Doppler Echocardiography Evaluate Atrioventricular Period Hemodynamics In Patients With DDD Pacemakers

Objective:To evaluate the effects of various atrioventricular period (AVP) of DDD pacemakers on hemodynamics. Methods:51 patients have been studied with normal cardiac function in whom implanted DDD pacemaker. After programming the device in pacing both atria and ventricle mode at heart rate of 60 and 70 beats/min at rest respectively. Each beat was programmed 5 AVPs, 80-100-140-180-220ms. At the same time Doppler echocardiographic transmitral and transaortic blood flow and stroke volume(SV) were recorded. Results:As AVP increased from 80ms to 220ms, SV with 60 beats/min are 55±10ml, 59±14ml, 62±12ml, 57±13ml, and 48±10ml; with 70 beats/min are 56±llml, 61±12ml, 66±llml, 53±14ml, and 49±12ml respectively. Total mital flow velocity-time integral with 60 beats/min are 9.2±2.4cm, 9.9±1.8cm, 12.0±2.6cm, 10.2±2.3cm, 8.9±2.1cm; with 70 beats/min are 10.1±2.1 cm, 10.3±2.2 cm, 12.4±2.3cm, 11.0±2.4 cm,9.1±1.9 cm. Maximal SV and left ventricular(LV) filling flow were achieved top at the AW of 140ms with both rates. SV was maekedly reduced at AVP 220ms due to disturbed LV early diastolic filling and shortened LV filling time, or at AW 80ms due to aborted left atrial contraction. Following the AW prolonged from 80ms to 220ms, the onset of left atrial contraction gradually moved to the front of the ventricle electroactivity from the behind.Discussions:1.The optimal AVP: the AV delay required to achieve optimal AV synchrony varies irom patient to patient. All the patients have normal left ventricle function, the maximal SV occurs at AVP 140ms. However, in former references, the optimal AVPs differ from 100ms to 200ms at rest. The reason is that patients with normal LV function mixed up with LV dysfunction.2.Mechanism of hemodynamic by optimal AVP: the benefit of AV synchrony has closely relation with atrial systolic time. Whether atrial systolic cause optimal ventricular filling is important to Starling mechanism. The experiment also shows optimal atrial systolic cause LV end-diastole pressure and the elongation of cardiac fibers.Conclusions:Lin ODD pacemaker patients with normal cardiac function, optimized AVP at rest is 140ms both with 60 beats/min and 70 beats/m2.the hemodynamic effects of varying AW have closely relationship with the timing of atrial contraction, the LV filling time, and interaction between early and late ventricular diastolic filling.3. To achieve the maximal ventricular filling and cardiac output, optimized AVP should be individualized, and programming the timing of atrial contraction at 20ms prior to ventricle should be considered.