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Biomedical subjects

J W Mason

Publications and source records attributed to J W Mason.

At least 145 records · Page 8Linked to original sources
PubMed1982

Surgery for ventricular tachycardia: efficacy of left ventricular aneurysm resection compared with operation guided by electrical activation mapping.

Sixty-five patients underwent surgery for recurrent ventricular tachyarrhythmias. The 32 patients in group 1 underwent simple left ventricular aneurysm resection. The 33 patients in group 2 underwent myocardial resection or incision guided by intraoperative mapping of the electrical activation sequence. The clinical, hemodynamic and angiographic characteristics of the two groups were similar. Although actuarial survival in the two groups was similar through 24 months, late attrition in group 1 patients has left only 21 +/- 13% (+/- SEM) alive by life-table analysis at 94 months. Arrhythmia recurrence has been greater in group 1 than in group 2. In group 1, 50 +/- 9% of patients at risk at 3 months had recurrences by actuarial analysis. In group 2, only 13 +/- 6% at 1 month, 17 +/- 7% at 3 months and 29 +/- 9% at 24 months relapsed. Death was caused by ventricular tachyarrhythmias in 12 of the 17 patients (71%) who died in group 1, but only three of 12 (25%) who died in group 2. We conclude that surgery of the left ventricle, guided and modified by intraoperative mapping of the electrical activation sequence, frequently eliminates ventricular tachyarrhythmias and may be more effective than blind resection of left ventricular aneurysm.

Electrocardiography↗
PubMed1982

Antiarrhythmic drug combinations in the treatment of ventricular tachycardia.

Combinations of antiarrhythmic drugs are frequently used to treat refractory ventricular tachycardia (VT), but few scientific data support this practice. We examined the efficacy and electrophysiology of 110 antiarrhythmic drug combination trials at electrophysiologic study in 74 patients with recurrent ventricular tachycardia. Lidocaine was combined with quinidine in 33 trials, procainamide in 22 and encainide in 20. Propranolol was combined with quinidine in 17 trials, procainamide in 12 and encainide in six. All individual drugs tested (except propranolol, which was usually not tested individually) had failed at electrophysiologic study or clinically in the presence of usually accepted plasma concentrations. Lidocaine in combination with quinidine was effective in 3% of the trials, with procanamide in 5% and with encainide in none of the trials. Propranolol in combination with quinidine was effective in 18% of the trials, with procainamide in 17% and with encainide in none of the trials. The electrophysiologic effects of the tested drug combinations were dominated by the individual effects of the type 1 antiarrhythmic agents. We conclude that the tested antiarrhythmic drug combinations are infrequently effective in preventing VT induction at electrophysiologic study when each agent has failed individually. The addition of lidocaine or propranolol to quinidine, procainamide or encainide does not produce significant synergistic or new effects on the electrophysiologic variables analyzed.

Aged↗
PubMed1982

Endomyocardial biopsy.

Endomyocardial biopsy has been used more frequently over the past 10 years in an increasing number of centers in this country and abroad. When done by an experienced physician, it is as safe as routine cardiac catheterization. Although biopsy is not yet applicable in all cases of myocardial disease, many investigators have found this procedure valuable in specific circumstances, including cardiac allograft rejection, anthracycline-induced cardiomyopathy, and myocarditis. With this technique diagnoses can be made for various disorders including cardiac amyloidosis, sarcoidosis, hemochromatosis, and endomyocardial fibrosis. Although helpful in detecting an unsuspected condition or in formulating prognosis in some patients, biopsy is not diagnostically specific in patients with dilated or hypertrophic cardiomyopathy, because these diseases have no completely pathognomonic features under current examination methods. The proper practice of endomyocardial biopsy requires both technical proficiency and expert pathologic interpretation. As a research tool, biopsy will continue to yield new knowledge about myocardial disease and its treatment.

Biopsy↗
PubMed1981

Malignant ventricular tachyarrhythmias associated with the use of encainide.

In patients treated with the antiarrhythmic drug, encainide, the agent appeared to cause or exacerbate malignant ventricular tachyarrhythmias in 11 cases. The most common type of arrhythmia associated with encainide toxicity was polymorphic ventricular tachycardia (VT) resulting in cardiac arrest. In contrast to drug-induced arrhythmias commonly encountered with quinidine and other type I antiarrhythmic drugs, encainide-induced rhythm was not associated with marked QT prolongation, was not necessarily initiated by R-on-T premature ventricular beats, and usually did not self-terminate. Two patients could not be resuscitated from the rhythm, and several others required prolonged or multiple resuscitations. The risk of encainide-induced ventricular tachyarrhythmias was 11% in 90 patients receiving the drug for recurrent sustained VT and/or fibrillation (VF), 2.2% in 47 patients receiving the drug for chronic complex ventricular ectopic activity. Encainide-induced arrhythmias occurred 29.8 +/- 11.3 hours (range 17 to 48 hours) after starting chronic oral maintenance doses or after dose increases, or 1 to 2 hours after single large doses. Patients experiencing this adverse effect could not be distinguished from those who did not on the basis of encainide dose, degree of QRS widening, or clinical status. We recommend that patients with history of sustained VT or VF have encainide therapy started only in a hospital setting with continuous ECG monitoring and capabilities for cardiopulmonary resuscitation. Dose changes should not be made more frequently than every 48 hours, and patients should not be discharged from the hospital until they have been on stable dose of encainide for a minimum of 48 hours.

Adult↗
PubMed1981

Dose-effect and structure-function relationships in doxorubicin cardiomyopathy.

The cardiomyopathy (CM) produced by the anticancer drug doxorubicin (DXR) (Adriamycin) provides a unique opportunity to analyze dose-effect and structure-function relationships during development of myocardial disease. We measured the degree of morphologic damage by ultrastructural examination of endomyocardial biopsy and the degree of performance abnormally by right heart catheterization in patients receiving DXR. Morphologic damage was variable but was proportional to the total cumulative DXR dose between 100 and 600 mg/m2. Performance abnormalities correlated weakly with dose, exhibited a curvilinear relationship, and had a "threshold" for expression. Catheterization abnormalities correlated well with morphologic damage (r = 0.57 to 0.78) in a subgroup of patients in whom exercise hemodynamics were measured, and this relationship also exhibited a curvilinear, threshold configuration. In DXR-CM myocardial damage is proportional to the degree of cytotoxic insult (DXR dose) while myocardial function is preserved until a critical dose or degree of damage is reached, after which myocardial performance deteriorates rapidly.

Biopsy↗
PubMed1981

Electrophysiologic effects of N-acetylprocainamide in human beings.

The electrophysiologic properties of N-acetylprocainamide (NAPA) were studied in 10 patients undergoing cardiac catheterization. Each patient received two successive intravenous infusions: one loading infusion over 15 minutes and one maintenance infusion at a slower rate for 30 minutes. Eight patients received 10.5 mg/kg body weight and two received larger doses (16 and 21 mg/kg, respectively). NAPA plasma concentration was measured at 5 minute intervals from 0 to 25 minutes, and then at 15 and 30 minutes of the second infusion. Mean blood pressure and electrophysiologic data obtained by programmed stimulation were recorded before drug administration and at 15 and 30 minutes of the infusion when the concentration of NAPA was nearly constant in each patient (range 12 to 35 microgram/ml). NAPA decreased blood pressure (p less than 0.005), increased corrected Q-T interval (p less than 0.01) and increased the atrial and ventricular effective refractory periods from 267 +/- 40 to 307 +/- 41 ms (p less than 0.01) and from 278 +/- 37 to 301 +/- 32.8 ms (p less than 0.05), respectively. NAPA did not significantly change sinus cycle length or sinus nodal recovery time, conduction intervals (A-H, H-V, P-R, QRS), atrioventricular nodal functional refractory period or nodal Wenckebach cycle length. The patient receiving the largest dose experienced mild nausea when the plasma concentration was above 35 microgram/ml. These data show that the electrophysiology of NAPA in human beings is different from that reported for procainamide. At the plasma concentrations studied NAPA increases atrial and ventricular refractory periods without increasing cardiac conduction times

Acecainide↗
PubMed1981

Failure to diagnose cardiac treatment rejection with Tc99m-PYP images.

The possibility of diagnosing transplant rejection using Tc-99m-PYP imaging was examined in 12 cardiac transplant recipients. Two patients were studied on two occasions. The presence or absence of active rejection was established by endomyocardial biopsy. The intensity and pattern of myocardial uptake of the tracer did not differ significantly in the two patients studied at the time of rejection compared to the remainder. It is concluded that a single Tc-99m-PYP study cannot be used to diagnose cardiac transplant rejection.

Adult↗
PubMed1981

The treatment of ventricular tachycardia using an automatic tachycardia terminating pacemaker.

Implanted cardiac pacemakers may be used in the management of selected patients with ventricular tachycardia unresponsive to other forms of medical and surgical therapy. We would like to report the successful treatment of such a patient utilizing a new multiprogrammable automatically activating ventricular burst pacemaker. Thorough electrophysiologic study preceded implantation, and was instrumental in choosing an effective terminating technique, in identifying the need for adjunctive drug therapy, and in testing the safety and efficacy of the implanted system.

Aged↗
PubMed1981

Antiarrhythmic efficacy of encainide in patients with refractory recurrent ventricular tachycardia.

Encainide is a new agent for treating ventricular arrhythmias. We attempted long-term oral therapy with encainide in 38 patients with recurrent, strikingly drug-refractory ventricular tachycardia. The usual daily dose of encainide ws 150-250 mg divided into four or six doses. The mean period until withdrawal of encainide or the date of follow-up was 4.2 months. Encainide completely eliminated recurrence of ventricular tachycardia in 54% of the patients for 6 months of therapy and in 29% of the patients for 18-30 months of therapy. Twelve patients (32%) had side effects possibly due to encainide; in four, the arrhythmia may have been worsened by encainide. During chronic therapy, encainide increased the PR interval by 18% and the QRS duration by 32%. There was no significant change in the corrected QT interval. The presence of QRS prolongation appeared to correlate with antiarrhythmic effect. We conclude that encainide is a safe, well-tolerated antiarrhythmic agent that is often effective against previously drug-refractory ventricular tachycardia.

Actuarial Analysis↗
PubMed1980

Accuracy of the ventricular tachycardia-induction study for predicting long-term efficacy and inefficacy of antiarrhythmic drugs.

We evaluated the prophylactic effect of antiarrhythmic agents against induction of ventricular tachycardia by extrastimulation in 51 patients with recurrent ventricular tachycardia. These patients subsequently underwent 58 long-term trials with tested agents. In 39 trials an agent predicted to be effective by electrophysiologic study was administered, and in 19 a drug predicted to be ineffective was used. There were no clinical differences between the two treatment groups. During a mean follow-up period of 8.2 months, arrhythmias recurred significantly less frequently in the group treated with drugs predicted to be effective than in the other group (P < 0.001); at six months 80 per cent of the patients in the former group were successfully treated, as compared with 33 per cent in the latter group. At 18 months the corresponding figures were 68 per cent and 11 per cent. We conclude that the arrhythmia-induction technique accurately predicts the clinical effectiveness of drugs used in the long-term treatment of recurrent ventricular tachycardia.

Adult↗
PubMed1980

Tocainide for drug-resistant ventricular arrhythmias: efficacy, side effects, and lidocaine responsiveness for predicting tocainide success.

Tocainide therapy has been evaluated in 38 patients with ventricular arrhythmias. Thirty-one had recurrent sustained ventricular tachycardia and/or fibrillation and 29 required prior cardioversions. These arrhythmias could not be managed with quinidine, procainamide, disopyramide, or propranolol. Tocainide doses averaged 1,500 mg/day (range 600 to 2,400) and the majority of patients had plasma concentrations from 6 to 12 micrograms/ml. Twenty-two patients (61%) had their arrhythmias controlled with tocainide and 16 (39%) did not. Tocainide dose and plasma concentrations were similar for responders and nonresponders. Lidocaine was effective in 26 patients and 16 (63%) of these had their arrhythmias controlled with tocainide. Of 12 patients in whom lidocaine was known to be ineffective or who had not been previously treated, only two (17%) had arrhythmias controlled with tocainide (P < 0.02). Side effects occurred in approximately two thirds of patients but required discontinuation of long-term tocainide in only three patients.

Aged↗
PubMed1980

Clinical use of an implantable automatic tachycardia-terminating pacemaker.

A significant fraction of patients with supraventricular and ventricular tachycardia remains a therapeutic problem despite improvements in diagnostic testing, new drugs, and improved techniques for the evaluation of the efficacy of drug therapy. Pacing provides an alternative in selected patients. Pacing techniques may be used for arrhythmia suppression or termination and in rare instances may allow the substitution of a more easily managed arrhythmia. We have permanently implanted a new programmable, automatic tachycardia-terminating pacemaker in patients with drug-refractory supraventricular tachycardia. Following pacemaker implantation, successful tachycardia termination has been documented by ambulatory monitoring. Because of changing requirements for effective termination, we feel programmability is mandatory for successful long-term efficacy. We conclude that pacemaker therapy of supraventricular trachyarrthythmia with the automatic antitachycardia terminating pacemaker is safe, effective, and well tolerated.

Anti-Arrhythmia Agents↗
PubMed1980

Repetitive beating after single ventricular extrastimuli: incidence and prognostic significance in patients with recurrent ventricular tachycardia.

The incidence of repetitive ventricular beating in response to programmed single ventricular extrastimuli delivered during spontaneous rhythm was tabulated in 59 patients with recurrent ventricular tachycardia. Repetitive beating occurred in only nine patients (15 percent). The repetitive response seemed to be a result of bundle branch reentry in four subjects and possibly a result of other mechanisms in five. There was no difference in the incidence of repetitive beating or type of repetitive response in patients with and without ischemic heart disease. During an average patient follow-up period of 13.6 months, there were eight sudden and six nonsudden deaths. Life table analysis revealed a significantly greater incidence of sudden death in patients with ischemic than in patients with nonischemic heart disease. There was no significant difference in the incidence of sudden death in patients with and without repetitive beating. It is concluded that the repetitive response to single ventricular extra-stimulation is infrequent in patients with recurrent ventricular tachycardia, and that repetitive beating is not a prognostic indicator or an indicator of vulnerability to ventricular tachycardia.

Adolescent↗