Neuroendocrine and haemodynamic changes in single-lead atrial pacing and dual-chamber pacing modes.

Objectives: Neuroendocrine and haemodynamic changes were compared between single-lead atrial (AAI) or dual-chamber (DDD) pacing modes in patients with sick sinus syndrome, in a crossover study. Methods: Inpatients scheduled for their first pacemaker implantation were screened for the following inclusion criteria: sick sinus syndrome; intact atrioventricular conduction; normal QRS interval. All study patients were implanted with a dual-chamber pacemaker, programmed for AAI or DDD pacing mode. Patients were allocated randomly to AAI followed by DDD pacing or to DDD followed by AAI pacing, each mode being applied for 72h. Echocardiographic, electrocardiographic and neuroendocrine parameters were tested at the end of each pacing mode. Results: From 152 inpatients screened for inclusion, 28 were selected for treatment. Plasma levels of atrial natriuretic peptide (ANP), endothelin, aldosterone and angiotension II were significantly lower, and aortic flow velocity-time integral was significantly higher, in AAI mode than in DDD mode. Aortic pre-ejection interval, interventricular mechanical delay and QRS duration were significantly higher in DDD than in AAI mode. Conclusions: In patients with sick sinus syndrome, DDD pacing mode can induce neuroendocrine system activation, and left ventricular dysfunction and dyssynchrony. These findings discourage the routine use of DDD pacing in patients with sick sinus syndrome.