In a number of other instances, however, in which there was more or less granular degeneration and cloudy swelling we found that the right ventricle ceased in diastole without, however, the capacity of the chamber being enlarged. We would make this differentiation in speaking of dilatation of the heart. We have met with 11 cases in which the right heart died in diastole, but in which there was no evidence that the right ventricle had been unduly expanded. In four cases there was evidence of an old compensatory hypertrophy of the left ventricle in which the cavity of this chamber was also slightly larger than normal. The lesions in these four cases, however, bore no direct relation to the results from the influenza infection. The appearance of the musculature with moderate grade of cloudy swelling suggested some œdema of the tissues. In the myocardium, œdema is difficult to recognize, and we would not place great stress upon its presence in mild degree.
The microscopic examination of the myocardium showing cloudy swelling gave the usual picture as is seen with a variety of infections. The muscle fibers showed a fine granular deposit in their cytoplasm and the staining quality of the tissue was somewhat altered. The transverse striæ were less distinct than normal, while not uncommonly the longitudinal fibrils became more evident. Fatty degeneration was not encountered.
In the single case showing a definite and acute dilatation of the ventricles the cause of the myocardial lesion could not be placed at the door of the influenzal infection. This was the case suffering from a secondary streptococcal bacteriæmia arising in the middle ear. It is more than probable that the streptococcus was the immediate cause of the acute muscle change and weakening. In a number of cases we have studied the tissues of the bundle of His, but we were unable to note any definite change.
It is interesting that the intoxication associated with acute influenza is selective in localizing in certain muscle tissues. We have previously indicated the intensity of muscle degenerations occurring in the abdominal recti. Even in these cases where these striped voluntary muscles were markedly affected the myocardium showed nothing more than a mild or moderate grade of cloudy swelling. We can only account for this in a difference in the constitution of these muscular structures, some being of such composition permitting of the localizing and damage by the unknown intoxicant. It does not appear that the reason for localization in certain tissues is in any way related to the character of the blood supply, nor is it related to the activity of the part.
In three cases we have found an inflammatory lesion of the endocardial tissues. In all of them this consisted of a slight acute verrucose mitral endocarditis. The lesions were very small, consisting only of a fine granular deposit looking like grains of sand localized along the border of the mitral leaflets. In no instance was the leaflet injured or incapacitated. Unfortunately the lesion not being suspected was encountered after the heart had been removed and opened and when it was too late to make bacteriological analyses. This point is greatly to be regretted, in as much as it is of great importance to know whether some distant lesions are induced through the influenza bacillus or its symbiotic flora.
The majority of authors report but little upon the heart lesions in influenza. Many deny that a heart involvement is to be found, a few report an occasional endocarditis. Wallis and Kuskow found more or less myocardial change similar to what is usually described as cloudy swelling. This reaction they point out differs in no way from the degenerations arising from other types of intoxications. Keegan in a series of about 23 autopsies found only a single case with acute dilatation.
Abrahams, Hallows and French had an opportunity of observing over 400 autopsies upon the influenza patients, and they comment upon the infrequency of cardiac dilatation. A slight dilatation of the right ventricle was seen in a few cases, and in no instance did they find pericarditis or endocarditis. They comment upon the heart condition as follows: “The most remarkable feature about the heart is the general absence of dilatation. In quite a large proportion of cases there has been no trace of dilatation; in a fair number of others there has been some dilatation of the right side, but this has seldom been extreme, perhaps enough to cause the apex of the heart to be formed about equally by right and left ventricles. Most often the heart has appeared of normal dimensions and the apex has been formed entirely by the left ventricle. This absence of dilatation accounts for the clinical absence of orthopnœa.” In direct contradiction to the above findings, the Advisory Board to the D. G. M. S., France, report the findings in 30 autopsies of clinical influenza. Twenty-nine of these 30 cases showed dilatation of the heart, chiefly of the right side, but very commonly of the left side as well. Twenty-one showed myocarditis and two endocarditis. In this report it is stated that these patients showed evidence of obsolete tuberculosis. It is possible that the condition of the patients and the presence of an unusual complicating infection led to the high incidence of cardiac involvement. The figures in this last series are much too high when compared with the frequency of heart involvement as found by the majority of other investigators.
A number of heart lesions not resulting from influenza were observed. For none of them was there an antecedent history, but in some cases the condition may have had an influence in causing accessory cardiac embarrassment. One case had a chronic interstitial myocarditis of the rheumatic type, three had mild grades of chronic sclerotic mitral endocarditis, one a bicuspid pulmonary valve and three showed old pericardial adhesions, one of them having a complete obliteration of the sac. The foramen ovale was patent in six of the hearts.
Arteries
The arteries in these young adults were remarkably healthy, and in none of them did we observe the characters of arteriosclerosis or leutic lesions. On the other hand, evidence of superficial fatty streaks lying in the intima of the aorta and some of its large branches were not uncommon and are believed to have had a relation to the acute infection of which they died. In only four cases in the series of 32 autopsies was evidence of these fatty streaks wanting. In about one-half of the remaining number these fatty streaks were only slight or moderate in extent, while in the rest of them these lesions were particularly prominent and striking. They formed linear markings on the posterior wall of the aorta, aggregating with particular prominence about the intercostal arteries. The anterior wall was quite free from them. The greater extent of these lesions lay in the descending thoracic and was less marked in the arch and the abdominal aorta. At times these fatty streaks were found to extend into the large vessels of the neck and into the intercostal arteries, and they were also found in the coronaries of the heart. It was uncommon to observe their presence in the arteries of the abdominal viscera.