LONG-TERM EFFECT OF VVI PACING ON ATRIAL AND VENTRICULAR-FUNCTION IN PATIENTS WITH SICK SINUS SYNDROME

We conducted a prospective, 6-month echocardiographic study on the eff ect of VVI pacing on left atrial and ventricular function and dimensio ns in patients with sick sinus syndrome. Thirty-nine patients (23 wome n and 16 men, aged 71.7 +/- 9.2 years; 30 in sinus rhythm and 9 in atr ial fibrillation) who had a VVI pacemaker implanted because of sick si nus syndrome were recruited in the study. In 26 patients who presented with and remained in sinus rhythm, paced left ventricular ejection fr action and stroke volume were significantly decreased (71.4% +/- 11.8% to 67.0% +/- 13.6%, and 73.9 +/- 29.0 cm(3) to 66.3 +/- 21.1 cm(3), r espectively, P < 0.001 for both), whereas the paced diastolic dimensio n of the left atrium was significantly increased (3.2 +/- 0.7 cm to 3. 7 +/- 0.9 cm, P < 0.001) at 6 months as compared with preimplantation. In nine patients with atrial fibrillation at implantation, paced left ventricular ejection fraction at follow-up was significantly decrease d (67.7 +/- 10.1% to 64.2% +/- 10.6%, P = 0.003), but paced stroke vol ume and left atrial diastolic dimension were not significantly changed (75.1 +/- 25.6 cm(3) to 79.0 +/- 22.7 cm(3), and 4.3 +/- 1.2 cm to 4. 6 +/- 1.5 cm, P = NS for both) at follow-up. Cessation of pacing and r estoration of sinus rhythm in 21 patients at follow-up did not result in any significant change of ejection fraction (67.5% +/- 10.2% to 67. 6% +/- 9.7%, P = NS) whereas stroke volume was increased (59.1 +/- 19. 6 cm(3) to 69.1 +/- 22.3 cm(3), P < 0.0001) in comparison with paced v alues. However, compared with preimplantation values, ejection fractio n was significantly decreased (70.4% +/- 10.0% to 67.6% +/- 9.7%, P = 0.001), whereas stroke volume was not significantly changed (68.4 +/- 22.3 cm(3) to 69.1 +/- 22.3 cm(3), P = NS) during sinus rhythm at foll ow-up. In 14 of those patients, discontinuation of pacing resulted in a significant increase of left atrial fractional shortening (8.1% +/- 1.7% to 20.1% +/- 4.3%, P < 0.001) and significant increase of left at rial diastolic dimension compared with paced and preimplantation level s (3.8 +/- 0.7 cm vs 3.6 +/- 0.7 cm and 3.0 +/- 0.5 cm, respectively, P < 0.001). Long-term VVI pacing in patients with sick sinus syndrome results in increase of the left ventricular end-systolic dimension and permanent reduction of the left ventricular ejection fraction, in the left atrium, VVI pacing causes an immediate reduction of the fraction al shortening as well as long-term increase of the diastolic dimension .