Failure in short-term prediction of ventricular tachycardia and ventricular fibrillation from continuous electrocardiogram in intensive care unit patients.

BACKGROUND: Patients in the intensive care unit (ICU) setting are prone to malignant ventricular arrhythmias. We sought to test whether electrocardiographic (ECG) markers of autonomic tone, ventricular irritability, and repolarization lability could be used in short-term prediction of ventricular arrhythmias in this patient population. METHODS: We studied 38 patients with sustained (>30 seconds) monomorphic ventricular tachycardia, polymorphic ventricular tachycardia, or ventricular fibrillation while monitored in the ICU and 30 patients without arrhythmia in the ICU who served as controls. All patients had at least 12 hours of continuously recorded multilead ECG before arrhythmic event. Mean heart rate and measures of heart rate variability, QT variability, and ventricular ectopy were quantified in 1-hour epochs for the 12 hours before the arrhythmic event and in 5-minute epochs for the last hour preevent (and using a random termination time point in controls). RESULTS: A modest downward trend in QT variability and a rise in heart rate were observed hours before polymorphic ventricular tachycardia and ventricular fibrillation events, although no significant changes heralded monomorphic ventricular tachycardia and no changes in any parameter predicted imminent ventricular arrhythmia of any type. There were no significant differences in ECG parameters between arrhythmia patients and controls. CONCLUSIONS: In ICU patients, sustained ventricular arrhythmias are not preceded by change in ECG measures of autonomic tone, repolarization variability, and ventricular ectopy. Short-term arrhythmia prediction may be difficult or impossible in this patient population based on ECG measures alone.

The prognostic importance of comorbidity for mortality in patients with stable coronary artery disease.

OBJECTIVES: To identify the prevalent and prognostically important coexisting illnesses among single coronary artery disease (CAD) patients. BACKGROUND: As the population ages, physicians are increasingly required to make decisions concerning patients with multiple co-existing illnesses (comorbidity). Many trials of CAD therapy have excluded patients with significant comorbidity, such that there are limited data to guide the management of those patients. METHODS: To consider the long-term prognostic importance of comorbid illness, we examined a cohort of 1471 patients with CAD who underwent cardiac catheterization between 1985 and 1989 and were followed up through 2000 in the Duke Databank for Cardiovascular Diseases. Weights were assigned to individual diseases according to their prognostic significance in Cox proportional hazards models, thus creating a new CAD-specific index. The new index was compared with the widely used Charlson index, according to prevalence of conditions, individual and overall associations with survival, and agreement. RESULTS: The Charlson index and the CAD-specific index were highly associated with long-term survival and almost equivalent to left ventricular ejection fraction. When considering the components of the Charlson index, diabetes, renal insufficiency, chronic obstructive pulmonary disease, and peripheral vascular disease had greater prognostic significance among CAD patients, whereas peptic ulcer disease, connective tissue disease, and lymphoma were less significant. Hemiplegia, leukemia, lymphoma, severe liver disease, and acquired immunodeficiency syndrome were rarely identified among patients undergoing coronary angiography. CONCLUSIONS: Comorbid disease is strongly associated with long-term survival in patients with CAD. These data suggest co-existing illnesses should be measured and considered in clinical trials, disease registries, quality comparisons, and counseling of individual patients.

A simplified approach to the management of non-ST-segment elevation acute coronary syndromes.

CONTEXT: While current practice guidelines provide an evidence-based approach to management of acute coronary syndromes (ACS), application of the evidence by individual physicians has been suboptimal. OBJECTIVE: To assess and synthesize the evidence regarding optimal management of non-ST-segment elevation ACS (NSTE-ACS). DATA SOURCES: Systematic searches of peer-reviewed publications were performed in MEDLINE and the Cochrane Database from January 1990 through November 2004, with consultation by content experts. Search terms included antiplatelet therapy, antithrombotic therapy, angiotensin-converting enzyme inhibition, angiotensin receptor blockade, beta-blockade, hypertension, hyperlipidemia, cigarette smoking, diet, diabetes mellitus, exercise, myocardial ischemia, and coronary artery disease. STUDY SELECTION AND DATA EXTRACTION: Criteria for selection of studies included controlled study design, English language, and clinical pertinence. Data quality was based on the publishing journal and relevance to clinical management of NSTE-ACS. DATA SYNTHESIS: While outcomes of controlled studies support a comprehensive approach in the management of patients with NSTE-ACS, many physicians perceive existing guidelines as lengthy and complex. After risk stratification to identify those patients most likely to benefit from an early invasive vs early conservative strategy, a comprehensive management plan can be assembled through an "ABCDE" approach. The elements of this include "A" for antiplatelet therapy, anticoagulation, angiotensin-converting enzyme inhibition, and angiotensin receptor blockade; "B" for beta-blockade and blood pressure control; "C" for cholesterol treatment and cigarette smoking cessation; "D" for diabetes management and diet; and "E" for exercise. CONCLUSION: An "ABCDE" approach for the management of NSTE-ACS provides a practical and systematic means to implement evidence-based medicine into clinical practice.

Effect of fenfluramine-derivative diet pills on cardiac valves: a meta-analysis of observational studies.

BACKGROUND: Fenfluramine-derivative diet pills were withdrawn from the market in 1997 because of an association with valvular regurgitation, but subsequent estimates of the prevalence of this condition have varied widely. We systematically reviewed evidence regarding the prevalence of valvular disease after fenfluramine exposure. METHODS: We searched multiple databases with multiple search terms. Conference proceedings from 1997 onward were searched by index. Authors of eligible studies were contacted to identify unpublished works. Selection criteria were liberally determined. Ten of the identified 11 articles met these criteria. Reviewers assessed the studies' methodologic quality by use of a standard form to evaluate selection, attrition, performance, and detection bias. The studies were analyzed in 2 groups on the basis of length of exposure (<90 days or >90 days). The Mantel-Haenszel method was used to summarize data. Quantitative and qualitative tests for heterogeneity were performed. Tests for publication bias were also done. RESULTS: Tests for heterogeneity were nonsignificant after removing 1 outlier trial. The pooled prevalence of valvular regurgitation meeting Food and Drug Administration criteria (at least mild aortic regurgitation or at least moderate mitral regurgitation) among patients treated for >90 days was 12.0% compared with 5.9% for the unexposed group (prevalence odds ratio 2.2, 95% CI 1.7-2.7). The combined analyses also identified a small but statistically significant increase in mitral regurgitation not previously identified by individual studies (exposed 3.5%, unexposed 1.8%, prevalence odds ratio 1.6, 95% CI 1.05-2.3). Among patients exposed for <90 days, a trend toward more regurgitation was not statistically significant by either combined Food and Drug Administration criteria (exposed 6.8%, unexposed 5.8%, prevalence odds ratio 1.4, 95% CI 0.8-2.4) or by individual valve. CONCLUSIONS: These data indicate that fenfluramine-associated valvular regurgitation is less common than initially reported, but still present in 1 of 8 patients treated for >90 days.

Imaging techniques for diagnosis of infective endocarditis.

With the ability to structurally characterize cardiac manifestations, echocardiography is used for the diagnosis and management of infective endocarditis. In establishing the diagnosis according to the Duke criteria, the findings of endocardial involvement (vegetation, abscess, prosthetic valve dehiscence) or new valvular regurgitation represent "major" diagnostic criteria. As echocardiography cannot reliably differentiate noninfective from infective lesions, however, proper diagnosis lies in correlating echocardiography with clinical findings. The more invasive transesophageal approach provides substantially greater image resolution; this approach should be considered first in the evaluation of patients with higher prior probabilities of endocarditis and those with potential endocardial complications.

Imaging techniques for diagnosis of infective endocarditis.

Cardiac imaging, specifically echocardiography, has greatly enhanced the ability of clinicians to effectively diagnose and manage IE. Echocardiograms should generally be obtained in all patients suspected of having IE, both to establish the diagnosis and to identify complicated cardiac involvement that may warrant surgical intervention. Transesophageal imaging is more sensitive and specific than the transthoracic approach and currently represents the optimal approach to echocardiographic imaging. Manifestations of endocardial involvement include vegetations, abscesses, aneurysms, fistulae, leaflet perforations, and valvular dehiscence. The roles of other imaging modalities including CT, MRI, and nuclear imaging have yet to be fully established.

Impact of international normalized ratio and activated clotting time on unfractionated heparin dosing during ablation of atrial fibrillation.

BACKGROUND: For ablation of atrial fibrillation, it is unclear how baseline international normalized ratio (INR) affects the dosing of unfractionated heparin (UFH). METHODS AND RESULTS: A retrospective review of 170 consecutive patients undergoing atrial fibrillation ablation with baseline activated clotting time (ACT) and INR values was performed. Patients were grouped according to INR <2.0 (G<2; n=129) and INR ≥2.0 (G≥2; n=41). Clinical variables, UFH doses, and ACT values were recorded. An equation was derived to calculate the first bolus of UFH required to achieve an ACT ≥300 seconds, and this was subsequently assessed in 168 patients. For the initial 170 patients, the baseline INR (2.47±0.31 versus 1.53±0.31) and ACT (185±26 versus 153±30 seconds) were significantly greater in G≥2 (P<0.001). The amount of UFH to achieve the first ACT ≥300 seconds was significantly higher for G<2 versus G≥2 (9701±2390 versus 8268±2366 U; P=0.0001). Baseline INR, ACT, and weight were predictors of the UFH dosage to achieve an ACT ≥300 seconds. An equation derived to achieve an ACT ≥300 seconds after a single bolus of UFH met this end point in 160 of 168 patients (95%). CONCLUSIONS: Baseline INR and ACT, in addition to weight, are the only predictors of UFH dosage needed to achieve an ACT ≥300 seconds. A derived equation predicted the UFH dosage to achieve an ACT ≥300 seconds.

Should Atrial Fibrillation Burden Be A Feature to Guide Thromboembolism Prophylaxis?

Atrial fibrillation (AF) is a well-known risk factor for cerebrovascular events and systemic emboli. However, the frequency and duration of AF necessary to be considered at risk for thrombus formation is unknown. This review summarizes the literature regarding AF burden and risk for thromboembolism. Previously, no distinction was made between patients who had paroxysmal versus persistent AF in regards to initiation of anticoagulation. Recently though, given an enhanced ability to detect even very brief paroxysms of AF via stored device diagnostics, the issue has been readdressed. However, despite multiple studies no clear threshold for AF burden to mandate anticoagulation has been established. In addition, there is a growing body of evidence which suggests that the pathophysiology of thrombus formation in AF involves mechanisms beyond just stasis due to protracted episodes of discoordinate atrial contraction. Therefore, once AF has been diagnosed and the risk-benefit ratio favors anticoagulation, therapy should be initiated and continued indefinitely unless a bleeding contraindication develops. ABBREVIATIONS: AF = atrial fibrillation, AT = atrial tachycardia, LAA = left atrial appendage, PAF = paroxysmal atrial fibrillation, SE = systemic emboli.