Early thrombolytic therapy does not enhance the recovery of the right ventricle in patients with acute inferior myocardial infarction and predominant right ventricular involvement

In this study we report the effects of early thrombolytic therapy on the recovery of the right ventricle after an acute myocardial infarction. Sixty-five patients presenting with their first inferior myocardial infarction and predominant right ventricular involvement were consecutively treated as follows: group A (20 patients) conservatively (without thrombolytic therapy), group B (19 patients) with streptokinase and group C (26 patients) with recombinant tissue type plasminogen activator. Coronary angiography was performed within 72 h after admission in 52 patients (10 of group A, 18 of group B and in 24 patients of group C) followed by transluminal coronary angioplasty in 26. All groups had similar characteristics except for a higher mean age in group A. Within 3 months, a remarkable improvement in right ventricular function and a major increase in ejection fraction was observed for all three patient groups. Improvement of right ventricular function was more prominent in patients with residual flow through the infarct-related artery. The beneficial course was comparable in all the groups, unaffected by the type of medical treatment applied, or by the performance of coronary angioplasty. No further significant change occurred beyond this period. Thus, early thrombolytic therapy does not augment the generally favorable course of recovery of the right ventricle from acute infarction.

High frequency electrocardiography of three orthogonal leads in dogs during a coronary artery occlusion

The ability to detect cardiac ischemia in dogs was studied using high frequency electrocardiography and signal averaging technique. Ischemia was induced via a balloon occluding cuff placed around the left anterior descending coronary artery. Three surface orthogonal bipolar leads (X, Y, and Z) were recorded prior to inflation of the occluding cuff. The cuff was then inflated, causing a complete occlusion of the coronary artery. The surface electrocardiogram was recorded before and during ligation and during reperfusion. The recorded waveforms were divided into sequential 10-15 second segments representing different stages of the ischemic state and were aligned using cross-correlation scheme, averaged and band pass filtered between 150-250 Hz. Analysis of the filtered high frequency QRS complexes revealed that coronary ligation was accompanied by changes in waveform morphology including the appearance of zones of reduced amplitude. In seven out of ten experiments reduced amplitude zones were absent before the ligation, present during the occlusion and absent following reperfusion. In two experiments, reduced amplitude zones that were present prior to ligation became wider during occlusion. In one experiment no reduced amplitude zone was present during any stage of the experiment. Such zones may represent slow conduction in regions of the heart rendered ischemia during coronary ligation. Therefore, the morphology of the high frequency QRS complex, as determined by analysis of the signal averaged electrocardiogram, may provide useful information regarding the presence of myocardial ischemia.

Effects of coronary occlusion on high-frequency content of the epicardial electrogram and body surface electrocardiogram

The very high-frequency content (150 to 250 Hz) of epicardial electrogram waveforms was studied in 19 anesthetized dogs subjected to occlusion of left anterior descending coronary artery. Computer techniques of digital averaging and digital band-pass filtering were applied. Signals were obtained from epicardial electrodes placed in the ischemic left ventricular region and on the noninjured right ventricular surface, and from the body surface electrocardiogram. All recordings were made simultaneously before, during, and after coronary occlusion and subjected to the same analysis. The waveforms obtained from the ischemic left ventricular region showed a considerable decrease in high-frequency content, while those obtained from the noninjured right ventricular surface remained unchanged. The results correlated with the appearance of a zone of reduced amplitude in the body surface high-frequency QRS complex. Therefore, this macroscopic phenomenon measured noninvasively from the body surface is explained by local reduction of high-frequency activity in the ischemic region of the myocardium.

Early intervention in acute myocardial infarction: significance for myocardial salvage of immediate intravenous streptokinase therapy followed by coronary angioplasty

Sixteen patients with acute myocardial infarction underwent treatment with streptokinase up to 3 hours after the onset of chest pain. Nine patients (group I) received streptokinase within 1 hour of the onset of pain, and seven patients (group II) received it within 2 to 3 hours. All underwent multigated radionuclide ventriculography after streptokinase therapy and 1 week later. Percutaneous transluminal coronary angioplasty of the infarct artery was performed within 24 hours in all patients. An effort-limited treadmill stress test was performed before discharge. There was no mortality or serious complication. Mean peak total creatine kinase was 521 +/- 289 mU/ml in group I, and 1,614 +/- 709 mU/ml in group II (p less than 0.05). The mean initial left ventricular ejection fraction was 47 +/- 11% in group I and 37 +/- 10% in group II. After early angioplasty (within 24 hours) and at 1 week recovery, left ventricular ejection fraction increased to 53 +/- 9% in group I (p less than 0.05) and to 40 +/- 7% in group II (p = NS). Seven of the nine patients in group I had normal radionuclide ventriculograms at discharge compared with none of the seven patients in group II. Thrombolytic therapy administered less than 1 hour after the onset of symptoms of acute myocardial infarction followed by angioplasty of the infarct artery results in preservation of left ventricular function, whereas therapy given after 2 hours has only a limited effect.

Pharmacokinetic differences between peripheral and central drug administration during cardiopulmonary resuscitation

Advanced resuscitation techniques are dependent on drug therapy to increase survival. Because drugs must reach their site of action instantaneously, the choice of appropriate route of administration may be critical. To study the pharmacokinetics of drug administration by peripheral and central venous routes during resuscitation, nine mongrel dogs were studied. Arterial blood pressure and electrocardiograms were monitored continuously. Cardiac output was evaluated before resuscitation to determine control levels. After thoracotomy and fibrillation of the heart, cardiac massage was started with a frequency of compression maintained at 60/min. Bolus injections of two different radioisotopes were given simultaneously through a peripheral and a central vein. Isotope activity was sampled through a catheter in the right femoral artery at 5 second intervals for 90 seconds and at 30 second intervals for 210 seconds. The major differences between the two routes of administration were that central injection produced a 270% higher peak concentration (p less than 0.001) and significantly shorter lag times to the first appearance of tracer (16 +/- 7 versus 38 +/- 13 seconds, p less than 0.05) and times to peak concentration (13 +/- 5 versus 27 +/- 12 seconds, p less than 0.01). In contrast, there were no significant differences in area under the time-counts curve, mean residence time, total body clearance and steady state volume of distribution. The central compartment volume of distribution was significantly smaller after central than after peripheral injection (26.1 +/- 56 versus 76.3 +/- 16.5 ml, p less than 0.01). The therapeutic implications of these findings must be investigated for individual drugs used during cardiorespiratory resuscitation to determine the most appropriate route and dosage for each agent.