Past use of erythromycin, tetracycline, or doxycycline is not associated with risk of first myocardial infarction

Clinical study of chlamydia pneumoniae infection in patients with coronary heart disease

Background

This study aims to investigate the chlamydia pneumoniae infection (PC) in patients with coronary heart disease.

Methods

A total of 92 patients with coronary heart disease, who were treated with percutaneous coronary intervention (PCI), were selected as the case group. In addition, 50 healthy people were enrolled as the control group. The incidences of CP infection and serum Chlamydia pneumoniae IgA antibody (CP-IgA), high sensitive C-reactive protein (hs-CRP), and interleukin-6 (IL-6) were compared in these two groups. The classification of coronary artery lesion, the incidence of perioperative cardiovascular events, and adverse prognosis events within six months after procedure were compared.

Results

The incidence of CP infection in the case group was higher (42.4% vs. 0%, P < 0.05). Furthermore, 17 patients were at grade I, 39 patients were at grade II, and 36 patients were at grade III. The incidences for these three kinds of patients were 17.6, 30.8, and 66.7%. The incidence of CP infection at grade III was higher than that of grade I or II (P < 0.05). Serum CP-IgA, hs-CRP and IL-6 levels increased with the severity of the coronary artery disease (P < 0.05), and the serum hs-CRP and IL-6 levels of patients with perioperative cardiovascular events were higher (P < 0.05). Moreover, the serum CP-IgA levels of the patients with adverse prognosis events were also higher (P < 0.05).

Conclusions

Patients with coronary heart disease have a high CP infection rate. The degree of infection is relevant to the severity of the coronary artery lesions and postoperative prognosis of patients, suggesting that CP infection may be an important factor affecting the incidence and prognosis of coronary heart disease.

Potential implications of matrix metalloproteinase-9 in assessment and treatment of coronary artery disease

BACKGROUND

Matrix metalloproteinase (MMP)-9, a member of the MMP superfamily is consistently implicated in the pathophysiology of atherosclerosis and plaque rupture, the most common mechanism responsible for acute coronary syndrome (ACS).

AIM

To summarize the role of MMP-9 in atherosclerosis and its potential implications in assessment and treatment of coronary artery disease (CAD).

METHODS

We reviewed the PubMed database for relevant data regarding the role of MMP-9 in the pathophysiology of atherosclerosis. In the light of these data, we postulate potential implications of MMP-9 in the management and treatment of CAD.

RESULTS AND CONCLUSIONS

Existing data strongly support the role of MMP-9 in plaque destabilization and rupture. Based on the current knowledge, MMP-9 can potentially serve as a diagnostic biomarker in ACS and a prognostic biomarker in ACS and chronic CAD patients. MMP-9 is reduced by therapies that are associated with favourable outcome in atherosclerosis and thus may serve as a surrogate biomarker of treatment efficacy. However, large morbidity and mortality trials are still required to confirm that MMP-9 reduction is associated with improved outcome independent of the traditional risk factors (i.e. low-density lipoprotein cholesterol). Given its role in plaque rupture, inhibition of MMP-9 may promote plaque stabilization and consequently reduce cardiovascular events. Yet, the efficacy and safety of MMPs inhibitors should be first studied in preclinical models of atherosclerosis.

Antibiotics active against Chlamydia do not reduce the risk of myocardial infarction

OBJECTIVE

There is evidence that Chlamydia pneumoniae (CP) is involved in the aetiology of myocardial infarction (MI). Randomised trials do not support a beneficial effect of antibiotics in secondary prevention of MI, but the evidence for an effect on primary prevention is conflicting. We investigated if past use of antibiotics active against CP is associated with a decreased risk of developing MI.

METHODS

We conducted a population-based case-control study of 4166 patients hospitalised due to MI from 1 January 1994 to 1 September 1999 in the County of Funen, Denmark. Controls (n=16,664) were a random sample of inhabitants, matched for age and sex. Confounders controlled for in the analysis were gender, age, obstructive pulmonary disease, diabetes, previous MI and known atherosclerotic antecedents. Previous use of antibiotics active against CP (macrolides, tetracyclines and quinolones) and of antibiotics not active against CP (penicillins) was analysed among the cases and controls.

RESULTS

The risk of MI was not associated with previous exposure to macrolides (OR: 1.0; CI: 0.9-1.1), tetracyclines (OR: 1.0; CI: 0.9-1.2) or quinolones (OR: 1.0; CI: 0.9-1.2) or combinations of the three drugs (OR: 1.0; CI: 0.9-1.1). There was no sign of a protective effect in subgroups defined by high cumulative doses of antibiotics, various time-windows of exposure, risk factors of MI or other co-morbidity. OR was 1.1 (0.9-1.3) in persons with no atherosclerotic antecedents.

CONCLUSION

The study does not support the hypothesis of a decreased risk of MI in patients exposed to antibiotics active against CP.

Update of antibiotic trials for secondary prevention of coronary heart disease

The possibility that infection is a stimulus for the vascular inflammation that promotes atherogenesis has spawned clinical trials of antibiotics. These have focused primarily on Chlamydia pneumoniae as a potential atherogenic agent. In contrast to pilot studies, recent large trials, capped by the Azithromycin and Coronary Events Study and PRavastatin Or AtorVastatin Evaluation and Infection Therapy mega trials, indicate that standard antibiotics (e.g., azithromycin and gatifloxacin) are ineffective for secondary cardiovascular prevention. Despite this, observations continue to mount that infection can be a stimulus for atherothrombosis. Thus, one should rethink, revise and reformulate hypotheses, and research strategies, including novel antibiotics and treatment at earlier stages of disease, rather than discard infection prematurely as a potential etiologic factor.

TLR signaling: an emerging bridge from innate immunity to atherogenesis

Chronic inflammation and disordered lipid metabolism represent hallmarks of atherosclerosis. Considerable evidence suggests that innate immune defense mechanisms might interact with proinflammatory pathways and contribute to development of arterial plaques. The preponderance of such evidence has been indirect clinical and epidemiologic studies, with some support from experimental animal models of atherosclerosis. However, recent data now directly implicate signaling by TLR4 in the pathogenesis of atherosclerosis, establishing a key link between atherosclerosis and defense against both foreign pathogens and endogenously generated inflammatory ligands. In this study, we briefly review these and closely related studies, highlighting areas that should provide fertile ground for future studies aimed at a more comprehensive understanding of the interplay between innate immune defense mechanisms, atherosclerosis, and related vascular disorders.

Antibiotics in primary prevention of stroke in the elderly

BACKGROUND AND PURPOSE

An increasing number of reports have linked infections to atherosclerosis and thrombosis. Thus, use of antibiotics may lower the risk of developing cerebrovascular disease. We investigated whether antibiotic use is associated with the risk of stroke in elderly individuals treated for hypertension.

METHODS

A cohort of 29 937 elderly subjects initiating antihypertensive therapy between 1982 and 1995 was formed from the Quebec healthcare insurance database. A nested case-control design was used in which each subject hospitalized with a primary discharge diagnosis of stroke between 1987 and 1995 was matched on calendar time to 5 randomly selected controls from the cohort. Conditional logistic regression was used to estimate odds ratios of stroke after adjustment for predisposing factors.

RESULTS

We identified 1888 cases and 9440 controls. The overall adjusted odds ratio for current antibiotic use was 0.80 (95% confidence interval, 0.63 to 1.01), and that for recent use was 0.81 (95% confidence interval, 0.70 to 0.94). Penicillin was the only individual antibiotic class that showed a protective association across different time windows. No significant association was found between stroke risk and the use of fluoroquinolones, macrolides, tetracyclines, or cephalosporins.

CONCLUSIONS

Although no clear, consistent associations between overall antibiotic use and cerebrovascular disease could be found, an intriguing association between penicillin use and stroke should be explored further.

Use of antibiotics is not associated with decreased risk of myocardial infarction among patients with diabetes

OBJECTIVE

To study the relationship between exposure to antibiotic treatment and risk of subsequent myocardial infarction (MI) in patients with diabetes.

RESEARCH DESIGN AND METHODS

A case-control design was used to assess the effect of previous antibiotic exposure in diabetes patients with acute, nonfatal or fatal MI (case subjects) and individually matched control subjects (four control subjects to one case subject, matched on sex, age, and index date). Subjects were sampled from the Northern California Kaiser Permanente Diabetes Registry, a well-characterized, ethnically diverse diabetic population from Kaiser Permanente Medical Care Program, Northern California Region. MI events were ascertained during a 2-year observation period (1998-1999). Separate conditional logistic regression models were specified to assess antibiotic exposure history (cephalosporins only, penicillins only, macrolides only, quinolones only, sulfonamides only, tetracyclines only, as well as more than one, any, or no antibiotic) for three nested windows before the index date (0-6 months, 0-12 months, 0-24 months), facilitating assessment of whether the potential effect was dependent on the timing of the exposure.

RESULTS

A total of 1,401 MI case subjects were observed. Odds ratios were calculated in models adjusted for age, sex, race, education attainment, time since diabetes diagnosis, diabetes type and treatment, use of diet and exercise, total cholesterol, HDL cholesterol, triglyceride levels, hypertension, elevated urinary albumin excretion, serum creatinine, BMI, and smoking. We found no evidence of a protective effect of any of these therapeutic classes of antibiotics during any of the three time frames.

CONCLUSIONS

Our study does not support the hypothesis that use of antibiotics has a protective effect for prevention of coronary heart disease in diabetic patients.

Antibiotics in primary prevention of myocardial infarction among elderly patients with hypertension

BACKGROUND

Given the premise that certain bacteria (such as Chlamydia pneumoniae) may play a role in the etiology of atherosclerosis, subjects treated with antibiotics that have antibacterial activity against C pneumoniae may be at lower risk for the development of an acute myocardial infarction (MI) than untreated subjects.

METHODS

A case-control design, nested within a cohort of 29,937 elderly subjects in whom antihypertensive therapy was initiated (1982-1995) was used, in which each subject who was hospitalized with a primary discharge diagnosis of MI between 1987 and 1995 (n = 1047) was matched on calendar time to 5 randomly selected control subjects for exposure contrasts. Conditional logistic regression analyses were conducted to adjust for predisposing factors for MI.

RESULTS

Although no clear consistent effect of antibiotics use was found in relation to MI, a trend was observed for a decreased risk of acute MI in patients receiving a prescription for antichlamydial antibiotics in the preceding 3 months (odds ratio 0.68, 95% CI 0.46-1.00). Antibiotics without antichlamydial activity showed no benefit in MI risk.

CONCLUSION

The beneficial effect of certain antichlamydial antibiotics in reducing the risk of MI cannot be excluded on the basis of this representative cohort of elderly patients in a routine clinical care setting. Larger prospective studies are required to confirm the usefulness of antibiotics in the primary prevention of MI.

Role of antibiotics for the prevention of cardiovascular disease

OBJECTIVE

To evaluate the data regarding the use of antibiotic therapy for the prevention of cardiovascular events.

DATA SOURCES

Pertinent literature was identified through a MEDLINE search (1966-September 2001) and through other secondary literature databases and/or bibliographies of pertinent articles.

DATA SYNTHESIS

Cardiovascular disease is a common cause of morbidity and mortality among the general population, with well-defined risk factors (e.g., diabetes, hypertension, hyperlipidemia, cigarette smoking, genetic predisposition). Clinical data evaluating the association between the aforementioned risk factors and the development of atherosclerosis and subsequent cardiovascular disease are substantial; however, these risk factors may only partially explain the high prevalence of cardiovascular disease. The presence of Chlamydia pneumoniae within atherosclerotic lesions has been documented and may be an additional risk factor for the development and progression of cardiovascular disease.

CONCLUSIONS

The results of primary and secondary prevention trials have shown conflicting evidence with regard to the beneficial effects of antibiotic therapy to reduce cardiovascular events. Currently, the lack of certainty in published data does not support the use of antibiotics for the prevention of cardiovascular disease. Clinicians should continue to emphasize interventions proven to reduce adverse cardiovascular events such as smoking cessation, reduction of hyperlipidemia, and control of hypertension.

Chlamydia pneumoniae and atherosclerosis -- what we know and what we don't

The clinical manifestations of atherosclerosis include coronary artery disease (CAD), stroke, abdominal aortic aneurysm and peripheral vascular disease. World-wide, CAD and stroke are the leading causes of death and disability. The recognition of atherosclerosis as an inflammatory disease in its genesis, progression and ultimate clinical manifestations has created an interesting area of vascular research. Apart from those well-known traditional risk factors for atherosclerosis, novel and potentially treatable atherosclerotic risk factors such as homocysteine (an amino acid derived from the metabolism of dietary methionine that induces vascular endothelial dysfunction) and infections have emerged. In fact, the century-old 'infectious' hypothesis of atherosclerosis has implicated a number of micro-organisms that may act as contributing inflammatory stimuli. Although cytomegalovirus, Helicobacter pylori and Chlamydia pneumoniae are the three micro-organisms most extensively studied, this review will focus on C. pneumoniae. Collaborative efforts from many disciplines have resulted in the accumulation of evidence from seroepidemiological, pathological, animal model, immunological and antibiotic intervention studies, linking C. pneumoniae with atherosclerosis. Seroepidemiological observations provide circumstantial evidence, which is weak in most prospective studies. Pathological studies have demonstrated the preferential existence of C. pneumoniae in atherosclerotic plaque tissues, while animal model experiments have shown the induction of atherosclerosis by C. pneumoniae. Finally, immunological processes whereby C. pneumoniae could participate in key atherogenic and atherothrombotic events have also been identified. Although benefits of the secondary prevention of atherosclerosis have been demonstrated in some antibiotic intervention studies, a number of negative studies have also emerged. The results of the ongoing large prospective human antibiotic intervention trials may help to finally establish if there is a causal link between C. pneumoniae infection and atherosclerosis.