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Biomedical subjects

E K Chung

Publications and source records attributed to E K Chung.

At least 19 recordsLinked to original sources
PubMed1979

Runaway pacemaker. Unpredictable pacemaker failure.

The runaway pacemaker is an uncommon but very serious complication of permanent artificial pacemakers. Although the runaway pacemaker has been most frequently encountered in older (fixed rate) pacemakers, this problem has also been reported in various types of newer models manufactured by different companies. The most striking finding in our case is that the pacemaker was reported by a reliable pacemaker follow-up service to be working normally only one week before the development of the malfunction. The extremely rapid pacing rate (750 beats per minute) was a manifestation of a far-advanced runaway pacemaker. The manufacturer believes that this is the first reported incident of a runaway pacemaker in this model. This indicates that the runaway pacemaker is still a potential problem, even in newer pacemakers, and reemphasizes the unpredictable and serious nature of this medical emergency.

Aged↗
PubMed1978

Sick sinus syndrome due to cardiac amyloidosis.

In a patient suffering from cardiac amyloidosis a case of sick sinus syndrome, manifested by markedly prolonged recovery time of the sinus node, was documented by an atrial pacing study. The first A-V junctional escape interval was markedly prolonged following the termination of the atrial pacing, pointing to a coexisting A-V nodal dysfunction. The patient required a permanent artificial pacemaker implantation.

Amyloidosis↗
PubMed1977

Wolff-Parkinson-White Syndrome--current views.

The Wolff-Parkinson-White (WPW) syndrome is an important clinical entity because of frequent recurrences of very rapid tachyarrhythmias. The electrocardiographic finding of the WPW syndrome often mimicks pseudo diaphragmatic (inferior) myocardial infarction which should not be misinterpreted. The most important diagnostic criterion is recognition of a delta wave; the short P-R interval or broad QRS complex may not be present in every case. The mechanism for the tachycardia is considered to be a reentry phenomenon via anomalous and normal atrioventricllar (A-V) pathways. The drug of choice for the treatment of regular supraventricular (reciprocating) tachycardia with narrow QRS complexes, which is the most common arrhythmia in the WPW syndrome, is propranolol. Digitalis is almost equally effective in this case. For tachyarrhythmias, particularly atrial fibrillation or flutter with anomalous conduction, intravenously-administered lidocaine is considered to be the drug of choice. Procainamide or quinidine is also frequently used under this circumstance with excellent therapeutic result. Many patients with the WPW syndrome require long-term maintenance drug therapy (propranolol, digitalis or quinidine in most cases). In urgent clinical situations, direct current (DC) shock should be applied immediately. In selected patients with refractory tachyarrhythmias, the use of an artificial pacemaker or surgical approach may be considered.

Anti-Arrhythmia Agents↗
PubMed1977

Drug-induced cardiovascular diseases.

A wide variety of drugs may be associated with serious cardiovascular toxicity. Toxicity due to drugs primarily used for treating cardiovascular toxicity. Toxicity due to drugs primarily used for treating cardiac disorders is the most extensively documented, especially the arrhythmias due to digitalis glycosides. Various arrhythmias are also caused by toxic levels of many antiarrhythmic agents including quinidine, procainamide and phenytotin. Myocardial depression and heart failure are serious side-effects of beta-adrenoceptor blocking agents and myocardial ischaemia due to sympathominetic amines may result from both direct and indirect mechanisms. The many toxic reactions in the cardiovascular system due to non-cardiac drugs are less widely known and for the most part less clearly understood. Many remain controversial at the current time; for example, the diathesis toward thromboembolism in women taking oral contraceptives. Potential cardiac toxicity due to drugs used in the rapidly expanding sphere of anti-neoplastic chemotherapy is exemplified by the cardiomyopathy-like toxicities of doxorubicin and daunorubicin. Many of the psychotherapeutic drugs including phenothiazine antipsychotics and tricyclic antidepressants have arrhythmogenic potential.

Adrenal Cortex Hormones↗
PubMed1976

Unusual electrocardiographic finding--bifascicular block due to hyperkalemia.

A unique case in which the patient had bifascicular block consisting of right bundle branch block and left posterior hemiblock as a result of marked hyperkalemia is presented. To our knowledge, this is the first reported case in which such unusual electrocardiographic abnormalities due to hyperkalemia were demonstrated. The electrocardiographic abnormalities produced by hyperkalemia in this case disappeared promptly by hemodialysis, as the serum potassium level returned to normal. It has been stressed that hyperkalemia should be considered as an important etiologic factor in the differential diagnosis of bundle branch block, hemiblocks and bifascicular block, particularly when these intraventricular blocks are produced suddenly.

Bundle-Branch Block↗
PubMed1976

Coexisting ventricular and blocked atrial parasystole.

A rare instance showing non-conducted atrial parasystole coexisting with ventricular parasystole is presented and a related subject is briefly discussed. The importance of recognizing parasystole is again emphasized because the ordinary extrasystoles, particularly ventricular in origin, are frequently digitalis-induced, while parasystole, which superficially resembles the ordinary extrasystoles, does not seem to be related to digitalis.

Cardiac Complexes, Premature↗
PubMed1976

Artificial cardiac pacing. 1. Indications.

With increasing use of artificial cardiac pacing, criteria for selection of patients have been refined. In general, the most important indication for pacing is the presence and severity of symptoms due to bradyarrhythmias. Use of pacing in acute myocardial infarction remains controversial, but some guidelines are presented here.

Acute Disease↗
PubMed1976

Artificial cardiac pacing: 2. follow-up and complications.

Following insertion or implantation of an artificial cardiac pacemaker, both physician and patient are involved in aftercare to monitor the patient's cardiac status, the condition of the implantation site, and the function of the pacemaker. Among the complications that may occur are pacemaker malfunction and perforation of the ventricles. The physician and patient must also be alert to the possibility of electrical interference and to the physiologic factors that can modify pacemaker function.

Arrhythmias, Cardiac↗
PubMed1975

Reappraisal of hemiblock.

The left bundle branch separates into the left anterior and the left posterior divisions. The impulse travels to the left ventricle via both divisions when they are intact. When one division is blocked, the diagnosis is hemiblock. Diagnostic criteria for left anterior hemiblock are marked left axis deviation, small Q wave in lead I and small R wave in lead III, little or no prolongation of the QRS interval, and no evidence of other causes of left axis deviation. Criteria for left posterior hemiblock are marked right axis deviation, small R wave in lead I and small Q wave in lead III, little or no prolongation of the QRS interval, and no evidence of other causes of right axis deviation. A pure form of hemiblock is not uncommon, especially during acute anterior myocardial infarction, but right bundle-branch block often coexists with hemiblock. Like left bundle-branch block, hemiblocks rarely occur in healthy persons. They are commonly associated with coronary or hypertensive disease or both and are less commonly associated with cardiomyopathies and calcified aortic disease.

Bundle-Branch Block↗
PubMedDate not supplied

Pacemaker bigeminy: pseudomalfunction.

The first reported unique case of atrial synchronized pacemaker-induced bigeminy is described and related literature is briefly discussed. The arrhythmia reported in this case can be erroneously misinterpreted as a malfunctioning pacemaker unless the physician is fully familiar with the specific nature of the atrial synchronized pacemaker. By recognizing this type of pacemaker bigeminy as an arrhythmia simply related to a normally functioning pacemaker, unnecessary surgery can be avoided.

Aged↗
PubMedDate not supplied

Reciprocal beats initiated by artificial pacemaker.

In conclusion, the underlying mechanism for this rhythm disturbance in our patient is the re-entry phenomenon, which is dependent upon a localized unidirectional block in the A-V junction. The predisposing factors, including digoxin and Inderal which tend to prolong A-V conduction, are considered for the mechanism of the production of the reciprocal beats in our case. Upon temporary withdrawal of digoxin and Inderal, the re-entry phenomenon has disappeared.

Aged↗
PubMedDate not supplied

Ventricular pseudo-bigeminy due to sustained myoclonus.

An elderly unconsciocus patient with anteroseptal myocardial infarction showing ventricular pseudo-bigeminy (artifact) due to sustained myoclonus is reported. The reason why the artifacts coincided with his cardiac contraction is not clearly understood. The artifact is completely eliminated following intravenous injection of succinylcholine chloride. This is the first reported case of such a puzzling electrocardiographic finding to our knowledge. It is extremely important to distinguish between a true and pseudo-arrhythmia. Otherwise, an erroneous diagnosis frequently leads to an erroneous therapeutic approach.

Aged↗