PubMed Health⌕ Search

Biomedical subjects

E L Michelson

Publications and source records attributed to E L Michelson.

At least 19 recordsLinked to original sources
PubMed1992

Thrombolytic therapy of acute myocardial infarction. Keeping the unfulfilled promises.

OBJECTIVE: To assess the use of thrombolytic therapy for acute myocardial infarction, evaluating whether inclusion and exclusion criteria should be altered as well as the public health implications of any such alterations. DATA SOURCES: Data obtained were from English-language articles on the use of thrombolytic therapy in acute myocardial infarction. Articles that reported on inclusion and exclusion criteria as well as specific complications of this therapy were specifically sought. The review included articles under the terms thrombolytic therapy and acute myocardial infarction in the National Library of Medicine's MEDLINE database. STUDY SELECTION: Studies selected for detailed review were those reporting specifics about inclusion and exclusion criteria and efficacy. Data extraction guidelines for assessing data quality included study size, patient population, detail of patient information acquired, and consecutive patient enrollment. DATA SYNTHESIS: Thrombolytic therapy can provide substantial decrements of morbidity and mortality of acute myocardial infarction in the subset of patients who receive this therapy, but is underused in the United States. Advanced age per se should not be an exclusion criterion. Improvements can be made in electrocardiographic diagnosis of acute myocardial infarction. Many of the clinical conditions initially excluded from thrombolytic consideration, such as hypertension or having received cardiopulmonary resuscitation, are only relative contraindications. The benefit/risk ratio in treatment of these patients is often acceptable. Several well-documented points of delay from onset of symptoms to treatment can be minimized, and accelerated therapy can result in a reduction in mortality rates. CONCLUSION: Significant public health benefits will result from greater use of thrombolytic therapy in acute myocardial infarction.

Contraindications↗
PubMed1991

Calcium antagonists in cardiology: update on sustained-release drug delivery systems.

One limitation of standard oral formulations of calcium antagonists has been the need for multiple daily dosing. Sustained-release dosage forms permit simpler regimens and a smoother therapeutic effect. Differences in drug pharmacokinetic and pharmacodynamic properties have led to development of several sustained-release delivery systems. Three major types are available: the osmotic pump, coated pellet, and slow-dissolving material released from a matrix. Each is currently utilized with specific calcium antagonists. The osmotic pump system with nifedipine (Procardia XL, Pfizer) allows once-daily dosing as well as improvements in certain side effects. Verapamil is available in formulations employing dissimilar release systems. The original sustained-action products (Calan SR, Searle; Isoptin SR, Knoll) utilize a matrix system; a subsequent product (Verelan; Lederle, Wyeth-Ayerst, A. H. Robins) utilizes timed-release pellets. Importantly, clinical efficacy appears to be maintained with these several drugs and formulations for their approved indications. Although a specific formulation may alter the absorption, metabolism, excretion, and blood levels of a drug, it does not alter basic drug properties. Thus, the major impact of sustained-release drug delivery system lies in potential compliance improvement and possible reduction of side effects related to serum drug profiles.

Calcium Channel Blockers↗
PubMed1991

Clinical pharmacology education in a division of cardiology.

A working model of how clinical pharmacology education can be interwoven into the matrix of an academic cardiology program that includes didactic teaching, clinical research, and patient care has been presented. Essential to the success of such a program is the commitment and dedication of both its full-time and voluntary faculty. Moreover, a comprehensive plan of organization and allocation of efforts is vital to the success of such a complex undertaking. As we look to the future, the discipline of clinical pharmacology will be increasingly relevant to the practicing cardiologist.

Cardiology↗
PubMed1979

Ethmozin: a new antiarrhythmic agent developed in the USSR. Efficacy and tolerance.

Ethmozin, a phenothiazine derivative, was developed in the Soviet Union as a new antiarrhythmic agent. We evaluated ethmozin using a controlled single-blinded in-hospital protocol in 14 ambulatory patients with ventricular ectopy ranging from an average of 48 to 1,801 depolarizations per hour and in eight patients with atrial ectopy ranging from 63 to 693 depolarizations per hour. Placebo was administered for the first 3 days, followed by ethmozin from 2.4 to 11.2 mg./Kg./day administered orally every 8 hours for 7 days and concluding with placebo for the final 3 days. Continuous 24-hour long-term electrocardiographic monitoring for 13 days was employed to measure drug efficacy accurately. Six of eight (75 per cent) patients with atrial ectopy and 10 of 14 (71 per cent) patients with ventricular ectopy had statistically significant reductions in ectopy during ethmozin therapy. Atrial ectopy was reduced at a lower dose and plasma level of ethmozin than was ventricular ectopy. With the exception of mild nausea in one patient, no side effects of ethmozin therapy were noted. Ethmozin appears to be a well-tolerated, effective antiarrhythmic agent with a dosage regimen that can promote patient compliance for long-term use.

Adult↗
PubMed1979

Ventricular tachycardia terminated by carotid sinus massage.

Carotid sinus massage affects supraventricular arrhythmias primarily through vagotonic effects on the sinus and AV nodes, but vagal innervation of the ventricle also exists and has been shown to have functional significance. The case presented here illustrates an unusual example of a ventricular tachycardia that was repeatedly converted to normal sinus rhythm by carotid sinus massage following administration of digoxin. The clinician should be aware that a wide QRS-complex tachycardia that responds to carotid sinus massage is not necessarily supraventricular in origin.

Carotid Sinus↗
PubMed1979

Recurrent sustained ventricular tachycardia. 4. Pleomorphism.

Two or more morphologically distinct ventricular tachycardias were observed during electrophysiologic study in 14 patients with chronic sustained ventricular tachycardia. Nine of these patients had clinical ventricular tachycardia with multiple morphologies. During the study 13 patients manifested both right bundle branch block (RBBB) and left bundle branch block (LBBB) morphologies. The remaining patient had RBBB with both right and left axis deviation. Changing morphologies were observed spontaneously in four patients and could be produced in all 14 by ventricular stimulation. In 12 patients both RBBB and LBBB originated in the left ventricle, and in 11 of these patients, from within a left ventricular aneurysm. Diastolic fragmented activity representing reentry was unchanged during both morphologies in four patients and during one morphology in five patients. Epicardial mapping confirmed the aneurysm as the site of origin of multiform ventricular tachycardias in two patients. Our data suggest that 1) ventricular tachycardia is frequently pleomorphic; 2) multiple morphologies usually represent variable exit sites and/or ventricular activation during the same tachycardia; and 3) there is a frequent association of pleomorphic ventricular tachycardia with left ventricle aneurysm.

Aneurysm↗
PubMed1979

Electrophysiologic study of the left ventricle: indications and safety.

Eighty patients (69 with documented or suspected recurrent ventricular tachycardia or fibrillation, ten with left bundle-branch block, and one with the Wolff-Parkinson-White syndrome) underwent both right ventricular and left ventricular programmed electrical stimulation, including ventricular pacing and the introduction of one or two ventricular extrastimuli or electrode catheter mapping of the left ventricle (or both). Left ventricular catheters were introduced precutaneously via the femoral artery (of 61 patients, one required secondary repair) or via brachial arteriotomy (of 19 patients, two required secondary repair). All patients received an intravenously administered bolus of hep arin (5,000 units) following the insertion of the left ventricular catheter and then 1,000 units/hr after the first hour of study. No patients had cerebrovascular, systemic thromboembolic, or cardiac sequelae. In four (12 percent) of 34 patients with inductible ventricular tachycardia, programmed electrical stimulation of the left ventricle was required for initiation. Extensive left ventricular endocardial mapping was performed in 45 patients. Our experience suggests that (1) electrophysiologic study of the left ventricle can be performed safely, (2) programmed electrical stimulation of the left ventricle is indicated when a suspected ventricular tachyarrhythmia cannot be induced from the right ventricle, and (3) endocardial mapping of the left ventricle is indicated when surgery is being considered to abolish recurrent sustained ventricular tachycardia.

Adolescent↗
PubMed1979

Multiple cardiac output measurements in man. Evaluation of a new closed-system thermodilution method.

Cardiac output estimates by a new closed-system automatic injection thermodilution method (COI-TD) were compared serially with the direct Fick technique (COFICK) and the standard open-system manual injection thermodilution method (COTD). Comparison with cardiac outputs determined simultaneously by the direct Fick technique in 100 measurements involving ten patients showed close agreement with the new closed system method using both 25 degrees C and 3 degrees C injectates. The cardiac output range was between 1.9 to 11.6 L/min. The open-system manual injection thermodilution method under identical conditions produced a wide scatter of measurements when compared to the direct Fick technique. Reproducibility of simultaneous COI-TD and COTD measurements was examined in quadruplicate. The reproducibility of measurements was within 1.9 percent with COI-TD and 5.9 percent with the COTD method using both 25 degrees C and 3 degrees C injectates. The COI-TD method eliminates the technical problems of recirculation, unstable indicator baseline changes, thermal continuity, and reproducibility encountered with the current COTD method. Analysis of cardiac output by the closed-system automatic injection thermodilution method provides a simple, rapid, reproducible, and highly accurate method for multiple cardiac output measurements suitable for use at the bedside.

Cardiac Catheterization↗
PubMed1979

Retinal arteriolar changes as an indicator of coronary artery disease.

Funduscopic examination was performed in 70 non diabetic, nonhypertensive patients without valvular heart disease undergoing coronary angiography for evaluation of chest pain syndromes to determine if retinal arteriolar changes could reliably predict presence of coronary artery disease. Retinal arteriolar changes were graded with respect to light reflex, vessel caliber, arteriovenous crossing defects, and vessel tortuosity without knowledge of angiographic findings. Each coronary vessel was graded with respect to its most occlusive lesion by angiography; coronary index was derived for each patient without knowledge of eye findings. Abnormal light reflex changes were the most sensitive indicators of presence and extent of coronary artery disease. Abnormal vessel tortuosity and decreased caliber were less sensitive but more specific; their presence also suggested more extensive coronary lesions. Thus, funduscopic examination demonstrating specific retinal arteriolar lesions may indicate presence of coronary artery disease and may correlate with extent of lesions in selected patients.

Adult↗
PubMed1978

Fascicular conduction distrubances after coronary bypass surgery.

Two hundred patients underogoing coronary bypass graft surgery were studied to determine the frequency and significance fo new fascicular conduction distrubances. The follow-up period ranged from 13 to 39 months. New disturbances developed in 39 patients (20 percent). Isolated right bundle branch block (6 percent) and left anterior hemiblock (6 percent) were the most common disturbances. Righ bundle branch block was usually transient and was not associated with further complications in the follow-up period. However, patients with either transient or persistent left bundle branch block or left anterior hemiblock, or both, had (1) increased later mortality compared with patients without new fascicular conduction disturbances (5 of 26 versus 11 of 161; P less than 0.02), and (2) increased late myocardial infarction (2 of 26 versus 2 of 161; P less than 0.05). New left fascicular conduction disturbances after coronary surgery identified a subset of patients with more extensive ischemic heart disease, suggesting that these patients require close follow-up care.

Adult↗
PubMed1978

Sustained ventricular tachycardia: evidence for protected localized reentry.

The components of the reentrant circuit were evaluated in 26 patients in whom sustained ventricular tachycardia could be reproducibly initiated or terminated, or both. Observations suggesting that the proximal His-Purkinje system was not a requisite component included (1) lack of requirement for retrograde His-Purkinje delay or bundle branck reentry, or both, for initiation of the tachycardia: (2) anterograde depolarization of the His bundle during ventricular tachycardial without alteration of the QRS configuration or cycle length; and (3) the presence of random retrograde His potentials during the tachycardia. Evidence that the reentrant circuit was localized to a small area of the ventricles included (1) the ability to capture large segments of the ventricles transiently or continuously with occurrence of intermittent or continuous supraventricular capture either spontaneously or with atrial pacing without effect on the tachycardia. These findings suggest that the reentrant circuit must be small, electrocardiographically silent and relatively protected.

Adolescent↗
PubMed1978

The limitations of epicardial mapping as a guide to the surgical therapy of ventricular tachycardia.

The adequacy of intraoperative epicardial mapping as a guide to surgical procedures performed to terminate ventricular arrhythmias was investigated. Ligation of the anterior septal or left anterior descending coronary artery in 28 dogs produced ventricular arrhythmias that were studied 24-36 hours following occlusion. The sites of origin of 26 tachycardias were determined to be in the subendocardium by using extensive epicardial, endocardial and intramural mapping techniques and were verified by demonstrating unaltered activation sequences during pacing from these earliest sites. Epicardial breakthrough followed earliest directly recordable ventricular activity by as little as 7 msec. Without endocardial mapping many of these tachycardias would have been incorrectly identified as originating in the fascicles or epicardium. The sites of epicardial breakthrough were anatomically distant from the sites of origin by a markedly varying extent (5mm to 6cm). Two rhythms might be close in their sites of earliest epicardial appearance yet distant on the endocardium or vice versa. We conclude that epicardial mapping may not be sufficient to identify or predict the origins of many ventricular tachycardias and that the success of surgery to abolish these arrhythmias may be enhanced by preoperative and intraoperative endocardial mapping.

Animals↗
PubMed1978

Limitations of routine long-term electrocardiographic monitoring to assess ventricular ectopic frequency.

Variations in the frequency of ventricular premature depolarizations (VPDs) were evaluated with three consecutive 24-hour long-term electrocardiography monitor recordings from 15 clinically stable patients with various cardiac disorders. Mean hourly VPD frequencies ranged from 37--1,801 per hour. Data were subjected to 4 and 5 factor nested analyses of variance. The extent of spontaneous variation in arrhythmia frequency that occurred in individual patients from day to day was 23%, between 8-hour periods within days was 29%, and from hour to hour was 48%. In addition, the variability between repeated three-day monitoring periods over time was quantified in five patients and found to be 37%. This analysis determined that to distinguish a reduction in VPD frequency attributable to therapeutic intervention rather than biologic or spontaneous variation alone required a greater than 83% reduction in VPD frequency if only two-24-hour monitoring periods were compared, and greater than 65% reduction if two 72-hour periods were compared. The limitations of routine 24-hour electrocardiographic monitoring must be considered in diagnostic and therapeutic decision-making.

Adult↗
PubMed1978

Fixed coupling: different mechanisms revealed by exercise-induced changes in cycle length.

Fixed coupled ventricular premature depolarizations (VPDs) are usually considered reentrant; recent experimental models have demonstrated that parasystolic rhythms may also appear in fixed coupled patterns. To analyze the mechanisms of fixed coupled VPDs, 60 exercise tests were chosen to evaluate the response of VPD coupling intervals to changes in cycle length of the dominant supraventricular rhythm. Selection criteria included the presence of frequent, unifocal VPDs that were fixed coupled (variation less than or equal to 80 msec) at any one cycle length, with the persistence of VPDs at several different cycle lengths. Three patterns of response of coupling intervals to changes in cycle length were noted: 1) 32 patients with a direct linear relation (r greater than or equal to 0.9) of coupling intervals to cycle length; 2) 16 patients with coupling intervals fixed, independent of cycle length; and 3) 12 patients with no consistent relation over a wide range of cycle lengths. Two patients in group 2 and four in group 3 fulfilled criteria for parasystole with interectopic intervals that remained constant at different cycle lengths. These results suggest that VPDs in group 1 are reentrant, while some patients with group 2 or 3 responses have evidence for parasystolic rhythms. We conclude that 1) fixed coupling of VPDs is not diagnostic of reentry, and 2) changes in cycle length induced with exercise may be useful in the analysis of mechanisms of VPDs.

Adolescent↗
PubMed1978

Recurrent sustained ventricular tachycardia 3. Role of the electrophysiologic study in selection of antiarrhythmic regimens.

Twenty patients with recurrent sustained ventricular tachycardia (VT) underwent serial electrophysiological studies (EPS) 1) to determine the predictive value of the EPS in the selection of antiarrhythmic therapy, and 2) to establish the therapeutic efficacy of available antiarrhythmic agents. In each patient VT could be reproducibly initiated by programmed stimulation. After control EPS, the effects of several drugs (lidocaine, procainamide, quinidine, disopyramide and diphenylhydantoin) on the ability to initiate VT were assessed. An oral regimen was chosen on the basis of acute EPS and its effectiveness was evaluated by repeat EPS in 24--72 hours. Blood levels achieved acutely were used as guidelines to chronic therapy. In 14 patients the initiation of VT was prevented by the acute administration of one or more agents. In 13 of these patients, a chronic oral regimen based on these results prevented recurrence of VT with a three- to 27-month follow-up. In the remaining patient, oral therapy could not achieve blood levels of procainamide shown to be effective intravenously, and VT recurred. In six patients no single drug or drug combination was effective during acute EPS, and VT recurred in all while on therapy with the agent shown to make initiation of VT most difficult. Procainamide prevented VT in nine patients; quinidine in three patients; lidocaine in three patients; diphenylhydantoin in two patients; and disopyramide in one patient. The mean duration of EPS studies was 4.5 days. This study suggests that serial EPS provides rapid identification of successful antiarrhythmic therapy and can predict in which patients conventional therapy would be ineffective, thereby identifying patients requiring more aggressive modes of therapy.

Administration, Oral↗
PubMed1978

Aspirin- and coumadin-related bleeding after coronary- artery bypass graft surgery.

We studied 100 consecutive patients to evaluate the potential effect of platelet active and antithrombotic agents prescribed preoperatively on bleeding complications after coronary-artery bypass graft surgery. Preoperative hemostatic values were normal in all patients. Mean mediastinal blood loss was significantly greater in 13 patients taking aspirin (892 +/- 91 ml) and six patients taking Coumadin (warfarin sodium) (858 +/- 168 ml) within 7 days of surgery than in 64 control subjects (439 +/- 28, P less than 0.001). Less marked but similar differences (P less than 0.05) were noted with other agents inhibiting platelet function. However, in nine patients given heparin, mean mediastinal blood loss (436 +/- 61 ml) was no different from that of control subjects. The degree of mediastinal blood loss did not correlate with age, sex, mean total operative time, bypass time, or number of vessels diseased or bypassed. In addition, patients taking aspirin or Coumadin required prolonged chest tube drainage compared to those in heparin or control groups (34 +/- 4 versus 20 +/- 1 h) (P less than 0.001).

Aged↗