George W. Manning

Protective effect of beta adrenoceptor blockade in experimental coronary occlusion in conscious dogs

To assess the effect of beta blockade and membrane stabilization on the outcome of acute coronary artery occlusion, anesthetized dogs were prepared with a ligature at the origin of the circumflex branch of the left coronary artery under direct vision. The dogs were allowed 48 to 72 hours to recover. A total of 154 dogs randomly allocated to 8 treatment groups were given intravenous injections of saline solution, doses of blocking agents found to block isoproterenol-induced tachycardia by 50 or 100 percent (or both) in the study dogs, or equivalent membrane-stabilizing doses of d-propranolol. Of these, 141 dogs met strict criteria for proper ligation. The 2 hour mortality rates were as follows: 72 percent of 25 dogs given 2 to 3 ml of saline solution, 24 percent of 25 dogs given 0.1 mg/kg and 70 percent of 10 given 1 mg/kg of dl-propranolol (Inderal®); 28 percent of 25 dogs given 0.2 mg/kg and 17 percent of 12 given 3.2 mg/kg of MJ-1999 (Sotalol®); 69 percent of 16 dogs given 0.07 mg/kg of dpropranolol; 17 percent of 12 dogs given 0.07 mg/kg of d-propranolol + 0.2 mg/kg of Sotalol; and 31 percent of 16 dogs given 1.4 mg/kg of AY-21,011 (Practolol®). All but 6 deaths were due to ventricular fibrillation. The larger dose of dl-propranolol was associated with more conduction defects, cardiac standstill and greater mortality than the smaller dose. Thus, significant protection (P <0.001) was conferred by the smaller dose of dl-propranolol, both doses of Sotalol, the mixture of d-propranolol and Sotalol, and Practolol. Similar patterns were seen with 24 hour mortality rates. The study shows that protection is due mainly to the beta receptor blocking rather than the membrane-stabilizing actions of these agents.

Cardiac manifestations in Freidreich's ataxia☆

Abstract Six cases of Friedreichs ataxia have been described, four of which showed classical pictures and two of which were considered to be variants of the disease. Cardiac manifestations were observed in four of these cases; in the remaining two no cardiac changes were noted; these cases, however, showed increased deep reflexes and might be considered as variants of the classical picture. Two patients were admitted to the hospital for treatment of the cardiac disorder and two cases were discovered while the patients were in the hospital during investigations of the neurological disorder. On examination, in addition to the neurological features, a rapid, irregular heart action was noted in three patients, two of whom required treatment for Stokes-Adams-like attacks and acute heart failure. In the third case the rapid, irregular rhythm had resulted in “palpitation” and dyspnea which, however, had not become a major complaint to the patient. In the remaining three patients there were no cardiac symptoms or signs; one of these showed the classical Friedreichs syndrome and electrocardiographic abnormalities. The electrocardiogram revealed multiple auricular and ventricular extrasystoles in three patients, with paroxysms of tachycardia in two of these. One other patient showed only T-wave abnormalities. The remaining two were considered normal, although one showed a marked sinus arrhythmia and minor degree of right axis deviation. Four cases showed significant T-wave abnormalities resembling cardiac infarction, and these occurred in the four patients with absent deep reflexes. A notable feature of these cases was the irregular heart action leading to cardiac insufficiency requiring treatment. This has not been a finding associated with the Friedreichs ataxia but has been reported as the principle clinical feature in familial cardiomegaly. The pathological similarity between Friedreichs disease and familial cardiomegaly is discussed, together with a review of the literature related to the heredo familial variants of Friedreichs ataxia, including a family in which both Friedreichs and heart disease has occurred. From the cases presented in this report there is a close relationship between the cardiac manifestations of the Friedreichs Ataxia and familial cardiomegaly. The pathological similarity, the familial nature, and similar clinical features of both, together with the known variants of the Friedreich group, including families with both Friedreichs ataxia and heart disease (in different members), support the concept that the lethal gene (or faulty germinal mutation) may result in familial heart disease occurring alone within the heredofamilial group of disorders.

An electrocardiographic study of 17,000 fit, young Royal Canadian Air Force aircrew applicants∗

Abstract In this study the electrocardiograms of 17,000 fit Royal Canadian Air Force aircrew applicants between the ages of eighteen and twenty-four have been reviewed. In 954 instances abnormalities of varying degrees were observed and repeat electrocardiographic studies, including further investigation, were carried out by a cardiologist in all but a few instances. There were eight-six applicants classed as unfit for pilot training on the basis of an abnormal electrocardiographic finding which could not be explained or accounted for on a physiologic or environmental basis. A few were found to have organic heart disease. A larger number (total of forty-five including proved heart disease) were found to have questionable findings either in the history or on clinical examination (cardiac murmurs, elevated blood pressure, questionable roentgenographic findings, history of tachycardia, syncope, trauma to the chest, infectious diseases, etc.) that may or may not have had some bearing on the electrocardiographic findings. These eighty-six men, however, were not accepted for pilot training on the basis of the abnormal electrocardiogram.

Postural heart block

Abstract (1) We have observed a total of 59 cases of first degree heart block with a P-R interval 0.24 second or greater in a consecutive series of 19,000 fit, young aircrew applicants. None has been associated with proved organic heart disease. Of the prolonged P-R intervals, 85 per cent were reduced to within normal limits in the standing position. (2) The reduction of P-R interval by standing, atropine, and exercise does not differentiate innocent postural heart block from that occurring in organic heart disease. (3) The clinical findings in these cases and follow-up studies to date do not indicate that isolated A-V block is indicative of organic heart disease, but rather is a manifestation of increased vagal tone.

Routine electrocardiography: Postprandial T-wave changes

Abstract 1. 1. In 2,000 consecutive routine electrocardiograms recorded at random throughout the day in healthy, fit men (aged 17 to 24 years) postprandial T-wave changes occurred in 78 cases, or 3.9 per cent. 2. 2. Whenever questionable T-wave findings are present in either routine or diagnostic tracings, a repeat tracing should be recorded in the fasting state. 3. 3. The present evidence supports the view that isolated postprandial T-wave changes are of no pathologic significance. 4. 4. Consideration should be given to the recording of the electrocardiogram in the fasting state wherever possible, particularly when tracings are recorded in connection with routine medical examination.

The initiation of ventricular tachycardia and fibrillation in experimental coronary artery occlusion

Abstract Ninety-four dogs were studied electrocardiographically following acute occlusion of the circumflex branch of the left coronary artery in an attempt to elucidate the electrogenesis of ventricular arrhythmias. In terminal ventricular fibrillation, T wave interruption was invariably present, occurring at the peak or on the downslope of the T wave, and was progressively greater in two thirds of the recorded episodes. In nonterminal ventricular tachycardia, T wave cutoff (present in only one fourth of the episodes) was found near the end of the T wave and was progressively less in successive cardiac cycles. The commonest type of T wave interruption associated with ventricular arrhythmias occurred when an extrasystolic T wave was interrupted by the QRS of the succeeding ventricular extrasystole (V by V type). This was not seen in isolated ventricular premature beats. The drop in arterial pressure was quantitatively related to the degree of T wave interruption.

Value of apex cardiography in the assessment of cardiac aneurysms

Abstract Ultralow-frequency displacement curves of anomalous precordial pulsations in 3 cases of postinfarction ventricular aneurysm were recorded simultaneously with an apex cardiogram. The tracing in the case of complete thrombotic obliteration of the aneurysmal sac was characterized by a double systolic peak and a brief rapid-filling wave terminating in a diastolic bulge. In contrast, the tracings of the other 2 cases, presumed to have no significant obliteration of the aneurysmal cavity, showed a sustained systolic thrust with a delayed peak and absence of a rapid-filling wave. A mechanism is postulated to explain the differences.

The effects of cortisone and ACTH on artificially induced cardiac infarction in the dog

Abstract It would appear from this small series that ACTH and cortisone have little or no effect on the healing of experimentally produced cardiac infarction in the dog, and that the use of these substances does not influence in any way the immediate mortality following sudden coronary occlusion in the conscious dog.

Discussion (Lipid Clinic I)

The multivariate analysis of factors associated with the dietary lowering of serum cholesterol in a group of patients with type II hyperlipoproteiemia and obesity, averaging 112% of ideal weight, suggested that weight loss was the most important factor, having three times the effect of reduced dietary saturated fat.

Discussion (Current Investigations in Myocardial Perfusion)

In discussion Dr. Klassen questioned Dr. Bloor’s use of the word Model 4 “aortic stenosis”. He asked whether the stenotic lesion was introduced below the take-off of the coronary arteries or above it as in coarctation. Dr. Bloor replied that the latter was the case and that the lesion more closely simulated a coarctation than aortic stenosis.