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Biomedical subjects

W D Weaver

Publications and source records attributed to W D Weaver.

At least 163 records · Page 9Linked to original sources
PubMed1985

Amplitude of ventricular fibrillation waveform and outcome after cardiac arrest.

The amplitude of ventricular fibrillation found initially in 394 patients was compared to clinical and logistical findings at the time of cardiac arrest. Peak-to-peak amplitude averaged 0.55 +/- 0.25 mV; a very low amplitude (0.2 mV or less) or "fine" fibrillation was present in 66 patients (17%). The amplitude was not found to be related to clinical histories, but depended on the length of the period from collapse until start of basic life support (p = 0.004) and the delay until assessment by paramedics (p = 0.001). Survival rates were strongly associated with amplitude: only 4 patients (6%) with fine ventricular fibrillation survived, compared to 117 or 328 patients (36%) in whom the initial amplitude was higher (p less than 0.001). Patient outcome related to amplitude even after adjusting for clinical history and logistical delays (p less than 0.005). We conclude that fine ventricular fibrillation is in part the result of delay in initiation of treatment, and that fibrillation amplitude is a powerful indicator of outcome after cardiac arrest.

Aged↗
PubMed1984

Considerations in the long-term management of survivors of cardiac arrest.

The heterogeneity of resuscitated patients at risk of recurrent cardiac arrest serves to make their management difficult and complex. It is logical that therapy should be tailored to each patient and certainly to the mechanism whereby sudden cardiac death occurred. It is important, also, to recognize that not all resuscitated victims are at high risk for recurrence and that aggressive interventions are not necessarily mandatory. In the patient with cardiac arrest related to transient myocardial ischemia, a direct approach toward relieving ischemia seems appropriate. Antiarrhythmic agents may have a role in the treatment of some patients, but to this date the efficacy of such therapy is speculative, at best. The development and testing of agents that have "antifibrillatory" properties seems a logical approach at this time. Clearly, efforts to lessen the mortality of patients who have been resuscitated from out-of-hospital cardiac arrest are important, not only for the particular patients themselves, but also in an effort to develop rational, prophylactic interventions for the large numbers of patients with coronary heart disease who are at risk for the development of sudden cardiac death.

Adrenergic beta-Antagonists↗
PubMed1984

Improved neurologic recovery and survival after early defibrillation.

Eighty-seven patients who had out-of-hospital cardiac arrests received defibrillating shocks delivered by minimally trained first responders before the arrival of paramedics in a city with short emergency response times. Their outcomes were compared with those of 370 other victims who received only basic life support by first responders until paramedics arrived. Survival was improved by early defibrillation in cases in which there was a delay in initiating cardiopulmonary resuscitation and in which paramedic response times exceeded 9 min; there was 62% survival after early defibrillation by first responders and 27% if first responders provided only basic life support (p less than .02). Neurologic recovery was also improved after early defibrillation. Eighteen of 46 resuscitated patients (39%) receiving early defibrillation were awake at 24 hr compared with 49 of 204 patients (24%) who received only basic life support while awaiting paramedics (p less than .02). Incorporating defibrillation as part of basic life support can reduce both mortality and morbidity from cardiac arrest, even in cities with established, rapidly responding emergency care systems.

Allied Health Personnel↗
PubMed1984

Effects of light and feeding space on leg abnormalities in broilers.

The influence of two management factors on the incidence and severity of leg abnormalities was studied in three experiments utilizing a total of 7200 male broiler chickens. Birds provided intermittent illumination (IL) had significantly fewer and less severe leg abnormalities than birds under continuous illumination. Broilers given 2.94 cm of feeding space per bird had more but less severe leg defects than birds given 1.47 cm of feeding space. Bird activity was greater under IL and is deemed to be at least partially responsible for the stronger legs recorded among broilers under this management practice.

Animal Husbandry↗
PubMed1984

Ventricular fibrillation causes sudden death in Southeast Asian immigrants.

Young, male, Southeast Asian immigrants living in the United States have a high incidence of unexplained, sudden, nocturnal death. We report the cases of three patients, two Laotians and one Filipino, who were resuscitated and subsequently studied extensively. Each patient was having ventricular fibrillation when first examined by paramedics outside the hospital, and episodes of fibrillation recurred in the early hospital course. Clinical evaluation found no significant coronary atherosclerosis or structural cardiac disease. One patient is asymptomatic after 2 years; the second patient died suddenly at 4 months; and the third is asymptomatic but had inducible ventricular tachycardia on electrophysiologic testing 6 months after resuscitation. The mechanism of sudden death in young Southeast Asian men appears to be ventricular fibrillation. The cause of the arrhythmia is unclear, although in our patients the arrhythmia was not an isolated event; underlying predispositions to further cardiac arrest persisted.

Adult↗
PubMed1983

Tc-99m PYP scanning following low voltage electrical injury.

An adolescent boy sustained low voltage electrical injury to his extremities when he inadvertently touched a low tension (440 volts) wire with a metal tube. Early in his hospital course, he was evaluated with Tc-99m pyrophosphate whole body scanning for the extent of his injuries. The scintigraphic findings correlated well with his subsequent clinical course.

Child↗
PubMed1982

Ventricular defibrillation -- a comparative trial using 175-J and 320-J shocks.

We compared the effects of initial electrical shocks using 175 and 320 J (joules) in 249 patients with ventricular fibrillation. Survival was unrelated to the energy level used for defibrillation. Reversion to an organized rhythm occurred in a similar proportion of both treatment groups after one or two shocks. The rhythm identified after the first shock was related to outcome (the survival rate was 42 per cent in patients with supraventricular rhythm, 30 per cent in persistent ventricular fibrillation, 26 per cent in idioventricular rhythm, and 14 per cent in asystole; P less than 0.02). Fibrillation recurred in 68 per cent of patients who had been initially defibrillated to an organized rhythm. Repeated shocks at the higher energy level resulted in a higher incidence of atrioventricular block after defibrillation (24 per cent of patients receiving 320 J and 9 per cent of those receiving shocks of lower energy; P less than 0.005). Patients who survived required fewer shocks than patients who later died in the hospital (2.6 shocks as compared with 3.6; P less than 0.005). We conclude that initial defibrillatory shocks using 175 J are as safe and effective as shocks of nearly twice that energy level.

Electric Countershock↗
PubMed1982

Termination of ventricular tachycardia by programmed extrastimuli from an externally-activated permanent pacemaker.

Two patients with hemodynamically well-tolerated recurrent ventricular tachycardia, drug resistant and previously requiring numerous external electrical cardioversions, had a permanent pacemaker implanted which could be programmed to deliver extrastimuli to convert the ventricular tachycardia to normal sinus rhythm. The patient- or physician-activated device can be programmed to induce or terminate ventricular tachycardia with extrastimuli delivered at the predetermined intervals which consistently induced or terminated the arrhythmia in the electrophysiology laboratory, allowing repeated evaluation of drug regimens. The pacemaker has reliably, painlessly, and consistently induced and terminated repeated episodes of ventricular tachycardia. This programmable pacemaker offers an alternative therapy for patients with hemodynamically well-tolerated refractory ventricular tachycardia.

Aged↗
PubMed1982

Ambulatory arrhythmias in resuscitated victims of cardiac arrest.

One hundred forty-four patients with coronary heart disease previously resuscitated from out-of-hospital ventricular fibrillation underwent 24-hour ambulatory ECG monitoring 5 months (median) after cardiac arrest. Patients were then followed for an average of 31.7 months. Fifty-one patients died, 32 from subsequent unexpected cardiac arrest. One hundred twenty-nine patients (90%) had uniform ventricular ectopy. Two-thirds had complex ventricular ectopy (Bigeminy/trigeminy, repetitive forms or frequent multiforms). Complex ectopy, present in 20% or more of the 30-minute recording intervals, occurred in 18 of the patients (56%) who developed subsequent cardiac arrest, compared with 26 of 92 (28%) who survived (P less than 0.005, specificity 72%, relative risk 2.3). Other forms of ventricular ectopy, e.g., uniform, multiform and repetitive beats, were more sensitive but less specific predictors of death or recurrent ventricular fibrillation. Complex ventricular ectopy was associated with certain clinical histories: it occurred in 95% of patients with a history of congestive heart failure and in 79% with remote myocardial infarction, compared with 59% and 56% without these histories (p less than 0.001 and p less than 0.01). As expected, mortality was also greater in patients who had these clinical characteristics. Complex ectopy was related to mortality regardless of the clinical history.

Ambulatory Care↗
PubMed1977

Myocardial imaging and radionuclide angiography in survivors of sudden cardiac death due to to ventricular fibrillation: preliminary report.

Twenty-one long-term survivors of out of hospital sudden cardiac death due to ventricular fibrillation underwent radionuclide angiography and myocardial imaging with thallium-201. In 13 patients images were obtained at rest and after maximal treadmill exercise; 11 of these 13 (85 percent) had an image defect in one or both studies. Eleven of the 21 patients (52 percent) had a defect in the image obtained at rest. The magnitude of myocardial image defects was typically great; some patients had an image abnormality without other clinical evidence (angina, S-T depression) of ischemia. The mean ejection fraction, assessed in 16 patients with radionuclide angiography, was 0.41 +/- 0.15 (standard deviation); in 5 of the 16 ejection fraction was normal (more than 0.50) and in 3 it was severely abnormal (less than 0.25). Thus, noninvasive radionuclide studies defined a broad spectrum of ischemic and ventriculographic abnormalities in survivors of sudden cardiac death. Further application of these noninvasive studies may identify those at high risk.

Adult↗
PubMed1977

Myocardial imaging with intravenously injected thallium-201 in patients with suspected coronary artery disease: analysis of technique and correlation with electrocardiographic, coronary anatomic and ventriculographic findings.

Myocardial imaging was performed after intravenous injection of thallium-201 at rest in 50 patients with suspected coronary artery disease and the results were compared with electrocardiographic, ventriculographic and coronary arteriographic findings. The thallium-201 myocardial images were of good quality and compared favorably with images previously obtained with intracoronary particle injection. Myocardial to background ratios averaged 2:1, a considerable improvement over ratios reported with potassium-43. There was complete intra- and interobserver agreement in the interpretation of images in 90 and 82 percent of cases, respectively. Major disagreement occurred in less than 5 percent of cases. Overall, 15 (30 percent) had an abnormal, 10 patients (20 percent) a borderline abnormal and 25 patients (50 percent) a normal myocardial image. Of patients with electrocardiographic Q waves, 91 percent had an image defect. Of 39 patients without Q waves, 13 percent had an image defect. All 30 patients with a normal or borderline abnormal thallium-201 image had a normal ventricular contraction pattern. All patients with a segmental ventriculographic abnormality had an image defect. In all cases, the area of electrocardiographic or ventriculographic abnormality corresponded to the area of the thallium-201 image defect. The systolic ejection fraction was depressed (0.49 +/- 0.18 [mean +/- standard deviation]) in patients with an image defect compared with that in patients with a normal image (0.64 +/- 0.06, P less than 0.005). Coronary arterial lesions were present and usually of high grade in all patients with an abnormal image; however, the presence of high grade coronary stenosis or occlusion as such correlated with image defects only to the extent that prior myocardial infraction was associated. Thus, satisfactory myocardial images at rest appear to be obtained with intravenously administered thallium-201 and electrocardiographic, ventriculographic and coronary arteriographic data suggest that image defects denote regions of prior myocardial infarction.

Coronary Angiography↗
PubMed1976

Angiographic findigs and prognostic indicators in patients resuscitated from sudden cardiac death.

Sixty-four patients with coronary artery disease (CAD) who had been resuscitated from out-of-hospital ventricular fibrillation (VF) underwent cardiac catheterization and angiography. The majority (72%) had a previous history of cardiovascular disease; in the remaining 28%, VF was the first manifestation of CAD. Advanced coronary atherosclerosis was a common finding; 94% of the patients had severe stenoses (70% or greater diameter narrowing) in one or more of the major coronary arteries, and most (70%) had ventricular wall contraction abnormalities. In over half of the patients, coronary anatomy was potentially suitable for complete revascularization. During an average follow-up period of 20.4 months, fourteen of the 64 patients developed a second episode of VF and/or died suddenly (VF/SD). In an attempt to identify characteristics which might be of prognostic value, the clinical, hemodynamic, and angiographic characteristics of this group were compared to those patients who had a single episode of VF and survived during follow-up. Patients who developed recurrent VF/SD had more triple vessel CAD (P less than 0.01), lower ejection fractions (P less than 0.05), and far more severe abnormalities of left ventricular contraction (P less than 0.001). These results indicate that angiographic findings can identify individuals at high risk for recurrent VF and also suggest that myocardial scarring may be an important factor in the initiation of ventricular fibrillation and in its recurrence.

Adult↗
PubMedDate not supplied

Clinical studies with the new glycosylated recombinant prourokinase.

Recombinant prourokinase (r-ProUK) is a single-chain urokinase-type plasminogen activator that is produced from a mammalian cell line. It is administered as a zymogen and remains inactive until converted to the active two-chain form on the surface of a clot. The clot specificity of this agent, therefore, is conferred by the site of conversion to the active form on the surface of the clot. Two pilot studies were conducted to evaluate the safety and efficacy of r-ProUK in patients with acute myocardial infarction. In the first study, the 90-minute patency rate was 66.7% in 21 patients receiving 60 mg over 60 minutes and 72.2% in 18 patients receiving 60 mg over 90 minutes. In the second study, the 90-minute patency rates were 45.5% in the group primed with recombinant urokinase who were given 60 mg of r-ProUK infused over 60 minutes (11 patients) and 80.8% in the primed group given 60 mg infused over 90 minutes (26 patients). Only 4.6% of patients experienced severe bleeding complications, with no patient developing intracranial hemorrhage. These two studies describe the first application of r-ProUK in patients. Although two doses were selected for evaluation, the small number of patients studied did not permit the selection of one dose as superior to the other. The results, however, did indicate that r-ProUK is a very effective thrombolytic agent in achieving patency of occluded coronary arteries. It is especially effective in maintaining coronary patency, having shown only a 1.4% rate of reocclusion. Serious bleeding complications were few and no intracranial hemorrhages were noted in this group of 131 patients. Additional clinical trials will be needed to compare the efficacy of r-ProUK with that of other available thrombolytic agents.

Adult↗
PubMedDate not supplied

Planning, implementation, and process monitoring for prehospital 12-lead ECG diagnostic programs.

Prehospital 12-lead electrocardiographic (ECG) diagnostic strategies have been proven feasible and effective, provided they are designed and implemented properly. The authors of this communication have expended considerable time and effort in determining appropriate planning, implementation, and process monitoring necessary for successful implementation of a variety of prehospital diagnostic strategies. Many of these issues may not be obvious to an emergency medical services (EMS) director initiating a 12-lead ECG program. This level of attention to protocol development, education, training, inservice education, coordination of the health-care community, objective program assessment, monitoring and continuous quality improvement can serve as a model for other diagnostic EMS programs that may develop as an expanded role for EMS.

Electrocardiography↗
PubMedDate not supplied

TNK-tissue plasminogen activator compared with front-loaded alteplase in acute myocardial infarction: results of the TIMI 10B trial. Thrombolysis in Myocardial Infarction (TIMI) 10B Investigators.

BACKGROUND: Bolus thrombolytic therapy is a simplified means of administering thrombolysis that facilitates rapid time to treatment. TNK-tissue plasminogen activator (TNK-tPA) is a highly fibrin-specific single-bolus thrombolytic agent. METHODS AND RESULTS: In TIMI 10B, 886 patients with acute ST-elevation myocardial infarction presenting within 12 hours were randomized to receive either a single bolus of 30 or 50 mg TNK-tPA or front-loaded tPA and underwent immediate coronary angiography. The 50-mg dose was discontinued early because of increased intracranial hemorrhage and was replaced by a 40-mg dose, and heparin doses were decreased. TNK-tPA 40 mg and tPA produced similar rates of TIMI grade 3 flow at 90 minutes (62.8% versus 62.7%, respectively, P=NS); the rate for the 30-mg dose was significantly lower (54.3%, P=0.035) and was 65. 8% for the 50-mg dose (P=NS). A prespecified analysis of weight-based TNK-tPA dosing using median TIMI frame count demonstrated a dose response (P=0.001). Similar dose responses were observed for serious bleeding and intracranial hemorrhage, but significantly lower rates were observed for both TNK-tPA and tPA after the heparin doses were lowered and titration of the heparin was started at 6 hours. CONCLUSIONS: TNK-tPA, given as a single 40-mg bolus, achieved rates of TIMI grade 3 flow similar to those of the 90-minute bolus and infusion of tPA. Weight-adjusting TNK-tPA appears to be important in achieving optimal reperfusion; reduced heparin dosing appears to improve safety for both agents. Together with the safety results from the parallel Assessment of the Safety of a New Thrombolytic: TNK-tPA (ASSENT I) trial, an appropriate dose of this single-bolus thrombolytic agent has been identified for phase III testing.

Aged↗