Efficacy of ticlopidine in the prevention of thromboembolic events in patients with VVI pacemakers

Acute and chronic phase platelet aggregability studies in Chinese patients after implantation of a permanent transvenous pacemaker

It has been suggested that the incidence of thromboembolic events always increases in patients after insertion of a transvenous pacemaker. Blood samples from twenty consecutive patients (fifteen males and five females) before and after pacemaker implantation was retained for platelet aggregability studies which were analyzed separately with ADP, collagen, epinephrine and arachidonic acid. The maximal amplitude of platelet aggregatory curve was detected by an aggregometer. The samples collected the day before pacemaker implantation (day 0) were used as self-control. Day 1 and day 3 after pacemaker implantation were defined as the acute phase, while day 30 was defined as the chronic phase. The maximal amplitude of platelet aggregatory curve was observed to be lowest on day 1 and then return to normal on day 3 and day 30. The results of platelet aggregability, however, showed no significant difference (P>0.05) between self-control and post-implantation samples. In conclusion, there was no significant change in platelet aggregability for either acute or chronic phases after pacemaker implantation. Antiplatelet medications may not be necessary for the prevention of thromboembolic events after the implantation of a pacemaker.

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.

Prethrombotic state due to hypercoagulability in patients with permanent transvenous pacemakers

Venous thrombosis is a relatively usual but serious complication of permanent transvenous pacing. However, the pathogenesis has not been defined. To clarify underlying abnormalities in the coagulation-fibrinolysis system in patients with permanent transvenous pacemakers, we measured serum levels of fibrinopeptide A (FPA), thrombin-antithrombin III complexes (TATs), plasmin-alpha 2 plasmin inhibitor complexes (PICs), D-dimer (D-D), beta-thromboglobulin (beta-TG), and platelet factor 4 (PF4) in 53 patients with permanent transvenous pacemakers and 10 control subjects. The patients were divided into two groups, as follows, according to the presence of mural thrombus documented along the pacing lead(s) by digital subtraction angiography and transesophageal echocardiography: Group Th (-), patients without venous route thrombus; and Group Th (+), patients with venous route thrombus. FPA and TAT levels increased significantly even in Group Th (-), and further increased in Group Th (+) compared with control subjects (FPA: 7.5 +/- 4.9, 15.3 +/- 8.8 vs 3.0 +/- 1.4 ng/mL, respectively, P < 0.05; TAT: 2.9 +/- 1.3, 4.8 +/- 2.3 vs 1.7 +/- 0.6 ng/mL, respectively, P < 0.05). There were no differences in levels of D-D, PIG, beta-TG, and PF4 among control subjects, Group Th (-), and Group Th (+). These findings suggest that the hypercoagulable state appears in patients with permanent transvenous pacemakers, even without apparent venous thrombosis. The patients with permanent transvenous pacemakers are thought to be in the prethrombotic state even if they have no venous route thrombosis.

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

OBJECTIVE

To investigate the platelet activation in different modes of pacing in patients implanted with dual chamber rate adaptive pacemaker (DDDR) for bradyarrhythmias, and to explore the possible underlying mechanism of the higher thromboembolic incidence in single chamber ventricular rate adaptive (VVIR) pacing.

DESIGN

Platelet activation was determined in chronically paced patients during three different pacing modes (VVIR, DDD, and DDDR) in a randomised crossover fashion.

SETTING

Pacemaker clinic at a university teaching hospital.

PATIENTS

15 patients with complete heart block, mean (SD) age 63 (10) years, and 12 patients with sick sinus syndrome, mean age 68 (9) years, implanted with DDDR pacemakers.

MAIN OUTCOME MEASURES

Platelet activation was assessed by measuring the plasma concentrations of platelet factor 4 (PF4) and beta thromboglobulin using an enzyme linked immunosorbent assay (ELISA). Mean log plasma PF4 and beta thromboglobulin values were compared in paced patients during different pacing modes and with controls.

RESULTS

Compared with controls, patients paced in DDDR, DDD, and VVIR modes had higher mean log plasma concentrations of PF4 (0.90 (0.32), 0.92 (0.29), and 1.12 (0.33) v 0.61 (0.29) log IU/ml, all p < 0.05, respectively) and beta thromboglobulin (1.55 (0.20), 1.59 (0.16), and 1.71 (0.18) v 1.40 (0.12) log IU/ml, all p < 0.05, respectively). In paced patients, VVIR pacing was associated with higher plasma concentrations of PF4 and beta thromboglobulin than either DDDR or DDD pacing (all p < 0.05). There was no significant difference in plasma PF4 and beta thromboglobulin between patients with complete heart block and sick sinus syndrome in the corresponding pacing mode. Holter monitoring showed no difference in mean pacing rate and occurrence of cardiac arrhythmias to account for the increased platelet activation during VVIR pacing. There was no relation between the percentage of ventricular pacing on Holter during DDDR, DDD, and VVIR modes and the log mean plasma concentrations of PF4 (r = 0.002, 0.001, and 0.001, respectively, all p > 0.05) and beta thromboglobulin (r = 0.007, 0.01, and 0.001, respectively, all p > 0.05).

CONCLUSIONS

Single chamber ventricular pacing was associated with enhanced spontaneous systemic platelet activation compared with physiological dual chamber pacing. This was related to the loss of atrioventricular synchrony rather than to the underlying cause of bradycardia, lack of rate response, or coexisting arrhythmia. This abnormality may be associated with increased thromboembolism and was correctible by an appropriate pacing mode prescription and possibly antiplatelet treatment.

Echographic detection of latent severe thrombotic stenosis of the superior vena cava and innominate vein in patients with a pacemaker: integrated diagnosis using sonography, pulse Doppler, and color flow

Thrombosis of the innominate vein and SVC is a serious complication in patients with pacemakers, inducing pulmonary embolism or SVC syndrome. Venography is the definitive method for its diagnosis; however, it is too invasive for related studies. The purpose of this study was to validate sonography, pulse Doppler, and color flow in detecting noninvasively innominate vein or SVC thrombosis in patients with pacemakers. In 53 patients with pacemakers, the 1 severe SVC stenosis and 18 severe innominate vein stenoses due to thrombosis were diagnosed by digital subtraction angiography. Sonography accurately showed the severe SVC stenosis due to thrombosis, but had limitations on the innominate vein thrombosis. Color flow demonstrated mosaic flow, indicating poststenotic turbulence due to stenosis of the innominate vein and SVC caused by thrombosis in 15 of 16 patients, and pulse Doppler disclosed absence of flow due to complete occlusion of the innominate vein in 2 of 2 patients. Sensitivity and specificity for detecting severe innominate vein stenosis due to thrombosis using combined color flow and pulse Doppler was 94% and 100%, respectively. In conclusion, sonography, pulse Doppler, and color flow allow accurate detection of severe innominate vein or SVC stenosis due to thrombosis, and are therefore useful for the follow-up of patients with a pacemaker.

Effect of low dose aspirin on augmented plasminogen activator inhibitor type 1 activity in patients with permanent pacemakers

To clarify the activity states of coagulation and fibrinolysis in patients with a permanent pacemaker, we studied 29 patients more than 4 months after operation. They were divided into a single pacemaker lead group (S, n = 14) and a double lead group (D, n = 15). Prothrombin time, activated partial thromboplastin time, fibrinogen, antithrombin III, tissue-type plasminogen activator (tPA) activity, plasminogen activator inhibitor type-1 (PAI-1) activity, and platelet aggregation were measured and compared to those in an age-matched control group (C, n = 7). The effects of low dose aspirin (81 mg/day) in the patients (n = 21) were also studied 2 weeks after administration. PAI-1 activity in groups S and D was significantly higher than that in the group C (53.5 +/- 36.5, 86.8 +/- 59.2 ng/mL vs 19.4 +/- 7.2 ng/mL; P < 0.01 and P < 0.005). Platelet aggregation induced by collagen was slightly higher in groups S and D than group C. Other parameters were not significantly different. In the patients, low dose aspirin significantly suppressed collagen induced platelet aggregation (71.8 +/- 20.3% vs 41.7 +/- 28.3%; P < 0.005), but not PAI-1 activity. tPA activity was increased significantly by the low dose aspirin administration (3.94 +/- 1.85 ng/mL vs 2.48 +/- 1.19 ng/mL; P < 0.005). Thus, PAI-1 activity in patients with a permanent pacemaker is elevated, and the activity is not suppressed by low dose aspirin unlike the platelet aggregation.

Mitral valve Carpentier-Edwards bioprosthetic replacement, thromboembolism, and anticoagulants

Patients undergoing mitral valve replacement (MVR) using a bioprosthesis are frequently placed on long-term anticoagulant treatment, and thereby lose the main advantage conferred by the bioprosthesis. To assess predictive factors of the need for long-term anticoagulant treatment, 100 consecutive patients surviving bioprosthetic MVR between 1977 and 1987 were followed up. The estimated thromboembolism-free survival was 88.9% +/- 3.6% after 6 years of follow-up. Preoperative risk factors for thromboembolism were supraventricular arrhythmia (p = 0.013) and a history of thromboembolism (p = 0.039). Among the preoperative and postoperative factors, only postoperative rhythm significantly influenced (p = 0.007) the thromboembolism-free survival, as determined by Cox regression analysis. Permanent anticoagulant treatment was instituted in 39 patients. Preoperative and peroperative risk factors associated with the need for long-term anticoagulant treatment, as evidenced by Fisher linear discriminant analysis, were supraventricular arrhythmia (p < 0.001), septal myotomy (p = 0.013), and predominant mitral stenosis (p = 0.013). Thus, in those patients with predominant mitral stenosis and supraventricular arrhythmia preoperatively, the subsequent need for permanent postoperative anticoagulant treatment is high, and the implantation of a mechanical valve is therefore recommended, providing there are no strict contraindications to anticoagulant treatment.

Platelet aggregability in patients with a VVI pacemaker

Several studies have suggested an increased incidence of thromboembolic events in patients with VVI pacemaker (VVI patients); furthermore, other authors have demonstrated that a treatment with anticoagulants or antiplatelet drugs may be effective in reducing thromboembolic events, thus suggesting an increased formation of platelet thrombi in these patients. In this respect, platelet aggregability was investigated in ten VVI patients and ten age- and sex-matched subjects. beta-thromboglobulin (beta-Tg) and platelet factor 4 (PF4) plasma levels were determined as well as platelet aggregation induced by ADP, collagen, epinephrine, and arachidonic acid. Plasma beta-Tg levels were increased in the patient group (86 +/- 24 vs 24 +/- 13 ng/mL; P < 0.001) in presence of normal PF4 values (14 +/- 11 vs 13 +/- 6 ng/mL; NS). Aggregation curves showed abnormal values of maximal amplitude, slope, and lag time. In particular, maximal amplitude was significantly higher in VVI patients as compared with controls (ADP P < 0.01, collagen P < 0.001, adrenaline P < 0.01, arachidonic acid P < 0.05). These findings strongly suggest an increase of platelet activity in VVI patients.