Acute Changes in Left Atrial and Left Ventricular Diameters After Physiological Pacing

The present study examined alterations in left atrial diameter (LAD) and diastolic left ventricular diameter (LVDd) in 37 patients (72.2 +/- 9.8 years old) who received physiological pacemakers; 22 with atrioventricular (AV) block and 15 with sick sinus syndrome (SSS). After pacemaker implantation, LAD and LVDd were serially measured using echocardiography, and their diameters were expressed per body surface area (LADI and LVDdI; mm/m2). Pulmonary capillary wedge pressure (PCWP) and cardiac output (CO) were measured in ten patients with SSS and ten with AV block during both right ventricular and AV sequential pacing. After AV sequential pacing, CO increased in 19 of 20 patients (3.2 +/- 0.9 L/min to 3.9 +/- 1.0 L/min; P < 0.001). LADI decreased from 24.9 +/- 4.2 mm/m2 to 21.8 +/- 4.4 mm/m2 (P < 0.001) in 22 patients with AV block and from 24.1 +/- 3.4 mm/m2 to 20.4 +/- 3.8 mm/m2 (P < 0.001) in 15 SSS patients. However, LVDdI did not change significantly in either group of patients. The changes in LAD after the implantation of a physiological pacemaker occurred rapidly, i.e., LAD began to decrease within 1 minute after the procedure, and then reached a plateau. This plateau phase continued for at least 7 days during physiological pacing. There was a positive correlation between the changes in LADI after pacemaker implantation and those in PCWP observed during the AV sequential pacing performed prior to the implantation (r = 0.86; P < 0.001). The reduction in LAD following pacemaker implantation was rapid and seemed to be accompanied by improvement of cardiac function. Thus, it is suggested that the serial measurement of LADI is useful to predict the efficacy of physiological pacemaker implantation.