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European Journal of Heart Failure 2006 8(6):615-620; doi:10.1016/j.ejheart.2005.12.001
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© 2005 European Society of Cardiology

Biventricular versus right ventricular pacing decreases immune activation and augments nitric oxide production in patients with chronic heart failure

Andrzej Rubaja,*, Piotr Rucinskia, Konrad Rejdakb,d, Krzysztof Oleszczaka, Dariusz Dumac, Pawel Griebd and Andrzej Kutarskia

a Department of Cardiology, Medical University of Lublin Poland
b Department of Neurology, Medical University of Lublin Poland
c Department of Clinical Biochemistry, Medical University of Lublin Poland
d Department of Experimental Pharmacology, Medical Research Center of the Polish Academy of Sciences Warsaw, Poland

* Corresponding author. E-mail address:arubaj{at}yahoo.com (A. Rubaj).


   Abstract
Top
 Abstract
1. Introduction
 2. Patients and methods
 3. Results
 4. Discussion
 References
 
Introduction: Immune system activation and oxidative stress are involved in the pathogenesis of heart failure (HF). We aimed to test the hypothesis that upgrading from right ventricular pacing (RVp) to biventricular pacing (BiVp) can counteract these phenomena.

Methods: 28 HF patients, with BiVp were switched to RVp for one week, and then returned to BiVp. Immediately prior to, and 48 h after the return to BiVp, left ventricular (LV) systolic function was evaluated by echocardiography, and serum N-terminal pro-brain natriuretic peptide (NTproBNP), C-reactive protein (CRP), tumor necrosis factor alpha (TNF-{alpha}), interleukin 6 (IL6), nitric oxide metabolites (NOx) and malondialdehyde (MDA) were assayed.

Results: LV systolic function significantly improved 48 h after switching from RVp to BiVp: Ao-VTI (p < 0.001), SV (p < 0.001) and CO (p < 0.001), and mitral regurgitation significantly decreased (p = 0.003). At the same time, indices of peripheral immune activation decreased: TNF-{alpha} (p = 0.02) and IL6 (p < 0.001). MDA decreased (p < 0.001), whereas NOx increased (p = 0.04). NTproBNP and CRP did not change. In addition, in "responders" (i.e. CO increase > 10% during BiVp vs. RVp) NTproBNP decreased and NOx increased. However, during BiVp, the decreases in TNF-{alpha}, IL6, and MDA occurred both in responders and in non-responders and were accompanied by a reduction in mitral regurgitation.

Conclusion: The beneficial effect of BiVp compared to RVp extends beyond improving cardiac haemodynamics and comprises a decrease in immune activation accompanied by an increase in serum NOx and decrease in serum MDA.

Key Words: Biventricular pacing • Chronic heart failure • TNF • IL6 • Nitric oxide

Received April 29, 2005; Revised September 21, 2005; Accepted December 5, 2005


   1. Introduction
Top
 Abstract
 1. Introduction
2. Patients and methods
 3. Results
 4. Discussion
 References
 
Persistent immune system activation, reflected by elevated serum proinflammatory cytokines, mainly TNF-P and interleukins (IL) 1 and 6, is one of the features of heart failure (HF) [1]. These cytokines, at concentrations usually present in the serum of HF patients have the potential to induce left ventricular (LV) dysfunction and remodelling, pulmonary oedema, cardiac cahexia and endothelial dysfunction [2,3]. Cytokine-driven mechanisms are thought to contribute significantly to heart failure progression, and the level of inflammatory activation is an important prognostic factor in HF. In fact, serum levels of IL-6, TNF-P and soluble TNF-P receptors are stronger predictors of mortality than traditional factors such as NYHA class, LV ejection fraction and maximal oxygen consumption [4].

Another important contributor to the development of HF is reduced nitric oxide bioavailability, which is related to endothelial dysfunction. It results from increased consumption of NO through reaction with superoxide anion radicals [5,6] and leads to impaired coronary and systemic perfusion, and reduced exercise capacity [7].

Since conduction disturbances are common, conventional DDD pacing utilising right ventricular apex pacing (RVp) had been evaluated in HF patients. Further observations and experimental studies have demonstrated that long-term RVp is associated with structural and functional changes in the myocardium leading to a deterioration in systolic function and worsening of HF symptoms [8,9]. However, biventricular pacing (BiVp) in patients with low ejection fraction and prolonged QRS duration has been shown to improve the quality of life and to reduce heart failure symptoms, hospitalisations and mortality. The benefit of BiVp may be related to improved LV systolic function, resynchronisation of cardiac contraction, reduction of mitral regurgitation and reverse remodelling [8-15].

It has not been determined whether BiVp is also associated with improvement in systemic inflammatory status. In the present study, we therefore aimed to determine the levels of chosen inflammatory markers in the serum of HF patients who were changed from RVp to BiVp. Serum indices of systemic oxidative stress (lipid peroxidation product malondialdehyde, MDA) and nitric oxide production (nitrates+nitrites, NOx) were also assayed.


   2. Patients and methods
Top
 Abstract
 1. Introduction
 2. Patients and methods
3. Results
 4. Discussion
 References
 
The study was conducted according to the guidelines of the Declaration of Helsinki, and the study protocol was approved by the Ethics Committee of the Medical University in Lublin. Each participant gave written informed consent.

Study participants were recruited from HF patients implanted with a biventricular pacing system. Criteria of implantation were as follows: (1) heart failure NYHA functional class III or IV, (2) left ventricular ejection fraction (LVEF) less than 40%, (3) QRS duration of ≥130 ms, (4) PQ duration of >150 ms. Patients were eligible to participate in the study provided that the pacing system had been implanted at least 4 weeks before the study and was functioning properly, and they were clinically stable. Patients were excluded if they had active infections, malignancies, collagen or inflammatory diseases, if they were cigarette smokers, or had used anti-inflammatory or immunosuppressive drugs within the two preceding weeks.

The study group consisted of 28 patients (23 male and 5 female, mean age 69.8 years, range 54-88 years) with a previously implanted biventricular pacing system (median time from implantation 5 weeks, range 1-16 months; 90 percentile: 7 weeks). In patients with sinus rhythm, atrio-ventricular pacing was applied using atrio-biventricular pacemakers (InSync III; Medtronic). In patients with chronic atrial fibrillation standard DDD (Axios D; BIOTRONIK) pacemakers were implanted with the atrial channel connected to the left ventricular lead and the ventricular channel to the right ventricular lead. The delay between RVp and LV pacing was set at 16 ms in InSync III and 15 ms in Axios D pacemakers and the LV was paced first.

Patients with sinus rhythm were paced in atrio-ventricular DDD mode. The energy delivered was programmed to be twice the pacing threshold. To eliminate variations of heart rate, and their influence on cardiac output and systolic function we permanently overdrove the intrinsic rate with a pacing rate of 10 beats per minute above spontaneous rhythm rate in each patient. AV delay was optimized in each pacing mode by means of the Ritter formula.

The rate in patients with chronic atrial fibrillation was set 10 bpm higher than mean ventricular rate in the last follow-up period (two patients had previous AV node ablation). The percentage of BiVp was higher than 80% in each patient with chronic atrial fibrillation during the study.

At the time of pacemaker implantation, 10 patients were in NYHA IV and 18 in NYHA III. The aetiology of heart failure was ischaemic in 13 and nonischaemic in 15 patients. 21 patients had sinus rhythm and 7 patients had chronic atrial fibrillation. Mean ejection fraction was 35±4%. Patients were on standard medical treatments consisting of ACE-inhibitors (90%), diuretics (86%), spironolactone (69%), digoxin (22%), beta-blockers (65%), aspirin (36%), amiodarone (20%) and oral anticoagulants (25%). Patients were kept on the same medication for at least 3 weeks before and throughout the study. All patients remained symptomatic but clinically stable throughout the entire study.

2.1. Study protocol
After implantation all pacemakers were set on the BiVp mode. At the start of the study pacemakers were reprogrammed to RV pacing for 7 days. At the end of this period the patients underwent evaluation which included assessment of NYHA class, physical examination, echocardiography, 12-lead ECG and routine blood tests (white cell count, haemoglobin, haematocrit, serum urea and creatine). For the biochemical assays, additional 10 ml samples of fasting blood were collected after at least 15 min of rest. Samples were centrifuged at 5000 rpm at 4 °C for 10 min and the serum was immediately frozen and kept at –80 °C until assay. The stimulation mode was then returned to BiVp. After 48 h of BiVp all tests were repeated. The patients were asked to fast for at least 12 h prior each blood sampling.

2.2. Echocardiography
Two-dimensional M-mode and Doppler echocardiography were performed using a Hewlett Packard ultrasound system (Sonos 5500) with 2.5 and 3.5 MHz electronic transducers. Left ventricular measurements were taken according to the current recommendations of the American Society of Echocardiography. A 2D echo was used to estimate EF according to the modified Simpson formula. The following parameters were measured or calculated: aortic velocity time integral (AoVTI), forward stroke volume (SV) defined as the product of AoVTI (averaged over five cardiac cycles) and cross sectional area of aortic annulus Ao={pi}2 (where r represents half of annular diameter), and cardiac output CO=SVxHR (where HR is the heart rate). Mitral regurgitation was expressed as area of colour Doppler regurgitation jet in four chamber projection.

2.3. Biochemical assays
All analyses were performed by laboratory staff blinded to the treatment status of the individual patients. CRP was measured by spectrophotometry (Semco SEc) using a commercial kit (Cormay CRP, Cormay, Poland).

TNF-P and IL6 were assayed with commercially available ELISA test kits according to the recommendations of the manufacturer (R&D, UK). NTproBNP was measured with a commercially available immunoassay kit (Roche Diagnostics, Germany). MDA was assayed with a high performance liquid chromatography (HPLC) system containing a C18 column (Supelco Discovery) and a UV-Vis detector set at 532 nm. The analytical procedure described by Draper et al. [16], with 1,1,3,3-tetraethoxypropane as the MDA standard was used. Concentration of NOx (NO2– and NO3–) was measured using the vanadium-based assay for simultaneous nitrite and nitrate measurement in biological specimens as described by Miranda et al. [17]. In short, vanadium is used to reduce nitrate to nitrite, which then reacts with Griess reagents. The reaction product is measured colorimetrically at 540 nm.

2.4. Statistical analysis
Calculations were performed using Statistica for Windows version 6.1 (Statsoft, USA) software. Data are expressed as means±SD. Because the distribution of data deviated from normal (tested by Shapiro-Wilk W test), to assess significance of differences in the parameters assayed and measured in different pacing modes, non-parametric Wilcoxon test for paired data and Mann-Whitney test for non paired data was used. Nonparametric correlation analyses: Spearman correlation and Kendall Tau statistic were used to calculate the correlation between measurements. Statistical significance was assumed at a level of p<0.05.


   3. Results
Top
 Abstract
 1. Introduction
 2. Patients and methods
 3. Results
4. Discussion
 References
 
Several parameters, namely systolic function indices, mitral regurgitation as well as TNF-P, IL6, NOx and MDA, significantly improved following the change in pacing mode from RVp to BiVp (Table 1). The remaining parameters did not change, although NTproBNP and CRP showed a tendency towards higher and lower levels, respectively.


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  		Table 1 Comparison of studied parameters between RV and BiV pacing modes

 
BiVp in relation to RVp was associated with an increase in diastolic filling time (DFT). E-wave deceleration time (EDT), early-to-atrial mitral peak flow velocities (E/A) ratio and isovolumetric relaxation time (IVRT) did not differ significantly between RVp and BiVp. We did no find any relationship between changes in basic indices of diastolic LV function (E/A ratio, E wave deceleration time, and IVRT) and the studied markers of inflammatory and oxidative stress.

To assess whether haemodynamic improvement determines improvement in inflammatory markers, the patients were retrospectively divided into two groups (responders and non-responders), on the basis of the magnitude of the change in CO which occurred after the switch from RVp to BiVp. Patients with more than a 10% increase in CO were classified as responders.

The data for responders and non-responders are shown in Table 2. Differences between these subgroups during BiVp comprised not only changes in systolic functional indices, but also a decrease in NTproBNP and an increase in NOx which only occurred in the responders. However, the decrease in IL6, TNF-P and MDA occurred in both responders and in non-responders and was accompanied by a reduction in mitral regurgitation in both groups, which was an unexpected finding.


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  		Table 2 Comparison of studied parameters between RV and BiV pacing modes in responders and non-responders

 
VTI, CO, CRP, NTproBNP, TNF-P, NOx, IL6, and MDA measured during RV pacing (baseline) did not differ between the responders and the non-responders.


   4. Discussion
Top
 Abstract
 1. Introduction
 2. Patients and methods
 3. Results
 4. Discussion
References
 
The results of the present study show that in HF patients, following pacing mode change from RVp to BiVp, systolic LV function indices rose significantly. This is in agreement with the observation that in HF patients upgrading of RVp to BiVp even for a short time may be haemodynamically beneficial [18]. We also found that changing the pacing mode from RVp to BiVp led to a significant decrease in serum concentrations of TNFP and IL6 which indicates that the mode of pacing may modulate the level of immune activation.

In HF patients, proinflammatory cytokines may be released from peripheral tissues affected by stagnant hypoxia and their production may be stimulated in response to endotoxins released by intestinal bacteria. A contributor to microcirculatory failure in HF may also be decreased availability of NO. The failing heart may generate TNF-P and IL6 as well, probably in response to end-diastolic ventricular wall stress and adrenergic activation [19]. The change of pacing mode from RVp to BiVp could suppress both peripheral and cardiac production of proinflammatory cytokines by improving haemodynamics and microcirculation.

Thus, the observations concerning the responders may easily be explained. The increases in CO might have alleviated stagnant tissue hypoxia through improvements in tissue perfusion. However, in non-responders systolic function indices, NOx and NTproBNP did not change. Nevertheless, mitral regurgitation and serum levels of the proinflammatory cytokines TNF-P and IL6 significantly decreased. This observation is suggestive not only of the improved haemodynamics as measured in the present study, but also that some other factor (or factors) are responsible for alleviation of systemic immune activation following upgrade of ventricular pacing.

It is worth noting that, besides IL6 and TNF-P, serum MDA was the other parameter measured in the present study which showed a slight but significant improvement (i.e., a decrease) both in responders and non-responders.

It is possible that changes in IL6 and TNF-P were in response to some improvement in systolic function, following pacing mode change from RVp to BiVp, which was below the threshold of detection of the methods used in the study. Reduction of mitral regurgitation may contribute to the observed reduction in inflammatory markers during BiVp [20]. However, we did not find any relation between reduction in mitral regurgitation jet area and changes in TNF-P and IL6 concentrations.

Importantly, there are data connecting mitral regurgitation, directly as well as indirectly, with increases in serum TNF-P [21,22]. It is, therefore, conceivable that following pacing mode change from RVp to BiVp a reduction of mitral regurgitation due to more accurate systolic synchronicity may result in decreased serum levels of TNF-P and IL6 independent of the haemodynamic improvements assessed by the methods employed in the present study.

Serum NTproBNP was significantly lower during BiVp, but only in the responders sub-group. The main stimulus for BNP synthesis and secretion is myocyte stretch. It seems likely that during BiVp in comparison to RVp, diastolic left ventricle wall stress became decreased which might improve endothelial function and increase NO production, hence NOx level. It is generally accepted that NOx (nitrate/nitrite) measurement reflects basal endogenous NO production [23], however careful controlling for other sources of NOx and renal excretion is necessary. Although it remained within generally accepted normal limits [24], NOx concentration was significantly higher during BiVp in comparison to RVp in responders but not in non-responders. The increase in NOx concentration in responders but not in non-responders suggests that improved physiological endothelial cell membrane shear stress induced by pulsatile blood flow enhancement along with higher CO and SV might increase endothelial NO synthesis [25,26].

4.1. Limitations
We used a short term observation period in stable patients for safety reasons and to minimize the influence of other confounding factors such as infections, and changes in diet and drugs. The method of MR assessment based on colour Doppler jet area measurement, although used in some large studies like MUSTIC and MIRACLE, is not precise, because it may be affected by technical and pathophysiological factors.

4.2. Conclusions
We conclude that the beneficial effect of BiVp in comparison to RVp extends beyond improving systolic efficacy and reduction of mitral regurgitation, and comprises a decrease in immune activation reflected by decreased serum concentrations of the major proinflammatory cytokines, TNF-P and IL6. The improvement in systolic efficacy which follows the pacing mode change from RVp to BiVp is coincident with an increase in serum NOx and decrease in serum NTproBNP level. However, decreases in IL6 and TNF-P level also occur in patients with mitral regurgitation but no improvement in systolic function detected by conventional echocardiographic methods. Since these cytokines are actively involved in cardiovascular maladaptive remodelling and the progression of HF, the effect BiVp may be of substantial clinical importance.


   References
Top
 Abstract
 1. Introduction
 2. Patients and methods
 3. Results
 4. Discussion
 References
 

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Upgrading from right ventricular pacing to biventricular pacing in pacemaker patients with chronic heart failure
Heart, January 1, 2008; 94(1): 102 - 107.
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