Acute and chronic changes in atrial natriuretic factor induced by ventricular pacing: a self controlled clinical trial

Neuroendocrine and haemodynamic changes in single-lead atrial pacing and dual-chamber pacing modes

OBJECTIVES

Neuroendocrine and haemodynamic changes were compared between single-lead atrial (AAI) or dual-chamber (DDD) pacing modes in patients with sick sinus syndrome, in a crossover study.

METHODS

Inpatients scheduled for their first pacemaker implantation were screened for the following inclusion criteria: sick sinus syndrome; intact atrioventricular conduction; normal QRS interval. All study patients were implanted with a dual-chamber pacemaker, programmed for AAI or DDD pacing mode. Patients were allocated randomly to AAI followed by DDD pacing or to DDD followed by AAI pacing, each mode being applied for 72 h. Echocardiographic, electrocardiographic and neuroendocrine parameters were tested at the end of each pacing mode.

RESULTS

From 152 inpatients screened for inclusion, 28 were selected for treatment. Plasma levels of atrial natriuretic peptide (ANP), endothelin, aldosterone and angiotension II were significantly lower, and aortic flow velocity-time integral was significantly higher, in AAI mode than in DDD mode. Aortic pre-ejection interval, interventricular mechanical delay and QRS duration were significantly higher in DDD than in AAI mode.

CONCLUSIONS

In patients with sick sinus syndrome, DDD pacing mode can induce neuroendocrine system activation, and left ventricular dysfunction and dyssynchrony. These findings discourage the routine use of DDD pacing in patients with sick sinus syndrome.

Serum markers of systemic right ventricular function and exercise performance

The right ventricle, which faces systemic pressure due to congenital heart disease, often develops premature systolic dysfunction. Cardiac hormones might be useful to identify patients with such systolic dysfunction. This prospective study investigated the relationship of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) levels with right ventricular ejection fraction (RVEF) and exercise performance in patients with a systemic right ventricle. ANP levels were obtained in 24 patients and BNP levels were obtained in 22 patients with systemic right ventricle. Patients underwent exercise study (n = 22) and cardiovascular magnetic resonance imaging (n = 11) or equilibrium radionuclide angiography (n = 13) to determine RVEF. There were 17 patients with complete transposition and 7 patients with corrected transposition. ANP showed an inverse correlation with RVEF (r2 = 0.63, p < 0.001), a weak but statistically significant inverse correlation with exercise duration (r2 = 0.18, p = 0.047) and no relationship with maximal oxygen consumption (peak V'O2) (r2 = 0.10, p = NS). BNP did not show a relationship with any of the parameters measured. ANP shows a strong inverse correlation with RVEF and a weak correlation with exercise duration in patients with a systemic right ventricle. BNP does not show a significant relationship when compared with either parameter. ANP might be a useful tool for identification of systolic right ventricular dysfunction.

The role of pacing mode in the development of atrial fibrillation

Asynchronous ventricular pacing has been shown to increase the risk of development of atrial fibrillation (AF) because of various mechanisms: retrograde atrioventricular (AV) conduction with increase in atrial pressure causing acute atrial stretch and reverse flow in the pulmonary veins, mitral regurgitation, reduced coronary blood flow, adverse neuroendocrine reactions, etc. Dual-chamber pacing preserves atrioventricular synchrony. However, in randomized multicentre trials comparing VVI(R) with DDD(R) pacing, AF is only slightly less frequent in the dual-chamber mode. This is most likely due to unnecessary ventricular pacing, which is frequent in dual-chamber pacing. At nominal values, dual-chamber devices usually do not permit intrinsic AV conduction but promote delivery of the ventricular stimulus at an inappropriate time in an inappropriate place. Programming of long AV delays facilitates spontaneous AV conduction but usually cannot completely avoid unnecessary ventricular pacing and causes other problems in the dual-chamber mode. Atrial septal lead placement can improve left-sided AV synchrony and promote spontaneous AV conduction. Programming of the AAI(R) mode is superior to the dual-chamber mode but cannot be used if AV conduction is impaired intermittently or permanently. Therefore, dedicated algorithms enhancing spontaneous AV conduction in the dual-chamber mode are desirable for a large proportion of pacemaker patients.

Natriuretic peptides and the prevalence of congestive heart failure in patients with pacemakers

AIM

The aim of the study was to investigate the diagnostic potential of natriuretic cardiac peptide measurement in the context of left ventricular dysfunction and comorbidities in a pacemaker population.

MATERIAL AND METHODS

Ninety-five consecutive patients with pacemakers were included in the study. All patients underwent echocardiography and were asked to complete the Minnesota Living with Heart Failure Questionnaire (MLHFQ). Brain natriuretic peptide (BNP), N-terminal proatrial natriuretic peptide (N-ANP) and atrial natriuretic peptide levels in plasma were measured.

RESULTS

Twenty-six percent of patients had reduced systolic left ventricular function; only 16 patients had a history of congestive heart failure. BNP was abnormally elevated in 64%, N-BNP in 72% and N-ANP in 96% of patients. Both BNP (r = 0.30; P < 0.01) and N-ANP (r = 0.39; P < 0.0005) correlated with MLHFQ. The strongest correlation was found between N-ANP and the ejection fraction (r = 0.6; P < 0.0001). Patients were stratified in a high-risk group and a low risk-group according to their N-ANP (N-ANP > 5000 fmol L(-1); n = 63 and N-ANP < 5000 fmol L(-1), n = 32) and BNP levels (BNP > 400 pg mL(-1); n = 17 and BNP < 400 pg mL(-1), n = 78). N-ANP was correlated with hypertension (P < 0.003) and atrial fibrillation (P < 0.03), and BNP with mitral insufficiency (P < 0.002).

CONCLUSIONS

Cardiac natriuretic peptides are markedly elevated in the majority of patients with pacemakers. The prognostic significance of BNP and N-ANP in left ventricular dysfunction warrants close follow-up schedules.

Dual chamber versus single chamber ventricular pacemakers for sick sinus syndrome and atrioventricular block

BACKGROUND

Dual chamber pacing or single chamber atrial pacing ('physiologic' pacing) is believed to have an advantage over single chamber ventricular pacing in that it resembles cardiac physiology more closely by maintaining atrioventricular (AV) synchrony and dominance of the sinus node, which in turn may reduce cardiovascular morbidity and mortality thus contributing to patient survival and quality of life. However, a significant proportion of pacemakers currently implanted are single chamber ventricular pacemakers.

OBJECTIVES

The objective of this review was to assess the short- and long-term clinical effectiveness of dual chamber pacemakers compared to single chamber ventricular pacemakers in adults with AV block, sick sinus syndrome or both. An additional objective was to assess separately any potential differences in effectiveness between dual chamber pacing and single chamber atrial pacing. The clinical effectiveness of single chamber atrial pacing versus single chamber ventricular pacing was not examined.

SEARCH STRATEGY

The Cochrane Controlled Trials Register (The Cochrane Library Issue 3, 2002), MEDLINE (1966 to 2002), EMBASE (1980 to 2002) and the Science Citation Index (1980 to 2002) were searched on 19th August 2002. Citation lists and web sites were checked and researchers in the field contacted.

SELECTION CRITERIA

Parallel group or crossover randomised controlled trials of at least 48 hours duration comparing dual chamber pacing and single chamber ventricular pacing, and investigating cardiovascular morbidity, mortality, patient related quality of life, exercise capacity and complication rates.

DATA COLLECTION AND ANALYSIS

Data was extracted onto pre-piloted data extraction forms. Quality assessment was undertaken using a checklist, with a sub-sample of quality data independently extracted by a second reviewer. Where appropriate data was available, meta-analysis was performed. Where meta-analysis was not possible, the number of studies showing a positive, neutral or negative direction of effect and statistical significance were simply counted.

MAIN RESULTS

Five parallel and 26 crossover randomised controlled trials were identified. The quality of reporting was found to be poor. Pooled data from parallel studies shows a statistically non-significant preference for physiologic pacing (primarily dual chamber pacing) for the prevention of stroke, heart failure and mortality, and a statistically significant beneficial effect regarding the prevention of atrial fibrillation (odds ratio (OR) 0.79, 95% CI 0.68 to 0.93). Both parallel and crossover studies favour dual chamber pacing with regard to pacemaker syndrome (parallel: Peto OR 0.11, 95% CI 0.08 to 0.14; crossover: standardised mean difference (SMD) -0.74, 95% CI - 0.95 to -0.52). Pooled data from crossover studies shows a statistically significant trend towards dual chamber pacing being more favourable in terms of exercise capacity (SMD -0.24, 95% CI -0.03 to -0.45). No individual studies reported a significantly more favourable outcome with single chamber ventricular pacing.

REVIEWERS' CONCLUSIONS

This review shows a trend towards greater effectiveness with dual chamber pacing compared to single chamber ventricular pacing, which supports the current British Pacing and Electrophysiology Group's Guidelines regarding atrioventricular block. Additional randomised controlled trial evidence from ongoing trials in this area will further inform the debate.

Characteristics of the acute rise of atrial natriuretic factor during ventricular pacing

BACKGROUND

Previous studies have shown that peripheral venous levels of atrial natriuretic factor (ANF) are elevated during ventricular pacing as a result of asynchrony of atrial and ventricular contraction. However, the pattern by which ANF rises following institution of ventricular pacing has not been fully established and its physiologic consequences are unclear.

METHODS

Eight ambulatory patients in stable condition with dual-chamber pacemakers were studied. The pacemaker was reprogrammed from the dual-chamber to the ventricular pacing mode for 3 h, during which serial measurements were made of BP, heart rate and rhythm, levels of ANF, and plasma renin activity (PRA).

RESULTS

ANF levels rose markedly but slowly following the onset of ventricular pacing, reaching levels as high as 694% of control. The rise occurred over the course of 120 min, at which time the average value for the group plateaued at 82.5 +/- 22.1 fmol/mL (mean +/- SEM) vs 25.3 +/- 4.5 fmol/mL at control (p < 0.01); there was, however, marked variability in individual responses. By contrast, levels of PRA remained remarkably stable. Average BP changes were small, although there was a trend in the later part of the study for systolic pressure to decrease.

CONCLUSIONS

ANF levels rise markedly but gradually after institution of ventricular pacing and, hence, acute pacing studies must account for this delay in their design. The physiologic importance of the rise in ANF should be evaluated further since the rise in peptide levels may be associated with a decrease in systolic BP.