SUMMARYWe sought to quantitate infarct size using radioactive imaging techniques. Infarcts were created in closed chest dogs. Using a scintillation camera interfaced to a computer, infarct images were made in the anterior, left lateral, LAO, and RAO projections, 48 Fourteen mongrel dogs weighing 14 to 31 kg were anesthetized with intravenous sodium pentobarbital (5 mg/kg). Via a carotid approach, utilizing a modified coaxial catheter and a closed chest technique,"' we selectively embolized small occluded catheter segments to branches of the left coronary artery, creating discrete areas of myocardial infarction. The dogs were given an antiarrhythmic drug (lidocaine, 50 mg, intravenously preinfarction; 1 hour postinfarction, and as needed) and antibiotic (cephazolin, 500 mg, intravenously) prophylaxis at the time of the procedure, and allowed to recover. Standard 12 lead electrocardiograms were taken preinfarction and one and 48 hours postinfarction. Forty-eight hours following infarction the dogs were again anesthetized and injected intravenously with 15 mCi of Tc-PYP formulated in our laboratory.'4 Seventy-five to ninety minutes later, infarct images were obtained in ten animals in the anterior, lateral, LAO and RAO projections. Two normal dogs were also imaged with Tc-PYP.The dogs were sacrificed two hours following Tc-PYP injection, at which time the hearts were removed and the ventricles isolated. The right ventricle was separated from the interventricular septum anteriorly. The septum was freed from the posterior ventricular wall and the specimen laid open. A necropsy image was taken. In each experiment, using a cork bore biopsy tool, a total of 74 cylindrical, transmural specimens were taken from grossly normal, grossly infarcted, and marginal zones of both ventricles. These biopsy specimens were counted in a well counter, quick frozen in dry ice and alcohol, and then stored at
SUMMARY Despite a fundamental difference in their underlying mechanisms, both postextrasystolic potentiation (PESP) and administration of nitroglycerin (TNG) have been utilized to predict reversibility of abnormal segmental wall motion in patients with ischemic heart disease. To determine whether these interventions induce the same changes in segmental contraction pattern, we analyzed biplane ventriculograms of 14 patients who had an adequately visualized PESP beat on a basal ventriculogram as well as a post-TNG ventriculogram. Four segments in each plane were defined and the area ejection fraction of each segment was calculated for a basal sinus, PESP, and post-TNG beat. To correct for global differences in the response to PESP and TNG, we normalized each segmental ejection fraction (NSEF) by the ventricular ejection fraction for that beat and IN PATIENTS WITH ISCHEMIC HEART DISEASE, localized segments of the ventricle which display decreased systolic wall motion may be composed of compromised but viable muscle fibers rather than scar tissue.",2 With the development of coronary artery bypass surgery, the concept of restoring contractile function by improving blood supply to an ischemic area has received increased consideration and has been supported by documentation of improvement in left ventricular function in some patients after such surgery.2 To preoperatively identify ischemic regions of the ventricle with the potential to improve their contractile function after adequate revascularization, several groups of investigators have evaluated the response of abnormally contracting segments to postextrasystolic potentiation (PESP), which enhances myocardial contractility, or to administration of nitroglycerin (TNG), which usually decreases the workload of the heart. Both of these interventions have been reported to improve the systolic motion of some hypokinetic and akinetic segments,'-"' and limited postoperative studies appear to confirm the predictive value of these induced changes.88.10 The use of PESP requires a ventriculogram with an early extrasystole followed by an adequately visualized sinus beat, whereas the administration of TNG requires the performance of a second ventriculogram. In an individual patient, the choice of which intervention to use may be limited. Therefore, we performed this study to ascertain whether the comparative effects of PESP and TNG are the same for all segments of a given ventricle regardless of the basal function of any segment and despite the difference in the underlying mechanisms of the two interventions. MethodsIn patients with chest pain suggestive of angina, we performed retrograde left heart catheterization with the patient in the postabsorptive state and following premedication with diazepam, 10 mg i.m. A #7F NIH catheter was passed from the right brachial artery or a #8F pigtail catheter was passed from the right femoral artery. Left ventricular pressures were monitored using a Statham P23Db
Due to our need, we sought a simple method to reliably create myocardial infarction in the closed-chest dog. Previous techniques were dangerous, time consuming, unreliable, and costly. Here we described a new coaxial catheter method by which occluded catheter plugs are embolized selectively to branches of the left coronary artery in closed chest dogs anesthetized with sodium pentobarbital (10 mg/lb). Infarcts varying in size from 3 to 27 g, 2-27% of the left ventricle, were reliably created in dogs weighing 26-70 lb. Complications were rare with only a single fatality in the last 15 procedures. The method proved safe, simple, quick, versatile, reproducible, and inexpensive.
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