THE BALLISTOCARDIOGRAM AND THE BLOCKAGE OF CIRCULATION THROUGH LIGATURE OF

BOTH VENAE CAVAE

PEDRO COSSIO, M.D., JULIO A. BERRETA, M.D., AND

HECTOR E. Mosso, M.D.*

BUENOS AIRES. ARGENTINA

E XPERIMENTAL work in dogs was carried out in order to give a basis to the ballistocardiogram. In the first instance, myocardial damage was induced

by ligature of a coronary artery or by myocardial cauterization. This was followed constantly by ballistocardiographic alterations.’ This paper deals with the elimination of the blood circulation factor in the ballistocardiogram.

METHOD

Twelve dogs, varying in weight, were anesthetized with intraperitoneal Nembutal. The blockage of the circulation was performed by ligature of both venae cavae and azygos veins, following the technique described in a previous paper. It was known that cardiac activity is not impaired up to eight minutes after the ligatures are placed.2J

An electromagnetic ballistocardiograph connected to Siemens electrocardio- graph was used, standardized so that 1 millivolt would correspond to a displace- ment of 1 cm. The dogs were placed on their backs with the ballistocardiograph on their hind legs. The tracings were registered before and after the thoracic opening and every minute after the operation was performed, until standstill of the heart ensued (ordinally within eight to twelve minutes).2s3

In nine instances the ligatures were permanent, while in three the blockage was intermittent. Blocking and unblocking were done two and three times every two or three minutes.

REGULTS

The ballistocardiograms prior to thoracic opening were polymorphic in their general appearance and height as described in the first experience, but constant in the same animal and therefore allowing further comparisons. After the thoracotomy and the dissection of the veins, the volume of the tracings increased with stronger and faster heart beats as easily observed.

After the ligatures in six dogs, the height of the tracings increased immedi- ately, running parallel with the height and speed of each heart beat in the first

Aided by a research grant from the Squibb Institute for Medical Research, E. R. Squibb & Sons, Argentina 9. A. Laboratories de Investlgacion, Argentina.

Received for publication June 26, 1954. *Dr. I. Perlanes performed the surgical part of the work.

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COSSIO ET AL.: BCG AND CIRCULATION RLOCKAGE 73

five or six minutes. The height and speed of the heart beat were so marked that the entire body of the animal was beating. This phenomenon was noticeable even on the operating table. At this moment. the heart beat “in vacua”, that is to say, without any blood entering or leaving it. The blood pressure was zero and the opening of the carotid artery did not give a drop of blood. The de- flections of the ballistocardiogram were easily detected and at times more clearly defined than before.

Pig. l.-Dog ballistocardiogram.

Seven minutes after the interruption of circulation the heart beat was re- markably weaker, and the height of the deflections diminished; finally, after a few seconds, they could not be registered (Fig. 1).

In the other three dogs, the ballistocardiogram showed small and irregular deflections from the start, coinciding with smaller and slower heart beats which were not transmitted to the thoracoabdominal wall of the animal (Fig. 2). The heart stopped or ventricular fibrillation appeared much sooner in this group of animals.

74 ,\MEKICAN HEART JOURNAL

Fig. 2. -Dog ballistocardiogram.

Fig. 3.-Dog ballistocardiogram.

COSSIO ET AL.: KG .iND CIKCUI..\TION HLOCKAGE 7 5

In the animals in which the ligature was intermittent, the deflections were easily registered, and in two of them, increased as the ligature was placed and decreased as it was removed (Fig. 3).

DISCUSSION

These experiments have confirmed our previous report on the great poly- morphism of the ballistocardiogram in the several dogs. This is of course a great difficulty for the correct evaluation of ballistocardiographic records of different animals, but successive tracings on the same animal can be compared to those obtained prior and after the experiments.

The importance of the heart beat in the origin of the ballistocardiogram is stressed by this experiment. The other factors (systolic output, arterial elas- ticity, length and diameter of the aorta, peripheral resistances) are not essential. The shape of the tracing is registered the same, even when the blood supply of the heart is stopped, and there is no incoming or outgoing blood. So all these factors are secondary and would influence the tracing only through the changes they may determine in the movements originated by the heart beat. As for the meaning of each deflection we must bear in mind that notwithstanding the blockage of circulation, the general pattern and number of deflections are not altered, just as if the heart were still expelling blood. Therefore, the extra- cardiac origin of certain deflections (those due to the pressure wave of the blood that circulates in the arterial tree)4 is of less importance.

In our opinion, it should be admitted that there are only one or two earl!. essential systolic deflections and that the others are pendular secondary waves. The latter are caused by a vibration movement that dies out progressively, and they could be influenced by forces originated in the circulation of blood.

The increased height of the ballistocardiographic deflections after the ligature of both venae cavae may be attributed to theelimination of the resistance to circulation. The heart is beating then without the resistance which in normal circumstances is generated by the movement of the liquid mass. The heart beats were of such intensity and volume that they irradiated to the whole surface of the body and at times even to the operating table, even with the cardiac. ischemia due to the blockage of circulation. It is common knowledge that myocardial ischemia without eliminating peripheral resistances originates hypo- kynesia of the myocardium registered graphically by Wiggers and associates”,” and more recently Prinzmetal and associates’ with ultra rapid films. This woulti also be the explanation for the 3.5 per cent of cases in which the volume of tht, ballistocardiogram did not increase but even decreased after the ligature. The small and slow heart action did not induce a beat even in the epigastric region and would be explained by hypokinesis of the myocardium, in spite of the elimi- nation of the resistances. In those conditions, we came to the conclusion that in dogs with marked heart beat after the ligature of the caval veins, the ballisto- cardiographic deflections were of large volume and well defined, and that beats of smaller volume generated smaller and less defined deflections.

The ballistocardiogram is therefore fundamentally caused by the heart action and may be due only in a small measure to the circulation of the blood.

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On the other hand, we believe “sensu strictu” that there are only one or two principal systolic deflections. The other deflections represent pendular move- ments of the body dying out, as proved graphically by the tracings registered during bradycardia. In this case, the lengthening of diastole favors the regis- tration of those movements (Fig. l), which could be influenced by forces originated in the circulation of blood.

SUMMARY

We have analyzed in twelve dogs the action on the ballistocardiogram of the blockage of the circulation through ligature of both venae cavae. In nine in- stances the ligature was permanent, while in three the blockage was intermittent, blocking and unblocking two and three times every two or three minutes.

The ballistocardiograms prior to thoracic opening were polymorphic in their general appearance and height, but constant in the same animal, and therefore allowed further comparisons. After the ligatures in six dogs, the height of the tracing increased immediately, running parallel with the height and speed of each heart beat. The ballistocardiographic deflections were very easily detected and at times more clearly defined than before, yet the heart was beating without blood. In the other three dogs, the ballistocardiograms showed small and irregular deflections from the start.

In the animals in which the ligature was intermittent, the deflections were easily registered, and in two of them increased as the ligature was placed and decreased as it was removed.

The ballistocardiogram is therefore fundamentally caused by the heart action and may be due in a small measure to the circulation of blood and peripheral factors.

The increased height of the ballistocardiographic deflections after the ligature of both venae cavae (the shape remains unchanged) may be attributed to the elimination of the resistance of circulation.

REFERENCES

1. Cossio, P., Berreta, J. A., Mosso, H. E., and Perianes, I.: El balistocardiograma en la agresibn mrocbrdica experimental, Rev. Arg. de Card. 20:85, 1953.

2. Perianes, I., and Berreta, J. A.: Interruption de la circulacibn. Mantenimiento artificial de la circulacibn encefllica y coronaria, Bol. y Trabajos de la Sociedad Arg. de Ciru- janos, Atio XI; Sesidn de1 5 de junio de 1950.

3. Perianes, I., and Berreta, J. A.: Efectos de la interruption de la circulacibn con o sin perfusi6n de1 cabo cefalico de am bas carbtidas, Medicina 10:337, 1950.

4. Dock, W., Mandelbaum, H., and Mandelbaum, R. A.: 1953, The C. V. Mosby Co.

Ballistocardiography, St. Louis,

5. Tenant, R., and Wiggers, C. G.: The Effect of Coronary Occlusion on Myocardial Con- traction, Am. J. Physiol. 112:351, 1935.

6. Wiggers, C. J.: Physiology in Health and Disease, ed. 5, Philadelphia, 1950, Lea & Febiger. 7. Prinzmetal, M., Schwartz, L., Corday, E., Spritzler, R., Berman, H., and Kruger, H. E.:

Studies on the Coronary Circulation. Loss of Myocardial Contractility After Cor- onary Artery Occiusion, Ann. Int. Med. 31:429, 1949.