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The Kinematic Viscosities of Blood in Normal and Rheumatoid Arthritic Subjects.
Experiments indicate that the murmurs heard in the hearts of rheumatic fever subjects arise from turbulent blood flow. It is known that in a given circuit a transition from stream-line flow to turbulent flow may be produced by an increase in the velocity of flow above or a decrease of the viscosity below certain critical values Thus one possible explanation of the complete absence of murmurs in the hearts of rheumatoid arthritic subjects may be a whole-blood viscosity of more than normal value. To test this possibility the blood (and plasma) viscosities for a series of patients suffering from rheumatoid arthritis have been measured at normal blood temperature and the same measurements have also been made for a control series. Though average values a little in excess of the average control value have been found for whole blood and for plasma, it is considered the effect is too small to explain the absence of murmur which it is thought lies in the different acoustic behaviour of the heart in the two cases.
This abstract only is submitted here, as the paper is to be published in full in the N.Z. Medical Journal.
Notes. Mr. Sagar commenced his address with an outline of the physics of viscosity and turbulence, showing their application in regard to blood and blood vessels, demonstrating how increased blood viscosity would decrease turbulence and thus diminish the likelihood of development of abnormal heart sounds in rheumatic-arthritic cases, if increased viscosity of the blood could be demonstrated. If this were proven, it would explain the failure of clinicians to detect by abnormal heart sounds any abnormality of the heart, but enlargement of the heart might still be shown by means of X-ray. Evidence of increased viscosity, however, must be regarded as unproven.
Dr. Fischmann had demonstrated the absence of clinical signs of a so-called “rheumatoid-arthritic heart” in cases of rheumatoid arthritis, and been unable to obtain evidence of disease electrocardiographically. In the absence of actual post-mortem examination of any of the hearts discussed, no pathological evidence was forthcoming, whilst radiological examination by Dr. Gwynne of the cases showed definite heart enlargement in 15 out of 60 cases of rheumatoid arthritis, a very much higher proportion than would be expected by the examination of non-rheumatic persons. This seemed to confirm the American view.
Discussion of Papers by E. J. Fischmann and F. J. Gwynne and F. H. Sagar.
Dr. Caughey asked regarding the nutrition of the cases, mentioning the high percentage of achlorhydria present in such cases, with a possibility of avitaminosis, which could be a possible cause of the heart enlargement, it being due to a mild degree of beriberi. This would also account for the low voltages evidenced on the electrocardiographs of certain of the cases examined. He stated that treatment with large doses of Vitamin B1 and review of the cases after a period of this treatment would shed more light on this possible aspect of the
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heart enlargement. He also asked whether changes of the viscosity could be due to different times of testing and whether they were correlated with the times of food intake.
Dr. Gwynne replied that the possibility of beriberi had been considered, but it did not appear to fit in with the rest of the picture. Dr. Fischmann stated that some of the cases had been given small doses of vitamins by tablet form, but admitted that beriberi would not react to the small doses given; all cases were, however, on fairly high Vitamin B diets. He also stated that in the cases of low voltage discovered in the investigation, only one had an enlarged heart; none of the cases showed any signs of heart failure or oedema, as would have been likely if the heart enlargement shown had been due to beriberi.
Mr. Sagar stated that all viscosity tests had been taken at the same time of the day, and that possibilities of variation due to dietetic habits had been excluded.
Dr. Gwynne further stated that he could not establish that the radiological enlargements demonstrated were actually correlated with pathological changes, nor was he claiming that changes would be shown here similar to those in certain hearts of rheumatoid arthritics demonstrated in America.
Dr. Malcolm asked Dr. Gwynne regarding the technique used by him in measuring the diameters of the hearts, particularly as to whether all radiographs were taken at the same time in the heart cycle. He stated the absence of heart sounds is probably relative, and that special microphones might bring into evidence some correlation of sounds with the enlargement, though change in resonance and size of the heart cavities might have something to do with the failure to record sound changes.
Dr. Gwynne replied that since his technique for taking the rheumatoid arthritic hearts was the same as for taking normal hearts with which they had been compared and that the only enlargements considered were those where there had been more than 1.5 cm. above normal, he considered the enlargement was really quite definite.
Dr. Fischmann stated that the patients had been treated on the assumption that where heart dilatation had been shown by X-ray, valvular heart disease was present, but not shown. He was rather pessimistic regarding the use of microphones for detecting abnormal heart sounds, as mere augmentation of the sounds present produced similar enhancement in the accessory sounds, which masked the ones which were being searched for. The work done by Mr. Sagar had shown the need for much greater co-operation between physicists and medical men, if we were really going to get to the bottom of these problems.