Temporal relation of epicardial electrographic, contractile and biochemical changes after acute coronary occlusion and reperfusion.

The increasing use of changes in the S-T segment of local epicardial electrograms to quantitate myocardial infarct size has led to the need for a better understanding of this method. Accordingly, we studied the local electrographic, tension and biochemical changes that occurred after coronary occlusion and subsequent reperfusion in 44 dogs using epicardial electrograms from 10 to 12 sites, Walton-Brodie strain gauge arches and myocardial ratios of potassium ion to sodium ion (K+/Na+). After coronary occlusion for 1 hour, total S-T segment elevation increased from 10.2 +/- 2.4 to 78.3 +/- 13.7 mv (P less than 0.001) and tension development decreased to 63.6 +/- 7.0% of control value (P less than 0.001); occlusion for 3 hours resulted in a total S-T segment elevation increase from 5.8 +/- 3.4 to 56.7 +/- 8.7 mv (P less than 0.001) and a tension decrease to 61.4 +/- 5.3% (P less than 0.001) of control value. After reperfusion two types of response were observed. In nine experiments new local pathologic Q waves appeared in an average of 5.3 of 8.2 ischemic electrode sites within 5 to 10 minutes of reperfusion concomitant with a marked further decrease in total tension from 67.3 +/- 5.5% to 42.4 +/- 6.0% of control value (P less than 0.001). Simultaneously, total S-T elevation decreased from 66.1 +/- 8.2 to 25.3 +/- 3.4 mv (P less than 0.001). In seven experiments no Q waves appeared after reperfusion and there was no significant change in tension. Total S-T elevation again decreased from 58.3 +/- 12.7 to 27.1 +/- 5.7 mv (P less than 0.025). When normal saline solution was perfused distal to the coronary arterial occlusion total S-T elevation decreased from 68.0 +/- 3.6 to 36.3 +/- 5.2 mv (P less than 0.001). After 3 hours of coronary occlusion, myocardial K+ decreased and Na+ increased in the ischemic zone, resulting in a significant decrease in the K+/Na+ ratio (P less than 0.005). Reperfusion for 2 hours resulted in a further depletion of K+ and an increase in Na+ with a resultant complete reversal of the K+/Na+ ratio (P less than 0.001). In summary, after reperfusion the S-T segment abnormalities rapidly decreased in all experiments despite the appearance of new Q waves in more than half of these studies concomitant with either a decrease or no change in contractile ability and continuing myocardial K+ loss and Na+ accumulation. S-T segment mapping therefore appears to be of limited value in assessing the effect of reperfusion on infarct size. The decrease in S-T segments that occurred with perfusion of either blood or saline solution suggests a "washout" phenomenon.     

In vivo coronary angioscopy

The feasibility of in vivo coronary angioscopy was tested utilizing a 1.8 mm angioscope in vessels where blood had been replaced by optically clear liquids, including a new perfluorocarbon emulsion. After trials in postmortem canine and human coronary arteries, in vivo intraluminal visualization was accomplished in the dog with a catheterization technique and in patients during open heart surgery. The results demonstrate the feasibility and potential clinical usefulness of direct visualization of intravascular anatomy and disease, analogous to endoscopy of other organ systems.     

The protean manifestations of Mycoplasma pneumoniae infection in adults.

Mycoplasma pneumoniae is a well recognized respiratory pathogen in children and young adults. In addition, M. pneumoniae infections may also involve other organ systems. Reviewed here are the various clinical syndromes in adults caused by this infectious agent, with emphasis on those which have recently been seen at The New York Hospital. Two previously unreported manifestations of M. pneumoniae infection, cranial nerve mononeuropathy and hepatitis, are described, and the laboratory methods for diagnosis are discussed.     

Human growth hormone release. Comparison of provocative test procedures

Twenty normal adult volunteers were systematically tested with five known provocative agents of human growth hormone (HGH) release in order to ascertain which procedure was the most effective stimulus for pituitary testing purposes. Ninety-five per cent responded normally (5 ng/ml increment) to levodopa (l-dopa) and 90 per cent to insulin-hypoglycemia. Arginine, vasopressin and glucagon were less potent stimuli; however, arginine (80 per cent response rate) was superior to vasopressin and glucagon (60 and 55 per cent, respectively).Nine subjects were retested with the same stimuli. Again, the incidence of normal HGH responses was highest with the l-dopa and insulin tolerance tests (100 and 89 per cent, respectively). Results with arginine, vasopressin and glucagon were significantly less consistent.Because of the important additional features of greater simplicity and safety, and until hypothalamic releasing substances become generally available, the routine use of l-dopa as a pituitary test agent warrants great attention.     

Caval occlusion technique for hepatic venous sampling: a new approach to estimating splanchnic substrate balance in conscious dogs.

We have proposed a new technique for sampling hepatic venous blood in conscious dogs. Sub-hepatic vena caval blood flow was temporarily occluded by a previously implanted inflatable snare so that all blood entering the inferior vena cava was hepatic venous effluent. Hepatic venous blood samples were collected from the inferior vena cava 8 seconds after beginning caval occlusion, with the total interval of flow occlusion lasting 12 to 15 seconds. No behavioral or metabolic alterations were observed when or metabolic alterations were observed when hepatic venous effluent was repetitively sampled using the caval occlusion technique. Net splanchnic glucose balance (NSGB) was measured in conscious dogs receiving saline, glucose or glucagon infusions. NSGB measurements made with the caval occlusion technique were in accord with previous results obtained via tracer methodology or arterio-venous difference techniques utilizing hepatic vein catheterization. The caval occlusion technique thus provides a method for collecting hepatic venous blood samples from conscious animals without the difficulties associated with hepatic vein catheterization.