History of CPR and the role of the national conference.

External defibrillation was first reported in 1956, mouth-to-mouth ventilation was first reported in 1958, and closed-chest compression in 1960. While these developments began the modern era of CPR, accounts of resuscitative efforts go back to ancient times. The guidelines for CPR and emergency cardiac care (ECC) have evolved through five national conferences, held in 1966, 1973, 1979, 1985, and most recently in February 1992. The purpose of these conferences was to review and update published materials in the light of scientific advances and clinical experience. This issue of the Annals of Emergency Medicine contains the proceedings of the most recent National Conference on CPR and ECC. At this conference, a consensus was reached by an international gathering of scientists and clinicians for guidelines on adult basic and advanced life support, as well as on pediatric and neonatal life support.

Noninvasive evaluation of cardiac risk before elective vascular surgery.

The prognostic utility for predicting cardiac events was determined for dipyridamole-thallium scintigraphy, exercise stress testing (when possible; n = 69) and multiple clinical variables in 100 consecutive patients admitted for elective surgical repair of peripheral vascular disease. After initial noninvasive evaluation, 11 patients were referred for coronary angiography and the remaining 89 patients had surgery without further cardiac studies. Fifteen patients (17%) had a postoperative myocardial infarction, one of which was fatal. Of these 15 patients, 14 had thallium redistribution and 3 had positive ST segment depression during stress testing. Among the many variables tested, the presence of redistribution on serial dipyridamole-thallium images was the most significant predictor of serious cardiac events. All 11 patients who had coronary angiography had both redistribution and multivessel coronary artery disease. Four of these 11 patients died during follow-up and 6 had coronary artery bypass surgery. It is concluded that dipyridamole-thallium imaging has significant prognostic utility in predicting postoperative myocardial infarction and death in patients with severe peripheral vascular disease, and is superior to exercise testing or clinical variables in determining cardiac risk. The odds for a serious cardiac event were 23 times greater in a patient with thallium redistribution than in a patient without redistribution, strongly suggesting that myocardial imaging may be used as a primary screening test before elective vascular surgery.

Cardiovascular pharmacology. III: Atropine, calcium, calcium blockers, and beta-blockers.

Atropine, calcium, calcium-channel blockers, beta-adrenergic-receptor blockers, oxygen, morphine, vasodilators, and potent diuretics are frequently used in advanced cardiac life support (ACLS). Since the last AHA conference on ACLS standards, little controversy has arisen regarding the use of oxygen, morphine, vasodilators, or potent diuretics. In 1979, a full vagolytic dose of atropine was recommended for use early in the course of asystolic or bradycardiac arrest. Since then reports suggest that this higher dose of atropine may be of some limited value in treating this highly resistant form of arrest. The routine use of calcium for asystole, bradycardiac arrest, and electromechanical dissociation has come under intense scrutiny. Studies have failed to demonstrate improved survival and have found potentially deleterious levels of serum calcium when calcium was administered according to AHA standards. It is also possible that postanoxic cerebral injury is exacerbated by the use of calcium. No controversy exists, however, concerning the use of calcium for the moribund patient with possible hypocalcemia or with an excess of calcium-channel blockers. The use of calcium-channel blockers has been advocated to prevent or retard the intracellular accumulation of calcium, which may cause irreversible postanoxic tissue damage. Calcium-channel blockers may also be useful in preventing or decreasing cerebral and coronary arteriospasm. These drugs have antianginal properties that may decrease ischemia. The antiarrhythmic effect of verapamil is particularly useful in the treatment of uncomplicated paroxysmal supraventricular tachycardia. Verapamil and diltiazem slow conduction through the atrioventricular node and may be used to slow the ventricular response in atrial fibrillation and flutter.(ABSTRACT TRUNCATED AT 250 WORDS)

External compression without adjuncts.

Over the past decade many exciting and promising new approaches of delivering CPR have been studied. Considerable data have accumulated suggesting that forward flow during CPR is generated, at least in part, by the development of elevated intrathoracic pressure with an extrathoracic arteriovenous pressure difference. This mechanism, known as the "thoracic pump," has been documented during "cough-CPR" and has led to numerous attempts at optimizing the outcome by increasing intrathoracic pressure in CPR. Studies have demonstrated improved flows with simultaneous ventilation and sternal compression, with static or interposed abdominal compression, with longer duration compression, and with various combinations of these maneuvers. Other recent studies have suggested that the cardiac compression mechanism may indeed be operative, at least under certain circumstances, and that CPR may be optimized by increasing the force and rate of compression. Still others have advocated a simple change in the sequence of initiating ventilation and compression. Which, if any, of these newly advocated methods improve the outcome when applied to man remains to be established. If any of these techniques is shown to be more advantageous, its widespead use will depend on its applicability without adjuncts and its teachability to the lay public.

Effects of the cessation of training on left ventricular function in the racing greyhound. Serial studies in a model of cardiac hypertrophy.

Exercise-induced cardiac hypertrophy has been associated with normal resting left ventricular function and, after cessation of training, variable degrees of regression. The racing greyhound is an animal with cardiac hypertrophy said to be part congenital and part exercise-induced. Racing greyhounds underwent serial cardiac catheterization three times during an 8-month period after cessation of racing/training to determine the functional consequences of the cessation of training. At the end of 8 months of inactivity the animals' hearts were excised and weighed in order to compare heart weight/body weight (HW/BW) ratios with those obtained in a group of racing greyhounds killed within one month, 19 +/- 16 days (mean +/- SD), of the cessation of training. Comparison of HW/BW ratios failed to reveal a significant difference between the serially studied group, 12.1 +/- 1.9 g/kg (mean +/- SD), and the more recently exercising group, 12.7 +/- 1.4 g/kg (mean +/- SD) of dogs. After 2 months of inactivity, 9 of 12 greyhounds in the serially studied group showed increases in max dP/dt and dP/dt normalized to a pressure of 50 mmHg. Modified pre-ejection period and peak negative dP/dt also increased significantly (p less than .004) during this same period. No further changes in these variables were found at the final 8-month study. Our failure to demonstrate a difference in HW/BW ratios between these two groups of dogs suggests that the exercise-induced component of cardiac hypertrophy in the trained racing greyhound is probably very small and, if it exists, regresses very early (less than 1 month). Changes in contractility indices that were observed occurred after this time period (between 1 and 2 months) and are therefore probably not due to regression of cardiac hypertrophy.

Chronic tocainide therapy for refractory high-grade ventricular arrhythmias.

Tocainide, an oral analog of lidocaine, was evaluated as a long-term antiarrhythmic agent in 21 patients with symptomatic complex ventricular ectopic activity (10 with hemodynamically significant ventricular tachycardia) refractory to currently available antiarrhythmics singly, and in combination for periods of 3 days to 35 months (mean 13.6 months). Tocainide appeared to be an effective and safe agent for the control of these refractory symptomatic ventricular arrhythmias in 14 of the 21 patients (66%). Minor central nervous system and gastrointestinal side effects were present in most of the patients, usually early on in therapy, and only precluded long-term use in 2 patients. Furthermore, lidocaine responsiveness was a good predictor of tocainide effectiveness in this group of patients. Tocainide precipitated atrioventricular (A-V) block in one patient with pre-existing A-V nodal disease; two patients developed a skin rash while on tocainide therapy. These two patients had previously developed lupus-like syndromes and skin rashes while on procainamide. The ANA titers had been falling in these two patients while on tocainide, and in one of these patients with true systemic lupus erythematosus, rechallenge with tocainide failed to produce skin rash. Tocainide's long plasma half-life and high oral bioavailability permit an 8-h regime. We conclude that tocainide is an effective, safe antiarrhythmic agent with tolerable side effects.

Studies of systolic mechanics and diastolic behavior of the left ventricle in the trained racing greyhound.

Despite much interest in the effects of exercise on the myocardium, and the need to develop animal models which mimic conditions leading to cardiac hypertrophy, little attention has been focused on the trained racing greyhound. The current study compared two groups of anesthetized trained racing greyhounds (a total of 20 animals, 12 of whom were maintained for serial studies and 8 of whom were sacrificed for anatomic correlations) with 3 detrained greyhounds and 6 comparably sized mongrels. Systemic blood pressures, right and left heart pressures, ventricular mechanics and indices of diastolic behavior were compared. All measured indices of contractility (dp/dt, dp/dtDP40, Vce and Vmax) were lower in trained racing greyhounds than in mongrels although none achieved statistical significance. No significant difference in diastolic behavior was found between trained greyhounds and mongrels. While caution should be applied because of the small numbers of animals and the use of anesthesia, the lower than expected contractility found in trained racing greyhounds may reflect increased parasympathetic tone in the immediate post-training period. The normal diastolic behavior of the trained greyhound left ventricle contrasts to abnormal diastolic behavior found in models of chronic pressure overload.

Improved myocardial preservation by improved distribution of cardioplegic solutions.

Two groups of elective coronary artery bypass graft (CABG) patients were compared with respect to a single variable: method of cardioplegia administration. All patients had saphenous vein grafts and all distal anastomoses were done with continuous aortic occlusion and intermittent administration of a 4 degrees C cardioplegic solution. One hundred patients in Group I had the distal anastomoses performed before the proximal anastomoses with cardioplegic solution administered only via the aortic root. One hundred patients in Group II had the proximal anastomoses performed first so that cardioplegic solution also perfused beyond coronary obstructions as each subsequent distal anastomosis was completed. Aortic occlusion averaged 6 minutes longer in Group II (46.5 minutes) than in Group I (40.3 minutes) (p less than 0.01). Mortality from cardiac causes was six times greater in Group I than in Group II (6% versus 1% p = 0.027) and overall mortality was eight times greater in Group I than in Group II (8% versus 1%; p = 0.008). We conclude that earlier cardioplegic perfusion of myocardium beyond obstructed coronary arteries substantially improves myocardial protection.

Applicability and interpretation of electrocardiographic stress testing in patients with peripheral vascular disease.

Electrocardiographically monitored arterial stress testing was performed before surgery in 130 patients with peripheral vascular disease. When limitations of claudication or pain at rest precluded treadmill exercise, arm ergometry was employed. The electrocardiographically monitored arterial stress test proved a cost-effective, easily applicable means of screening for coronary artery disease in this group of patients. Unlike statistical analyses of historical risk factors, the electrocardiographically monitored arterial stress test evaluates the current functional state of the myocardium. We believe that preoperative electrocardiographic exercise testing should be employed more widely and should be considered in any patient facing major surgery in whom coronary artery disease is suspected on the basis of past history or known risk factors. In patients who have an ischemic response to exercise, particularly at less than 75 percent of the maximum predicted heart rate, coronary angiography and possibly coronary revascularization should be considered before elective major surgery is performed.