Platelet activation and mitral valve prolapse

Platelet proteome changes in dogs with congestive heart failure

BACKGROUND

Platelets play a central role in the development of cardiovascular diseases and changes in their proteins are involved in the pathophysiology of heart diseases in humans. There is lack of knowledge about the possible role of platelets in congestive heart failure (CHF) in dogs. Thus, this study aimed to investigate the changes in global platelet proteomes in dogs with CHF, to clarify the possible role of platelets in the physiopathology of this disease. Healthy-dogs (n = 10) and dogs with acute CHF due to myxomatous mitral valve disease (MMVD, n = 10) were used. Acute CHF was defined based on the clinical (increased respiratory rate or difficulty breathing) and radiographic findings of pulmonary edema. Dogs Blood samples were collected into tubes with acid-citrate-dextrose, and platelet-pellets were obtained by centrifuge and washing steps. Platelet-proteomes were identified using LC-MS based label-free differential proteome expression analysis method and matched according to protein database for Canis lupus familiaris.

RESULTS

Totally 104 different proteins were identified in the platelets of the dogs being 4 out of them were significantly up-regulated and 6 down-regulated in acute CHF dogs. Guanine-nucleotide-binding protein, apolipoproteins (A-II and C-III) and clusterin levels increased, but CXC-motif-chemokine-10, cytochrome-C-oxidase-subunit-2, cathepsin-D, serine/threonine-protein-phosphatase-PP1-gamma-catalytic-subunit, creatine-kinase-B-type and myotrophin levels decreased in acute CHF dogs. These proteins are associated with several molecular functions, biological processes, signaling systems and immune-inflammatory responses.

CONCLUSION

This study describes by first time the changes in the protein composition in platelets of dogs with acute CHF due to MMVD. Our findings provide a resource for increase the knowledge about the proteome of canine platelets and their roles in CHF caused by MMVD and could be a tool for further investigations about the prevention and treatment of this disease.

Hemostatic function in Cavalier King Charles Spaniels assessed using thromboelastography

BACKGROUND

Macrothrombocytopenia is a well-known anomaly in Cavalier King Charles Spaniels (CKCSs), a breed also highly predisposed to develop myxomatous mitral valve disease (MMVD). Thromboelastography (TEG) has been shown to be a valuable instrument for whole blood hemostatic evaluation in dogs and correlates well with different physiologic and pathologic situations.

OBJECTIVES

We aimed to assess the influence of macrothrombocytopenia and the severity of MMVD on hemostatic function as measured by TEG.

METHODS

Associations between TEG variables (R, K, α, MA, and G) and dog characteristics, heart rates, systolic blood pressures, MMVD severities (healthy, mild or moderate, and severe), echocardiographic variables, platelet variables (platelet count, mean platelet volume [MPV], and plateletcrit), and hematocrits were evaluated in 47 prospectively recruited privately owned CKCSs. Blood samples were analyzed using a computerized thromboelastograph and an Advia 2120 hematology analyzer.

RESULTS

Univariable and multiple regression analyses showed an effect of left ventricular (LV) fractional shortening (FS%) on all TEG variables, an effect of LV FS% and age on TEG α, and an effect of LV FS% and MPV on TEG MA and TEG G. TEG MA and G increased with increasing MPV, but the associations were generally weak. No significant differences were detected in the TEG variables between the MMVD severity groups.

CONCLUSION

Macrothrombocytopenia and increased LV FS%, of which the latter commonly increases in various positive inotropic states, were both associated with a more hypercoagulable hemostatic system, according to the TEG results, in the present study.

Plasma and platelet serotonin concentrations in healthy dogs and dogs with myxomatous mitral valve disease

OBJECTIVES

Serotonin has been implicated in canine myxomatous mitral valve disease (MMVD); however, the sources of serotonin have not been fully elucidated. This study compared the concentration of serotonin in plasma and platelets of normal healthy small breed dogs with predisposition to MMVD and dogs with naturally occurring MMVD.

ANIMALS

43 small-breed client-owned dogs with an approximate weight of <10 kg and age of 6 years or above were divided into 2 groups: a healthy control group (n = 20) and a group with echocardiographic evidence of MMVD (n = 23).

METHODS

5 ml samples of blood were collected. Plasma and platelets were separated by centrifugation and assayed for serotonin measured by enzyme linked immunosorbent assay (ELISA).

RESULTS

Median plasma serotonin concentration was not significantly different (p = 0.3630) between normal healthy dogs (3.7 ng/ml) and dogs with MMVD (4.3 ng/ml). Males had higher plasma serotonin concentration than females (4.7 and 2.9 ng/ml respectively, p = 0.0043). Platelet serotonin concentration was not different between healthy dogs and dogs with MMVD (128.6 ng/10⁹ platelets and 176.6 ng/10⁹ platelets respectively, p = 0.4575). Age, echocardiographic indices and platelet count showed no correlation with plasma or platelet serotonin concentration.

CONCLUSIONS

Circulating plasma serotonin is unlikely a major source of serotonin signaling in canine MMVD. Platelets could be a source of serotonin in canine MMVD through platelet adhesion to the mitral valve; however, the amount of serotonin stored in platelets of healthy dogs and dogs with MMVD is not different.

Mean platelet volume may be elevated in mitral valve prolapse and associated with the severity of prolapse

Thromboembolic events can be seen in patients with mitral valve prolapse (MVP). It is unclear whether platelet activation may contribute to these events in patients with MVP. Thus, we aimed to evaluate mean platelet volume (MPV) in patients with MVP and its association with the severity of MVP. This study included 312 patients with MVP and 240 control participants. Mean platelet volume was significantly higher in patients with MVP than in controls (8.9 ± 0.7 vs 7.9 ± 0.6 fL, P = .001). In linear regression analysis, MPV was independently associated with the degree of mitral regurgitation (β = .23, 95% confidence interval (CI): 0.14-0.32, P = .001), maximal leaflet displacement (β = .24, 95%CI: 0.17-0.31, P = .001), and mean thickness of the anterior (β = .47, 95%CI: 0.27-0.61, P = .001) and posterior leaflets (β = .22, 95%CI: 0.03-0.41, P = .02). Our findings show that MPV can be elevated in patients with MVP and may be independently associated with severity of mitral regurgitation, leaflet displacement, and thickness of the leaflets.

Right pulmonary agenesis in an elderly woman complicated by transient ischemic attack

There are few case reports regarding patients with right lung agenesis living to old age because of both severe mediastinal and cardiac displacements. We report a 61-year-old woman with right pulmonary agenesis complicated by a transient ischemic attack that was evaluated by a three-dimensional reconstruction of helical computed tomography and an echocardiography. This patient was able to survive until old age because she had no critical anomalies in other organs including the heart. A mitral valve prolapse was detected by a two-dimensional echocardiography and we treated her with anti-platelet aggregation therapy for the prevention of recurrent stroke.

Mitral valve prolapse

Mitral valve prolapse is a common valvular abnormality that is the most common cause of severe non-ischaemic mitral regurgitation in the USA. The overall prognosis of patients with mitral valve prolapse is excellent, but a small subset will develop serious complications, including infective endocarditis, sudden cardiac death, and severe mitral regurgitation. We present a comprehensive review of mitral valve prolapse, examining normal mitral anatomy, the clinical and echocardiographic features of mitral valve prolapse, and the pathophysiology and genetics of the disorder. We discuss the contemporary management of both asymptomatic and symptomatic prolapse, with particular attention to the timing and technique of surgical repair. We conclude that echocardiography is the method of choice for diagnosing mitral valve prolapse, that clinical and echocardiographic features can predict which patients with prolapse are at highest risk for complications, and that mitral valve repair is the treatment of choice for symptomatic prolapse.

Decreased Platelet Function in Cavalier King Charles Spaniels with Mitral Valve Regurgitation

With aggregometry, increased platelet activity has been reported in Cavalier King Charles Spaniels (CKCS) without mitral regurgitation (MR). In contrast, dogs with MR have been found to have decreased platelet activity. The purpose of this study was to test an easy bedside test of platelet function (the Platelet Function Analyzer [PFA-100]) to see if it could detect an increase in platelet activity in CKCS without MR and a decrease in platelet activity in CKCS with MR. This study included 101 clinically healthy dogs > 1 year of age: 15 control dogs of different breeds and 86 CKCS. None of the dogs received medication or had a history of bleeding. The PFA-100 evaluates platelet function in anticoagulated whole blood under high shear stress. Results are given as closure times (CT): the time it takes before a platelet plug occludes a hole in a membrane coated by agonists. The CT with collagen and adenosine-diphosphate as agonists was similar in control dogs (median 62 seconds; interquartile interval 55-66 seconds) and CKCS with no or minimal MR (55; 52-64 seconds). The CT was higher in CKCS with mild MR (regurgitant jet occupying 15-50% of the left atrial area) (75; 60-84 seconds; P = .0007) and in CKCS with moderate to severe MR (jet > 50%) (87: 66-102 seconds; P < .0001). CKCS with mild, moderate, and severe, clinically inapparent MR have decreased platelet function. The previous finding of increased platelet reactivity in nonthrombocytopenic CKCS without MR could not be reproduced with the PFA-100 device.

Diminished global fibrinolytic capacity in patients with mitral valve prolapse is associated with transient ischemic attacks

Although mitral valve prolapse (MVP) has shown to be associated with thromboembolic complications, the cause of thromboembolic events in those patients is still unknown. The purpose of this study was to evaluate the fibrinolytic activity in MVP patients. The study included 35 consecutive patients (25 women, mean age 25+/-11 years) with echocardiographically documented MVP and 25 age- and sex-matched subjects as a control group. Four of MVP patients have a history of transient ischemic attack (TIA). Global fibrinolytic capacity (GFC), a new technique that examines the effectiveness of the entire fibrinolytic system, was measured. Global fibrinolytic capacity was found to be nonsignificantly increased in MVP patients (3.14+/-1.42 microg/mL) compared to those in control subjects (2.36+/-1.33 microg/mL) (p>0.05). However, in four of these MVP patients who had a history of transient ischemic attack, the GFC level was significantly lower than in patients who have no history of transient ischemic attack (1.67+/-0.6 microg/mL vs 3.27+/-1.46 (microg/mL, p=0.003). Furthermore, the GFC levels of these four patients were less than those of controls (p=0.04). These results showed that global fibrinolytic activity was similar in MVP patients without a history of TIA and control subjects. However, MVP patients with a history of TIA had significantly decreased global fibrinolytic activity compared to controls and as well as MVP patients without a history of TIA.

Relation between mitral regurgitation and platelet activation

OBJECTIVES

This study sought to examine the effect of mitral regurgitation (MR) on platelet activation in patients with mitral valve prolapse (MVP) or rheumatic MR.

BACKGROUND

MVP and rheumatic MR are associated with an increased incidence of thromboembolic events. Although the underlying causes are not clear, increased platelet activation has been suggested as one of the pathogenic mechanisms. Results of previous studies that have investigated the relation between MVP and platelet activation are controversial. Whether the presence of MR in patients with mitral valve disease is associated with platelet activation remains unclear.

METHODS

We studied platelet activation by measuring the plasma level of platelet factor 4 (PF4) and beta-thromboglobulin (BTG) in 16 patients with MVP, 12 patients with rheumatic MR and 25 control subjects. A detailed echocardiographic examination, including M-mode measurement and color Doppler flow mapping to detect the presence and severity of MR was performed.

RESULTS

Patients and control subjects were matched for gender, age and left ventricular ejection fraction. Eight (50%) of 16 patients with MVP had MR. Patients with MVP and MR and patients with rheumatic MR had a significantly larger left atrial diameter. Mean log plasma levels of PF4 and BTG were significantly higher in patients with MVP and MR and patients with rheumatic MR than in control subjects (1.17 +/- 0.22 and 0.93 +/- 0.23 IU/ml vs. 0.52 +/- 0.34 IU/ml, p < 0.01; 1.70 +/- 0.21 and 1.53 +/- 0.15 IU/ml vs. 1.37 +/- 0.15 IU/ml, p < 0.05, respectively) but were comparable in patients with MVP and no MR and control subjects. Plasma levels of PF4 and BTG were positively correlated with the severity of MR, as assessed by a semiquantitative method (r = 0.59, p = 0.0001; r = 0.60, p = 0.0001, respectively). Increasing age and left atrial enlargement were not related to platelet activation.

CONCLUSIONS

MR in mitral valve disease was associated with systemic platelet activation. MVP itself was not associated with increased platelet activation. The degree of platelet activation was positively correlated with the severity of MR and was independent of the underlying etiology of mitral valve disease, age and left atrial size. The possibility of a higher incidence of thromboembolism and the role of antiplatelet agents in such patients will require further studies to determine.

Platelet aggregation in transient global amnesia

We found a correlation between increased platelet aggregation parameters and transient global amnesia and no differences between patients with transient global amnesia and transient ischemic attacks. Our findings support the theory of a vascular mechanism for transient global amnesia.

Mitral valve prolapse and platelet aggregation in patients with hemiplegic and non-hemiplegic migraine

Migraine and mitral valve prolapse (MVP) share a number of features. Both migraine and MVP show platelet dysfunctions and an increased risk of transient ischemic attacks (TIA) and stroke. There is a strikingly high incidence of migraine among MVP patients. The focal neurological deficits associated with hemiplegic migraine resemble TIA symptoms which may occur in MVP patients. Furthermore, the risk of cerebral infarction in migraineurs is reported to be higher than in the general population. The results of our study with 43 patients suffering from non-hemiplegic migraine (common and classical migraine) and 19 migraineurs with a hemiplegic migraine indicate that hemiplegic migraine is not associated with MVP and increased platelet aggregation more frequently than other migraine forms. Independent of migraine type, there is no difference between patients with and without mitral valve prolapse with respect to platelet dysfunction.

Activation of platelet function in Fabry's disease

Increased platelet aggregation and high plasma concentration of beta-thromboglobulin were observed in hemizygotes and heterozygotes of Fabry's disease. Carbamazepine and phenytoin administered for the treatment of pains in these patients showed no significant effect on platelet aggregation. No activation of platelets was observed after the addition of ceramide trihexoside, the storage lipid of this disease. Mitral valve prolapse was found in eight of 12 patients. Although the pathogenesis of platelet activation and mitral valve prolapse are not known, the platelet activation could be an early indicator and an accelerating factor of thromboembolic vascular change in this disease.

Neurologic disorders associated with mitral valve prolapse

Mitral valve prolapse has been reported to be associated with a variety of neurologic disorders, including cerebral ischemia, transient global amnesia, migraine, autonomic dysfunction, and psychiatric disease. The evidence supporting these associations and possible pathogenetic mechanisms are discussed. Some neurologic disorders may be direct complications of mitral valve prolapse, while others may occur as part of an underlying genetic defect or common link.

Branch artery occlusion in a young woman

A 31-year-old woman presented with signs and symptoms of anterior and posterior cerebral circulatory insufficiency. The differential diagnosis and therapeutic options are discussed. The most likely cause is a cardiogenic source of emboli.

Platelet activity in mitral valve prolapse: a study of platelet aggregation, malondialdehyde production, and plasma beta-thromboglobulin

Platelet aggregation, malondialdehyde (MDA) production, and recovery after aspirin (ASA) administration and plasma levels of beta-thromboglobulin (BTG) were determined in 40 asymptomatic patients with mitral valve prolapse (MVP) and 17 normal subjects. Platelet aggregation was similar in patients and controls, although two patients presented spontaneous aggregation. Production of MDA and plasma levels of BTG were higher in MVP than in controls; however, recovery after ASA was similar in both groups. The results further indicate that platelet hyperactivity is present in a significant number of asymptomatic patients with MVP.