Potential for altering the natural history of congestive heart failure: need for large clinical trials

Congestive heart failure (CHF) is a major clinical and public health problem; moreover, its incidence is increasing. Once this syndrome is manifest, the mortality rate is very high. To date, none of the drugs available for its treatment has been shown to reduce mortality. It is theoretically possible that in patients with overt CHF, drug treatment may not alter prognosis. This hypothesis suggests that patients at high risk of heart failure should be treated before CHF becomes manifest. Alternatively, the trials of patients with manifest CHF may have been unpromising, simply because they were too small. These considerations indicate an urgent need for very large studies of both categories of patients--a "prevention" trial in those without overt CHF and a "treatment" trial in those with overt CHF.

Overview of randomised trials of diuretics in pregnancy

Over the past 20 years at least 11 randomised trials of the prevention with diuretics of pre-eclampsia and its sequelae have been undertaken. Nine of these were reviewed. Reliable data from the remaining two were not available. The nine reviewed had investigated a total of nearly 7000 people. Significant evidence of prevention of "pre-eclampsia" was overwhelming, even when oedema was not included as a diagnostic criterion. But as the definitions of pre-eclampsia that had been used depended heavily on increases in blood pressure this evidence may simply have reflected the well known ability of diuretics to reduce blood pressure. When the data on perinatal death were reviewed a little difference was seen in postnatal survival. The incidence of stillbirths was reduced by about one third with treatment, but, perhaps owing to small numbers (only 37 stillbirths), the difference was not significant. Thus these randomised trials failed to provide reliable evidence of either the presence or the absence of any worthwhile effects of treatment with diuretics on perinatal mortality. The implications of this for current and future trials of beta blockers and other agents in the prevention of pre-eclampsia and its sequelae are that extremely large, ultra simple randomised trials are needed, of a size sufficient to permit direct assessment of the effects of treatment not on pre-eclampsia but on perinatal mortality itself. This may require the study of tens of thousands of pregnancies.

The entry ECG in the early diagnosis and prognostic stratification of patients with suspected acute myocardial infarction

475 patients with suspected uncomplicated myocardial infarction (MI) were divided into 3 groups based on their entry ECG: group 1--significant ST elevation; group 2a--ST depression or T inversion; group 2b--normal ECG. Infarction was confirmed in 99.7% of group 1, 68.5% of group 2a and 39.7% of group 2b patients. Despite similar clinical, haemodynamic and historical variables at presentation, group 1 patients had significantly larger MI, more in-hospital complications and a higher short-term and long-term mortality (P less than 0.005) than group 2 patients. The entry ECG of patients with suspected MI is an excellent and simple predictor of those who are most likely to have an MI confirmed and identifies a group of patients at high risk of death or developing complications.

Reduction in infarct size, arrhythmias and chest pain by early intravenous beta blockade in suspected acute myocardial infarction

Four hundred seventy-seven patients suspected of having had acute myocardial infarction within less than 12 hours were randomized to receive i.v. atenolol followed by oral treatment for 10 days or to a control group. In patients with ECG changes indicative of infarction at entry, i.v. atenolol significantly reduced enzyme release by one-third and enhanced R-wave preservation. In patients without such ECG changes, treatment significantly prevented the development of infarction in a proportion of patients. There was also a significant reduction in R-on-T ectopics, repetitive ventricular arrhythmias and supraventricular arrhythmias. Treated patients had significantly greater pain relief and required fewer opiate analgesics. Significantly fewer atenolol-treated patients died by 10 days (the treatment period), had nonfatal cardiac arrests, developed heart failure, or suffered reinfarction.

Reduction of ventricular arrhythmias by early intravenous atenolol in suspected acute myocardial infarction

The effect of intravenous atenolol on ventricular arrhythmias in acute myocardial infarction was assessed in 182 patients admitted within 12 hours of the onset of chest pain. Ninety-five patients were randomised to receive 5 mg intravenous atenolol followed immediately by 50 mg by mouth and 50 mg 12 hours later, then 100 mg daily for 10 days; 87 patients served as controls. The treated patients had significantly fewer ventricular extrasystoles; 58 control patients (67%) had R-on-T extrasystoles compared with only 25 treated patients (26%) (2p less than 0.0001); repetitive ventricular arrhythmias were detected in 64 control patients (74%) and 55 treated patients (58%) (2p less than 0.05). Heart rate was significantly reduced from 77 +/- 1 beats/min at entry to 65 +/- 1 beats/min (2p less than 0.001) in the first hour after intravenous atenolol, and in addition the rate was significantly different from that in the control group. There was no difference in the incidence of heart failure, but fewer patients in the treated group received other antiarrhythmic agents or digoxin. These results show that early intravenous atenolol prevents ventricular arrhythmias in suspected acute myocardial infarction.

Factors of importance for QRS complex recovery after acute myocardial infarction

The regression of the ECG signs of myocardial infarction has been studied in 101 patients. A significant increase in R wave amplitude and decrease in Q wave depth on the standard ECG was observed over three months. In 21% of the patients, Q waves disappeared completely. In inferior infarction, these changes were more apparent in the lateral V leads than in the inferior limb leads. Patients with intraventricular conduction defects were excluded. Two factors associated with the Q and R wave changes have been identified. Lower heart rates appeared to facilitate the recovery of R waves, and smaller infarcts, as assessed by peak LDH, showed greater ECG recovery. This study raises the interesting possibility that modification of the heart rate may affect favourably the healing process after an acute myocardial infarction.

Ischemic pain relief in patients with acute myocardial infarction by intravenous atenolol

Pain relief in acute myocardial infarction (AMI) by the beta-adrenoceptor antagonist, atenolol, was demonstrated by three separate studies. First, 18 patients were randomized to double-blind intravenous atenolol (5 mg) or saline immediately after admission, followed by oral atenolol (50 mg) or placebo 10 minutes later. In patients receiving atenolol, pain relief coincided with reduction in heart rate (HR), systolic blood pressure (SBP), and HR X SBP product (p less than 0.05); however, pain and these parameters were unchanged by placebo. The degree of pain relief was related to the reduction in cardiac work achieved (r = 0.725; p less than 0.001). A second open study involving 22 patients receiving intravenous atenolol (5 to 15 mg) early after AMI showed ischemic pain relief in 17 patients. They achieved a more significant reduction in HR X SBP product than those whose pain remained unchanged (p = 0.004). Finally, a retrospective study of 163 patients randomized to either atenolol or no beta blockade early after AMI revealed that patients receiving atenolol needed less opiate analgesia after admission (p less than 0.001). The safety of this therapy was illustrated by a decreased incidence of left heart failure and atrial fibrillation and no tendency to second- and third-degree heart block.

Regional ischemic ventricular dysfunction in myocardium supplied by a narrowed coronary artery with increasing halothane concentration in the dog

The effects of increasing inspired halothane concentration (0.5, 1.0, 1.5, 2.0 per cent) upon left ventricular myocardium supplied by a critically narrowed coronary artery and a normal coronary artery were studied in 11 open-chested dogs. Regional ventricular function was measured by continuous recording of ventricular segment length using pairs of implanted miniature ultrasonic length detectors in the left anterior descending coronary artery (LAD) and left circumflex coronary artery (LC) territories before and during critical stenosis of the LAD by a micrometer-controlled snare. Critical narrowing was documented by ischemic regional ventricular function (i.e., post-systolic shortening; systolic lengthening) limited to the LAD territory when FIO2 = 0 for 90 seconds. Hemodynamic variables (aortic, left atrial and left ventricular pressure, and heart rate) were measured, ECG lead II was recorded, and the first derivative of left ventricular pressure (LV dP/dt) and coronary perfusion pressure derived for each halothane concentration before and during LAD narrowing. Increasing halothane was associated with equivalent progressive depression of global ventricular function before and during LAD constriction. Prior to LAD constriction, no ischemic changes in regional function occurred. Regional ventricular function was normal during 0.5 percent halothane in the presence of LAD constriction. With increasing halothane during LAD constriction, ischemic regional ventricular function was observed in the LAD territory in eight of eleven hearts, whereas regional ventricular function remained normal in the LC territory. The epicardial ECG was recorded in three dogs and was insensitive as an indicator of ischemia, becoming abnormal only after severe ischemic changes were established. In these studies, in which heart rate remained constant, arterial blood pressure and LV dP/dt decreased, and left ventricular end-diastolic pressure increased, decrease in blood flow and oxygen delivery due to a lower perfusion pressure distal to the coronary artery narrowing appears to be primarily responsible for the observations. The authors hypothesize that clinically unapparent episodes of regional myocardial ischemia distal to narrowed coronary arteries may be an important cause of perioperative myocardial infarction.

Variability of electrocardiographic and enzyme evolution of myocardial infarction in man

We have studied the time course of development of ST segment elevation, R wave loss, and Q wave development in 41 patients using 35 lead praecordial mapping or 12 lead electrocardiograms in those with anterior and inferior infarcts, respectively. The first recording was at a mean time of six hours after the onset of pain; subsequent records were taken every eight hours for 24 hours, every 12 hours for the second day, and every day thereafter. Serial CK MB estimates were obtained at every four hours for the first 72 hours. There was good agreement in the time course between the electrocardiogram and enzyme evolution. Forty-one per cent of patients showed rapid infarction with R wave and Q wave evolution complete within 12 hours of pain and accompanied by a short duration of enzyme release (mean = 19.30 hours). Fifty-nine per cent of patients showed more prolonged infarction with longer R wave and Q wave evolution and enzyme release (mean = 30 hours). Four patients also showed delayed reinfarction. ST segment elevation was maximal at six hours in the whole group and was significantly lower thereafter. Patients with rapid infarction showed high initial ST segment elevation which decreased promptly compared with those with prolonged infarction, who showed moderate but more persistent ST segment elevation. This study shows the variability in the time course of the electrocardiogram and enzyme evolution after myocardial infarction in man.

The role of serum myoglobin in the detection and measurement of myocardial infarction

The use of serum myoglobin determinations in the diagnosis and quantitation of acute myocardial infarction was studied in 53 patients. Serial blood samples collected for the first 72 h after pain were analysed for serum myoglobin using a radioimmunoassay procedure. Samples were also assayed for serum creatine kinase (CK) and its myocardial isoenzyme CK-MB, aspartate aminotransferase (AST) and alpha-hydroxybutyrate dehydrogenase (alpha HBDH). Analysis of first and second samples obtained at mean times of 7.6 and 10.7 h respectively after pain produced the following detection rate: serum myoglobin 85% and 98%; serum CK 71% and 85%; serum AST 58% and 81%; serum CK-MB 29% and 60%; serum alpha HBDH 23% and 33% respectively. Total CK-MB and myoglobin release from damaged myocardium were calculated using the method of Norris et al. [16]. A significant correlation was obtained between infarct size calculated from CK-MB and myoglobin in the whole group (n = 29, r = 0.71, p < 0.001). The correlation was even more significant for smaller infarcts with CK-MB release < 220 U/l (n = 13, r = 0.92, p < 0.001).

Heart rate and ectopic prematurity in relation to sustained ventricular arrhythmias

Forty-four patients with acute myocardial infarction were studied using 24-hour electrocardiographic monitoring. A linear correlation has been shown to exist between heart rate preceding accelerated idioventricular rhythm and ventricular tachycardia and the rates of these. The prematurity index was found to be inversely related to the preceding heart rate and also to the rate of accelerated idioventricular rhythm or ventricular tachycardia. Faster heart rates preceded extrasystoles with shorter prematurity indices and a significant inverse correlation was observed between preceding heart rate and prematurity index. Patients developing ventricular tachycardia had more frequent isolated ventricular extrasystoles and faster heart rates preceding the episode as compared with patients not showing ventricular tachycardia. No association was observed between ventricular tachycardia and accelerated idioventricular rhythm. All four patients developing ventricular fibrillation showed preceding ventricular tachycardia, with three of these patients demonstrating faster rates of ventricular tachycardia (greater than 170/min) and shorter prematurity indices (less than 0.80) than patients without ventricular fibrillation. Heart rate may influence the severity of ventricular arrbythmia; the prematurity of an extrasystole is of importance in patients developing accelered idioventricular rhythm or ventricular tachycardia.

Early intravenous atenolol treatment in suspected acute myocardial infarction. Preliminary report of a randomised trial

214 patients were studied in a randomised trial to determine whether administraiton of intravenous atenolol within 12 hours of chest pain reduced eventual infarct size, as estimated by cumulative enzyme release and by ECG changes. 135 patients already had ECG evidence of infarction at entry; 72 received atenolol which significantly decreased subsequent enzyme release (atenolol and control means = 121 IU, SE +/- 10 and 177 IU, SE +/- 17; 2p < 0.005) and enhanced R-wave preservation (atenolol and control means = 46% +/- 3 and 36% +/- 3; 2p < 0.02). 79 patients had no evidence of infarction at entry; 44 did not receive atenolol and 27 of these subsequently developed infarction, whereas only 11 of 35 treated patients infarcted during their hospital stay (2p < 0.01). In hospital, fewer atenolol patients died (4 vs 9), had non-fatal cardiac arrests (2 vs 6), or required therapy for heart-failure (36 vs 47). Unlike many previous trials which had negative results, in this trial we gave the drug intravenously and promptly (median of 4 hours from onset of pain to injecton), thereby achieving early beta-blockade.

Effect of atenolol on recovery of the electrocardiographic signs of myocardial infarction

The most notable changes in the 35-lead precordial electrocardiogram in 22 subjects in the first 6--12 months after acute myocardial infarction were a reduction in the amplitude of Q waves and a significant increase in the amplitude of the R waves. Patients who, in a random trial, had been given 100 mg atenolol daily from admission showed a significantly greater recovery in R-wave amplitude and decrease in Q waves than patients given placebo. It is concluded that atenolol improves the recovery of the electrocardiographic signs of myocardial infarction.

Value of electrocardiogram in predicting and estimating infarct size in man

The value of the electrocardiogram in assessing infarct size was studied using serial estimates of the MB isomer of creatine kinase (CK MB) in plasma, serial 35 lead praecordial maps in 28 patients with anterior myocardial infarction, and serial 12 lead electrocardiograms in 17 patients with inferior myocardial infarction. In patients with anterior infarcts, sigma ST, sigma R, sigma Q, sigma R/(Q+S), and the number of sites with ST elevation more than 2 mm or with QS waves, were obtained from each map. Correlation between both maximum sigma Q and maximum sigma ST with cumulative CK MB was highly significant. There was also a significant correlation between sigma R and sigma R/(Q+S) with cumulative CK MB. There was no significant correlation between maximum number of sites with ST elevation or with Q or QS waves and cumulative CK MB. Maximum sigma ST and number of sites with ST elevation predicted maximum sigma Q and number of sites with QS or Q waves at a time when infarction was not complete. In patients with inferior infarcts, there was a significant correlation between maximum sigma Q and maximum sigma ST in leads II, III, and a VF, and cumulative CK MB. This study shows that all the waves in the electrocardiogram are useful in assessing infarct size. The fact that maximum sigma ST predicts final sigma Q may be used to assess the efficacy of interventions designed to salvage ischaemic myocardium.