Donald R. Peterson

MYOCARDIAL ISCHEMIA AFTER MAXIMAL EXERCISE IN HEALTHY MEN. A METHOD FOR DETECTING POTENTIAL CORONARY HEART DISEASE

Abstract A study of 433 asymptomatic men emphasizes the value of strenuous exercise testing in the early detection of myocardial ischemia. The sensitivity of the maximal exercise capacity test was nine times greater than that of the double Masters two-step test in eliciting electrocardiographic evidence of myocardial ischemia in 201 “normal” men who were over 34 years of age. Improved detection of potential coronary heart disease by this method is illustrated by comparison with several epidemiologic studies. If the reliability and specificity of this electrocardiographic abnormality in predicting clinical coronary heart disease is confirmed by future follow-up examinations, a method of detection and study of potential coronary heart disease and factors influencing its course will be available.

Seattle Heart Watch: initial clinical, circulatory and electrocardiographic responses to maximal exercise.

Abstract A network of 15 maximal exercise testing facilities in four teaching hospitals, 10 private offices and clinics and an industrial medical department was organized in July 1971 to study prospectively the antecedents of myocardial infarction and sudden cardiac death. Within 18 months 2,332 men were tested: 1,275 healthy “normal” subjects, 97 with prior myocardial infarction, 306 with angina pectoris, 193 with hypertension and 461 with various mutually exclusive combinations of these diagnoses; among these clinical groups were five patients who had had a prior episode of ventricular fibrillation. Historical, physical and laboratory data were recorded on self-teaching printed forms, with normal, borderline and abnormal responses arranged in three columns. Classification with respect to “unlikely,” “questionable” or “likely” risk of future cardiac events was assessed from the highest tally of items in these columns. Analysis showed computer-averaged S-T segment responses were more consistent and reliable predictors than visual interpretations. Cardiac manifestations in healthy men varled with age and risk assessment, and in patients with cardiovascular disease varied with diagnosis and natural history of disease. Many significant differences provided insights into mechanisms of impaired cardiac function in relation to type of clinical disease. Testing was responsible for one postexertional cardiac arrest. Recovery was effected promptly by defibrillation; there was no mortality.

Noninvasive Predictors of Sudden Cardiac Death In Men With Coronary Heart Disease Predictive Value of Maximal Stress Testing

In a follow-up study of 1,852 men with coronary heart disease, 195 deaths occurred within the first 3 years (33 +/- 13 months [mean +/- standard deviation]). Analysis of these cases indicated that the risk of sudden cardiac death in ambulatory men with clinical manifestations of coronary heart disease may be readily estimated from noninvasive clinical and exercise criteria. The important predictors are indexes of the severity of coronary heart disease and impairment of peak left ventricular function demonstrated with symptom-limited maximal exercise. The advantages of these predictors are that they may be elicited on the initial study as well as on follow-up noninvasive examinations of ambulatory patients. The appearance of nonelectrocardiographic predictors in serial examinations may provide an indication for invasive studies and be a more important finding than the ischemic S-T reponse to exertion.

Prospective assessment of recurrence risk in sudden infant death syndrome siblings

Knowledge of the likelihood of a repetition of sudden infant death syndrome within a sibship, particularly in the next sibling, is important to parents. Methodologic considerations with respect to the studies of recurrence risk already published indicate that the rates reported are overestimates. This suspicion is confirmed by our study based on 826,162 infants surviving the first week of life on file in the Medical Birth Registry of Norway. A total of 1062 (1.3 per 1,000) infants died of SIDS; five deaths occurred as the second case in a family. The recurrence risk for the nextborn sibling was 5.6 per 1000, and for all subsequent siblings 4.8 per 1000, which would seem encouragingly low from a counseling point of view.

The sudden infant death syndrome: repetitions in families.

REPORTS on repetition of s~udden infant death syndrome in families have, for th~ most part, been anecdotal? Available information, therefore, is insufficient for either counseling parents or for addressing questions about heritability. In the United States the incidence rate of SIDS ranges between two and three per 1,000 live births per year. The incidence rate of repetitions would necessarily be some fraction of the total. To study events which occur this seldom would require a population based investigation on an immense scale. We elected, therefore, to conduct a study which would permit an estimation of the risk of repetition of SIDS among subsequently born children of families who had experienced at least one episode. To accomplish this objective we sought assistance from officers and staff members of the National Sudden Infant Death Syndrome Foundation and the Guild for Infant Survival, as well as from representatives of Regional SIDS Centers, who informed SIDS parents within their purview about the project and distributed questionnaires to those who wished to participate. Parents sent completed questionnaires directly to the project office at the University of Washington. This data collection scheme, which was dictated by necessity, precluded estimation of a response rate. However, representativeness of the subjects with respect to familial aggregations, with overestimation a major consideration, constitutes a more relevant concern than the sample fraction per se. Despite the obvious limitations of this avenue of investigation, Similar studies have helped to assess familial aggregation in a variety of diseases. We could not conceive of a practical alternative to this approach that would yield a sufficient number of families with systematically collected information concernmg each family member. The nationwide solicitation of SIDS parents for information, initiated in April, 1976, has now produced sufficient data to warrant analysis.

Nationwide Cerebrovascular Disease Morbidity Study

Previous studies have noted that the geographic differences in stroke mortality among areas of the United States were not due to artifacts of certification practices or accuracy of the diagnosis. A study of hospitalized stroke patients was completed in order to determine whether the mortality differences were due to a higher incidence or case fatality following a stroke in areas with high stroke death rates. Eight of the nine areas that participated in the Nationwide Mortality Study were included in this study. A total of 2,619 stroke cases were ascertained including 1,631 (62.3%) who were alive at the time of hospital discharge, 937 (35.8%) dead at discharge, 46 (1.7%) who were discharged alive but died outside of the hospital, and five (0.2%) who were dead at discharge and certified by the medical examiner. The incidence of stroke was higher in the high stroke death rate areas especially for men. The ratio of the incidence of stroke in men as compared to women was higher in the younger age groups (45–54, 55–64) and in the high-incidence as compared to low-incidence areas. The case-fatality percentage was lowest in Denver and highest in South Carolina. Presence of coma on admission was the principal determinant of subsequent mortality in all areas. Finally, there was no consistent difference in the distribution of symptoms of stroke among the areas, and diagnostic procedures were performed more often in urban than rural areas. Approximately 80% of the stroke cases could be substantiated by either an autopsy verifying diagnosis, arteriography, hemorrhagic spinal fluid, hemiplegia or coma on admission. Several hypotheses to explain the differences have been suggested as well as the need for new information.

Infant mortality among subsequent siblings of infants who died of sudden infant death syndrome.

A specially designed method for measuring infant mortality among families with subsequent siblings of sudden infant death syndrome (SIDS) victims in the state of Washington, 1969 to 1984, yielded results similar to those from an earlier study in Norway. In both studies the SIDS rates among siblings were substantially lower than prior estimates. The rate of SIDS in siblings of infants who died of SIDS did not differ significantly from the SIDS rate among control infants matched for maternal age and birth order. Total infant mortality rates in the two groups were virtually identical. From the data at hand, it appears that earlier estimates of the risk of SIDS in siblings were inflated and that parents of SIDS victims can be counseled accordingly.

Sudden infant death syndrome and hypertriiodothyroninemia: comparison of neonatal and postmortem measurements.

Serum triiodothyronine concentrations in victims of sudden infant death syndrome, when compared with those of both living and dead controls, were found to be elevated to a degree comparable to those found in a previous study. Thyroxine, thyroid-stimulating hormone, and thyroglobulin values were not elevated. Neonatal triiodothyronine and thyroxine values, determined on specimens collected within a few days of birth for most of the sudden infant death syndrome victims, did not differ significantly from those of comparable peers in their birth cohort. These results indicate that hypertriiodothyroninemia may serve as a useful postmortem diagnostic marker for the syndrome but not as a premortem predictor. Parenthetically, thyroid hormones appear to remain stable in either a frozen or dried state for up to two years.