Purpose: There is growing evidence that only the highest achieved degree of biventricular pacing (BiVP), reaching 100%, from optimal LV lead position is correlated to the greatest reduction in total mortality and morbidity in selected heart failure (HF) patients (pts). There are several mechanisms leading to reduction of continuous BiVP in clinical practice. On the other hand the device reported degree of BiVP may be inaccurate. Aim of the study was to evaluate by 48h Holter monitoring the incidence of inefficient BiVP during effort in pts reported as exclusively BiV paced.
Methods: The study population consisted of 45 HF pts (9w, 36m), mean age 57±10 years, with dilated cardiomyopathy, in sinus rhythm, implanted with CRT-D for standard indications. Left ventricular lead was positioned in PL, L or AL CS veins. All pts received max treatment including carvedilol. Clinical evaluation was satisfactory. They underwent echocardiographic optimization of their VV and AV intervals. Algorithms for improvement of max BiVP were not activated. All pts underwent automatic device estimation of the BiVP degree which was reported as excellent. Four months post device implantation they underwent accurate estimation of BiVP percentage by 48h Holter monitoring while were encouraged to be active. The percentage of native, complete capture BiVP and fusion beats (template matched analysis) was defined manually by 2 operators. The degree of BiVP estimated by device and by 48h Holter monitoring were compared.
Results: Although device counters reported 48h BiVP ranging among 95-100%, in 9 pts Holter monitoring revealed inferior effective BiV pacing, especially during max exercise estimated as 75-85%. The main reason was transient loss of pure BiV because of faster intrinsic conduction beating the programmed AVD. Short runs of atrial tachyarrhythmias and PVCs were included in BiVP disruptive events.
Conclusions: In CRT pts optimal device programming in individual basis is very important aiming to maintenance of pure BiVP delivery not only at rest but also during exercise, where is most required. Additional workup is needed for accurate estimation of its efficacy apart from overestimated device data.