Interaction between bacteria and cholesterol crystals: Implications for endocarditis and atherosclerosis.

BACKGROUND: The interaction between pathogenic bacteria and cholesterol crystals (CCs) has not been investigated. However, CCs are found extensively in atherosclerotic plaques and sclerotic cardiac valves. Interactions between pathogenic bacteria and CCs could provide insights into destabilization of atherosclerotic plaques and bacterial adhesion to cardiac valves. METHODS: Staphylococcus aureus and Pseudomonas aeruginosa were used to assess in vitro bacterial adhesion to CCs and proliferation in the presence of CCs compared to plastic microspheres and glass shards as controls. Ex vivo studies evaluated bacterial adhesion to atherosclerotic rabbit arteries compared to normal arteries and human atherosclerotic carotid plaques compared to normal carotid arteries. Scanning electron microscopy (SEM) was used to visualize bacterial adhesion to CCs and confocal microscopy was used to detect cholesterol binding to bacteria grown in the presence or absence of CCs. RESULTS: In vitro, S. aureus and P. aeruginosa displayed significantly greater adhesion, 36% (p<0.0001) and 89% (p<0.0001), respectively, and growth upon exposure to CCs compared to microspheres or glass shards. Rabbit and human atherosclerotic arteries contained significantly greater bacterial burdens compared to controls (4× (p<0.0004); 3× (p<0.019), respectively. SEM demonstrated that bacteria adhered and appeared to degrade CCs. Consistent with this, confocal microscopy indicated increased cholesterol bound to the bacterial cells. CONCLUSIONS: This study is the first to demonstrate an interaction between bacteria and CCs showing that bacteria dissolve and bind to CCs. This interaction helps to elucidate adhesion of bacteria to sclerotic valves and atherosclerotic plaques that may contribute to endocarditis and plaque destabilization.

External validation of the HIT Expert Probability (HEP) score.

The diagnosis of heparin-induced thrombocytopenia (HIT) can be challenging. The HIT Expert Probability (HEP) Score has recently been proposed to aid in the diagnosis of HIT. We sought to externally and prospectively validate the HEP score. We prospectively assessed pre-test probability of HIT for 51 consecutive patients referred to our Consultative Service for evaluation of possible HIT between August 1, 2012 and February 1, 2013. Two Vascular Medicine fellows independently applied the 4T and HEP scores for each patient. Two independent HIT expert adjudicators rendered a diagnosis of HIT likely or unlikely. The median (interquartile range) of 4T and HEP scores were 4.5 (3.0, 6.0) and 5 (3.0, 8.5), respectively. There were no significant differences between area under receiver-operating characteristic curves of 4T and HEP scores against the gold standard, confirmed HIT [defined as positive serotonin release assay and positive anti-PF4/heparin ELISA] (0.74 vs 0.73, p = 0.97). HEP score ≥ 2 was 100 % sensitive and 16 % specific for determining the presence of confirmed HIT while a 4T score > 3 was 93 % sensitive and 35 % specific. In conclusion, the HEP and 4T scores are excellent screening pre-test probability models for HIT, however, in this prospective validation study, test characteristics for the diagnosis of HIT based on confirmatory laboratory testing and expert opinion are similar. Given the complexity of the HEP scoring model compared to that of the 4T score, further validation of the HEP score is warranted prior to widespread clinical acceptance.

Statin therapy in the reduction of cardiovascular events in patients undergoing intermediate-risk noncardiac, nonvascular surgery.

BACKGROUND: Hydroxymethylglutaryl-coenzyme A reductase inhibitors (statins) reduce perioperative cardiac events in high-risk patients undergoing cardiovascular surgery. However, there is paucity of data on the role of statins in patients undergoing intermediate-risk noncardiac, nonvascular surgery (NCNVS). HYPOTHESIS: Statins are cardioprotective in intermediate-risk NCNVS. METHODS: We identified a retrospective cohort of patients undergoing intermediate risk NCNVS. Our composite end point (CEP) included 30-day all-cause mortality, atrial fibrillation (AF), and nonfatal myocardial infarction (MI). A stepwise logistic regression with adjustment using propensity scores was performed to determine if statin therapy was independently associated with the risk reduction of adverse postoperative cardiovascular outcomes. RESULTS: We identified 752 patients. Seventy-five of them (9.97%) developed composite end points; 10 (1.33%) had in-hospital nonfatal MI, 44 (5.85%) developed AF, and 35 (4.65%) died within 30 days. The 30-day all-cause mortality was 31/478 (6.48%) among statin nonusers vs 4/274 (1.45%) for statin users (P < 0.002). As compared with nonusers, patients on statin therapy had a 5-fold reduced risk of 30-day all-cause mortality. Statin therapy was associated with decreased CEP after adjusting for baseline characteristics, with a propensity score to predict use of statins (odds ratio [OR]: 0.54, 95% confidence interval [CI]: 0.30-0.97, P = 0.039). After further adjustment for propensity score, diabetes mellitus, percutaneous coronary intervention, and prior coronary artery bypass grafting, statin therapy proved beneficial (OR: 0.51, 95% CI: 0.28-0.92, P = 0.026). CONCLUSIONS: Statin use in the perioperative period was associated with a reduction in cardiovascular adverse events and 30-day all-cause mortality in patients undergoing intermediate-risk NCNVS.

Cerebrovascular steal phenomenon in a patient undergoing dipyridamole nuclear perfusion cardiac imaging.

Transient ischemic neurological deficits following intravenous dipyridamole administration during pharmacological cardiac stress test are seldom reported, but there can be serious vascular complications. We report a case of a 58-year-old Caucasian male who developed expressive aphasia after dipyridamole infusion during an elective dipyridamole-technetium cardiac stress test performed for chest pain. Computed tomography angiogram of the neck revealed a known total occlusion of the right internal carotid artery and 50% stenosis of the left internal carotid artery. The patient's aphasia spontaneously resolved within 24 h. In this paper, we report a unique case in which the administration of intravenous dipyridamole precipitated transient ischemic attack in a patient with stable asymptomatic bilateral carotid artery disease and prior carotid endarterectomy. We also discuss the intracerebral vascular steal phenomenon as a possible pathophysiological mechanism in this patient.

Coronary artery fistula: a case series with review of the literature.

Coronary artery fistula (CAF) is an anomalous connection between a coronary artery and a major vessel or cardiac chamber. Most of the coronary fistulas are discovered incidentally during angiographic evaluation for coronary vascular disorder. The management of CAF is complicated and recommendations are based on anecdotal cases or very small retrospective series. We present three cases of CAF, two of which were symptomatic due to hemodynamically significant coronary steal phenomenon. They underwent successful transcatheter coil embolization, leading to resolution of their symptoms. Percutaneous closure offers a safe and effective way for the management of symptomatic patients. CAFs are rare cardiac anomalies but can give rise to a variety of symptoms because of their hemodynamic consequences or complications. They should be part of cardiac differential diagnosis particularly in patients without other risk factors. Correction of CAF is indicated if the patients are symptomatic or if other secondary complications develop.