Effect of Dual-Chamber Pacemakers with Various Atrioventricular Intervals on Systolic Function, Diastolic Function, and Plasma Level of NT-pro BNP in a Sample of Iraqi Patients
Keywords:DDD pacemaker, NT-proBNP, atrioventricular interval (AVI), A-wave truncation.
Background: The use of dual-chambers (DDD) pacemakers is steadily increasing a year after year and one
of the programmable settings for these pacemakers is the duration of the atrioventricular interval (AVI).
AVI manipulation is justified for a variety of reasons including better hemodynamic stability and extending
the battery life of the pacemaker. Since plasma NT-proBNP level reflects the myocardial wall tension, we
hypothesized that different durations of AVI may have an effect on cardiomoycytes stretch and myocardial
wall tension and hence an effect on plasma NT-proBNP level. So we tried to use plasma NT-proBNP as a
marker for that strain, if present. Also, we tried to explore the effect of DDD pacemakers on both the systolic
and the diastolic functions of the heart using conventional echocardiographic parameters.
Methods: 52 patients with permanent dual-chambers pacemaker were recruited. We exclude those with
heart failure, renal impairment, and major valvular or coronary vessels disease. All patients had a thorough
medical history and examination, ECG, echocardiography (2-D, M-mode, and Doppler) as well as blood
sampling for NT-proBNP. Based on the shape of their E-A waves by pulsed-wave Doppler of transmitral
flow, they were grouped in 3 categories. Group-A included those with truncated A-wave, group-B comprised
those with separated E and A waves, and group-C involved those with fused E-A waves with or without
diastolic mitral regurgitation.
Results: there was statistically significant difference in the duration of AVI among the 3 groups (p <0.001)
with patients having fused E-A waves recorded the longest AVIs. Plasma NT-proBNP levels were significantly
higher when E-A waves were fused (p <0.001). The systolic parameters such as the cardiac output, the stroke
volume and the ejection fraction were higher when there was neither A-wave truncation nor E-A wave
fusion (p <0.001). All patients showed evidences of diastolic dysfunction.
Conclusion: despite the fact that DDD pacemakers are more physiological mode of pacing, nevertheless
they induce some grade of diastolic heart failure. Manipulating the AVI into longer than the device`s default
values should be carefully judged since it is associated with higher levels of plasma NT-proBNP levels that
reflect cardiac wall tension and strain which in turn may progresses in future into another cardiac problems
such as atrial fibrillation.
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