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Biomedical subjects

J W Mason

Publications and source records attributed to J W Mason.

At least 109 records · Page 6Linked to original sources
PubMed1985

Endomyocardial biopsy.

Endomyocardial biopsy is an accepted, useful invasive tool for the analysis of human endomyocardium at the cellular and subcellular levels. It is applicable in the evaluation of specific diseases including cardiac allograft rejection, myocarditis, anthracycline cardiotoxicity, and infiltrative cardiomyopathies. The procedure can be performed in a cardiac catheterization room on an outpatient basis. The technique is quite safe when performed by trained cardiologists. Left ventricular biopsies are also safe but require systemic heparinization to prevent thromboembolization. The clinical indications for performing an endomyocardial biopsy include routine followup and suspected rejection of cardiac allograft, suspected myocarditis, monitoring or diagnosis of suspected anthracycline cardiotoxicity, and suspected secondary cardiomyopathies. Left ventricular endomyocardial biopsy is indicated for diseases that predominantly involve the left side of the heart, including left heart irradiation, cardiac fibroelastosis in infants, endomyocardial fibrosis, and scleroderma heart disease, and when right ventricular biopsy is unsuccessful. Endomyocardial biopsy is increasingly being used for research in the areas of tissue biochemistry, primary and valvular cardiomyopathies, immunology, beta receptor enzymology, drug interactions, and myocardial fibrosis. Endomyocardial biopsy has not been shown to be clinically useful in the evaluation of primary, dilated, hypertrophic, or alcoholic cardiomyopathies. These disease processes all lack pathognomomic microscopic abnormalities, and subclassification has neither been successful nor therapeutically useful. In addition, this technique is limited in diagnosing any cardiac abnormality that is not diffuse, inasmuch as only a few samples of the endomyocardial layer are obtained for evaluation. Therefore, a negative biopsy result is not 100 percent specific in excluding certain diseases. A further limitation of this technique is the need for an experienced cardiac pathologist who is well versed in interpretation of biopsy specimens. Finally, there should be a sufficiently large case load to train and to maintain skilled practitioners so that the procedure can be performed with little risk. The role of endomyocardial biopsy will continue to expand as research continues to find more uses for the technique and as more clinicians become skilled in its use.

Antibiotics, Antineoplastic↗
PubMed1984

Facilitation of ventricular tachyarrhythmia induction by isoproterenol.

Ventricular tachyarrhythmia induction was facilitated during infusion of isoproterenol in 21 of 60 patients with ventricular tachycardia (VT) or ventricular fibrillation (VF) in whom programmed electrical stimulation alone failed to reproducibly induce sustained ventricular tachyarrhythmias. Of 44 patients with no ventricular tachyarrhythmias induced before isoproterenol infusion, 11 had a sustained ventricular tachyarrhythmia and 1 patient had unsustained VT induced by isoproterenol alone or by programmed stimulation during the infusion. In 9 of 16 patients in whom nonreproducible or unsustained ventricular tachyarrhythmias were induced before isoproterenol infusion, more reproducible or more sustained ventricular tachyarrhythmias were induced during the infusion. Tachyarrhythmia induction was facilitated by isoproterenol in 20 of 40 patients with sustained VT clinically, but in only 1 of 20 patients with unsustained VT or VF clinically. Among patients with sustained VT clinically, those with exercise-provoked VT and those who had not been tested with stimulation at a second right ventricular site or in the left ventricle were more likely to have induction facilitated by isoproterenol. Drugs effective against induction of isoproterenol-facilitated ventricular tachyarrhythmias were identified in 13 of 25 trials. These drugs were effective during a mean follow-up of 17 months in 7 of 9 long-term trials.

Anti-Arrhythmia Agents↗
PubMed1984

Clinical efficacy and electrophysiology of imipramine for ventricular tachycardia.

Invasive electrophysiologic studies were performed before and during treatment with imipramine in 18 patients with inducible ventricular tachycardia (VT). All received imipramine, 50 mg twice daily for 3 days, and then 100 mg twice daily for 3 days. Imipramine increased the infranodal conduction times (HV) (from 58 +/- 7.8 to 65 +/- 10 ms) and QRS duration (from 133 +/- 21 to 153 +/- 39 ms) and significantly decreased sinus cycle length (from 875 +/- 145 to 711 +/- 116 ms) and maximal corrected sinus nodal recovery time (from 457 +/- 656 to 380 +/- 603 ms). The Wenckebach cycle length tended to decrease and the QT interval to increase, but these changes were not statistically significant. Atrial and ventricular refractory periods, atrioventricular nodal conduction times and induced VT cycle length did not change significantly. Imipramine prevented induction of VT in 2 patients, and VT was more difficult to induce in 1 patient. These 3 patients received chronic imipramine therapy. The 2 patients in whom no VT could be induced while taking imipramine have had no recurrence of arrhythmia at 6 and 12 months of follow-up. The third patient died suddenly 4 months after discharge from the hospital. One patient had worsening of arrhythmias while taking imipramine and 61% had minor adverse effects. The mean combined plasma imipramine and desmethylimipramine concentration at the time of the repeat electrophysiologic study was 227 +/- 114 ng/ml. Imipramine is effective against VT in some patients; however, like other type I antiarrhythmic drugs, the rate of efficacy is low.

Adult↗
PubMed1984

The dexamethasone suppression test during bereavement.

The dexamethasone suppression test (DST) was given to 13 elderly grieving subjects having a major depressive disorder. Forty-six per cent had some predisposition for depression. All had a post-DST, 4:00 p.m. serum cortisol below 5 micrograms/dl, but these cortisols correlated with Hamilton Depression scores (r = .59, p less than .05).

Depressive Disorder↗
PubMed1984

Quinidine.

Explore the source record for details and available documents.

Animals↗
PubMed1984

Recordings of basal ventricular preexcitation from electrode catheters in patients with accessory atrioventricular connections.

To determine the effects of ventricular preexcitation via accessory atrioventricular connections (ACs) on the sequence of basal ventricular activation, electrophysiologic study records of 22 patients with AC were reviewed. In each, AC site was confirmed by mapping done at operation. Local ventricular preexcitation (VP), defined as earlier timing of a local ventricular electrogram relative to the surface electrocardiographic QRS onset in preexcited compared with in normal QRS complexes, was assessed at the coronary sinus and at the ventricular septal summit recorded from the His bundle site. Five patients with concealed AC did not have VP. VP patterns with manifest AC were similar during average fusion QRS complexes and maximum ventricular preexcitation. Left free wall and left crux AC produced VP apparent on the ventricular electrogram recorded at the coronary sinus alone. With anteroseptal AC, VP was noted only at the ventricular septal summit. Posteroseptal AC produced VP that was apparent on the ventricular electrogram recorded at the coronary sinus and on the electrogram of the ventricular septal summit. Right free wall AC preexcited neither of these basal ventricular regions. The observation of VP patterns may help in localizing AC and may be particularly useful in patients without retrograde AC function at electrophysiologic study.

Adolescent↗
PubMed1984

Block of inactivated sodium channels and of depolarization-induced automaticity in guinea pig papillary muscle by amiodarone.

The electrophysiological effects of amiodarone were studied in guinea pig papillary muscle by means of the single sucrose gap voltage clamp technique. The first time derivative of the upstroke of the action potential was measured as an indicator of the sodium current. The preparations were not voltage clamped during the action potential upstroke. Acute effects of amiodarone (4.4 X 10(-5) M and 8.8 X 10(-5) M; six experiments each) and effects of chronic administration at a single dose level (nine experimental vs. eight control animals) were studied. Results were qualitatively the same for all experimental conditions, and concentration dependent in the acute studies. Amiodarone caused marked use-dependent depression of the first time derivative of the upstroke of the action potential during stimulus trains. For example, at normal resting potential, chronic amiodarone treatment reduced the first time derivative of the upstroke of the action potential of the 16th beat of trains of cycle length 300 msec to 70 +/- 15% (mean +/- SD) of the initial value. This blocking effect was accentuated at more depolarized holding potentials and reduced at hyperpolarized holding potentials. Reduction of the first time derivative of the upstroke of the action potential was found to depend upon sodium channel inactivation. For all experiments, the mean normalized first time derivative of the upstroke of the action potential following a 1-second clamp in the -20 to +20 mV range was 0.92 +/- 0.08 in the control condition and 0.66 +/- 0.20 in the presence of amiodarone (less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1984

Heart transplant rejection monitored by signal-averaged electrocardiography in patients receiving cyclosporine.

Data from standard and high-frequency signal-averaged electrocardiograms (ECGs) were correlated with the results of 67 endomyocardial biopsies performed in 20 cyclosporine-treated heart transplant recipients. Eight patients (group 1) were in the early postoperative hospitalization period and 12 patients (group 2) were studied after their hospital discharge. The biopsy samples were classified as normal or as indicating early (cellular infiltrate) or definite rejection (myocyte necrosis). The standard ECG parameter studied was the summated QRS voltage in leads I, II, III, V1, and V6. The signal-averaged ECG was evaluated for QRS duration, high-frequency voltage amplitude of the total QRS complex and of its three thirds, peak QRS voltage amplitude, and QRS integrated voltage-time product. The ECG recording obtained at the time of a first normal biopsy sample was considered the normal reference to which additional tracings from the same patient were compared. At the time of subsequent biopsies, the standard ECG parameter showed poor reproducibility (r = .58) and it was inadequate in defining rejection episodes in the early or late postoperative period. The signal-averaged ECG was more reproducible (r = .83) and more accurate in detecting definite rejection during the late posttransplant period than the standard ECG. In group 2 patients, 92% of abnormal signal-averaged ECG recordings were associated with rejection episodes and only 13% of normal tracings were associated with definite rejection. The method was inadequate, however, in monitoring patients during the early postoperative period and in detecting mild forms of rejection in the late postoperative phase.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1983

Clinical efficacy and electrophysiology of oral propafenone for ventricular tachycardia.

Sixteen patients with ventricular tachycardia (VT) or nonfatal cardiac arrest were treated with propafenone (P), 900 mg/day. Electrophysiologic studies were performed before and during therapy with P. All patients had inducible sustained VT at the baseline study. During P therapy, VT was not inducible in 1 patient, was unsustained in 1 and was harder to induce in 2 patients. P increased the cycle length of VT from 307 +/- 67 to 382 +/- 107 ms. Five patients began outpatient therapy with P, including 2 in whom VT was slowed to less than 125 beats/min. Two are arrhythmia-free during follow-up of 2 and 8 months. P significantly increased intraatrial conduction time (from 44 +/- 12 to 72 +/- 22 ms), AH interval (from 115 +/- 36 to 152 +/- 45 ms), HV interval (from 55 +/- 18 to 92 +/- 42 ms), QRS duration (from 140 +/- 36 to 180 +/- 48 ms) and QT interval (from 402 +/- 30 to 459 +/- 60 ms). P increased atrial (from 247 +/- 36 to 288 +/- 38 ms) and ventricular (from 249 +/- 20 to 277 +/- 32 ms) effective refractory periods, Sinus cycle length did not change, but the corrected sinus node recovery time increased (from 162 +/- 85 to 821 +/- 1,607 ms). P aggravated arrhythmias in 4 patients. The plasma P concentration, measured either at the time of electrophysiologic studies of when therapy was discontinued, was 753 +/- 428 ng/ml. P suppressed ventricular ectopic beats in 33% and increased them in 1 patient. P has antiarrhythmic activity against VT similar to that of other antiarrhythmic drugs and has potential for serious adverse effects in some patients.

Administration, Oral↗
PubMed1983

Nature of inducible ventricular tachyarrhythmias in a canine chronic myocardial infarction model.

A canine model suitable for serial conscious studies was developed to evaluate the nature of sustained ventricular tachyarrhythmias in chronic experimental myocardial infarction. Thirteen dogs underwent left anterior descending coronary artery ligation followed by complete reperfusion; 11 sham-operated dogs served as controls. In this model, ventricular tachyarrhythmias are inducible in most dogs with experimental infarction and in several dogs without this condition. The morphologic features, rate and drug response of the induced arrhythmias are unlike those of human ventricular tachycardia. Tachyarrhythmia induction is facilitated by anesthesia and thoracotomy. This canine infarct model does not adequately imitate human recurrent ventricular tachycardia, but may simulate human sudden cardiac death.

Animals↗
PubMed1983

Determinants of survival in patients with ventricular tachyarrhythmias.

We analyzed data from 239 patients with sustained ventricular tachycardia or ventricular fibrillation to determine prognosis, predictors of survival, and the prognostic value of inducing arrhythmia and assessing therapy at the time of electrophysiologic study. Therapy predicted to be effective on the basis of electrophysiologic study was administered over a sustained period. There were 71 cardiac deaths, including 44 sudden deaths, during a mean (+/- S.D.) follow-up period of 14.8 +/- 13.9 months (range, one day to 67 months). At one, two, and three years, the actuarial incidence of sudden death was 17 +/- 3, 25 +/- 4, and 34 +/- 6 per cent, and that of cardiac death was 28 +/- 3, 37 +/- 4, and 50 +/- 6 per cent. Multivariate regression analyses demonstrated that the two strongest predictors of both sudden death and cardiac death were a higher New York Heart Association functional class (P less than 0.0001 for sudden death and P less than 0.0001 for cardiac death) and the failure of any therapy to be identified as potentially effective on the basis of electrophysiologic study (P = 0.0019 and P = 0.0003). The majority of deaths in patients with ventricular tachyarrhythmias were sudden, but the severity of heart failure was the strongest independent predictor of mortality. Response to therapy during electrophysiologic study was also an independent predictor of survival.

Adult↗
PubMed1983

Vulnerability of patients with obstructive hypertrophic cardiomyopathy to ventricular arrhythmia induction in the operating room. Analysis of 17 patients.

To evaluate vulnerability to ventricular arrhythmia induction, programmed electrical stimulation was performed in the operating room in 17 consecutive patients undergoing myotomy-myectomy for obstructive hypertrophic cardiomyopathy (HC). A control group of 5 patients undergoing coronary artery bypass grafting with normal left ventricular function and no previous myocardial infarction also was tested. Of the 17 patients with HC, 14 had inducible sustained ventricular tachycardia (VT) or ventricular fibrillation (VF), 1 had inducible unsustained VT and the remaining 2 had less than 6 ventricular beats. In contrast, none of the 5 control patients had an inducible sustained ventricular arrhythmia, 1 had inducible unsustained VT, and the remaining 4 had less than 3 ventricular beats. The difference between the 2 groups with respect to induction of a sustained ventricular arrhythmia, unsustained VT or less than 6 ventricular beats was significant (p less than 0.001). It is concluded that patients with severe obstructive HC are unusually vulnerable to ventricular arrhythmia induction. This suggests that spontaneous ventricular tachyarrhythmias may be an important cause of sudden death in patients with HC.

Adolescent↗