Prognosis in occult thymomas in myasthenia gravis following transcervical thymectomy.

Thymomas were noted in 239 (11%) of 2097 myasthenic patients followed up at our institution. Among 996 patients who had undergone thymectomy, 191 patients (19%) had thymomas compared with 48 (4%) of 1101 patients treated without surgery. A definitive diagnosis of thymoma was not made until after thymectomy in 61 patients (35%); in patients not treated with thymectomy, 23% of associated tumors were diagnosed at autopsy. Patients with occult thymomas treated with the transcervical approach had a clinical course superior to those with tumors diagnosed prior to surgery and treated with the transsternal approach. Most of the advantage could be attributed to the association of occult thymomas with small tumor size and to the association of the latter with absence of invasiveness. Small tumor size was significantly associated with higher remission and lower mortality as shown in a proportional hazards analysis. Occult thymomas were accessible through the transcervical approach, with some operations necessitating a complementary mediastinotomy. Thymectomy, through the transcervical approach if technically feasible, is of benefit to all patients, has minimal morbidity, and should be performed early in the course of the disease as a diagnostic and therapeutic intervention since the risk of occult thymomas in patients with myasthenia gravis is high.

Clinical experience in more than 2000 patients with myasthenia gravis.

The vast strides in terms of pathophysiologic understanding which have been made in the past 25 years of research in myasthenia gravis are remarkable. This period of time has also seen the evolution of many applicable technological advances to better our care of these patients. Myasthenia's place in the autoimmune family of diseases has been demonstrated. No clear-cut strategy resulting from these discoveries has, however, been more than one of temporary relief or clinical improvement. In our center over these years the performance of early thymectomy in all cases of generalized myasthenia seems to be the one demonstrably reliable technique available. The effect of this procedure on coexisting neoplasia and other autoimmune disease suggests continuing avenues of investigation.

Evidence favoring the use of anticoagulants in the hospital phase of acute myocardial infarction.

Since the last comprehensive review of anticoagulation in acute myocardial infarction four additional randomized control trials have been reported. The overwhelming majority of all trials favored anticoagulation. Rates of thromboembolism were higher in the control, and hemorrhagic complications in the anticoagulated group. Pooling of all randomized control trials gives mean case fatality rates of 19.6% for the control and 15.4% for the anticoagulated group, a relative reduction of 21% (P less than 0.05 or less than 0.001, depending on the analytic method). Five of six randomized control trials reported "no effect" because the difference favoring anticoagulation was not statistically significant. However, sample sizes in these "negative" papers were too small to protect against missing a 21% reduction in true case fatality rate due to anticoagulation (beta greater than 0.10). All patients who present no specific contraindication should receive anticoagulants during hospitalization for infarction.

Ventricular electrical instability in the conscious dog: effects of psychologic stress and beta adrenergic blockade.

The effect of psychologic stress on cardiac vulnerability was examined in 10 conscious dogs. The repetitive extrasystole threshold was employed as a measure of susceptibility to ventricular fibrillation. Instrumental aversive conditioning constituted a stressful environment. The repetitive extrasystole threshold decreased by nearly 50 percent during 3 days in which the animals were exposed to the stressful environment. When Tolamolol hydrochloride, a cardioselective beta adrenoceptor blocking agent, was administered before a stress session, the repetitive extrasystole threshold was unaltered from the control value. Thus, stress-evoked changes in cardiac vulnerability are mediated through the sympathetic nervous system.

Repetitive extrasystole as an index of vulnerability to ventricular fibrillation.

The assessment of ventricular vulnerability by inducing ventricular fibrillation (VF) presents limitations when neural activity is being investigated, especially in the unanesthetized animal. As repetitive extrasystoles (RE) have been observed to precede the occurrence of VF, it was relevant to determine whether the RE threshold provides a reliable index of cardiac susceptivility to fibrillation. The RE and VF threshold relationships were studied in 32 chloralose-anesthetized dogs during left stellate ganglion stimulation, vagus nerve stimulation, and beta-adrenergic blockage with practolol. The vulnerable period was scanned at 1-ms intervals and at 2-mA increments with a single, 2-ms, constant-current cathodal stimulus; RE and multiple RE were induced reproducibly when 66% and 82%, respectively, of the fibrillatory current was administered. The nadirs for RE and multiple RE were coincident in the cardiac cycle with the vulnerable-period threshold for VF. Stellate and vagal stimulation and beta-adrenergic blockade resulted in comparable changes in RE and VF thresholds and produced equivalent shifts in the cardiac cycle of the RE and VF vulnerable-period nadirs. These observations suggest that RE and VF phenomena share a common electrophysiologic basis and that the RE threshold can be used as an end point for measuring ventricular vulnerability to VF.

Programmed "trendscription." A new approach to electrocardiographic monitoring.

A new approach to monitoring of episodic but frequently recurring arrhythmias has been developed, consisting of condensation of electrocardiographic information on a special drum recorder, a programmer that permits selection of intervals and durations for monitoring, and a telemetry unit for transmission of the electrocardiographic signal. We used this system to manage three selected cases.