Sick sinus syndrome (SSS) is a clinical syndrome caused by lesions in the sinoatrial node and surrounding tissues. It results in impaired impulse formation and/or impulse conduction in the sinoatrial node, leading to arrhythmias (mainly sinus bradycardia, sinus arrest and sinoatrial block) and a series of clinical manifestations. At present, there is a lack of clinically effective therapeutic drugs for SSS. Common methods for establishing SSS animal models include cryoinjury, local injection, clamping, electrical cauterization and formaldehyde injury, among which the formaldehyde injury method is the most widely applied. Formaldehyde-induced sinoatrial node injury can be achieved by wet compressing the sinoatrial node area with formaldehyde-soaked gauze, or microinjecting a small dose of formaldehyde into the sinoatrial node using a microsyringe.

Japanese big-ear rabbits (male and female, body weight about 2 kg)
Modeling method: A formaldehyde-soaked cotton swab was placed on the sinoatrial node region along the detecting electrode and fixed for a certain period. The model was successfully established when the heart rate decreased by 30–50% indicated by electrocardiogram.
Evaluation indexes: heart rate detection, HE staining, Masson staining

Heart rate measurement

Myocardial tissue HE staining

Myocardial tissue Masson staining