Fetal monitoring during maternal cardiac surgery with

cardiopulmonary bypass

K.S. Koh, mb, bs; R.M. Friesen, md; R. A. Livingstone, mb,

Summary: Fetal cardiac activity was monitored with an external ultrasound transducer in two patients with clinical class III heart disease due to severe mitral stenosis complicated by pulmonary hypertension, undergoing

open heart surgery with cardiopulmonary bypass in the 2nd trimester of pregnancy. Fetal distress was detected in one patient who had mitral valvuloplasty, and was corrected by increasing the rate of blood flow. the other patient had a mitral valve replacement but no fetal distress was noted. The postoperative course of both mothers and fetuses was

uneventful. Resume: Surveillance du f6tus chez deux femmes durant I'opiration a coeur ouvert avec coeur-poumon artificiel Deux femmes enceintes ont subi, durant le 2e trimestre de leur grossesse, une intervention a coeur ouvert avec coeur-poumon artificiel, pour une cardiopathie de classe clinique III causee par une stenose mitrale severe

compliquee d'hypertension pulmonaire. L'activite cardiaque du fetus a ete surveillee durant I'operation maternelle au moyen d'un transducteur externe a ultrason. Chez une des meres, qui a subi une valvuloplastie mitrale, on decela la souffrance fetal, qui fut corrigee par une augmentation de la vitesse de la circulation sanguine. Chez l'autre malade on pratiquait le remplacement de la valvule mitrale mais on ne decouvrit aucun signe de souffrance fetale. L'evolution postop6ratoire, tant chez les meres que les fetus, se deroula sans aucun incident.

The earliest reports of cardiac surgery

frcs[c]; L.J. Peddle, md, frcs[c] surgery valvuloplasty. Extracorporeal

b sc,

circula¬ several reports of open heart with the use of extracorporeal circula¬ tion utilized the Olson pump and the tion have appeared. Bentley oxygenator; perfusate type was Zitnik and colleagues5 in 1969 col¬ Normosol R. Flow rates were 60 to 80 lected a total of 20 cases of open heart ml/kg depending on venous return. Both fetuses were monitored by the surgery during pregnancy through a re¬ view of the literature and personal Hewlett-Packard fetal monitoring unit, communications. In this series there the external ultrasound transducer was only one maternal death (overall being placed over the maternal abdo¬ mortality, 5%). The data suggest that men where the fetal heart was heard pregnancy per se does not increase the most clearly. The ultrasound transducer maternal risk of heart surgery requiring was fixed firmly to the skin by strips extracorporeal circulation. There were of adhesive. The fetal heart acivity was recorded at a writer speed of 2 cm/ seven fetal deaths (overall mortality, 33%). That series did not show any min. correlation of pump type, perfusate Case 1 type or perfusion time with either ma¬ A 27-year-old woman, gravida II, para ternal or fetal mortality. was admitted to hospital on Oct. 14, 1, in heart The role of open surgery 1973 at 20 weeks' gestation with severe the production of congenital malforma¬ mitral stenosis complicated by pulmonary tions or the induction of abortion re¬ hypertension. Her estimated date of conmains uncertain. Factors potentially finement was in early March 1974. She had no history of a definite episode dangerous to the fetus that are inherent in cardiopulmonary bypass should be of rheumatic fever. Exertional dyspnea considered. Perfusion of the pelvis dur¬ had first been noted in 1967. This became 1971 when she consulted a ing bypass is not normally pulsatile; worse up toat which time a cardiac mur¬ perhaps this departure from normal is physician, mur was discovered. She had been on flow If the uterine blood important. antibiotics since that time. becomes marginal as a result of lack of prophylactic her previous pregnancy she had During of uterine artepulsatile flow, opening noted slight orthopnea, exertional dyspnea riovenous shunts or uterine hypertonia and ankle edema. Labour had been un¬ during bypass, critical fetal hypoxia eventful and in May 1972 she delivered might occur. The possibility that par- a male infant (weight, 3 kg) spontaneously ticulate or bubble emboli or sludging at term. Her symptoms were alleviated of blood might interfere with placental post partum. On Sept. 23, 1973 she was admitted to circulation during bypass awaits further a rural hospital with hemoptysis. She was investigation. It is likewise possible that treated conservatively with furosemide cannulation of the inferior vena cava and of but had further

digoxin episodes during cardiopulmonary bypass might hemoptysis associated with increasing partially obstruct this vessel, producing dyspnea. On Sept. 26 she was transferred subtle placental changes and secondary to a Winnipeg hospital for further man¬ fetal abnormalities. agement. Clinical examination and special With these thoughts in mind, the ac¬ investigation revealed severe mitral ste¬ tivity of the fetal heart was monitored nosis with pulmonary hypertension. Sur¬ desirable. during maternal cardiac surgery with geryShewaswasconsidered transferred to St. Boniface extracorporeal circulation in two pa¬ General Hospital, where her general con¬

performed during pregnancy appeared tients to detect fetal distress and, if dition was satisfactory: she was in no in 1952 when Brock,1 Cooley and any occurred, to determine whether and no pallor or cyanosis was Chapman,2 Logan and Turner3 and simple measures could be instituted to distress, noted. Her temperature was 37.1°C; pulse Mason4 reported on a total of 11 pa¬ correct fetal hypoxia. rate, 76 beats/min and regular, and pulse tients who underwent closed mitral volume good; blood pressure, 110/70 mm Patients and methods commissurotomy during pregnancy. Hg; and respiratory rate, 28/min. Her There was one maternal death and one Two patients with class III heart jugular venous pressure was not elevated. premature delivery. Since then reports disease (New York Heart Association The lungs were clear. The apex beat was of mitral commissurotomy in preg¬ functional classification) due to severe at the 5th left intercostal space and midnancy have increased in number, and mitral stenosis complicated by pul¬ clavicular line. There was a loud first heart sound and a grade 4/6 diastolic monary hypertension in the 2nd tri¬ rumble with presystolic accentuation at of mester From the department of obstetrics and pregnancy underwent open the apex. The fundus of the uterus was gynecology, St. Boniface General Hospital and heart surgery with cardiopulmonary by¬ at the umbilical level, consistent with 20 the University of Manitoba, Winnipeg One patient had a mitral valve weeks' gestation. Fetal heart sounds were pass. Reprint requests to: Dr. K.S. Koh, 560-60 Pearl replacement; the other had mitral heard with Doptone; the heart rate was St., Winnipeg, Man. R3E 1X2 1102 CMA JOURNAL/MAY 3, 1975/VOL. 112

142 beats/min. There




with its subvalvular components created

a subvalvular stenosis that could not be splenomegaly or peripheral edema. The relevant investigations included the relieved by the usual closed procedure, with the added risk of a false splitting following: 1. Chest radiography, which showed being a definite possibility. The activity of the fetal heart was evidence of pulmonary venous hyperten¬ monitored preoperatively with external sion and early congestive heart failure. 2. Electrocardiography (ECG), which cardiotachometry; the baseline fetal heart showed right axis deviation, incomplete rate (FHR) was 150 beats/min (Fig. 1). The patient underwent surgery on Oct. right bundle branch block and left atrial 29. The activity of the fetal heart was abnormality. 3. Echocardiography, which demon¬ monitored with the ultrasound transducer strated severe mitral valve disease. placed over the left side of the fundus 4. Pulmonary function tests, which re¬ approximately 5 cm from the umbilicus. vealed slight inspiratory and expiratory Total cardiopulmonary bypass was in¬ stituted and the body temperature was obstruction. 5. Combined right and left heart cathe¬ reduced to 31.5°C. The commissures and terization and angiocardiography, which underlying fused papillary muscles initially confirmed severe mitral stenosis and pul¬ were incised directly but this resulted in excessive regurgitation. Therefore, the monary hypertension. Although closed mitral commissurotomy mitral valve was replaced with a no. 32 was considered, the thickening and ex¬ Braunwald-Cutter valve. treme shortening and fusion of the valve The baseline FHR during general anes¬ thesia was between 135 and 145 beats/ min (Fig. 2) and remained the same until the cardiopulmonary bypass was begun, at which time the tracing was lost from :Pii«iiliiiL.. fliiiiciiis the monitor. A tracing at 120 beats/min liiiisfflii! was obtained for only 3 minutes during mmmm the period of extracorporeal circulation 9,mmmmmmm _..,.._._.,.....jtH r MKmmmmm._... 3). Towards the end of the period mmmmmummm'x mwrnmim m^t (Fig. of extracorporeal circulation the fetal im\:mmm,mmmmjm^ m MmmmmM^ m m* heart sounds were audible from the ultra¬ ~iwmm$m*mm&!m mtmammm tmm sound amplifier and the rate was 110 pr&& beats/min. When cardiopulmonary bypass was discontinued fetal heart activity was

mmmm mmmtwmmm wm wmmmm wgmmwmmmm immmmmm

Preoperative fetal heart (FHR) pattern; baseline FHR, beats/min.

detected on the monitor again; the base¬ line FHR was between 135 and 145 beats/min. The extracorporeal circulation time was 70 minutes. Blood gas values

FIG. 1.Case 1. rate


shown in Table I. The loss of the tracing from the mon¬ itor during cardiopulmonary bypass may have been due to the positioning of the ultrasound transducer directly over the aorta, where the high rate of blood flow from the pump interfered with the detec¬ tion of fetal heart sounds. The postoperative course of both mother and fetus was uneventful. Digoxin and sodium warfarin were administered to the mother; the prothrombin time was maintained at 20 to 25%. Postoperatively the baseline FHR was approximately 155 are

beats/min (Fig. 4).

The remainder of the patient's antenatal course was uneventful. She went into spontaneous labour at 39 weeks' ges¬ tation and delivered on Feb. 28, 1974 a

healthy 2.9-kg female baby with

score ouse.

of 9 at 1 minute, assisted




Apgar vent-

Case 2 A 20-year-old

primigravida was ad¬ mitted to hospital at 22 weeks' gestation on Oct. 19, 1973 for cardiac surgery. She had severe mitral stenosis complicated by pulmonary hypertension. She had been hospitalized in 1971 and 1972 with fever and malaise, at which time a heart mur¬ mur was discovered. Her estimated date of confinement was Mar. 1, 1974. She stated that she had felt well until 2 months before (at 14 weeks' gestation), when orthopnea, exer¬ tional dyspnea and ankle edema developed. She was 132 cm tall and weighed 37 kg. Her blood pressure was 100/65 mm Hg. Her pulse rate was 90 beats/min and regular and the pulse volume was good.

Case 1

FIG. 4.Case 1.


Table I.Random values of arterial blood gases during extracorporeal circulation


pattern; baseline FHR, 155 beats/min.


Extracorporeal circulation time (min) Temperature (°C) PH Pco2 (mm Hg) (mm Hg) Po2 Bicarbonate (meq/l) Base excess (meq/l)


Case 2 27

31.5 34 7.25 7.26 7.18 47 43 60 170 187 289 19.5 18.5 21 -2 -8 -8

FIG. 2.Case 1. FHR pattern with under general anesthesia.


FIG. 3.Case 1. FHR of 120 beats/min during extracorporeal circulation.

FIG. 5.Case 2.

Slowing of

extracorporeal circulation. JOURNAL/MAY 3, 1975/VOL. 112 1103

FHR at commencement of CMA

The jugular venous pressure was elevated to 3 cm H20. She was dyspneic on minimal exertion but the lung fields were clear on auscultation. The apex beat was palpable in the 5th left intercostal space and midclavicular line. There was a loud first heart sound and a grade 4/6 middiastolic murmur with presystolic accentuation at the apex. The uterine fundus was approximately 2 cm above the umbilicus, consistent with 22 weeks' gestation. Fetal heart sounds were normal; the FHR was 148 beats! mm and regular. There was moderate peripheral edema. Special cardiovascular investigations included the following: 1. EGG, which revealed marked T-wave inversion in V1 to V4. 2. Chest radiography, which showed the heart to be somewhat enlarged; there was a typical mitral configuration with enlargement of the right ventricle and left atrium, and prominence of the left atrial appendage. There was some degree of pulmonary congestion. 3. Echocardiography, which demonstrated a severe stenotic, moderately pliable mitral valve. 4. Pulmonary function tests, which revealed slight inspiratory and expiratory obstruction. 5. Cardiac catheterization, which con-




FIG. 6-Case 2. Increase in FHR with increase in blood flow during extracorporeal circulation.


firmed rigid mitral valve leaflets with thickened chordae tendineae and associated severe pulmonary hypertension. On the basis of the preoperative angiocardiographic study the valve was judged to be moderately thickened and its movement restricted, features that made it unsuitable for a closed type of commissurotomy. Preoperatively the FHR was normal, at 140 to 145 beats/mm. Open heart mitral valvuloplasty was pefformed on Nov. 2, 1973. The external ultrasound transducer was placed on the right lower quadrant of the abdomen, approximately 8 cm from the umbilicus. The baseline FHR was between 130 and 135 beats/mm. However, when extracorporeal circulation was instituted the FHR slowed to 60 beats! mm and remained there (Fig. 5). As in case 1 the tracing was lost but the fetal heart sounds could be heard from the ultrasound amplifier and counted. In an attempt to improve placental perfusion the blood flow rate was increased from 3100 to 3600 ml! mm. The FHR audibly increased to 80 and then 120 beats/mm (Fig. 6). When the extracorporeal circulation was discontinued the FHR accelerated momentarily to 170 beats/mm (Fig. 7) and then remained at 130 beats/mm. The extracorporeal circulation time was 27 minutes. Blood gas values are shown in Table I. The postoperative course of both mother and fetus was relatively uneventful. The mother continued to show moderate pulmonary congestion in the immediate postoperative period, which was well controlled with occasional administration of furosemide. Digoxin and low-salt diet were prescribed. The FHR postoperatively was 130 beats! mm. The remainder of her antenatal course was uneventful. She went into spontaneous labour at 38 weeks' gestation and delivered on Feb. 16, 1974 a healthy 2.7-kg male baby with an Apgar score of 6 at 1 minute, assisted by ventouse.

Discussion In the second patient undergoing open heart surgery fetal bradycardia was detected with ultrasound cardiotachometry. The bradycardia was corrected by an increase in blood flow from the pump. Short perfusion times

at high flow rates would presumably provide maximal placental perfusion. It is conceivable that other conservative measures employed to correct fetal distress during labour may also be attempted during open heart surgery, for example: (a) increasing the oxygen saturation of the blood; (b) administering sodium bicarbonate to correct acidosis; or (c) infusing glucose to replenish depleted fetal glycogen stores during fetal hypoxia and to correct fetal acidosis originating because of maternal acidOs's. Technical aspects such as pump type, perfusate type or perfusion time as they relate to obstetric patients also warrant further investigation. If fetal distress can be successfully treated or minimized in open heart surgery during pregnancy, the fetal mortality and morbidity associated with the operation will diminish considerably. The technical problems of accurately recording the FHR during cardiopulmonary bypass will have to be overcome so that changes in the FHR pattern suggestive of fetal distress can be visualized and corrected promptly. Conclusion Open heart surgery is now more frequently used to treat severely disabled pregnant patients with surgically correctable cardiac lesions. The potential and actual fetal hazards appear multiple, but as yet their precise mechanisms of action remain undetermined. It may be possible to reduce the fetal mortality and morbidity by monitoring the fetus during maternal open heart surgery and instituting simple measures to correct fetal distress when it occurs. Fetal monitoring should be more widely used during maternal surgery, especially in major chest operations in which oxygenation of maternal blood, and hence oxygen supply to the fetus, may be jeopardized. We wish to acknowledge the cooperation of Dr. Morley Cohen and the cardiovascular and thoracic service of St. Boniface General Hospital in the surgical management of these patients. References 1. BROCK RC: Valvotomy in pregnancy. Proc R Soc Med 45: 538, 1952 2. COOLEY DA, CHAPMAN DW: Mitral commissurotomy







FIG. 7-Case 2. Increase in FHR after discontinuation of extracorporeal circulation 1104 CMA JOURNAL/MAY 3, 1975/VOL. 112





1113, 1952 3. LOGAN A, TURNER RWD: Mitral valvulotomy in pregnancy. Lancet 1: 1286, 1952 4. MASON J: in discussion of STABLER FE, SZELELY PJ: Cardiac disease in pregnancy. Obstet Gynecol Br Emp 59: 569, 1952 s. zITNIK RS, BRANDENBURG RO, SHELDON R, Ct al: Pregnancy and open-heart surgery. Circulation 39 (suppi): 257, 1969 6. McINTOsH R, MEaRS¶-r KK, RscHARDs MR, et Incidence of congenital malformations:

study of 5964 pregnancies. Pediatrics 14: 505, 1954 7. MEFFERT WG, STANSEL HG: Open heart surgery during pregnancy. Am I Obstet Gynecol 102: 1116, 1968

Fetal monitoring during maternal cardiac surgery with cardiopulmonary bypass.

Fetal cardiac activity was monitored with an external ultrasound transducer in two patients with clinical class III heart disease due to severe mitral...
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