Platelet activation during dobutamine stress echocardiography

Complications of exercise and pharmacologic stress echocardiography

Stress echocardiography is a diagnostic cardiovascular exam that is commonly utilized for multiple indications, including but not limited to the assessment of obstructive coronary artery disease, valvular disease, obstructive hypertrophic cardiomyopathy, and diastolic function. Stress echocardiography can be performed via both exercise and pharmacologic modalities. Exercise stress is performed with either treadmill or bicycle-based exercise. Pharmacologic stress is performed via either dobutamine or vasodilator-mediated (i.e., dipyridamole, adenosine) stress testing. Each of these modalities is associated with a low overall prevalence of major, life-threatening adverse outcomes, though adverse events are most common with dobutamine stress echocardiography. In light of the recent COVID-19 pandemic, the risk of infectious complications to both the patient and stress personnel cannot be negated; however, when certain precautions are taken, the risk of infectious complications appears minimal. In this article, we review each of the stress echocardiographic modalities, examine major potential adverse outcomes and contraindications, assess the risks of stress testing in the setting of a global pandemic, and examine the utilization and safety of stress testing in special patient populations (i.e., language barriers, pediatric patients, pregnancy).

[Prethrombus acute constitution during dobutamine stress echocardiography]

Although generally regarded as a safe stress modality, dobutamine stress echocardiography (DSE) has been associated with several well described complications. However, to our knowledge, acute constitution of thrombi during the stress test has never been described. In this report, we present the case of a 64 year-old man with a history of ischemic heart disease who underwent a preoperative DSE; during the test, we witnessed a striking acute constitution of an intense prethrombotic state with almost a formation of a highly mobile massive thrombus adjacent to the infero-apical segment spontaneously resolving few minutes after the end of the test.

Circulating Microparticles Decrease After Cardiac Stress in Patients With Significant Coronary Artery Stenosis

BACKGROUND

Cardiac stress leads to a dynamic increase of circulating microparticles (MPs) in healthy individuals that is diminished in individuals with vascular disease. The impact of coronary ischemia on circulating MP level is unknown. This study investigates the kinetics of circulating MPs during cardiac stress in patients with coronary artery stenosis.

HYPOTHESIS

Patients with significant coronary stenosis show altered circulating MP levels after cardiac stress.

METHODS

Eighty patients with stable coronary artery disease underwent dobutamine stress echocardiography (DSE) on the day before coronary angiography. Before, immediately after, at 4 hours, and at 24 hours after DSE, blood was drawn to determine CD144⁺ endothelial microparticles (EMPs), CD14⁺ CD16⁺ monocyte-derived microparticles (MMPs), and CD31⁺ CD42b⁺ platelet microparticles. A significant stenosis was defined as stenosis diameter ≥70% in a major native epicardial coronary artery with a diameter of ≥2.5 mm.

RESULTS

Significant coronary artery stenoses were found in 41 patients. In these patients, CD144⁺ -EMP and CD14⁺ CD16⁺ -MMP concentrations decreased immediately after DSE. Stimulation of target endothelial cells with sera from patients with significant coronary artery stenoses significantly augmented endothelial capacity to take up EMPs, but not MMPs, in vitro. Serum-induced enhancement of endothelial phosphatidylserine receptor expression was found as a potential mechanism of increased endothelial EMP uptake and subsequently reduced circulating EMP levels after cardiac stress.

CONCLUSIONS

Cardiac ischemia leads to reduced circulating MP levels under cardiac stress. Changes of endothelial MP uptake capacities could be one possible mechanism.

Dynamic release and clearance of circulating microparticles during cardiac stress

RATIONALE

Microparticles are cell-derived membrane vesicles, relevant to a range of biological responses and known to be elevated in cardiovascular disease.

OBJECTIVE

To investigate microparticle release during cardiac stress and how this response differs in those with vascular disease.

METHODS AND RESULTS

We measured a comprehensive panel of circulating cell-derived microparticles by a standardized flow cytometric protocol in 119 patients referred for stress echocardiography. Procoagulant, platelet, erythrocyte, and endothelial but not leukocyte, granulocyte, or monocyte-derived microparticles were elevated immediately after a standardized dobutamine stress echocardiogram and decreased after 1 hour. Twenty-five patients developed stress-induced wall motion abnormalities suggestive of myocardial ischemia. They had similar baseline microparticle levels to those who did not develop ischemia, but, interestingly, their microparticle levels did not change during stress. Furthermore, no stress-induced increase was observed in those without inducible ischemia but with a history of vascular disease. Fourteen patients subsequently underwent coronary angiography. A microparticle rise during stress echocardiography had occurred only in those with normal coronary arteries.

CONCLUSIONS

Procoagulant, platelet, erythrocyte, and endothelial microparticles are released during cardiac stress and then clear from the circulation during the next hour. This stress-induced rise seems to be a normal physiological response that is diminished in those with vascular disease.

Ventricular Fibrillation in Late Recovery After Dobutamine Stress Echocardiography

A 62-year-old man with multiple cardiac risk factors, including diabetes mellitus type II, treated hypertension, and hyperlipidemia, had a dobutamine stress echocardiogram performed as part of a preoperative evaluation. At peak stress the patient developed an apical regional wall motion abnormality. Approximately 12 minutes into the recovery period, the patient developed ventricular tachycardia that degenerated into ventricular fibrillation. He was successfully resuscitated and underwent emergency coronary angiography that showed a 95% distal left anterior descending coronary artery stenosis.

P-selectin expression, but not GPIIb/IIIa activation, is enhanced in the inflammatory stage of Takayasu's arteritis

BACKGROUND

Inflammation and thrombosis are closely related processes, but the association between disease activity and thrombogenicity in Takayasu's arteritis (TA) is poorly understood. To investigate the link between platelet activation and disease activity, flow cytometric analyses of platelet P-selectin and activated GPIIb/IIIa expression were performed in patients with TA.

METHODS AND RESULTS

Twenty-two patients with TA, classified into active (Group A, n = 9) and inactive (Group I, n = 13) according to blood-derived inflammatory markers, and 14 healthy age- and gender-matched controls (Group C) were studied. Compared with Group C, the mean fluorescence intensity of P-selectin in response to 0.1-10 micromol/L of ADP was significantly upregulated in Group A, but not in Group I. No differences in platelet GPIIb/IIIa expression in stimulated platelets were seen among the 3 groups. Standard platelet aggregation studies revealed that disease activity did not influence platelet aggregation by ADP.

CONCLUSIONS

P-selectin expression, but not activated GPIIb/IIIa, is enhanced in ADP-activated platelets from patients in the inflammatory stage of TA. P-selectin may play a significant role in the inflammatory and thrombotic responses associated with intractable TA, presumably by inducing platelet-leukocyte interactions.

Echocardiography in the evaluation of patients in chest pain units

Using percutaneous angioplasty to induce the ischemic cascade in the cardiac catheterization laboratory, echocardiographic wall motion abnormalities have been documented to precede electrocardiographic abnormalities and angina. Therefore, detection of cardiac wall motion abnormalities is potentially more sensitive than the history, physical examination, and ECG for identification of myocardial ischemia. Echocardiography is highly reliable for assessing cardiac wall motion and, thus, it has been used for diagnosis and risk assessment in patients presenting to the emergency department (ED) with symptoms suggestive of myocardial ischemia. In patients who have acute ST-elevation myocardial infarction (MI), echocardiography is comparable to invasive left ventriculography for detecting wall motion abnormalities. However, the usefulness of echocardiography in the low-risk population that has chest pain of uncertain origin and a nondiagnostic initial presentation is less well established.

Stimulation of Staphylococcus epidermidis growth and biofilm formation by catecholamine inotropes

BACKGROUND

Bacterial colonisation of indwelling medical devices by coagulase-negative staphylococci is a prevalent risk in intensive-care units. Factors determining biofilm formation and progression to catheter- related infection are incompletely understood. We postulated that administration of inotropic agents via indwelling intravenous catheters may stimulate growth and formation of biofilms by Staphylococcus epidermidis.

METHODS

Inocula representing physiologically relevant infecting doses of S epidermidis were incubated in a minimum medium supplemented with fresh human plasma in the presence or absence of pharmacological concentrations of norepinephrine or dobutamine. Biofilm formation on polystyrene and medical-grade silicone was examined. After incubation, cultures were assessed for growth and formation of biofilms by colony counting and scanning electronmicroscopy. The production of exopolysaccharide, a major constituent of S epidermidis biofilms, was also assessed by use of immunofluorescence microscopy.

FINDINGS

Incubation of S epidermidis with catecholamine inotropes in the presence of human plasma resulted in a significant increase in growth compared with control on both polystyrene and silicone surfaces, with pronounced increases in biofilm formation as visualised by scanning electronmicroscopy. Experiments with transferrin labelled with radioactive iron showed the ability of catecholamine inotropes to facilitate acquisition of iron by S epidermidis. Immunofluorescence microscopy revealed extensive exopolysaccharide production associated with S epidermidis biofilms.

INTERPRETATION

The ability of catecholamine inotropic drugs to stimulate bacterial proliferation and biofilm formation may be an aetiological factor in the development of intravascular catheter colonisation and catheter-related infection. The removal of iron from transferrin for subsequent use by S epidermidis is a possible mechanism by which catecholamine inotropes stimulate bacterial growth as biofilms.

Dobutamine stress echocardiography: safety in diagnosing coronary artery disease

Dobutamine stress echocardiography is considered a relatively well-tolerated diagnostic modality, effective in the management of patients with known or suspected coronary artery disease. Adverse effects during testing are relatively frequent, precluding the achievement of a diagnostic end-point in about 5 to 10% of tests. These adverse effects, mostly tachyarrhythmias and arterial hypotension, are usually minor and self limiting. However, severe life-threatening complications, as well as death, also occur. By analysing Medline-quoted literature up to March 1999, we found 35 original studies from a single institution with more than 100 patients, as well as 2 multicentre studies, concerning the feasibility and safety of dobutamine stress echocardiography. In a cumulative total of 26438 tests performed, 79 life-threatening complications (such as acute myocardial infarction, asystole, ventricular fibrillation, sustained ventricular tachycardia or severe symptomatic hypotension) have been reported, giving an incidence of 1 severe adverse reaction per every 335 examinations. In addition, 29 isolated case reports have been published describing life-threatening complications during dobutamine echocardiography. In case reports, 2 deaths have been described, both due to acute cardiac rupture in patients with recent inferior myocardial infarction. Severe adverse reactions during dobutamine echocardiography can be ischaemia independent, and are independent of operator experience and are unpredictable; some complications can be late occurring and long lasting. As a consequence, the procedure must be clearly indicated, written informed consent has to be obtained from the patient, an attending physician must be present during testing, and long term observation of outpatients is useful in order to manage late complications. In conclusion, while the safety of dobutamine stress echocardiography was reported to be outstanding in early reports, further experience presents a substantially more worrying picture. This must be taken into account by both physicians and patients when assessing the risk-benefit profile of the procedure.

Pharmacologic stress echocardiography in the assessment of coronary artery disease

Pharmacologic stress echocardiography has gained widespread popularity in recent years because it is more feasible for the patient and less technically demanding for the echocardiographer than exercise stress testing. The two most popular pharmacologic stresses are dobutamine and dipyridamole. These agents provide similar prognostic value and diagnostic accuracy for angiographically assessed coronary artery disease; dobutamine has marginally higher sensitivity in single-vessel disease, and dipyridamole has marginally higher specificity in patients with normal coronary arteries. Both stresses are safe, but a physician should always be in attendance when they are administered: Life-threatening reactions can occur in one of 300 to 500 cases with dobutamine and in one of 700 to 1500 cases with dipyridamole. For dipyridamole and dobutamine echocardiography, outcome data are available from multicenter, international, observational, prospective studies, such as the EPIC (Echo Persantine International Cooperative) and EDIC (Echo Dobutamine International Cooperative).