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Biomedical subjects

B R MacKenzie

Publications and source records attributed to B R MacKenzie.

10 recordsLinked to original sources
PubMed1997

Decreasing mortality from acute myocardial infarctions: effect of attack rates and case severity.

Mortality from myocardial infarction (MI) has declined in many countries and the reasons for the decline have not been fully quantified. We used the database of the Halifax County MONICA Project to test the hypothesis that the decline of in-hospital mortality from MI can be explained by a trend toward less severe disease as opposed to improved treatment. During the study period 1984-1993, 14,130 people aged 25-74 had been admitted to hospital with suspected MI. Of these, 3774 were diagnosed as definite MI by standardized criteria (480 fatal). For each patient, clinical history, serial cardiac enzymes, and ECG treatment regimen during hospital stay were extracted from patient charts. Survival status 28 days after onset of symptoms was determined. A severity index predicting 28-day case fatality was derived from health status at admission time. During the study period the rate of definite MI in the MONICA target population showed a general downward trend from 221 to 179 per 100,000/year (p = 0.0002). The severity index increased during the observation time (p < 0.0001), predicting 25% higher mortality. Case fatality fluctuated, but showed a marginally significant decline. We conclude that part of the decreased in-hospital mortality from MI is due to lower attack rates. The remainder occurred despite increased case severity and is possibly due to improved in-hospital treatment.

Adult↗
PubMed1994

Gender differences in the presentation, treatment, and short-term mortality of acute chest pain.

The Halifax County MONICA database was used to estimate the gender bias in presentation, prehospital and in-hospital treatment, and 28-d mortality of patients suffering an episode of acute chest pain. The study population consisted of all county residents aged 25-74, admitted between 1984 and 1990 to a CCU, or suffering a myocardial infarction anywhere in a hospital. The mean age for men was 58.5 (n = 6561), for women 61.5 (n = 3176). Women of all age groups were more likely to have a history of diabetes or hypertension, and below age 55 had a higher prevalence of peripheral vascular disease. Typical symptoms for infarction were present in 30.8% of women and 38.1% of men (p < 0.0001). More women were taking beta-blockers, Ca-antagonists, digitalis, diuretics, and nitrates (p < 0.001), and more men were on antiarrhythmics. A gender difference was observed for coronary arteriography (24% in men, 18% in women) and for the exercise stress test (23% in men, 18% in women). In hospital, men had more episodes of severe arrhythmias (OR = 1.52). Except for aspirin and antiarrhythmics, the difference in hospital medication and 28-d mortality (9.6% in women vs. 7.8% in men) could be explained by the existing clinical conditions.

Adult↗
PubMed1988

Acute non-Q-wave myocardial infarction: a distinct clinical entity of increasing importance.

Despite the increasing incidence of acute non-Q-wave myocardial infarction, controversy remains regarding its validity as a distinct pathophysiologic physiologic and clinical entity. Review of the data indicates that the controversy is more apparent than real. The pathophysiologic factor discriminating best between non-Q-wave and Q-wave infarction is the incidence rate of total occlusion of the infarct-related artery, approximately 30% in non-Q-wave infarction and 80% in Q-wave infarction. Patients with non-Q-wave infarction have a higher incidence of pre-existing angina than patients with Q-wave infarction; they also have lower peak creatine kinase levels, higher ejection fractions and lower wall-motion abnormality scores, which suggests a smaller area of acute infarction damage. However, patients with non-Q-wave infarction have a significantly shorter time to peak creatine kinase level and more heterogeneous ventriculographic and electrocardiographic infarct patterns. The in-hospital death rate is lower in non-Q-wave than in Q-wave infarction (approximately 12% v. 19%). The long-term death rates are similar for the two groups (27% and 23%), but the incidence of subsequent coronary events is higher among patients with non-Q-wave infarction; in particular, reinfarction is an important predictor of risk of death. Most of the differences in biologic and clinical variables between the two types of acute infarction can be related to a lower incidence of total occlusion, earlier reperfusion or better collateral supply in non-Q-wave infarction. Further study is needed to better characterize the long-term risk and to define the most appropriate therapies.

Electrocardiography↗
PubMed1988

The consequences of reviewing serial changes in the Minnesota code for diagnosis of acute myocardial infarction.

We investigated the effect of reviewing serial electrocardiograms (ECGs) for significance of changes in the Minnesota code, and the influence of this effect on the MONICA diagnosis of myocardial infarction (MI). We used the data from 1340 consecutive admissions to the coronary care units of our MONICA centre and we developed ECG classifications and MONICA diagnoses that were based once on the unreviewed Minnesota code and once on the reviewed code. A comparison of the two ECG classifications showed that codes for evolution of Q-waves and injury currents were much more likely to change as a result of a review (46.8%) than codes for evolution of repolarization changes (12.8%). The review of serial Minnesota codes caused a change of the MONICA diagnosis primarily in the category definite MI (10%). In a blinded clinical assessment, the cases that changed diagnosis were judged to be different from those that remained constant. It is concluded that the use of ECG classification based on unreviewed Minnesota code changes introduces heterogeneity. The significance of this effect depends on the use of the results.

Coronary Care Units↗
PubMed1987

Effectiveness of a non-amalgamated ambulance service on out-of-hospital sudden cardiac death.

Many Canadian communities rely on non-amalgamated ambulance services to respond to out-of-hospital sudden cardiac arrest victims. These pre-hospital care systems lack a central coordinating and dispatching facility, a publicized, easily-accessible telephone number (911) and vehicles equipped with monitor-defibrillators, and are generally staffed by personnel trained only in basic cardiac life support. To receive definitive care, the victim of a cardiac arrest in these communities must be successfully transported to a hospital. In the study area, 114 victims of out-of-hospital sudden death were identified in a community served by a non-amalgamated ambulance service over a 12-month period for an annual incidence rate of 6.1/10,000. The mean age was 64 +/- 11.5 years with the majority (78%) of arrests occurring in the home. The collapse to CPR time was 10.2 +/- 6.7 minutes and the ambulance response time was 5.2 +/- 3.9 minutes. The estimated time from collapse to the victims receiving definitive care was 36.4 +/- 19.1 minutes. Overall, only 8 victims (8.8%) survived and were discharged from hospital. Based on the data presented, survival rate for cardiac arrest victims treated by a non-amalgamated ambulance system are inferior to those reported for pre-hospital care services capable of providing advanced cardiac life support at the scene. Whether all of the components of an established paramedic program are required to improve survival rates in individual communities remains undetermined.

Adult↗
PubMed1983

Frequent ventricular ectopic activity without underlying cardiac disease: analysis of 45 subjects.

Forty-five subjects, aged 2 weeks to 62 years, who presented with frequent (greater than 100/day) ventricular ectopic beats (VEBs) and without evidence of underlying cardiac disease were studied. The spectrum of ventricular dysrhythmia was assessed by 24-hour ambulatory electrocardiography and exercise tolerance test. Sinus rhythm was the prevailing rhythm in all subjects. VEB frequency averaged 444 +/- 454 per hour (range 0 to 1,863) over the 24-hour monitoring period and was not significantly different during waking or sleeping periods. There was no simple correlation of VEB frequency with prevailing sinus rate (r = -0.0006; p = not significant [NS]). The prevalence of complex VEBs (multiform, R-on-T and repetitive) was relatively high (18 of 45 patients), and was equally distributed about the median VEB frequency of 314 VEBs/hour (7 of 18 versus 11 of 18; NS). Of the 43 subjects who had exercise tests, 37 had VEBs during the preexercise rest phase, compared with only 11 at peak exercise (p less than 0.0001). To assess the short-term natural history of the VEBs, 27 subjects had repeat clinical examinations and 24-hour electrocardiograms at a mean interval of 8 months. All remained well. Although there was considerable individual temporal variability of VEB frequency in this subgroup, there was no significant change in group mean values (415 +/- 409 VEBs/hour initially versus 401 +/- 383 VEBs/hour at follow-up study; NS). The relative temporal constancy of VEB frequency in the group as a whole was also reflected in a high linear correlation of VEB frequency at initial and follow-up studies (r = 0.816; p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗