Platelet reactivity and endothelial function in children of patients with early acute myocardial infarction

AIMS

To assess whether platelet reactivity is increased in offspring of patients with early acute myocardial infarction (AMI) and its possible relation with endothelial dysfunction.

METHODS AND RESULTS

We studied 23 healthy children (15±3 years, 13 males) of patients with early AMI (≤50 years old; Group 1) and 21 healthy children of healthy subjects without any history of cardiovascular disease (14±3 years, 10 males; Group 2). Platelet reactivity was assessed by flow cytometry as the increase in monocyte-platelet aggregates (MPA) and CD41 and PAC-1 platelet expression in response to exercise stress test (EST), adenosine diphosphate (ADP) stimulation (10(-7) M), or both. Endothelial function was assessed by measuring brachial artery dilation during post-ischaemic forearm hyperaemia [flow-mediated dilation (FMD)]. Both EST and ADP induced a higher percentage increase in platelet receptor expression in Group 1, compared with Group 2, with the most significant difference being shown for the response to the combined stimuli (e.g. MPA, 23.1±12 vs. 5.63±8%, P<0.001; platelet PAC-1, 57.7±47 vs. 13.2±7%, P<0.001). Compared with Group 2, Group 1 children showed lower FMD (10.7±3.1 vs. 8.0±2.9%, respectively; P=0.007). However, no significant association was found between FMD and platelet reactivity.

CONCLUSION

Our results show increased platelet reactivity in children of patients with early AMI; the finding was not significantly correlated with endothelial dysfunction, suggesting that other mechanisms are mainly involved in the enhanced platelet response to agonistic stimuli.

Electrical and autonomic cardiac function in patients with Dravet syndrome

Dravet syndrome (DS) is an epileptic encephalopathy related mainly to mutations in the SCN1A gene, encoding for neuronal sodium channels. Patients with DS have a high risk of sudden unexpected death in epilepsy (SUDEP). In this study we investigated whether patients with DS present abnormalities in electrical and autonomic cardiac function. To this aim we assessed ventricular repolarization and heart rate variability (HRV) on standard electrocardiography (ECG) and on 24-h ECG Holter monitoring, respectively, in 20 patients affected by DS (6.8 ± 4 years, 11 female). As age- and sex-matched control groups, we also studied 20 patients with other epileptic syndromes receiving antiepileptic drugs (ES/AED, 6.0 ± 5 years, 12 female), 20 patients with other epileptic syndromes without treatment (ES/no-AED, 6.7 ± 4 years, 10 female), and 20 healthy children (HC, 7.2 ± 5 years, 11 females). Data analysis showed that patients with DS had depressed HRV variables compared to both ES patients (ES/AED and ES/no-AED) and HC control group, whereas no significant differences in HRV variables were found between ES patients (with and without treatment) and HC. There was no significant difference between patients with DS and all the other control groups in RR intervals, QT, and QTc interval analysis. In conclusion, DS patients display an imbalance of cardiac autonomic function toward a relative predominance of adrenergic tone compared to both healthy children and patients with other forms of epilepsy, independent of antiepileptic therapy. Follow-up studies should clarify the clinical significance of this autonomic impairment and whether HRV analysis can be helpful in predicting the risk of sudden death in patients with DS.

Inflammation-related effects of adjuvant influenza A vaccination on platelet activation and cardiac autonomic function

BACKGROUND

Inflammation, platelet reactivity and cardiac autonomic dysfunction increase the risk of cardiovascular events, but the relationships between these prognostic markers are poorly defined. In this study, we investigated the effect of an inflammatory stimulus (influenza A vaccine) on platelet activation and cardiac autonomic function.

METHODS

We measured serum C-reactive protein (CRP) and interleukin-6 levels, monocyte-platelet aggregates (MPAs) and monocyte/platelet receptor expression before and after adjuvant influenza A vaccination in 28 patients with type II diabetes (mean age 62.1 ± 8 years, 18 men). Twenty-four-hour Holter electrocardiogram was recorded 24 h before and after vaccination; heart rate variability (HRV) was assessed as a measure of cardiac autonomic function.

RESULTS

Inflammatory cytokines, MPA formation and monocyte/platelet receptor expression increased after vaccination. CRP was 2.6 ± 2.8 and 7.1 ± 5.7 mg L⁻¹ 48 h before and after vaccination, respectively (P < 0.0001). HRV parameters decreased after vaccination compared to baseline, with very low-frequency amplitude showing the most significant change (34.6 ± 11.8 and 31.0 ± 10.2 ms 48 h before and after vaccination, respectively; P = 0.002). A significant correlation was found between percentage changes in CRP levels and in most HRV variables, with the most significant correlations between changes in CRP levels and changes in standard deviation of all normal RR intervals (r = 0.43; P = 0.02).

CONCLUSIONS

Together with an inflammatory reaction, influenza A vaccine induced platelet activation and sympathovagal imbalance towards adrenergic predominance. Significant correlations were found between CRP levels and HRV parameters, suggesting a pathophysiological link between inflammation and cardiac autonomic regulation. The vaccine-related platelet activation and cardiac autonomic dysfunction may transiently increase the risk of cardiovascular events.

Effect of pioglitazone on systemic inflammation is independent of metabolic control and cardiac autonomic function in patients with type 2 diabetes

The aim of this article is to investigate the relation of the anti-inflammatory effect of pioglitazone with cardiac autonomic function and metabolic control in diabetic patients. In this prospective open label trial, 36 type 2 diabetic patients (age 60 ± 10, 20 M) without overt cardiovascular disease were randomized to add pioglitazone (30 mg) to their therapy or to continue standard therapy. C-reactive protein (CRP) serum levels, metabolic parameters and cardiac autonomic function (assessed by heart rate variability [HRV] on 24-h ECG Holter monitoring) were measured at baseline and after 3 months. Clinical and laboratory variables were similar in the two groups. No significant changes were observed after 3 months for metabolic and anthropometric parameters, except for a mild increase in HDL levels in the pioglitazone group only (P = 0.04 vs. controls). CRP levels decreased significantly at follow-up in the pioglitazone group (3.2 ± 1.97 vs. 2.37 ± 1.56 mg/l) but not in the control group (3.0 ± 1.92 vs. 3.93 ± 2.14 mg/l; P = 0.003). No differences were found in basal and follow-up HRV variables between the two groups. In type 2 diabetic patients pioglitazone exerts favourable effects on inflammation even after short-term therapy. This effect precedes those on metabolic and anthropometric parameters and is not associated with changes in cardiac autonomic function.

Cardiac adrenergic nerve function in patients with cardiac syndrome X

BACKGROUND

We previously found a severe impairment of cardiac uptake of I-metaiodobenzylguanidine (MIBG), an analogue of norepinephrine, on myocardial scintigraphy in a small group of patients with cardiac syndrome X (CSX), suggesting a dysfunction of cardiac adrenergic nerve fibres. In this study, we assessed the consistency of these previous findings in a larger group of these patients.

METHODS

Planar and single-photon emission computed tomography MIBG myocardial scintigraphy was performed in 40 CSX patients (58 +/- 7 years, 17 men). Cardiac MIBG uptake was measured by the heart/mediastinum ratio and by a single-photon emission computed tomography regional cardiac MIBG uptake defect score (higher values = lower uptake). As a control group, we studied 20 healthy individuals (56 +/- 6 years, nine men). An exercise stress Tc-SestaMIBI myocardial scintigraphy was performed in 34 CSX patients (85%).

RESULTS

Cardiac MIBG defects were observed in 30 patients (75%), with nine (22.5%) showing no cardiac MIBG uptake at all. Compared with controls, CSX patients showed a significantly lower heart/mediastinum ratio (1.70 +/- 0.35 vs. 2.1 +/- 0.22, P < 0.001) and a higher cardiac MIBG defect score (27 +/- 25 vs. 4.4 +/- 2.5, P < 0.001). No differences were found in lung MIBG uptake between the two groups. Reversible perfusion defects on stress myocardial scintigraphy were found in 17 out of 34 CSX patients (50%), all of whom also had abnormal cardiac MIBG uptake; cardiac MIBG uptake abnormalities were also present in nine of 17 patients with normal perfusion scintigraphic images. Cardiac MIBG uptake findings were similar in our first 12 patients and in the 28 patients studied subsequently.

CONCLUSION

Our data show a relevant impairment of cardiac MIBG uptake in patients with CSX, suggesting that functional abnormalities in cardiac adrenergic nerve function may play a significant role in the mechanisms responsible for the syndrome.

Low glucose blood levels are associated with abnormal cardiac sympatho-vagal balance in type 2 diabetic patients with coronary artery disease

BACKGROUND AND OBJECTIVES

Glycemic control has been suggested to improve prognosis in diabetic patients, but recent trials failed to show benefits from intensive glycemic control. Hypoglycaemic episodes or large variability in glucose blood levels causing a sympatho-vagal imbalance of cardiac autonomic function (CAF) might play a role in this result. In our study we assessed whether blood glucose fluctuation may be related to variations in CAF during daily life in diabetic patients with coronary artery disease (CAD).

MATERIALS AND METHODS

Twelve patients with type 2 diabetes mellitus with CAD (65+/-4 years, 2 women) underwent simultaneous 48-hour ECG Holter monitoring and continuous interstitial glucose measurements. The highest and lowest glucose levels for each 3-hour segments of the day were identified and heart rate variability (HRV) parameters were measured on Holter recordings on 5-minute intervals centred on these times.

RESULTS

Overall, 294 glucose levels were available for analysis. In the whole population several HRV indices were significantly lower in correspondence of the lowest glucose blood levels and this difference was much more evident in patients who were not taking beta-blockers, than in patients who were taking beta-blockers. A significant, although mild, correlation was found between glucose blood levels and several time-and frequency domain HRV variables in patients not taking beta-blockers, but not in these on beta-blockers therapy.

DISCUSSION

Our data suggest that, in type 2 diabetic patients with CAD, hypoglycaemic episodes are associated with depressed HRV and that beta-blocking agents are able to contrast this relation. These interesting results merit to be investigated in a larger population of patients.

Changes in Psychological Symptoms and Heart Rate Variability During EMDR Treatment: A Case Series of Subthreshold PTSD

Elevated psychophysiological parameters and heightened physiological reactivity to trauma-related cues are acquired changes following trauma exposure. Measuring improvement in these variables is an appropriate evaluation of outcome in treatment studies. Heart Rate Variability (HRV) is a computerized measure of physiological responsivity derived from Holter ECG recording. Four female outpatients with persistent post-traumatic symptoms and personal impairment following “small t” trauma exposure underwent a course of EMDR treatment and were assessed at baseline, end of treatment, day 30 and day 90 of follow-up, using self-report symptom scales and 90-min Holter ECG recordings. Symptom scores decreased between baseline and end of treatment, with improvement maintained at follow-up. Several HRV measures changed favorably in different recording intervals. HRV is a feasible and sensitive method to measure physiological changes in the treatment of individuals distressed by “small t” trauma. Further investigation is advisable to expand these preliminary data.

Predictors of exercise-induced platelet reactivity in patients with chronic stable angina

OBJECTIVE

Previous studies have shown that exercise increases platelet reactivity in patients with coronary artery disease (CAD). However, the response of platelet reactivity to exercise is considerably variable and its predictors are poorly known.

METHODS

We studied 214 consecutive patients (age 61.9 +/- 9 years, 167 men) with stable angina and obstructive coronary artery disease. All patients underwent a symptom-limited treadmill exercise stress test. Venous blood samples were collected before and at peak exercise. Platelet reactivity was assessed by the platelet function analyzer system as the time for flowing whole blood to occlude a collagen-adenosine diphosphate ring (closure time: shorter times = higher reactivity). Both closure time at peak exercise and the exercise-induced change in closure time from rest were assessed as an expression of exercise-related platelet reactivity.

RESULTS

Closure time decreased significantly with exercise in the whole population (from 95.9 +/- 22 to 81.2 +/- 18 s, P < 0.001). The only variable significantly associated with closure time at peak exercise was hematocrit (P = 0.003). Basal systolic blood pressure (P = 0.023) and lack of nitrate use (P = 0.03), on the contrary, were the only variables significantly associated with increased exercise-induced closure time change. Peak hematocrit maintained an independent association with peak closure time in multivariable analysis, although the correlation was mild. No variable, on the contrary, was associated with exercise-induced platelet reactivity after correction for basal closure time values at multivariable analyses.

CONCLUSION

Among stable coronary artery disease patients, platelet reactivity after exercise cannot be reliably predicted by several common clinical and laboratory variables.

Combination of variant and microvascular angina

Prinzmetal's variant angina (VA) and cardiac syndrome X (CSX) are two distinct, usually easily recognizable, forms of angina syndromes, caused by epicardial spasm, usually responsible for transient transmural myocardial ischemia at rest and by coronary microvascular dysfunction (CMVD), usually responsible for effort induced subendocardial ischemia, respectively. In this article we report clinical evidence in three patients of the simultaneous occurrence of angina episodes typical of both VA and CSX, suggesting that common pathogenetic factors may be responsible for clinical manifestations both of functional macrovascular and microvascular coronary artery abnormalities in some angina patients.

Prognostic value of heart rate turbulence and its relation to inflammation in patients with unstable angina pectoris

Heart rate turbulence (HRT) provided insights into cardiac autonomic function and predicted clinical outcome in patients with myocardial infarction. A relation between cardiac autonomic function and inflammation was shown in several clinical settings. To assess the prognostic impact of HRT and its relation with inflammation in patients with unstable angina pectoris (UAP), HRT parameters (turbulence onset [TO] and turbulence slope [TS]) were measured in 331 patients with UAP (age 66.4 +/- 10 years; 231 men) with premature ventricular complexes on electrocardiographic Holter monitoring. Total and cardiac mortality were assessed at the 6-month follow-up. The 6th (-1.52%) and 4th deciles (4.90 ms/RR) were the best prognostic cut-off values for TO and TS, respectively. TS <4.9 ms/RR was associated with hazard ratio (HRs) of 7.10 (95% confidence interval [CI] 2.68 to 18.8, p = 0.0001) and 8.02 (95% CI 2.73 to 23.6, p = 0.0002) for total and cardiac mortality, respectively. The same HRs for TO >-1.52% were 2.94 (95% CI 1.11 to 7.81, p = 0.03) and 3.33 (95% CI 1.13 to 9.79, p = 0.029), respectively. Patients with TO <-1.52% and TS >4.9 ms/RR showed very low risks of total and cardiac mortality (1.8% and 0.9%, respectively). TS <4.9 ms/RR was independently associated with total (HR 3.87, 95% CI 1.21 to 12.3, p = 0.02) and cardiac (HR 3.81, 95% CI 1.01 to 14.4, p = 0.048) mortality at multivariable analyses. Both TS (r = -0.29, p <0.001) and TO (r = 0.16, p = 0.005) showed significant correlation with serum C-reactive protein. Thus, HRT can be helpful for risk stratification of patients with UAP. The association between cardiac autonomic function and inflammation can be pathogenetically relevant in this clinical setting.

CagA antigen of Helicobacter pylori and coronary instability: insight from a clinico-pathological study and a meta-analysis of 4241 cases

BACKGROUND

Cytotoxin-associated gene-A (CagA) antigen is expressed by some virulent strains of Helicobacter pylori (H. pylori). The role of CagA antigen in coronary instability is unknown. We performed a clinico-pathological study and a meta-analysis in the attempt to shed new light on this complex issue.

METHODS

In the clinico-pathological study, 38 patients with unstable angina (UA), 25 patients with stable angina (SA), 21 patients with normal coronary arteries (NCA) and 50 age and sex matched healthy volunteers were enrolled. Serology for CagA was assessed in all patients. Specimens of atherosclerotic plaques were obtained from all patients by directional coronary atherectomy, and prepared for immunohistochemistry using anti-CagA monoclonal antibodies. The meta-analysis includes 9 studies assessing the association between seropositivity to CagA strains and acute coronary events.

RESULTS

The titre of anti-CagA antibodies was significantly higher in patients with unstable angina (161+/-90 RU/ml) compared to those with stable angina (83+/-59 RU/ml p<0.02), NCA (47.3+/-29 RU/ml p<0.01) and healthy controls (73+/-69 p<0.02). Anti-CagA antibodies recognized antigens localized inside coronary atherosclerotic plaques in all specimens from both stable and unstable patients. In the meta-analysis, seropositivity to CagA was significantly associated with the occurrence of acute coronary events with an odds ratio (OR) of 1.34 (95% CI, 1.15-1.58, p=0.0003).

CONCLUSIONS

Taken together these findings suggest that in a subset of patients with unstable angina, an intense immune response against CagA-positive H. pylori strains might be critical to precipitate coronary instability mediated by antigen mimicry between CagA antigen and a protein contained in coronary atherosclerotic plaques.

[Mechanisms of myocardial cell protection from ischemia/reperfusion injury and potential clinical implications]

Myocardial cell damage caused by myocardial ischemia results from several factors that include the duration of ischemia, oxygen demand by cardiomyocytes at the time of ischemia, and the presence and entity of collateral blood flow to the ischemic area. Importantly, myocardial cell injury may derive not only from ischemia itself but also from detrimental phenomena occurring during the restoration of myocardial blood flow after the ischemic episode (reperfusion damage). In the last decades a lot of studies have demonstrated that cardiomyocytes have several mechanisms that provide them protection against the damage deriving from ischemia-reperfusion, also allowing a prolongation of survival in the most severe cases. In this article we review some of these mechanisms, also discussing their present and/or potential therapeutic applications in the clinical setting. The topics include the interventions aimed at reducing cardiac work through a reduction of oxygen demand by myocardial cells or at optimizing the utilization of energetic resources by myocardial cells in situations of ischemia, the importance of phenomena such as ischemic preconditioning (early and delayed) and postconditioning of myocardial cells, and, finally, the theoretic possibility of interventions aimed at preventing cell death consequent to apoptosis.

Association between reduced pulmonary diffusing capacity and cardiac autonomic dysfunction in Type 1 diabetes

BACKGROUND

In Type 1 diabetes mellitus (DM), it has been suggested that autonomic nervous system dysfunction (NAD) impairs lung diffusion capacity. Heart rate variability (HRV), a measure of cardiac autonomic function, is a sensitive method of detecting NAD. To our knowledge, no previous study has assessed whether cardiac sympatho-vagal balance is associated with lung diffusion capacity in diabetes.

METHODS

Twenty Type 1 DM patients without pulmonary abnormalities and systemic NAD underwent measurement of lung diffusion capacity for carbon monoxide (DLCO) by single-breath method and assessment of cardiac autonomic function by HRV analysis on 24-h electrocardiographic Holter recordings.

RESULTS

Standard respiratory function tests and peripheral autonomic tests were normal in all patients. DLCO was lower than normal reference values in six patients (30%). DLCO correlated significantly with most HRV variables, independent of the clinical and laboratory variables. The strongest correlation was found with standard deviation of all RR intervals (SDNN; r = 0.62, P = 0.003) in the time domain and low frequency (LF) power (r = 0.73, P < 0.001) in the frequency domain.

CONCLUSIONS

In Type 1 diabetes, a significant association exists between cardiac NAD and reduced DLCO in the absence of clinical respiratory and autonomic abnormalities. Thus, NAD may be involved in the early reduction of DLCO in these patients, possibly through abnormalities in the regulation of pulmonary blood flow at the microvascular level.