Effects of atrioventricular asynchrony on platelet activation: implication of thromboembolism in paced patients

Thromboembolic events during the perioperative period in patients undergoing permanent pacemaker implantation

BACKGROUND

Thromboembolism (TE) is one of the most serious complications after pacemaker implantation. It has been demonstrated that several patient characteristics and different pacing modes are related to an increased risk of TE events during long-term follow-up.

HYPOTHESIS

We propose that TE events occurring during the perioperative period of pacemaker implantation may be associated with certain clinical characteristics.

METHODS

The potential risk factors of TE events were analyzed in 406 consecutive patients who underwent pacemaker implantation.

RESULTS

We identified TE events in 11 patients (2.7%) within 7 days after pacemaker implantation. Four of the 11 (36.4%) patients died of complications of TE. Univariate analysis revealed that an age of >75 years (4.56 odds ratio [OR], P = 0.031), hypertension (3.59 OR, P = 0.028), diabetes (8.89 OR, P < 0.001), coronary heart disease (4.8 OR, P = 0.005), atrial fibrillation (AF) (5.68 OR, P = 0.006), persistent AF (10.36 OR, P < 0.001), and a history of stroke or transient ischemic attack (5.62 OR, P = 0.002) were associated with an increased risk of TE events. Multivariate logistic analysis showed that persistent AF (9.8 OR, P < 0.001) was independently associated with TE. The incidence of perioperative TE was not significantly different between patients with single- and dual-chamber pacemakers.

CONCLUSIONS

We found TE events during the perioperative period in patients undergoing pacemaker implantation were not uncommon. Because persistent AF during the perioperative period was the only independent risk factor for perioperative TE, appropriate anticoagulation therapy may be necessary in those patients. © 2012 Wiley Periodicals, Inc. J. Liu, MD, is co-first author. The authors have no funding, financial relationships, or conflicts of interest to disclose.

Subtraction method for determination of N-terminal connective tissue growth factor

Background

Connective tissue growth factor (CTGF) may be a potential marker of fibrosis. However, platelet-derived CTGF may be released into the plasma by platelet activation during or after blood collection, thereby interfering with accurate determination of the true plasma CTGF level. Plasma CTGF exists as the N-terminal CTGF fragment (N-fragment), composed of modules 1 and 2, whereas platelet CTGF exists as full-length CTGF (full-length), composed of modules 1–4. We perceived the need to develop a method for distinguishing between the N-fragment and full-length CTGF levels, so that the true plasma and serum CTGF (N-fragment) levels could be accurately determined.

Methods

Full-length levels were determined by a sandwich enzyme-linked immunosorbent assay (ELISA) using two monoclonal antibodies recognizing modules 1 and 4, respectively (M1/4 ELISA). Total CTGF (full-length CTGF plus N-terminal CTGF) levels were determined by a sandwich ELISA using two monoclonal antibodies recognizing modules 1 and 2, respectively (M1/2 ELISA). N-terminal CTGF levels were determined by subtracting the full-length levels from the total CTGF levels.

Results

Both the M1/2 and M1/4 ELISAs showed good analytical performance. When the CTGF levels of plasma and serum collected simultaneously from the same subject were compared, the N-fragment levels determined by the subtraction method were the same, in spite of the fact that full-length CTGF was present in the sample.

Conclusion

N-fragment levels in plasma and serum can be accurately determined by this subtraction method, even if full-length CTGF in platelets is released during or after blood collection.

Transvenous Cryoablation Reduces Platelet Activation During Pulmonary Vein Ablation Compared with Radiofrequency Energy in Patients with Atrial Fibrillation

BACKGROUND

Radiofrequency (RF) ablation procedures for atrial fibrillation (AF) are associated with potential risks of thromboembolism, which may be minimized by the use of cryoablation that preserves the integrity of endocardium. The objective of this study was to compare the thrombogenic potential of transvenous cryoablation versus RF ablation during pulmonary vein (PV) isolation.

METHODS AND RESULTS

Thirty consecutive patients with paroxysmal AF were randomized to undergo segmental PV isolation procedure using 4-mm tip RF ablation (n = 15) or cryoablation (CryoCor, San Diego, CA, USA) (n = 15). Blood samples were drawn after sheath insertion (baseline), after transseptal puncture, before ablation (after heparin administration), and after isolation of a superior PV. Activation of coagulation was measured with plasma levels of prothrombin fragment 1 + 2 (F1 + 2) and thrombin-antithrombin III complex (TAT), and platelets by plasma level of beta-thromboglobulin (beta-TG) and flow cytometric enumerating of P-selectin (CD62)-positive platelets. In both groups, the plasma level of beta-TG, F1 + 2, and TAT were elevated after sheath insertion. The percentage changes in plasma level of beta-TG, F1 + 2, and TAT and CD41/62-positive platelets from baseline after transseptal puncture and before ablation were similar (P > 0.05). However, the percentage changes in CD62-positive platelets from baseline were significantly higher in patients treated with RF ablation (82 +/- 20%) than with cryoablation (22 +/- 14%, P = 0.02), although their plasma levels of beta-TG, F1 + 2, and TAT were not different (P > 0.05).

CONCLUSIONS

Significant platelet and coagulation activations were observed during PV ablation procedures, and heparin administration only prevented activation of coagulation but not platelets. Persistent platelets activation was observed during RF energy application, but not during cryoablation.

Comparison of hemostatic activation created by right- and left-heart radiofrequency catheter ablation

BACKGROUND

Thromboembolic complications commonly occur in radiofrequency (RF) ablation procedures (0.6-1.3% of cases). Comparison of hemostatic activation between left and right RF ablation is limited.

HYPOTHESIS

The purpose of this study was to evaluate platelet and hemostatic activation before, immediately after, and 48 h following left and right myocardial RF ablation procedures.

METHODS

The subjects were two groups of patients who underwent right-heart (24 patients) and left-heart (20 patients) RF ablation. Blood samples taken before, immediately after, and 48 h after the procedure were tested for changes in platelet and hemostatic activation.

RESULTS

No indication of clinically symptomatic thromboembolism and no major differences in baseline characteristics and procedure were apparent in either group, except for a higher temperature mode setting (p < 0.001) in the left-heart group. The hemostatic evaluation levels increased significantly by the end of the procedure in both groups and the platelet activation level remained elevated for 48 h after the procedure. The platelet activation level increased insignificantly at the end and 48 h after the procedure. Of the other changes in levels of platelet and hemostatic activation, only an increase in one of the hemostatic levels in the right-heart group at 48 h after procedure was significant (p = 0.01).

CONCLUSIONS

Our findings suggest that similar hemostatic activation occurred during and immediately after RF ablation in both groups. Sustained elevation of the hemostatic marker after the ablation procedure in the right-heart group was observed as of significant therapeutic and prognostic implications.

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.

[Prospective and comparative study of pacemaker implants carried out at the electrophysiology laboratory and the operating room]

INTRODUCTION AND OBJECTIVES

Permanent pacemaker implantation is done by different physicians with either a surgical or clinical training. Our objective was to evaluate if there were significant differences in the implantation parameters and in the complication rate among implantations performed by cardiologists in the electrophysiologic laboratory and cardiological surgeons in the operating room.

MATERIAL AND METHODS

We prospectively collected those patients' data who received a first pacemaker implantation by cardiovascular surgeons and electrophysiologists during the year 1998. Data collected included demographic information, indication for pacing, surgical time, complications during procedure, stimulation and sensing thresholds as well as type of pacing.

RESULTS

We first-implanted 216 pacemakers in a one year period, 101 by cardiovascular surgeons and 115 by electrophysiologists. 56% were male patients. Average age in the surgery group was 74.2 +/- 9 years and 72.09 +/- 12 in the electrophysiology group (p = NS). Main diagnoses were as follows: complete heart block in 32.9% patients, complete heart block 2. degrees 16.4%, sinus node dysfunction 12.2%, AV node ablation 12.2% and others. The complications rate for surgery group was 4% and 1.7% for electrophysiologists (p = NS). Electrophysiologists placed more bicameral devices. No clinically significant differences were found among other implant parameters.

CONCLUSIONS

Pacemaker implant by cardiologists in an electrophysiologists laboratory is a safe procedure that does not have more complications when compared to the same procedure done in the operating room by surgeons. This allows hospital resource optimization and reduction of hospital stay length.

Arterial thromboembolism in patients with sick sinus syndrome: prediction from pacing mode, atrial fibrillation, and echocardiographic findings

OBJECTIVE

To evaluate whether thromboembolism in sick sinus syndrome can be predicted by pacing mode, atrial fibrillation, or echocardiographic findings.

METHODS

Patients were randomised to single chamber atrial (n = 110) or ventricular (n = 115) pacing. They were divided into subgroups with and without brady-tachy syndrome at time of randomisation. The occurrence of atrial fibrillation and thromboembolism during follow up were investigated and compared with echocardiographic findings.

RESULTS

The annual risk of thromboembolism was 5.8% in patients with brady-tachy syndrome randomised to ventricular pacing, 3.2% in patients without brady-tachy syndrome randomised to ventricular pacing, 3% in patients with brady-tachy syndrome randomised to atrial pacing, and 1.5% in patients without brady-tachy syndrome randomised to atrial pacing. In atrial paced patients without brady-tachy syndrome at randomisation and without atrial fibrillation during follow up, the annual risk of thromboembolism was 1.4%. Left atrial size measured by M mode echocardiography was of no value in predicting thromboembolism.

CONCLUSIONS

Arterial thromboembolism in patients with sick sinus syndrome is very common and is associated primarily with brady-tachy syndrome at randomisation and with ventricular pacing. The risk of thromboembolism is small in atrial paced patients in whom atrial fibrillation has never been documented.