Biomedical subjects
Publications and source records attributed to L Lemberg.
The relationship of platelet aggregation to coronary and cerebral ischemic attacks has been well established. A number of clinical trials have shown that the daily use of aspirin 160 to 325 mg daily, dipyridamole 300 to 400 mg daily, or both are effective in preventing platelet aggregation, and results in a statistically significantly reduction in the incidence of coronary events and transient ischemic cerebral attacks.
A wide QRS complex tachycardia that cannot be immediately identified, and which on clinical grounds requires prompt treatment, should be converted electrically. Drug management can be time consuming, and agents that block AV transmission, that is, verapamil and propranolol, may be life-threatening.
Rapid and progressive improvement in techniques and decreased morbidity and mortality rates have taken place since the introduction in 1977 of PTCA for the treatment of coronary artery disease. PTCA is now performed worldwide. Originally used for proximal single-vessel disease, which is still the ideal lesion, criteria for PTCA have expanded to include multiple stenotic lesions in one or more vessels, distally located obstructive lesions, patients with prior coronary artery bypass surgery, and patients with acute myocardial infarction where PTCA is performed in combination with streptokinase lysis of an obstructive thrombus.
Alterations in serum potassium levels are not uncommon in this era of wide use of diuretics, potassium supplements, and potassium-sparing drugs. Familiarity with the characteristic electrocardiographic changes related to abnormal serum levels of potassium is necessary in the care of patients in intensive care units.
Antiarrhythmic drugs are associated with a significant incidence of arrhythmogenic effects, as well as other cardiac and extracardiac side effects. Thus, it is important that the decision to treat ventricular arrhythmias be made on the bases of the frequency of the arrhythmia, its qualitative features, and the presence or absence of underlying heart disease. These features influence the risks of sudden arrhythmogenic death.
Thromboembolic complications are a major problem in patients with atrial fibrillation. This vignette presents the probabilities of thromboembolism in the various etiologies of atrial fibrillation and prophylactic management with anticoagulants.
The clinical implications and use of an AICD are presented. This device is still under investigation, but has proved to be highly successful in trials to date.
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The potential arrhythmogenic effects of alcohol have recently been studied electrophysiologically. These experiments have confirmed clinical observations that alcohol in modest doses has the potential of producing atrial or ventricular arrhythmias. Although many of the patients have underlying heart disease, there are reports of patients with no evident heart disease where acute alcohol injestion has caused arrhythmias. This sequence of events, i.e., cause and effect, has been referred to as the "holiday heart" syndrome.
One of several mechanisms may be responsible for the arrhythmia in patients with attacks of SVT. When conventional therapy is ineffective in preventing the attacks and when the attacks occur frequently, then electrophysiologic studies should be performed. These studies help determine the mechanism of the arrhythmia and provide the means for testing antiarrhythmic drugs for prophylactic use. When drugs fail, sophisticated, specially designed antiarrhythmic pacemakers can be used when the electrophysiologic mechanisms are known.
The pacemaker 12-lead electrocardiogram accurately assesses the location of the pacing catheter tip. The electrocardiogram is the only instrument that determines whether an artificial pacemaker functions normally.
When ventricular pacemakers are implanted in patients who still retain normal AV conduction, retrograde conduction may activate the atria after ventricular activation. This results in a retrograde flow of blood from the ventricles to the atria with flooding of the jugular and pulmonary veins. Weakness or syncope can then occur as a result of lower cardiac output or congestive heart failure. A change to a dual-chamber pacemaker that produces AV synchrony is often necessary.
Familiarity with the more sophisticated modes of pacing is necessary to determine normal pacemaker function. A thorough knowledge of all functions of a pacemaker is required to interpret and manage pacemaker-induced arrhythmias.
Knowledge of the programmed parameters of an artificial pacemaker is critical to the accurate assessment of pacemaker function, especially with the use of an AV universal (DDD) pacemaker. In addition, each manufacturer's idiosyncrasies regarding pacemaker function have to be appreciated to intelligently monitor the rhythm of a state-of-the-art pacemaker.
Coronary thrombolysis with streptokinase infusion can be achieved if performed during the first 4 hours of the onset of myocardial infarction. It has been a consistent finding that lysis of the thrombus can reestablish angiographically documented, antegrade coronary flow. Restoration of blood flow and preservation of ischemic myocardium can be achieved after coronary thrombolysis. Coronary artery bypass surgery or percutaneous transluminal coronary angioplasty may be necessary when significant obstructive coronary artery lesions due to atherosclerotic plaques remain after successful thrombolysis.
Immersing the patient's face in cold water to induce the "diving reflex" is a quick and simple method of treating paroxysmal supraventricular tachycardia. Patients can be trained to perform the "diving reflex" at home. There are many advantages to this method of treatment when compared to many of the other therapies. Polyuria up to 3 L is often noted during the first 90 minutes of a paroxysmal tachycardia. The diuresis is thought to be due to atrial distention with resultant inhibition of antidiuretic hormone secretion.
Amiodarone is an investigative antiarrhythmic drug in the United States. However, it has been used successfully in European countries for the past 14 years. Amiodarone is effective in the long-term management of resistant supraventricular and ventricular arrhythmias. Although a very useful addition to the antiarrhythmic drugs currently in use, it has potential side effects that have delayed its acceptance by the Food and Drug Administration. The consensus of opinion among the clinical investigators of amiodarone is that it will be released for limited clinical use in the near future. Cardiovascular nurses involved in the design, coordination, and conduction of clinical investigations need to be vigilant in objectively monitoring and documenting both the potential efficacy and possible adverse effects of all interventions in research subjects.