Histologic,ultrastructural, and enzymatic measurements of infarct size following coronary artery stenosis and occlusion

Coronary artery narrowing (CAN), which reduced resting coronary blood flow (BF) by 50%, was induced in 10 conscious dogs and was maintained for 4 hours. Five additional dogs (group 1) with complete coronary artery occlusion were compared to the dogs with CAN. serum isoenzymes of creatine phosphokinase (CK) and latate dehydrogenase (LD) were monitored hourly in all groups. After 36 hours, samples were obtained for regional myocardial BF, quantitative histology, and quantitative ultrastructural (EM) morphology. Six dogs with CAN had small infarcts (MI) of less than 1 gm and persistent myocardial cell injury (group 2). The other four dogs with CAN had only persistent myocardial cell injury by ultrastructural criteria (group 3). Peak serum CK activities in groups 2 and 3 were similar, as were MI sizes calculated from serum CK and myocardial depletion. MB CK was of diagnostic value in group 1 but not in groups 2 and 3. The ratio of $\text{LD}\text{1}\text{LD 2}$ had diagnostic value in all three groups. MI size by enzyme estimates was consistently higher than planimetered MI size at autopsy in both groups 1 and 2. All three groups had significant amounts of ultrastructural damage outside of histologically demonstrated MI. These findings suggest that (1) gross and histologic MI size determination of 36 hours after ischemia underestimate extent of damage, and (2) ultrastructural cell changes cause significant release of CK and LD in coronary disease (CAD).     

Myocardial alterations following hypothalamic stimulation in the intact conscious dog

We sought to determine if electrical stimulation of the posterior hypothalamus at physiologic levels could induce myocardial injury in the unanesthetized dog. Biphasic pulses of 1.0 msec. duration, 100 Hz., and 0.2 to 0.8 ma. intensity for 15 sec. via stereotaxically implanted electrodes in six unanesthetized dogs immediately increased heart rate (95 per cent) and mean aortic blood pressure (73 per cent). In two dogs instrumented for aortic and coronary blood flow measurements, stimulation immediately raised cardiac output (21 per cent) and coronary blood flow (185 per cent). All parameters returned to control within 8 to 10 minutes after stimulation. In two dogs killed four hours after stimulation, electron microscopy revealed foci of discrete single-cell degeneration. In two dogs killed 72 and 168 hours after stimulation, light microscopy showed multiple foci of myocytolysis and fibrosis located perivascularly and subendocardially. These lesions resembled catecholamine-induced injury or myocardial lesions secondary to hypoxia. The electron microscopy findings suggest that the lesions are catecholamine-induced. These results suggest that physiologic stimulation of the hypothalamus plays a role in some types of myocardial injury.     

Remission From Suicidal Ideation Among Those in Chronic Pain: What Factors Are Associated With Resilience?

Although there have been many studies on the link between chronic pain and suicidality, surprisingly little research has focused on resilience and recovery among those in chronic and disabling pain who have had suicidal thoughts. The objectives of this study were to identify the prevalence and correlates of recovery from suicidal thoughts among those in chronic pain. A secondary analysis of a nationally representative sample of Canadians in chronic and disabling pain who had ever had serious suicidal thoughts (N = 635) was conducted to identify the prevalence and characteristics of those who are no longer considering suicide. Data were drawn from the Canadian Community Health Survey-Mental Health. Three in five Canadians in chronic pain (63%) who had seriously considered suicide at some point in their life had been free of these thoughts in the past year. Those free of suicidal ideation were significantly more likely to be older, women, white, better educated, with a confidant, and to use spirituality to cope, but less likely to have low household incomes, difficulties meeting basic expenses, and a history of depression and anxiety disorders.PerspectiveAlmost two-thirds of formerly suicidal Canadians with chronic pain were free from suicidal thoughts in the past year. These findings provide a hopeful message of resilience and recovery in the context of disabling pain and help to improve targeted outreach to those most at risk for unremitting suicidality.