Experimental and clinical studies have shown the beneficial effects of triiodothyronine (T3) following myocardial revascularization on cardiopulmonary bypass (CPB). In this study, open-label T3 was administered to 68 high-risk patients undergoing open heart surgery. The New Jersey Risk Assessment was used to calculate the preoperative estimated surgical mortality. A loading dose of T3 was administered: (a) at release of the aortic cross-clamp, (b) whenever the patient became CPB dependent, (c) if the patient exhibited low cardiac output after discontinuing CPB and (d) as pretreatment before initiating CPB. All therapeutic modalities were followed by a continuous T3 infusion. Following T3 therapy, CPB was discontinued in all patients. Based upon discriminant analysis, a total of 26 deaths were expected from the entire group, but only 7 patients died, therefore, the observed mortality was reduced by 72% (p < 0.007). The use of T3 had a major impact on reducing surgical mortality, and may be advocated as a new therapeutic modality in patients with high estimated mortality undergoing open heart surgery.

Adult↗

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Choosing a vessel for aortocoronary bypass.

In practice, the surgeon is left with few choices of the proper ACB graft. His options are limited entirely to autologous tissues, of which the best is the great saphenous vein from the calf (Table 3). Actually, once leg veins and the internal mammary artery are no longer available there are few other choices worth considering. Small calibre allografts, however preserved, and synthetic grafts, are uniformly doomed to failure. The great saphenous vein from the calf is usually a single tube, of suitable diameter and strength for arterial replacement. Most of its tributaries lie in the upper third of the calf; this makes the lower segment preferable for the patient who requires only one or two bypasses. Variations in the normal anatomy have been illustrated.

Blood Vessel Prosthesis↗

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Relationship between pacemaker fibrillation thresholds and electrode area.

Energy thresholds for electrical pacing of the heart are lower with small electrodes than with large. Because pacing of the heart during the vulnerable period may produce ventricular fibrillation, it is also pertinent to know if fibrillation threshold is affected by the electrode size. Electrodes of different surface area but of the same material were implanted in 40 dogs and the pacing thresholds were recorded. Ventricular fibrillation was electrically induced by discharging a 2-msec d.c. cathodal pulse of progressively increasing energy into the vulnerable period. It was found that small electrodes required more energy to produce ventricular fibrillation than large electrodes, and the ratio of fibrillation to stimulation threshold was higher for the small-surface-area electrode. The difference between the thresholds and ratios obtained with the various electrodes was statistically significant. A similar experiment was performed in animals with chronically implanted electrodes, producing comparable results. The results indicate that, in regard to pacing and fibrillation thresholds, small electrodes are preferable to large.

Animals↗

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