Kan optimal pacemakerfrekvens bestämmas på bakgrund av BNP? : En pilotstudie

Abstract

ABSTRACT Background Pacemaker is a well established alternative in treatment of patients with arrhythmic cardiac disease. Programming of the pacemaker is based on registered data of heart activity from the pacemaker as well as clinical experience. In general it is considered that a heart with mild affection of arrhythmic disease have the potential to give a more satisfying ejection fraction and therefore can tolerate a relatively low heart frequency in comparison to a heart that is more severely affected of arrhythmic disease and therefore demands a higher frequency. If the pace is inadequate the heart is in risk of asthenia. However, excessive pacing may result in unnecessary cardiac load and potential of further heart disease. Brain natriuretic peptide (BNP) is a hormone mainly produced by myocard. The production is stimulated by stretch in myocardial cells, and the physiological effects are reduced blood pressure and venous return. Pro-BNP is the precursor of BNP and NT-proBNP which is produced in equal amounts as a result of cleavage. NT-proBNP has no physiological effect. Both BNP and NT-proBNP is measurable in blood and show elevated values in patients with cardiac overload. In clinical practice the peptides are used for evaluation of heart failure. Objective This clinical trial investigates if BNP has a potential use in clinical evaluation of optimal pacemaker programming for the individual patient. We hypothesized that there is an inverse relationship between NT-proBNP in plasma and ejection fraction, physical function and quality of life. We further hypothesized that a group of patients with high values of NT-proBNP may benefit from faster pacing, and then demonstrate a reduction in NT-proBNP in plasma in addition to improvement in the heart´s contractile function, physical function and quality of life assessed by a questionnaire. Methods Included patients are a group with permanent atrial fibrillation and symptomatic reduced heart function treated with an iatrogenic AV-block and pacemaker implantation. The clinical trial is divided into two parts with part A being a cross-section study where the included patients baseline register NT-proBNP, ejection fraction by echocardiography, 6-minute walking test and quality of life measured by questionnaire SF-36. Part B of the clinical trial is an intervention study, that will take place if Part A show significant results, where we include the ten patients from Part A with the highest level of NT-proBNP. The intervention is to program the pacemaker to a frequency of 80 beats per minute for three weeks time and thereafter perform the same registrations as in baseline. Discussion and conclusion The two parts of the study constitute a pilot study investigating BNP and its effect in pacemaker patients. Part A give the opportunity to relate BNP to the other parameters in baseline in addition to the selective function for suitable patients included in Part B. In Part B there is potential for evaluation of BNP related to an increase in pacemaker frequency and the objective effect of the heart. If BNP show significant results it may justify a larger study with pacing periods with various pacing rates in a randomized sequenced and measure BNP as part of the clinical evaluation in finding the optimal pacing rate for the individual patient.