The Optimal AV Interval At Right Atrial Pacing With Different Frequencies And The Effect On Left Ventricular Cardiac Function After CRT Implantation

Objective: Chronic heart failure is the final destination of many kinds of cardiovascular diseases and the rate of hospitalization and mortality are high. The combined treatment of ACEI/ARB,beta blockers and diuretics might reduce mortality in patients with CHF,but the drug therapy of CHF has its limitations.Cardiac resynchronization therapy(CRT) becomes the important progress in the field of non-drug therapy in patients with CHF which might effectively improve the mechanical synchron of atrioventricular interventricular,intraventricular,so as to improve left ventricular function. At present CRT is usually administered with LV and BV stimulation in VDD mode, which pacing mode may in accordance with physiological features. But some patients with CHF maybe associated with sinus bradycardia.The main reason is that associated with sick sinus syndrome or use of beta blockers. CRT device usually be set to DDD mode after the implantation to patients with sinus bradycardia. It is important to find the optimal AV after CRT implantation.The aim of this study was to observe the changes of the optimal AV interval and the effects on LV cardiac function in patients at right atrial pacing with different frequencies after CRT implantation.Method: 15 patients with severe heart failure referred for CRT were entered,who were hospitalized in the Department of Cardiology of the second hospital of Hebei Medical University from December 2014 to December 2015, including 9 males and 6 females. Meet the following clinical criteria:(1) the clinical diagnosis of dilated cardiomyopathy or ischemic cardiomyopathy;(2) the NYHA functional classes III or IV;(3) LVEF less than or equal to 35%;(4) QRS duration is equal to or greater than 120ms;(5) in sinus rhythm. One case of ischemic cardiomyopathy, dilated cardiomyopathy in 14 cases.During 7-10 days after the implantation AV interval was optimized either at atrial sensing or at atrial pacing.Optimal AVdelay was defined as the AV delay that yielded the largest aortic VTI at tested AV intervals(between 80 and its PR interval). AT the same time, the left ventricular function parameters were measured at different AV intervals.Statistical analysis was performed using SPSS21.0 statical package.P <0.05 was considered statistically significant.Results:1 Comparison of the optimal AV interval among sinus rhythm and atrial pacing at different frequencies:1.1 There was no statistical significant difference in optimal AV interval among sinus rhythm and atrial pacing at different frequencies(P>0.05).1.2 There was no statistical difference in maximum AVTI during optimal AV interval among sinus rhythm and atrial pacing at different frequencies(P>0.05).2 Comparison of left ventricular function parameters at equal AV intervals among sinus rhythm and atrial pacing at different frequencies:2.1MVTI: There was a statistically significantly difference among sinus rhythm and atrial pacing at different frequencies at equal AV interval with a P-value of < 0.05. MVTI of the sinus rhythm group is better than the atrial pacing group at different frequencies.The interaction between heart rate and interval was statistically significant(P<0.05).2.2AVTI: There was a statistically significantly difference among sinus rhythm and atrial pacing at different frequencies at equal AV interval with a P-value of < 0.05. AVTI of the sinus rhythm group is better than that of atrial pacing group at different frequencies. The interaction between heart rate and interval was statistically significant(P< 0.05).2.3 QRS duration: No statistical significantly difference was found during equal AV interval among the three groups(P>0.05).The interaction between heart rate and interval was compared with statistical significance(P<0.05), heart rate and interval has interaction.2.4 Left ventricular strain: No statistical significantly difference was found at equal AV interval among the three groups(P>0.05). The interaction between heart rate and interval was statistically significant(P<0.05), heart rate and interval has interaction.Conclusion:1 The optimal AV intervals between sinus rhythm and atrial pacing at different frequencies were not significant different.2 The MVTI and AVTI of sinus rhythm were superior to those of right atrial pacing at different frequencies at equal AV interval.