A comparison of paramedic versus basic emergency medical care of patients at high and low risk during acute myocardial infarction.

This prospective study compares the outcome of patients with acute myocardial infarction managed by mobile intensive care (paramedic phase) with that of similar patients managed by basic emergency medical care (control phase) in the same community before the introduction of paramedics. All paramedic-transported patients were managed according to a standard chest pain protocol with use of prophylactic lidocaine and, as needed, treatment for sinus bradycardia, hypotension and life-threatening ventricular arrhythmia. There were no specific interventions for supraventricular tachyarrhythmia or hypertension. All patients were treated under similar in-hospital protocols. Percent mortality in patients with hypotension, the highest risk subgroup in the control phase, was significantly lowered with paramedic-level care (69 versus 10%, p = 0.01). Patients with hypertension, a relatively low risk subgroup during the control phase (16% mortality), were also at lower risk during the paramedic phase (10% mortality). In fact, there was no mortality in either study phase for patients with an initial systolic blood pressure greater than 180 mm Hg. During the combined study phases, patients with normotension and tachycardia demonstrated a tendency toward higher percent mortality (33%) than either patients with normotension without tachycardia (10%) or those with hypertension and tachycardia (6%). Although the overall percent mortality was reduced by 24% (from 21 to 16%), this decrease was largely due to the improvement of patients with hypotension. Investigation into the feasibility of prehospital interventions for the high risk patient with acute myocardial infarction normotension and tachycardia appears warranted.

Prognostic value of a coronary artery jeopardy score.

The prognostic value of a coronary artery jeopardy score was evaluated in 462 consecutive nonsurgically treated patients with significant coronary artery disease, but without significant left main coronary stenosis. The jeopardy score is a simple method for estimating the amount of myocardium at risk on the basis of the particular location of coronary artery stenoses. In patients with a previous myocardial infarction, higher jeopardy scores were associated with a lower left ventricular ejection fraction. When the jeopardy score and the number of diseased vessels were considered individually, each descriptor effectively stratified prognosis. Five year survival was 97% in patients with a jeopardy score of 2 and 95, 85, 78, 75 and 56%, respectively, for patients with a jeopardy score of 4, 6, 8, 10 and 12. In multivariable analysis when only jeopardy score and number of diseased vessels were considered, the jeopardy score contained all of the prognostic information. Thus, the number of diseased vessels added no prognostic information to the jeopardy score. The left ventricular ejection fraction was more closely related to prognosis than was the jeopardy score. When other anatomic factors were examined, the degree of stenosis of each vessel, particularly the left anterior descending coronary artery, was found to add prognostic information to the jeopardy score. Thus, the jeopardy score is a simple method for describing the coronary anatomy. It provides more prognostic information than the number of diseased coronary arteries, but it can be improved by including the degree of stenosis of each vessel and giving additional weight to disease of the left anterior descending coronary artery.(ABSTRACT TRUNCATED AT 250 WORDS)

Basic emergency medical care of patients with acute myocardial infarction: initial prehospital characteristics and in-hospital complications.

This prospective study documents the natural history of the prehospital phase of 110 patients with acute myocardial infarction transported by a basic emergency medical system during a 22 month period. Ambulances in a mixed urban-rural county were staffed by basic emergency medical technicians certified in basic life support and the administration of intravenous fluids. Systolic blood pressure, pulse rate and cardiac rhythm were noted for all patients at the time of ambulance arrival and intermittently during transport. Analyses of patient data were performed to determine the relation between the occurrence of subsequent in-hospital urgent complications and death and 1) patient delay time, 2) initial pulse rate, 3) initial systolic blood pressure, and 4) initial cardiac rhythm. Twenty-three (21%) of the 110 patients died and 66 (60%) experienced at least one in-hospital urgent complication. When initial rhythm, pulse rate and blood pressure were considered, patients with hypotension had a higher mortality rate than did those who were either normotensive or hypertensive. The 10 patients with initial sinus bradycardia but no hypotension constituted a subgroup with zero mortality. These results identify high and low risk patient subgroups that may benefit from either providing or withholding interventions directed toward hemodynamic stabilization during the prehospital phase of acute myocardial infarction.

Out-of-hospital management of cardiac arrest by basic emergency medical technicians.

The outcome in 126 consecutive patients with nontraumatic out-of-hospital cardiac arrest was analyzed to determine the effectiveness of a standard ambulance system over 22 months. Therapy was limited to basic life support (that is, administration of oxygen by mask, i.v. fluids, closed-chest massage and artificial respiration) by emergency medical technicians in a community in which less than 1% of the population had been trained in cardiopulmonary resuscitation (CPR). Analyses of patient data were performed to determine the relations between survival to hospital admission or discharge and 6 variables; response time, prior CPR, initial rhythm, acute myocardial infarction, initial blood pressure and initial pulse. Of 126 patients, 28 (22%) survived to hospital admission and 11 (9%) to hospital discharge. Two patient subgroups had a higher discharge rate: those with an initial rhythm of ventricular tachycardia or fibrillation (7 of 50, 14%), and those with an initial blood pressure greater than or equal to 90 mm Hg and a pulse rate of greater than 50 beats/min (3 of 6, 50%). For patients in arrest before ambulance arrival, there was no difference in outcome between those who did or those who did not receive prior CPR. Results of this study can be used as a basis for evaluating and comparing interventions directed toward stabilization of patients during the prehospital phase of cardiac arrest.

Early discharge after acute myocardial infarction.

Approximately 50% of patients hospitalized with acute myocardial infarction have an uncomplicated course and an excellent prognosis. To be considered as having an uncomplicated course, patients should not have ventricular tachycardia or fibrillation, second or third degree atrioventricular block, pulmonary edema, cardiogenic shock, infarct extension, persistent hypotension, sinus tachycardia, or sustained supraventricular tachycardia occurring within the first 4 days of hospitalization. Patients with recurrent angina in the postinfarction period may also be at increased risk. Early and rapidly progressive rehabilitation programs permit the safe discharge of patients with an uncomplicated course after 7 days. Functional exercise testing before, or soon after, early discharge may identify high-risk patients and alter their management.

Hemodynamic effects of acute atrioventricular sequential pacing in patients with left ventricular dysfunction.

Acute atrioventricular (A-V) sequential pacing was compared with ventricular pacing in seven men with symptomatic left ventricular failure (New York Heart Association functional class III and IV) and depressed left ventricular ejection fraction (mean 29 percent, range 18 to 40). Cardiac index was higher during A-V sequential pacing than during ventricular pacing for every patient at paced rates of 75 to 100 beats/min. The mean increment was 17 percent (range 10 to 37) at a paced rate of 75 beats/min, 23 percent (range 8 to 45) at a paced rate of 85 beats/min and 29 percent (range 19 to 55) at a paced rate of 100 beats/min. The increase in cardiac index in an individual patient did not correlate with baseline characteristics including functional class, cardiothoracic ratio, resting ejection fraction, cardiac index or balloon-occluded pulmonary wedge pressure. Arterial pressure varied from beat to beat during ventricular pacing because of the changing relation of atrial to ventricular systole. When an atrial contraction preceded a ventricular paced beat by a physiologic interval intraarterial pulse pressure uniformly increased. That increase correlated strongly (r = 0.993) with the increase in cardiac index that occurred during A-V sequential pacing. Measurement of the pulse pressure during A-V dissociation is a simple technique that may be useful for predicting the degree of improvement in cardiac output expected with methods of pacing that restore A-V synchrony.

Pirmenol, a new antiarrhythmic agent: initial study of efficacy, safety and pharmacokinetics.

Pirmenol (CI-845), a new antiarrhythmic drug, was studied for the first time in humans to establish a minimum effective i.v. dose in 10 patients with chronic, stable premature ventricular complexes (PVCs) and to evaluate toxicity and pharmacokinetics. Infusions of 70-150 mg were associated with a 90% or greater reduction in PVCs nine of the 12 times they were administered to six patients. Peak plasma concentrations were 1.0-3.8 micrograms/ml at the end of these infusions. At the same time, small but significant increases in diastolic blood pressure (4 mm Hg) and QTc interval (0.01 second) were seen, but both values were within the normal range. Pirmenol was associated with no change in heart rate, systolic blood pressure, PR interval or QRS duration, renal, hepatic or hematologic function, or symptoms. Blood, plasma and free drug concentrations declined biexponentially after cessation of a 150-mg infusion (n = 4), with a terminal half-life of 7-9.4 hours. The therapeutic response, lack of toxicity, and relatively long half-life indicate that pirmenol is a promising antiarrhythmic agent.

Effects of oral hydralazine on rest and exercise hemodynamics in patients with aortic or mitral regurgitation and left ventricular dysfunction.

The hemodynamic effects of afterload reduction were studied at rest and during two levels of upright exercise in patients with aortic or mitral regurgitation and left ventricular dysfunction. Eleven patients underwent invasive hemodynamic monitoring before and after 50-70 mg of oral hydralazine was given ever 6 h for 48 h. At rest, heart rate and mean arterial pressure after hydralazine were unchanged from control. During exercise, there was no significant change in heart rate, but mean arterial pressure fell significantly during the first level of exercise. Systemic vascular resistance was elevated before hydralazine and was significantly reduced after treatment at both exercise levels. After hydralazine, the resting oxygen consumption was significantly elevated at rest but was unchanged during exercise, the arteriovenous oxygen difference was significantly narrowed at both rest and exercise, and the pulmonary capillary wedge pressure was also significantly lower at both rest and exercise. In this select group of patients who are not candidates for surgical valve replacement, chronic afterload reduction with oral hydralazine may result in increased cardiac performance, decreased pulmonary congestion, reduced myocardial oxygen demands, and improvement in resting and/or exertional symptoms.

Rest and exercise hemodynamic effects of oral hydralazine in patients with coronary artery disease and left ventricular dysfunction.

To determine the hemodynamic effects of afterload reduction at rest and during upright exercise in patients with coronary artery disease and left ventricular dysfunction, 12 patients were studied before and after taking 50-75 mg of oral hydralazine every 6 hours for 48 hours. Oxygen consumption and heart rate were unchanged from control both at rest and during two work loads on a bicycle ergometer. Cardiac output was significantly increased at rest and during both workloads. The arteriovenous oxygen difference was significantly reduced at rest and during exercise. Pulmonary capillary wedge pressure was also significantly lower at rest and during exercise. Systemic vascular resistance was reduced at rest, and exercise-induced vasodilation was augmented by the administration of hydralazine. Left ventricular end-diastolic volume and ejection fraction assessed by radionuclide angiocardiography were not significantly changed at rest or during exercise after hydralazine. Seven of the 12 patients have maintained clinical improvement during a follow-up of 6-12 months. Hemodynamic improvement provided by oral hydralazine at rest is maintained during moderate exertion in patients with coronary artery disease and left ventricular dysfunction. In selected patients, chronic afterload reduction with oral hydralazine may result in increased cardiac reserve, decreased pulmonary congestion or decreased myocardial oxygen demands, thereby improving or abolishing resting or exertional dyspnea or angina.

Arrhythmias during myocardial infarction: Mechanisms, significance, and therapy.

Mobile coronary care, continuous electrocardiographic monitoring, electrical defibrillation, and effective antiarrhythmic agents have each contributed to the major advances made in the detection, prevention, and treatment of arrhythmias during myocardial infarction. Ventricular ectopy within the first few minutes of acute myocardial infarction is still a major cause of death in patients with coronary artery disease, and future work, including education of at least selected members of the lay population in the techniques of cardiopulmonary resuscitation, will be necessary to significantly reduce the incidence of prehospital sudden death. For patients who survive the early minutes of infarction and receive medical attention, the short and long-term prognosis is now largely determined by the amount of myocardium which is permanently affected by the ischemic process. The influence of disturbance of heart rate and rhythm on the balance between myocardial oxygen supply and demand, on hemodynamic function of the heart, and on experimental infarct size has been recognized. Future work must therefore also confirm that prevention and early therapy of potentially deleterious arrhythmias will limit infarct size, improve the short-term prognosis of patients with myocardial infarction, and decrease the incidence of late sudden death.

The clinical significance of bundle branch block complicating acute myocardial infarction. 2. Indications for temporary and permanent pacemaker insertion.

The indication for prophylactic temporary and permanent pacing during acute myocardial infarction (MI) complicated by bundle branch block is high risk of progression via a Type II pattern to second or third degree (high degree) AV block during hospitalization or follow-up. In this study, determinants of high degree AV block during hospitalization and sudden death or recurrent high degree block during the first year of follow-up were examined in 432 patients with MI and bundle branch block. Timing of onset of bundle branch block, the involved fascicles, and the PR interval were examined as determinants of risk of progression to high degree AV block during MI. At highest risk were 186 patients with blocks involving the right bundle and at least one fascicle of the left bundle which were not documented on prior electrocardiograms. Risk was similar with (38%) or without (31%) accompanying first degree AV block. Patients with transient high degree AV block during MI had a 28% incidence of sudden death or recurrent high degree block during the first year of follow-up. Patients not continuously paced had a higher incidence of sudden death or recurrent high degree block than patients continuously paced (65% vs 10%, P less than 0.001). Sudden death during follow-up also occurred in 13% of patients without high degree block during MI. A subgroup with 1) documented prior MI, 2) anterior or indeterminant acute MI, and 3) no symptoms of cardiac failure had a 35% risk of sudden death. The role of permanent pacing in this group is unknown. Thus, patients at high risk of high degree AV block should receive prophylactic temporary pacing. Patients who survive high degree block with MI should receive temporary and then permanent pacing. Patients without high degree AV block during MI who nervertheless have a high risk of sudden death may benefit from permanent pacing.

The clinical significance of bundle branch block complicating acute myocardial infarction. 1. Clinical characteristics, hospital mortality, and one-year follow-up.

To provide an understanding of the clinical characteristics of patients with acute myocardial infarction (MI) and bundle branch block, experience from five centers was accumulated. Patients in whom bundle branch block first appeared after the onset of cardiogenic shock were excluded. In 432 patients, the most common types of block were left (38%) and right with left anterior fascicular block (34%). In 42% of the patients, bundle branch block was new. Progression to high degree (second or third degree) atrioventricular (AV) block via a Type II pattern occurred in 22% of the patients. Hospital and first year follow-up mortality rates were 28% and 28%, respectively. Only 46% of the patients developed pulmonary edema or shock (Killip Class III or IV), and hospital mortality was related to the amount of heart failure (8%, 7%, 27%, 83% for Killip Classes I-IV, respectively). Patients with progression to second degree or third degree AV block via a Type II pattern had increased hospital mortality compared with patients without this complication (47% vs 23%, P less than 0.001). In the absence of pulmonary edema or shock, patients with Type II second degree or third degree AV block still had a higher mortality rate than patients without advanced AV block (31% vs 2%, P less than 0.005), with nearly all the deaths due to abrupt development of AV block. Thus, in many patients MI with bundle branch block is associated with severe heart failure. However, this was not true for a majority of the patients, in whom therapy aimed at preventing morbidity and mortality due to the bradyarrhythmia of advanced AV block might be beneficial.