Coronary Angiographic and Scintigraphic Findings in Experimental Cardiac Contusion 1

Nuclear Medicine

Ching L. Chlu, M.D., James D. Roelofs, M.D., Raymundo T. Go, M.D., Donald B. Doty, M.D., Earl F. Rose, M.D., and James H. Christie, M.D. Clinical, angiographic, scintigraphic and pathologic observations in myocardial contusion were correlated. Radionuclide imaging of the injured heart with 99mTc-Sn-polyphosphate provides an accurate diagnosis in acute, even mild, myocardial contusion. The study can be carried out without danger to the critically ill patient. The coronary angiographic findings in this study explain what is occurring pathologically in the heart. Since arteriography is a more invasive technique than radionuclide imaging, its use is recommended only when the image is negative if it is necessary to establish the clinical diagnosis for treatment or when more than one week has elapsed since the injury. INDEX TERMS:

Coronary vessels • Heart, radionuclide studies • Heart, wounds and in-

juries Radiology 116:679-683, September 1975

ARDIAC

INJURY

due

to

nonpenetrating

chest

C trauma is not uncommon. The automobile, industrial and agricultural injuries of the heart due to closed chest trauma have increased and have become important clinical entities. It is well known that cardiac injury may occur without external evidence of chest trauma. The purpose of this study is to examine the coronary vascular changes of myocardial contusion due to closed chest trauma. Also, an improved diagnostic technique using radionuclide imaging is shown to demonstrate increased isotope uptake in the heart early after the injury. METHODS

Isolated myocardial Injury was produced by the impact of a captive-bolt handgun to the intact chest wall of 26 anesthetized dogs weighing 15-20 kg. A SuperCash pistol, originally designed for the abattoir industry, was modified by attaching a 2-inch semielliptical steel disk to the end of the force-transmitting piston. This device was held firmly against the left chest wall at the point of maximum cardiac impulse. The powder loads produced nominal velocity of 390-570 ± 45 feet/second of a %-inch (9.5 mm) diameter 350 grain ballistic slug fired in a test device. Group 1 dogs were sacrificed following myocardial contusion; these were examined immediately, 24 hours, 48 hours, 72 hours and one week post injury. Heparin (1000 U/kg) was administered prior to sacrificing the animal with intravenous nembutal. The heart and lungs were immediately removed en bloc. The ascending aorta was opened, and the coronary artery ostia directly cannulated and perfused with temperature-reversible gelatin containing barium. The pressure of injection var-

Fig. 1.

Angiogram of the "whole" normal dog heart with left coronary artery injected with the barium gel.

ied because the material was hand injected through a syringe. Temperature of the gelatin was above 90°C to maintain fluidity and after injection the hearts were immediately submerged in water at 15-20 oC to solidify the gelatin. The hearts were fixed by perfusion of the right atrium with 40 % formalin at 20-30 cm H20 pressure and suspension of the specimen in the fixative for

1 From the Departments of Radiology (C. L. C., J. D. R., R. T. G., J. H. C.), Surgery (D. B. D.), and Pathology (E. F. R.), University of Iowa Hospitals and Clinics, Iowa City, Iowa. Presented at the Sixtieth Scientific Assembly and Annual Meeting of the Radiological Society of North America, Chicago, III., Dec. 1-6, 1974. dk

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Fig. 2. Whole heart and t-ern thick section following mild contusion showing terminal extravasation from small branch vessels. Fig. 3. Angiogram and macrosection showing a large area of extravasation (arrow) in the left ventricle and interventricular septum.

24 hours. Absolute alcohol was used for 48 hours to harden the specimen and allow approximately 1.5 cm "bread-loaf" sectioning of the heart. High-resolution roentgenograms were made of the whole heart (Fig. 1) and the thick sections using 300 mA for 1-2 seconds at 25-30 KeV on Kodak-M film (1). Appropriate tissues were processed and sectioned at 4 J1 using hematoxylin and eosin, Movat and PTAH (phosphotungstic acid hematoxylin) stains for histologic examination. These findings were then correlated with the angiographic changes. The eight dogs of Group 2 were given 5 mCi 99mTcSn-polyphosphate. Contusion was achieved in the same manner under intravenous nembutal anesthesia. Control images of the chest in supine, left oblique and lateral views were made at intervals for a period of 1-2 hours after intravenous injection. The dogs were returned for follow-up imaging studies 24 hours, 48 hours, 72 hours and one week after contusion. A Searle Radiographics Pho/Gamma HP scintillation camera with a 16,000-hole collimator was used for imaging (2). A total of 550,000 counts was obtained in each projection.

RESULTS

Acute Contusion (Immediately, 24 and 48 Hours PostTrauma): Radiographic chest examination showed acute dilatation of the heart immediately after cardiac injury. The pulmonary findings ranged from negative to visualization of some alveolar infiltrates in the left lower lobe. Occasionally pneumothorax and rib fractures were noted. Follow-up chest radiographs taken two days later showed normal heart size and clear lungs in spite of previous laceration of the apical myocardium or some pulmonary contusion. Postmortem coronary angiograms showed similar vascular changes immediately, 24 and 48 hours after cardiac contusion. The main left coronary artery remained intact in mild or severe contusion in all dogs. Superficial patchy areas of myocardial hemorrhage were noted in mild contusion. The angiogram showed generalized arterial spasm and extravasation from terminal branch vessels (Fig. 2) in the area of injury in two dogs. Severe contusion with laceration of the apex and substantial hemorrhage but intact main coronary arteries

CORONARY FINDINGS IN CARDIAC CONTUSION

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Fig. 4.

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Nuclear Medicine

Macrosection on the left shows multiple giant capillary-sinusoidal vessels (arrows). Histologic section on the right shows that these vascular channels are lined by a single layer of endothelial cells.

Nt Fig. 5.

Fig. 6.

Angiogram and histologic section showing numerous kinked new vessels in the area of injury.

were noted in three dogs. A large area of extravasation of radiopaque contrast material (Fig. 3) was strikingly shown in the left ventricle and interventricular septum of four dogs. Giant capillary-sinusoidal vessels were also visualized (Fig. 4) and noted to be similar to the dilated collateral vessel seen in response to the stimulus of cardiac hypoxia as described in the review of the circulation to myocardium by Mautz (3). These structures were felt to be dilated capillaries rather than other ves-

sets because of a single layer of endothelial cells forming the wall. The radionuclide images showed no activity in the undamaged heart with normal uptake in the ribs, sternum, and vertebrae. The studies showed increased activity in the mildly and severely injured myocardium with strong uptake in the severe cases. The images remained positive through 24, 48 and 72 hours after trauma (Fig. 5). This increased activity as seen in the in vivo

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scan was shown to correspond to the increased activity in a study of the hearts with a scintillation camera at the time of autopsy. Tissue distribution studies showed a marked increase in concentration of the radionuclide in the injured as compared to the normal myocardium. Seventy-two Hours After Contusion: The angiogram showed numerous fine kinked or new vessels (Fig. 6) near the area of injury. These small new vessels were found morphologically in areas of granulation tissue as part of the process of repair. The radionuclide images remained positive with diminishing activity at this stage. One Week Post Contusion: The heart showed patchy areas of scarred myocardium mixed with normal myocardium. The coronary arteries returned to normal size but remained somewhat tortuous in the areas of injury (Fig. 7). Very few to no giant capillary-sinusoids or

September 1975

99mTC-sn-polyphosPhate: (NaH/0

4)n

n: 40-50

Tissue Distribution: Organ or Tissue

Ratio (CPM/gr tissue)

Normal heart L. V. Normal heart R. V. Blood Injured heart (1) InjU red hea rt 121 Normal rib Injured rib Injured pericardium Injured pericardium fat Injured lung Injured liver

1. 00 1. 54 2.16 9.46 14.02 8.29 14.81 4.07 1.79 4.19 7.63

Fig. 9. Summary of results obtained by imaging isolated specimens of tissue from two dogs. Note that the numbers shown are expressed as a ratio of activity with the normal myocardium being used as the reference.

small kinked neovascular structures could be found at this stage. The scintigraphic studies (Fig. 8) showed little or no cardiac activity, but high uptake could be seen in some ribs on the left, presumably representing healing fractures. DISCUSSION

Fig. 7. The angiogram one week after the injury shows only some increased tortuosity of vessels in the area of the contusion.

Fig. 8.

A review of the literature indicates that there has never been an in-depth experimental study involving the angiographic changes in cardiac contusion. The previously described findings outline our impression as to what the sequential morphologic changes are in myocardial contusion. In order to understand why the radionuclide image is positive, we are assisted by the findings of Bonte et al. (4) who studied the scan findings in experimental myocardial infarction in dogs. Ischemia, which results in myocardial cell death, is accompanied by cellular influx of calcium ions which localize within the mitochondria in the crystalline structure of hydroxyapatite. The 99 m Tc_

Sequential radionuclide images of the same dog show that the activity in the contused myocardium has almost disappeared in one week with activity remaining in the overlying injured ribs.

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Sn-polyphosphate, which normally labels hydroxyapatite for bone scanning, labels the hydroxyapatite in the injured myocardium as well. Tissue distribution studies of the radioactive tracer were performed in two of our dogs and showed an injured to normal myocardium ratio of 8:1 and 14:1, respectively (Fig. 9). The ratios between injured and normal muscle and bone did not show a comparable rise in the injured tissue. We further theorize that the tracer may localize within extravasated pools and/or giant capillary-sinusoidal vessels as demonstrated in postmortem angiography and pathological sections. Decreasing localization of the radiopharmaceutical in the heart is apparent as time goes on. There is also evidence that the extravasated pools and giant capillary-sinusoids diminish simultaneously with the decreased activity of the scan. ACKNOWLEDGMENTS:

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CORONARY FINDINGS IN CARDIAC CONTUSION

The authors wish to thank Dr. Frank

Nuclear Medicine

H. Cheng and Dr. Kenneth A. Bell for their assistance in this project.

REFERENCES 1. Doty DB, Anderson AE, Rose EF, et al: Cardiac trauma: clinical and experimental correlations of myocardial contusion. Ann Surg 180: 452-460, Oct 1974 2. Go RT, Chiu Cl, Doty DB, et al: Imaging of experimental myocardial contusion with Tc-99m-Sn-Polyphosphate (abst). J Nucl Mad 15: 494-495, Jun 1974 3. Mautz FR: Anatomical and physiological considerations in the development of a collateral circulation to the myocardium. Dis Chest 31: 265-285, Mar 1957 4. Bonte FJ, Parkey RW, Graham KD, et al: A new method for radionuclide imaging of myocardial infarcts. Radiology 110:473-474, Feb 1974 Department of Radiology University of Iowa Hospitals and Clinics Iowa City, Iowa 52242

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Coronary angiographic and scintigraphic findings in experimental cardiac contusion.

Clinical, angiographic, scintigraphic and pathologic observations in myocardial contusion were correlated. Radionuclide imaging of the injured heart w...
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