UNLABELLED: In patients with atrioventricular dissociation associated with complete atrioventricular block or reverse synchronization and preservation of the sinus rhythm the atria are mechanically over-burdened by contraction in an inept stage of the cardiac cycle (against a closed atrioventricular valve). Prolonged overburdening leads to dilatation of the atria and a higher incidence of supraventricular arrhythmias incl. atrial fibrillation. The objective of the trial was to assess whether these changes are reversible.

METHOD: In 26 patients where atrioventricular dyssynchronization as the only detectable reason of atrial dilatation was eliminated by implantation of sequential atrioventricular stimulation, the authors investigated by echocardiography the dimensions, volumes and ejection fractions of the atria and left ventricle at baseline (A), after 24 hours following implantation (B), after 8 weeks (C), after one year (D).

RESULTS: Left atrium: during the first 24 hours diminution in the long axis occurred (AxB: -4.28, p = 0.023), the difference remained significant even after eight weeks (AxC: -6.1, p = 0.050). The ejection fraction was after eight weeks also significantly greater (BxC: +8.29, p = 0.039). Right atrium: within 24 hours the long axis was reduced (AxB: -4.70 p = 0.033), the difference was apparent also after 8 weeks (AxC: -5.60 p = 0.028). Within 8 weeks (AxC) the mean enddiastolic pressure diminished significantly (-11.01, p = 0.032) as well as the endsystolic volume (-9.01, p = 0.018, while the ejection fraction increased (+7.50, p = 0.031). The right ventricular volume during diastole increased between the 8th week and the check-up after one year (+6, -1, +17.77, p = 0.046). Left ventricle: the ejection fraction had a rising trend, after one year a significant difference was found as compared with the baseline value (AxD: +10.20%, p = 0.007) and as compared with the value assessed 8 weeks after implantation (CxD: +9.44%, p = 0.018). The change of the ejection fraction was inversely proportional to the value of the ejection fraction immediately after implantation (r -0.83, p < 0.01).

CONCLUSION: The authors provided evidence of the reversibility of the morphological and functional atrial damage and the favourable effect of atrioventricular synchronization on left ventricular function.