Chronotropic incompetence in coronary patients is frequently associated with intrinsic sinoatrial node dysfunction, primarily abnormal sinoatrial rhythm.
• Sinoatrial node function testing, including adjusted SA node function time and conduction time, provides crucial insights.
• Rationed exercise testing serves as a valuable screening method for detecting latent weak sinoatrial node syndrome in coronary artery disease patients.