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Biomedical subjects

R H Falk

Publications and source records attributed to R H Falk.

At least 73 records · Page 4Linked to original sources
PubMed1992

Proarrhythmia in patients treated for atrial fibrillation or flutter.

OBJECTIVE: To review data on the type, mechanism, and prevalence of the proarrhythmic effect of drugs used to treat atrial fibrillation or flutter. DATA SOURCES: English-language literature from the early 1960s to the present was identified by manual search of the literature; relevant articles were reviewed. Pertinent earlier studies were identified from references in the articles reviewed and were included when relevant. STUDY SELECTION: All studies, controlled and uncontrolled, as well as individual case reports that contained data convincingly linking atrial antiarrhythmic therapy to a proarrhythmic side effect were included. DATA EXTRACTION: Key data were extracted from each article in studies in which a causal relationship between the use of a drug and a proarrhythmic response appeared likely. DATA SYNTHESIS: Antiarrhythmic therapy aimed at stabilizing the atrium may have adverse effects on the ventricle including torsade de pointes and, less commonly, sustained ventricular tachycardia. Different antiarrhythmic agents appear to have differing potentials for this proarrhythmic response, which is most common with class 1A agents. Other proarrhythmic responses to atrial antiarrhythmic agents include the acceleration of the ventricular response either by enhancing atrioventricular nodal or bypass tract conduction or by converting atrial fibrillation to flutter with 1:1 conduction. Calcium-channel blocking agents and, less commonly, digoxin may perpetuate the duration of paroxysmal atrial fibrillation, and virtually all agents can cause sinus node dysfunction or atrioventricular block. CONCLUSIONS: Although drug therapy for atrial fibrillation or flutter is generally well tolerated, the potential exists for uncommon but serious proarrhythmic effects. Knowledge of the risk factors and symptoms of these adverse reactions will help to further reduce this risk.

Anti-Arrhythmia Agents↗
PubMed1992

Ventricular thrombi and thromboembolism in dilated cardiomyopathy: a prospective follow-up study.

To determine the prevalence and natural history of left ventricular thrombus in dilated cardiomyopathy, we prospectively performed two-dimensional echocardiograms in 25 patients with nonischemic dilated cardiomyopathy who were not receiving anticoagulation. Eighty-five echocardiograms were performed serially over a 9- to 30-month period (mean follow-up 21.5 months). A left ventricular thrombus was present on initial echocardiogram in 11 (44%) patients, became present during follow-up in an additional four, and disappeared in two. Thrombus was significantly more common in patients with fractional shortening of less than or equal to 10% (12 of 15) than in those with a fractional shortening 11% to 25% (3 of 10) (p less than 0.02). Five embolic events (four cerebral) occurred over the follow-up period, four of which were associated with a previously visualized left ventricular thrombus. Three of five thrombi that protruded into the left ventricular cavity subsequently embolized. We conclude that in nonanticoagulated patients with dilated cardiomyopathy left ventricular thrombus and thromboembolism are common. Echocardiography may be helpful in predicting which patients are at risk of thromboembolism.

Adult↗
PubMed1992

Reproducibility of the catecholamine response to serial exercise testing in normals.

Plasma norepinephrine (NE) and epinephrine (E) increase with exercise but the reproducibility of their response to short-term serial exercise testing has not been established. Therefore, NE and E were measured at rest, 6 minutes, peak exercise, and 5 minutes postexercise in 10 normal subjects undergoing three identical exercise tolerance tests within 4-13 days. Norepinephrine and E were also measured in tests 2 and 3 at the time equivalent to the peak exercise duration in test 1 (peak--equivalent). Exercise duration increased slightly from test 1 (15.6 +/- 0.7 min) to test 2 (16.5 +/- 0.5 min; p = 0.07) but no further on test 3 (16.2 +/- 0.9 min). Norepinephrine and E did not differ across the three tests at rest, 6 minutes, peak test or posttest, but a significant decrease in both NE and E was seen at peak-equivalent by test 3 (p less than 0.05). Heart rate decreased across the three tests at 3, 6, 9, and 12 minutes (p less than 0.02 for each) and peak equivalent (p less than 0.005) but was unchanged at rest, peak exercise and postexercise. Thus, plasma catecholamines and heart rate decrease at high levels of exercise with repeated, short-term exercise testing, possibly due to familiarity with the protocol. These results suggest that control groups are important when measuring the effects of short-term pharmacologic intervention by serial exercise tests.

Adult↗
PubMed1991

Digoxin for atrial fibrillation: a drug whose time has gone?

For over 200 years digitalis compounds have been used to treat atrial fibrillation. The rapid ventricular response to atrial fibrillation is frequently treated with digoxin to produce a controlled heart rate. Digoxin has also been proposed as a treatment for terminating recent-onset atrial fibrillation, for maintaining sinus rhythm after an episode of atrial fibrillation, and as prophylactic therapy in patients with paroxysmal atrial fibrillation to prevent excessive tachycardia during a paroxysm. Perhaps because it has been used for so long, few of these indications have been studied scientifically until recently. Studies now suggest that in patients with atrial fibrillation, digoxin is a poor drug for controlling heart rate during exertion, has little or no effect in terminating the arrhythmia, and may occasionally aggravate paroxysmal atrial fibrillation. Despite adequate digitalization, the heart rate at the onset of a paroxysm of fibrillation in patients receiving the drug does not differ from the heart rate in patients not receiving it. This article discusses the current role of digoxin in the management of patients with chronic, recent-onset, or paroxysmal atrial fibrillation.

Atrial Fibrillation↗
PubMed1991

Effects of exercise on transmitral gradient and pulmonary artery pressure in patients with mitral stenosis or a prosthetic mitral valve: a Doppler echocardiographic study.

Doppler echocardiography was used to determine changes in transmitral gradient and pulmonary artery pressure after exercise in 12 patients with mitral stenosis and 11 patients with a prosthetic mitral valve. The mean transmitral gradient in the mitral stenosis group was 9 +/- 7 mm Hg at rest and increased to 17 +/- 8 mm Hg after exercise. In patients with a prosthetic mitral valve, exercise resulted in an increase in mean transmitral gradient from 5 +/- 2 to 8 +/- 3 mm Hg. Calculated pulmonary artery systolic pressure increased with exercise from 41 +/- 19 to 70 +/- 32 mm Hg in the mitral stenosis group and from 28 +/- 8 to 39 +/- 15 mm Hg in patients with a prosthetic valve. Exercise Doppler echocardiographic evaluation of changes in transmitral gradient and pulmonary artery systolic pressure was found to be technically simple and an important addition to the noninvasive evaluation of patients with mitral valve disease.

Adult↗
PubMed1990

Impact of prospective peer review on pacemaker implantation rates in Massachusetts.

Preapproval of elective permanent pacemaker insertions in Medicare patients is now mandatory for reimbursement. Of 1,860 requests for approval of an initial pacemaker implant in Massachusetts, 1,494 (80.3%) met strict Medicare guidelines and were approved by a nurse reviewer, and 366 (19.7%) were referred to an independent physician because of a question of appropriateness of indication or type of pacemaker. Only five requests (0.27%) were denied because of an inappropriate indication for pacing. On a second review of these records, an additional eight pacemaker insertions (0.43%) were deemed to have been inappropriately approved. Comparison of the annualized number of pacemaker requests for the study period with those of the 3 years before mandatory approval revealed a reduction of only 3.7%. Thus, contrary to previous findings in other areas of the country, in Massachusetts, inappropriate pacemaker insertions are rare and the effect of the prior approval process is minimal.

Heart Diseases↗
PubMed1990

Physical and intellectual recovery following prolonged hypoxic coma.

Prolonged coma resulting from hypoxic brain injury is usually associated with a dismal chance of return to independent existence. In this report a case is described of a 60 year old man who recovered and returned to work as a university professor after being in a vegetative state at least 8 weeks after a prolonged cerebral hypoxic event.

Coma↗
PubMed1989

Flecainide-induced ventricular tachycardia and fibrillation in patients treated for atrial fibrillation.

Flecainide acetate has a recognized proarrhythmic effect in patients treated for ventricular tachycardia. Three patients developed severe ventricular arrhythmias while taking flecainide for atrial fibrillation. Patient 1 had normal ventricular function and idiopathic atrial fibrillation. Treadmill exercise tests during digoxin therapy showed no ventricular arrhythmia; however, during flecainide therapy the patient developed ventricular flutter at his peak exercise level that required cardioversion. Patient 2 had normal ventricular function and a prosthetic mitral valve. During therapy with flecainide, 150 mg twice daily, he had an episode of sustained ventricular tachycardia, also at his peak exercise level. Patient 3 had paroxysmal atrial fibrillation and hypertrophic cardiomyopathy but no previous ventricular arrhythmia. She died suddenly within 10 days of starting flecainide therapy. Judged from previous findings none of these patients was considered at high risk for proarrhythmia. These cases suggest a possible relation between vigorous exercise, atrial fibrillation, and the proarrhythmic properties of flecainide and indicate the limitations of classifying patients as "high-risk" or "low-risk" for proarrhythmic complications of anti-arrhythmic therapy.

Adult↗
PubMed1988

The effect of propranolol and verapamil on external pacing threshold: a placebo-controlled study.

External transthoracic pacing is frequently used in situations where cardiac medications are administered. In view of theoretical concerns of the effects of beta-blocking and calcium channel blocking agents on pacing threshold, these agents were studied in six normal subjects over a 90 minute period during external cardiac pacing. Subjects received 10 mg propranolol, verapamil or identical placebo intravenously on 3 separate days in a double-blinded trial with serial determination of pacing threshold. Neither placebo nor either active drug altered pacing threshold. It is concluded that propranolol and verapamil have no significant effect on the threshold required for external transthoracic pacing in normal subjects and concerns about a drug induced increase in threshold may be unfounded.

Adult↗