Henry T. Davis

Cardiac Death in the First 6 Months After Myocardial Infarction: Potential for Mortality Reduction In the Early Posthospital Period

In a prospective postmyocardial infarction study of 759 patients aged less than 66 years, 42 posthospital cardiac deaths (42 of 759; 6 percent) occurred during a 6 month follow-up period. The average age of those who died was 53.5 +/- 8.8 (+/- standard error) years, and postmortem examination was obtainedon 36 percent. Almost 60 percent of the 6 month posthospital mortality occurred within 2 months after hospital discharge. Fifty-five percent of the cardiac deaths occurred either outside th ehospital or within hospital emergency departments, and 62 percent of the deaths were sudden (within 12 hours) or unwitnessed. The suspected mechanism of cardiac death was a primary arrhythmia in 62 percent, and a definite or probable myocardial infarction was diagnosed in only 41 percent. Use of digitalis and diuretic and antiarrhythmic agents was significantly (P is less than 0.025) greater in this group during the week before death than in a comparison survivor group; no difference in use of propranolol or tranquilizers was noted between the two groups. Fifty percent of the group that died had two or more of the following factors: death outside the hospital, sudden death, primary arrhythmic death. These findings indicate that a considerable potential exists for reducing cardiac death in the early posthospital phase of myocardial infarction.

Somatosensory thresholds in monkeys exposed to acrylamide

Six monkeys were trained to report detection of a vibratory or electrical stimulus applied to the fingertip. The vibratory stimuli were presented at two frequencies (40 and 150 Hz). Thresholds were determined with a tracking procedure before, during, and after dosing. Each monkey served as its own control. Four monkeys were dosed orally with 10 mg/kg of acrylamide 5 days a week until the appearance of toxic signs. The total administered dose varied between 320 and 450 mg/kg. The other two monkeys served as time-matched controls. All the monkeys were observed 5 days a week. They were also weighed and presented with a visuomotor task (pickup test) twice a week. Weight loss usually preceded the onset of gross behavioral disturbances, such as loss of balance, tremor, or decreased activity. Impaired coordination, as revealed with the pickup test, paralleled weight loss. Electrical sensitivity was not affected. Vibration sensitivity, however, fell during dosing and remained impaired for several months after dosing ceased, outlasting all the other effects. Recovery of the other indices occurred relatively soon after dosing ended. These data indicate that vibration sensitivity testing can trace the time course of intoxication and recovery in toxic peripheral neuropathies. Furthermore, the differential results obtained with vibratory and electrical stimulation are consonant with a primary effect on end-organ receptors.

A Test for the Effects of Low-Temporal-Average-Intensity Pulsed Ultrasound on the Rat Fetus

In 1978, Pizzarello and co-workers reported that exposure of rat fetuses to diagnostic levels of ultrasound caused marked reduction in fetal weight. Replicates of these experiments have been conducted and, in addition, exposures at 10 times the peak and average intensity were used. No effect on fetal weight, numbers of living fetuses or resorptions could be attributed to ultrasound at either exposure level.

Test for the effects of diagnostic levels of ultrasound on the immune response of mice

Abstract An attempt has been made to replicate an experiment which reported suppression of the immune response of mice after exposure of the spleen to a pulsed diagnostic ultrasound unit with a temporal average acoustic power of 8 mW. Our tests of both hemagglutinin and hemolysin responses of mice exposed at 8 and 80 mW temporal average powers were not significantly different from controls.

Statistical analysis of root growth rate determinations

Abstract Experiments in which a number of factors may influence a response require careful analysis. Typically, such factors include a treatment condition, whose effects are of primary interest, and a number of secondary variables, whose influence cannot be controlled in the design of the experiment. The analysis of variance can be used to analyze such complex experiments. Data on the growth rates of pea roots exposed to 60 Hz electric fields are used to illustrate this statistical technique. Also included is a series of related plots, which clearly reveal the structure in the data.

THE CHRONOLOGY AND SUDDENNESS OF CARDIAC DEATH AFTER MYOCARDIAL INFARCTION

A prospective postinfarction study of 978 patients less tha 66 years of age followed from 1 to 5 years was utilized to evaluate the chronology (interval from hospital discharge to demise) and suddenness (elapsed time from the onset of terminal symptoms to demise) of cardiac death. Clinical information including the patients history and CCU, 6-hour Holter electrocardiographic, medication, and mortality event data was available on 112 cardiac deaths, with 56% of those with witness deaths dying suddenly (less than or equal to 1 hour). During the first postinfarction year 50% of the nonsudden deaths occurred within the first month after hospital discharge, whereas 84% of the sudden deaths occurred in the 2 to 12 month period after infarction (Chi Square = 6.25, p less than 0.02). There were no clinical variables including Holter-recorded ventricular premature beats that distinguished between early and late or sudden and nonsudden cardiac death. These findings indicate that the chronology and suddenness of the terminal cardiac event are more difficult to predict than had previously been appreciated. The therapeutic implications of these observations are discussed.

Ultrasonic treatment of tumors--II. Moderate hyperthermia.

Abstract Ultrasonically induced hyperthermia (44–45°C for 10 min) and surgical excision were used in the treatment of hamster fibrosarcomas. Both pulsed and continuous wave 3 MHz radiation was used. Rates of metastasis and effectiveness in eliminating the primary tumor were approximately equal with the two methods of treatment.

Ultrasonic treatment of tumors-III high intensity, low frequency exposures

Abstract Hamster fibrosarcomas were exposed to 1.06 MHz ultrasound at intensities of 90 W/cm 2 in a pulse mode (0.1 sec on, 0.9 sec off) to avoid excessive heating. Tumor temperatures ranged from 19 to 30°C during these exposures. The treatment had no apparent effect on the rate of growth of the primary tumor or on the rate of metastasis.