Cineradiography for determination of normal and abnormal function in mechanical heart valves

Cineradiography for Determination of Normal and Abnormal Function in Mechairical

Heart Valves Werner Vogel, MD, Hans Peter Stall, MD, Wolfgang Bay, MD,

Gerd Frijhlig, MD, and Hermann Schieffer, MD

To detemmine the diagnostic value of cineradiography of mechanical heart valves, 112 tine fluomscopic studies were perbnned in 76 pa tients with 95 valve prosmww (caged ball or disk valves, tiltimg disk and bileaflet valves). A patient group (n = 45) presenting with clinical or echocardiiphic findings suggestive of. valve+ related camplications was compamd withacom trolgroup(n=3l)withoutsuchsymptoRlaDisk- opening angles (mean + SD) for Medtronic Hall aortic valves were found to bs signiiickmtly smaller (62.8 f ll.1’) in patients than in contml suqects (73.9 + 1.6”; p 40.05). 7iie ingrowth or thrombus fommtion, or both, demonstrated in 3 patients on subsequent moperation, are con&k ered as the main cause of incomplete 01 asym met& disk opening. Opening and closing times did not dii signiily between patients and controlsubjects. Besides abnormal valve motion, structuraldefectssuchasstnltfractureor leamtescapecouldherapidlydetectedbyci~ eradio@aphy if xray projections according to the particular valve design were used. Together with qmntitative Doppler echomrdio&aphic and dini- cal data, thii method can help to &ve specific answersiftllequestiiistoeitherconfimor exclude imminent or acute valve matfunctii. Thus, modem cineradiiy is a himly valuable noninvasive diic tool far both rapid man agement of emergency cases and routine follow- up of patients with mechanical heart valves.

(Am J Cardiol lSS3;71:22H32)

From the Medizinische Universititsklinik und Poliklinik, Innere Medi- zin III (Kardiologie), Homburg/Saar, Germany. Manuscript received February 11, 1992. Revised manuscript received and accepted August 17, 1992.

Address for reprints: Werner Vogel, MD, Medizinische Universi- Gtsklinik, Innere Medizin III, D-6650 HomburgBaar, Germany.

F luoroscopy has been widely used for identifying artificial heart valves1,2 and detecting valve malfunction and valve-related complications, which

were relatively frequent in the early years of valve surgery.3-5 Meanwhile, patients with modem artificial valves are usually followed up by 2-dimensional and Doppler echocardiography. However, these techniques, although giving excellent insight into hemodynamics, do not allow a structural analysis of mechanical valves. Thus, they remain indirect methods where a mechanical problem is in question.

Although the visibility of mechanical valves with modem radiologic equipment has become excellent, sys- tematic cineradiographic studies have been reported only for the functional analysis of single valve types (e.g., BjSrk-ShileyC9 or St. Jude1o,11 valves), for monitoring fibrinolytic therapy in acute valve thrombosis,6,‘2 and for evaluating periprosthetic regurgitation.13 The aim of the present study was (1) to establish normal values for opening and closing times of different types of current mechanical valves in vivo, (2) to compare opening and closing angles of tilting disk valves with the manufac- turer’s specifications, and (3) to show abnormalities in clinically suspected or surgically proven malfunction as will be demonstrated in individual cases.

Patient population and valve types: A total of 112 cineradiographic studies were performed in 95 mechanical heart valve substitutes that had been implanted in the aortic (n = 47), mitral (n = 46), and tricuspid (n = 2) positions in 76 patients. Fifty-nine patients had un- dergone single-valve replacement (33 aortic, 26 mitral), and 17 double-valve replacement (aortic and mitral in 15, aortic and tricuspid in 2) 70 + 65 months (range 1 to 230) before the study. In 45 patients (patient group), we considered an indication for fluoroscopy because of clinical or Doppler echocardiographic14 tindings suggestive of valve-related complications (5 were emergency cases of pulmonary edema or cardiogenic shock, or both). Indications are listed in detail in Table I. In the remaining 31 subjects (control group) fluoroscopy was performed for different reasons: Older models of caged ball or tilting disk valves known to bear an increased risk of strut fracture or leaflet escape were screened for exclu- sion of early signs of such mechanical failure (e.g., Bjork-Shiley valves before the monostrut era,15-18 duromedics bileatlet valves19). Other subjects were examined in order to exclude valve thrombosis, e.g., if anticoagulation had been discontinued for noncardiac surgery. No control subject had clinical or Doppler echocardiographic signs of valve or cardiac dysfunction at the time of analysis.

CINERADIOGRAPHY IN MECHANICAL HEART VALVES 225

TABLE I Indications for Cineradiography (patient group)

Indication

Heart failure* Changed clicks/murmurs TIA/stroke, dizziness Hemolysis Anticoagulation, irregular

Doppler gradient hight Malfunction follow-upt

Infective endocarditis

No. of Pts.

10 7 7 7 5

4 3

2

%

22.2 15.6 15.6 15.6 11.1

8.9 6.6

4.4

Total 45 100.0

*Heart failure unexplamed by poor ventricular function or arrhythmias. or both. ?Gradient exceedine 30 m m Hg in aoriic valve and 4 m m Hg in mitral/tricuspid

valves. tMlnor mechanical dysfunction without clear indabon for reoperation. TIA = transient ischemic attack. I

TABLE II Distribution of Prosthetic Valves with Respect to

Type, Site, and Relation to Patient or Control Groups

Valve Aortic Mitral All

Type (pt./control) (pt./control) (pt./control)

Starr-Edwards 4 (2/2) 2 (l/l) 7* (413) Cooley-Cutter 1 Cl/-) - t-/-j 1 (l/-I BJBrk-Shiley 14 (11/3) 4 (2/2) 18 (13/5) Lillehei-Kaster 2 (l/l) - t-i-> 2 (l/Ii Medtronic-Hall 36 (19/17) 1 (-/I) 37 (19/18) St. Jude Medical 3 (l/2) 30 (20/ 10) 34* (22/12)

Duromedrcs 2 C-/2) 11 (l/10) 13 (l/12)

Total 62 (36/26) 48 (25/23) 112* (63/49)

*Include 2 tncusp!d valves in the patlent group.

r

FIWRE 1. Rzmge of amiocaudal skew (vedcal hivtcM@ androtaucn(~ewtal~efxraytubefcrthe identitication of pmJsc&m in valve cimradiiphy (see text). UO/RAO q left/right ant& oblique view.

ips Poly Diagnost C) with digital imaging (Philips DCI- S Release 2.3). This system allows the position of the roentgen tube to be varied within a wide range of cranial to caudal skew (horn -45 to +45”) and of right to left oblique rotation (from -120 to +120”), each projection

J being characterized by 2 (positive or negative) figures. For example, in a -31”/+42” projection the tube is tilt-

Numbers and types of investigated valves are listed ed to a 31” cranial and rotated to a 42” left anterior oblique position (Figure 1). All valves were assessed as follows:

in Table II. In all, 12 different models from 7 types of mechanical valves were examined. Most of the valves in the patient group could be matched with control valves of the same type.

MflHODS Fhroroscopy and cineradiography were performed in

the supine patient with a monoplane x-ray system (Phil-

1. A sag&al (O”/O”) projection was taken for the identification of the valve and its steric orientation in situ.

2. The tube was then moved to a position with x- rays parallel to the valve ring plane. This allowed one to directly determine the occluder’s excursions in caged

Skew [“I cranlal

-60

-30 - - .

X

O-

30.. -.y’:- / x = mitral valve . -

I - . =aortlc valve

60- x -

caudal

I I I I I 1 I

RAO -60 -30 0 30 60 LAO

Rotation [ “1

FIWRE 2. PmJeclion altglee ef pivot viewe. Note the wide diikrtion of coomlinates in individu~ valves. Mean values for all mea8lldlemRml(/cfg amnv) and aortic valves (shad mow) me shcwn. LAo/RAo = left/right ante&r cbliiue view.

226 THE AMERICAN JOURNAL OF CARDIOLOGY VOLUME 71 JANUARY 15.1993

CONTROLQROUP PATIENT GROUP lmarcl

360 - . .

320 - .

280 - .

240 - .

200 - T

I hortlo Mltrrl Aortlo Mitral

openlolorrd opmlolowd oprnlclor~d oprnlcloaed

FlGURE 3. Opening and closing times (in milliseconds) of diC ferent typea ef medmmiil valves. Whmnces between pa tients and conwl subjects me net SqniRcant.

valves. In tilting valves, however, a “pivot” view (tech- nically equivalent to the sectional elevation) with x-rays strictly parallel to the tilting axis had to be achieved in order to measure correctly opening and closing angles.

3. Additional projections were performed if any ir- regularities of disk motion were observed or a pivot view could not be obtained: a “disk” view with the beams parallel to the disk plane at full opening but perpendicular to the tilting axis. This view allows calculation of the opening angle with sufficient accuracy6 and checking for correct seating of the occluder on its support. Special views were added to examine the welding points of struts in Bjork-Shiley and caged valves.

4. The projection angles of each view were docu- mented, and video prints and short &refilm runs (3 to 6 heart cycles) were obtained for the subsequent functional analysis:

Valve motion was analyzed by measuring opening and closing angles from the pivot view and by evaluating the occluder’s opening and closing speed using the shutter speed of 50 frames/s as a time marker. For example, if opening started in frame 1 and was being completed in frame 3, opening time was calculated to be 60 ms (with the exact opening time ranging between 40 and 60 ms). Accordingly, closing time, systolic and diastolic

FlGURE I Nomml opening (loo, IeU) aad dosing zs@e (Woo) of a 29 mm St. Jude Me&calmRralvalveseenfromRspivot view.Forcompbte~sisofthiscasea pivot view of tlm supefinlpesed Me RallaorticvalveneedstobeobtMedbya furtherleftrotatiiamlcranialskewofths xray tube.

FlGURE 4. Normal opening (75”) and closing angle (0’) of a Madtronic-Rall aortic valve. Superimpossd pivot supports indicate that the pivot view is correctly installed.

intervals and heart cycle length were measured. Differ- ences between valve motion parameters of the patient and control group were statistically analyzed by use of the Mann-Whitney U test.

RESULTS Valve olientatii: In the group with 46 aortic tilt-

ing disk valves, a pivot view was not obtained in 4 patients (8.7%) for anatomic or technical reasons (invis- ible delrin disk of an early Bjork-Shiley model in 1 patient). In the mitral group, 10 of 36 valves (27.8%) could not be viewed exactly along the pivot axis. Fig- ure 2 shows the wide distribution of projection angles for the pivot views of tilting disk or bileaflet valves in the aortic and mitral position, respectively. The wide range is due to anatomic variations as well as the surgeon’s choice for valve orientation and forces the radio- grapher to find individual projections for the specific views of each valve.

Valve motio ving and dosing speed: Nor- mal disk or ball motion in different valve types was stud- ied in 31 subjects in the control group with 48 valves. Irrespective of the valve size and heart cycle length, opening time was completed within 60 ms in >80% of all aortic valves. Only 2 aortic valves (1 Starr-Edwards, 1 Medtronic-Hall) required 80 to 100 ms for full opening. Opening and closing times in the patient group did not differ significantly from those in control subjects, with mean values and ranges being slightly higher in


FIGURE 6. Rormal opening and closing of a Duromedics mitral valve.

both aortic and mitral valves (Figure 3). Mitral opening time in both groups rarely exceeded 80 ms (100 ms in 2 and 160 ms in 1 patient with a periprosthetic leak; all had bile&et valves without any mechanical malfimc- tion).

Complete closing required up to 360 ms in some of the bileaIlet mitral valves. This finding was infrequent and mostly due to an asymmetric closing in patients

80 -[“I p 0.05

0 -- .”

P .$;- f *J-

70 - . e n I T beev-- .-... ‘.--700

i 60-

i !50- i 1

)... : _.....- i’ -.600

I

. . 40- = =

cm- . = C I a-- .

0 . 8 i

10 -

.smmw-- .--““M. -0.. - b

Controls / Patients Controls / Patients

Medtr.-Hall Aortic Bji%k-Shiley

FIWRE 7. Opening and closing w of tilting drk valves. R/ackMmgktsandbttedMesmiakthespecifiedopening an@es of 75” in the Medbnic (Medtr.)+lall de valve, and ef 60 cr 70” in BJiwk9lriley valves, respectively. Note the WilkJJHBg0Of &nomtal~inthepatientgmup.

PlGllRE8.PiVOtdtliSkVkW ef M-1 acrtic valve

F: wRheonr&ntlyasymmetric cpening by cnly 50”. Patii lWtdIyncopely~apt~

age and sevefe eternal and genedesteepaeeie.Ne

: : ..- dmge at cimrmlio&aphy 1 ,‘.i and2yecrsiatqpatiat

ii ,;‘;,# remained 8symptomatic.

228 THE AMERICAN JOURNAL OF CARDIOLOGY VOLUME 71 JANUARY 15,1993

with atria1 fibrillation. In none of the cases was it asso- ciated with clinically significant mitral regurgitation.

Valve moGon+qemimg and closing angles To compare disk excursions with the manufacturers’ specifications, opening and closing angles were measured in all tilting disk and bileaflet valves in which a pivot projection had been achieved. Tilting disk valves close at O”, with the disk forming a parallel radioopaque line within the valve ring (Figure 4). The only exception is the Lillehei-Kaster valve which closes at 18” and opens to a maximum of 80”. The Medtronic-Hall valves open to 75” (Figure 4) or 70” for the aortic and mitral models, respectively. Bjork-Shiley disks open to 60 or 70” depending on the type. In St. Jude valves both leatlets form an angle of 120” (size 125 mm) or 130” (size 227 mm) when closed and 10” at full opening (Figure 5). Duromedics leaflets cover an angle of 38 and 28” for

FlGUR5 10. Reduced opening a@e (5W) of a Mdtronidlall acrtic valve in an asymptomatic patlent; Deppler #adient was 5OmmHg.Atfollowupafter4 ww clssing deficit (lw) WlthaortiCfWgU@t&iCll8d

*&y&zaq-- .-

tively a pnnus at tha inflow (larsese#mW~afresh tllMdUSlbt~OUtflOWSide

(small segment) wem detected and removed. FolhWup after 1 year again showed an opening zmgleof55”,withaDoppler gradient of 25 mm Rg.

the open mitral and aortic valves, respectively; these angles, however, are particularly difficult to assess because of the curved shape of the leatlet and their poor visibility in the closed position (Figure 6).

Statistical analysis revealed that opening angles of Medtronic-Hall aortic valves were significantly smaller in patients (62.8 k ll.l”, range 44 to 75”) than in control subjects (73.9 f 1.6”, range 71 to 76”). Opening angles >70” were found in only 5 cases in the patient group. These had been investigated for reasons not high- ly suggestive of mechanical failure, namely hemolysis, bleeding complication, unexplained syncope, and infective endocarditis (2 cases). In the remaining valves (70%), opening angles were 169”. In Bjork-Shiley valves, opening angles met the specified values of 60 or 70” with a deviation of 13” except the case described later. Closing (0’) was normal in all but 3 patients (1

FlGuRE 12. llmnobilization of ths caudd leafletofa2lmmDuromdcs - mitral valve 1 year after implantation by massive cakRic&on of the mitral ring (see text).


FloURE13.S~~ardsmodel84oomikalvalve4yearrapterimplantation.Strutfractureatthebgseri~andescapeaf a 12 mm fra@neM of the inner track were detected by cineradim (arrows). Explanted valve eves showed 2 broken welding points and marked cloth injury.

with a Bjork-Shiley and 2 with Medtronic-Hall aortic valves) with subsequently contirmed valve thrombosis (Figure 7). Opening and closing angles of all St. Jude Medical valves were again close (within 3”) to specified values (opening angles, 10 to 13”, closing angles, 120 to 122” or 130 to 133’).

A frequent observation in valves with reduced opening angles was a constant asymmetry of the disk at max-

FWJRE 15. CooleyCutter caged disk aOrtic valve 15 years afterimplaeMii,witheonealmovemeetofanopaHied biconical disk (caMed iofdtration?). Valve ex- was necesmy becauy of aortic regu@tation due to subvalvular pamus fonnaWn and iatemWeti %oCki~ of the disk.

FIGURE 14. staw-Edw~ model S400 mitral valve 16 yeas postoperatively at full opening. Intact welding points atthebaseringbutwidsned cage with 1 mm distance between upper shut and ball areseenwithvisiblaandaub ble (diastolic rattling) lateral play of the ball (ses text).

imal opening in the disk view (Figure 8). As a cause of this functional abnormality, tissue ingrowth or thrombus formation, or both, between the disk and the supporting pivot were suspected and could be confirmed in 3 patients who subsequently underwent reoperation. For example, in the case demonstrated in Figure 9, opening and closing angles of 44 and 29”, respectively, were caused by a tbrombus extending from 1 pivotal support to the major segment of the valve orifice with severe impairment of disk mobility, Similarly, an upstream pannus formation alongside the small segment of a Bjork- Shiley spherical disk valve with a fresh thrombus around the outlet strut were suggested from cineradiographic data (opening and closing angles 42 and 13”, opening and closing speed 240 and 160 ms, respectively) and continned during emergency surgery. Another case with a combination of pannus and fresh thrombus formation could be detected cineradiographically (Figure 10).

Incomplete valve opening could also be observed in patients with low cardiac output or arrhythmias. Disk- pivot contact in these cases, however, changed during several heart cycles and appeared to be normal in single (e.g., postextrasystolic) contractions (Figure 11).

In 1 case of mitral valve replacement with a 31 mm Duromedics valve, the inferoposterior lea&5 was stuck in severely calcified tissue in an almost closed position (Figure 12). This mass had aheady been present at the time of implantation, and had only partly been resected

230 THE AMERICAN JOURNAL OF CARDIOLOGY VOLUME 71 JANUARY 15, 1993

because of its infiltration into the posterior left ventricular wall. One year postoperatively, after a perfect recon- valescence, the patient again developed slight dyspnea on exertion. Doppler echocardiography revealed a small valve area of 1.6 cm* (measured by the pressure half- time method), and a relatively high gradient of 4 to 6 mm Hg with respect to the large valve size.14

Stnmtural defects: A strut fracture in a Starr-Ed- wards mitral valve (model 6400) 4 years after implantation could be detected by cineradiography. A 12 mm fragment of the inner metal track appeared to be broken and embolized into the left ventricle; the welding point was fractured at the base ring. The valve was removed because total break of the cage was imminent. The sit- uation then turned out to be even more serious because the excised valve showed that 2 of the 4 struts had already broken at the metal ring base (Figure 13). In another case of the same valve type, the aspect of the welding points appeared normal (Figure 14), but marked “lateral” excursions of the ball were suggestive of cage wear as will be discussed next.

One patient had an opaque layer in the “equatorial” plane of the biconical disk in an aortic Cooley-Cutter valve, which had to be exchanged after 1.5 years of un- eventful functioning because of aortic regurgitation and a subvalvular pannus formation with intermittent “cock- ing” of the disk, demonstrated intraoperatively. During cinefluoroscopy, disk movement itself appeared normal (Figure 15).

Two of our patients with cardiogenic shock presented with an outlet strut fracture of a Bjork-Shiley con- vexoconcave valve. Immediately after admission diagno- sis was cineradiographically coniirmed in both patients. The tirst case was a 37 year-old man who had had an uncomplicated aortic valve replacement 8 years before admission. He was seen in cardiogenic shock 4 hours after the onset of severe dyspnea, and died from low ventricular output despite immediate reoperation. The other patient was a 55 year-old man who had been followed 7 years after Bjork-Shiley mitral valve replacement without complications. He was referred to our hos- pital 7 hours after the onset of acute heart failure which had been refractory to usual therapy. Leaflet escape had not been suspected clinically because closing clicks were

clearly audible on auscultation. Changing loudness of the clicks had been attributed to the preexisting absolute arrhythmia. This misleading constellation could later be explained by a concomitant mild aortic stenosis that entrapped the large disk within the left ventricle and allowed it to be thrown on the metal valve ring every 2 to 3 systoles. The patient was protected from massive pulmonary edema for several hours by this “intermittent” mitral competence. Unfortunately, he also died in refractory left ventricular failure on the seventh day after emergency reoperation.

DISCUSSION From our data we can state that cineradiography pro-

vides clear information on structure and function of most mechanical heart valve prostheses. In roughly 85% of all tilting disk valves disk opening and closing angles can be directly measured and compared with the manu- facturer’s specifications, since a correct pivot view re- produces the designer’s sectional elevation. In the remaining valves, the opening angle can be obtained from the disk view by simple calculation. The excellent visibility of the disk in a profile view with modem x-ray systems makes the direct method applicable for virtual- ly all current disk valves. It is clearly superior to indirect method@ that are dependent on optimal imaging and cannot always rule out minimal closing deficits. Our lindings in the control group are consistent with pub- lished reports. 8~9~10~12 They suggest that a normal disk opening can be assumed if the measured opening angle meets the designated value within a small deviation of up to 3 to 4” depending on image quality, which may be poor in obese patients. As a consequence, an opening deficit of 25” should aid in further clarifying whether there is an anatomic (pannus, thrombus) or a functional reason (arrhythmia, low output, valve orientation). Ex- tensive calcification of the valve ring may be indicative of tissue ingrowth to the valve orifice that has been pre- viously shown to be a common problem after valve replacement,2O especially in patients with incorrect anticoagulation.4 According to the results of other investiga- tors,9,12 the opening or closing times of normal artificial valves rarely exceed 80 ms; the exception is the bileaflet valve in the mitral position, especially in patients with

FmuREl6.Bj6rk-6hiley 70" convexo-ancave mitral vdve 8 yeas after i~ntation. Note theslightaaymaryofthe a4ltletstNtmdt6skatfull openinglyearlate4rthe4situa tionwasidentidinUmodice (left) and disk (@itJ views


atrial fibrillation who may intermittently have a marked delay of one 1eatIet’s closing movement, usually without serious hemodynamic consequences. Severe and constant impairment of disk mobility in terms of low opening or closing speed is suggestive of acute thrombotic obstruction, but obviously it is not a sensitive sign. In our 3 patients with acute aortic valve thrombosis, both opening and closing times were abnormal in only 1; the others had prolonged opening or completely normal values (all within the reduced excursion angles).

Structural defects in caged valves were mostly related to ball variance or strut cloth injury, and rarely to a real damage to the cage itselF as in our patient (Fig- ure 13). It is not clear whether such a break is facilitat- ed by the long-term wear of the struts due to lateral excursions of the metal ball. Such “oscillations” perpendicular to the normal motion axis were clearly visi- ble and audible as a rattling diastolic noise on auscultation in the case presented in Figure 14.

Severe structural defects have been reported for many mechanical prostheses.19v22 The strut fracture problem of Bjork-Shiley valves continues to be a chal- lenge in the management of patients involved.15-18,23,24 Whether serial follow-up of such patients by cineradiography could identify patients at risk (e.g., by detection of slight strut deformation [Figure 161, or by identifying other possible predictors of fracture) needs to be es- tablished. In our institution, we therefore plan a screen- ing program of all pre-monostrut Bjork-Shiley valves with the described cineradiographic method.

The patient’s only risk with cineradiography is x-ray exposure with fluoroscopy times of 5 to 10 minutes (which can be reduced to about one third in reexamina- tions if projection angles are known) and cinefihn exposure times between 20 and 60 seconds. The small haz- ard seems greatly outweighed by the diagnostic benefit of this noninvasive method.

Interactions between biologic structures and a technical device over a lifetime are not predictable because they are dependent on several factors, namely the un- derlying disease, valve type and size. This has been em- phasized many years ago.s,23 Technical devices need precise survey, and this applies especially to artificial heart valves because they constantly interfere with liv- ing tissue. Advantage can be taken of modem technical equipment to get a closer look at this complex interrela- tion. Magnetic resonance imaging may be a promising technique for special questions, but is still of limited value for studying mechanical valves.25 Doppler echocardiography is a clear advance for hemodynamic follow-up after valve replacement. Cineradiography with its immediate and high-resolution documentation capabilities provides unique information unavailable from other techniques, especially if early postoperative data can be compared with those from later follow-up. Therefore,

this simple method should be routinely used for patients with artiftcial heart valves.

REFERENCES 1. Mebhnann DJ, Resnekov L. A guide to the radiographic identification of pms- thetic heart valves. Circulation 1978;57:613623. 2. Mehhnann DJ. A guide to the radiographic identification of prosthetic heat valves: an addendum. Circulation 1984;69:102-105. 3. Starr A, Gmnkemeier GL, Lambat LE, ‘I?tomas DR, Sugimura S, Lefrank EA. Aottic valve replacement: a ten-year follow-up of non-cloth-covered caged ball prostheses. Circulation 1977;56:II:B-133-11-139. 4. Smithwick W, Kouchoukos NT, Karp RP, Pacific0 AD, KiikIin JW. Late stene sis of Starr-E!dwards clotl~-covered prostheses. Ann Thorac Surg 1975;20:24%2.54. 1. Roberts WC. Choosing a substitute cardiac valve: type, size, surgeon. Am J Car- dial 1976;38:633-644. 6. Venkataraman K, Beer RF, Mathews NP, Carl JR, Han&n EC, Turner AF, Fiick IX Thmmbosis of BjGrk-Shil ey amtic valve prostheses. Report of 3 cases and a method of cineradiogmphic assessment of the opening angle. Radiology 1980;137:44-47. 7. Ishimam S, Fumawka K, T&ah&i M. Cineradiographic evaluation of the con- vexoxoncave Bji%k-Shiley prosthetic valve in mitral position. Stand .I Thoroc Car- diovasc Surg 1983;17:211-215. 8. Cousin AJ, Soto B. New cineradiogmphic methods for assessment of Bjork- Shi- ley valve integrity. AJR Am J Roentgenol 1986;147:1139-1144. S. Albrechtsson UG, Thulii LI, Olin CL. Ciieradiographic functional evaluation of the Bjiirk-Shiley monostrut prosthesis. A follow-up study of 46 consecutive patients. Scar&J Thorac Cardiovasc Surg 1987;21:91-95. 10. Castanda-Zuninga W, Nicoloff D, Jorgensen C, Nath PH, Zollikofa C, Amp&z K. In viva radiographic appearance of the St. Jude valve prosthesis. Radiology 1980;134:775-776. 11. Hartz RS, L&&em J, Kucich V, DeBoer A, O’Mam S, Meyers SN, Michae- lii LL. Comparative study of w&win versus antiplatelet therapy in patients with a St. Jude Medical valve in the aotiic position. J Thorac Cardiovasc Surg 1986; 92:684-690. 12. Cm LS, Weiss M, Bateman TM, Pfaff JM, DeRobertis M, Eigler N, Vas R, Matloff JM, Gray RJ. Fibrinolytic therapy of St. Jude valve thrombosis under guid- ance of digital cinefluoroscopy. J Am CON Cardiol 1985;5:124&1249. 13. Green CE, Glass-Royal M, Bream PR, Soto B, Elliott LP. Ciiefluoroscopic evaluation of periprosthetic cardiac valve regurgitation. Am J Roentgenoi 1988; 15 1:4%459. 14. Burckhardt D, Hoffmann A, Amann FW, Gridel E. Noninvasive assessment of pressure gradients across prosthetic heart valves by doppler ultrasound. In: DeBakey ME, ed. Advances in Cardiac Valves. London: Yorke Medical Books, 1983:199-205. 15. Liidblom D, Bi&k VO. Semb BKH. Mechanical failure of the Bi&k-Shilev valve. Incidence, cl&al presentation, and management. J Thorac Cardiovac Surg 198ti92z894-907. 16. bstermeyer I, Horstkotte D, Bennet J, Huysmans H, Liidblom D, Olii C, Semb G. The Bj&k-Shiley 70” convexo-concave prosthesis strut fixture problem (present state of information) Thorac Cardiovasc Surg 1987;35:71-77. 17. Hiiatzka LF, Kouchoukos NT, Gntnkemeier GL, Miller DC, Sadly HE, Wech- sler AS. Outlet shut fracture of the Bjiirk-Shiley 60” convexo-concave valve: current information and recommendations for patient care. J Am CON Cardiol 1988; 11: 113&1137. 18. Liidblom D, Rodriguez L, Bjb;rk VO. Mechanical failure of the Bjiirk-Shiley valve. Updated follow-up and considerations on prophylactic re~placement. J Tho- rot Cardiovasc Swg 1989;97:95-97. 19. Moritz A, Klepetko W, Khii-Brady G, Schreiner W, Pabiiger I, Bailer H, Lang I, WoIner E. Four year folIow-up of the Dummedics Edwards bile&t valve prostheses. J Cardiovasc Surg 1990;31:274282. 20. Yoganathan AP, Corcotan WH, Harrison EC, Carl JR. The Bji&k-Shiley aortic prosthesis: flow characteristics, thmmbus formation and tissue overgrowth. Cir- culation 1978;58:7&76. 21. Zumbro GL, Cundey PE, Fishback ME, Galloway RF. Shut fracture in DeBakey valve. Successful reoperation and valve replacement. J Thorac Cardiovasc Surg 1977;73:469-470. 22. Orsinelli DA, Becker RC, Cu&xd HF, Moran JM. Mechanical failure of a St. Jude Medical Prosthesis. Am J Cardiol 1991;67:!%%908. 23. Taylor K. Acute failure of atificial heart valves. The risk is small. Br Med J 1988;297:996-997. 24. Treasure T. Management of patients with Bjcrk-Shiley prosthetic valves. Br Heart J 1991;66:333-334. 21. Randall PA, Kohmann W, Scalzeti EM, Szeverenyi NM, Panicek DM. Mag- netic resonance imaging of prosthetic cardiac valves in vitro and in viva Am J Car- dial 1988;62:97>976.

232 THE AMERICAN JOURNAL OF CARDIOLOGY VOLUME 71 JANUARY 15,1993

Cineradiography for determination of normal and abnormal function in mechanical heart valves

Documents

Transcript of Cineradiography for determination of normal and abnormal function in mechanical heart valves