Effects Of Alternative Pacing Mode On Patients With Sick Sinus Syndrome

ObjectiveSick sinus syndrome (SSS) is the most frequent type of bradyarrhythmia which takes up about 50%. Patients with SSS have the symptoms such as dizzy spells, amaurosis, syncope, palpitation, short breath and so on which are related with low grade cardiac output. In patients with SSS , normal atrioventricular ( AV ) conduction, and no bundle branch block, the above - mentioned bradyca-dia related sympotoms can be treated successfully with any pacemaker — a single chamber atrial ( AAI) pacemaker, a single chamber ventricular ( VVI) pacemaker , or a dual chamber ( DDD) pacemaker. However, it is still in study which pacing mode can bring patients with SSS the most benefit. The purpose of this study was to analyse the influnce of alternative pacing mode on cardiac function and atrial arrhythmia of patients with sick sinus syndrome, and then to offer the evidenve for further instructing treatment and selecting the optimal pacing mode.Methods1. Object of study:53 patients with sick sinus syndrome were implanted DDDR pacemakers which were randomly controlled alternative pacing mode. All the patients who were going to accept the pacemaker implantation were selected freely from The First Hospital Affiliated To China Medical University and Shen Yang Medical College Shen Zhou Hospital during the period from January 2004 to February 2005. They were AAIR(8 patients) , DDDR with short rate adaptive AV delay(DDDR -S) ( 11 patients) , DDDR with a fixed long AV delay ( DDDR - L) (llpatients) and VVIR(23 patients) respectively. Among them, patients selecting VVIR pacing mode were divided into two groups on the basis of the percentage of ventricular pacing(VP% ) : VVIR( VP% <50% ) (8 patients) and VVIR( VP% > 50% ) (15 patients) .2. Instruments:HP SONOS 5500 Echocardiographic Imaging System (HEWLETL PACKARD Co. USA)Delmar485 Holter (DELMAR Co. USA)Kenz 1210 Electrocardiograph (KENZ Co. Japan)Pacemaker Program - Controlled Instrument (MEDTRONIC Co. USA, ST. JUDE Co. USA, BIOTRONIC Co. Germany)DDDR pacemaker ( MEDTRONIC Co. , ST. JUDE Co. , VITATRON Co. , USA, BIOTRONIC Co. Germany)Atrial lead (MEDTRONIC Co. , ST. JUDE Co. , VITATRON Co. , USA, BIOTRONIC Co. Germany)Ventricular lead (MEDTRONIC 'Co. , ST. JUDE Co. , VITATRON Co. , USA, BIOTRONIC Co. Germany)3. Procedures: Postoperative patients were followed up in three month, six month and twelve month respectively. We collected information about medical history, physical examination and gave electrocardiograph, echocardiography, pacemaker condition examination and recorded patients ' symptoms, physical sign , cardiac function, the incidence of atrial arrhythmias and pacemakers working condition.4. Statistical analysis;Statistical analysis was performed by using SPSS 13. 0. Results were expressed as mean ± SD for continuous variables. Continuous variables were compared by using analysis of variance At test and nonparametric test. P value <0. 05 was required for statistical significance.Results1. There were no significant differences in demographic data and clinicalcharacteristic in five groups: AAIR, DDDR - L, DDDR - S, VVIR( VP% < 50% ) and VVIR( VP% > 50% ) (P > 0.05 ).2. The bradycardia related symptoms disappeared or relieved in all patients selected.3. The effect of alternative pacing mode on cardiac function: Five groups CO increased obviously after operation comparing with theirs before operation ( P< 0.05 respectively) .CO:AAIR(4.93 ±0.43L/min vs 3.08 ±0.61L/min) ,DDDR-L(4.70 ± 0. 54L/min vs 2. 97 ±0. 52L/min) ,DDDR - S(4.58 ±0. 35L/min vs 2. 95 ±0. 84L/min) , VVIR( VP% <50% ) (4. 02 ±0. 57L/min vs 3. 02 ±0. 72L/min) and VVIR( VP% >50% ) (3.97 ± 0. 61L/min vs 3. 05 ± 0. 45L/min) ( P < 0. 05 respectively).LVEF increased obviously in groups after operation comparing with theirs before operation: AAIR, DDDR -L and DDDR - S.LVEF: AAIR(59.64±6.85% vs 54. 61 ±7.43% P <0. 05) ,DDDR - L (58.26 ±7. 83% vs 55.02 ±5.64% P<0.05) and DDDR-S(56.82 ±4.3% vs54.31 ±7.3% P<0.05).LVEF in VVIR( VP% <50% ) increased slightly after operation comparing with its before operation, but there was no significant statistical difference ( P > 0.05).Whereas, LVEF in VVIR(VP% >50% ) decreased obviously after operation comparing with its before operation(50.40 ± 12.90 % vs55.03 ±6. 05 % P <0.05).There were significant differences on the ratio of E/A in AAIR, DDDR — L, DDDR - S and VVIR ( VP% > 50% ) by self - control study ( P < 0. 05 respectively) : AAIR(1.19±0.23 vs 1.06 ±0.18 P <0.05) , DDDR -L( 1.17 ±0.32 vs 1.09 ±0.28 P<0.05), DDDR-S(0.92 ±0.23 vs 1.03 ±0.12 P <0.05)and VVIR(VP% >50% ) (0.83 ±0.24 vs 0. 99 ±0.17 P<0.05). A-mong them, the ratio of E/A increased after operation in AAIR and DDDR - L, and went down after operation in DDDR - S and VVIR( VP% >50% ). The ratio of E/A in VVIR( VP% <50% ) decreased slightly after operation, but there was no significant statistical difference (P >0. 05).Postoperative LAD in VVIR(VP% >50% ) expanded obviously (36.96 ± 4. 12mm vs 34. 92 ± 3. 49mm P < 0. 05 ) . Postoperative LAD became shorter slightly in AAIR and DDDR - L, and became longer slightly in DDDR - S and VVIR( VP% <50% ) , but there were no significant statistical differences ( P > 0.05).4. The effect of alternative pacing mode on atrial arrhythmias: There were significant differences on the total time and the scoring of paroxysmal atrial arrhythmia after operation comparing with theirs before operation in four groups : AAIR (1.48 ±0.90 hours per month vs 3.35 ±2. 31 hours per month;3 vs 8, P <0. 05 respectively) , DDDR - L (1.92 ±0. 67 hours per month vs 3. 67 ±2. 88 hours per month;5 vs 10, P <0. 05 respectively) , DDDR - S (2. 06 ±0. 87hours per year vs 3.33 ±2. 40 hours per month;4 vs 9 , P < 0. 05 respectively) and VVIR( VP% >50% ) (3. 69 ±2. 78 hours per month vs 3. 07 ±2. 36 hours per month;13 vs 9, P <0.05 respectively). The amount of the above two variables in VVIR ( VP% > 50% ) increased slightly after operation , but there were no significant statistical differences( P >0. 05) .5. There were significant differences on the percentage of ventricular pacing between DDDR - L and DDDR - S ( P < 0. 01 ) . There were significant differences on the percentage of ventricular pacing between VVIR ( VP% < 50% ) and VVIR( VP% > 50% ) ( P <0.01) .Conclusions1. Alternative pacing mode could increase CO and improve bradycardia related symptoms successfully.2. Both atrioventricular unsequential contraction and the unsynchronous contraction between the left and the right ventricle could promote the expanding of LAD.3. The unsynchronous contraction between the left and the right ventricle could deteriorate cardiac function.4. Atrial arrhythmia could be inhabited for atrioventricular sequential contraction and be promoted for unsynchronous contraction between the ventricles.5. AAIR pacing mode was better than other pacing modes in the effects on cardiac function and atrial arrhythmia. There was a little probability to appear AV Block after operation in patients with sick sinus syndrome selecting AAIR pacing mode. AAIR could improve cardiac function and relieve atrial arrhythmi-a.6. DDDR could improve cardiac systolic function, relieved atrial arrhythmia, but showed different results in cardiac diastolic function in the two subgroups of DDDR ( DDDR - L and DDDR - S). DDDR - L could improve it, whereas, DDDR - S could deteriorate it.7. VVIR(VP% < 50% ) could improve cardiac systolic function, meanwhile , it didnt perform obviously passive effect on diastolic function and atrial arrhythmia. VVIR(VP% >50%) could improve cardiac systolic function, but it could deteriorate diastolic function and promote the development of atrial arrhythmia.