Max Ingemansson

Prediction of sinus rhythm maintenance following DC-cardioversion of persistent atrial fibrillation – the role of atrial cycle length

BackgroundAtrial electrical remodeling has been shown to influence the outcome the outcome following cardioversion of atrial fibrillation (AF) in experimental studies.The aim of the present study was to find out whether a non-invasively measured atrial fibrillatory cycle length, alone or in combination with other non-invasive parameters, could predict sinus rhythm maintenance after cardioversion of AF.MethodsDominant atrial cycle length (DACL), a previously validated non-invasive index of atrial refractoriness, was measured from lead V1 and a unipolar oesophageal lead prior to cardioversion in 37 patients with persistent AF undergoing their first cardioversion.Results32 patients were successfully cardioverted to sinus rhythm. The mean DACL in the 22 patients who suffered recurrence of AF within 6 weeks was 152 ± 15 ms (V1) and 147 ± 14 ms (oesophagus) compared to 155 ± 17 ms (V1) and 151 ± 18 ms (oesophagus) in those maintaining sinus rhythm (NS). Left atrial diameter was 48 ± 4 mm and 44 ± 7 mm respectively (NS). The optimal parameter predicting maintenance of sinus rhythm after 6 weeks appeared to be the ratio of the lowest dominant atrial cycle length (oesophageal lead or V1) to left atrial diameter. This ratio was significantly higher in patients remaining in sinus rhythm (3.4 ± 0.6 vs. 3.1 ± 0.4 ms/mm respectively, p = 0.04).ConclusionIn this study neither an index of atrial refractory period nor left atrial diameter alone were predictors of AF recurrence within the 6 weeks of follow-up. The ratio of the two (combining electrophysiological and anatomical measurements) only slightly improve the identification of patients at high risk of recurrence of persistent AF. Consequently, other ways to asses electrical remodeling and / or other variables besides electrical remodeling are involved in determining the outcome following cardioversion.

Modification of intrinsic AV-nodal properties by magnesium in combination with glucose, insulin, and potassium (GIK) during chronic atrial fibrillation

OBJECTIVE To explore the effects of MgSO4 in combination with glucose, insulin, and potassium (GIK) on intrinsic AV-nodal properties during chronic atrial fibrillation. METHODS The study included two patient groups--(a) control and intervention and (b) intervention--with different infusion times and concentrations of MgSO4. Ambulatory electrocardiographic recordings were analyzed using modified heart-rate stratified histogram (HRSH) analysis allowing detailed observation of the RR distribution at different average heart rate levels. The two RR-interval populations observed in most patients were characterized by analyzing the relationship between the summits of the peaks of the bimodal histograms. RESULTS A bimodal RR distribution with a shorter and a longer RR-interval population was observed in 9 of 11 (control), 9 of 11 (intervention) in group (a), and 11 of 13 in group (b) patients. No significant changes in the two RR populations were seen in the control registration (group a). There were, however, indications of a conduction delay in the longer RR intervals in group (a), which received a low concentration of MgSO4, when control was compared with intervention recordings. In group (b), receiving a high MgSO4 concentration, a conduction delay was seen in both the shorter and longer RR populations, being most pronounced for the longer RR population. CONCLUSION High MgSO4 levels caused a delay in both the shorter and longer RR intervals. The conduction delay in the longer RR population was most pronounced, indicating that MgSO4 differently affected the two corresponding AV-nodal pathways.

Effects of MgSO4 and glucose, insulin and potassium (GIK) on atrial conduction during the first 12 hours after DC-conversion of chronic atrial fibrillation

Objective - To investigate changes in atrial conduction induced by MgSO 4 and glucose, insulin and potassium (GIK) during the first 12-h period of sinus rhythm after successful DC-conversion of chronic atrial fibrillation (CAF). Methods - Signal-averaged P-wave duration, QRS-duration and PQ-time were recorded in 20 patients who were randomly assigned to control or intervention. Ten patients received no infusates (control group) and 10 patients received MgSO 4 and GIK infusions (intervention group). P-wave duration was determined from the X-, Y- and Zleads, which were further combined to obtain a spatial magnitude. P-wave morphology was studied by analysing global activation patterns and discrete components from the calculated spatial magnitude signal. Results - No changes in the measured parameters were seen in the control group. The P-wave duration, QRSduration and PQ-time increased from 139(13) [mean(SD)] to 149(15) ( p < 0.01), 90(7) to 94(9) ( p < 0.05) and 188(10) to 207(13) ms ( p < 0.01), respectively, after bolus infusion of MgSO 4 . The time from the start of the P-wave to its 1st and 2nd max. locations increased by 6 ms ( p < 0.01) in both cases after bolus infusion of MgSO 4 and had reversed after 10 h of MgSO 4 and GIK infusion. P-wave duration and PQ-time decreased after 10 h of MgSO 4 and GIK infusion, from 149(34) (bolus) to 138(12) and from 207(13) to 195(27) ms ( p < 0.05), respectively, in spite of an even higher serum Mg concentration at the end of this period. Conclusion - Bolus infusion of MgSO 4 2 h after DC-conversion of CAF produced an intra-atrial conduction delay that could be reversed by adding a GIK infusion, in spite of a concomitant increase in serum Mg concentration. No recovery of the intra-atrial conduction delay, seen after DC-conversion of CAF, was observed in either of the two groups during the 12-h study period.OBJECTIVE To investigate changes in atrial conduction induced by MgSO4 and glucose, insulin and potassium (GIK) during the first 12-h period of sinus rhythm after successful DC-conversion of chronic atrial fibrillation (CAF). METHODS Signal-averaged P-wave duration, QRS-duration and PQ-time were recorded in 20 patients who were randomly assigned to control or intervention. Ten patients received no infusates (control group) and 10 patients received MgSO4 and GIK infusions (intervention group). P-wave duration was determined from the X-, Y- and Z-leads, which were further combined to obtain a spatial magnitude. P-wave morphology was studied by analysing global activation patterns and discrete components from the calculated spatial magnitude signal. RESULTS No changes in the measured parameters were seen in the control group. The P-wave duration, QRS-duration and PQ-time increased from 139(13) [mean(SD)] to 149(15) (p < 0.01), 90(7) to 94(9) (p < 0.05) and 188(10) to 207(13) ms (p < 0.01). respectively, after bolus infusion of MgSO4. The time from the start of the P-wave to its 1st and 2nd max. locations increased by 6 ms (p < 0.01) in both cases after bolus infusion of MgSO4 and had reversed after 10 h of MgSO4 and GIK infusion. P-wave duration and PQ-time decreased after 10 h of MgSO4 and GIK infusion, from 149(34) (bolus) to 138(12) and from 207(13) to 195(27) ms (p < 0.05), respectively, in spite of an even higher serum Mg concentration at the end of this period. CONCLUSION Bolus infusion of MgSO4 2 h after DC-conversion of CAF produced an intra-atrial conduction delay that could be reversed by adding a GIK infusion, in spite of a concomitant increase in serum Mg concentration. No recovery of the intra-atrial conduction delay, seen after DC-conversion of CAF, was observed in either of the two groups during the 12-h study period.