Biomedical subjects

Joseph C Lin

Publications and source records attributed to Joseph C Lin.

2 recordsLinked to original sources

PubMed2004

Syncope.

Syncope is a syndrome consisting of a relatively short period of temporary and self-limited loss of consciousness caused by transient diminution of blood flow to the brain (most often the result of systemic hypotension). Syncope comprises part of a subset of clinical conditions in which loss of consciousness is transient. Other conditions in this group, which are not syncope and should be clearly distinguished from syncope, include, for example, seizure disorders, posttraumatic loss of consciousness, and cataplexy. Recent surveys indicate that syncope accounts for approximately 1% of emergency department visits in Europe, although older reports from the United States placed this number closer to 3%. The reported prevalence of syncope in the population varies: 15% of children before the age of 18 years; 25% of a military population aged 17 to 26 years; 16% and 19%, respectively, in men and women aged 40 to 59 years; and up to 23% in a nursing home population older than 70 years. The highest frequency of syncope occurs in patients with cardiovascular comorbidity and older patients in institutional care settings. The causes of syncope are numerous and, not infrequently, multiple factors may contribute. The diagnostic evaluation is benefited by availability of a detailed medical history and reports of eyewitnesses. In this context, the physician must consider the classification of the causes of syncope, and address the most likely causes first. The principal groups of causes may be summarized as: (1) neurally mediated reflex syncope (eg, vasovagal faint, carotid sinus syndrome); (2) orthostatic (postural) syncope; (3) cardiac arrhythmias; (4) structural cardiac and pulmonary causes; and (5) cerebrovascular disorders (rare). In addition, conditions that may mimic syncope but are not true syncope (eg, psychogenic pseudosyncope) must be considered. Only after a definitive cause is established can appropriate treatment be initiated. In this regard, the syncope evaluation is facilitated by maintaining an organized diagnostic approach. The practitioner should avoid wasteful use of short-term ambulatory electrocardiographic recordings (eg, Holter monitors) and rarely positive neurologic tests (eg, electroencephelography, head magnetic resonance imaging/computed tomography) in the absence of head trauma or evident neurologic signs. In many medical centers the evaluation of patients with syncope is haphazard, and may be substantially enhanced by establishment of a multidisciplinary syncope evaluation unit or team.

Diagnosis, Differential↗

PubMed2003

Rates of positive cardiac troponin I and creatine kinase MB mass among patients hospitalized for suspected acute coronary syndromes.

BACKGROUND: Cardiac troponin I (cTnI) is a more specific and sensitive biomarker than creatine kinase MB (CKMB) for detection of myocardial damage. We report the prevalence of positive cTnI and CKMB mass among patients hospitalized with suspected acute coronary syndrome (ACS) and the potential impact of use of different reference cutoffs, particularly those proposed by European Society of Cardiology/American College of Cardiology (ESC/ACC) consensus guidelines, on rates of diagnosis of acute myocardial infarction (AMI). METHODS: We analyzed 1719 consecutive patients with suspected ACS admitted to an urban acute care hospital over a 6-month period. Patients (> or = 18 years of age) had at least two separate sets of plasma biomarkers (cTnI and CKMB) measured more than 12-24 h after admission to determine the potential rates of AMI based on different biomarker cutoff concentrations. RESULTS: The prevalence of cTnI-positive cases ranged from 10.6%, based on a cutoff of twice the ROC curve (cTnI < or =1.2 microg/L), to 25.0%, using the ESC/ACC-recommended 99th percentile cutoff (cTnI <0.1 microg/L). The prevalence of CKMB-positive cases ranged from 10.4%, with the cutoff of twice the ROC curve (CKMB < or =10.0 microg/L) to 21.7%, with the 99th percentile cutoff (CKMB <3.9 microg/L). Use of the 10% CV cutoff (cTnI < or =0.3 microg/L and CKMB <3.9 microg/L) instead of the ROC cutoff produced a 26% increase in all cTnI-positive cases. Use of the 99th percentile reference cutoff instead of the ROC curve-derived cutoff produced an 85% increase in all cTnI-positive cases. A substantial proportion of the increase in total cTnI-positive cases was derived from cTnI-positive/CKMB-negative cases: 71 (4.1%), 73 (4.2%), 98 (5.7%), and 209 (12.2%) of cTnI-positive cases were CKMB-negative, as determined by the twice the ROC, ROC, 10% CV, and 99th percentile reference cutoffs, respectively. At the 99th percentile cutoffs, 8.8% of cases were CKMB-positive/cTnI-negative. CONCLUSIONS: Use of lower reference cutoffs for plasma biomarkers, as recommended by ESC/ACC guidelines, markedly increases the rates of cTnI-positive cases overall. A substantial proportion of the increase in total cTnI-positive cases was derived from the creation of additional cTnI-positive/CKMB-negative cases. CKMB-positive/cTnI-negative cases are likely false positive for myocardial injury.

Adolescent↗